CENTER FOR DRUG EVALUATION, NMPA

　　November, 2023

　　I. Overview

　　In recent years, significantly increased CAR-T cell therapy products (hereinafter referred to as CAR-T products) have been applying for clinical trials in China, some of them have been authorized for marketing to treat multiple disease indications. However, the technology in this field is rapidly evolving, the manufacturing process, the quality control, the design and execution of clinical trials are different from those of other biological products. The understanding and knowledge of manufacturing processes and product quality attributes are cumulatively developing. Therefore, various manufacturing changes such as process optimization often occur during clinical trials and after marketing, of which, the addition or change of manufacturing sites, change of genetic modification systems, replacement of raw materials and optimization of analytical methods are common. Autologous CAR-T products are personalized therapeutic products, uses variety of raw materials for production, involves complex operational procedures in donor cell collection, manufacturing, testing, cryopreservation, transportation and infusion, inherently bears high variability in starting materials, manufacturing process and product quality attributes. In addition, batch size is usually limited, plus unique quality management system (QMS), together making change management and comparability studies rather challenging.

　　Technically, the post-marketing manufacturing changes study of CAR-T products in general may follow the ICH Q5E and the guidance “The Technical Guidance on CMC Change Study of Marketed Biologics (Trial Version)” issued by NMPA in 2021 [1-2]. The above two guidelines provide technical requirements for comparability study of manufacturing changes such as proteins, peptides and their derivatives, and change study of raw materials such as viral vectors and recombinant proteins used for CAR-T product production, which can be appropriately referenced if applicable.. However, some specific requirements are unsuitable due to the particularity of autologous CAR-T products. EMA (European Medicines Agency) provided the comparability considerations for Advanced Therapy Medicinal Products (ATMP) in Questions and Answers [3] issued in December, 2019. Some general principles for cellular therapy products CMC changes were suggested, but none specific technical requirements were provided, in NMPA issued related guidance [4] in 2022. In July, 2023, FDA (Food and Drug Administration, US) issued the draft guidance of CGT products manufacturing changes and comparability study for comment purposes [5].

　　Therefore, while adapting the general rules of manufacturing changes and comparability study for biological products, the particularity of autologous CAR-T products must be fully consider in making manufacturing changes studies. As reference for applicants/MAH, this Q&A summarizes the common and most often asked questions of manufacturing changes in autologous CAR-T product clinical trials and post-marketing, and provides answers to the questions on the basis of current scientific knowledge and regulatory evaluation experiences. This document reflects the current thinking of regulatory agency, will be enriched and updated along with the technology development and regulatory review experience.

　　This document is primarily intended to the manufacturing changes study of autologous CAR-T products, yet it is inclusive of other cell therapy products, such as TCR-T cell products, TIL products, and somatic stem cell products, if any of the principles or answers presented herein are applicable.

　　II. Common problems and technical requirements

　　1. General principles for manufacturing Change

　　Question: What are the study design principles for manufacturing change of CAR-T cellular therapeutic products?

　　Answer:

　　The applicant/MAH is responsible for change management, manufacturing change and change assessment. Applicants/MAH are encouraged to continuously improve product quality, and safety through process optimization/changes, while demonstrating the changes introduced have no adverse impacts on the product.

　　(1) Change Management

　　Considering rapid evolvement of CAR-T technology and unique product development process, the applicant/MAH is encouraged to explore, on the basis of QbD concept, the impact of manufacturing approach, manufacturing materials, manufacturing process, and other factors on product quality and safety. It is recommended to endeavor defining CAR-T product CQAs from early development stage progressively, in order to better understand of the correlation between product quality attributes and clinical safety and efficacy, to facilitate the impact assessment of the changes imposed on product quality.

　　Along process optimization, applicants/MAH are encouraged to purposefully select higher grade raw materials and safer gene modification systems, develop closed or semi-closed manufacturing processes, improve quality specifications, and optimize analytical methods. Considering the particularity of CAR-T products and the complexity of manufacturing change, it is recommended to design the plan and strategy of manufacturing change as early as possible along product development, so that to avoid/reduce unexpected changes which may impede the product development process. With the accumulation of product and process knowledge, the change plan and the strategy should be periodically revised and expanded. For post-marketing products, it is recommended to design a reasonable and sensible risk-based change plan. As for frequent post-marketing changes, it is recommended to timely consult the regulatory agency the change plan and submission strategies.

