Stem Cell-based Therapies and FDA Regulations

Transcription

1 Stem Cell-based Therapies and FDA Regulations By Trina Slabiak, MS, RAC Stem cell-based therapies are arriving in the clinic as Phase 1 studies. Which technological challenges and US Food and Drug Administration (FDA) regulations govern the development and translation of stem cell therapies into medical treatments? Irving Weissman, MD, PhD, discussed the current and future caveats of bringing stem cell therapies to clinical trials at the Institute of Stem Cell Biology and Regenerative (ISSCR) conference in San Francisco on 15 June We begin with discovery and must have the appropriate adult stem cells to regenerate the required tissue, explained Weissman. Then we move on to the preclinical testing and determine under what situations these cells will work. Moving past preclinical testing is difficult because no venture capital group, investment bank or NIH [National Institutes of Health] will fund the clinical research. So you try to form a company and struggle every day to raise the money for clinical trials or work with the California Institute of Regenerative Medicine (CIRM) to get funding, added Weissman. The goal is to do a reasonable clinical trial where you can learn what the regulatory issues are and learn how to make the product in a safe way. Twenty-five years ago we showed that simultaneous transplant with a blood-forming stem cell and a donor organ induces tolerance to the new organ in animal models. We are close to having the tools to test these therapies in the clinic, Weissman concluded. We are just at the cusp of discovery for human stem cell therapies. 1 Trends in Cell Therapies Trends in cell therapies have expanded beyond human embryonic stem cells. Multipotent adult stem cells include adipose-derived, placental and amniotic membrane-derived sources. Cell therapy applications are numerous and expanding and include tissue engineering, cell products to induce immune tolerance for organ transplant, gene therapies to treat regulatoryfocus.org November

2 Table 1. Regulations Applicable to Stem Cell Based Products Treatment Product Guidance and Legislation Regulatory Law Human cells, tissue or cellularbased products (HCT/P) Biologics Section 361, Public Health Service Act, infectious disease Section 351, Public Health Service Act, premarket approval, safety and effectiveness 21 CFR (d) 21 CFR 600 Drugs Food, Drug, and Cosmetic Act 21 CFR 200 Cell therapy and gene therapy when genetic material is transferred to cells ex vivo Xenotransplantation Application of Current Statutory Authorities to Human Somatic Cell Therapy Product and Gene Therapy Products, 14 October 1993 US Public Health Service. Guideline on Infectious Disease Issues in Xenotransplantation, FDA 28 January 1997 Medical device 21 CFR 800 chronic disease and medical device-delivered cell therapies. The California Institute for Regenerative Medicine (CIRM) currently is sponsoring research groups working on several diseases including cancer, HIV, stroke, type 1 diabetes, ALS and sickle cell anemia. The three major cell-based therapy approaches include embryonic stem cells, adult stem cells and application of stem cells to deliver traditional small molecule therapies. 2 FDA Regulations Because cell-based therapies are comprised of human tissues in a variety of ways and have multiple therapeutic applications, stem cell therapies fall under many FDA regulatory categories. FDA regulations cover these applications and cell varieties in detail. Cell-based therapeutic agents fall under the definition of the treatment products listed in Table 1. Deborah Hursh, PhD, from FDA s Center for Biologics Evaluation and Research (CBER), spoke at the Symposium on Stem Cell Translation: Strategies Best Practices & Regulatory Considerations in San Francisco on 27 September Her program outlined FDA s regulatory perspectives on stem cell-based therapies. 3 At first glance, FDA regulations are very detailed. Hursh s talk brought life to the subject of FDA regulations by briefly outlining the many required steps from development through manufacturing and clinical application. She also discussed safety and effectiveness aspects of cell therapies of particular concern to CBER. Safety and Effectiveness The plasticity of stem cells, allowing their further differentiation into diverse cell types, raises concerns about cross-differentiation that must be addressed. Multipotent and pluripotent cells may differentiate into unintended cells and integrate into unintended targets, causing adverse effects. Cell-based products require a variety of safety considerations. Stem cell products are heterogeneous substances. The concept of lower dose may not reduce their clinical or adverse effects. It is difficult or impossible to discontinue or reverse the effect once cell therapy is administered. According to Hursh, the most dangerous risks are ectopic tissue formation, migration away from the treatment site and cell therapies that lead to tumorgenicity. Stem cell products do not lend themselves to a one size fits all concept of production, development and regulation, explained Hursh. Flexibility in how to fulfill the criteria is needed for diverse and novel products in an evolving field. FDA review of safety and effectiveness is product-based. Hursh encourages early interaction between sponsors and the agency to establish manufacturing and preclinical study criteria. FDA tries to help when pointing out critical issues ahead of time so the sponsor doesn t have to backtrack. regulatoryfocus.org November

