1. U.S. Food and Drug Administration CENTER FOR BIOLOGICS EVALUATION AND RESEARCH March 29, 2007 Sipuleucel-T BLA 125197 US Food and Drug Administration Center for Biologics Evaluation and Research US Food and Drug Administration Center for Biologics Evaluation and Research Cellular, Tissue and Gene Therapies Advisory Committee Meeting 1

2. U.S. Food and Drug Administration CENTER FOR BIOLOGICS EVALUATION AND RESEARCH FDA Presenters Keith Wonnacott, PhD, Product Reviewer Division of Cellular and Gene Therapies Office of Cellular, Tissue and Gene Therapies Ke Liu, MD, PhD, Clinical Reviewer Division of Clinical Evaluation, Pharmacology and Toxicology Office of Cellular, Tissue and Gene Therapies BoGuang Zhen, PhD, Statistical Reviewer Division of Biostatistics Office of Biostatistics and Epidemiology 2

3. U.S. Food and Drug Administration CENTER FOR BIOLOGICS EVALUATION AND RESEARCH Sipuleucel-T Review Team Product Keith Wonnacott, PhD Thomas Finn, PhD Malcolm Moos, MD, PhD Syed Husain, PhD Clinical Ke Liu, MD, PhD Peter Bross, MD Statistics BoGuang Zhen, PhD Labeling Catherine Miller Pharmacology and Toxicology Yongjie Zhou, MD, PhD Bioresearch Monitoring Bhanu Kannan Epidemiology Kathryn O’Connell, MD, PhD Manufacturing and Product Quality Gang Wang, PhD Mary Padgett Project Management Lori Tull, RAC Mark Davidson

4. U.S. Food and Drug Administration CENTER FOR BIOLOGICS EVALUATION AND RESEARCH Manufacturing Process Overview: Sipuleucel-T (APC8015) 3-4 Days PA2024 ANTIGEN ADDED Collects patient’s blood cells Further enrichment of mononuclear cells APC activation/antigen processing Final formulation 4

5. U.S. Food and Drug Administration CENTER FOR BIOLOGICS EVALUATION AND RESEARCH Manufacturing Process Overview: Placebo (APC-Placebo) REFRIGERATED—No PA2024 antigen added Collects patient’s WBC Enriches for mononuclear cells NO APC activation Final formulation 5

6. U.S. Food and Drug Administration CENTER FOR BIOLOGICS EVALUATION AND RESEARCH B cellT cell Monocyte NK cell BasophilRed Blood CellsEosinophilNeutrophilPlatelets Granulocytes In vitro culture Buoyant Density Centrifugation Steps (BDS77 and BDS65) Apheresis (APH) Final product formulation (FP) 6

7. U.S. Food and Drug Administration CENTER FOR BIOLOGICS EVALUATION AND RESEARCH B cellT cell Monocyte NK cell In vitro culture Buoyant Density Centrifugation Steps (BDS77 and BDS65) Apheresis (APH) Final product formulation (FP) 7 PA2024

8. U.S. Food and Drug Administration CENTER FOR BIOLOGICS EVALUATION AND RESEARCH The Manufacturing Process: IS designed to: –Enrich for mononuclear leukocytes –Activate antigen presenting cells IS NOT designed to : –Control cell number –Control relative percentages of cell types 8

9. U.S. Food and Drug Administration CENTER FOR BIOLOGICS EVALUATION AND RESEARCH Numbers of cells infused are highly variable Minimum total nucleated cell (TNC) number required for APH starting material Process significantly reduces TNC number No upper or lower limit for TNC in the final product 9

10. U.S. Food and Drug Administration CENTER FOR BIOLOGICS EVALUATION AND RESEARCH Relative percentages of cell types are highly variable Monocyte CD14, CD54 B cell CD19 T cell CD3 NK cell CD56 10

11. U.S. Food and Drug Administration CENTER FOR BIOLOGICS EVALUATION AND RESEARCH Proposed mechanism of action During manufacturing In the patient 11

12. U.S. Food and Drug Administration CENTER FOR BIOLOGICS EVALUATION AND RESEARCH Evidence for cellular activation and antigen presentation Monocytes take up the antigen and express the cell surface marker CD54 CD54 expressing cells present antigen to antigen-specific T cell clones Antigen presenting cells show increased expression of costimulatory molecules 12

13. U.S. Food and Drug Administration CENTER FOR BIOLOGICS EVALUATION AND RESEARCH Monocytes take up antigen Antigen uptake Cell type specific marker 13

14. U.S. Food and Drug Administration CENTER FOR BIOLOGICS EVALUATION AND RESEARCH Monocytes express CD54 14

15. U.S. Food and Drug Administration CENTER FOR BIOLOGICS EVALUATION AND RESEARCH Evidence for cellular activation and antigen presentation Monocytes take up the antigen and they express the cell surface marker CD54 CD54 expressing cells present antigen to antigen-specific T cell clones Antigen presenting cells show increased expression of costimulatory molecules 15

16. U.S. Food and Drug Administration CENTER FOR BIOLOGICS EVALUATION AND RESEARCH Costimulatory molecule expression increases during culture with PA2024 16

17. U.S. Food and Drug Administration CENTER FOR BIOLOGICS EVALUATION AND RESEARCH Evidence for cellular activation and antigen presentation CD54 expressing cells present antigen to T cells Monocytes take up the antigen and they express the cell surface marker CD54 Antigen presenting cells show increased expression of costimulatory molecules 17

18. U.S. Food and Drug Administration CENTER FOR BIOLOGICS EVALUATION AND RESEARCH CD54 positive cells stimulate PAP- specific T cell clones Number of Cells 18

19. U.S. Food and Drug Administration CENTER FOR BIOLOGICS EVALUATION AND RESEARCH Product Potency Potency assay is designed to detect activated antigen presenting cells Product potency measures: –Number of CD54 positive cells indirect indication that cells can process and present antigen –CD54 upregulation ratio of CD54 expression before and after culture with PA2024 direct measure of cellular activation 19

20. U.S. Food and Drug Administration CENTER FOR BIOLOGICS EVALUATION AND RESEARCH Limitations of the potency assay Impact of manufacturing on other cell types and the potential role of other cell types is unknown –CD54 cells typically represent only 20% of final product –Roles of B cells, T cells and NK cells are unknown The ability of sipuleucel-T (APC8015) to induce an immune response against the patient’s prostate cancer is unknown 20

21. U.S. Food and Drug Administration CENTER FOR BIOLOGICS EVALUATION AND RESEARCH Summary Cell number varies Relative percentages of cells vary Sipuleucel-T contains activated antigen presenting cells that can process and present the tumor antigen The contribution of other cells to product activity is not known 21