　　(2) Principles of risk-based change design

　　It is recommended that the applicant/MAH conduct a risk assessment of manufacturing change, and design scientific-sound change plan according to the stage of product development, the nature of the change.

　　Throughout product development, the extent of comparability study should be expanded accordingly to proceed clinical study. Generally, optimization of manufacturing process is a norm in the early clinical stage which often results in changes, risk assessment of those changes should focus mainly on safety to support clinical trials, efficacy may be evaluated as appropriate, thus change plan should be designed on the basis of risk concerns of the stages. By taking into consideration of the uniqueness of CAR-T product manufacturing process, the variability of autologous source material, and the limitations of scientific understanding of manufacturing process and product, in principle, major manufacturing changes should be accomplished, manufacturing process should be locked before the start of the confirmatory clinical trial, so that manufacturing site, capacity, process, materials, testing, and product quality and other aspects of the confirmatory clinical trial are closely interconnected with commercial manufacturing. It is generally not recommended to implement major changes after the completion of confirmatory clinical trials, unless there are good reasons, in such case, comprehensive comparability studies should be conducted, and communication with regulatory agencies is encouraged.

　　The impact imposed on CAR-T products by manufacturing changes is inseparably associated with the nature of the changes, from apheresis, CAR design, raw materials, process complexity, manufacturing mode, transportation and storage conditions, and assay methods etc. The extent of impact varies with the complexity and the ranking of the changes. In general, the higher the risk-ranking of and the more complex of the change, the greater the risk and the severer the impact on product safety and efficacy. For example, changes such as critical raw materials (e.g., process changes in genetic modification system) and key cell culture operations may significantly affect the quality of CAR-T products. Multiple interlinked lower-risk changes may cumulatively uprise the overall risk, in this case, it is recommended to analyze the superimposed impact on product quality. In summary, change plan should be based on scientific evaluation, case-by-case, holistically analyze potential risk factors and their cumulative impacts.

　　Comparability study is progressive, when the CQAs of CAR-T products are not well-characterized, the correlation between the CQAs, and safety and efficacy would not be explicitly defined. If comparability study indicates that the quality attributes of CAR-T products are incomparable pre- and post-change resulting potential impact on efficacy and safety based on current scientific knowledge, or risk assessment concludes that the CMC changes pose a greater risk and uncertainties, non-clinical and/or clinical bridging studies becomes necessary to evaluate the safety and efficacy of post-change products no matter the product is on clinical study stage or launched.

　　2. Particularity of manufacturing changes

　　Question: What are the difference of manufacturing change comparability study between autologous CAR-T product and classical biological product?

　　Answer:

　　There exist unique features of manufacturing changes and comparability study of CAR-T products, in terms of manufacturing materials and processes, and product quality attributes. Furthermore, CAR-T products are living cellular products with complex structure in nature, while the knowledge of process and product is yet limited, therefore there are great risks resulting from changes and rather challenging to do comparability.

　　(1) In regard of manufacturing materials, autologous CAR-T product is personalized cell therapy, whose starting cellular materials are individually collected in hospitals, collection processes may differ among hospitals, thus composition, expansion capability and other quality attributes of the cellular materials vary. Comparability and other studies such as validation of collection and processing procedure may use samples from different donors, the inherent individual variability of source cellular materials further complicates comparability study. Additionally, there are many other manufacturing materials including key materials such as beads and media, whose changes may impose a significant impact on cell composition and biological activity of CAR-T products. Thus when running comparability study of raw material manufacturing process and quality, the impact of raw material on CAR-T products should be studied.