3 Table 2. Manufacturing Materials Likely to Provoke FDA Safety Concerns Manufacturing Material Human serum or serum proteins Affinity purified proteins Cell or tissue extracts Potential Contaminant Viral and bacterial contaminants Adventitious agents in antibodies Possible viral contaminants Chemistry, Manufacturing, Controls Since clinical trial design is supported by manufacturing, source control and cell therapy product testing must be clearly defined. Cell therapy products do not have the luxury of being sterilized prior to administration. The major components of source control for cell therapy production are donor testing, control of cell banks and control of all reagents and supplies that have had contact with the product. Donor Testing Controls to prevent transmission of infection or introduction of infectious agents during cell processing are referred to as donor testing controls. Allogeneic donors must comply with the tissue rules set forth in 21 CFR 1271, Subpart C. Donor screening includes medical record review, physical assessment and medical history interview. The donor must be tested with FDA-approved or -cleared donor screening tests. This type of donor testing follows the same guidelines as blood donor testing. Some of the tests include screening for HIV, Hepatitis C Virus (HCV), Cytomegalovirus (CMV), parasites and an expanding list of tropical diseases migrating to North America. Cell Banks Cells that are expanded and used for pluripotent master cell bank storage are subjected to another level of testing scrutiny. Hursh clarified, If you are going to make a cell bank, there is a good chance that you could introduce another adventitious agent into the cell bank. Master cell banks must follow the regulations set forth in CFR 600 to test for adventitious agents. These agents include but are not limited to HIV, HCV, CMV, Human T-lymphotropic virus (HTLV), Epstein-Barr virus (EBV), parvovirus B19, and in vivo and in vitro virus testing. Other adventitious agents, such as bovine viruses and viruses from fetal calf serum, are based on the growth media that support the cells. All the materials used to grow and expand cells in culture are subject to bacterial and fungal testing. The cells in the bank must be characterized by molecular markers and cell surface to define their viability and purity. The number of passages, karyotypic alterations and established intrinsic property measurements must be documented. Testing for cell-based product banks may be limited by the availability of adequate sample size. If you are working from a smaller limited source, the rules are flexible and negotiated with CBER, Hursh added. Material and Supply Qualification All reagents and supplies must be documented to show they are qualified for a specific use. Researchers must ensure that reagents will perform as expected in the manufacturing process. The clinical quality of reagents must be evaluated for safety, purity and potency. It is important to avoid changing vendors during the manufacturing process. What is your plan if a sole vendor of a critical reagent or manufacturing equipment ends production? asked Hursh. The best thing to do if you need to use a reagent with For research purposes only, Not for human use on the label is to call FDA and ask what you need to establish the safety parameter. The manufacturing materials of greatest concern to FDA are listed in Table 2. regulatoryfocus.org November

4 Table 3. CFR Specifications for Biologic Products Safety Code of Federal Regulation , , , Endpoint Purity Free of extraneous material Free from opportunistic viruses, mycoplasma and endotoxins Bacterial and fungal sterility Identity Specific test to distinguish it from other similar substances Constituent Materials Potency Assay for biological function Identify all ingredients, preservatives, diluents, adjuvants and excipients Manufacturing Manufacturing is defined as culturing cells. Hursh mentioned this can be a complicated issue for early development. Controls and standardization of the manufacturing process must be applied to the product, process and facility. Establishing critical manufacturing process control is better for the final product and these specifications will be necessary during the clinical trial, added Hursh. Reproducibility and consistency of product lots are critical for administering the proper dosage to achieve clinical efficacy. If you don t know what you have, it will be difficult to interpret your clinical results, she said. Product Specification All manufactured drugs and biologics must demonstrate product consistency. The best way to ensure integrity and stability of stem cell therapies is to demonstrate manufacturing process controls. Hursh explained, FDA understands that there will be a heterogeneous population of cells but the sponsor must know the exact components of the heterogeneity every time the product is manufactured. Product quality testing requires both in-process testing and final product lot release testing. Biologic product specifications for safety, purity, identity, constituent material and potency are all clearly defined in the Code of Federal Regulations (CFR). The applicable parts of the biologic Code of Federal Regulations are outlined in Table 3. Identity Testing Cell-based therapies present particularly complex manufacturing challenges because their craft and techniques are still being developed. The manufacturing process is likely to evolve as researchers become more knowledgeable. Lot release specifications for FDA Investigational New Drugs must follow guidelines set forth in the CFR. The viability for live cell therapy products must be at least 70%. Most lot release specifications are established by the sponsor and justified on their manufacturing experience and clinical need, explained Hursh. Biomarkers Biomarkers are essential to evaluating product identity, potency, dose concentration and purity. Unlike traditional chemically manufactured drugs, biological products must define their active ingredients from biological assays. Geron s Phase 1 investigational therapy to treat spinal injury used 14 biomarkers to characterize its product.4 FDA biomarker characterization recommendations are cell surface markers, quantitative morphology and gene or protein arrays. If multiple cell types or cells at different stages of differentiation are expected to be present, we suggest you include markers that will identify the major contributing populations for identity and purity, Hursh noted. regulatoryfocus.org November

