Navigating EU ATMP Batch Release: A Comparative Guide to Requirements Across Member States

Abstract

This article provides a comprehensive comparison of batch release requirements for Advanced Therapy Medicinal Products (ATMPs) across European Union countries. Tailored for researchers, scientists, and drug development professionals, it explores the foundational EU regulatory framework, details methodological approaches for compliance, addresses common challenges in decentralized manufacturing and supply chain logistics, and validates strategies through comparative analysis of national competent authority expectations. The content synthesizes current guidelines, including the 2017 ATMP-specific GMP rules and the latest 2025 proposed revisions, to offer a practical roadmap for successful batch release in the complex EU regulatory landscape.

Understanding the EU Regulatory Framework for ATMP Batch Release

Comparison of Batch Release Requirements for ATMPs in EU Countries

Advanced Therapy Medicinal Products (ATMPs) represent a category of innovative biological products in the European Union (EU), governed by a sophisticated regulatory framework. The legal foundation for these therapies is established by Directive 2001/83/EC, ATMP Regulation (EC) No 1394/2007, and associated delegated acts, which collectively define the requirements for marketing authorization, manufacturing, and batch release [1]. ATMPs are classified into four primary categories: gene therapy medicinal products (GTMP), somatic cell therapy medicinal products (SCTMP), tissue-engineered products (TEP), and combined ATMPs (cATMP) that incorporate one or more medical devices as integral components [1]. A critical differentiator within this framework is the distinction between ATMPs, regulated as medicinal products, and other human cell and tissue products that may fall under different legal frameworks such as blood or transplant laws, where cells are not considered medicinal products and cannot be commercialized on an industrial scale for ethical and legal reasons [1].

The regulatory oversight for ATMPs involves a dual-layer system where marketing authorization follows a centralized procedure evaluated by the European Medicines Agency's (EMA) Committee for Advanced Therapies (CAT) and Committee for Medicinal Products for Human Use (CHMP), ensuring a single evaluation applicable across all EU member states [1]. However, manufacturing authorizations and GMP compliance remain under the supervision of national competent authorities of individual member states, creating a complex interface between centralized and national regulatory responsibilities [2]. This structure establishes the foundation for understanding variations in batch release implementation across EU countries while operating within a harmonized regulatory framework.

EU Batch Release Requirements: Centralized Framework with National Implementation

The EU batch release system for ATMPs functions through a decentralized implementation of a centrally-defined framework. While Directive 2001/83/EC and Regulation (EC) No 1394/2007 establish the overarching legal requirements, the practical application of batch release occurs at the national level through member states' competent authorities [2]. The manufacturing or import of ATMPs within the EU requires a manufacturing authorization from the national competent authority where these activities occur, and all ATMPs must be produced according to EU Good Manufacturing Practice (GMP) standards [2].

The batch release process involves multiple stakeholders with distinct responsibilities. The manufacturer or manufacturing authorization holder bears primary responsibility for ensuring each batch complies with GMP and marketing authorization requirements. National competent authorities conduct regular inspections of manufacturing sites to verify compliance and perform official batch release through their control laboratories, which may test samples to verify declared composition [2]. The EMA maintains the EudraGMDP database, which consolidates GMP certificates and non-compliance statements issued after inspections across member states, facilitating information exchange between regulatory bodies [2].

Table 1: Key Stakeholders in ATMP Batch Release Process

Stakeholder	Primary Responsibility	Regulatory Level
EMA/CAT	Scientific evaluation of marketing applications; guidelines coordination	EU Centralized
National Competent Authorities	Manufacturing authorizations; GMP inspections; official batch release	Member State National
Manufacturing Authorization Holder	GMP compliance; quality control; batch documentation	Company Level
Marketing Authorization Holder	Product registration; pharmacovigilance; compliance with authorization terms	Company Level

A significant challenge in this system emerges from the tension between centralized authorization and decentralized manufacturing oversight. Although ATMPs receive marketing authorization through the centralized procedure, manufacturing compliance remains a national competency, potentially leading to variations in implementation across member states [2]. The system operates on mutual recognition and harmonization efforts coordinated through the EMA's Good Manufacturing and Distribution Practice Inspectors Working Group (GMP/GDP IWG), which works to establish common interpretations of GMP requirements across the EU [2].

Comparative Analysis of National Implementation Approaches

Standard Batch Release Model

The standard batch release model represents the conventional approach to ATMP batch control across EU member states. In this model, product release occurs at the manufacturing facility before distribution to clinical sites [3]. The manufacturing authorization holder conducts comprehensive quality control testing, including identity, purity, potency, and safety assessments, with the qualified person (QP) certifying that each batch meets all specifications outlined in the marketing authorization [2]. National competent authorities may perform official control authority batch release for certain biological products, testing samples in their control laboratories to verify compliance with the declared composition [2].

This model faces particular challenges with ATMPs characterized by short shelf-lives and personalized manufacturing. The time required for comprehensive quality control testing, including sterility tests, may approach or exceed the product's viable duration, creating significant logistical constraints [3]. Additionally, the personalized nature of many ATMPs, particularly autologous therapies, means each patient's product constitutes an individual batch, dramatically increasing the batch release workload compared to conventional medicines manufactured at scale [3].

Emerging Approaches: Modular and Point-of-Care Manufacturing

The United Kingdom's Medicines and Healthcare products Regulatory Agency (MHRA) has introduced innovative regulatory approaches to address challenges in ATMP batch release through The Human Medicines (Amendment) (Modular Manufacture and Point of Care) Regulations 2025 [3]. This legislation establishes two novel pathways: modular manufacturing (MM) and point-of-care (POC) manufacturing, collectively termed "decentralized manufacturing" [3].

The modular manufacturing model involves manufacturing activities performed away from the primary manufacturing site but still within controlled environments, potentially including hospital laboratories or relocatable modular units [3]. Under this framework, product release occurs at the centralized "control site" that holds the manufacturer's license (MM), while satellite "modular units" follow detailed instructions in a Master File (MF) [3]. Similarly, the point-of-care model applies when manufacturing must occur at or near the patient location due to method of manufacture, shelf life, constituents, or administration route [3]. The manufacturer's license (POC) holder creates the MF and supervises secondary sites, with product release again occurring at the main manufacturing site rather than at the bedside [3].

Table 2: Comparison of ATMP Batch Release Models

Feature	Standard Model	Modular Manufacturing	Point-of-Care Manufacturing
Release Location	Manufacturing facility	Centralized control site	Centralized control site
Regulatory Framework	Directive 2001/83/EC	Manufacturer's license (MM) with Master File	Manufacturer's license (POC) with Master File
Batch Definition	Conventional batch size	Personalized or small batches	Patient-specific batches
Shelf Life Considerations	Suitable for stable products	Accommodates shorter shelf lives	Designed for very short shelf lives
Applicability	Traditional biologics	Distributed manufacturing	Bedside manufacturing

These innovative models represent a significant shift from the conventional approach by decoupling physical manufacturing activities from regulatory responsibility. The license holder maintains overall responsibility for quality assurance and batch release while delegating specific manufacturing activities to satellite sites operating under precisely defined protocols [3]. This approach potentially addresses the critical challenge of ATMPs with extremely short shelf lives by moving certain manufacturing steps closer to patients while maintaining centralized quality control and batch release.

Experimental Approaches for Batch Comparability

Comparability Protocols and Methodologies

Demonstrating comparability following manufacturing changes represents a critical component of ATMP development and quality control. The comparability exercise aims to provide analytical evidence that a product maintains highly similar quality attributes before and after manufacturing process changes, with no adverse impact on safety or efficacy [4]. According to ICH Q5E guidelines, this exercise requires careful planning with predefined acceptance criteria finalized before testing post-change batches [4]. The foundation of comparability assessment lies in comprehensive analytical characterization comparing critical quality attributes (CQAs) between pre-change and post-change products.

The typical comparability protocol follows a structured approach: (1) compiling comprehensive product knowledge including lists of product quality attributes (PQAs); (2) describing process changes and their potential impact on PQAs; (3) selecting appropriate analytical methods to detect potential changes; (4) defining acceptance criteria based on historical data; and (5) conducting side-by-side testing of pre-change and post-change materials [4]. The European Medicines Agency provides specific guidelines on the non-clinical and clinical requirements for comparability exercises when manufacturing process changes are made [5]. This methodology ensures that manufacturing changes can be implemented without compromising product quality or necessitating additional clinical studies when analytical comparability is satisfactorily demonstrated.

Analytical Methods and Quality Attribute Assessment

The analytical toolbox for ATMP comparability includes orthogonal methods capable of detecting subtle differences in complex biological products. For critical quality attributes such as higher-order structure, glycosylation patterns, and biological activity, multiple complementary techniques are typically employed [4]. Electrophoretic methods including capillary electrophoresis and capillary isoelectric focusing (cIEF) are generally preferred over traditional gel electrophoresis due to their superior quantitative capabilities [4]. The selection of analytical methods should be based on their ability to detect potential changes resulting from specific manufacturing modifications, with priority given to methods with established historical data for meaningful comparison.

The experimental workflow for comparability assessment begins with identifying which quality attributes might be affected by specific manufacturing changes through a risk assessment exercise [4]. This is followed by determining the most appropriate process intermediate for analysis, considering both the likelihood of detecting changes and analytical method sensitivity [4]. While theoretical considerations might suggest testing immediately downstream of the process modification, practical constraints often necessitate testing at the drug substance stage where sensitivity requirements can be better met and the impact of the entire purification process can be assessed [4].

The Scientist's Toolkit: Essential Reagents and Materials

Table 3: Key Research Reagent Solutions for ATMP Batch Release Testing

Reagent/Material	Function in Experimental Protocols	Application Context
Reference Standards	Serve as benchmarks for comparing pre-change and post-change product quality attributes	Comparability studies, method qualification, potency assays
Characterized Cell Banks	Provide consistent cellular starting materials for manufacturing and analytical development	Cell-based potency assays, product characterization
Quality Control Reagents	Enable detection of product identity, purity, potency, and safety parameters	Batch release testing, in-process controls, stability studies
Method Suitability Panels	Verify analytical method performance for intended quality attributes	Method validation, transfer, and qualification
Process-Related Impurity Standards	Facilitate detection and quantification of manufacturing process residuals	Safety testing, clearance validation studies

The comparison of batch release requirements for ATMPs across EU countries reveals a complex regulatory landscape characterized by a centralized marketing authorization system coupled with decentralized implementation at national levels. While Directive 2001/83/EC and ATMP Regulation (EC) No 1394/2007 establish harmonized legal requirements across the EU, practical application through national competent authorities introduces potential variations in implementation [1] [2]. The recent introduction of innovative regulatory pathways for modular and point-of-care manufacturing by the UK MHRA represents a significant evolution in addressing the unique challenges posed by ATMPs, particularly those with short shelf-lives and personalized manufacturing approaches [3].

The future direction of ATMP batch release is likely to involve greater harmonization of decentralized manufacturing models across EU member states, potentially informed by the UK's pioneering framework. Additionally, ongoing revisions to GMP guidelines specific to ATMPs, including alignment with revised Annex 1 and integration of ICH Q9 and Q10 principles, promise to further refine quality requirements [6]. For researchers and drug development professionals, understanding these evolving regulatory landscapes is essential for navigating the complex pathway from ATMP development to commercial approval and patient access across European markets.

The regulatory framework for Advanced Therapy Medicinal Products (ATMPs) in the European Union is a complex, multi-tiered system designed to ensure the safety, quality, and efficacy of these innovative therapies. Effective batch release of ATMPs—a critical step in bringing these treatments to patients—requires precise coordination between three key regulatory actors operating at different levels of oversight. Understanding the distinct yet interconnected responsibilities of the European Medicines Agency (EMA), National Competent Authorities (NCAs), and the Qualified Person (QP) is fundamental for researchers, scientists, and drug development professionals navigating the EU regulatory landscape. This guide objectively compares their roles, responsibilities, and interactions based on current EU legislation and regulatory guidelines.

Comparative Analysis of Key Regulatory Actors

The table below provides a structured comparison of the three primary actors involved in the oversight and release of ATMP batches in the EU.

Table 1: Key Actors and Responsibilities in ATMP Batch Release

Actor	Level of Operation	Core Responsibilities in ATMP Context	Legal Basis
European Medicines Agency (EMA) [7] [8]	EU-Level	- Scientific assessment of ATMPs for market authorization (centralized procedure) [7].- Provides scientific recommendations on ATMP classification via the Committee for Advanced Therapies (CAT) [7].- Coordinates GMP activities and maintains inspection-related procedures across Member States [2] [9].	Regulation (EC) No 726/2004 [7]
National Competent Authorities (NCAs) [2] [9]	Member State-Level	- Issue manufacturing and import authorizations for ATMPs within their territory [2] [9].- Conduct regular, repeated on-site GMP inspections of manufacturing sites [2] [9].- Officially release batches of biological medicinal products, including ATMPs, within their jurisdiction [2] [9].	Directive 2001/83/EC [7]
Qualified Person (QP) [10]	Manufacturing Site-Level	- Certifies that each batch of a medicinal product has been manufactured and checked in compliance with EU law, the marketing authorization, and GMP [10].- Personally responsible for batch certification before a product is released to the market [10].- Relies on and ensures the Pharmaceutical Quality System is effective [10].	Directive 2001/83/EC (Annex 16 of EU GMP Guide) [10]

Interaction Workflow in ATMP Batch Release

The following diagram illustrates the logical relationship and sequence of interactions between the QP, the National Competent Authority, and the EMA during the ATMP batch release process.

Diagram 1: ATMP Batch Release Workflow and Actor Interactions

This workflow shows that the QP operates at the manufacturer level, the NCA operates at the member state level with legal authority for GMP inspections and official batch release, while the EMA provides overarching coordination and harmonization at the EU level.

Experimental Protocols for Regulatory Compliance

For researchers, demonstrating compliance with regulatory standards is an integral part of ATMP development. The following methodologies are critical for generating the data required by the QP and NCAs.

Protocol: Validation of Sterility Assurance in ATMP Manufacturing

Objective: To validate the aseptic processing of an ATMP, providing the sterility assurance data required for GMP compliance and batch release [2] [11].

Methodology:

• Media Fill Simulation: Perform a minimum of three consecutive successful simulation runs mimicking the entire aseptic manufacturing process. Use a culture medium (e.g., Tryptic Soy Broth) that supports microbial growth in place of the actual cell-based product [11].
• Process Representation: The simulation must incorporate all critical aseptic operations, including vial transfers, cell feeding, harvesting, and formulation. It should account for the maximum number of interventions and the duration of the process typical of the actual manufacturing [11].
• Incubation and Analysis: Incubate the media-filled containers at 20-25°C for 7 days and then at 30-35°C for 7 days. Inspect for microbial growth (turbidity) throughout the incubation period [2].
• Acceptance Criteria: The simulation is considered valid only if no growth is observed in any of the media-filled containers, demonstrating that the aseptic process is robust and under control [11].

Protocol: Orthogonal Potency Assay Qualification

Objective: To establish at least two complementary (orthogonal) potency assays for an ATMP, as required by regulators to confidently measure the product's biological activity, a critical quality attribute for batch release [12].

Methodology:

• Assay Selection: Develop two independent assay formats based on different scientific principles.
  • Assay A (Mechanism-Based): A cell-based bioassay that measures the product's intended biological effect (e.g., target cell lysis for a CAR-T product).
  • Assay B (Attribute-Based): An analytical method quantifying a specific molecule or activity linked to potency (e.g., cytokine secretion via ELISA or flow cytometry for specific surface markers) [12].
• Assay Qualification: For each assay, define and validate performance characteristics including accuracy, precision (repeatability and intermediate precision), specificity, linearity, and range. For early-phase studies, qualification is required, while full validation is mandatory for Phase 3 and marketing authorization applications [12].
• Data Correlation: Test multiple ATMP batches and correlate the results from both assays. The data should demonstrate that the two methods, while measuring different aspects, are indicative of the product's overall potency and biological function [12].

The Scientist's Toolkit: Essential Reagents and Materials

The table below details key reagents and their functions in the development and quality control of ATMPs.

Table 2: Key Research Reagent Solutions for ATMP Development

Reagent/Material	Function in ATMP Context	Critical Regulatory Consideration
Cell Culture Media	Supports the growth and maintenance of cells used as the active substance.	Must be GMP-grade for clinical trial material manufacturing; research-grade materials are not permitted [12].
Vector/Genome Editing Machinery	Used for genetic modification in Gene Therapy Medicinal Products (GTMPs).	Classified as a starting material by the EMA and must be produced under GMP conditions [12].
Human Tissues and Cells (SoHOs)	The primary starting material for many ATMPs (e.g., CAR-T, tissue-engineered products).	Procurement and testing must comply with the EU Substances of Human Origin (SoHO) legislation [12].
Orthogonal Assay Components	Kits, antibodies, and reagents used in complementary analytical methods for identity, purity, and potency.	Assays must be qualified (early phase) or fully validated (late phase) per ICH Q2(R2) to ensure reliability of results for batch release [12].

Advanced Therapy Medicinal Products (ATMPs) represent a groundbreaking category of medications that utilize genes, cells, or tissues to treat, diagnose, or prevent diseases [13]. In the European Union, ATMPs are classified into three main types: gene therapy medicines, somatic-cell therapy medicines, and tissue-engineered medicines, with an additional category for combined ATMPs that incorporate one or more medical devices as integral components [13] [14]. These innovative products are subject to a robust regulatory framework centered on Regulation (EC) 1394/2007, which establishes specific rules for their authorization, supervision, and pharmacovigilance [14]. The regulation also led to the establishment of the Committee for Advanced Therapies (CAT) within the European Medicines Agency (EMA), which provides the specialized expertise required to evaluate these complex therapies [13] [14].

As biological-based products, ATMPs present unique manufacturing challenges that differentiate them from conventional pharmaceuticals [15]. Their complex nature, often involving living cells or tissues, necessitates tailored Good Manufacturing Practice (GMP) requirements to ensure consistent quality, safety, and efficacy while accommodating their specific characteristics [15] [6]. EudraLex Volume 4, the EU's detailed guidelines for GMP, contains a dedicated section—Part IV—that addresses these specific needs for ATMP manufacturing [16]. This specialized guidance exists alongside the general GMP framework but adapts the principles to account for the particular complexities of advanced therapies, creating a regulatory environment that balances rigor with appropriate flexibility for innovative products [6].

EudraLex Volume 4: Structure and Scope

EudraLex Volume 4, "The rules governing medicinal products in the European Union," contains the comprehensive Good Manufacturing Practice (GMP) guidelines for medicinal products for human and veterinary use [16] [17]. It serves as the operational blueprint that EU auditors use to assess whether products are manufactured to reliably safe and effective standards [17]. The Volume translates EU legislation, specifically Commission Directive (EU) 2017/1572 (for human medicinal products) and Commission Delegated Regulation (EU) 2017/1569 (for investigational medicinal products), into detailed operational expectations [16] [17].

The structure of EudraLex Volume 4 is organized into four distinct parts, each addressing specific aspects of pharmaceutical manufacturing:

• Part I outlines the basic GMP requirements for medicinal products, covering fundamental areas including the Pharmaceutical Quality System, personnel, premises and equipment, documentation, production, quality control, and outsourced activities [16] [17].
• Part II focuses specifically on the manufacture of active substances used as starting materials, with requirements aligned with the ICH Q7 guideline [17].
• Part III contains GMP-related documents that provide supplementary guidance and interpretation [16] [17].
• Part IV details the GMP requirements specific to Advanced Therapy Medicinal Products (ATMPs), recognizing their unique nature and manufacturing challenges [16].

The annexes to Volume 4 provide targeted guidance for specialized manufacturing contexts. For ATMPs, it is particularly important to note that Annex 2 (Manufacture of Biological active substances and Medicinal Products for Human Use) is no longer applicable to ATMPs, as these products are specifically covered by the dedicated guidelines in Part IV [16].

Table 1: Key Components of EudraLex Volume 4 Relevant to ATMPs

Component	Title/Focus	Relevance to ATMPs
Part IV	GMP for Advanced Therapy Medicinal Products	Primary set of rules specifically tailored to ATMPs
Annex 1	Manufacture of Sterile Medicinal Products	Relevant for sterile ATMPs, emphasizes Contamination Control Strategy
Annex 13	Investigational Medicinal Products	Applies to ATMPs used in clinical trials
Annex 15	Qualification and Validation	Critical for validating ATMP manufacturing processes
Annex 16	Certification by a Qualified Person and Batch Release	Governs batch release of finished ATMPs

Part IV GMP Guidelines for ATMPs: Key Principles and Current Focus

Part IV of EudraLex Volume 4 contains the GMP guidelines specifically tailored to Advanced Therapy Medicinal Products, acknowledging their distinct nature compared to conventional pharmaceuticals [16]. These guidelines operationalize the principle that ATMPs are subject to the same fundamental quality requirements as other medicinal products but require adaptations to address their specific characteristics, particularly when they contain viable biological materials [15] [6]. The current version of these guidelines was adopted in November 2017 and became operational in May 2018 [16] [6].

In May 2025, the European Medicines Agency (EMA) released a concept paper proposing significant revisions to Part IV, with the public consultation period open until 8th July 2025 [6]. These proposed updates reflect the evolving regulatory landscape and technological advancements in ATMP development. The key areas of focus in the proposed revision include:

• Alignment with Revised Annex 1: Harmonizing ATMP-specific GMP requirements with the updated Annex 1 (effective August 2023), particularly emphasizing the development and implementation of a comprehensive Contamination Control Strategy (CCS) [6].
• Integration of ICH Concepts: Incorporating principles from ICH Q9 (Quality Risk Management) and ICH Q10 (Pharmaceutical Quality System) to promote a systematic approach to quality risk management and establish robust pharmaceutical quality systems [6].
• Adaptation to Technological Advancements: Providing clarifications on qualifying, controlling, and managing new technologies in ATMP manufacturing, such as automated systems, closed single-use systems, and rapid microbiological testing methods [6].
• Updates on Cleanroom and Barrier Systems: Offering further clarifications on expectations for cleanroom classifications and the use of barrier systems like isolators and Restricted Access Barrier Systems (RABS), while maintaining provisions for biosafety cabinets used for individualized ATMP batches [6].
• Legal References and Definitions: Updating references and definitions related to starting materials of human origin to align with the new Regulation (EU) 2024/1938 on substances of human origin (SoHO), published in July 2024 [6] [14].

The relationship between these regulatory components and their application to ATMPs can be visualized through the following workflow:

Comparative Analysis: Part IV ATMP Guidelines vs. General GMP Requirements

The Part IV GMP guidelines for ATMPs maintain the fundamental quality principles of general GMP while introducing specific adaptations that acknowledge the unique challenges of manufacturing advanced therapies. These differences are particularly evident in areas such as starting materials, quality control approaches, and facility design, where the living nature of ATMP components necessitates specialized considerations [12] [15].

Critical Differentiating Factors for ATMPs

• Starting Material Requirements: For ATMPs, the EMA requires GMP-grade manufacturing of investigational medicinal products for first-in-human studies, with specific emphasis on human-origin materials [12] [6]. The updated guidelines clarify that ex vivo genome editing machinery must be defined as starting materials rather than raw materials, requiring manufacturing under GMP principles [12]. This differs from the FDA's "fit-for-purpose" approach for Phase 1 studies, though both agencies expect higher quality input materials than for early-phase small molecules [12].

• Quality Control and Testing Methods: Regulatory authorities demonstrate openness to alternative and complementary analytical methods for ATMP evaluation [12]. The EMA's guidelines for investigational ATMPs specifically state that orthogonal methods should be considered for analytical testing to ensure robustness and reliability, particularly when reference standards or validated methods are lacking [12]. The FDA similarly encourages orthogonal assays to build confidence in critical quality attributes, applying a "phase-appropriate" lens where assays need to be qualified but fully reliable for early-phase studies, progressing to full validation by Phase 3 [12].

• Facility and Environmental Controls: The proposed revisions to Part IV provide specific clarifications on cleanroom classifications and the use of barrier systems such as isolators and Restricted Access Barrier Systems (RABS) [6]. Importantly, the guidelines maintain provisions for biosafety cabinets to accommodate the manual manipulations often required for individualized ATMP batches, acknowledging the practical realities of manufacturing these personalized therapies [6].

Table 2: Comparison of Key GMP Requirements: General vs. ATMP-Specific

Aspect	General GMP Requirements	ATMP-Specific GMP Requirements
Starting Materials	GMP for active substances (Part II)	GMP for human-origin materials; genome editing machinery defined as starting materials
Quality Control	Validated methods (ICH Q2)	Orthogonal methods encouraged; phase-appropriate approach
Facility Controls	Defined cleanroom classifications	Specific provisions for biosafety cabinets and individualized batches
Sterility Assurance	Contamination Control Strategy (Annex 1)	Enhanced focus on aseptic processing for living cells
Regulatory Oversight	National competent authorities	Centralized with EMA's Committee for Advanced Therapies (CAT)

Manufacturing Challenges and Regulatory Responses

ATMP manufacturing faces several distinctive challenges that the Part IV guidelines aim to address. Contamination control is particularly critical since traditional sterilization methods are not feasible for living cell products, necessitating rigorous aseptic processing throughout manufacturing [15]. Tumorigenicity risk represents another significant concern, especially for pluripotent stem cell-derived products, requiring specific safety assessments including in vivo teratoma formation assays or, for somatic cell-based therapies, studies in immunocompromised models [15].

The comparability of products after manufacturing process changes presents a substantial hurdle for ATMP developers [15]. Regulatory authorities in the EU, US, and Japan have issued tailored guidance emphasizing risk-based comparability assessments, extended analytical characterization, and staged testing to ensure changes do not impact safety or efficacy [15]. The EU specifically recommends identifying Critical Quality Attributes (CQAs) most susceptible to process variations when conducting these assessments [15].

Experimental Considerations and Research Applications

Analytical Methodologies for ATMP Quality Control

The evaluation of ATMP quality employs specialized methodologies that address their complex biological nature. Orthogonal method validation represents a critical approach, where multiple independent analytical techniques are used to measure the same quality attribute, thereby building confidence in the results [12]. For gene therapy products, this typically includes techniques such as qPCR and next-generation sequencing (NGS) for assessing vector genome integrity, or combining infectivity assays with copy number assessments to fully characterize product quality [12].

The regulatory framework supports a phase-appropriate validation strategy where method validation rigor increases throughout product development [12]. Early-phase studies require methods that are reliable, reproducible, and sufficiently sensitive to support safety decisions, while late-phase and commercial stage products require full validation according to ICH Q2(R2) guidelines, including demonstration of accuracy, precision, specificity, linearity, range, and robustness [12]. Potency assays represent a particularly critical focus area, with regulators emphasizing the need for functional, biologically relevant assays that adequately reflect the mechanism of action [12].