　　(2) In regard of manufacturing process, CAR-T products may be manufacturing in different approach. Manufacturing area can be divided according to processing steps or batches. The expansion strategy of manufacturing capacity includes increasing batch production scale (scale-up) and increasing the number of production batches while maintaining the manufacturing process and batch size (scale-out). Manufacturing process is often characterized with many processing steps including in vitro genetic modification, lengthy turnaround time, and lack of virus removal/inactivation, leading to high risk of adventitious agents contamination. With the advances in technologies, such as novel gene modification systems and processes, automated instruments and in-process control techniques may be employed in CAR-T cell production, above-mentioned manufacturing approaches and advanced technologies may introduce additional risk factors, and further complicate comparability study design and implementation.

　　(3) In regard of quality study and analytical method, CAR-T products is usually composed of several cell types, their characterization often involves quality analysis of cell subtypes, biological activities, metabolic status, product related impurity including defining target and non-target cell populations. Considering the autologous starting cells are collected from variable donors which experienced different chemo-radiotherapy and show different response, the variation of T cell subsets population, differentiation and function, along with limited cell number, make it a huge challenge to obtain sufficient representative samples for comparability study. Besides, due to the multifaceted mechanism of action of CAR-T products, it remains challenging to establish a robust biological activity assay that is capable of accurately investigate the mechanism of action. In addition, the variety of surface markers and the variability of test methods further intense the difficulty of quality study and test results interpretation.

　　(4) In regard of data collection and analysis, due to the continuously progress of CAR-T related science, it is suggested that the applicant/MAH continuously collect the post-change data, analyze the comparability study scope, protocol and result retrospectively, further confirm the impact of manufacturing change on product quality, accumulate the knowledge of product quality, facilitating the better quality and risk control.

　　In summary, comparability study of manufacturing changes of CAR-T products requires good understanding and control of variables throughout manufacturing process, while ensuring the effectiveness of quality management system on quality and risk control. Key areas of concern include leukapheresis collection and transportation, audit and quality control of raw materials, manufacturing facility, utilities, and the design and validation of processing procedures, the prevention and control strategies of mix-ups, contamination, and cross-contamination, the suitability and precision of analytical methods, and the appropriate personnel and manufacturing capacity etc.

　　3. Comparability study protocol

　　Question: How to design the comparability study?

　　Answer:

　　There are two ways to do comparability study: a side by side comparison between pre- and post-change batches, and the comparative analysis of post-change batches against pre-change historical batches. Considering the fluctuation of manufacturing process and the variability of analytical methods, whenever possible, it is recommended to do side by side comparability study and comparative analyze results against historical data, including assessing potential impact of variation in analytical assay, manufacturing materials, operators, equipment, etc.

　　Regarding samples selection, study protocol design, and acceptance criteria of comparability study, the representativeness of samples should be considered to fit the characteristics of CAR-T products and the type of the change to be analyzed. Considering the individual differences of autologous products, it is recommended to fully evaluate the rationality of the selection of comparability study samples according to the development stage, the nature of changes and statistical methods to be employed.. If start source materials are from heath donors, the differences between healthy donor cells and patient-derived cells should be considered, as materials from healthy donor may not accurately represent the impact of changes on patient-derived materials, thus whenever possible, it is preferred to do comparability study using patient-derived materials. In case cells from health donor are used for comparability study, it is recommended to comparative analyze in-process parameter control, in-process testing, and product quality attribute between health donors and patient-derived, to demonstrate the robustness of the process and the representativeness of the health donor cells. In order to minimize the impact of the variability of donor derived cells on comparability study, it is recommended to split the start source materials from the same donor into two portions and manufacture products separately in parallel (split-based approach). As for changes in specifications, it is recommended to revise specifications primarily using data generated from patient-derived materials, caution should be applied when citing data derived from health donor materials.

　　Comparability study protocol should cover process, characterization features, product quality attributes and stability. For manufacturing process changes, a comparison of process parameters and in-process control parameters should be included. It is possible to insert additional sampling points at critical process stages for pre- and post-change analysis. For example, cell growth and cell viability may be compared using cell culture suspension collected at different process steps. In terms of quality attribute analysis, it is recommended to properly expand quality attributes (such as cell phenotype) on top of established specifications. Regarding stability study, it is recommended to select representative batches, bases on risk-assessment of the changes, for long-term stability study, accelerated stability (if applicable), excursion of storage and transportation (if applicable) condition study, and clinical use condition study. The parameters analyzed should be sensitive and indicative of potential impacts.