5 Potency Potency validation assays for cell-based therapies are particularly challenging. Analytical assay methods correlating unique specific activity of the product are accepted as an indirect measure of biological activity. Direct measure of biological activity is preferred but indirect measure fulfills the potency assay requirements. Hursh outlined a multiple assay approach for situations where it may not be possible or feasible to develop a single assay that encompasses all elements of an acceptable potency assay. Potency assays are required prior to Phase 3 clinical testing and she recommends not waiting until the end of Phase 2 to develop your potency assay. Comparability FDA-approved products must be comparable from lot to lot. They also must demonstrate comparability from early preclinical studies through all phases of clinical investigation. This can be rather challenging for small developers working with small sample sizes and limited starting material availability. Cell Migration Alice Varga, MS, MA, from Geron spoke at the Regulatory Affairs Professionals Society annual meeting in San Jose, California on 25 October She reviewed Geron s regulatory challenges with a current Phase 1 clinical trial for spinal injury treatment. Cell therapies are injected into or administered to appropriate target sites in the patient. It is important to know where your cells are going once they are injected into a patient. Geron s stem cell treatment was injected into a spinal injury site by highly trained surgeons. Geron needed to determine whether there were enough cells at the target site, whether there was distribution outside the target site, whether cells were migrating at the target site and how these cells migrated over time. Varga reported Geron has not found any cells outside the target area within the spinal column. Geron shut down its Phase 1 clinical study on spinal regeneration in November 2011 due to financial concerns, leaving Advanced Cell Technology as the only remaining US company with an active cellular regeneration clinical study using human embryonic stem cells. 5 The patients treated with Geron s investigational human embryonic stem cell therapy for spinal injury are still being monitored by the company. 6 Safety Safety is an important issue at FDA. Source control of cell-based therapies is pivotal to ensuring safety. For small developers and independent researchers, manufacturing is financially challenging. The amount of time and money required to develop stem cell or call based therapy is staggering. Each stage of development is highly regulated and following those regulations is very expensive. To ensure patient safety, comprehensive histological examination of the cell-based therapy is required by FDA to determine unregulated cell growth, cell migration, post-transplantation survival, fusion with the patient s existing cells and tissue integration. Current Clinical Studies Most cell based therapies are currently being developed by independent researchers. Funding sources for the manufacturing and preclinical testing stages is limited. News from the 7 th Annual New York Stem Cell Summit on 21 February 2012 reported 182 active clinical trials using mesenchymal stem cells for over 40 different applications. 8 Active, recruiting, and terminated stem cell clinical studies can be found at the website. regulatoryfocus.org November

6 FDA Approval and Consumer Alerts Umbilical cord blood collected from a placenta with the birth mother s consent is currently the only FDA-approved stem cell product. There are a few recent examples of unapproved stem cell products reaching the market without FDA approval. In December 2011, three people were arrested in the US and charged with 15 counts of criminal activity related to manufacturing, selling and using stem cells from cord blood without FDA sanction or approval. 8 A Texas midwife obtained cord blood by telling mothers it was for research purposes and sold the cord blood to a laboratory in Arizona. The Arizona lab sold the cord blood to a third party in South Carolina. The final fraudulent stem cell product ended up with a doctor who travelled to Mexico to perform unapproved stem cell procedures. A stem cell banking company in Houston is being investigated for possibly administering unproven stem cell treatments to patients. FDA considers it to be a crime to inject unapproved adult stem cells into patients. 9 FDA Partnership FDA is committed to bringing cell-based therapies safely from the clinic to the patient. The staff offers support and advice concerning the manufacture and development of cellbased therapies. It is important to communicate with the agency early in the manufacturing process to avoid costly mistakes. We can expect safe cell-based treatments to arrive on the market in the years to come. References 1. Weissman I. Press briefing at 2010 Annual Meeting of the International Society for Stem Cell Research (ISSCR); 15 June 2010; San Francisco, CA. 2. California Institute for Regenerative Medicine (CIRM) Annual Report. 3. Hursh D. FDA s Approach to Regulation of Stem Cell Therapies. Presentation at International Society of Cellular Therapy (ISCT) 2nd Annual Symposium on Stem Cell Translation: Strategies, Best Practices & Regulatory Considerations; 27 September 2010; San Francisco, CA. 4. Varga A. Update on Cell and Gene Therapy. Presentation at 2010 Regulatory Affairs Professional Society Conference & Exhibition; 25 October 2012; San Jose, CA. 5. Pollack A. Geron Is Shutting Down Its Stem Cell Clinical Trial. The New York Times. 14 November Blaney M. Imetelstat as an Inhibitor of Cancer Stem Cells Targeting Cancer Stem Cells in Oncology. Presentation at Molecular Medicine Tri-Con; 20 February 2012; San Francisco, CA. 7. Caplan A. Presentation at 7 th Annual New York Stem Cell Summit; 21 February 2012; New York, NY. 8. Thwarting a Stem Cell Scheme, FDA Warns About Consumer Stem Cell Claim. FDA s Consumer Updates. ForConsumers/ConsumerUpdates/ucm htm#Thwarting. Accessed 24 September The Darker Side of Stem Cells. Nature. 2012; 483(7387): 5. Author Trina Slabiak, MS, RAC, began her career as a cell and molecular biologist. She is published in the areas of oncology, HIV, and metabolism. She is currently working as clinical regulatory professional and can be reached at bluemolecule@gmail.com by the Regulatory Affairs Professionals Society. All rights reserved. regulatoryfocus.org November