Essential Research Reagents and Materials

The development and quality control of ATMPs requires specialized reagents and materials that meet stringent quality standards. The following table outlines key materials and their applications in ATMP research and development:

Table 3: Essential Research Reagent Solutions for ATMP Development

Reagent/Material	Function	Quality Considerations
Human-Derived Starting Materials	Source cells/tissues for ATMP manufacturing	Must comply with SoHO Regulation (EU 2024/1938); donor screening and testing requirements
Genome Editing Machinery	Genetic modification of cell-based therapies	Defined as starting material in EU; requires GMP-grade manufacturing
Cell Culture Media/Reagents	Expansion and maintenance of cellular products	Serum-free, xeno-free formulations preferred; vendor qualification essential
Viral Vector Systems	Gene delivery vehicles	Full characterization including identity, potency, purity; testing for replication-competent viruses
Critical Reagents	Used in potency assays and other quality tests	Qualified for intended use; stability monitoring program required

The experimental workflow for implementing these methodologies and reagents in ATMP batch release can be visualized as follows:

The specialized GMP framework established in Part IV of EudraLex Volume 4 creates a comprehensive regulatory environment specifically designed for the unique challenges of Advanced Therapy Medicinal Products. The upcoming revisions to these guidelines, expected following the May 2025 concept paper consultation, will further strengthen this framework by incorporating quality risk management principles, addressing technological advancements, and aligning with the new SoHO Regulation [6] [14].

For researchers and drug development professionals working with ATMPs, understanding these specialized requirements is essential for successful batch release and regulatory compliance. The batch release process for ATMPs requires particular attention to several key areas: comprehensive characterization of starting materials of human origin, implementation of orthogonal testing methods for critical quality attributes, rigorous contamination control strategies appropriate for living cells, and thorough documentation to support the qualification and decision-making of the Qualified Person responsible for certification [12] [16] [15]. As the regulatory landscape continues to evolve with the proposed revisions to Part IV, developers should maintain awareness of emerging requirements and engage early with regulators through available mechanisms such as the CAT classification procedure and scientific advice programs to navigate this complex framework successfully [12] [13].

The Role of the Pharmacopoeia and Marketing Authorisation in Setting Specifications

For Advanced Therapy Medicinal Products (ATMPs), which include gene therapies, somatic cell therapies, and tissue-engineered products, the specifications defining quality, safety, and efficacy are critically established through the interplay of two key regulatory elements: the pharmacopoeia and the marketing authorisation (MA) [13] [18]. The marketing authorisation, granted by regulatory authorities like the European Medicines Agency (EMA) in the EU, provides product-specific approval based on a thorough assessment of the benefit-risk ratio for a claimed indication [19]. Concurrently, the pharmacopoeia provides a compendium of public quality standards for medicinal products and their components, compliance with which is a legal requirement in many jurisdictions [20]. Within the context of batch release for ATMPs in the EU, this guide compares how these two instruments function, their distinct yet complementary roles, and the experimental protocols used to demonstrate compliance with the specifications they set.

Regulatory Framework and Scope

Marketing Authorisation for ATMPs

In the European Union, ATMPs must be authorized via the centralized procedure, with the EMA conducting a single scientific assessment for the entire market [21]. The Committee for Advanced Therapies (CAT) is pivotal in evaluating ATMP marketing authorisation applications [13] [18]. The MA is granted based on a detailed dossier containing pharmaceutical, preclinical, and clinical data that demonstrate a positive benefit-risk balance for the target patient population [19] [18]. For ATMPs, the regulatory framework includes specific pathways like conditional approval and the PRIME (Priority Medicines) scheme to expedite access for serious diseases with unmet medical needs [18].

The Legal Force of the Pharmacopoeia

Pharmacopoeias, such as the European Pharmacopoeia (Ph. Eur.), are legally recognized in EU directives [20]. Their standards help ensure the quality of medicines by providing public standards for drug substances, excipients, and finished products. Compliance with the relevant pharmacopoeia is not optional; it is a legal and regulatory requirement in the countries where they are applicable, and non-compliance can result in regulatory observations [20]. The specifications in a pharmacopoeia are typically general, applying to materials and products across manufacturers, whereas the MA sets product-specific specifications.

Table 1: Key Characteristics of Marketing Authorisation and Pharmacopoeia

Feature	Marketing Authorisation (MA)	Pharmacopoeia (e.g., Ph. Eur.)
Primary Role	Grants permission to market a specific medicine after assessing its benefit-risk profile [19]	Provides enforceable public quality standards for medicines and components [20]
Nature of Specifications	Product-specific, detailed in the approved product dossier	General, applicable to articles across multiple manufacturers and products
Legal Basis	Regulation (EC) No 726/2004, Directive 2001/83/EC, ATMP Regulation (EC) No 1394/2007 [18]	European Union Directives on Medicines (e.g., 2001/83/EC) [20]
Geographical Scope	Granted for the entire EU/EEA market via centralized procedure for ATMPs [21]	Applicable within the member states of the European Pharmacopoeia Convention
Focus of Control	Overall quality, safety, and efficacy of the final, specific product	Quality of substances, preparations, and specific test methods

Comparative Analysis of Specification Setting

Interaction in Setting Final Product Specifications

For ATMP batch release, the specifications for the final product are a composite of requirements from both the MA and the pharmacopoeia. The Marketing Authorisation lays down the product-specific specifications detailed in the approved registration dossier. These are derived from data generated during product development and are unique to that ATMP [19]. Meanwhile, the pharmacopoeia provides the generalized, foundational quality standards for raw materials, excipients, and certain test methods that must be applied wherever relevant [20]. For instance, a somatic cell therapy ATMP must conform to the specific potency and sterility specifications listed in its MA, while also using reagents and materials that comply with Ph. Eur. monographs.

Batch Control and Release Requirements

A critical stage where the roles of the MA and pharmacopoeia converge is batch release. Each batch of an ATMP must be tested to confirm it meets the specifications set in the MA before it can be released for use [22]. The Qualified Person (QP) is responsible for ensuring that each batch has been manufactured according to Good Manufacturing Practice (GMP) and meets the approval conditions [22]. The pharmacopoeia provides the official, often legally mandated, test methods for many of these controls, such as sterility testing or assays for endotoxins [20]. In some cases, for ATMPs imported from third countries, a waiver from routine batch testing in the EU may be granted by the CAT/CHMP during the MA evaluation, but only under strict conditions (e.g., very short shelf-life, limited batch size, and testing in a GMP-certified facility in a country with a mutual recognition agreement) [22].

Table 2: Comparison of Roles in ATMP Batch Release

Aspect	Marketing Authorisation	Pharmacopoeia
Batch Specification Setting	Defines the specific acceptance criteria for the release of each batch of the authorized product	Provides standard test methods and acceptance criteria for quality attributes (e.g., sterility, particulate matter)
Testing Methods	Accepts validated methods specified by the manufacturer; these may be pharmacopoeial methods or suitable alternatives [20]	Provides the official, recognized methods that are often the default standard; alternative methods must be validated to show equivalent performance [20]
Regulatory Oversight	National competent authorities are responsible for the official control authority batch release for biological products like ATMPs [2]	Compliance is verified by regulatory authorities during inspections; GMP requires consistent production and control per pharmacopoeial standards [20] [2]
Impact of Non-Compliance	Batch rejection, suspension, or withdrawal of the Marketing Authorisation	Regulatory observations, potential batch recall, and impact on the GMP license of the manufacturer

Experimental Protocols for Specification Compliance

Protocol for Demonstrating Pharmacopoeia Compliance

Objective: To verify that a critical raw material (e.g., a sodium chloride solution used in an ATMP process) complies with the current monograph of the European Pharmacopoeia (Ph. Eur.).

Methodology:

• Identification and Surveillance: Monitor the Ph. Eur. for updates to the relevant monograph through a structured pharmacopoeial surveillance process [20].
• Sample Preparation: Prepare the test sample as directed in the general notices and the specific monograph of the Ph. Eur.
• Analytical Testing: Perform all tests listed in the monograph (e.g., identification, assay, pH, clarity of solution, endotoxins, bacterial bioburden) using the compendial methods described.
• Method Verification (if applicable): If an alternative method to the compendial procedure is used, perform a full validation to demonstrate that the alternative method is equivalent or superior to the official method, as permitted by the general notices [20].
• Data Analysis: Compare the results obtained against the acceptance criteria defined in the monograph. The material complies only if it meets all requirements.

Protocol for Validation of a Product-Specific Potency Assay per MA Requirements

Objective: To develop and validate a cell-based bioassay to measure the biological activity of a somatic cell therapy ATMP, as required by its specific Marketing Authorisation.

Methodology:

• Assay Design: Develop a functional assay that measures a relevant biological mechanism of action (e.g., target cell killing by cytotoxic T cells).
• Qualification of Critical Reagents: Establish detailed specifications for all critical reagents (e.g., target cell lines, cytokines, detection antibodies) as per GMP. Their quality and consistency are crucial for assay performance [23] [2].
• Validation Parameters: Validate the assay according to ICH guidelines, assessing parameters including:
  • Accuracy and Precision: Through spike/recovery experiments and repeated testing over multiple days.
  • Linearity and Range: To demonstrate the assay produces results proportional to the analyte concentration in the specified range.
  • Specificity: To ensure the assay signal is specific to the intended mechanism.
  • Robustness: To test the assay's resilience to small, deliberate variations in method parameters.
• Setting Specification Limits: Establish justified acceptance criteria for batch potency based on data generated during clinical development and validation studies, which are then locked into the MA.

The Scientist's Toolkit: Key Research Reagent Solutions

The development and quality control of ATMPs rely on a suite of critical reagents and materials, the quality of which is governed by both pharmacopoeial standards and MA stipulations.

Table 3: Essential Materials for ATMP Development and Testing

Research Reagent/Material	Function	Governance by Pharmacopoeia and MA
Cell Culture Media	Provides nutrients and environment for the growth and maintenance of cells used in or constituting the ATMP.	Must comply with Ph. Eur. monographs for ingredients (e.g., salts, amino acids). The specific formulation and quality are critically defined in the MA dossier [23].
Vector for Gene Therapy	The vehicle (e.g., lentiviral vector) for delivering therapeutic genetic material into patient cells.	As an Active Substance, its manufacturing and quality control are extensively detailed in the MA. Testing may reference Ph. Eur. general chapters for analytics (e.g., sterility) [13] [18].
Human Serum Albumin	A common excipient used as a stabilizer in cell-based ATMP formulations.	Must conform to the Ph. Eur. monograph for Human Albumin Solution. Its sourcing and qualification data are included in the MA application [20].
Flow Cytometry Antibodies	Critical reagents for characterizing cell surface and intracellular markers to identify and quantify ATMP cell populations.	While not typically covered by a specific monograph, their use and validation for the specific product are controlled by the MA and GMP. Performance must be consistent and qualified [23].
Endotoxin Testing Reagents	Used in the Limulus Amebocyte Lysate (LAL) test to detect and quantify bacterial endotoxins as part of sterility assurance.	The test method is described in a Ph. Eur. general chapter. The MA sets the specific acceptance limit for the final ATMP product [20].

Implementation and Workflow

The relationship between the Marketing Authorisation, the pharmacopoeia, and the final quality control of an ATMP batch is a dynamic and integrated process. The following diagram illustrates the logical workflow of how these elements interact to ensure that only batches meeting all quality specifications are released.

The specification of ATMPs for batch release is not governed by a single document but is the result of a synergistic relationship between the Marketing Authorisation and the pharmacopoeia. The Marketing Authorisation provides the legally binding, product-specific framework for quality, safety, and efficacy, while the pharmacopoeia supplies the foundational, universally applicable quality standards and test methods. For researchers and developers, understanding this interplay is crucial. Navigating this complex landscape requires a strategy that incorporates early and continuous pharmacopoeial surveillance, rigorous product-specific validation as demanded by the MA process, and a robust quality system that seamlessly integrates both sets of requirements to ensure the consistent production of safe and effective ATMPs for patients.

The European Medicines Agency (EMA) has initiated a significant update to the Good Manufacturing Practice (GMP) guidelines specific to Advanced Therapy Medicinal Products (ATMPs). Released on May 8, 2025, the concept paper proposes revisions to Part IV of the EU GMP guidelines, with the public consultation period open until July 8, 2025 [6]. This revision aims to align the ATMP-specific GMP requirements with recent regulatory developments and technological advancements that have transformed the field since the current version was adopted in 2017 [6]. For researchers and drug development professionals, these changes represent a substantial shift in the regulatory expectations for ATMP manufacturing and quality control, particularly in the context of batch release requirements across EU member states.

The proposed revisions come at a critical juncture for the ATMP sector. Fifteen years after the implementation of the ATMP Regulation, the European landscape has witnessed the authorization of only 19 ATMPs, with a notable predominance of gene therapy products (84.2%) over somatic cell therapy and tissue-engineered products [24]. This regulatory evolution occurs alongside persistent challenges in pricing, reimbursement, and patient access, highlighting the importance of efficient and standardized manufacturing requirements to facilitate broader ATMP availability [24].

Key Proposed Revisions in the 2025 Concept Paper

The EMA's proposed revisions focus on several critical areas that will impact ATMP manufacturing and batch release protocols. These changes reflect the evolving understanding of ATMP quality control and aim to establish a more robust and flexible regulatory framework.

Table: Key Proposed Revisions to ATMP GMP Guidelines

Area of Revision	Current Emphasis	Proposed Changes	Impact on Batch Release
Contamination Control	Basic sterility assurance	Enhanced Contamination Control Strategy (CCS) aligned with revised Annex 1	More comprehensive environmental monitoring data required for batch release
Quality Risk Management	General quality systems	Systematic integration of ICH Q9 (Quality Risk Management) and ICH Q10 (Pharmaceutical Quality System)	Risk-based approaches to in-process controls and testing
Manufacturing Technologies	Traditional cleanroom operations	Qualification and control of automated systems, closed single-use systems, and rapid microbiological methods	Potential for reduced sterility testing requirements with validated rapid methods
Facility Requirements	Fixed cleanroom classifications	Clarified expectations for cleanroom classifications and barrier systems (isolators, RABS)	More flexible facility standards while maintaining product quality

Alignment with Revised Annex 1 and Contamination Control Strategies

A fundamental proposed change involves harmonizing ATMP-specific GMP requirements with the revised Annex 1, which has been in effect since August 2023 and introduces modifications for the manufacture of sterile medicinal products [6]. The updated guidelines will emphasize the development and implementation of a comprehensive Contamination Control Strategy (CCS), representing a shift from reactive testing to proactive quality assurance. For batch release requirements across EU countries, this means manufacturers will need to demonstrate robust environmental monitoring programs, particularly important for individualized ATMP batches that often involve manual manipulations in biosafety cabinets [6].

Integration of ICH Quality Guidelines

The revision plans to incorporate principles from ICH Q9 (Quality Risk Management) and ICH Q10 (Pharmaceutical Quality System), promoting a systematic approach to quality risk management throughout the product lifecycle [6]. This integration will affect batch release by encouraging a more science-based, risk-managed approach to determining critical quality attributes and critical process parameters. For ATMPs with limited batch sizes, such as those manufactured under the hospital exemption pathway, this may allow for more flexible yet scientifically justified release criteria tailored to specific product characteristics and patient populations [24] [25].

Adaptation to Technological Advancements

The concept paper acknowledges the emergence of new technologies in ATMP manufacturing, such as automated systems, closed single-use systems, and rapid microbiological testing methods [6]. The revised guidelines will provide clarifications on qualifying, controlling, and managing these technologies to ensure they do not detrimentally impact product quality. For batch release, this creates opportunities for implementing rapid microbial methods that can significantly reduce the time between product manufacturing and patient administration—a critical consideration for ATMPs with short shelf-lives [6].

Comparative Analysis: Current vs. Revised Batch Release Requirements

The proposed revisions to GMP guidelines for ATMPs will inevitably affect batch release requirements across EU member states. The following comparison highlights how these changes may influence key aspects of batch release protocols and documentation.

Table: Comparison of Batch Release Requirements Under Current and Revised Guidelines

Release Requirement	Current Framework	Proposed Revised Framework	Implications for Cross-Border Recognition
Sterility Testing	Traditional pharmacopoeial methods	Integration of validated rapid microbiological methods	Potential for faster release but requires harmonized validation approaches
Environmental Monitoring	Mainly focused on cleanroom classification	Comprehensive Contamination Control Strategy with data trending	More extensive documentation requirements for batch release
Quality Documentation	Fixed requirements	Risk-based approach aligned with ICH Q9	More flexibility but increased need for scientific justification
Starting Materials	Variable requirements for human-origin materials	Updated definitions and references for materials of human origin	Improved harmonization of donor screening requirements

Impact on Hospital Exemption and Non-Routine ATMPs

The Hospital Exemption (HE) pathway allows for the non-routine manufacture of custom-made ATMPs within specific EU member states, creating significant variability in batch release requirements across countries [24]. The proposed GMP revisions may influence how HE products are regulated, particularly regarding cleanroom standards and environmental monitoring. Research indicates that the HE pathway has been utilized differently across member states, with some countries like Belgium implementing stringent regulatory policies that have limited HE utilization, while others such as Finland, Germany, Italy, and the Netherlands have enabled modest availability of ATMPs through this pathway [24] [25].

The survey of Belgian academic and hospital producers revealed that meaningful human cell and tissue products are no longer available to surgeons and their patients due to stringent regulatory policies, highlighting how national interpretations of ATMP regulations can significantly impact product availability [24]. The proposed GMP revisions may either exacerbate or alleviate these disparities, depending on how they address the unique challenges of small-scale, non-routine ATMP manufacturing.

Harmonization of Allogeneic Donor Eligibility Requirements

A critical aspect of batch release for allogeneic ATMPs involves donor eligibility determination and testing of starting materials. The current EMA guideline provides only limited general guidance regarding donor screening and testing for infectious disease, reminding manufacturers that requirements must comply with relevant EU and member state-specific legal requirements [23]. This has created challenges for developers working across multiple jurisdictions, as differences in donor testing requirements can cause timeline delays and increased costs [23].

The proposed GMP revisions present an opportunity to enhance harmonization in this area, though the concept paper's specific approach to allogeneic donor testing remains unclear. In contrast to the EU's more flexible approach, the U.S. FDA is more prescriptive in its requirements for donor eligibility determination, including specific tests to be performed and laboratory qualifications [23].

Experimental Protocols for Implementing Revised GMP Requirements

Protocol 1: Validation of Rapid Microbiological Methods

Objective: To validate rapid microbiological methods as alternatives to traditional sterility testing for ATMP batch release.

Methodology:

• Comparative Testing: Perform parallel testing of identical samples using both rapid method and compendial method
• Validation Parameters: Assess method suitability, accuracy, precision, specificity, and limit of detection
• Matrix Studies: Validate method across different ATMP product types (cell therapies, gene therapies, tissue-engineered products)
• Robustness Testing: Evaluate method performance under varying conditions (temperature, incubation time, sample volume)

Data Analysis:

• Statistical comparison using equivalence testing with pre-defined acceptance criteria
• Demonstrate non-inferiority of rapid method compared to compendial method
• Establish sample sizes based on power analysis for detecting meaningful differences

Protocol 2: Implementation of Contamination Control Strategy

Objective: To develop and implement a comprehensive Contamination Control Strategy for ATMP manufacturing facilities.

Methodology:

• Risk Assessment: Apply ICH Q9 principles to identify potential contamination risks throughout manufacturing process
• Environmental Monitoring Program: Establish monitoring locations, frequencies, and alert/action limits based on risk assessment
• Data Trending: Implement statistical process control for monitoring data to detect trends and shifts
• Media Fill Simulations: Perform periodic process simulation studies to validate aseptic processing capabilities

Key Performance Indicators:

• Rate of excursions from environmental monitoring limits
• Time to detection of contamination events
• Effectiveness of corrective and preventive actions

Regulatory Framework Relationships

The following diagram illustrates the relationship between the proposed GMP revisions and other regulatory elements affecting ATMP batch release in the EU:

The Scientist's Toolkit: Essential Research Reagent Solutions

Table: Key Reagents and Materials for ATMP Batch Release Testing

Research Reagent	Function in Batch Release	Application in Revised GMP Context
Rapid Microbiology Kits	Alternative sterility testing	Enables faster release with reduced incubation times under revised guidelines
PCR-based Mycoplasma Detection	Mycoplasma testing	More sensitive and faster than culture methods, compatible with short ATMP shelf-lives
Flow Cytometry Panels	Cell phenotype and potency assessment	Critical for demonstrating identity and biological activity of cell-based ATMPs
Cytokine Release Assays	Safety testing for immunogenicity	Evaluates potential for adverse immune responses, especially important for allogeneic products
Endotoxin Testing Reagents	Bacterial endotoxin testing	Required safety test for all parenteral ATMPs, with updated methods under revision

The proposed 2025 revisions to EMA's GMP guidelines for ATMPs represent a significant evolution in regulatory thinking, with far-reaching implications for batch release requirements across EU member states. The increased emphasis on quality risk management, contamination control strategies, and advanced manufacturing technologies reflects the growing maturity of the ATMP field and the need for more sophisticated quality assurance approaches.

For researchers and drug development professionals, these changes will require adaptations in quality systems and testing methodologies, but also present opportunities for more efficient and scientifically justified batch release processes. The successful implementation of these revised guidelines will depend on continued dialogue between regulators, academic researchers, and industry stakeholders, particularly through the ongoing public consultation process open until July 8, 2025 [6].

As the ATMP field continues to evolve, these GMP revisions may help address some of the persistent challenges in product availability and cross-border recognition that have limited patient access to these transformative therapies, while maintaining the rigorous quality standards necessary for patient safety [24] [25].

Implementing Compliant Batch Release Procedures for ATMPs

Establishing the Pharmaceutical Quality System (PQS) and Quality Risk Management (ICH Q9)

The Pharmaceutical Quality System (PQS) and Quality Risk Management (QRM) form the foundational framework for ensuring drug product quality, safety, and efficacy throughout their lifecycle. For Advanced Therapy Medicinal Products (ATMPs), which include gene therapies, somatic cell therapies, and tissue-engineered products, implementing a robust PQS and QRM is particularly critical due to their complex nature and personalized manufacturing processes [26]. The International Council for Harmonisation (ICH) provides the central guidance for these systems through its ICH Q9 guideline, which outlines principles and tools for effective quality risk management [27] [28].

The recent update to ICH Q9 (Revision 1), effective 23 July 2023, introduces significant enhancements aimed at addressing subjectivity in risk assessments, improving the management of supply chain risks, and providing greater clarity on risk-based decision-making [29]. This revised guideline is especially pertinent for ATMPs, where manufacturing complexities and the use of novel technologies necessitate a highly adaptive and rigorous quality approach. The European Medicines Agency (EMA) emphasizes that ATMP manufacturing must comply with GMP requirements and encourages a risk-based approach tailored to the specific characteristics of these innovative products [8] [6].

Core Principles and Regulatory Framework

The Pharmaceutical Quality System (PQS)

The PQS provides a comprehensive framework that encompasses all aspects of pharmaceutical manufacturing, from drug development through commercial production. It is designed to ensure that products consistently achieve intended quality attributes and comply with marketing authorizations. For ATMPs, the PQS must be particularly adaptable to address unique challenges such as limited shelf-lives, complex supply chains, and personalized manufacturing scenarios [26] [6].

ICH Q9: Quality Risk Management

ICH Q9 provides a systematic process for quality risk management that can be applied to drug substances, drug products, biological products, and biotechnological products [28]. The guideline does not prescribe specific methodologies but rather offers a framework and suggests various tools that can be used for risk assessment and control [28].

The key components of the QRM process according to ICH Q9 include [28]:

• Risk Assessment: Identifying potential risks, analyzing their probability, severity, and detectability.
• Risk Control: Implementing strategies to reduce risks to an acceptable level.
• Risk Communication: Effectively communicating risks and control strategies to stakeholders.
• Risk Review: Continuously monitoring and reviewing the results of the QRM process.

Table 1: Key Changes in ICH Q9 (Revision 1) Effective July 2023

Area of Improvement	Key Changes in Revision 1	Relevance to ATMPs
Management of Subjectivity	Added dedicated subchapter (5.3) on managing and minimizing subjectivity in risk assessments; recommends considering suppositions and bias [29].	Critical for ATMPs where process knowledge may be limited and novel technologies are employed.
Supply Chain & Product Availability	New subchapter (6.1) on QRM's role in addressing product availability risks due to quality/manufacturing problems [29].	Essential for ATMPs with complex supply chains and personalized logistics [26].
QRM Formalities	Enhanced clarification on formal vs. informal risk analysis; emphasizes fluid transitions based on risk [29].	Supports phase-appropriate application for ATMPs from clinical trials to commercialization.
Risk-Based Decision Making	New subchapter (5.2) linking decision-making to knowledge management (ICH Q10) and data integrity [29].	Strengthens CMC strategies, a major challenge for ATMP developers [26].
Technical Updates	Updated references to standards; "risk identification" changed to "hazard identification" in risk management process [29].	Aligns terminology with evolving ATMP manufacturing and control paradigms.

Methodologies and Experimental Protocols

Quality Risk Management Tools

ICH Q9 suggests various structured methodologies that can be deployed within the PQS for systematic risk assessment. The selection of a specific tool depends on the context and complexity of the situation being evaluated.

Table 2: Key Methodologies for Quality Risk Management

Methodology	Type	Primary Function	Application Example in ATMPs
FMEA(Failure Modes and Effects Analysis)	Inductive	Assesses effects of potential failure modes on the system [28].	Identifying potential failure points in automated fill-finish systems for cell therapies.
FTA(Fault Tree Analysis)	Deductive	Identifies causal chains leading to undesirable events [28].	Investigating root causes of cross-contamination in multi-product facilities.
HAZOP(Hazard and Operability Study)	Inductive	Identifies deviations from initial system design [28].	Evaluating operational deviations in closed-system bioreactors.
HACCP(Hazard Analysis and Critical Control Points)	Inductive	Identifies and controls critical points in a process [28].	Establishing critical control points for viral clearance in starting materials.

Experimental Protocol: Implementing FMEA for an ATMP Manufacturing Process

The following protocol outlines a standardized approach for conducting a Failure Mode and Effects Analysis, a commonly used QRM tool in ATMP development and manufacturing.

Objective: To systematically identify and prioritize potential failure modes in a critical ATMP manufacturing process (e.g., cell separation) and establish risk control measures.

Materials and Reagents:

• Process Flow Diagrams: Detailed maps of the manufacturing unit operations.
• FMEA Worksheet: Template for documenting failure modes, causes, effects, and controls.
• Multidisciplinary Team: Personnel from Quality, Process Development, Manufacturing, and Engineering.
• Risk Ranking Criteria: Pre-defined scales for severity, occurrence, and detection.