　　To establish comparability acceptance criteria, it is recommended to consider development stage and batch number, analyze data from pre- change process development batches and historical clinical batches (including maximum, minimum, average, median, etc.). The applicability of statistical analysis methods used to set the ranges of acceptance criteria should be justified. Data for comparability study should be from as many as possible released pre-change batches without cheery-pick. Data analysis should collectively consider the potential impact of source materials (e.g., patient vs. health donor) and change ranking on the acceptance criteria and comparability.

　　Risks naturally differ along development stages and type of changes, the applicant/MAH is thus encouraged to consult with the regulatory authority the comparability study for given specific changes. Up to date, the correlation between the CAR-T product quality attributes and clinical safety and efficacy has not been explicitly established, in case the risk of change is high, or the uncertainty of the impact on product quality, or the quality attributes of pre- and post-change products are not comparable, nonclinical and/or clinical bridging studies may be required to address the potential impact of the changes on clinical safety and efficacy, such as, the in vitro and/or in vivo potency comparability study, in vivo persistency and distribution, differentiation and systematic toxicity evaluation of pre- and post- change products.

　　4. Change of manufacturing site, manufacturing line (module), and manufacturing changeover frequency while manufacturing process remains unchanged

　　Question (1): What aspects should be considered for comparability study of the change where manufacturing sites and manufacturing lines are added in “mirror image” manner? While the manufacturing process and batch size remain unchanged.

　　Answer:

　　Assuming facility layout and quality management system remain unchanged, the “mirror image” addition of manufacturing sites and manufacturing lines should first be in compliance with GMP requirements. On the premise that the layout of the sites and the quality management system remain unchanged, the new sites and lines should be well assessed for the purposed of the change, including environment, utilities, personnel, QC testing, and equipment. The Aseptic process simulation (APS) validation should be performed, and design the process study with appropriate batch number based on manufacturing process, to qualify and/or verify its operation and robustly support manufacturing. Nevertheless, comparability study should be performed to compare pre- and post-change batches. For details, please refer to the Question 1 and Question 3 in this document.

　　Based on product development stage, that the suitable manufacturing capacity validation should be designed. The validation should simulate the worst conditions of the same/different manufacturing process steps simultaneously running in different areas/cleanroom, according to manufacturing mode, facility layout and manufacturing process (key factors include manual operation, mix-up, product exposure to environment, or complex manipulation procedure). As manufacturing mode may widely vary, the applicant/MAH is encouraged to consult with the regulatory authority before making changes and performing comparability study.

　　Question (2): What aspects should be considered for comparability study of changes of increasing manufacturing changeover frequency? While manufacturing process, manufacturing site and line are not changed.

　　Answer:

　　While the manufacturing equipment, process, and operator are not changed, the applicant/MAH should justify the increase in manufacturing changeover frequency and the potential risk based on acquired manufacturing experience and manufacturing process characteristics. Risk assessment of the change should include analyzing correlation between manufacturing deviation and manufacturing changeover frequency, if it is the case, corrective action and optimization should be carried out accordingly. Risk assessment should focus on manufacturing environment, utilities, personnel, QC testing personnel and instruments, line clearance/cleaning/disinfection/sanitization (or sterilization) procedures, and the suitability of other auxiliary functions, along with acquired manufacturing experience, historical data and aseptic process simulation (APS) to support manufacturing capacity validation design and verification performance. Following the validation of manufacturing changeover frequency, in combination with facility layout and process characteristics, manufacturing capacity should be calculated and justified as a result of assessment of personnel, QC testing, facilities and equipment under the worst scenario of manufacturing scheduling and conditions. In addition, risk assessment should focus on mix-up, contamination, cross-contamination when complex process steps are simultaneously carried out in the same area/cleanroom. As manufacturing mode may widely vary, the applicant/MAH is encouraged to consult with the regulatory authority before making changes and performing comparability study.

　　5. Change of manufacturing site and manufacturing line (including manufacturing process change)

　　Question: What aspects should be considered for comparability studies of changes in manufacturing site and manufacturing line along with manufacturing processes? For example, changing cell culture manipulation or culture medium components.

