Potency Measurements for Cellular and Gene Therapy Products

1. Potency Measurements for Cellular and Gene Therapy Products Denise K Gavin, Ph.D. Center for Biologics Evaluation and Research Office of Cellular, Tissue and Gene Therapies Division of Cellular and Gene Therapies denise.gavin@fda.hhs.gov Cellular, Tissue, and Gene Therapies Advisory Committee Meeting #41February 9, 2006

2. Suzanne Epstein Denise Gavin Mike Havert Syed Husain Ke Liu Jawahar Tiwari Keith Wonnacott Kimberly Benton Eda Bloom Maritza McIntyre Raj Puri Stephanie Simek Celia Witten FDA Participants Executive Secretary: Gail Dapolito

3. Meeting Goals • To discuss challenges related to the development of meaningful and relevant potency assay measurements for C&GT products. • To obtain perspectives and advice from members of the CTGTAC regarding the implementation of scientifically valid assays for measuring potency of C&GT products.

4. Products Regulated by the Office of Cellular, Tissue and Gene Therapy • Cellular Therapy Products • Gene Therapy Products • Tumor Vaccines • Tissues • Tissue Engineered Products • Combination Products • Devices used for cells/tissues • Xenotransplantation Products • Other Novel Products

5. Cellular Therapy Products • Stem cells • e.g. embryonic, hematopoietic, cord blood, mesenchymal, neural • Differentiated cells • e.g. pancreatic islets, chondrocytes, myocytes, neural, stromal • Immune cells • e.g. dendritic cells, lymphocytes, macrophages • Tumor cells • Source Material • autologous and allogeneic donors, cell lines

6. transfer of genetic material by means of a vector... Gene Therapy Gene Gene Plasmid/Lipid Vector Viral Vector

7. … directly to the subject or … used to modify cells ex vivo for subsequent administration to the subject Gene Therapy Products

8. C&GT based Tumor Vaccines • Cellular products • Gene therapy products • Cell lysates • Cells and cell lysates pulsed with peptides, proteins or vectors • Adjuvant

9. Successful Product Development • Demonstrate product to be safe, pure and effective • Full product characterization • Demonstration of manufacturing and product consistency (e.g. adherence to cGMPs)

10. Characterization for Product Release 21 CFR 610 • Safety • Sterility • Purity • Identity • Potency

11. Potency 21 CFR 21 CFR 600.3 (s): The word potency is interpreted to mean the specific ability or capacity of the product…to effect a given result. 21 CFR 610.10: Tests for potency shall consist of either in vitro or in vivo tests, or both, which have been specifically designed for each product so as to indicate its potency…

12. Determining Potency? • ICH: SectionQ6B “Guidance for Industry: Specifications: Test Procedures and Acceptance Criteria for Biotechnological/Biological Products”: • Potency is the quantitative measure of biological activity based on the attribute of the product that is linked to the relevant biological properties. • A relevant, validated potency assay should be part of the specifications … (21 CFR 211)

13. Assay Validation FDA: Guidance for Industry: Analytical Procedures and Methods Validation & ICH Validation of Analytical Procedures… • “process of demonstrating that analytical procedures are suitable for their intended use.” • Does the assay measure what it is intended to measure? • Does the assay yield data that answers a specific question? • Does the assay provide confidence in the results? • It is in the regulations (e.g. 21 CFR 211)

14. Assay Validation • Accurate • Precise • Sensitive • Specific • Reproducible • Robust

15. Advantages to Early Potency Assay Development • Critical to determine activity of product • Critical to assure product quality and lot-to-lot consistency • Important when interpreting clinical data • Allows for examination of multiple assays • Provides data to establish specifications for lot release • Provides data to support product stability • Important measure for comparability studies

16. Acceptable Potency Assay • Measure of the biological activity of the product • Measure a property specific to the product • Results should be available for lot release • Results should be quantitative • Demonstrate lot-to-lot consistency • Compared to a reference standard or appropriate control • Validated for licensure

17. Approaches for Potency Measurements • Direct measure of biological activity • Biological assay methods • product specific characteristics • Indirect measure of biological activity • Analytical assay methods • correlated to product specific activity

18. Biological Assay Methods • In vivo • Animal models • Structural repair • Gene function • Immune response • In vitro • Cell culture • Signaling pathways • Proliferation • Enzymatic activity

19. Analytical Assay Methods • Immunochemical Procedures • ELISA • Quantitative flow cytometry • ELISPOT • Molecular and Biochemical Procedures • Microarray/genomics technologies • RT-PCR • Q-PCR • Proteomics

20. Challenges-Product Characteristics • Complex mechanism of action • Multiple active components • Potential for interference or synergy • Product variability due to variability in starting cells or tissue • Limited material to test • Product stability • Many products administered within hours of harvest • Storage/holding may effect viability, potency, etc.

21. Challenges-Assay Characteristics • Variability • Identify sources of variability • Design assay to minimize effects • Validation • Limited availability of reference standards and controls • Patient specific therapies • Novel vectors • Time constraints

22. What is FDA doing to help? • Work with sponsors early in product development • Apply a phased in approach to assay development • Allow multiple assays to demonstrate potency • Matrix Approach

23. Acceptable Potency Assay Demonstrating Potency

24. Typical Challenge Demonstrating Potency

25. Simple Matrix Approach Demonstrating Potency

26. Simple Matrix Approach Demonstrating Potency

27. Simple Matrix Approach Demonstrating Potency 

28. Multiple challenges Demonstrating Potency

29. Multiple Assay Matrix Approach Demonstrating Potency

30. Multiple Assay Matrix Approach Demonstrating Potency

31. Multiple Assay Matrix Approach Demonstrating Potency

32. Multiple Assay Matrix Approach Demonstrating Potency  

33. Examples of Potency Approaches • Functional assay • e.g. antigen specific T-cell activation (e.g. cytokine release via ELISA or ELISPOT) • Analytical assay correlated to function • e.g. correlating antigen binding (e.g. flow cytometry) to T-cell activation • Matrix of assays correlated with function • e.g. phenotypic cell surface marker and antigen presentation correlated with T-cell activation

34. Summary • Start Potency Assay Development Early! • Recognize challenges to meeting requirements • Evaluate more than one assay • Collect correlation data • A well characterized product is important when interpreting clinical data

35. Obtaining Information from CBER • http://www.fda.gov/cber/publications.htm • Guidance Documents • ICH Guidelines • Email: Manufacturers assistance: MATT@CBER.FDA.GOV Consumers:OCTMA@CBER.FDA.GOV

36. Guest Speakers John Elliott, Ph.D., National Institute of Standards & Tech. David C. Kaslow, M.D., Vical, Inc. Bryan Butman, Ph.D., GenVec, Inc. Alla Danilkovitch,. Ph.D., Osiris Therapeutics, Inc. Kelledy Manson, M.T., M.S., Therion Biologics Corp. Nicole Provost, Ph.D., Dendreon Corp.

37. Advice sought from committee We are seeking input from the committee regarding: • Assay design schemes that will be necessary to validate potency assays for C&GT products • The types of data and studies necessary to demonstrate valid correlations between analytical assays and biological properties of the products • What is necessary to adapt and implement state of the art technologies (microarray, genomics, proteomics) to obtain consistent results necessary for their use in potency measurements • Future research directions that may be necessary to demonstrate potency for cell and gene therapy products

38. Classic Example of Potency