Procedure:

• Define the Scope: Select a specific manufacturing process (e.g., magnetic cell separation). Create a detailed process flow diagram identifying all process steps.
• Assemble Team: Convene a multidisciplinary team with knowledge of the process, product, and quality requirements.
• Identify Failure Modes: For each process step, brainstorm potential failure modes (how the process could fail).
• Analyze Effects: For each failure mode, determine the potential effects on the product's Critical Quality Attributes (CQAs).
• Assign Risk Scores: Score each failure mode using pre-defined scales (typically 1-10) for:
  • Severity (S): Impact on product quality or patient safety.
  • Occurrence (O): Probability of the failure occurring.
  • Detection (D): Likelihood of detecting the failure before impact.
• Calculate Risk Priority: Compute the Risk Priority Number (RPN): RPN = S × O × D.
• Identify Controls: For each failure mode, document existing process controls and detection methods.
• Plan Mitigation: For high RPN scores, define additional risk mitigation actions. Re-score RPN after proposed actions.
• Document and Review: Document the complete FMEA. Establish a schedule for risk review based on process changes or new information.

Expected Output: A prioritized list of process risks with assigned mitigation strategies, integrating QRM into the PQS and providing documented evidence for regulatory submissions.

Diagram: FMEA Implementation Workflow for QRM.

Comparative Analysis of Regulatory Expectations

EU versus US Perspectives on QRM

While ICH Q9 provides a harmonized foundation for quality risk management, regulatory expectations can vary in implementation, particularly for complex products like ATMPs/CGTs. Understanding these nuances is crucial for global development strategies.

European Union Perspective: The EU emphasizes a stringent application of QRM, with specific GMP guidelines for ATMPs (Part IV of EU GMP) currently under revision to better align with the updated ICH Q9 and technological advancements [6]. The EMA requires GMP-grade manufacturing of investigational medicinal products even for first-in-human studies, reinforcing a high-quality standard from the earliest development phases [26]. The upcoming revision of the ATMP GMP guidelines also emphasizes the integration of ICH Q9 principles and the development of a Contamination Control Strategy (CCS) as outlined in the revised GMP Annex 1 [6].

United States Perspective: The FDA applies a more phase-appropriate approach to QRM and CMC requirements for CGTs. For Phase 1 trials, facilities need to be "fit-for-purpose" with emphasis on patient safety and sterility assurance, not necessarily full commercial GMP compliance [26]. Process consistency becomes critical by Phase 2, with full GMP compliance expected by Phase 3 [26]. The FDA has also demonstrated openness to alternative analytical methods (e.g., orthogonal methods, NAMs) when scientifically justified, which is particularly relevant for characterizing complex ATMPs [26].

Risk-Based Approaches to Analytical Testing

Both EMA and FDA encourage the use of orthogonal methods (methods using different scientific principles to measure the same attribute) to build confidence in Critical Quality Attributes (CQAs) for ATMPs [26]. This is a practical application of QRM to analytical control strategies.

Table 3: Research Reagent Solutions for ATMP Characterization

Reagent / Solution	Function	Application Example
GMP-Grade Starting Materials	Ensure quality and traceability of input materials; mitigate risk to patient safety [26].	Plasmid DNA for gene therapy vector production.
Orthogonal Assay Reagents	Enable measurement of the same product attribute using different scientific principles [26].	qPCR and NGS reagents for vector genome integrity.
Potency Assay Reagents	Measure biological activity; functional, biologically relevant assays are expected by regulators [26].	Cell-based assays with reference standards.
Sterility Testing Kits	Rapid microbiological methods adapted for short-lived ATMPs.	BacT/ALERT culture bottles for final product release.

The establishment of a robust Pharmaceutical Quality System integrated with proactive Quality Risk Management according to ICH Q9 is fundamental for the successful development and commercialization of ATMPs. The recent revision of ICH Q9 strengthens this framework by providing enhanced guidance on managing subjectivity, supply chain risks, and formalizing risk-based decision-making processes. For researchers and developers operating in the dynamic ATMP landscape, a deep understanding of these principles—and their nuanced application across different regulatory jurisdictions—is not merely a regulatory expectation but a critical component of ensuring that these transformative therapies reach patients with the highest assurance of quality, safety, and efficacy.

This guide details the batch release process for Advanced Therapy Medicinal Products (ATMPs) in the European Union, a critical pathway ensuring these complex therapies meet stringent safety, quality, and efficacy standards before reaching patients.

Advanced Therapy Medicinal Products (ATMPs) represent a frontier in medical treatment, comprising gene therapies, somatic-cell therapies, and tissue-engineered products [13]. Their inherent complexity, often involving living cells or genetic material as the active substance, necessitates a specialized and robust regulatory framework for batch release. In the European Union, the European Medicines Agency (EMA) centrally authorizes all ATMPs, providing a single evaluation procedure [13]. The regulatory landscape is dynamic, with recent updates to Good Manufacturing Practice (GMP) guidelines specifically for ATMPs, emphasizing the integration of ICH Q9 (Quality Risk Management) and ICH Q10 (Pharmaceutical Quality System) principles [6]. The batch release process is a cornerstone of this framework, designed to verify that each batch of an ATMP conforms to its marketing authorization before it is released to the market.

The EU Regulatory Framework for ATMP Batch Release

The legal foundation for ATMP batch release is established in EudraLex Volume 4, the EU's guide to Good Manufacturing Practice (GMP) [16]. For ATMPs, Part IV of EudraLex Volume 4 provides the specific GMP requirements, which are distinct from those for conventional biologics or chemical medicines [16]. A significant recent development is the EMA's proposal to revise this Part IV, aiming to align it with the updated GMP Annex 1 on sterile medicinal products and to incorporate modern manufacturing technologies like automated and closed systems [6]. This update, once finalized, will further refine the quality expectations for ATMPs. The entire process is supervised by the EMA's Committee for Advanced Therapies (CAT), which possesses the specific expertise required for evaluating these sophisticated products and provides draft opinions on their quality, safety, and efficacy [13].

Table: Key Regulatory Bodies and Guidelines for ATMP Batch Release in the EU

Entity/Guideline	Role and Focus in ATMP Batch Release
European Medicines Agency (EMA)	Centralized authorization and oversight of all ATMPs in the EU [13].
Committee for Advanced Therapies (CAT)	Provides scientific expertise for ATMP evaluation, including quality aspects [13].
EudraLex Volume 4, Part IV	Contains the GMP guidelines specific to Advanced Therapy Medicinal Products [16].
Qualified Person (QP)	An individual legally responsible for certifying that each batch has been produced in compliance with GMP and its marketing authorization before release [16].
Official Control Authority Batch Release (OCABR)	A mandatory additional control for certain biological medicines, conducted by a National Competent Authority.

The Batch Release Pathway: A Step-by-Step Analysis

The batch release process for ATMPs is a multi-layered verification system. It begins with the manufacturer's internal quality control and culminates in certification by a Qualified Person, with an additional tier of official control for certain products.

Certification by the Qualified Person (QP)

The QP certification is a legal requirement for every batch of an ATMP placed on the EU market. The QP, named on the manufacturer's license, must personally certify that the batch complies with several key requirements [16]:

• Good Manufacturing Practice (GMP): The batch was manufactured in accordance with GMP standards, specifically those outlined in EudraLex Volume 4, Part IV for ATMPs.
• Marketing Authorization (MA): The batch conforms to the details provided in the EU marketing authorization for the product.
• Principles and Guidelines of GMP: All activities, including any outsourced operations, adhere to established GMP principles.

This certification is based on a thorough review of the batch documentation, which includes records of production, quality control testing, and the conditions of storage and transport. For autologous ATMPs (custom-made for individual patients from their own cells), this process is adapted to the batch-of-one reality, requiring streamlined yet rigorous documentation and verification procedures.

Official Control Authority Batch Release (OCABR)

For certain high-risk biological products, including some ATMPs, an additional step follows QP certification: the Official Control Authority Batch Release (OCABR). This is a mandatory control performed by a National Competent Authority (e.g., the MHRA in the UK or a regulatory body in an EU member state). The OCABR process involves [16]:

• The manufacturer submits a sample and the full batch protocol to the Official Medicines Control Laboratory (OMCL) of the competent authority.
• The OMCL reviews the protocol and may perform its own laboratory tests to verify that the batch meets the authorized specifications.
• Upon successful verification, the competent authority issues a batch release certificate, which is required for the batch to be distributed.

It is important to note that OCABR is an independent verification that supplements, rather than replaces, the legal duty of the QP.

The Role of Quality by Design (QbD) in Streamlining Release

A proactive approach to quality, Quality by Design (QbD), is increasingly critical for successful ATMP batch release. QbD is a systematic, risk-based framework for process development that builds quality into the product from the very beginning [30]. Its implementation directly supports the batch release process by:

• Defining a Quality Target Product Profile (QTPP): This is a prospective summary of the quality characteristics of the drug product.
• Identifying Critical Quality Attributes (CQAs): These are the physical, chemical, biological, or microbiological properties that must be controlled to ensure product quality.
• Linking CQAs to Process Parameters: Through Design of Experiments (DoE), manufacturers can establish a "Design Space"—a multidimensional combination of process parameters and material attributes that have been demonstrated to assure quality [30].

When a process is well-understood and controlled within its design space, it provides a strong scientific rationale for the QP to certify the batch, as the product's quality is assured by design, not just by end-product testing.

Table: Comparison of Key Concepts in ATMP Batch Release

Concept	Description	Impact on Batch Release
Qualified Person (QP)	A legally recognized expert responsible for batch certification [16].	The final internal gatekeeper before a batch can be released for sale or use.
Official Control Authority Batch Release (OCABR)	A mandatory external verification by a National Competent Authority for certain biologicals [16].	An additional layer of regulatory oversight and safety assurance.
Quality by Design (QbD)	A systematic approach to development that emphasizes product and process understanding [30].	Provides a scientific foundation for QP certification and can reduce release testing through process validation.
Critical Quality Attributes (CQAs)	Product characteristics critical to safety and efficacy, must be controlled within appropriate limits [30].	Define the key parameters that must be verified during batch release.
Design Space	The established range of process parameters that ensures product CQAs are met [30].	Operating within a validated design space gives the QP higher confidence in batch quality.

Experimental Protocols for Batch Release

The batch release of an ATMP is underpinned by a suite of analytical experiments designed to confirm the product's identity, purity, potency, and safety. The specific protocols are unique to each product but fall into general categories.

Identity, Purity, and Potency Assays

• Protocol for Cell Identity (Flow Cytometry): This method is standard for characterizing cell surface and intracellular markers.
  • Methodology: A single-cell suspension is incubated with fluorescently labeled antibodies specific to target markers. The cells are then passed through a flow cytometer, which lasers excite the fluorophores, and detectors measure the emitted light.
  • Data Analysis: The percentage of cells expressing the marker(s) of interest (e.g., CD19 for CAR-T cells) is quantified. Results must fall within the predefined specifications set in the marketing authorization.
• Protocol for Potency (Functional Assay): Potency measures the biological activity of the ATMP, which is critical for its therapeutic effect.
  • Methodology (e.g., Cytotoxic Activity for CAR-T): Target cells expressing the relevant antigen are co-cultured with the ATMP (e.g., CAR-T cells). Target cell killing is measured using a real-time cell analyzer or by quantifying lactate dehydrogenase release.
  • Data Analysis: The lytic activity is calculated, often as a percentage of specific killing or as an EC50 value. The batch must demonstrate a minimum level of potency to be released.
• Protocol for Purity and Safety (Mycoplasma Testing): This is a mandatory safety test to ensure the product is free from mycoplasma contamination.
  • Methodology: The sample is inoculated into both liquid and solid mycoplasma culture media and incubated for up to 28 days. Alternatively, a validated nucleic acid amplification technique like PCR can be used.
  • Data Analysis: For the culture method, the absence of any mycoplasma growth confirms the test. For the PCR method, the absence of specific amplification products indicates a negative result.

Novel Analytical Workflows: QbD and DoE

Implementing a QbD approach requires sophisticated experimental protocols during process development, which in turn simplifies and strengthens the subsequent batch release.

• Protocol for Defining the Design Space (Design of Experiments): This is a structured, statistical method for understanding the relationship between process inputs and product CQAs [30].
  • Methodology: Instead of testing one factor at a time, multiple Critical Process Parameters are varied simultaneously according to a pre-defined experimental matrix. For example, in a cell culture process, factors like seeding density, media composition, and bioreactor parameters might be varied.
  • Data Analysis: The resulting CQA data (e.g., cell viability, transduction efficiency) is analyzed using multivariate regression. This model identifies which parameters significantly impact CQAs and defines their optimal ranges, thus establishing the "design space."

The following diagram illustrates the logical relationship between QbD elements and the final batch release, forming a continuous assurance cycle.

The Scientist's Toolkit: Essential Reagents and Materials

Successful batch release testing relies on a suite of high-quality, validated reagents and analytical systems.

Table: Key Research Reagent Solutions for ATMP Batch Release

Tool/Reagent	Function in Batch Release
Characterized Cell Lines	Serve as positive controls or target cells in identity and potency assays (e.g., for flow cytometry or cytotoxic activity tests).
Fluorochrome-conjugated Antibodies	Essential for flow cytometry-based identity and purity tests, enabling detection of specific cell markers.
Validated PCR/Kits	Used for safety testing (e.g., mycoplasma, sterility, vector copy number analysis) and identity testing.
Cell Culture Media & Reagents	Critical for executing functional potency assays and for any required cell-based assays post-thaw.
Reference Standards	Well-characterized standards (e.g., from EDQM) used to calibrate equipment and validate analytical methods, ensuring data accuracy [31].

The batch release process for ATMPs, from QP certification to Official Control Authority Batch Release, is a comprehensive and rigorous system designed to manage the unique risks associated with these transformative therapies. The integration of Quality by Design principles is no longer just a best practice but a strategic necessity to build robustness into ATMP manufacturing and facilitate a science-driven release process [30]. As the regulatory landscape evolves, with ongoing updates to GMP guidelines and the adoption of novel manufacturing technologies like point-of-care production [31], the batch release framework will continue to adapt. For researchers and developers, a deep understanding of these requirements, coupled with robust experimental data from well-designed protocols, is paramount for successfully navigating the path from the lab to the clinic.

For developers of Advanced Therapy Medicinal Products (ATMPs), navigating the complex regulatory environment requires a meticulous approach to documentation. The European Medicines Agency (EMA) has proposed significant revisions to EU GMP Chapter 4 (Documentation) and Part IV (GMP specific to ATMPs) to address emerging technologies and strengthen data integrity requirements [32] [6]. These changes directly impact how master formulas and batch records are created, maintained, and reviewed within the framework of official control authority batch release (OCABR) procedures across EU member states.

The revised Chapter 4, currently in draft with a final version expected in 2026, introduces a comprehensive life cycle approach to documentation, taking data governance and risk management into account [32]. For ATMPs, this means that documentation systems must now be designed to handle the unique challenges of personalized therapies, small batch sizes, and complex supply chains while ensuring full compliance with the stringent principles of data integrity.

Comparative Analysis of Updated Documentation Requirements

Key Changes in EU GMP Chapter 4 and Alignment with ATMP-Specific Guidelines

The proposed revisions to EU GMP Chapter 4 represent a substantial expansion from the 2011 version, growing from 9 to 17 pages with approximately 50% completely rewritten content [32]. These changes align with technological advancements in ATMP manufacturing and introduce more detailed requirements for all GMP documentation.

Table: Key Changes in EU GMP Chapter 4 Documentation Requirements

Documentation Element	Previous Requirements (2011)	Updated Requirements (2025 Draft)	Specific Impact on ATMPs
Data Integrity Principles	Implied expectations for data reliability	Formalized ALCOA++ principles with explicit requirements for all data types [32] [33]	Critical for autologous therapies with patient-specific data chains
Documentation Lifecycle	Basic retention requirements	Comprehensive life cycle approach with defined data governance [32]	Ensures traceability from starting materials to final product
Electronic Systems & Signatures	Limited guidance on electronic records	Detailed requirements for electronic signatures, hybrid systems, and AI utilization [32]	Supports automated systems and closed single-use systems in ATMP manufacturing [6]
Risk Management	General quality risk management principles	ICH Q9 integration throughout documentation processes with documented risk assessments [6]	Essential for managing variability in biological starting materials
Outsourced Activities	Basic contract requirements	Enhanced controls for documentation archiving by service providers and clearer chain of responsibility [32]	Crucial for ATMPs often involving multiple specialized contractors

The EMA's parallel revision of Part IV of the GMP guidelines specific to ATMPs further emphasizes the alignment with the updated Annex 1 (manufacture of sterile medicinal products) and incorporates principles from ICH Q9 (Quality Risk Management) and ICH Q10 (Pharmaceutical Quality System) [6]. This dual regulatory update ensures that ATMP documentation systems address both general GMP standards and product-specific challenges.

Master Formula and Batch Record Requirements in the Context of ATMPs

For ATMPs, the master formula and batch manufacturing record represent critical documentation that must accommodate both the standardized elements of pharmaceutical production and the patient-specific aspects of these innovative therapies.

Master Formula Requirements: The master formula for ATMPs must contain comprehensive information that ensures batch-to-batch consistency despite the inherent variability of biological systems. The updated guidelines emphasize that manufacturing instructions must be tightened to ensure consistency and reproducibility, aligning with the FDA's process validation lifecycle approach [33]. Specific requirements include:

• Clearly defined critical process parameters (CPPs) and critical quality attributes (CQAs) with established acceptance criteria
• Comprehensive descriptions of all materials, including substances of human origin (SoHOs) with traceability to donor [12]
• Detailed manufacturing instructions that account for the use of automated systems, closed single-use systems, and rapid microbiological testing methods [6]

Batch Manufacturing Record Updates: The revised Chapter 4 introduces specific requirements for batch records that are particularly relevant to ATMPs:

• Enhanced Traceability: Records must now include raw data and distribution information, underpinning regulators' expectations for complete traceability [33]. For autologous ATMPs, this means documenting the chain of identity from patient donation through to final product administration.
• Electronic Batch Records: The guidelines officially acknowledge electronic signatures for the first time, requiring they be legally binding, traceable, and compliant with ALCOA++ principles [32] [33]. This is particularly important for ATMPs utilizing automated and digital systems.
• Controlled Form Sets: The new requirements include specific controls for numbered test protocol forms, which has significant implications for the quality control of individualized ATMP batches [32].

Table: ATMP-Specific Documentation Challenges and Regulatory Solutions

ATMP Characteristic	Documentation Challenge	Regulatory Solution	Implementation Example
Patient-Specific (Autologous)	Maintaining chain of identity and preventing mix-ups	Enhanced traceability requirements and unique identifier systems	Barcode systems linking patient to product throughout manufacturing
Small Batch Sizes	Justifying batch definition and homogeneity	Risk-based approach with documented justification [32]	Definition of "super batches" with rigorous in-process controls [34]
Complex Supply Chains	Managing documentation across multiple sites/contractors	Direct written contracts between all parties defining documentation responsibilities [34]	Contractual requirements for data exchange between apheresis centers, manufacturers, and treatment sites
Starting Material Variability	Characterizing and controlling biological variability	Orthogonal methods for analytical testing and comprehensive characterization [12]	Multiple assay methods to fully characterize potency and purity

Batch Release Requirements for ATMPs in EU Countries

Official Control Authority Batch Release (OCABR) Framework

The EU regulatory framework for batch release of human biologicals, including ATMPs, is established under Article 114 of Directive 2001/83/EC [35]. The Official Control Authority Batch Release (OCABR) procedure requires that batches of immunological medicinal products or medicinal products derived from human blood or plasma be tested by an Official Medicines Control Laboratory (OMCL) before being placed on the market.

The core administrative procedure for OCABR is defined in the EU Administrative Procedure for Official Control Authority Batch Release, which is used by OMCLs when implementing OCABR at the national level [35]. The key steps in this process include:

• The member state informs the Marketing Authorisation Holder (MAH) that its authorised human biological medicinal product is subject to OCABR
• Samples of the batch to be released are sent, along with production and control protocols, to an OMCL within the EU/EEA
• If results are satisfactory, the Competent Authority issues an "Official Control Authority Batch Release Certificate"
• The MAH must provide a copy of the OCABR Certificate to the Competent Authority of the member state where the batch will be marketed
• The certificate is recognized by all members of the network [35]

For ATMP developers, early engagement with OMCLs is critical. The EMA strongly recommends that applicants enter into collaboration with one or more OMCLs at least one year before submission of the marketing authorisation application to allow for an exchange of information [35].

Documentation Requirements for ATMP Batch Release Across EU Member States

The batch release process for ATMPs requires comprehensive documentation that demonstrates compliance with the approved specifications laid down in the relevant monographs of the European Pharmacopoeia and in the relevant marketing authorisation [35]. The specific documentation requirements include:

• Production and Control Protocols: Detailed documentation of the entire manufacturing process, including in-process controls and testing results
• Quality Control Documentation: Complete records of all quality control testing, including methods, results, and deviations
• Starting Material Documentation: Comprehensive traceability and characterization data for all starting materials, particularly substances of human origin [12]
• Stability Data: Documentation supporting the product's stability through the claimed shelf-life
• Comparability Data: For any process changes, comprehensive data demonstrating comparability to the original process [36]

The following diagram illustrates the complete OCABR process for ATMPs from manufacturing through to market release, highlighting documentation requirements at each stage:

ATMP Batch Release Workflow

Experimental Protocols for Documentation Compliance

Protocol for Validating Electronic Documentation Systems in ATMP Manufacturing

Objective: To validate that electronic documentation systems (e.g., Electronic Batch Records, QMS software) comply with updated EU GMP Chapter 4 requirements and ALCOA++ principles for ATMP manufacturing.

Methodology:

• System Requirements Mapping: Map all Chapter 4 requirements to system functionalities, with particular attention to data integrity controls for hybrid systems [32] [33]
• ALCOA++ Principle Testing: Verify compliance with each ALCOA++ principle through structured testing protocols:
  • Attributable: Validate user access controls and electronic signature functionality
  • Legible: Confirm data remains readable throughout retention period
  • Contemporaneous: Verify time-stamping functionality and prevent back-dating
  • Original: Validate creation and storage of true copies
  • Accurate: Test data transcription accuracy and error rates
  • Complete: Verify no data omission through system integration testing
  • Consistent: Confirm standardized workflows across system modules
  • Enduring: Test data backup, recovery, and archive functionalities
  • Available: Validate search and retrieval capabilities across data lifecycle
  • Traceable: Verify comprehensive audit trail functionality [33]
• Risk Assessment: Conduct formal risk assessment using ICH Q9 principles to identify and mitigate data integrity risks specific to ATMP processes [6]
• Supplier Qualification: For commercially provided systems, verify supplier quality management system and technical support capabilities [34]

Acceptance Criteria:

• Zero critical defects in data integrity controls
• 100% compliance with ALCOA++ principles in operational scenarios
• Successful data recovery within defined timeframe in disaster recovery test
• Comprehensive audit trail capturing all GMP-relevant data changes

Protocol for Implementing the New Validation Master Plan Requirement

Objective: To establish and implement the mandatory Validation Master Plan required by the revised Chapter 4, specifically addressing ATMP manufacturing processes [32].

Methodology:

• Scope Definition: Define the scope of qualification and validation activities, including facility, equipment, utilities, manufacturing processes, cleaning, and analytical methods
• Risk-Based Approach: Apply risk assessment to determine validation intensity and prioritization, focusing on patient safety and product quality aspects critical for ATMPs [6]
• Documentation Structure: Establish hierarchy of validation documents, defining relationships between validation plan, protocols, reports, and standard operating procedures
• Change Control Integration: Develop procedures for managing changes to validated状态, including documentation requirements and re-validation criteria
• Periodic Review: Establish schedule and methodology for periodic review of validated状态

Acceptance Criteria:

• Successful regulatory inspection with no critical findings related to validation approach
• On-time completion of all validation activities per approved schedule
• Effective change control process maintaining validated状态 through process improvements
• Successful batch certification and release without validation-related delays

Table: Research Reagent Solutions for ATMP Documentation and Compliance

Tool/Resource	Function	Application in ATMP Documentation
QT9 QMS Software	Quality Management System enabling compliance with ALCOA++ principles through automated workflows [33]	Manages document control, training records, CAPA, and audit trails for ATMP manufacturing
Electronic Batch Record (EBR) Systems	Digital systems for creating, managing, and archiving batch manufacturing records	Ensures real-time data capture and compliance with electronic signature requirements [32]
Orthogonal Analytical Methods	Multiple independent methods measuring the same quality attribute [12]	Provides comprehensive characterization of ATMP critical quality attributes as required by regulators
Data Integrity Assessment Tools	Frameworks for evaluating ALCOA++ compliance across paper, electronic, and hybrid systems [33]	Identifies and mitigates data integrity risks throughout ATMP documentation lifecycle
Validation Master Plan Template	Structured approach to documenting validation activities as required by revised Chapter 4 [32]	Ensures comprehensive validation of ATMP-specific processes and systems

The evolving regulatory landscape for ATMP documentation requires a proactive approach to implementing the updated EU GMP Chapter 4 requirements. By understanding the specific changes to master formula and batch record requirements, and their interaction with the OCABR process, ATMP developers can establish robust documentation systems that ensure regulatory compliance while supporting the unique characteristics of these innovative therapies. The experimental protocols and tools outlined provide a practical foundation for addressing these challenges in a structured, scientifically sound manner.

The development of Advanced Therapy Medicinal Products (ATMPs) presents unique challenges, particularly in managing the complex journey of starting materials of human origin. These materials—encompassing blood, tissues, and cells—form the foundational biological components for gene therapies, somatic cell therapies, and tissue-engineered products [8] [15]. Unlike traditional pharmaceutical manufacturing, ATMP production requires navigating a complex regulatory landscape that governs every stage from donor selection to final product release [12]. The European Medicines Agency (EMA) mandates that developers must be aware of legislation governing different stages of the medicine development process, including Good Manufacturing Practice (GMP), Good Clinical Practice (GCP), and Good Laboratory Practice (GLP) requirements specific to these biological materials [8].

A critical challenge in this field involves the successful translation of non-clinical Good Laboratory Practice (GLP) results into GMP-compliant manufacturing processes that reliably meet quality specifications defined during product development [15]. GLP focuses on protecting scientific data from contamination and ensuring data accuracy and reliability during preclinical development, while GMP protects the product itself from contamination during manufacturing [15]. This transition is particularly complex for ATMPs due to the inherent variability of biological materials and the stringent controls needed to ensure final product safety, quality, and efficacy.

Comparative Analysis of EU and US Regulatory Requirements

Key Regulatory Definitions and Classifications

The regulatory classification of ATMPs differs significantly between the European Union and the United States, impacting how starting materials are defined and managed [12].

