Published on 02/12/2025

Acceptance Criteria in ATMP: Attribute vs Variable

Advanced Therapy Medicinal Products (ATMPs) present unique challenges and opportunities in the pharmaceutical development landscape, particularly regarding validation protocols. With a regulatory environment governed by stringent guidelines from authorities such as the FDA, EMA, and MHRA, understanding the distinction between attributes and variables within Acceptance Criteria (AC) is pivotal for professionals involved in the development and commercialization of biologics. This article serves as a detailed guide on the acceptance criteria, focusing on the validation processes relevant to ATMPs, including Process Performance Qualification (PPQ) and Continuous Process Verification (CPV) tailoring.

Understanding the Fundamentals of Acceptance Criteria

Acceptance criteria define the conditions under which a product, process, or system is deemed acceptable. In the context of ATMPs, the criteria can be categorized into two main components: attributes and variables. Each plays a critical role in ensuring product safety, quality, and efficacy. Understanding these distinctions is essential for establishing robust validation protocols that meet regulatory expectations.

Attributes refer to the specific characteristics of a product that must meet predefined standards to ensure its quality and performance. Examples of attributes in the context of ATMPs include potency, identity, and purity. These aspects are usually measured through established methods and processes, with the results compared against predetermined specifications.

Variables, conversely, are factors that can influence the outcomes of a process but are not direct measures of product quality. These can include environmental controls, manufacturing parameters, and equipment performance. Variables must be monitored and controlled to ensure they do not adversely affect product attributes. Effective management of variables is a critical part of PPQ/CPV strategies within ATMP validation.

Defining Potency and Identity in ATMPs

In the context of biologics and ATMPs, potency and identity are defined as Critical Quality Attributes (CQAs). Potency typically refers to the measure of a drug’s biological effect, while identity verifies the chemical or biological makeup of the product.

The FDA guidance documents, including ICH Q5A(R2), underscore the importance of characterizing these CQAs during the development process. Regulators require comprehensive documentation demonstrating that potency and identity have been validated through rigorous testing, contributing to a product’s ability to confer the intended therapeutic effect.

It is essential to establish appropriate acceptance criteria for these CQAs early in the product development process, ensuring that they are adequately addressed within the validation framework. This encompasses a thorough understanding of the manufacturing process, including viral clearance validation and spiking studies, to effectively establish justified acceptance criteria.

The Role of Viral Clearance Validations

Viral clearance validation is crucial in the manufacturing of ATMPs, particularly those produced via mammalian cell systems. The validation process typically includes spiking studies, in which known quantities of viral particles are introduced into the production process. This experimental approach allows for the assessment of the product’s ability to clear viral contaminants effectively.

To ensure compliance with regulatory expectations, particularly those set forth by the FDA and the EMA, manufacturers must document their viral clearance validation strategies. The guidelines provided by EMA provide vital insights into acceptable methodologies and evaluation criteria.

• Spiking Studies Design: The design of spiking studies should reflect realistic worst-case scenarios to challenge the viral clearance processes effectively while replicating the conditions expected during routine manufacturing.

• Data Interpretation: Data obtained from spiking studies must be analyzed through robust statistical methodologies to ensure that the conclusions drawn are scientifically valid and support regulatory submissions.

• Regulatory Consultation: Engage regulatory affairs professionals early in the development process to ensure that spiking study designs and acceptance criteria are aligned with the expectations of regulatory bodies.

Implementing Closed and Single-Use Systems in ATMP Manufacturing

Closed systems and single-use systems are becoming increasingly prevalent in the production of ATMPs, providing risk mitigation for contamination and operational efficiency. The implementation of these systems has implications for both the PPQ and viral clearance validation processes.

Closed Systems: The benefits of closed systems include reduced operator exposure to hazardous substances and minimized contamination risk during production processes. The engineering controls and environmental parameters of these systems should be rigorously validated against acceptance criteria, confirming that they meet the specific needs of ATMP manufacturing.