　　Answer:

　　Theoretically, this kind of change has the potential impact on product quality, applicant/MAH is encouraged to conduct the full comparability study, and continuously improve product quality and safety through manufacturing process optimization, meanwhile appropriately plan changes, acquire process and product knowledge, explore the impact of manufacturing process changes on the quality of CAR-T products.

　　When manufacturing site change is accompanied by manufacturing process change, it is recommended to assess the impact of the change on product safety and efficacy, by taking into account product development stage, pre-change manufacturing experience and product clinical performance, for comparability study, please refer to Question 1 and Question 3 in this document. Regarding process changes, it is recommended to design change-sensitive sampling points to analyze the change impact. For example, by increasing frequency of continuous sampling, or by conducting monitoring of process performance based on process knowledge. It is also possible to improve in-process risk management by expanding testing or employ more advanced test methods, and study on the quality attributes of post-change intermediates and products. For raw material change, please perform comparability study according to the answers to Questions 6 and 7. In comparability study, it is advised to include multiple representative batches, the coverage of comparison indices, the rationality of preset acceptance criteria, the validity of test methods, and the objectivity of data analysis. Comparability study should demonstrate that post-change manufacturing process can robustly manufacture CAR-T products meeting specifications.

　　6. Gene modification system change

　　Gene modification system change herein refers to changes in raw materials, manufacturing process, and specifications etc., excluding changes gene modification system per se (e.g., lentiviral vector structure and biological properties).

　　Since CMC of different gene modification systems is rather complex, applicant/MAH is encouraged to communicate the specific changes with CDE.

　　Question (1): What aspects should be considered in comparability study for manufacturing process changes of lentiviral vector?

　　Answer:

　　Gene modification of T cells using viral vectors is an important step in the manufacture of CAR-T products. For the changes in viral vector manufacturing process, risk assessment should consider raw materials, manufacturing process, vector quality attributes and stability. Comparability study should be designed according to risk assessment of changes. When the risk of change is high, it is recommended perform a holistic comparability study of manufacturing process, quality, and stability. In case manufacturing process changes of viral vector are assessed to potentially affect CAR-T product safety and efficacy, comparability study should include CAR-T products in addition to viral vector.

　　For viral vectors manufactured by plasmid transient transfection, please refer to the Question 6 (2) for the technical requirements of comparability study of plasmid changes.

　　Besides release testing, comparability study of viral vector may need analyzing extended quality attributes depending upon risk assessment of the changes (including plasmids, host cells). The following should be analyzed: in-process contamination of adventicious agents, and whole genome sequence, purity, transduction efficiency, and process-related impurities and viral vector product-related impurities, etc. to support the clinical safety and efficacy of post-change viral vector. In comparability study, it is recommended to combine the nature of change and risk assessment to design the side by side comparability study and/or retrospective comparative analysis of historical vector data, and select appropriate statistical analysis tools to set reasonable comparability acceptance criteria of viral vector.

　　When process change potentially affects the purity, impurity level and biological activity of viral vector, in turn affects clinical safety and efficacy of CAR-T products, CAR-T product comparability study should be performed for multiple representative pre- and post-change viral vector batches. It is recommended to analyze multiple paired batches of CAR-T products produced using split source materials (2 samples from the same donor cells) and pre- and post-change batches of viral vector, and focus on quality difference during CAR-T product manufacturing. The CQAs of CAR-T products for comparability study should include at least cell viability, transduction efficiency, vector copy number, CAR expression level, biological activity, and replication competent virus. When applicable, comparability acceptance criteria may be established on the basis of historical data of clinical batches or process validation batches of CAR-T products.

　　Comparability study of manufacturing process changes of viral vectors should follow the same technical requirements, regardless the source of the viral vectors, for example home-made, manufactured by CDMO or purchased from supplier. In case viral vector is manufactured by CDMO or purchased from supplier, the supplier shall notify the applicant/MAH of any changes in a timely manner, the applicant/holder should design comparability study accordingly, and manage the risk of the change by signing a quality agreement with the supplier. The applicant/MAH should assess quality control risk of viral vector through supplier audit, viral vector release testing, quality control strategy, and batch supply capability, and establish appropriate internal control specifications. Additionally, viral vector stability during transportation should be fully assessed by transportation validation study, to ensure that the quality of viral vector meets the manufacturing requirements of CAR-T products.