Table 1: Regulatory Classification of ATMPs/CGTs in EU vs. US

Aspect	European Union (EU)	United States (US)
Umbrella Term	Advanced Therapy Medicinal Products (ATMPs)	Cell and Gene Therapies (CGTs)
Product Categories	- Gene Therapy Medicinal Products (GTMPs)- Somatic Cell Therapy Medicinal Products (sCTMPs)- Tissue Engineered Products (TEPs)- Combined ATMPs (cATMPs)	- Human Gene Therapies- Somatic Cell Therapies(No separate category for TEPs)
Governing Bodies	European Medicines Agency (EMA)Committee for Advanced Therapies (CAT)	Food and Drug Administration (FDA)Center for Biologics Evaluation and Research (CBER)Office of Therapeutic Products (OTP)
Starting Materials Approach	GMP-grade manufacturing required for investigational products in first-in-human studies [12]	"Fit-for-purpose" facility for Phase 1, with higher quality input materials than early-phase small molecules [12]

In the EU, the classification of combined products differs notably. For example, if a product combines a cell and gene therapy, such as CAR-T cells, it is always classified as a gene therapy [12]. The regulatory framework continues to evolve, with proposed EU pharmaceutical legislation aiming to redefine GTMPs to include genome editing techniques and synthetic nucleic acids, which were previously categorized as chemical medicinal products [12].

Donor Tracing and Quality Control Requirements

Both regulatory systems emphasize rigorous donor tracing and quality controls, though with different implementation frameworks.

Table 2: Donor Tracing and Quality Control Requirements

Requirement	European Union (EU)	United States (US)
Donor Tracing	Required under Substances of Human Origin (SoHO) legislation [12]	Required under FDA guidance for CGTs
Quality Control Testing	Must comply with relevant legislation (Directive 2002/98/EC and associated directives for blood; Directive 2004/23/EC for tissues and cells) [8]	Phase-appropriate approach, but higher standards for starting materials than small molecules [12]
GMP Application	Full GMP required for investigational products in first-in-human studies [12]	Phase-appropriate GMP; process consistency expected by Phase 2 [12]
Legislative Updates	SoHO legislation revised in 2024, extending to donor registration, collection, testing, storage, distribution, import, and export [12]	FDA guidance documents updated regularly to reflect technological advancements

The EU's revised SoHO legislation, which brings blood products, tissues and cells under one regulation, seeks to provide greater protection to patients and donors [12]. This has significant implications for ATMP developers, as all parties handling any SoHO activities must comply with the new regulation by August 2027 [12].

Experimental Protocols for Quality Assessment

Donor Eligibility and Material Qualification

Establishing robust donor screening protocols is fundamental to ensuring the safety of starting materials. The following methodology outlines a comprehensive approach:

Materials and Reagents:

• Donor history questionnaire
• Serological testing kits (HIV-1/HIV-2, HBV, HCV, etc.)
• Nucleic acid testing (NAT) equipment
• Sterile collection kits with unique identifiers
• Temperature monitoring devices

Procedure:

• Donor Medical History Review: Conduct comprehensive donor screening using standardized questionnaires to identify risk factors for transmissible diseases.
• Informed Consent: Obtain documented informed consent specifying the use of donated materials for ATMP manufacturing.
• Serological Testing: Perform testing for relevant infectious disease markers using validated methods.
• Nucleic Acid Testing: Conduct NAT for viruses with window period concerns to enhance safety.
• Material Collection: Collect starting materials using aseptic technique with unique donor identifiers.
• Quarantine: Place all collected materials in quarantine until completion and review of all testing.
• Documentation: Maintain complete records of donor eligibility determination, testing results, and material handling.

This protocol must be conducted in compliance with both technical standards and ethical requirements, particularly regarding donor confidentiality and informed consent procedures.

Orthogonal Methods for Quality Attribute Testing

Regulatory authorities increasingly recommend orthogonal testing methods—employing different scientific principles to measure the same attribute—to build confidence in critical quality attributes (CQAs) [12].

Materials and Reagents:

• Cell counting equipment (automated viable cell counter)
• Flow cytometer with appropriate antibodies
• PCR and next-generation sequencing (NGS) platforms
• Sterility testing media kits
• Mycoplasma detection kits
• Endotoxin testing reagents

Procedure for Cell-Based Therapy Characterization:

• Identity Testing:
  • Perform flow cytometry for surface marker characterization
  • Conduct genetic fingerprinting (STR analysis) for autologous products
  • Use orthogonal methods such as qPCR and NGS for vector genome integrity in gene therapies [12]

• Potency Assessment:

  • Implement functional, biologically relevant assays
  • Utilize cell-based bioassays measuring therapeutic mechanism
  • Apply orthogonal methods where feasible to confirm results

• Purity and Safety Testing:

  • Conduct sterility testing per pharmacopoeial methods
  • Perform mycoplasma testing using both culture and indicator cell methods
  • Test for endotoxin using LAL or recombinant methods
  • Measure residual impurities (e.g., cytokines, serum components)

The FDA generally encourages using orthogonal assays to build confidence in CQAs, with this expectation consistent for both Phase 1 IND and later-phase submissions [12]. Similarly, EMA's guidelines for investigational ATMPs state that orthogonal methods should be considered for analytical testing to ensure robustness and reliability of results [12].

Diagram 1: Quality Control Testing Workflow for Starting Materials. This workflow illustrates the sequential testing phases with orthogonal verification as a critical release gate.

The Scientist's Toolkit: Essential Research Reagents and Solutions

Successful management of starting materials requires specialized reagents and systems designed to maintain material integrity throughout the manufacturing process.

Table 3: Essential Research Reagent Solutions for Starting Material Management

Reagent/Solution	Function	Application Notes
Validated Serological Testing Kits	Detection of infectious disease markers	Must have appropriate sensitivity/specificity; require periodic revalidation
Nucleic Acid Testing Platforms	Detection of viral genetic material	Reduces window period risk; essential for donor safety
Automated Cell Counters with Viability Assessment	Quantification of cell number and health	GMP-validated systems provide reproducible results for critical processes
Flow Cytometry Antibody Panels	Characterization of cell surface markers	Multi-color panels enable comprehensive immunophenotyping
Mycoplasma Detection Kits	Screening for mycoplasma contamination	Both culture-based and PCR-based methods recommended as orthogonal approaches
Endotoxin Testing Reagents	Detection of bacterial endotoxins	LAL or recombinant methods must be validated for product type
Cell Culture Media with Defined Components	Ex vivo expansion of cellular materials	Serum-free, xeno-free formulations reduce variability and safety concerns
Cryopreservation Media with Controlled-Rate Freezing Systems	Long-term storage of starting materials	DMSO-containing solutions require validation of post-thaw viability and function

These tools form the foundation of a robust quality control system for starting materials. The selection of appropriate reagents should be guided by phase-appropriate validation requirements, with increased stringency as products move toward commercialization [12].

Analytical Methodologies and Data Interpretation

Phase-Appropriate Analytical Validation

Regulatory authorities apply a "phase-appropriate" lens to analytical method requirements [12]. For early-phase (IND) studies, assays need to be qualified—not yet fully validated—but must be reliable, reproducible, and sensitive enough to support safety decisions [12]. By Phase 3 and into pre-registration stage assets, full validation is required under ICH Q2(R2), including accuracy, precision, specificity, linearity, range, and robustness [12].

Potency assays represent a particularly critical challenge, often cited as the most common Chemistry, Manufacturing, and Controls (CMC) deficiency in CGT programs [12]. The FDA expects functional, biologically relevant assays that adequately demonstrate the biological activity specific to the product's mechanism of action. For cell-based therapies, this may include measures of differentiation potential, secretory profile, or direct cytotoxic activity.

Emerging Technologies in Quality Assessment

Novel technologies are increasingly being incorporated into quality assessment paradigms for ATMP starting materials:

Digital Soft Agar Assays: These more sensitive methods have replaced conventional soft agar colony formation assays for detecting rare transformed cells in therapeutic products, addressing tumorigenicity concerns [15].

Organoid Technology: Provides more accurate models for disease modeling and drug screening, enabling better assessment of starting material functionality [15].

Artificial Intelligence: AI technology helps address monitoring concerns, automation, and data management throughout the manufacturing process [15].

Regulators have demonstrated openness to accepting alternative methods, where feasible and justifiable [12]. The FDA Modernization Act opened the door for New Approach Methodologies (NAMs), such as in silico or organ-on-chip models, to supplement or, in some cases, replace certain in vivo studies [12].

Diagram 2: Emerging Technologies Enhancing Starting Material Quality Control. Novel approaches address specific challenges in ATMP development and safety assessment.

The management of starting materials of human origin for ATMPs requires a sophisticated approach that integrates robust donor tracing systems, comprehensive quality controls, and phase-appropriate analytical validation. The regulatory landscape continues to evolve, with both the EU and US authorities working to adapt requirements to the unique challenges posed by these innovative therapies while maintaining strict standards for patient safety.

Successful navigation of this complex environment demands early and ongoing engagement with regulatory authorities, implementation of orthogonal testing methodologies, and careful attention to emerging technologies that can enhance product characterization. As the field advances, the harmonization of standards and increased regulatory clarity will further support the development of these promising therapies while ensuring the consistent quality and safety of their biological starting materials.

Stability Testing and Setting Shelf-Life for Short-Lived Cell and Gene Therapies

For researchers and drug development professionals working with Advanced Therapy Medicinal Products (ATMPs), stability testing presents unprecedented challenges that diverge significantly from conventional biologics. Short-lived cell and gene therapies, with shelf lives sometimes as brief as 24-72 hours, demand innovative approaches to stability testing and shelf-life determination [37]. Within the European Union's regulatory framework, establishing scientifically justified shelf lives is not merely a technical requirement but a critical component of patient safety and product efficacy. The European Medicines Agency (EMA) emphasizes that ATMP developers must navigate complex legislation covering Good Manufacturing Practice (GMP), Good Clinical Practice (GCP), and Good Laboratory Practice (GLP) requirements throughout medicine development [8].

The inherent biological complexity of these living therapies introduces multiple variables that traditional stability models cannot adequately address. Unlike stable small molecules or even recombinant proteins, cell and gene therapies contain viable biological entities whose critical quality attributes (CQAs)—including viability, phenotype, potency, and functionality—can degrade rapidly and irreversibly [37]. This degradation follows non-linear kinetics that violate assumptions behind classical stability models, necessitating the development of specialized testing protocols that can accurately predict product behavior within compressed timeframes. Understanding these challenges is fundamental to designing robust stability programs that meet EU batch release requirements while ensuring therapeutic performance.

Comparative Analysis: Stability Testing Paradigms

Traditional Biologics vs. Short-Lived Cell and Gene Therapies

Table 1: Comparative Analysis of Stability Testing Requirements

Testing Parameter	Traditional Biologics (ICH Q5C)	Short-Lived Cell & Gene Therapies
Shelf Life	1-5 years (refrigerated/frozen)	24-72 hours (fresh products) [37]
Retest Period	Applicable in some cases	Not applicable - single-use patient-specific doses [37]
Critical Quality Attributes	Protein structure, aggregation, deamidation	Cell viability, phenotype, function, potency [37]
Degradation Kinetics	Linear, predictable	Non-linear, disproportionate to time/temperature [37]
Key Stability Methods	HPLC, CE, spectroscopy	Multi-parametric flow cytometry, metabolic assays, functional response tests [37]
Regulatory Framework	ICH Q5C, established guidelines	Adapting GMP guidelines specific to ATMPs [6]
Container Systems	Standard vials, prefilled syringes	Gas-permeable bags, custom vials, closed-system bioprocessing containers [37]

EU Regulatory Framework for ATMP Stability Testing

The European regulatory environment for ATMP stability testing is evolving rapidly to address the unique challenges posed by these products. The EMA has recognized that conventional stability testing approaches require significant adaptation for ATMPs. Recently, the EMA released a concept paper proposing revisions to Part IV of the EU GMP guidelines specific to ATMPs, aiming to align these guidelines with the revised Annex 1 on sterile medicinal products and incorporate modern quality principles from ICH Q9 and Q10 [6].

The EU regulatory approach acknowledges that real-time stability studies are often impractical for products with extremely short shelf lives, necessitating alternative approaches to establish expiration dates [37]. The legislation provides scientific and financial incentives to encourage ATMP development, including fee reductions of 65-90% for scientific advice and certification procedures [8]. This supportive framework aims to foster innovation while maintaining rigorous standards for product quality and patient safety.

Stability testing under 21 CFR 211.166 is required during all phases of product development, ensuring investigational products maintain acceptable characteristics for proposed clinical studies [37]. However, these regulations were developed primarily for small molecules and recombinant biologics, requiring careful interpretation when applied to cell and gene therapies. The EMA's Committee for Advanced Therapies provides extensive input to develop appropriate guidelines that address the novel and complex manufacturing scenarios utilized for ATMPs [8].

Essential Methodologies for Stability Assessment

Stability-Indicating Assays for Cell and Gene Therapies

Table 2: Stability-Indicating Assays for Cell and Gene Therapies

Assay Category	Specific Methods	Measured Parameters	Applicable Therapy Types
Viability Assessment	7-AAD, Annexin V/PI, dye exclusion assays	Apoptotic progression, membrane integrity, cell death mechanisms	All cell-based therapies [37] [38]
Phenotypic Characterization	Multi-parametric flow cytometry, surface marker analysis	Identity, purity, differentiation status, contaminating populations	CAR-T, TCR, TIL, MSC therapies [37]
Functional Potency	Cytokine release, target cell killing (Chromium-51 release, real-time imaging), calcium flux	Biological activity, mechanism-specific functionality, activation capacity	Immune effector cells (CAR-T, TCR, NK, TIL) [37]
Metabolic Activity	Mitochondrial function assays, metabolic flux analysis	Cellular fitness, energetic status, metabolic adaptation	All viable cell therapies [37]
Proliferation Capacity	CFSE labeling, Ki67 expression, serial division analysis	Replicative potential, expansion capability, durability	Stem cell products, long-lived immune cells [37] [38]
Global Analysis	Gene expression profiling, microRNA analysis	Comparability, consistency, stability indicators	All advanced therapies [38]

Experimental Workflow for Stability Study Design

The diagram below illustrates a comprehensive experimental workflow for designing and executing stability studies for short-lived cell and gene therapies:

Stability Testing Workflow for ATMPs

Analytical Methodologies and Protocols

Post-Thaw Viability and Functional Integrity Assessment

For cell-based therapies, post-thaw viability assessment requires sophisticated approaches that go beyond simple dye exclusion tests. A comprehensive protocol should include:

• Early Apoptosis Detection: Utilize Annexin V in combination with viability dyes (e.g., PI or 7-AAD) to distinguish between early apoptotic, late apoptotic, and necrotic cell populations. This is particularly critical for therapies with delayed-onset cell death phenomena [37].
• Functional Potency Measurements: Implement mechanism-specific functional assays that reflect the intended biological activity. For immune effector cells, this includes:
  • Cytokine Release Assays: Quantify cytokine production (IFN-γ, IL-2, TNF-α) upon target recognition using ELISA or multiplex platforms.
  • Cytotoxic Activity: Measure target cell killing capacity using real-time impedance-based systems or traditional Chromium-51 release assays [37].
• Metabolic Competence: Assess mitochondrial function through assays measuring membrane potential (JC-1, TMRM) or metabolic flux (Seahorse Analyzer) to evaluate cellular fitness beyond mere viability [37].

These multi-parametric approaches are essential because traditional chemical assays are often insufficient to reflect true product stability for cell-based products [37].

Container-Closure and Storage Condition Validation

The selection and validation of appropriate container-closure systems is particularly critical for short-lived therapies. Experimental protocols should address:

• Material Compatibility: Test interactions between cell therapy products and container materials (plasticizers, adhesives) under simulated storage conditions.
• Gas Permeability Studies: Quantify oxygen and CO₂ diffusion through storage bags, as this can significantly impact cell viability and function, especially for metabolically active cell products.
• Thermal Stability Profiling: Establish temperature limits through controlled stress studies that evaluate both immediate and delayed effects on product quality attributes [37].

The EMA's proposed revisions to GMP guidelines for ATMPs emphasize the importance of container-closure systems and provide further clarifications on cleanroom classifications and barrier systems used in ATMP manufacturing [6].

The Scientist's Toolkit: Essential Research Reagent Solutions

Table 3: Research Reagent Solutions for Stability Testing

Reagent Category	Specific Examples	Function & Application	Key Considerations
Specialized Culture Media	T cell therapy culture solutions, NK cell therapy culture solutions, serum-free MSC culture media	Provide consistent environments for cell growth; reduce variability from animal-derived components [37]	Formulation stability; lot-to-lot consistency; growth factor stability
Cryopreservation Systems	GMP-compliant cryopreservation media, DMSO-free cryopreservation media, protein-free freezing media	Enhance cell recovery; maintain viability and function post-thaw; mitigate variability [37]	Cryoprotectant toxicity; compatibility with administration; storage stability
Viability Assessment Tools	7-AAD, Annexin V/PI kits, mitochondrial membrane potential dyes (JC-1, TMRM)	Detect apoptotic and dead cells; assess early indicators of functional decline [37]	Timing of assessment; multiple detection methods; correlation with function
Phenotypic Characterization Reagents	Fluorochrome-conjugated antibodies for flow cytometry, intracellular staining kits	Monitor surface marker expression; verify identity and purity; detect phenotypic drift [37]	Panel design; antibody stability; validation for stability-indicating capacity
Functional Assay Components	Cytokine detection antibodies, target cells for killing assays, activation reagents	Quantify biological activity; measure mechanism-specific potency [37]	Assay linearity; precision; relevance to mechanism of action

Decision Pathway for Shelf-Life Determination

The following diagram outlines a systematic approach for determining appropriate shelf-life for short-lived cell and gene therapies:

Shelf-Life Determination Pathway

Stability testing for short-lived cell and gene therapies requires a paradigm shift from traditional approaches to accommodate their unique biological complexity and compressed shelf lives. The EU regulatory framework is evolving to address these challenges through updated GMP guidelines that incorporate quality risk management principles and adapt to technological advancements in ATMP manufacturing [6]. The successful development of these innovative therapies depends on implementing robust, multi-parametric stability programs that can accurately predict product behavior within clinically relevant timeframes.

Future directions in ATMP stability testing will likely incorporate more real-time monitoring technologies and advanced analytical methods such as global gene expression profiling to enhance predictability of product performance [38]. As regulatory guidance continues to mature, developers should engage early with regulatory bodies through available support mechanisms, including the EMA's innovation task force and scientific advice procedures that offer significant fee reductions for ATMP developers [8]. By adopting scientifically rigorous and regulatory-compliant stability testing frameworks, researchers can ensure that these promising therapies deliver their full potential to patients while meeting the stringent requirements of EU batch release standards.

Addressing Common Challenges in ATMP Batch Release Across Borders

Navigating Multi-Site and Decentralized Manufacturing Authorization

For advanced therapy medicinal products (ATMPs), selecting an appropriate manufacturing authorization model is a critical strategic decision that directly impacts regulatory pathways, batch release requirements, and ultimately, patient access to these innovative treatments. Within the European Union (EU) and United Kingdom (UK), regulatory frameworks have evolved to accommodate both traditional multi-site manufacturing (multiple facilities under a single product license) and the emerging concept of decentralized manufacturing (production at or near the point of patient care) [39] [40]. The fundamental distinction between these models lies in their geographical organization and regulatory oversight mechanisms. Multi-site manufacturing maintains centralized control over quality systems while operating across physically distinct locations, whereas decentralized manufacturing distributes both production and quality oversight activities across healthcare settings to accelerate patient access to therapies with limited shelf lives [39] [41].

The regulatory landscape for these manufacturing approaches is dynamic, with recent developments significantly impacting ATMP batch release requirements. The UK's Medicines and Healthcare products Regulatory Agency (MHRA) has introduced a novel framework for decentralized manufacturing that took effect in July 2025, allowing manufacture at the point of care (POC) and through modular manufacturing (MM) approaches [39]. Simultaneously, the European Medicines Agency (EMA) has proposed revisions to Good Manufacturing Practice (GMP) guidelines specific to ATMPs, aiming to align them with updated Annex 1 requirements and incorporate ICH Q9 (Quality Risk Management) and ICH Q10 (Pharmaceutical Quality System) principles [6]. These regulatory developments reflect a concerted effort to adapt oversight frameworks to the unique challenges posed by ATMPs while maintaining rigorous quality standards.

Comparative Analysis of Authorization Models

The choice between multi-site and decentralized manufacturing authorization models involves distinct regulatory requirements, operational complexities, and batch release implications. The following comparison table summarizes the core differences between these approaches from regulatory and operational perspectives:

Table: Comparative Analysis of Manufacturing Authorization Models

Aspect	Multi-Site Manufacturing	Decentralized Manufacturing
Regulatory Basis	Traditional pathway allowing multiple sites in one license [40]	Emerging framework (UK effective July 2025); EU revisions proposed [39] [6]
Geographical Structure	Multiple fixed facilities under central control	Production at point of care or modular units near patients [39]
Quality Oversight	Centralized Qualified Person (QP) oversight	Distributed oversight with QP maintaining ultimate responsibility [39]
Documentation Requirements	Standard regulatory dossiers for each site (in some regions) [40]	Decentralized Manufacturing Master File (DMMF) with annual reporting [39]
Batch Release Flexibility	Standardized process across sites	Adapted processes for local conditions with maintained oversight [39]
Supply Chain Resilience	High through redundancy of fixed sites	Very high through proximity to patients and reduced transportation [41]

The regulatory framework for multi-site manufacturing, while established, suffers from significant inefficiencies in some regions. As noted in a joint position paper by international pharmaceutical associations, some countries still "issue a new license for each additional manufacturing site," leading to "repeated review of a full dossier" and "a proliferation of additional licenses requiring long-term maintenance" [40]. This fragmented approach ultimately limits supply chain flexibility and can impede patient access to critical medicines.

In contrast, the UK's decentralized manufacturing framework introduces innovative regulatory concepts including the Decentralized Manufacturing Master File (DMMF), which captures "the locations, status of manufacturing sites, contact details, products, processes, and procedures" [39]. This centralized documentation approach allows manufacturers to add or decommission secondary sites without submitting variations to the regulatory authority, though they must "notify the MHRA of any material alteration to the control site or modular units" and provide "annual reporting of updates and changes" [39]. This flexible yet controlled approach represents a significant departure from traditional manufacturing authorization models.

Batch Release Requirements for ATMPs

Qualified Person (QP) Oversight and Responsibilities

Batch release requirements for ATMPs differ significantly between multi-site and decentralized manufacturing models, particularly regarding Qualified Person (QP) responsibilities. In traditional multi-site manufacturing, QP oversight follows established EU guidelines with clearly defined responsibilities for each manufacturing site. The QP ensures each batch complies with marketing authorization and Good Manufacturing Practice (GMP) requirements before release, with standardized procedures across different locations [42].

For decentralized manufacturing, the MHRA's new framework introduces adapted QP responsibilities that maintain rigorous standards while accommodating distributed manufacturing. Although "the Qualified Person (QP) can nominate an individual who is independent of the manufacturing and clinical team of the patient in question to release a POC product," the license holder must comprehensively "demonstrate how they will ensure consistency in the release process and how the process will be reviewed, including how the QP will maintain oversight" [39]. This approach recognizes the practical challenges of point-of-care manufacturing while ensuring maintained quality oversight.

The diagram below illustrates the batch release pathways for both manufacturing models:

Documentation and Traceability Requirements

Comprehensive documentation and robust traceability systems are fundamental to both manufacturing models but implement differently based on operational structures:

• Multi-Site Manufacturing Documentation: Requires complete batch records from each manufacturing site, with clear reconciliation procedures. The EMA emphasizes maintaining "a chronological list of all post-authorisation submission since granting the MA or since the last renewal," including "all approved or pending Type IA/IB and Type II variations, Extensions, Art 61(3) Notifications, USR, and PSURs" [42]. This comprehensive documentation ensures full traceability across all manufacturing sites.

• Decentralized Manufacturing Documentation: Utilizes the Decentralized Manufacturing Master File (DMMF) as the central documentation repository, capturing "the locations, status of manufacturing sites, contact details, products, processes, and procedures" [39]. License holders must "maintain the DMMF and keep it up to date with annual reporting of updates and changes" [39]. For traceability, manufacturers must "demonstrate how they will maintain product and batch traceability" across "several healthcare settings" [39].

GMP Compliance and Control Strategies

Both manufacturing models must comply with GMP requirements, though implementation strategies differ:

• Multi-Site GMP Compliance: Follows established EU GMP guidelines with site-specific compliance verification. Manufacturers must provide "a statement, or when available, a certificate of GMP compliance, not more than three years old, for the manufacturer(s) of the medicinal product" [42]. For active substances, declarations must confirm compliance with detailed guidelines on good manufacturing practice for starting materials [42].

• Decentralized GMP Compliance: The EMA's proposed revisions to Part IV of GMP guidelines specific to ATMPs aim to "incorporate principles from ICH Q9 (Quality Risk Management) and ICH Q10 (Pharmaceutical Quality System)," promoting "a systematic approach to quality risk management" [6]. These revisions also acknowledge "the emergence of new technologies in ATMP manufacturing, such as automated systems, closed single-use systems, and rapid microbiological testing methods" [6], providing adapted GMP frameworks for decentralized approaches.

Experimental Protocols for Batch Release Studies

Protocol 1: Comparative Analysis of Regulatory Frameworks

Objective: To systematically compare batch release requirements for ATMPs across different EU member states and authorization models.

Methodology:

• Regulatory Document Analysis: Comprehensive review of EU regulations, MHRA guidelines, and EMA scientific guidelines pertaining to ATMP batch release [42] [39] [8].
• Stakeholder Interviews: Conduct semi-structured interviews with regulatory affairs professionals (n=15) from ATMP manufacturers utilizing both multi-site and decentralized models.
• Case Study Examination: Analyze 5-7 ATMP case studies with different manufacturing authorization approaches to identify implementation challenges and best practices.

Data Collection:

• Document batch release timelines, documentation requirements, and QP involvement levels for each model.
• Record stakeholder perceptions of regulatory harmonization and implementation barriers.
• Quantify supply chain resilience metrics including time-to-patient and disruption frequency.

Analysis Framework:

• Comparative analysis of regulatory requirements using predetermined coding scheme.
• Thematic analysis of interview transcripts to identify recurring challenges.
• Statistical analysis of batch release efficiency metrics between manufacturing models.

Protocol 2: Quality Control Method Validation

Objective: To validate quality control methods suitable for decentralized manufacturing environments.

Methodology:

• Method Transfer Studies: Execute method transfer protocols between centralized and decentralized sites for critical quality attributes (CQA).
• Environmental Monitoring: Implement comprehensive environmental monitoring programs across decentralized manufacturing units to assess control state.
• Rapid Testing Evaluation: Validate rapid microbiological and potency testing methods suitable for point-of-care manufacturing settings.

Acceptance Criteria:

• Method performance equivalence demonstrated through statistical analysis (p<0.05).
• Environmental monitoring results meeting classified area requirements.
• Rapid method validation meeting ICH Q2(R1) validation parameters.

