Potency assay development for cellular therapy products: an ISCT review of the requirements and experiences in the industry.

The evaluation of potency plays a key role in defining the quality of cellular therapy products (CTPs). Potency can be defined as a quantitative measure of relevant biologic function based on the attributes that are linked to relevant biologic properties. To achieve an adequate assessment of CTP potency, appropriate in vitro or in vivo laboratory assays and properly controlled clinical data need to be created. The primary objective of a potency assay is to provide a mechanism by which the manufacturing process and the final product for batch release are scrutinized for quality, consistency and stability. A potency assay also provides the basis for comparability assessment after process changes, such as scale-up, site transfer and new starting materials (e.g., a new donor). Potency assays should be in place for early clinical development, and validated assays are required for pivotal clinical trials. Potency is based on the individual characteristics of each individual CTP, and the adequacy of potency assays will be evaluated on a case-by-case basis by regulatory agencies. We provide an overview of the expectations and challenges in development of potency assays specific for CTPs; several real-life experiences from the cellular therapy industry are presented as illustrations. The key observation and message is that aggressive early investment in a solid potency evaluation strategy can greatly enhance eventual CTP deployment because it can mitigate the risk of costly product failure in late-stage development.

Developing assays to address identity, potency, purity and safety: cell characterization in cell therapy process development.

A major challenge to commercializing cell-based therapies is developing scalable manufacturing processes while maintaining the critical quality parameters (identity, potency, purity, safety) of the final live cell product. Process development activities such as extended passaging and serum reduction/elimination can facilitate the streamlining of cell manufacturing process as long as the biological functions of the product remain intact. Best practices in process development will be dependent on cell characterization; a thorough understanding of the cell-based product. Unique biological properties associated with different types of cell-based products are discussed. Cell characterization may be used as a tool for successful process development activities, which can promote a candidate cell therapy product through clinical development and ultimately to a commercialized product.

Validation of short-term handling and storage conditions for marrow and peripheral blood stem cell products.

BACKGROUND: Allogeneic hematopoietic stem cell transplants from unrelated donors are routinely used in the treatment of patients with hematologic malignancies. These cellular products are often collected off-site and require transport from the collection site to transplantation centers. However, the effects of transport conditions and media on stem cell graft composition during short-term storage have not been well described. STUDY DESIGN AND METHODS: Five bone marrow (BM), four filgrastim-mobilized peripheral blood stem cell (PBSC), and four nonmobilized peripheral blood mononuclear cell (PBMNC) products were collected from healthy volunteer donors and stored at 4 or 20°C for up to 72 hours in 10% PlasmaLyte A plus anticoagulants such as 10% acid citrate dextran-A (ACD-A) and/or 10 IU/mL heparin. Products were evaluated at 0, 24, 48, and 72 hours for cellular content, viability, and metabolic activities. RESULTS: BM products maintained equivalent cell viability when stored at either 4 or 20°C over 72 hours, but cell viability was better maintained for PBSC products stored at 4°C. The mean viable CD34+ cell recovery for PBSC and BM products stored over 72 hours at 4°C was higher than 75%. Significantly lower CD34+ cell and colony-forming unit recoveries were seen in PBSC products but not BM products stored at room temperature. Faster lactic acid accumulation was observed in PBMNC and PBSC products stored without ACD-A. CONCLUSIONS: Seventy-two-hour storage of BM, PBSC, and PBMNC products at refrigerated temperature maintains optimal cell viability and recovery. Anticoagulation with ACD-A is preferred over heparin to reduce lactic acid accumulation in the product media.

A changing time: the International Society for Cellular Therapy embraces its industry members.

The last decade has seen a dramatic rise in the development of new cellular therapeutics in a wide range of indications. There have been acceptable safety profiles reported in early studies using blood-derived and adherent stem cell products, but also an inconsistent efficacy record. Further expansion has been hindered in part by a lack of capital (both private and public) and delayed entry into the cell therapy space by large healthcare and pharmaceutical companies, those members of the industry most reliably able to initiate and maintain advanced-phase clinical trials. With recognition that the International Society for Cellular Therapy (ISCT) is uniquely positioned to serve the global translational regenerative medicine research community as a network hub for scientific standards and policy, the ISCT commissioned the establishment of an Industry Task Force (ITF) to address current and future roles for industry. The objectives of the ITF were to gather information and prioritize efforts for a new Commercialization Committee (CC) and to construct innovative platforms that would foster constructive and synergistic collaborations between industry and ISCT. Recommendations and conclusions of the ITF included that the new CC: (1) foster new relationships with therapeutic and stem cell societies, (2) foster educational workshops and forums to cross-educate and standardize practices, (3) create industry subcommittees to address priority initiatives, with clear benchmarks and global implementation, and (4) establish a framework for a greater industry community within ISCT, opening doors for industry to share the new vision for commercialization of cell therapy, emphasizing the regenerative medicine space.

Cellular engineering of HSV-tk transduced, expanded T lymphocytes for graft-versus-host disease management.

Engineering donor T lymphocytes with inducible 'suicide genes', such as herpes simplex virus thymidine kinase, has potential to improve safety and efficacy in allogeneic transplantation by facilitating management of graft-versus-host disease. Elective administration of a relatively nontoxic pro-drug would induce in vivo negative selection of engineered lymphocytes specifically, sparing other donor hematopoietic cells. The engineered cells must retain immunologic function, and undergo negative selection in response to clinically attainable plasma concentrations of pro-drug. The cell engineering process itself, typically involving activation, transduction, ex vivo expansion, and selection, must produce clinically useful numbers of genetically modified cells at high purity. We discuss development of a cellular engineering manufacturing process that yields transduced, expanded T lymphocytes meeting these requirements.