　　During confirmatory clinical trial and post-marketing, viral vector process change should be avoided or conducted with caution. If major changes are unavoidable, and the risk is assessed high, pre-clinical and/or clinical bridging study may be necessary, for specific requirements, CDE should be consulted.

　　Question (2): What aspects should be considered in comparability study of changes in plasmids used for lentiviral vector packaging?

　　Answer:

　　Changes of lentiviral vector packaging plasmid system include changes of packaging system (e.g., change of packaging cell line or plasmid number), changes of plasmid sequence, and changes of plasmid manufacturing process.

　　Changes of lentiviral vector packaging plasmid system are high risk. In this case, please refer to Question 6 (1) to design and perform comparability study of lentiviral vectors and the comparability study of CAR-T products.

　　When packaging plasmid sequence is changed, risk assessment should be carried out on the changes in CAR sequence (except the CAR amino acid sequence change) and other elements’ sequences. When the sequence of antibiotic resistance gene, regulatory element, enhancer, or promoter is changed, it should be determined if the changed sequences are in vector genome, and whether the changes affect transgene expression, then assess the impact of the change on the quality of lentiviral vector and CAR-T products. If changed sequences are not packaged into the genome of lentiviral vector and have marginal impact on transgene expression, comparability study of lentiviral vectors should be performed, whether comparability study of corresponding CAR-T products should be performed is dependent upon the outcome of lentiviral vector comparability study. If the changed sequence are packaged into the genome of lentiviral vector, the comparability studies of both vector and CAR-T product are recommended. If the comparability study and evaluation indicate the high risk, the in vivo bridging study should be conducted. The communication with CDE on bridging study scope is encouraged. CAR is a critical element that affects the safety and efficacy of CAR-T products, when its amino acid sequence is changed, it is recommended to communicate with CDE and submit a new IND.

　　If plasmid manufacturing process is changed while plasmid sequence remains unchanged, risk assessment should be carried out, and plasmid quality pre- and post-change should be analyzed. When plasmid process change clearly causes the shift of plasmid purity and impurity level (such as the supercoiled ratio, residual host DNA level, etc.), comparability study should be performed on the lentiviral vector manufacturing process and lentiviral vector quality to analyze the impact of the change. When changes in plasmids clearly impact on the quality of lentiviral vector, then comparability studies of corresponding CAR-T products should be conducted to analyze potential impact of the change on the quality of CAR-T products.

　　7. Critical raw materials change

　　Question: What aspects should be considered in comparability study of changing autologous serum with serum replacement or changing the supplier of magnetic beads?

　　Answer:

　　During process optimization along product development, applicant/MAH is encouraged to substitute raw materials of human/animal origin with those of chemically defined, or to use raw materials of higher quality (for example, use the pharmaceutical grade raw materials for substitution). When it is assessed that the change of raw materials (for example, critical raw materials such as serum, magnetic beads, and culture medium) may affect the quality of CAR-T products, comparability study should be performed on raw materials and corresponding CAR-T products.

　　Comparability study of raw materials should be designed according the type of raw materials, the nature of the change, and the criticality of the raw materials in CAR-T product manufacturing. In case manufacturing site or manufacturing process of raw material is changed, supporting data should be submitted to show quality comparability of pre- and post-change raw materials, and each quality index stays within comparability acceptance criteria. For raw materials produced by recombinant expression, the comparability study of raw material change may refer to ICH Q5E and other relevant guidance for the change of biological products. It is advised to investigate composition, purity, impurity, and biological activity of pre- and post-change raw materials.

　　If the change of raw materials potential impacts cell composition, biological activity and other quality attributes of CAR-T products, which in turn affects the safety and efficacy of CAR-T products, apparently comparability studies on CAR-T products should be performed. Owing to the individual variability of source materials and the meaningfulness of statistical power, for the change of critical raw materials during clinical trials, it is recommended to use multiple batches of pre- and post-change raw materials, perform comparability study of CAR-T products manufactured with the raw materials using split source materials, demonstrate the equivalence of pre- and post-change raw materials, in combination with the data of manufacturing process, CAR-T product quality and stability, and investigation of the impact of raw material change on CAR-T manufacturing process performance and product quality.