The Scientist's Toolkit: Research Reagent Solutions

Table: Essential Research Tools for ATMP Manufacturing Authorization Studies

Tool/Reagent	Function in Research	Application Context
Regulatory Document Database	Compilation and analysis of EU, MHRA, and EMA guidelines [42] [39] [8]	Comparative framework development
ICH Q9/Q10 Assessment Tools	Implementation of quality risk management and pharmaceutical quality systems [6]	GMP compliance strategy evaluation
DMMF Template	Standardized documentation for decentralized manufacturing sites [39]	Batch release documentation studies
Case Study Repository	Collection of real-world implementation examples across member states	Regulatory harmonization analysis
Stakeholder Interview Guides	Structured data collection from regulatory professionals	Qualitative research on implementation challenges
Batch Release Tracking System	Monitoring of release timelines and documentation requirements	Efficiency comparison between models

Regulatory Convergence and Future Directions

The regulatory landscape for ATMP manufacturing authorization demonstrates both convergence and ongoing divergence between major jurisdictions. The EMA's recently adopted guideline on clinical-stage ATMPs represents "a credible, if not overly ambitious, effort to consolidate information drawn from over 40 separate guidelines and reflection papers" [23]. This consolidation provides clearer pathways for manufacturers but also highlights persistent differences in implementation approaches between regulatory bodies.

Significant regulatory convergence has occurred in Chemistry, Manufacturing, and Controls (CMC) requirements, with the EMA ATMP guideline organization "mirroring common technical document (CTD) section headings for Module 3" [23]. However, important differences remain in several critical areas:

• Allogeneic Donor Eligibility: The EMA guideline provides "only limited general guidance" regarding donor screening and testing, while "the FDA is more prescriptive in its requirements" [23].
• GMP Compliance Expectations: The EU maintains that "ensuring compliance with GMP requirements is achieved, in part, through mandatory self-inspections," while "the U.S. approach to GMP is through reliance on attestation at the earliest stages of clinical development" [23].
• Potency Testing Requirements: Differing expectations for potency assay validation and implementation continue to present challenges for global ATMP development [23].

Future regulatory developments will likely continue the trend toward harmonization while addressing the unique challenges of decentralized manufacturing. The EMA's proposed GMP revisions and the MHRA's pioneering decentralized manufacturing framework represent significant steps toward regulatory frameworks that balance flexibility with rigorous quality oversight. As these frameworks evolve, batch release requirements for ATMPs will continue to adapt to technological advancements while maintaining fundamental quality standards essential for patient safety.

Managing Supply Chain Logistics for Autologous ATMPs with Short Shelf-Lives

Advanced Therapy Medicinal Products (ATMPs), particularly autologous cell therapies, represent a paradigm shift in medicine, offering the promise of curative, one-time treatments for a range of serious diseases [43]. Unlike traditional pharmaceuticals, autologous ATMPs are patient-specific products manufactured from a patient's own cells, which are harvested, manipulated ex vivo, and then reinfused [43] [44]. This "needle-to-needle" or "vein-to-vein" model creates an exceptionally complex and interdependent supply chain where the product and the patient are inextricably linked [43] [44]. The challenge is magnified for products with very short shelf lives, sometimes measured in hours or days, which demand a perfectly synchronized, just-in-time logistical operation [45]. Within the European Union (EU), this logistical puzzle is further complicated by a regulatory framework that requires robust batch release requirements to ensure patient safety and product efficacy [8] [12]. This guide objectively compares the critical logistical and regulatory elements for managing these advanced therapies, providing a structured analysis for researchers and drug development professionals navigating this challenging field.

Core Logistical Challenges: A Comparative Analysis

The supply chain for autologous ATMPs with short shelf lives differs radically from that of traditional biologics and even other ATMPs. The table below systematically compares these critical logistical attributes.

Table 1: Comparative Analysis of Supply Chain Attributes for Different Therapeutic Products

Feature	Traditional Biologics (e.g., mAbs)	Allogeneic ATMPs ("Off-the-Shelf")	Autologous ATMPs (Short Shelf-Life)
Starting Material	Well-defined API sources [43]	Donor cells from a qualified donor bank [44]	Patient-specific apheresis material; high variability [43]
Batch Size	Single lot = thousands of doses [43]	Single lot = multiple patient doses [44]	Single lot = 1 patient; real-time manufacturing [43]
Traceability	Standard track & trace	Batch-level traceability	Needle-to-needle chain-of-identity required [43]
Shelf Life & Storage	Often refrigerated (2–8°C); stable for months/years [43]	Typically cryopreserved; allows for stockpiling [44]	Very short (hours/days); often fresh or cryopreserved with limited stability [45]
Time Sensitivity	Moderate (drug inventory possible) [43]	Lower; "make-to-stock" model possible [44]	Very tight "just-in-time" windows; zero margin for error [43] [46]
Shipping Model	Established cold chain, pooled shipping [43]	Specialized cryoshippers [44]	"White glove" couriers, 24/7 coverage, active telemetry [43] [46]
Regulatory Focus	Standard GMP track & trace [43]	GMP, donor eligibility, batch release [8]	Chain-of-identity/custody, patient-specific batch release [43] [12]

The Vein-to-Vein Workflow and Critical Control Points

The journey of an autologous ATMP is a linear, sequential process with multiple hand-off points, each representing a potential failure node. The following diagram maps this workflow and its inherent risks.

Diagram 1: Autologous ATMP Vein-to-Vein Workflow and Critical Control Points

The diagram highlights critical control points, particularly in the packaging and shipping phases (red nodes), where the product is most vulnerable to logistical failures. The chain of identity (COI) must be unbroken from apheresis to infusion to ensure the right product is delivered to the right patient [43] [46]. Furthermore, coordinating the manufacturing timeline with the patient's clinical schedule, particularly the lymphodepletion chemotherapy, is a critical path activity; any delay can jeopardize patient health and product viability [43].

Regulatory Framework and Batch Release in the EU

The logistical strategy for an autologous ATMP is deeply intertwined with regulatory requirements for batch release. The EU has a specific framework governed by Regulation (EC) No 1394/2007, with the Committee for Advanced Therapies (CAT) providing scientific evaluation [8] [45].

Comparative Analysis of EU Batch Release Pathways

The EU provides different regulatory pathways, each with distinct implications for logistics and batch release. The following table compares these key routes.

Table 2: Comparison of EU Regulatory Pathways for Autologous ATMPs

Pathway	Centralised Marketing Authorisation	Hospital Exemption (Article 3.7)	Clinical Trial (IMPs)
Scope	Marketing across the entire EU market [47]	Non-routine, custom-made product in a single Member State [47]	Investigational use in approved clinical trials [8]
Batch Release Oversight	Strict GMP, Qualified Person (QP) release mandatory for each batch [8] [12]	National "specific quality standards"; must be equivalent to centralised MA requirements [47]	GMP-compliant IMP manufacture; QP release required [8] [46]
Logistical & Supply Chain Implications	Requires a validated, scalable supply chain capable of multi-country distribution [46]	Highly heterogeneous implementation across Member States; supply chain typically confined to one hospital/country [47]	Phase-appropriate GMP; supply chain must support trial protocol across multiple (potentially multi-national) sites [46]
Key Logistical Challenge	Harmonizing QP release across different countries with potential for border delays [46]	Navigating divergent national interpretations of "non-routine basis" and quality standards [47]	Frontloading EU CTR requirements; defining importer of record and depot strategy early [46]

A pivotal figure in the EU and UK batch release process is the Qualified Person (QP), whose responsibilities are integral to supply chain design. The QP is legally responsible for certifying that each batch of the product has been manufactured and tested in compliance with GMP and the marketing authorization before it is released for use [12] [46]. Best practices strongly advise involving a QP early in the supply chain design stage to ensure that the logistical plan, including shipping lanes, custody transfer points, and conditional "shipment under quarantine" protocols, is defensible from a regulatory standpoint [46].

The Evolving Landscape: Point-of-Care and Modular Manufacturing

Recognizing the immense logistical burden of centralized manufacturing for short shelf-life products, regulators are exploring new frameworks. The UK's MHRA has pioneered a regulatory pathway for Modular Manufacture (MM) and Point-of-Care (POC) manufacturing, effective July 2025 [3]. This model allows for the final manufacturing or assembly steps to occur at a hospital or clinic (the modular unit) under the supervision and control of a central manufacturing license holder. Critically, product release is performed at the central site, not the bedside, which can significantly streamline the process for short shelf-life products [3]. The following diagram illustrates this new model.

Diagram 2: MHRA's Modular/Point-of-Care Manufacturing and Batch Release Model

Experimental Protocols and Methodologies for Logistics Validation

Validating the supply chain for a short shelf-life autologous ATMP requires a rigorous, data-driven approach. The following methodologies are critical for de-risking logistics and supporting regulatory submissions.

Shipping Lane Qualification Protocol

Objective: To demonstrate that a specific shipping route (from manufacturing site to clinical center) can maintain the product's critical quality attributes (CQAs), such as viability and potency, within the specified shelf life.

Methodology:

• Mock Shipments: Execute a minimum of three consecutive successful mock shipments using surrogate materials (e.g., cell media, non-investigational cells) that mimic the product's physical and thermal characteristics.
• Instrumentation: Equip shipments with calibrated temperature data loggers (and, if applicable, vibration and shock loggers) placed within the product's primary container to monitor conditions in real-time [43] [44].
• Stress Testing: Expose shipments to worst-case scenario conditions, including extended transit times, extreme ambient temperatures, and potential layovers [44].
• Pre- and Post-Shipment Testing: Analyze surrogate products for key CQAs (e.g., cell viability, sterility, potency) before and after the shipment to quantify any impact of transport.

Rapid Sterility Testing (for Fresh Products)

Objective: To enable a conditional "ship-to-quarantine" and rapid release model for products with shelf lives shorter than the standard 14-day sterility test.

Methodology:

• Technology Implementation: Employ rapid microbiological methods (RMM) such as flow cytometry, isothermal microcalorimetry, or nucleic acid amplification techniques, which can provide results in 24-48 hours [46].
• Validation: Validate the RMM against the compendial sterility method per Ph. Eur. 2.6.1, demonstrating equivalent or superior sensitivity and specificity.
• Release Strategy: Define a risk-based release protocol in the quality agreement where the QP can release the product for infusion based on a negative rapid sterility result, with the understanding that the batch will be quarantined and recalled if the compendial method later returns a positive result [46].

The Scientist's Toolkit: Key Reagents and Solutions for Supply Chain Management

Beyond biological reagents, managing this supply chain requires a suite of specialized tools and technologies.

Table 3: Essential Research Reagent Solutions for ATMP Supply Chain Logistics

Tool/Solution	Function & Application	Experimental Consideration
Cryopreservation Agents (e.g., DMSO)	Protects cells from ice crystal formation during freezing and storage at ultra-low temperatures (e.g., -150°C to -196°C) [43].	DMSO toxicity to cells and patients requires careful optimization of concentration and washing steps; controlled-rate freezing is critical [43].
Cryogenic Shipper Qualification	Validated shipping containers that maintain stable ultra-low temperatures using dry ice or liquid nitrogen vapor phase [43] [44].	Performance Qualification (PQ) must simulate real transport stresses; label adhesion and legibility at cryogenic temperatures are critical [44].
IoT & Telemetry Sensors	GPS and continuous temperature monitoring devices that provide real-time data on shipment location and conditions [43] [46].	Data must be accessible to case managers and QPs; alert thresholds for temperature excursions must be defined and validated [46].
Orchestration Platform Software	Digital systems that coordinate the entire vein-to-vein process, tracking chain-of-identity and synchronizing all stakeholders [43] [46].	Platforms must be validated per GMP data integrity standards (ALCOA+); ensure interoperability between hospital, manufacturer, and courier systems [43].
Rapid Mycoplasma Assay	Molecular-based assays (e.g., PCR) that provide mycoplasma testing results in hours instead of the 28-day culture method.	Essential for conditional release of fresh products; requires full validation to demonstrate sensitivity over the culture method [15].

The successful management of supply chain logistics for autologous ATMPs with short shelf-lives hinges on a fully integrated strategy where logistical design and regulatory batch release requirements are developed in parallel. As the field evolves, regulatory innovation, such as the MHRA's POC framework, and technological advances in rapid testing and real-time monitoring offer promising pathways to simplify these complex operations. The key to success lies in early and deep collaboration between developers, logistics experts, and regulators, particularly the Qualified Person, to build supply chains that are not only robust and reliable but also agile enough to ensure these transformative therapies can reach the patients who need them in a timely and safe manner.

Overcoming Variability in Biological Starting Materials and Process Validation

Advanced Therapy Medicinal Products (ATMPs), encompassing cell and gene therapies, represent a frontier in medical treatment but face significant challenges due to the inherent variability of biological systems. Unlike traditional small-molecule drugs manufactured through reproducible chemical synthesis, biologics are produced using living systems, making it impossible to guarantee that each batch will be identical to the last [48]. This variability originates from multiple sources, including the biological nature of starting materials, complex manufacturing processes, and the sensitive analytical methods required for quality control [49] [50].

For ATMPs classified as medicinal products in the European Union, regulatory approval requires demonstration of quality, safety, and efficacy through controlled manufacturing processes and comprehensive analytical testing [51]. The critical quality attributes (CQAs) of ATMPs are determined not only by manufacturing process inputs such as starting and raw materials but also by how the manufacturing process itself is designed and controlled [51]. This article examines the sources of variability in biological starting materials and manufacturing processes, compares strategies for controlling this variability, and provides detailed experimental methodologies for ensuring consistent product quality within the context of EU batch release requirements.

Biological Variation and Raw Materials

Biological variation represents the most significant source of process variability according to industry assessments, with raw materials and consumables constituting a close second [49]. This variability occurs because bioprocesses utilize highly complex living organisms with millions of biochemical pathways that can introduce product variants. For example, during development of a recombinant protein malaria vaccine, the number of product variants resulting from O-linked mannosylation was considerably reduced by overexpression of a chaperone protein called PDI [49]. Glycosylation patterns can significantly influence therapeutic efficacy, as mannosylation can trigger more rapid clearance of proteins from a patient's body, thereby reducing therapeutic effect [49].

The European Medicines Agency (EMA) requires GMP-grade manufacturing of investigational medicinal products for first-in-human studies, emphasizing that ex vivo genome editing machinery be defined as starting materials [12]. This requirement has disappointed many developers who had requested a risk-based analysis and potential classification as a raw material that would allow for manufacturing outside of GMP principles [12]. The inherent complexity of biologics is evident when comparing molecular sizes: while a small molecule drug like aspirin consists of as few as 21 atoms, biologics can be made of over 25,000 atoms [48].

Operational and Environmental Factors

Operational inputs—including measurements, methods, personnel, and equipment—represent significant sources of variation derived from how bioprocesses are operated within facilities [49]. Industry surveys indicate that approximately one in five respondents identified operational influences as the major risk to achieving product critical quality attributes [49]. Automation strategies can reduce this variability; for instance, automating bioreactor feeds can minimize errors from multiple operator-involved steps and enable more data capture for process analysis [49].

Environmental factors, while considered less influential than in classical pharmaceutical manufacturing, still contribute to overall variation. Some biological operations must be performed within specific temperature parameters to maximize product stability, and variations within these ranges can affect product quality [49]. Microbial contamination from the environment represents a potentially batch-terminating event, though few biologics manufacturers claim sterile processing, and a degree of bioburden is tolerated within downstream processes [49].

Figure 1: Sources of Process Variation in ATMP Manufacturing. This diagram categorizes the primary sources of variability that impact Critical Quality Attributes (CQAs) of Advanced Therapy Medicinal Products, highlighting biological factors as the predominant concern according to industry surveys [49].

Regulatory Framework and Batch Release Requirements

EU vs US Regulatory Approaches

The regulatory approaches to ATMPs in the European Union and United States show both overlaps and notable differences. In the EU, ATMPs fall under four sub-types: gene therapy medicinal product (GTMP), somatic cell therapy medicinal product (sCTMP), tissue engineered product (TEP), and combined ATMP (cATMP) [12]. Under current legislation, the EU is much more precise in its delineation of GTMPs than the U.S., though new EU pharmaceutical legislation will bring important changes, including redefining GTMP to include genome editing techniques and synthetic nucleic acids [12].

In the US, cellular and gene therapies serve as the umbrella category with human gene therapies and somatic cell therapies nested underneath, with no separate category for TEPs [12]. For classification uncertainty, the EU Committee for Advanced Therapies (CAT) provides recommendations, while in the US, companies can engage with the Office of Therapeutic Products (OTP) under CBER that regulates all CGTs [12]. A significant difference emerges for combination products: in the EU, if a product is a combination of a cell and gene therapy, such as CAR-T cells, it is always classified as a gene therapy, whereas the US approach may differ [12].

Evolving EU Regulatory Landscape

The EU regulatory landscape for ATMPs continues to evolve with significant legislative changes. The revised pharmaceutical legislation introduces Article 56a, which enables member states to require a marketing authorization holder (MAH) to make a product available in sufficient quantities to cover the needs of patients in that country [12]. This could be problematic for ATMPs due to their storage and logistics requirements, particularly for personalized therapies for rare diseases that must be manufactured close to the site of care and administered within hours of completion of manufacturing [12].

The EU Substances of Human Origin (SoHO) legislation, revised in 2024, brings blood products, tissues and cells under one regulation to provide greater protection to patients and donors [12]. The updated legislation extends activities covered to include donor registration, collection and testing, as well as storage, distribution, import, and export, significantly impacting ATMP developers as all parties handling any of the SoHO activities must comply with the new regulation by 7 August 2027 [12].

Table 1: Comparison of EU and US Regulatory Approaches to ATMPs/CGTs

Regulatory Aspect	European Union (ATMPs)	United States (CGTs)
Product Categories	Gene therapy (GTMP), Somatic cell therapy (sCTMP), Tissue engineered (TEP), Combined ATMP [12]	Cellular and gene therapies umbrella, with human gene therapies and somatic cell therapies nested underneath [12]
Classification Body	Committee for Advanced Therapies (CAT) [12]	Office of Therapeutic Products (OTP) under CBER [12]
Combination Products	Always classified as gene therapy (e.g., CAR-T cells) [12]	Handled by Office of Combination Products with 60-day designation process [12]
Starting Material Requirements	GMP grade required for first-in-human studies; ex vivo genome editing machinery defined as starting materials [12]	Higher quality input materials than for early phase small molecules; no research grade excipients or starting materials [12]
GMP Certification for Import	EU GMP certification required with qualified persons (QP) for batch release [12]	FDA compliance required for US manufacturing

Analytical Control Strategies

Potency Assay Development and Variability Control

Potency testing represents a legal requirement for lot release testing of biologics, providing a quantitative measure of a drug's intended biological activity through its mechanism of action (MoA) [50]. These assays face significant variability challenges due to the inherent variability of experimental biological systems and their product-specific nature, which typically requires development from "scratch" as part of CMC drug development activities [50]. Unlike compendial methods, potency assays benefit less from multi-company improvement across years and international standardization that aim to increase measurement consistency and reduce variability [50].

The experimental design of potency methods is inherently linked to the variability of the final assay format. Intra-assay variability is often controlled through replication strategies, using multiple dilution series within an assay run that are combined to form a model fit, allowing more precise measurement and helping control sample preparation errors [50]. A critical consideration is selecting an appropriate number of assay runs for the derivation of reportable potency values, which can either come from one valid assay run or be averaged over multiple % relative potency (%RP) values from different assay runs [50].

Regulators have demonstrated openness to accepting alternative methods where feasible and justifiable [12]. The FDA generally encourages using orthogonal assays—methods using different scientific principles to measure the same attribute—to build confidence in critical quality attributes (CQAs) [12]. For example, identity, potency, and purity assays in gene therapy programs often require at least two complementary methods, such as qPCR and next generation sequencing (NGS) for vector genome integrity, or infectivity assay in addition to copy number assessment [12].

Phase-Appropriate Assay Validation

A phase-appropriate approach to assay validation is essential throughout the product development lifecycle. For early-phase (IND) applications, assays need to be qualified but must be reliable, reproducible, and sensitive enough to support safety decisions [12]. By Phase 3 and into pre-registration stage assets, full validation is required under ICH Q2(R2), including accuracy, precision, specificity, linearity, range, and robustness [12]. Potency assays are often singled out as the most common CMC deficiency in CGT programs, with FDA expecting functional, biologically relevant assays [12].

EMA's guidelines for investigational ATMPs (effective July 2025) specifically state that orthogonal methods should be considered for analytical testing to ensure the robustness and reliability of results related to product quality, particularly when reference standards, validated methods, or standardized assays are lacking [12]. This guideline aligns with the broader move toward regulatory convergence with the FDA in analytical and comparability principles [12]. For clinical trial materials, validated analytical methods are encouraged but not strictly required for early phases; orthogonal testing bolsters confidence in the data when full validation isn't feasible [12].

Table 2: Potency Assay Variability Management Throughout Product Lifecycle

Development Stage	Assay Status	Key Variability Control Activities	Typical Acceptance Criteria
Preclinical	Assay Development	Prequalification runs; AQbD implementation; DoE for optimal parameters [50]	Internal quality targets met across chosen range [50]
Phase 1 (FTIH)	Assay Qualification	First formal variability assessment; supports IND/CTA filings [50]	Platform acceptance criteria based on similar products [50]
Phase 2	Method Refinement	Process consistency expectations; refining critical process parameters [12]	Tightening specifications; phase-appropriate validation [12]
Phase 3	Method Validation	Full GMP compliance; validation per ICH Q2(R2) [12] [50]	Actual manufacturing process and method performance data [50]
Commercial	Continued Verification	Ongoing trending during commercial lot testing [50]	Based on PPQ, clinical experience, and validation data [50]

Process Validation Methodologies

Risk-Based Validation Approaches

The manufacturing process validation of products used in clinical investigation is a regulatory requirement, with production needing to be prospectively validated to confirm the suitability of the product for its intended use [52]. Effective validation must be designed to include all key components that define product manufacturing consistency, reliability, product quality, and data accuracy [52]. For ATMPs, a risk-based approach provides manufacturers with the flexibility necessary to adapt the best controls to the process while ensuring all requirements and critical aspects are met [53].

The International Society for Pharmaceutical Engineering (ISPE) emphasizes that risk-based approaches help understand what's critical to product quality, patient safety, and product variability [53]. This understanding enables focus on those elements to ensure a safe manufactured product, preventing wasted resources, inefficient operations, or products failing to reach market [53]. The phase-appropriate validation strategy adapts the level of rigor and documentation based on development stage, establishing an effective control strategy to navigate the complexities of ATMP validation [53].

Key recently released regulations crucial for ATMP risk-based validation include PIC/S Annex 2A (Manufacture of Advanced Therapy Medicinal Products for Human Use), PIC/S Annex 1 (Manufacture of Sterile Medicinal Products), and ICH Q9(R1) Quality Risk Management [53]. These frameworks guide manufacturers in implementing comprehensive risk-based validation strategies across the ATMP product lifecycle, facilitating regulatory compliance while fostering innovation in the field [53].

Mixing Validation and Process Control

In biopharmaceutical manufacturing, validation of solution-mixing processes plays a vital role in ensuring drug-product quality and regulatory compliance [54]. For biologics as complex, multicomponent solutions, successful production hinges on consistently homogeneous mixing, as variations can diminish product efficacy, stability, and safety [54]. Mixing-time studies determine the time needed to achieve a homogeneous solution, which is crucial for maintaining uniform product quality and efficacy [54].

The matrix and bracketing approaches enable optimization of mixing validation across different solution formulations, aiming to identify and validate worst-case scenarios while streamlining the validation process [54]. The matrix approach involves testing a representative subset of variable combinations, such as batch sizes, agitator speeds, and tank geometries, to understand their impact on mixing efficiency [54]. The bracketing approach focuses on testing extremes of key variables, such as the smallest and largest batch sizes and the lowest and highest agitator speeds, under the assumption that intermediate conditions will perform consistently [54].

For establishing homogeneity acceptance criteria, either individual study results must maintain a relative standard deviation (RSD) within ≤5.0%, or all individual values must remain within ±10.0% of the average [54]. When measurements are reported near the lower end of the measurement range, absolute values are applied to validate the required precision for achieving homogeneity [54]. Monitoring at least one critical parameter related to mixing (such as turbidity, conductivity, pH, or osmolarity) is recommended to ensure that a process remains within acceptable limits [54].

Figure 2: Risk-Based Process Validation Workflow. This diagram outlines the systematic approach to validating manufacturing processes for ATMPs, incorporating matrix and bracketing methods to efficiently establish controlled processes while maintaining regulatory compliance [54] [53].

Experimental Protocols and Research Toolkit

Potency Assay Variability Estimation Protocol

Objective: To quantify potency assay variability and determine the appropriate number of assay runs needed to achieve reportable results with acceptable out-of-specification (OOS) rates [50].

Materials and Equipment:

• Reference Standard (RS): Well-characterized drug lot of known potency [50]
• Test samples: Manufactured lots to be tested for potency
• Cell lines or biological systems relevant to drug mechanism of action [50]
• Laboratory equipment: Plate readers, pipettes, sterile workstations
• Data analysis software: Suitable for linear mixed models and parallelism testing [50]

Methodology:

• Assay Design: Implement a replication strategy with multiple dilution series within each assay run. Prepare independent dilution series for both RS and test samples to control sample preparation errors [50].
• Experimental Execution: Perform valid assay runs as defined in method SOP, ensuring system suitability criteria are met, including parallelism testing between RS and assay control [50].
• Data Collection: For each valid run, collect dose-response data and calculate % relative potency (%RP) using appropriate model fits (e.g., 4-parameter logistic fit) [50].
• Variability Analysis:
  • Use linear mixed models to estimate different sources of variability (within-run, between-run, operator-to-operator) [50]
  • Calculate variance components and total variability for reportable results
  • Determine the relationship between number of runs and OOS rates under given specifications [50]
• Reportable Value Determination: Establish the number of assay runs needed for reportable values based on variability estimates and acceptable OOS rates [50].

Data Analysis: The relative measurement of potency against an RS helps control intra-lab (day-to-day and analyst-to-analyst) and interlab assay variability [50]. The fundamental assumption of parallelism must be met for meaningful derivation of %RP in a standardized and reproducible manner [50]. The number of assay runs should be selected to control the accuracy and precision of the assay results for sample testings [50].

Mixing Validation Protocol Using Matrix Approach

Objective: To validate mixing processes across different manufacturing scales and conditions using a matrix approach to efficiently establish worst-case scenarios [54].

