Developing cell and gene therapy products (CGT) presents unique challenges, particularly in manufacturing and quality control (Chemistry, Manufacturing, Controls – CMC). Sponsors must adopt a proactive approach to problem-solving and risk assessment to avoid clinical holds and program delays. This is especially critical for autologous cell therapies, where only one batch of starting material is available, leaving no room for error during manufacturing. Additionally, because these therapies involve living cells, they are often highly sensitive to processing timelines. Any delays during manufacturing, testing, or delivery can compromise the product’s viability and effectiveness. Therefore, rigorous quality control is required at multiple stages of the cell therapy manufacturing process to ensure the product’s safety and efficacy.
The Critical Role of Analytical Testing
Analytical testing is a key aspects of CGT development, ensuring the quality, safety, purity, and potency of drug products before they reach the patient. This testing involves the use of both compendial (standardized) and non-compendial (product-specific) analytical methods to rigorously assess the properties of starting materials, raw materials, drug substances, and final products, as well as to conduct in-process testing. The goal is to provide a comprehensive overview of the cell therapy manufacturing process.
Compendial vs. Product-Specific Methods
Health Authorities strongly encourage the use of compendial methods when applicable, particularly for safety testing such as sterility and endotoxin analyses. However, due to the unique nature of cell therapy products, many analytical methods require product-specific development using advanced laboratory techniques, such as flow cytometry, next-generation sequencing, and cell-based functional potency assays. In such cases, sponsors must provide comprehensive scientific justification for their chosen methods and demonstrate reliable performance. The FDA’s cell therapy guidance for these products specifically addresses the need for novel analytical approaches while maintaining rigorous quality standards (FDA Guidance on Considerations for the Development of Chimeric Antigen Receptor (CAR) T Cell Products, 2024) . While allowing flexibility for use of new methodologies, FDA requires analytical validation and use of reference standards to ensure method reliability. While allowing flexibility for use of new methodologies, FDA requires analytical validation and use of reference standards to ensure method reliability.
Key Stages of Quality Control
The quality control process for cell therapies begins with the patient’s starting material and follows through manufacturing, in-process testing, and release testing. For cell therapy products, human cells are collected from the patient (autologous therapy) or from a donor (allogeneic therapy) and transferred to the manufacturing facility, where they undergo genetic modification and expansion before being returned to the hospital to be infused back into the patient. The following stages outline the key steps of the quality control process to ensure product safety, efficacy, and reliability in cell therapy manufacturing.
- Starting Material Testing: The journey begins with thorough testing of starting materials. For autologous therapies, patient cells must meet certain quality specifications to ensure a high probability of manufacturing success. For allogeneic therapies, additional donor eligibility testing adds another layer of complexity, as it requires confirmation of donor suitability and product safety according to strict regulatory guidelines.
- Raw Material Testing: Critical materials, such as cell culture media, cytokines, cell isolation reagents, viral vectors and other gene editing components undergo careful assessment by vendors and in-house by sponsors to ensure consistent quality standards.
- In-Process Testing: Throughout the cell therapy manufacturing process, continuous monitoring of critical parameters is essential. This includes assessing cell culture conditions, cell modification efficiency, and expansion characteristics to provide real-time insights into product development and ensure the process is on track.
- Final Product Testing: Once the manufacturing process is complete, the final therapeutic product undergoes a comprehensive evaluation of product identity, potency, and safety parameters. This includes the quantification of modified cells to confirm the intended composition, assess genetic editing efficiency, and ensure batch-to-batch consistency. Additionally, stability studies are conducted to evaluate the product’s integrity over time, assessing factors such as potency, viability retention, and potential degradation under defined storage conditions. These stability studies are crucial for determining appropriate shelf life, transport conditions, and long-term storage strategies to maintain product quality.
Addressing the Challenge of Potency Testing
Potency testing remains one of the most challenging aspects of cell therapy manufacturing. The FDA’s guidance on potency testing for cellular and gene therapy products (FDA Draft Guidance on Potency Assurance for Cellular and Gene Therapy Products, 2023) emphasizes the importance of developing relevant biological assays that accurately measure the product’s specific mechanism of action. These requirements evolve throughout development, with expectations for quantitative and validated potency measurements as programs progress toward commercialization. These advanced methods not only support regulatory approval but also play a vital role in demonstrating consistent clinical efficacy, ultimately facilitating the transition from early-stage development to full-scale commercialization.
Regulatory Guidelines for Analytical Testing
FDA and ICH guidelines provide a comprehensive and clear framework for developing and validating analytical methods to support cell and gene therapy (CGT) products (FDA Guidance on Human Gene Therapy Products Incorporating Human Genome Editing, 2024 ; ICH Q2(R2) guidelines – Validation of Analytical Procedures). As cell therapy products progress through development phases, the required level of qualification and validation increases. FDA recommends initiating assay development early in the process and employing a variety of assays to thoroughly characterize the product. Scientifically sound principles for assay performance should be applied, ensuring tests are specific, sensitive, reliable, and include appropriate controls or standards. Compendial methods should be used when appropriate, and safety-related tests must be qualified prior to the initiation of clinical studies.
During early clinical trials, sponsors must demonstrate appropriate control of test methods and provide evidence of analytical method suitability. As development progresses to pivotal trials and commercial applications, analytical procedures must undergo thorough qualification and validation in accordance with ICH Q2(R2) guidelines, addressing parameters such as accuracy, precision, specificity, range, and robustness. Each assay used for lot release or stability testing must be qualified by the time efficacy data is collected. Additionally, all non-compendial assays must be fully validated to support a successful marketing application.
Staying Ahead of Regulatory Expectations
The evolution of analytical methods in cell therapy manufacturing continues to advance alongside technological developments and regulatory requirements. Success in this field demands not only technical expertise but also a thorough understanding of regulatory expectations and the ability to implement phase-appropriate analytical strategies.
At Allucent, we help sponsors navigate the complexities of regulatory expectations for cell therapy manufacturing and overcome CMC challenges in their programs. To learn more about how we can help, see Chemistry, Manufacturing and Controls | Allucent. Our goal is to support you in meeting regulatory requirements and achieving key submission milestones, bringing innovative therapies to patients sooner.
Additional References
- 21 CFR Part 610 – General Biological Products Standards. Title 21 of the U.S. Code of Federal Regulations (CFR), Subchapter F – Biologics. U.S. Food and Drug.
- 21 CFR Part 1271 – Human Cells, Tissues, and Cellular and Tissue-based Products. Title 21 of the U.S. Code of Federal Regulations (CFR), Subchapter L – Regulations for the Registration of Human Cells, Tissues, and Cellular and Tissue-Based Products. U.S. Food and Drug Administration (FDA).
- Safety Testing of Human Allogeneic Cells Expanded for Use in Cell-Based Medical Products, Draft Guidance for Industry. U.S. Food and Drug Administration (FDA), 2024.
About the Author
Alicja Fiedorowicz, MSc is Associate Director, CMC in Regulatory and Drug Development Consulting at Allucent, specializing in CMC regulatory support of cell and gene therapies and biologics. With extensive experience in advising on CMC-related regulatory content for health authority submissions, her expertise encompasses regulatory gap analysis, analytical development, quality control, product and process characterization, comparability evaluations, and process and analytical validation. She holds a MSc degree in Biotechnology from Wroclaw University of Technology.
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