Single-Use Systems: Single-use technology (SUT) simplifies operations and reduces the need for cleaning validation. However, it poses unique challenges regarding the establishment of acceptance criteria. Manufacturers must ensure that leachables and extractables from these systems do not impact product quality adversely. Comprehensive testing and evaluation methods for these materials are essential in characterizing risks associated with SUT in ATMP environments.

Aseptic Controls as per Annex 1 Guidelines

Aseptic manufacturing of ATMPs requires adherence to rigorous Aseptic Controls outlined in Annex 1 of the EU GMP Guidelines. These controls play a pivotal role in maintaining the sterility of biological products, which is particularly critical for ATMPs due to their nature and intended use.

There are multiple critical components to consider when establishing acceptance criteria related to aseptic controls:

• Environmental Monitoring: Implement a robust environmental monitoring program to assess and control microbial contamination throughout the production areas. Acceptance criteria must be established for viable and non-viable particles in the cleanrooms.

• Personnel Training: Establish and maintain stringent training protocols for personnel involved in aseptic processing. Employee qualifications should align with the expectations set forth in regulatory guidelines, ensuring that those performing critical tasks are fully competent and aware of contamination control measures.

• Process Validation: Conduct thorough process validation studies that directly correlate with defined acceptance criteria for aseptic conditions. This alignment is vital for establishing the efficacy of the procedures implemented.

PPQ and CPV Tailoring for ATMPs

Process performance qualification (PPQ) and continuous process verification (CPV) are integral parts of the regulatory framework governing ATMP manufacturing. These methodologies should be tailored specifically to account for the unique attributes and variables of ATMPs. Emphasis must be placed on the development of appropriate acceptance criteria that address both process robustness and product quality.

Tailoring PPQ: Effective tailoring of the PPQ process ensures that critical process parameters (CPPs) and CQAs are evaluated thoroughly. The goal is to establish process limits that maintain consistent product quality and safety. Each ATMP should undergo a tailored PPQ plan, integrating specific cycle conditions, statistical analysis, and component verification.

Implementing CPV: CPV is employed to continuously monitor and verify the manufacturing process following the attainment of PPQ criteria. Establishing acceptance criteria for the monitoring of variability during routine manufacturing is critical. These criteria should enable the detection of out-of-specification events early enough to prevent product quality deterioration.

Developing a Comprehensive Validation Strategy

A coherent validation strategy for ATMPs must incorporate the principles of QbD (Quality by Design) along with compliance to regulatory standards. Professionals involved in validation processes should adopt a holistic view that encompasses all stages of manufacturing, from planning to execution, and post-market monitoring.

Key aspects of a comprehensive validation strategy include:

• Risk Assessment: Conduct thorough risk assessments throughout the product lifecycle to identify potential areas of concern, ensuring that acceptance criteria are scientifically justified and in alignment with predefined product requirements.

• Data Integrity: Ensure that data integrity principles are upheld throughout the validation process. This compliance is indispensable, particularly in the context of regulatory auditing and inspection.

• Stakeholder Collaboration: Foster communication between various stakeholders, including research, development, regulatory affairs, and quality assurance teams. This collaborative approach supports the establishment of comprehensive acceptance criteria and validation practices aligned with regulatory expectations.

Conclusion: The Path Forward in ATMP Validation

The development and validation of Advanced Therapy Medicinal Products require a robust understanding of acceptance criteria, including the intricate balance between attributes and variables. As ATMPs continue to evolve, it is imperative for pharmaceutical professionals to remain informed and adept in navigating the regulatory landscape to ensure compliance with the US FDA, EMA, and MHRA standards, along with aligning with the ICH Q5A(R2) guidelines. By adopting effective and science-based validation methodologies, the industry can assure the safety, efficacy, and quality of ATMPs, fostering public health advances in therapeutic options.