Materials and Equipment:

• Manufacturing tanks of various scales and geometries
• Solutions representing formulation extremes
• Monitoring equipment: pH meters, conductivity meters, turbidimeters
• Data collection system for continuous parameter monitoring

Methodology:

• Tank Identification: List all tanks used throughout the biomanufacturing process [54].
• Solution Grouping: Organize the solutions prepared in each tank, treating each preparation as a condition within the group [54].
• Comprehensive Risk Assessment:
  • Evaluate mixing hydrodynamics: Analyze mixing dynamics for grouped conditions and assign risk scores related to solution solubility [54]
  • Assess solution properties: Evaluate intrinsic properties of each solution and assign risk scores based on maximum solubility of multicomponent solution, powder-particle size, and ingredient immiscibility [54]
  • Calculate overall risk: Derive an overall score by combining risk factors: (mixing hydrodynamics) × (solution maximum solubility) × (particle size) × (chemical complexity and ionic strength) [54]
• Critical Condition Testing: Validate the most critical conditions to ensure mixing performance is controlled effectively across all tank sizes and configurations [54].

Acceptance Criteria: Homogeneity is demonstrated when at least three consecutive samples show consistent agreement within acceptable variability in the measured parameter [54]. For normally distributed parameters, a sample size calculation at 90% confidence and 80% reliability with a detectability (Δ/σ) value of 1.0 yields a sample size of three [54]. Either individual study results must maintain a relative standard deviation (RSD) within ≤5.0%, or all individual values must remain within ±10.0% of the average [54].

Table 3: Research Reagent Solutions for Variability Control Studies

Reagent/Category	Function	Key Specifications	Variability Control Application
Reference Standard (RS)	Well-characterized drug lot for relative potency measurement [50]	Known potency; fully characterized	Serves as benchmark for test sample comparison in potency assays [50]
Cell Lines for Bioassays	Biological systems for functional potency assessment [50]	Consistent response characteristics; appropriate for mechanism of action	Enable biologically relevant potency measurements [12]
Engineering Parameters	Normalized metrics for mixing assessment (P/V, Fr, tblend) [54]	Calculated from equipment specifications and operating conditions	Facilitate comparison of mixing dynamics across scales [54]
Orthogonal Assays	Multiple methods measuring same attribute via different principles [12]	qPCR, NGS, infectivity, copy number assessment	Build confidence in critical quality attributes (CQAs) [12]
Risk Assessment Tools	Framework for evaluating process variability sources [53]	Based on ICH Q9(R1) Quality Risk Management	Support risk-based validation strategies [53]

Overcoming variability in biological starting materials and process validation requires a multifaceted approach integrating rigorous analytical controls, risk-based process validation, and adherence to evolving regulatory frameworks. The inherent variability of biological systems necessitates sophisticated control strategies, including orthogonal analytical methods, phase-appropriate assay validation, and comprehensive process characterization. The EU regulatory landscape for ATMPs continues to evolve, with emphasis on harmonized standards and risk-based approaches that ensure product quality while fostering innovation.

Successful navigation of these challenges enables the development of safe and effective ATMPs that meet stringent batch release requirements. By implementing robust control strategies throughout the product lifecycle—from early development through commercial manufacturing—developers can mitigate variability risks while maintaining regulatory compliance. The experimental protocols and methodologies outlined provide a framework for addressing variability challenges, contributing to the broader goal of ensuring consistent product quality for these transformative therapies.

Research Reagent Solutions for ATMP Process Comparability Studies

Reagent / Material	Function in Experimental Protocol
Orthogonal Assays	Provides two or more analytical methods based on different scientific principles to measure the same Critical Quality Attribute (CQA), such as identity or potency, ensuring robust and reliable results [12].
Functional Potency Assays	Measures the biologically relevant activity of the product, which is critical for demonstrating product efficacy and is a key expectation of regulatory agencies [12].
Genome Editing Machinery	For genetically modified ATMPs, these components (e.g., CRISPR-Cas systems) are defined as starting materials and must be manufactured to GMP grade for clinical trials [12].
GMP-Grade Starting Materials	All input materials, including cells, vectors, and excipients, must be qualified and of GMP quality to ensure patient safety and product consistency, even in early-phase trials [12].
Closed-System Automated Platforms	Integrated, automated manufacturing technologies that minimize human intervention and process variability, enabling consistent production across multiple decentralized sites [55].

Comparison of GMP Standards: Centralized vs. Point-of-Care Manufacturing

Feature	Centralized Manufacturing Facility	Point-of-Care (POC) Manufacturing
Regulatory Model	Single-site, centralized oversight by a national Competent Authority [55].	"Hub and spoke" or "Control Site" model, where a central site oversees a network of POC sites [56] [55].
Facility Structure	Dedicated, large-scale GMP facility with traditional cleanrooms [55].	Multiple, smaller sites; often uses closed-system, automated technologies or deployable units ("GMP-in-a-box") in hospital settings [55].
Batch Certification & Release	A single Qualified Person (QP) certifies each batch for release before distribution, per EU GMP Annex 16 [57] [34].	The Control Site's QP maintains oversight. For POC products administered immediately, certain labeling may be waived, but GMP compliance is mandatory [58] [55].
Supply Chain & Logistics	Complex and lengthy, involving shipment of cryopreserved products, which can delay patient treatment [55].	Simplified and localized, enabling delivery of fresh products with very short shelf-lives and reducing logistics burden [58] [55].
Process Validation & Comparability	Focus on process consistency and validation within a single facility and equipment train [55].	Paramount to demonstrate product comparability and process consistency across all decentralized manufacturing sites in the network [58] [55].
Key Regulatory Guidance (EU)	Well-established under EudraLex Volume 4 and EMA guidelines [34].	Evolving framework; MHRA published a new, tailored framework in 2025, while the EU is still developing specific provisions [58] [55].

Regulatory Frameworks and Oversight Models

Centralized Manufacturing

The European Medicines Agency (EMA) centrally authorizes all ATMPs, and the Committee for Advanced Therapies (CAT) is pivotal in their scientific assessment [13]. The foundational GMP requirements are outlined in EudraLex Volume 4, with Annex 16 providing specific guidance on certification by a Qualified Person (QP) and batch release [57] [34]. In this model, a single QP at a licensed manufacturing site bears the legal responsibility for certifying that each batch complies with its marketing authorization and GMP standards before it is released for distribution [57].

Point-of-Care Manufacturing

The UK's Medicines and Healthcare products Regulatory Agency (MHRA) has been a pioneer, establishing the first comprehensive regulatory framework for POC manufacturing in 2025 [58] [55]. This framework introduces two new license types: a Manufacturer's License for Modular Manufacturing (MM) and a Manufacturer's License for Point of Care (POC) [55].

The core of this new model is the "Control Site" concept. This licensed site acts as the central regulatory nexus, responsible for the overall quality system and overseeing all POC manufacturing sites within the network [58] [55]. The Control Site holds the "POC Master File" (or Decentralized Manufacturing Master File, DMMF) as the main source of information for the manufacturing process and is the primary point of contact for regulatory authorities [56] [58]. This model shifts some oversight responsibilities from the regulator to the licensed manufacturer, requiring a system of robust audits and quality agreements between the Control Site and each POC location [58].

Diagram 1: Regulatory oversight model for POC manufacturing. The Competent Authority directly supervises the Control Site and may inspect any POC site, while the Control Site provides continuous oversight of the entire network.

Batch Release and QP Certification Requirements

Centralized Batch Release

In centralized manufacturing, batch release is a definitive, centralized event. A named Qualified Person (QP) at the Manufacturing Importation Authorisation (MIA) holder's site must certify each batch. This certification is based on a full review of the manufacturing and testing records from all sites involved in the production chain, ensuring compliance with GMP and the product's marketing authorization [57] [34]. The entire supply chain, from active substance starting materials to the finished product, must be established and verified [34].

POC Batch Release

The POC model introduces flexibility but maintains the requirement for rigorous quality oversight. The QP at the Control Site carries the overall responsibility for the quality system and product release [55]. For products with an extremely short shelf-life that are administered immediately after manufacture (within minutes), the MHRA guidance allows for exemptions from certain labeling requirements after manufacture but encourages pre-labeling of containers [58]. However, this does not diminish the fundamental GMP and quality review obligations. The integrity of the chain of identity and the electronic batch record is critical for traceability in a recall situation [55].

Diagram 2: Batch release workflow comparison. Centralized manufacturing relies on a single QP certification event, while POC manufacturing depends on continuous system oversight by the Control Site QP and immediate product administration.

Experimental Protocols for Demonstrating Process Comparability

A cornerstone of the POC manufacturing model is demonstrating that the product is comparable regardless of where it is made within the network. The following methodology is critical for regulatory submissions.

Objective: To demonstrate that ATMPs manufactured across multiple decentralized POC sites are comparable in terms of critical quality attributes (CQAs) to those produced at the central or lead manufacturing site.

1. Protocol Design:

• Site Selection: Include the central control site and a representative sample of POC manufacturing sites. The number should be justified statistically to represent the network's variability [55].
• Sample Material: Use a common, well-characterized cell source (allogeneic) or simulate the autologous process using standardized, representative donor material [55].
• Study Arms: Manufacture multiple batches (n≥3 per site) using the identical, validated process and the same platform technology (e.g., closed-system automated bioreactors) at all sites [55].

2. Analytical Methods:

• Orthogonal Testing: Employ at least two complementary analytical methods based on different scientific principles to measure key CQAs. For example, use both qPCR and next-generation sequencing (NGS) to assess vector genome integrity in gene therapies [12].
• Potency Assays: The potency assay must be a functional, biologically relevant method that reflects the product's mechanism of action. This is often a key focus area for regulators [12].
• Method Suitability: Ensure analytical methods are qualified (for early phase) or fully validated (for commercial phase) per ICH Q2(R2) and are comparable across all testing sites [12] [55].

3. Data Analysis:

• Statistical Power: Pre-define acceptance criteria for comparability based on process capability and clinical experience. Use statistical models (e.g., equivalence testing, analysis of variance (ANOVA)) to demonstrate that inter-site variability is no greater than intra-site variability [55].
• CQA Assessment: Compare all relevant CQAs, including identity, purity, potency, viability, and sterility, across all study arms to conclude on product comparability [58] [55].

The regulatory landscape for ATMP manufacturing is evolving to accommodate innovative POC models. While centralized manufacturing operates under a well-established, single-site QP certification model, POC manufacturing relies on a networked "Control Site" structure with overarching QP oversight. The successful implementation of a POC strategy hinges on a robust QMS, the use of closed-system automated technologies, and, most critically, the rigorous demonstration of process comparability across all manufacturing sites. Regulatory agencies like the MHRA are leading this transition with tailored frameworks, offering a pathway to improve the accessibility and scalability of these transformative therapies.

Utilizing the EudraGMDP Database for Compliance Verification and Inspection Planning

For researchers and drug development professionals working with Advanced Therapy Medicinal Products (ATMPs), the EudraGMDP database serves as a critical regulatory tool for compliance verification and inspection planning. Maintained by the European Medicines Agency (EMA), this community database provides essential information on manufacturing, import, and wholesale distribution authorisations, along with Good Manufacturing Practice (GMP) and Good Distribution Practice (GDP) certificates [59]. For ATMPs, which include gene therapies, somatic-cell therapies, and tissue-engineered products, compliance with EU GMP standards is mandatory for both marketed products and investigational medicinal products used in clinical trials [2]. The database aims to improve information sharing between regulators and the public, aid in coordinating inspections of manufacturers in third countries, and facilitate verification of legitimate actors in the medicine distribution chain [59].

Comparative Analysis of Database Verification Capabilities

The EudraGMDP database provides distinct verification mechanisms for different aspects of the ATMP supply chain. The table below summarizes the key compliance documents accessible through the database and their specific relevance to ATMP development.

Table 1: Key Compliance Documents in the EudraGMDP Database for ATMP Verification

Document Type	Scope of Verification	Relevance to ATMP Development
GMP Certificate	Confirms a manufacturer complies with Good Manufacturing Practice principles [60].	Essential for ATMP manufacturers as specific GMP guidelines apply [2] [16].
Manufacturing and Importation Authorisation (MIA)	Authorizes the manufacture or import of medicinal products in the EU [60].	Required for any company manufacturing or importing ATMPs within the EU market [2].
GDP Certificate	Confirms a wholesale distributor complies with Good Distribution Practice [60].	Crucial for ensuring the integrity of the ATMP supply chain, especially for temperature-sensitive products.
Statement of Non-Compliance	Indicates a manufacturer does not comply with GMP/GDP standards [60].	Allows researchers to identify and avoid non-compliant facilities for sourcing materials or manufacturing.
Registration of Active Substance Manufacturers	Records manufacturers, importers, and distributors of active substances [60].	Important for verifying the quality of starting materials, which for ATMPs include substances of human origin [6].

Methodological Framework for Database Utilization

Experimental Protocol for Compliance Verification

A systematic approach to using the EudraGMDP database ensures comprehensive compliance verification for ATMP research and development. The following protocol outlines a standardized methodology:

• Organization Identification: Confirm the organization's details are correctly recorded in EMA's Organisation Management Service (OMS), as this is a prerequisite for applications since January 2022 [59].

• Certificate Verification: Search the public EudraGMDP database using the organization name or location to retrieve valid GMP/GDP certificates, manufacturing authorisations, and statements of non-compliance [60].

• Inspection History Analysis: Review the historical data for repeated inspections, identified deficiencies, and the scope of authorized manufacturing activities relevant to ATMPs.

• Cross-Border Compliance Checking: For international research collaborations, verify mutual recognition agreements with third-country authorities, which facilitate information sharing in the database [59].

• Regulatory Alignment Confirmation: For ATMP-specific manufacturing, confirm that the GMP certificate references compliance with Part IV of Eudralex Volume 4, which contains the specific GMP guidelines for ATMPs [16].

Workflow for ATMP Compliance Verification

The following diagram illustrates the logical workflow for utilizing the EudraGMDP database in ATMP compliance verification and inspection planning:

Table 2: Key Research Reagent Solutions for ATMP Regulatory Compliance

Resource	Function	Application in ATMP Research
EudraGMDP Database	Public database for verifying GMP/GDP compliance of manufacturers and distributors [59] [60].	Core tool for due diligence on manufacturing partners and suppliers for ATMP development.
EMA's Organisation Management Service (OMS)	Master database for organization-related details [59].	Prerequisite step before EudraGMDP searches; ensures correct entity identification.
EudraLex Volume 4, Part IV	Specific GMP guidelines for Advanced Therapy Medicinal Products [16].	Reference standard for ATMP-specific manufacturing quality requirements.
ICH Q9 (Quality Risk Management)	Quality risk management principles to be incorporated in updated ATMP guidelines [6].	Framework for risk-based approaches to ATMP manufacturing and quality control.
EMA/CAT Classification Procedure	Procedure for determining ATMP classification [13] [26].	Formal process to confirm regulatory status of borderline products.

Emerging Regulatory Developments in ATMP Compliance

The regulatory landscape for ATMPs is continuously evolving. In May 2025, EMA released a concept paper proposing revisions to Part IV of the EU GMP guidelines specific to ATMPs [6]. These revisions aim to align ATMP-specific GMP requirements with the updated Annex 1 on sterile medicinal products, incorporate principles from ICH Q9 (Quality Risk Management) and ICH Q10 (Pharmaceutical Quality System), and provide clarifications on new technologies in ATMP manufacturing [6]. Furthermore, new legislation on substances of human origin (SoHOs) revised in 2024 will require all parties handling these starting materials to comply with updated standards by August 2027 [26]. These developments highlight the importance of continuous monitoring of regulatory databases like EudraGMDP for maintaining compliance in ATMP research and development.

For ATMP researchers, regular consultation of the EudraGMDP database provides critical intelligence for selecting compliant manufacturing partners, planning regulatory inspections, and ensuring the integrity of the ATMP supply chain from early development through commercial distribution.

Comparative Analysis of National Implementation and Best Practices

Comparing Expectations of National Competent Authorities in Key Member States

The regulatory landscape for Advanced Therapy Medicinal Products (ATMPs) in the European Union is characterized by a dual-layer structure. While marketing authorization for industrially produced ATMPs is centralized through the European Medicines Agency (EMA), the implementation of specific pathways, including batch release requirements, often falls to National Competent Authorities (NCAs) [47]. This decentralized execution, particularly for pathways like the hospital exemption, has resulted in a heterogeneous regulatory environment across member states [47] [24]. For researchers and drug development professionals, understanding these national nuances is critical for planning clinical development and market access strategies. This guide objectively compares the expectations of NCAs in key member states, focusing on batch release and related regulatory requirements for ATMPs. The comparison is framed within a broader thesis on ATMP batch release, synthesizing information on national-level implementation of EU regulations to highlight points of convergence and divergence.

Comparative Analysis of National Regulatory Pathways

The following sections and tables summarize the regulatory frameworks and batch release requirements for ATMPs in selected EU member states and the UK, which has established distinct regulations post-Brexit.

Table 1: Overview of Key National ATMP Regulatory Pathways and Responsible Authorities

Member State / Country	National Competent Authority (NCA)	Key National Pathway(s)	Legal Basis / Guidance
European Union (General)	European Medicines Agency (EMA); National Competent Authorities of Member States	Centralised Marketing Authorisation; Hospital Exemption (HE)	Regulation (EC) No 1394/2007; Directive 2001/83/EC, Article 3(7) [47]
Germany	Paul-Ehrlich-Institut (PEI)	Authorisation of non-routinely manufactured ATMPs ($4b AMG)	German Medicines Act (Arzneimittelgesetz - AMG), Section 4b [61]
United Kingdom	Medicines and Healthcare products Regulatory Agency (MHRA)	Modular Manufacture (MM); Point of Care (POC) Manufacture	The Human Medicines (Amendment) (Modular Manufacture and Point of Care) Regulations 2025 [3] [62]
Italy	Agenzia Italiana del Farmaco (AIFA)	Hospital Exemption (HE)	National implementation of EU ATMP Regulation [63]
Spain	Agencia Española de Medicamentos y Productos Sanitarios (AEMPS)	Hospital Exemption (HE)	National implementation of EU ATMP Regulation [47]
Belgium	Federal Agency for Medicines and Health Products (FAMHP)	Hospital Exemption (HE)	National implementation of EU ATMP Regulation [24]

Table 2: Comparison of Batch Release and Key Manufacturing Requirements

Member State / Country	Batch Release Location & Supervision	Fees for National Pathway Approval	Key Requirements for National Pathways
Germany ($4b AMG)	Not explicitly specified; under responsibility of the approval holder.	€4,250 to €17,000, depending on procedure scope [61]	- Submission of modules based on CTD format [61]- Proof of permits for collection/manufacturing [61]- Pharmacovigilance system proportionate to scale [61]
United Kingdom (MM/POC)	Control Site (holds manufacturer's licence). Batch is released at the main manufacturing site, not at the POC/MM site [3] [62].	Standard MHRA fees apply (specifics not detailed in sources)	- Manufacturer's Licence (MM/POC) and Master File for each product [62]- POC/MM sites specified in licence and master file [62]- Licence holder supervises and controls all sites [3]
Hospital Exemption (e.g., Italy, Spain, Belgium)	Within the approved hospital/manufacturing site, under professional responsibility of a medical practitioner [47].	Varies by Member State; Germany's fee structure (above) is one example.	- Non-routine preparation and custom-made for individual patient [47]- National GMP authorisation [47]- Traceability & pharmacovigilance equivalent to centrally authorised ATMPs [47]- Highly heterogeneous interpretation of requirements across member states [47] [24]

Key Insights from the Comparative Analysis

• Fundamental Model Difference: The UK's new Modular and Point of Care framework introduces a fundamentally different batch release model. It centralizes responsibility and batch release at a licensed "control site," which supervises distributed manufacturing units via a master file system [3] [62]. In contrast, the EU's Hospital Exemption and Germany's §4b AMG pathway typically envision batch release and full responsibility residing within the individual hospital or manufacturing unit where the product is prepared [47] [61].

• Regulatory Heterogeneity in the EU: The implementation of the Hospital Exemption across EU member states is highly heterogeneous. Critical concepts like "non-routine basis" and "custom-made product" lack a unified definition in EU binding law, leading to varying interpretations at the national level [47]. This results in differences in the upper limit of patients treated, duration of approval, and evidentiary requirements for approval [47] [24].

• Data Reporting and Use: A significant challenge lies in the interplay between nationally regulated exempted ATMPs and centrally authorized ATMPs. There are conflicting views among regulators on whether data generated under a Hospital Exemption can be used to support a subsequent centralized marketing authorization application, adding uncertainty for developers [47].

Experimental Protocols for Regulatory Compliance

To generate the data required for submissions to NCAs, developers must implement robust experimental protocols. The following workflows and methodologies are critical for demonstrating product quality, safety, and efficacy.

Protocol 1: Orthogonal Analytical Method Validation for Critical Quality Attributes (CQAs)

Objective: To establish and validate multiple independent analytical methods for measuring the same Critical Quality Attribute (CQA) of an ATMP, building confidence in the reliability of quality control data submitted to regulators [12].

Methodology:

Workflow Description: The process begins with the identification of CQAs such as identity, potency, and purity [12]. A primary analytical method is selected (e.g., qPCR for vector copy number in gene therapy), followed by the development of an orthogonal method based on a different scientific principle (e.g., next-generation sequencing for vector genome integrity) [12]. Both methods undergo rigorous qualification assessing precision, sensitivity, and linearity. The level of validation is phase-appropriate, moving from qualified assays in early phases to full validation according to ICH Q2(R2) guidelines by the pre-registration stage [12]. All data and procedures are thoroughly documented in the Chemistry, Manufacturing, and Controls (CMC) section of the regulatory submission.

Protocol 2: Quality Control Strategy for Point-of-Care and Modular Manufacture

Objective: To implement a quality control strategy suitable for ATMPs manufactured in a decentralized model (e.g., UK's POC/MM framework), where final product assembly may occur at multiple satellite sites.

Methodology:

Workflow Description: This protocol aligns with the UK's MHRA framework for Modular and Point-of-Care manufacture [3] [62]. A central Control Site, which holds the Manufacturer's Licence (MM or POC), creates and maintains a product-specific Master File detailing all manufacturing and assembly arrangements. This Master File is followed by all satellite Modular or POC Sites. The satellite sites conduct in-process testing and generate quality control data, which is transmitted to the Control Site. The batch release decision, however, is made exclusively at the Control Site based on the consolidated data, ensuring centralized quality oversight despite decentralized manufacturing activities [3].

The Scientist's Toolkit: Essential Reagents and Materials

The development and quality control of ATMPs require specialized reagents and materials. The following table details key solutions used in the field.

Table 3: Key Research Reagent Solutions for ATMP Development and QC Testing

Reagent / Material Category	Specific Examples	Function & Application in ATMP Development
Cell Culture Media & Supplements	Serum-free media, cytokines, growth factors, GMP-grade FBS	Ex vivo expansion and differentiation of somatic cells for cell therapy products (e.g., CAR-T cells, chondrocytes) [24].
Gene Editing Machinery	CRISPR/Cas9 systems, TALENs, mRNA for gene insertion, viral vectors	Genetic modification of cells for Gene Therapy Medicinal Products (GTMPs). Defined as a starting material by EMA, requiring high quality [12].
Analytical Assay Reagents	qPCR probes/primer sets, NGS libraries, flow cytometry antibodies, ELISA kits	Used in orthogonal methods for characterizing CQAs like identity, potency (biological activity), purity, and vector copy number [12].
GMP-Grade Starting Materials	Plasmid DNA, cytokines, separation beads, apoptosis inducers	Critical raw materials used in the manufacturing process. Regulators do not allow research-grade materials; higher quality input materials are expected even in early phases compared to small molecules [12].
Substances of Human Origin (SoHO)	Patient or donor-derived cells (e.g., leukapheresis material), tissues	The primary active substance for many ATMPs. Their collection and testing must comply with EU SoHO legislation and relevant directives, ensuring donor safety and traceability [12] [8].

This comparison guide reveals a dynamic and diverse regulatory environment for ATMP batch release across key European markets. The central tension lies between the EU's Hospital Exemption, characterized by its necessary flexibility but significant national heterogeneity, and the UK's newly established Modular and Point of Care framework, which offers a structured, centralized-control model for decentralized manufacturing. For drug development professionals, these differences are not merely administrative. They fundamentally influence clinical trial design, manufacturing network planning, and regulatory strategy. Success in this landscape requires early and proactive engagement with the relevant National Competent Authorities to understand their specific interpretations and expectations, ensuring that innovative therapies can navigate these complex pathways to reach patients in need.

Advanced Therapy Medicinal Products (ATMPs), encompassing gene therapies, cell therapies, and tissue-engineered products, represent a groundbreaking class of medicines within the European Union (EU). Their inherent complexity and personalized nature, particularly for autologous therapies, present unique challenges for manufacturing and quality control. The batch release process is a critical regulatory requirement designed to ensure that every batch of a medicine released to the market meets the established standards of quality, safety, and efficacy. For ATMPs, this process must be adapted to address product-specific characteristics, such as short shelf lives, patient-specific manufacturing, and complex modes of action. This guide provides a comparative analysis of the batch release strategies for two pioneering ATMPs: Strimvelis, an ex vivo gene therapy for ADA-SCID, and Zalmoxis, an allogeneic T-cell therapy. By examining their regulatory pathways, quality controls, and post-approval monitoring, this article aims to elucidate the specific considerations for ATMP batch release within the context of EU regulatory frameworks, offering a vital resource for researchers and drug development professionals.

Strimvelis (Autologous CD34+ Cell-Based Gene Therapy for ADA-SCID)

Strimvelis is the first ex vivo gene therapy to receive marketing authorization in the EU. It is indicated for the treatment of severe combined immunodeficiency due to adenosine deaminase deficiency (ADA-SCID), a rare and life-threatening genetic disorder [64] [65]. The therapy is an autologous product, meaning it is manufactured using the patient's own cells. Specifically, a sample of the patient's bone marrow is collected, and CD34+ cells (hematopoietic stem and progenitor cells) are isolated and genetically modified ex vivo using a gamma-retroviral vector to insert a functional copy of the human ADA gene [66] [67]. The modified cells are then infused back into the patient after a conditioning regimen with busulfan. Once engrafted, these cells are capable of producing functional ADA enzyme, leading to sustained immune reconstitution [65].

Zalmoxis (Allogeneic T-Cell Therapy for Hematological Disorders)

Zalmoxis was an allogeneic, genetically modified T-cell therapy that received conditional marketing authorization (CMA) in the EU. It was developed as an adjunctive treatment for haploidentical hematopoietic stem cell transplantation (HSCT) in adult patients with high-risk hematological malignancies [68]. The product consisted of T cells from a matched donor that were genetically modified with a retroviral vector encoding a suicide gene. This suicide gene allowed for the controlled elimination of the donor T cells in case of adverse events, such as graft-versus-host disease (GvHD) [68]. Despite its innovative approach, Zalmoxis was withdrawn from the market in October 2019 after unfavorable results from a required post-approval Phase III clinical trial, which is a stipulated condition for medicines authorized under CMA [68].