　　For changes of cytokine concentration and culture medium composition, since the changes may affect cell composition and biological activity of CAR-T products, it is recommended to include in full comparability study in-process control, release criteria, and a comparative analysis of extended quality attributes of CAR-T products, if necessary, conduct comparative stability studies.

　　In the event of changes of donor cell collection process, changes in collection process, storage and transportation procedures, manipulation steps and parameters should be specified, sort out the manipulation steps that may have an potential impact on CAR-T products, and analyze the potential impact of collection procedures on the quality of starting cell materials, CAR-T product quality, and comparability studies.

　　8. Changes of drug product formulation

　　Question: How should the comparability study be performed when drug product formulation of CAR-T product is changed, for example, change of cell cryopreservation solution?

　　Answer:

　　Common changes in drug product formulation include changes in dosage form (frozen/fresh), strength and excipients (cryoprotectant, cell cryopreservation solution, etc.). When drug product formulation is changed, a comparative study should be conducted, and the basis for the use of the new drug product formulation should be justified, supported with the study data of CMC, safety, excipients (e.g., cell cryopreservation solution), formulation, stability, and supportive documents.

　　When the supplier of excipients is changed, while the type and amount of excipients remain unchanged, comparability study of pre- and post-change excipients is required, and the safety and quality of post-change excipients should be no lower/less than the pre-change. Post-change excipient should have no impact on the safety and efficacy of CAR-T products.

　　The risk is usually high to change type/amount of excipient and dosage form. When cell cryopreservation solution is changed, the choice of the post-change shall be justified based on the in-process control and CAR-T product release data of the pre- and post-change, moreover, comparability study of pre- and post-change CAR-T product quality and stability should be performed. When drug product formulation is changed, the compatibility assessment/study of the primary packaging material and infusion device set should be performed. The expiration date of post-change CAR-T product shall be re-established with the real-time stability study data of long-term storage.

　　In case comparability study data is insufficient or comparability study is inconclusive, or the risk of ingredient change is high, non-clinical and/or clinical bridging studies should be conducted.

　　9. Changes of storage, transportation, and clinical use conditions

　　Question: What aspects should be considered in comparability study? When the shelf-life of CAR-T products is extended after process change, and the freezer transporting CAR-T products from manufacturing site to hospitals is changed.

　　Answer:

　　When transportation, storage and use conditions of CAR-T products are changed, post-change stability study and pre- and post-change stability comparability study should be performed. For change impacting product stability (e.g., changes in storage and transportation temperatures), it is recommended to conduct thorough comparative stability analysis of long-term stability, accelerated stability, transportation stability, and in-use stability of representative batches packaged in containers of the same material, and the study should include the worst-case scenario. If the impact of change is assessed negligible on CAR-T product stability (e.g., the secondary packaging change without changing storage and transportation temperature), some of stability study could be waived on the basis of complete temperature record and other supporting data. When transport conditions are changed, transport validation studies is expected.

　　Accelerated stability studies may help elucidating the degradation pattern of CAR-T products under extreme conditions, evaluating the detection sensitivity of degradation derivatives by current analytical methods, and facilitating quality assessment of product accidentally exposed to unintended storage and transportation conditions, therefore the applicant/MAH is encouraged to perform appropriate comparative study of accelerated stability, and to analyze degradation pattern of CAR-T products.

　　Considering particularity of autologous CAR-T products and the urgency of clinical needs for certain indications, when a batch size is not enough to support all testing of stability study, multiple batches may be used in complementation to maximize stability study. For a given batch whose size limits testing of stability study, testing could be subtracted or testing frequency could be reduced on the basis of acquired relevant and appropriate data review (only applicable to testing whose risk does not rise with storage time being, such as process-related impurities), and under conditions of justification and being complementary to other batches. When batch size is sufficient of full stability study, a comprehensive comparability study is expected. In stability study, at least these safety- and efficacy-related parameters should be analyzed: cell viability, biological activity, and the number of CAR-positive cells. If there are steps such as pause or holding during manufacturing, the stability study of process intermediates is expected.