Table 1: Fundamental Characteristics of Strimvelis and Zalmoxis

Feature	Strimvelis	Zalmoxis
Therapeutic Category	Ex vivo gene therapy	Somatic cell therapy
Cell Source	Autologous (patient's own cells)	Allogeneic (donor cells)
Genetic Modification	Yes (gamma-retroviral vector with ADA cDNA)	Yes (retroviral vector with suicide gene)
Therapeutic Indication	ADA-SCID	Adjunctive treatment after HSCT for hematological malignancies
Marketing Status in EU	Approved (2016)	Withdrawn (2019)

Comparative Analysis of Regulatory Pathways and Evidence

The journey from development to market authorization for Strimvelis and Zalmoxis highlights divergent regulatory pathways and evidence requirements within the EU. Strimvelis was developed through a successful public-private partnership involving the San Raffaele Telethon Institute for Gene Therapy (SR-Tiget), Fondazione Telethon, and GlaxoSmithKline (GSK), and later sold to Orchard Therapeutics [64] [67]. Its approval was based on data from a single main study involving 12 children with ADA-SCID, which demonstrated a 100% survival rate at three years and sustained immune reconstitution [66] [65]. The product was granted orphan medicine designation and received a standard marketing authorization.

In contrast, Zalmoxis was granted a Conditional Marketing Authorization (CMA). This pathway is applicable to medicines that address unmet medical needs and whose benefits of immediate availability outweigh the risks inherent in the fact that comprehensive clinical data are not yet available [68]. Consequently, approval is granted on the condition that the company fulfills specific obligations, such as completing ongoing or new clinical trials to confirm the product's benefit-risk profile. The withdrawal of Zalmoxis following unfavorable results in its post-approval Phase III trial underscores the risks associated with this regulatory pathway and the critical importance of fulfilling these obligations [68].

A comparative study of regulatory submissions found that ATMPs, as a category, often display critical deficiencies in submitted clinical data at the time of application compared to more established biologicals [68]. To mitigate this, regulators may employ flexibility, particularly in assessing non-clinical data. However, this is often balanced by imposing more post-approval commitments, which can add pressure on the product's market performance post-launch.

Table 2: Regulatory Pathways and Evidence for Authorization

Aspect	Strimvelis	Zalmoxis
Regulatory Pathway	Standard Marketing Authorization	Conditional Marketing Authorization (CMA)
Orphan Designation	Yes [66]	Information not specified in search results
Key Evidence for Approval	Single study, 12 patients, 100% survival at 3 years, long-term follow-up (~7 years) [66] [65]	Evidence met the bar for CMA but required confirmatory trial
Post-Authorization Measures	Registry for long-term safety monitoring (insertional mutagenesis, efficacy) [66]	Required completion of Phase III clinical trial
Market Outcome	Currently marketed (licensed in several European countries) [67]	Withdrawn in 2019 due to unfavorable Phase III results [68]

Batch Release Requirements and Quality Control

The batch release of ATMPs in the EU is a rigorous process governed by Good Manufacturing Practice (GMP) guidelines tailored specifically for ATMPs [69]. A cornerstone of this process is the certification by a Qualified Person (QP), as outlined in EU GMP Annex 16 [57]. The QP is responsible for ensuring that each batch has been manufactured and tested in compliance with the marketing authorization and GMP standards before it is released for use.

For a product like Strimvelis, the autologous and patient-specific nature dictates a highly individualized batch release strategy. Each patient's treatment constitutes a single batch. The manufacturing process begins with the collection of the patient's bone marrow. The CD34+ cells are then purified and transduced with the retroviral vector encoding the ADA gene [65] [67]. Given the short shelf life of the final product, the entire process, from cell collection to infusion, operates under a tightly controlled and expedited timeline [67].

Quality control for Strimvelis involves a suite of in-process and release tests. These likely include, but are not limited to, viability and potency assays, tests to confirm the identity and purity of the CD34+ cell population, and quantification of vector copy number to ensure successful genetic modification. Furthermore, stringent testing for sterility (bacterial and fungal) and freedom from mycoplasma and endotoxins is critical to ensure patient safety [69]. The use of a gammaretroviral vector necessitates specific safety testing, such as replication-competent retrovirus (RCR) assays, to ensure the viral vector has not regained the ability to replicate [65].

While detailed public specifications for Zalmoxis's batch release are limited, as an allogeneic product, it would have been manufactured in larger, more defined batches from donor cells, unlike the single-patient batches for Strimvelis. This allows for a different approach to scale-out and quality control. Its release criteria would similarly have included assessments of cell viability, potency, identity, and sterility, with additional specific tests to verify the functionality of the suicide gene system.

Diagram 1: Strimvelis manufacturing and release workflow.

The Scientist's Toolkit: Key Reagents and Materials

The development, manufacturing, and quality control of ATMPs like Strimvelis and Zalmoxis rely on a specialized set of reagents and materials. The following table details some of the core components essential for such advanced therapies.

Table 3: Key Research Reagent Solutions for ATMP Development

Reagent/Material	Function in ATMP Development & Manufacturing
Retroviral Vector (Gamma-retroviral)	A genetically disabled virus used as a vehicle to deliver and insert a therapeutic gene (e.g., ADA cDNA) into the genome of target cells (e.g., CD34+ cells) [65] [67].
CD34+ Cell Selection Reagents	Antibodies and magnetic bead-based kits for the positive selection and purification of hematopoietic stem and progenitor cells from a heterogeneous cell sample like bone marrow or apheresis product [67].
Cell Culture Media & Cytokines	Specialized, often serum-free, media formulations supplemented with growth factors (e.g., SCF, TPO, FLT3-L) to support the survival, expansion, and maintenance of stem cells during the ex vivo manufacturing process [67].
Replication-Competent Retrovirus (RCR) Assay	A critical safety testing kit used to detect the presence of replication-competent virus in the final product, ensuring the genetic modification process has not generated a replicative and potentially harmful virus [65].
Flow Cytometry Reagents	Antibodies and viability dyes used for quality control tests to confirm cell identity (e.g., CD34+ purity), viability, and potency throughout the manufacturing process [69].

The case studies of Strimvelis and Zalmoxis provide critical insights into the dynamic and demanding landscape of ATMP batch release in the EU. Strimvelis demonstrates a successful model of academia-industry partnership leading to a standardized, albeit patient-specific, manufacturing and release process for an autologous gene therapy, supported by robust long-term follow-up to manage theoretical risks [64] [65]. In contrast, the trajectory of Zalmoxis highlights the challenges associated with the Conditional Marketing Authorization pathway, where initial approval based on promising but incomplete data must be followed by confirmatory evidence, failing which market withdrawal is a tangible outcome [68].

A key differentiator in their regulatory journeys was the sufficiency of clinical evidence at the time of authorization. The compelling, long-term data from Strimvelis's pivotal trial supported a full authorization, while the evidence for Zalmoxis met the threshold for a conditional approval, which carried inherent risks [68]. For researchers and developers, these cases underscore the necessity of engaging with regulatory bodies like the EMA early and often, through protocols like the PRIority MEdicines (PRIME) scheme, to align on evidence requirements [65]. Furthermore, they emphasize that a successful batch release strategy is not merely a final step but is integrated into the entire product lifecycle, from process design and GMP compliance to post-marketing pharmacovigilance. As the ATMP field continues to evolve with next-generation technologies, the lessons learned from these pioneering therapies will be invaluable in shaping efficient, safe, and effective regulatory pathways for the curative medicines of the future.

Advanced Therapy Medicinal Products (ATMPs), which include gene therapies, somatic cell therapies, and tissue-engineered products, represent a frontier in medical innovation for treating diseases with limited therapeutic options [70]. The unique nature of these products, often characterized by complex manufacturing processes and personalized applications, necessitates specialized regulatory frameworks for Good Manufacturing Practice (GMP). Two significant regulatory approaches have emerged: the European Medicines Agency's (EMA) EudraLex Volume 4, Part IV and the Pharmaceutical Inspection Co-operation Scheme's (PIC/S) Annex 2A [71] [72]. This analysis examines the critical divergence between these frameworks, with a specific focus on implications for batch release requirements within EU member states and for researchers and drug development professionals navigating this complex landscape.

The core structural difference lies in their regulatory architecture. The EMA established Part IV as a standalone GMP guide specifically for ATMPs, published on 22 November 2017 (enforced 22 May 2018) [71]. In contrast, PIC/S elected to maintain ATMP guidance within its Annex structure, creating a separate Annex 2A for ATMPs that took effect on 1 February 2022, while explicitly stating that all other applicable PIC/S Annexes, such as Annex 1 for sterile manufacturing, still apply to ATMPs [71] [72]. This fundamental difference in approach—comprehensive standalone document versus integrated annex—explains why the EMA's Part IV is almost double the length (88 pages) of the PIC/S Annex 2A (49 pages) and creates significant ripple effects on technical requirements [71].

Comparative Analysis of Key Regulatory Divergences

The following table summarizes the principal differences between the two regulatory frameworks, which are critical for researchers to understand when designing manufacturing and testing processes.

Table 1: Core GMP Requirement Comparison between PIC/S Annex 2A and EMA Part IV

GMP Requirement / Approach	PIC/S Annex 2A	EMA Part IV	Implications for Batch Release
Regulatory Structure	Integrated with other PIC/S Annexes (e.g., Annex 1) [71]	Standalone guideline [71] [73]	PIC/S requires compliance with a broader set of standards, complicating the compliance landscape.
Quality Risk Management (QRM)	Referenced throughout but no dedicated section [71]	Extensive information, including risk-based manufacturing environmental controls [71]	EMA allows more flexible, risk-based environmental controls for early-phase trials, potentially facilitating batch release for complex cases.
Contamination Control Strategy (CCS)	Explicitly required [71]	Not explicitly referenced in available data	CCS is a foundational element for batch contamination assessment in the PIC/S framework.
Grade D 'In Operation' Particulate Monitoring	Not required [71]	Requires risk assessment to determine necessity [71]	Directly impacts environmental monitoring protocols and data required for batch release decisions.
Manufacturing in Grade A with Grade C Background	Not referenced [71]	Permitted for early-phase trials for life-threatening conditions [71]	EMA provides regulatory flexibility for exceptional clinical circumstances, affecting the validation data for batch release.

Analysis of Divergence Impact on ATMP Development

The divergence in regulatory philosophy has tangible consequences. The EMA's standalone Part IV, while comprehensive, suffers from a lack of integration with the evolving broader EU GMP framework, including significant revisions to Annex 1 and the incorporation of modern quality concepts like those in ICH Q9 and Q10 [73]. This has prompted the EMA to issue a Concept Paper in May 2025 proposing a revision of Part IV, largely to address this very issue [73]. The PIC/S approach, by contrast, automatically benefits from updates to other annexes, promoting a more harmonized and current regulatory practice [73].

Furthermore, the EMA's explicit allowance for manufacturing a critical Grade A area within a Grade C background for very early-phase trials addressing life-threatening conditions with no alternatives provides a crucial flexibility pathway for innovators [71]. This risk-based concession, absent from PIC/S Annex 2A, can accelerate proof-of-concept trials by simplifying facility requirements. Conversely, PIC/S Annex 2A offers superior clarity on the types of ATMPs within its scope, using illustrative tables and figures, whereas this information is located in a separate EMA Q&A document, making it less accessible for developers [71].

Implications for Batch Release of ATMPs

The regulatory divergence directly impacts the responsibilities of the Qualified Person (QP) in batch release. A core requirement for releasing batches of ATMPs imported into the EU from third countries is that each batch must be re-tested within the EU unless a specific exemption is granted [22]. The European Medicines Agency (EMA) has clarified that such an exemption can only be considered under two stringent conditions:

• For a limited quantity of available material.
• For a product with a very short shelf life [22].

Crucially, the exemption is contingent upon the product being tested in a GMP-certified facility in a third country that has a relevant Mutual Recognition Agreement (MRA) or equivalent agreement with the EU [22]. This creates a complex interface between the specific ATMP GMP rules (Part IV or Annex 2A) and general importation regulations, requiring deep regulatory awareness from QPs and researchers. The application for an exemption must be submitted to the EMA's Committee for Advanced Therapies (CAT) during the marketing authorization evaluation process, highlighting the need for early strategic planning [22].

Experimental Workflow for Batch Release Testing

The following diagram illustrates the critical decision pathway for batch release, particularly concerning imported ATMPs, integrating the requirements from both regulatory frameworks and the possibility of exemption.

Diagram 1: Batch release workflow for ATMPs, detailing the exemption process for imports.

Essential Research Reagents and Materials for Compliance

Navigating the regulatory requirements for batch release necessitates specific materials and documentation. The following table outlines key components of the "Regulatory Toolkit" for ensuring compliance.

Table 2: Essential Research Reagents and Documentation for ATMP Batch Release

Item / Reagent	Function / Purpose in Compliance	Regulatory Consideration
Reference Standards & Cells	Critical for analytical method validation, calibration, and batch potency testing.	Must be qualified and traceable. Stability data is required for short-lived materials [22].
Validated Assay Kits	Used for safety testing (e.g., sterility, mycoplasma, endotoxin) and identity/potency assays.	Method transfer and validation between third country and EU sites must be flawless for exemption applications [22].
GMP Certificate (MRA Country)	Documentary evidence to support waiver of re-testing for imported batches.	Must be issued by an EEA authority relevant to the specific testing category [22].
Stability Data Package	Justifies the proposed shelf life, a key factor for exemption due to short shelf life.	Data must be generated under specified storage conditions and included in the marketing application [22].
Contamination Control Strategy (CCS)	A proactive plan to assess control strategies for microbial and particulate contamination.	A required document under PIC/S Annex 2A, crucial for overall quality assessment prior to release [71].
Quality Risk Management (QRM)	A systematic process for identification, risk assessment, and control of product quality risks.	Heavily emphasized in EMA Part IV, enabling flexible approaches like risk-based environmental monitoring [71].

The analysis confirms that while there are no fundamental conflicts between PIC/S Annex 2A and EMA Part IV, the strategic divergences in structure, risk-based flexibility, and specific technical requirements are significant [71]. For researchers and drug development professionals, the choice of regulatory pathway has direct implications on manufacturing strategy, facility design, and the evidence package required for batch release. The EMA's more explicit risk-based approach, as seen in the flexibility for early-phase trials, can facilitate development agility. In contrast, the PIC/S framework offers greater harmonization and clarity through its integrated structure.

The regulatory landscape is dynamic. The EMA's proposed revision of Part IV, initiated in May 2025, is a clear move to address the shortcomings of its standalone model and better align with evolving GMP concepts [73]. Furthermore, the broader context of UK-EU regulatory divergence shows a trend towards UK alignment with EU rules in areas of manufactured goods, which could influence the long-term acceptance of batch testing data between these regions [74] [75]. For professionals in the field, continuous monitoring of these developments is not merely beneficial but essential for the efficient and compliant advancement of transformative advanced therapies to patients.

The Impact of ICH Q5A (R2) on Viral Safety and Clearance Strategies for ATMPs

The International Council for Harmonisation (ICH) Q5A(R2) guideline, titled "Viral Safety Evaluation of Biotechnology Products Derived from Cell Lines of Human or Animal Origin," represents a critical update to global regulatory standards, finalised in early 2024 [76]. This revision provides a risk-based framework for assuring the viral safety of biotechnology products, outlining the necessary data for marketing applications [76]. For Advanced Therapy Medicinal Products (ATMPs), including gene therapies, somatic cell therapies, and tissue-engineered products, this guideline is particularly transformative. It addresses the unique challenges posed by these innovative treatments, which often involve complex biological materials like viral vectors and living cells, introducing new risks of adventitious agent contamination [77].

The updated guideline maintains the foundational, three-tiered viral safety strategy of: (1) selecting and testing cell lines and other raw materials for the absence of viral agents; (2) testing the product at appropriate manufacturing steps for infectious viruses; and (3) evaluating the capacity of the production process to clear infectious viruses [78] [79]. However, ICH Q5A(R2) introduces substantial additions that reflect over two decades of scientific and manufacturing advances. Most significantly for ATMP developers, it now explicitly includes guidance for viral-vector-based products used in gene therapies and vaccines, and addresses continuous manufacturing processes, thereby providing a modernised framework for viral safety that aligns with current state-of-the-art approaches in the ATMP field [77] [79].

Comparative Analysis of Viral Safety Strategies: Pre- and Post-ICH Q5A (R2)

Key Changes Introduced by ICH Q5A (R2) for ATMPs

The evolution from the previous guideline to ICH Q5A(R2) has substantially shifted the viral safety landscape for ATMPs. The table below systematically compares the core approaches before and after this update, highlighting the critical advancements.

Table 1: Comparison of Viral Safety Strategies for ATMPs Pre- and Post-ICH Q5A(R2)

Aspect	Pre-Q5A(R2) Era (Primarily ICH Q5A(R1))	Post-Q5A(R2) Era (Current Approach)
Scope & Applicability	Primarily focused on traditional biotech products (e.g., recombinant proteins from CHO cells) [77].	Explicitly includes viral vectors (e.g., AAV), viral-vector-derived products, and cell-based production platforms used for ATMPs [77] [79].
Testing Regimen	Testing of Master Cell Banks (MCBs), Working Cell Banks (WCBs), and bulk harvest [78].	Expanded to include testing of viral seeds, cells at the limit of in vitro cell age (LIVCA), and the drug substance for helper viruses and replication-competent particles [77] [79].
Viral Clearance Studies	Expected for traditional biologics; expectations for labile vectors were less clear [77].	Clarifies expectations for viral clearance steps for vectors (e.g., AAV) where feasible without compromising product efficacy [77].
Analytical Methods	Reliance on in vivo assays (e.g., MAP, HAP) and in vitro cell culture assays [79].	Encourages advanced methods like Next-Generation Sequencing (NGS) to replace certain in vivo assays, aligning with the 3Rs principles [79].
Manufacturing Paradigms	Guidance based on batch manufacturing processes.	Introduces specific viral safety considerations for Continuous Manufacturing (CM), addressing monitoring, detection, and clearance in dynamic systems [77] [79].
Use of Prior Knowledge	Limited formal recognition.	Explicitly allows the use of Prior Knowledge (PrK) for modular validation and resin-reuse studies, potentially reducing product-specific validation efforts [79].

Detailed Methodologies for Viral Safety Evaluation under ICH Q5A (R2)

The successful implementation of ICH Q5A(R2) relies on robust and well-defined experimental protocols. Below are the detailed methodologies for key activities mandated by the guideline for ATMPs.

Protocol for Testing Cell Banks, Viral Seeds, and Bulk Harvest

This protocol is designed to detect a wide spectrum of viral contaminants, including adventitious, endogenous, and specific viruses related to viral vector systems [77] [79].

• Sample Collection: Aseptically collect representative samples from the Master Cell Bank (MCB), Working Cell Bank (WCB), cells at the Limit of In Vitro Cell Age (LIVCA), viral seeds, unprocessed bulk harvest, and drug substance [79].
• In Vitro Assay for Adventitious Viruses:
  • Procedure: Inoculate the test sample onto a panel of mammalian cell lines (e.g., Vero, MRC-5, HEK 293) chosen for their susceptibility to a broad range of human and animal viral pathogens. Include a positive control (e.g., Vesicular Stomatitis Virus - VSV) and a negative control (uninoculated cells).
  • Incubation & Observation: Incubate the cultures for 14-28 days and observe regularly for cytopathic effects (CPE), hemadsorption, or hemagglutination.
  • Interpretation: The appearance of CPE or other viral effects in the test sample indicates a positive result for adventitious viruses.
• In Vivo Assay for Adventitious Viruses (or NGS Alternative):
  • Traditional In Vivo Procedure: Inoculate the test sample into adult mice, suckling mice, and embryonated eggs. Observe animals for signs of illness or death; examine eggs for viability and lesions.
  • NGS-Based Replacement [79]: Extract total nucleic acids (DNA and RNA) from the test sample. Prepare sequencing libraries and perform high-throughput sequencing on an NGS platform. Analyse the resulting data using a validated bioinformatics pipeline to detect sequences from known and unexpected viral agents.
  • Interpretation: The guideline now encourages the use of fully validated NGS methods as a replacement for the in vivo assay, reducing animal use and potentially increasing detection sensitivity [79].
• Tests for Retroviruses and Specific Contaminants:
  • Reverse Transcriptase (RT) Assay or Product-Enhanced RT (PERT) Assay: Detect retroviral contamination by measuring RT activity.
  • Transmission Electron Microscopy (TEM): Used to characterise and quantify retrovirus-like particles in cell lines.
  • Species-Specific Tests: For insect cell lines, perform PCR or other NATs to detect specific contaminants like insect rhabdovirus [79].

Protocol for Viral Clearance Validation Studies

Viral clearance studies demonstrate the capability of the manufacturing process to remove and/or inactivate potential viral contaminants [79].

• Study Design:
  • Scale-Down Model: Establish a validated small-scale model that accurately represents the manufacturing-scale unit operation.
  • Model Virus Selection: Select a panel of model viruses with diverse physicochemical properties (size, genome type, envelope) that represent potential contaminants. For viral vectors, this includes viruses representing adventitious agents, endogenous viruses, and relevant helper viruses [79]. Examples include:
    • Murine Leukemia Virus (MuLV): Model for endogenous retroviruses.
    • Parvovirus (e.g., MMV or PPV): Model for small, non-enveloped viruses.
    • Vesicular Stomatitis Virus (VSV): Model for large, enveloped RNA viruses.
• Spiking and Processing:
  • Virus Spike Preparation: Prepare a high-titer stock of the model virus.
  • Spiking: Add ("spike") a known amount of virus into the process intermediate (e.g., clarified harvest) at the beginning of the unit operation. The spike volume should be small (≤10%) to avoid altering the product's properties.
  • Processing: Run the scaled-down unit operation following established manufacturing parameters.
• Titration and Calculation:
  • Titration: Assay the virus titer in the pre-spike material, the spiked starting material, and the processed material using a plaque assay, 50% tissue culture infectious dose (TCID₅₀), or other validated method.
  • Log Reduction Value (LRV) Calculation: Calculate the LRV for the step using the formula:
    • LRV = Log₁₀ (V₁ × T₁ / V₂ × T₂)
    • Where V₁ is the volume of the spiked starting material, T₁ is the titer of the spiked starting material, V₂ is the volume of the processed material, and T₂ is the titer of the processed material.
• Virus Reduction Steps:
  • Low-pH Inactivation: Hold the spiked product at a defined acidic pH (e.g., pH 3.5-3.9) for a specified time (e.g., 30-60 minutes) at a controlled temperature.
  • Solvent/Detergent (S/D) Treatment: Incubate the spiked product with a specific combination of solvent (e.g., Tri-n-butyl phosphate - TNBP) and detergent (e.g., Triton X-100 or Polysorbate 80) for a defined time and temperature.
  • Virus Filtration: Pass the spiked product through a dedicated virus filter (e.g., parvovirus or retrovirus filter). The post-use filter must pass an integrity test.
  • Chromatography: Evaluate the viral clearance across chromatographic steps (e.g., AEX, CEX, affinity). Fractions are collected and assayed for virus titer.

The following workflow synthesizes the core viral safety strategy for ATMPs as outlined in ICH Q5A(R2), integrating both testing and clearance evaluation.

Diagram 1: ICH Q5A(R2) Viral Safety Evaluation Workflow for ATMPs. This diagram outlines the three-pronged, risk-based strategy for ensuring viral safety, from source material control to process validation.

The Scientist's Toolkit: Essential Reagents and Materials for ICH Q5A (R2) Compliance

Successfully implementing ICH Q5A(R2) requires a suite of critical reagents and materials. The following table catalogues these essential components, which form the foundation of a compliant viral safety strategy for ATMPs.

Table 2: Essential Research Reagent Solutions for Viral Safety Evaluation

Reagent/Material	Function & Application in Viral Safety	Specific Example(s) / Notes
Qualified Cell Banks	Serve as the foundational starting material. MCBs and WCBs are fully characterized for endogenous and adventitious viruses to establish a secure baseline [79].	Master Cell Bank (MCB), Working Cell Bank (WCB). Characterization includes in vitro assays, in vivo/NGS, and retrovirus testing.
Viral Seeds	For viral vector ATMPs, these are the critical input materials. Testing seeds for adventitious agents and replication-competent viruses is essential [79].	Adeno-associated virus (AAV) seed stock, Lentivirus vector stock. Test for RCAAV/RCL and absence of adventitious viruses.
Model Viruses	Used in viral clearance validation studies to demonstrate the capability of manufacturing steps to remove/inactivate a wide range of viruses [79].	MuLV (for retroviruses), MMV (for small, non-enveloped viruses), VSV or BVDV (for large, enveloped viruses).
NGS Kits & Platforms	For comprehensive, broad-spectrum virus detection in cell substrates and banks, replacing in vivo methods like MAP/HAP tests and reducing animal use [79].	Total nucleic acid extraction kits, library preparation kits, and validated bioinformatics pipelines for viral sequence detection.
PCR/NAT Reagents	Used for specific, sensitive detection of known viral contaminants (e.g., insect rhabdovirus in insect cells) or for quantifying model viruses in clearance studies [79].	Multiplex PCR assays, qPCR/TaqMan probes, primers for specific viral targets.
Virus Removal Filters	A dedicated viral clearance unit operation. Validated to remove viruses of a specific size, providing a robust, complementary safety measure [79].	Parvovirus filters (small, ~20 nm), Retrovirus filters (larger, ~40-50 nm). Must be integrity-tested post-use.
Chromatography Resins	Used in purification and can contribute to viral clearance via binding mechanisms. Re-use studies are needed to demonstrate consistent clearance over the resin's lifetime [79].	Anion exchange (AEX) resins are particularly effective for removing acidic viruses under certain conditions.

Advanced Considerations: Continuous Manufacturing and Prior Knowledge

ICH Q5A(R2) breaks new ground by addressing modern manufacturing paradigms and regulatory science concepts.

Viral Safety in Continuous Manufacturing (CM)

For CM processes, where materials are fed and products discharged continuously, the guideline acknowledges that technical aspects of viral control differ from batch processing [77] [79]. Key considerations include:

• Process Dynamics: Monitoring, detection, and virus removal are affected by system dynamics, parameter fluctuations, and longer bioreactor runtimes, which may increase viral safety risks [77].
• Validation Approach: It is often feasible to use scale-down batch models to validate viral clearance for unit operations within a CM process (e.g., chromatography, low-pH inactivation, virus filtration), provided relevant dynamic parameters are controlled and justified [79].
• Material Traceability: Specific strategies are required for material traceability in the event of a virus detection, given the continuous nature of the process [77].

Utilization of Prior Knowledge (PrK)

The revised guideline explicitly allows for the use of Prior Knowledge to support viral safety strategies [79]. This can significantly reduce product-specific validation burdens.

• Modular Validation: PrK from well-established, in-house unit operations (e.g., a specific chromatography resin or inactivation step) can be applied to new products, provided the scale-down model and critical parameters are comparable.
• Resin Re-use Studies: Data on the viral clearance capacity of chromatography resins over their lifetime can be generated using model viruses and a representative product, and this knowledge can be leveraged for subsequent products using the same resin and similar conditions.

The following diagram illustrates the decision-making workflow for designing a viral clearance study under ICH Q5A(R2), incorporating these advanced concepts.

Diagram 2: Viral Clearance Study Design Workflow. This decision tree outlines the key considerations for designing a viral clearance study, including the impact of manufacturing type and the use of Prior Knowledge.

The implementation of ICH Q5A(R2) marks a significant step towards harmonising and modernising the viral safety evaluation of ATMPs. By explicitly including viral vectors and addressing continuous manufacturing, it provides a much-needed, science-driven framework that aligns with the complex nature of these advanced therapies [77]. For researchers and drug development professionals working within the European Union's regulatory context, this updated guideline has profound implications for batch release requirements.

The guideline's emphasis on a risk-based control strategy offers a structured approach to managing viral safety, which is critical for ATMPs manufactured under pathways like the Hospital Exemption (HE) [25]. The HE enables patient access to custom-made ATMPs, but its utilization has been limited by regulatory complexities and a lack of standardisation across member states [25]. ICH Q5A(R2) can serve as a foundational document to enhance transparency and standardise the viral safety data expected in marketing applications and potentially for supporting the batch release of ATMPs across the EU. The encouragement of NGS and other advanced methods not only aligns with 3Rs principles but also promises more sensitive and comprehensive testing, potentially increasing regulator and patient confidence in the safety of these innovative products [79].

In conclusion, while ICH Q5A(R2) introduces complex new challenges for manufacturers—such as defining the validity of in-house data for new products and adapting to novel testing methodologies [77]—it ultimately provides a robust and contemporary pathway to ensure the viral safety of ATMPs. Its successful application, guided by expert interpretation and engagement with regulators, will be crucial for advancing the field and ensuring the safe and effective delivery of these groundbreaking therapies to patients.

Benchmarking QP Oversight and Importation Procedures for International Supply Chains

The international supply chain for Advanced Therapy Medicinal Products (ATMPs) presents unique regulatory challenges due to their complex, personalized nature and often limited shelf life. Central to ensuring product quality and patient safety across borders are the batch release requirements, particularly the oversight by Qualified Persons (QPs) and importation procedures. The European Union (EU) and United Kingdom (UK) have established sophisticated regulatory frameworks for these products, while the United States Food and Drug Administration (FDA) employs a different model based on manufacturer Quality Units [80]. This guide provides a comparative analysis of these systems, focusing on the practical implications for researchers, scientists, and drug development professionals working with ATMPs in international contexts. Recent regulatory developments, including the UK's 2025 framework for decentralized manufacturing and ongoing revisions to EU GMP guidelines for ATMPs, highlight the dynamic nature of this field and the need for current, detailed comparison [58] [6] [81].

Comparative Analysis of International Regulatory Frameworks

Core Regulatory Philosophies and Accountability Structures

The EU, UK, and US approaches to batch release and importation for ATMPs share the common goal of ensuring patient safety but differ significantly in their implementation and philosophical underpinnings.

• EU Model (Personal Accountability): The EU system centers on the Qualified Person (QP), a specific, personally identifiable expert who holds legal responsibility for certifying that each batch meets Good Manufacturing Practice (GMP) standards and the product's marketing authorization before release. The QP must have specialized academic degrees, relevant industry experience, and be formally recognized by a national regulatory agency. This professional can face personal liability if they negligently certify defective products that cause harm [80].

• UK Model (Oversight and Adaptation): The UK system, while historically aligned with the EU, has introduced innovative frameworks post-Brexit. For clinical supplies entering Great Britain from the EU/EEA, the UK requires a QP Oversight process to verify that initial QP certification occurred in a listed country [82]. Furthermore, the 2025 regulations for decentralized manufacturing create specific pathways for Point of Care (POC) and Modular Manufacturing (MM) of ATMPs, adapting the QP's role for highly personalized, non-centralized production [58] [81].

• US Model (System-Based Accountability): The US FDA relies on a manufacturer's Quality Unit, an independent department within the company, which is responsible for approving or rejecting all components, drug product containers, closures, in-process materials, packaging materials, labeling, and drug products. The system is rooted in Current Good Manufacturing Practices (CGMP) and places legal responsibility on the manufacturer as a firm, rather than on a specifically named individual professional for batch certification [80].

Table 1: Core Accountability Models for ATMP Batch Release

Region	Key Responsible Entity	Basis of Accountability	Legal Foundation
European Union	Qualified Person (QP)	Personal, professional liability	EU Clinical Trials Directive (2001/20/EC); EudraLex Volume 4, Annex 16 [80]
United Kingdom	QP (for oversight/verification)	System oversight with personal responsibility	The Medicines for Human Use (Clinical Trial) Regulations 2004; Human Medicines (Amendment) 2025 [82] [81]
United States	Manufacturer's Quality Unit	Corporate and system liability	21 CFR Parts 210 and 211 (CGMP) [80]

Importation and Testing Requirements for ATMPs

Importation procedures create an additional layer of control for international supply chains, with significant differences in testing requirements.

• EU Importation Testing: The EU mandates that each batch of drugs imported from countries without a Mutual Recognition Agreement (MRA) must be re-tested within the EU before the QP can certify it for distribution. This requirement is detailed in EudraLex Volume 4, Annex 21. This means that ATMPs manufactured in, for example, India or China and imported into the EU must undergo this additional testing. Products from MRA partners like the US, Canada, and Australia are exempt from this re-testing requirement [80].

• US Importation Testing: The FDA does not generally mandate additional testing beyond what is required for the manufacturer's Quality Unit at the site of manufacture as part of standard CGMP. The FDA may require additional testing as part of enforcement actions, such as consent decrees, but this is not a routine requirement for importation [80].

• UK Post-Brexit Oversight: For IMPs entering Great Britain from the EU/EEA, the UK's QP Oversight process does not necessarily require re-testing, but it does require verification that the initial QP certification in the listed country has been performed correctly. The UK QP named on a Manufacturing Importation Authorisation (MIA(IMP)) must have specific documentation available, including evidence of the certifying site's appropriate license and details of the supply chain [82].

Table 2: Comparative Importation and Testing Requirements

Region	Pre-Distribution Testing for Imports	Exceptions	Governing Regulation / Guidance
European Union	Required for imports from non-MRA countries [80]	Imports from MRA countries (e.g., US, Canada, Australia, Switzerland) [80]	EudraLex Vol. 4, Annex 21
United Kingdom	QP Oversight and verification of existing certification; physical shipment to UK often precedes oversight completion [82]	N/A	MHRA Guidance on QP Oversight Process
United States	Not routinely required beyond manufacturer's CGMP testing [80]	May be required via enforcement actions (e.g., consent decree) [80]	21 CFR Parts 210/211

Special Procedures: Decentralized Manufacturing and Hospital Exemption

The complex, patient-specific nature of ATMPs has driven the creation of specialized regulatory pathways that modify traditional supply chain and batch release models.

• UK Decentralized Manufacturing (2025): The UK's MHRA has introduced a comprehensive framework for manufacturing ATMPs at the Point of Care (POC) or via Modular Manufacturing (MM), effective July 2025. Under this model, a central "control site" holds the manufacturing license and creates a Decentralized Manufacturing Master File (DMMF) with instructions for the remote sites. The QP release occurs at the central control site, not at the patient's bedside, which is a significant shift from previous approaches. This system is designed for products that, due to short shelf-life or highly specialized nature, must be made close to the patient [58] [81] [3].

• EU Hospital Exemption: The EU provides an exemption from the central marketing authorization for ATMPs that are prepared on a non-routine basis and used within the same Member State in a hospital under the exclusive responsibility of a medical practitioner for an individual patient. While exempt from centralized authorization, these products must still be manufactured under a national authorization and comply with specific quality standards, as well as traceability and pharmacovigilance requirements. The interpretation of "non-routine basis" and "custom-made product" varies significantly across Member States, leading to a heterogeneous application of this pathway [47].

Methodologies for Regulatory Analysis and Compliance

Protocol for Mapping an International ATMP Supply Chain

Researchers and developers must systematically analyze their product's journey to ensure compliance across jurisdictions.

• Step 1: Supply Chain Node Identification: Document every physical location and legal entity involved in the process, from starting material procurement (e.g., cell collection, vector manufacturing) through to final administration to the patient.
• Step 2: Jurisdictional Classification: Determine the regulatory jurisdiction (EU Member State, UK, US, etc.) for each node identified in Step 1.
• Step 3: Regulatory Pathway Determination: For each jurisdiction, classify the product and its intended use (e.g., Commercial ATMP, Investigational ATMP, Hospital Exemption, POC/MM).
• Step 4: Requirement Mapping: Against each node, list all applicable batch release, QP certification, and importation/testing requirements based on the classifications in Step 3. This includes identifying the need for a QP, the location of batch certification, and any required import testing.
• Step 5: Documentation Flow Analysis: Map the required documentation (e.g., batch records, test results, QP certificates) that must travel with or ahead of the product to facilitate release at each stage.
• Step 6: Gap Analysis and Protocol Finalization: Identify gaps between current procedures and regulatory requirements. Develop a comprehensive quality agreement that clearly defines responsibilities, including those of the QP, across all parties in the supply chain [83] [82].

Workflow for QP Certification and Batch Release of Imported ATMPs

The following diagram illustrates the typical workflow for releasing an ATMP imported into the EU from a non-MRA country, highlighting the dual control steps.

The Researcher's Toolkit for ATMP Regulatory Compliance

Navigating international batch release requires specific knowledge and documentation. The following table details key resources and their functions in the regulatory process.

Table 3: Essential Research Reagent Solutions for ATMP Regulatory Compliance

Tool / Resource	Primary Function	Application in Regulatory Process
EudraLex Volume 4 (EU GMP Guide)	Defines GMP standards for the EU, including specific annexes for IMPs (Annex 13), ATMPs (Part IV), and Imports (Annex 21) [80] [8].	Serves as the primary reference for quality standards that the QP assesses against for batch certification.
ICH Q9 (Quality Risk Management)	Provides principles and examples for quality risk management processes [6].	Integrated into EU GMP; used to justify a risk-based control strategy for the product, which is critical for decentralized manufacturing applications.
Decentralized Manufacturing Master File (DMMF)	A document detailing the product, process, and procedures for manufacturing at remote POC or MM sites [58] [81].	Required by UK MHRA for POC/MM licenses; ensures standardized operations across all decentralized manufacturing units.
Qualified Person (QP)	An individual legally responsible for certifying batch release [80].	The central figure in the EU/UK system for confirming GMP and regulatory compliance before a batch is released.
Mutual Recognition Agreement (MRA)	An international agreement where countries recognize each other's GMP inspections and certifications [80].	Determines whether imported batches require re-testing within the EU, significantly impacting supply chain time and cost.

The international regulatory environment for ATMP supply chains is characterized by a fundamental dichotomy between the EU/UK's personally accountable Qualified Person model and the US's corporate Quality Unit system. For researchers and developers, this means that strategic planning must account for these philosophical and practical differences from the earliest stages of product development. The emergence of novel frameworks like the UK's decentralized manufacturing regulations offers new pathways for delivering complex, personalized ATMPs but also introduces additional layers of oversight and documentation. Success in this landscape depends on a proactive, meticulously documented approach to quality, a clear understanding of the specific QP and importation requirements in each target market, and robust agreements that define responsibilities across what are often globally dispersed supply chains.

Conclusion

The batch release of ATMPs in the EU is governed by a complex, evolving framework that requires deep integration of GMP principles, robust quality systems, and proactive engagement with national authorities. Key takeaways include the critical role of the Qualified Person, the necessity of a life-cycle approach to quality, and the growing importance of managing decentralized manufacturing and complex logistics. Future directions will be shaped by the 2025 revisions to ATMP GMP guidelines, increased harmonization efforts, and the regulatory adaptation to point-of-care manufacturing. For biomedical research, this underscores the imperative to embed regulatory strategy early in development to ensure these transformative therapies can reach patients efficiently across all EU member states.

References

• 1. Regulatory Framework for Advanced Therapy Medicinal ... [https://pmc.ncbi.nlm.nih.gov/articles/PMC6728416/]
• 2. Good Manufacturing Practice for ATMPs [https://www.eurogct.org/research-pathways/manufacturing/good-manufacturing-practice-atmps]
• 3. MHRA Issues New Regulation On Modular And Point Of ... [https://www.cellandgene.com/doc/mhra-issues-new-regulation-on-modular-and-point-of-care-manufacture-of-atmps-0001]
• 4. Comparability Protocols for Biotechnological Products [https://www.bioprocessintl.com/monoclonal-antibodies/comparability-protocols-for-biotechnological-products]
• 5. Comparability of biotechnology-derived medicinal products ... [https://www.ema.europa.eu/en/comparability-biotechnology-derived-medicinal-products-after-change-manufacturing-process-non-clinical-clinical-issues-scientific-guideline]
• 6. EMA Proposes Revisions to GMP Guideline for ATMPs [https://www.gmp-compliance.org/gmp-news/ema-proposes-revisions-to-gmp-guideline-for-atmps]
• 7. Legal framework: Advanced therapies [https://www.ema.europa.eu/en/human-regulatory-overview/advanced-therapy-medicinal-products-overview/legal-framework-advanced-therapies]
• 8. Support for advanced-therapy developers [https://www.ema.europa.eu/en/human-regulatory-overview/advanced-therapy-medicinal-products-overview/support-advanced-therapy-developers]
• 9. Manufacturing Authorisation of ATMPs [https://www.eurogct.org/research-pathways/manufacturing/manufacturing-authorisation-atmps]
• 10. The Role of the Qualified Person (QP) in the Pharmaceutical ... [https://progress-lifesciences.nl/publicaties/role-of-a-qualified-person-in-pharmaceutical-industry/]
• 11. Navigating through Advanced Therapy Medicinal Products ... [https://ispe.org/pharmaceutical-engineering/ispeak/navigating-through-advanced-therapy-medicinal-products-atmps]
• 12. Where the US and EU differ and overlap with CGTs/ATMPs [https://www.pharmalex.com/thought-leadership/blogs/qa-for-innovators-navigating-the-complex-regulatory-world-of-atmps-cgts/]
• 13. Advanced therapy medicinal products: Overview [https://www.ema.europa.eu/en/human-regulatory-overview/advanced-therapy-medicinal-products-overview]
• 14. Regulation and access to advanced therapies [https://www.ibanet.org/regulation-access-advanced-therapies]
• 15. Current challenges and future directions of ATMPs in ... [https://pmc.ncbi.nlm.nih.gov/articles/PMC12274769/]
• 16. EudraLex - Volume 4 - Public Health - European Commission [https://health.ec.europa.eu/medicinal-products/eudralex/eudralex-volume-4_en]
• 17. EudraLex Volume 4 (EU GMP): What It Is, Key Annexes, ... [https://www.scilife.io/blog/eudralex-volume-4]
• 18. EU Regulatory Pathways for ATMPs: Standard, Accelerated ... [https://pmc.ncbi.nlm.nih.gov/articles/PMC6378853/]
• 19. 6 things you should know about drug marketing ... [https://servier.com/en/newsroom/folders/things-know-drug-marketing-authorizations-ma/]
• 20. Why Pharmacopoeia Compliance Is Necessary [https://www.pharmtech.com/view/why-pharmacopoeia-compliance-necessary-0]
• 21. Advanced therapies: marketing authorisation [https://www.ema.europa.eu/en/human-regulatory-overview/marketing-authorisation/advanced-therapies-marketing-authorisation]
• 22. ATMP from Third Countries - New Q&A Paper on Batch ... [https://www.gmp-compliance.org/gmp-news/atmp-from-third-countries-new-q-a-paper-on-batch-release-published]
• 23. EMA Guideline On Clinical-Stage ATMPs Comes Into Effect [https://www.cellandgene.com/doc/ema-guideline-on-clinical-stage-atmps-comes-into-effect-on-the-verge-of-convergence-0001]
• 24. Current State‐Of‐Play of the EU Advanced Therapy ... [https://pmc.ncbi.nlm.nih.gov/articles/PMC12104850/]
• 25. Advanced therapy medicinal product manufacturing under ... [https://www.sciencedirect.com/science/article/pii/S1465324920306320]
• 26. Navigating the complex regulatory world of ATMPs/CGTs [https://www.cencora.com/resources/pharma/qa-for-innovators]
• 27. ICH Q9 Quality risk management - Scientific guideline [https://www.ema.europa.eu/en/ich-q9-quality-risk-management-scientific-guideline]
• 28. Implementing ICH Q9 for GMP quality risk management ... [https://www.eurofins.com/assurance/resources/articles/implementing-ich-q9-for-gmp-quality-risk-management-compliance/]
• 29. The new ICH Q9 Revision on Quality Risk Management ... [https://www.gmp-compliance.org/gmp-news/the-new-ich-q9-revision-on-quality-risk-management-becomes-effective-as-of-23-july-2023-a-detailed-analysis]
• 30. Quality by Design methodology enables sustainable ATMP ... [https://www.antleron.com/post/quality-by-design-methodology-enables-sustainable-atmp-development-and-scalable-manufacturing]
• 31. Regulatory Round-up - July 2025 - Cell and Gene Therapy [https://ct.catapult.org.uk/news/regulatory-round-up-july-2025]
• 32. Chapter 4 - new Requirements for GMP Documentation? [https://www.gmp-compliance.org/gmp-news/ema-chapter-4-new-requirements-for-gmp-documentation]
• 33. Pharma Data Integrity Updates: EU GMP Chapter 4 [https://qt9software.com/blog/pharmaceutical-data-integrity-eu-gmp]
• 34. Guidance on good manufacturing practice and good ... [https://www.ema.europa.eu/en/human-regulatory-overview/research-development/compliance-research-development/good-manufacturing-practice/guidance-good-manufacturing-practice-good-distribution-practice-questions-answers]
• 35. Batch Release for Human Biologicals: vaccines, blood and ... [https://www.edqm.eu/en/omcl/batch-release-for-human-biologicals-vaccines-blood-and-plasma-derivatives]
• 36. Biosimilar medicines: marketing authorisation [https://www.ema.europa.eu/en/human-regulatory-overview/marketing-authorisation/biosimilar-medicines-marketing-authorisation]
• 37. Global Guide to Stability Testing for Cell Therapy Products ... [https://www.atlantisbioscience.com/blog/global-guide-to-stability-testing-for-cell-therapy-products-regulatory-compliance/?srsltid=AfmBOoqbD-NSZNepOKr0PpxX6lgja5CbYLGlrm2ZxsvV-sJjlU8Z5wTy]
• 38. Quality assessment of cellular therapies: the emerging role of ... [https://pmc.ncbi.nlm.nih.gov/articles/PMC2983004/]
• 39. MHRA's Decentralized Manufacturing Regulation Set to ... [https://www.pda.org/pda-letter-portal/home/full-article/mhra-s-decentralized-manufacturing-regulation-set-to-take-effect]
• 40. Registration of multiple manufacturing sites in one product ... [https://www.ifpma.org/publications/registration-of-multiple-manufacturing-sites-in-one-product-license/]
• 41. Centralized vs. Decentralized Manufacturing - Katana MRP [https://katanamrp.com/blog/centralized-vs-decentralized-manufacturing/]
• 42. Renewal and annual re-assessment of marketing authorisation [https://www.ema.europa.eu/en/human-regulatory-overview/post-authorisation/renewal-annual-re-assessment-marketing-authorisation]
• 43. Cell & Gene Therapy Logistics: Clinical Trial Supply Chain ... [https://intuitionlabs.ai/articles/cell-gene-therapy-logistics-supply-chain]
• 44. Delivering Curative Therapies: Autologous vs. Allogeneic ... [https://ispe.org/pharmaceutical-engineering/november-december-2023/delivering-curative-therapies-autologous-vs]
• 45. Advanced Therapy Medicinal Products I ATMPs I [https://www.gxpcellators.com/advanced-therapy-medicinal-products-atmps/]
• 46. Apheresis to Dose: De-risking the ATMP Supply Chain [https://www.phacilitate.com/insights-resources/apheresis-dose-de-risking-atmp-supply-chain]
• 47. ATMPs specific "Hospital exemption" pathway [https://www.eurogct.org/research-pathways/therapy-classification/atmps-applicable-regulatory-pathways/atmps-specific]
• 48. Understanding Biologic and Biosimilar Drugs [https://www.fightcancer.org/policy-resources/understanding-biologic-and-biosimilar-drugs]
• 49. Understanding and Controlling Sources of Process Variation [https://www.bioprocessintl.com/bioanalytical-methods/understanding-and-controlling-sources-of-process-variation-risks-to-achieving-product-critical-quality-attributes]
• 50. Potency Assay Variability Estimation in Practice - PMC [https://pmc.ncbi.nlm.nih.gov/articles/PMC11788244/]
• 51. Manufacturing process development of ATMPs within a ... [https://insights.bio/immuno-oncology-insights/journal/article/467/manufacturing-process-development-of-atmps-within-a-regulatory-framework-for-eu-clinical-trial-marketing-authorisation-applications]
• 52. 98 Biological product manufacturing process validation (PV) [https://www.sciencedirect.com/science/article/abs/pii/S1465324919305195]
• 53. Advanced Therapy Medicinal Products (ATMPs ... [https://ispe.org/pharmaceutical-engineering/ispeak/new-ispe-guide-advanced-therapy-medicinal-products-atmps]
• 54. Validation Risk Assessment of Buffer and Solution Mixing [https://www.bioprocessintl.com/biochemicals-raw-materials/buffer-and-solution-mixing-time-validation-a-risk-assessment-framework-for-analysts-using-matrix-and-bracketing-approaches]
• 55. Implementation of a quality management system for ... [https://pmc.ncbi.nlm.nih.gov/articles/PMC12361990/]
• 56. POINT OF CARE MANUFACTURE (POC): a new emerging ... [https://blog.pqegroup.com/gxp-compliance/point-of-care-manufacture-new-emerging-model]
• 57. Annex 16: Certification by a Qualified Person and EU ... GMP Batch [https://www.gmp-compliance.org/guidelines/gmp-guideline/eu-gmp-annex-16-certification-by-a-qualified-person-and-batch-release]
• 58. 7 New MHRA Guidances To Help You With Decentralized ... [https://www.cellandgene.com/doc/new-mhra-guidances-to-help-you-with-decentralized-manufacturing-for-cell-and-gene-therapies-0001]
• 59. EudraGMDP database | European Medicines Agency (EMA) [https://www.ema.europa.eu/en/human-regulatory-overview/research-development/compliance-research-development/good-manufacturing-practice/eudragmdp-database]
• 60. EudraGMDP - Eudra GMP - Public Layout [https://eudragmdp.ema.europa.eu/inspections/displayHome.do]
• 61. Authorisation of ATMP [https://www.pei.de/EN/regulation/approvals/authorisation-atmp/authorisation-atmp-node.html]
• 62. Human medicines Modular Manufacture and Point of Care ... [https://www.gov.uk/government/publications/human-medicines-modular-manufacture-and-point-of-care-regulations-2025-overview/human-medicines-modular-manufacture-and-point-of-care-regulations-2025-overview]
• 63. Pricing & Reimbursement Laws and Regulations 2025 – Italy [https://www.globallegalinsights.com/practice-areas/pricing-reimbursement-laws-and-regulations/italy/]
• 64. Case Study: Strimvelis | EuroGCT [https://www.eurogct.org/case-study-strimvelis]
• 65. Gene therapy for ADA‐SCID, the first marketing approval of an ex vivo gene therapy in Europe: paving the road for the next generation of advanced therapy medicinal products - PMC [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5452047/]
• 66. Strimvelis | European Medicines Agency (EMA) [https://www.ema.europa.eu/en/medicines/human/EPAR/strimvelis]
• 67. Strimvelis - Wikipedia [https://en.wikipedia.org/wiki/Strimvelis]
• 68. Mitigating Deficiencies in Evidence during Regulatory ... [https://pmc.ncbi.nlm.nih.gov/articles/PMC7327881/]
• 69. Manufacturing [https://www.eurogct.org/research-pathways/manufacturing]
• 70. Advanced therapy medicinal products: a comprehensive ... [https://pharmaceutical-journal.com/article/ld/advanced-therapy-medicinal-products-a-comprehensive-overview-for-pharmacy-professionals]
• 71. Comparison of EudraLex Part IV with PIC/S Annex 2A [https://ispe.org/pharmaceutical-engineering/ispeak/atmp-regulations-comparison-eudralex-part-iv-pics-annex-2a]
• 72. PIC/s Annex 2A for ATMPs - GMP Regulation Updates [https://www.onlinegmptraining.com/pics-annex-2a-atmps-updates/]
• 73. Proposed Revision of EU GMP Part IV, ATMPs [https://www.nsf.org/life-science-regulatory-news/proposed-revision-of-eu-gmp-part-iv-atmps]
• 74. UK-EU Divergence Tracker Q3 2025 [https://ukandeu.ac.uk/reports/uk-eu-divergence-tracker-q3-2025/]
• 75. UK-EU Divergence Tracker Q4 2024 - Q2 2025 [https://ukandeu.ac.uk/reports/uk-eu-divergence-tracker-q4-2024-q2-2025/]
• 76. Q5A(R2) Viral Safety Evaluation of Biotechnology Products ... [https://www.fda.gov/regulatory-information/search-fda-guidance-documents/q5ar2-viral-safety-evaluation-biotechnology-products-derived-cell-lines-human-or-animal-origin]
• 77. Hello again! ICH Q5A revision 2 updates guidance for ... [https://www.parexel.com/insights/blog/hello-again-ich-q5a-revision-2-updates-guidance-for-developers-of-biotechnological-products-and-atmps]
• 78. ICH Q5A(R2) Guideline on viral safety evaluation of ... [https://www.ema.europa.eu/en/ich-q5ar2-guideline-viral-safety-evaluation-biotechnology-products-derived-cell-lines-human-or-animal-origin-scientific-guideline]
• 79. Viral Safety With ICH Q5A Revision 2 [https://www.bioprocessintl.com/viral-clearance/viral-safety-for-biotechnology-products-including-viral-vectors-ich-q5a-revision-2-brings-updated-and-more-comprehensive-guidance]
• 80. Rethinking manufacturing quality oversight for prescription ... [https://www.brookings.edu/articles/rethinking-manufacturing-quality-oversight-for-prescription-drugs/]
• 81. UK amendment supports decentralized manufacturing [https://www.pharmalex.com/thought-leadership/blogs/mhras-regulation-covering-decentralized-manufacturing-to-come-into-effect/]
• 82. The QP Oversight Process [https://www.pnrpharma.com/the-qp-oversight-process/]
• 83. Investigational Medicinal Products— Optimizing the Supply ... [https://www.appliedclinicaltrialsonline.com/view/investigational-medicinal-products-optimizing-supply-chain]