　　For the extension of the shelf life of CAR-T product, full long-term stability study data of post-change products should be provided to support the approval of full shelf life.

　　10. Changes of analytical methods

　　Question: What aspects should be considered in comparability study of the changes caused by the optimization or transfer of analytical method, and the change of testing site?

　　Answer:

　　With the advancement of technology and the accumulation of CAR-T product knowledge, the analytical methods of CAR-T cells are rapidly updated, new analytical methods are dynamically developed, and the sensitivity and specificity of analytical methods are continuously upgraded. In order to accurately analyze CAR-T product quality attributes, applicant/MAH is encouraged to adopt appropriate analytical methods in CAR-T product testing and make progressive effort of method optimize.

　　In the event of analytical method optimization or change, qualification and/or validation of analytical method to be changed is expected, comparability study of pre- and post-change methods should be performed to demonstrate that post-change method is equivalent or better than pre-change one. In general, methodological bridging study should be conducted, which recommend to test multiple representative batches with post-change method and compare the data obtained with the data generated with pre-change method. In case the post-change test results of a given sample differs from pre-change test data, the post-change method should be justified, and the revision of quality specifications should be evaluated.

　　When the testing site is changed, a gap analysis, methodology transfer protocol and transfer study is expected. The methodology transfer study protocol should include operational details of analytical methods, material and equipment, samples used, pre-set acceptance criteria. For flow cytometry, if applicable, reference standards should be used to calibrate flow cytometry devices of testing sites, to ensure their consistency. Once the methodology transfer is completed, multiple tests of the same samples should be performed at each testing site to verify the equivalence of pre- and post-change testing methods.

　　Changes of cell counting and CAR transduction efficiency analytical methods (e.g., flow cytometry) may impact dose calculation of CAR-T products, if necessary, dose calculation should be adjusted accordingly to ensure the accuracy of dose administration. Biological activity is an important quality attribute of CAR-T products, a thorough study is expected on any changes, and release testing method may be appropriately adopted through in vivo mechanism of action, testing methodology qualification validation studies, and advancement of product development.

　　11. Change of specifications and limit range

　　Question: What aspects should be considered in comparability study of changes in CAR-T product quality specifications and limits?

　　Answer:

　　The establishment and revision of quality specifications is a norm through entire life cycle of CAR-T product. Applicant/MAH is encouraged to explore the correlation between product quality attributes and clinical efficacy using data and knowledge accumulated during clinical trial and post-marketing, to progressively improve and define quality specifications of CAR-T products.

　　In the event of changing testing and acceptance limits of CAR-T products, justification should be well established, and supporting data are expected. Supporting data should at least include pre- and post-change quality data of multiple batches of CAR-T products, validation data of analytical methods (including study data for reference substances), stability study data, and historical data of clinical batches. Changes of quality specifications should not result in a decline in CAR-T product quality control. When stability study is involved, post-change specifications should be suitable to monitor product stability changes during storage, and product stability should meet post-change acceptance limits. For the changes of intermediates quality specifications and in-process control specifications, above-discussed principles and requirements could be adopted.

　　Applicant/MAH is encouraged to continue clinical data collection on clinical study and post-marketing stage, investigate the correlation between clinical safety and efficacy, and manufacturing process parameters and product quality attributes, and periodically retrospective analysis of quality data trend and progressively improve quality specifications according to the data accumulated.

　　Ⅲ. References

　　[1] ICH Q5E, Comparability of Biotechnological/Biological Products Subject to Changes in Their Manufacturing Process, 2005.

　　[2] NMPA.《已上市生物制品药学变更研究技术指导原则(试行)》, 2021.

　　[3] EMA. Questions and answers-Comparability considerations for Advanced Therapy Medicinal Products (ATMP), 2019.

　　[4] NMPA.《免疫细胞治疗产品药学研究与评价细胞治疗产品药学研究与评价技术原则指导(试行)》，2022.

　　[5] FDA. Draft Guidance for Industry-Manufacturing Changes and Comparability for Human Cellular and Gene Therapy Products, 2023.