Immunotherapy using chimeric antigen receptor modified T cells has proven to have a high response rate to patients with B cell malignancies, and chimeric antigen receptor T cell therapy is currently being studied in several hematology and solid tumor types. CAR-T cells are produced by removing T cells from a patient`s blood and modifying them to express chimeric antigen receptors, which reprogram the T cells to target tumor cells. As chimeric antigen receptor T cell therapy enters late-stage clinical trials and becomes the choice of more patients, the production process of chimeric antigen receptor T cell compliance with global regulatory requirements has become a topic of extensive discussion. In addition, the current challenge of using chimeras is to solve the antigen receptor T cell manufacturing process from a single institution to a large multi-site manufacturing center.
The generation of CAR-T cells requires several carefully executed steps and quality control tests are performed throughout the protocol. First, the process involves drawing blood from the patient using leukocyte removal, separating the white blood cells, and then returning to the rest of the blood circulation. After collecting a sufficient number of white blood cells, the white blood cell separation product enriches T cells. The process involves washing out the cells from a leukocyte separation buffer containing anticoagulant. The enrichment of lymphocytes can be accomplished by countercurrent centrifugal elutriation, which separates cells by size and density and maintains cell viability. The use of specific antibody bead conjugates or markers to separate T cell subpopulations at the CD4/CD8 composition level is an additional step that can be performed.
Although a program for the production of clinical-grade CAR T cells has been established, so far, CAR T cell therapy has only been used to treat a few hundred patients. When expanding this complex manufacturing process to treat more patients in larger trials in more clinical centers, the process should be carefully evaluated to ensure production efficiency without compromising the integrity and effectiveness of the final product. Since CAR T cells can be used to target multiple types of cancer, the production scale of vectors and CAR T cells will also depend on the incidence of each indication. Other considerations include generating consistent, high-quality vectors for predictable genetic modification of cells, understanding the long-term safety of gene therapy, and anticipated global regulatory issues.
The main challenge in expanding the production of CAR T cell therapy is the transition from a flexible process at a single academic institution to a highly controlled process that can be implemented in many collection, manufacturing and treatment sites. Therefore, effective coordination between the collection, manufacturing, and treatment locations involved is essential to ensure the correct handling of materials and the rational arrangement of patients throughout the treatment process. The successful development of the global manufacturing process of CAR T cells will depend on a deep understanding of the products and processes to establish the profile and key quality attributes of the target product.
For CTL019, the target product features include the qualities already discussed: target specificity, high-efficiency T cells, capable of strong expansion in the body and long-term durability. Using this product information, key quality attributes were explored. Cell number, transduction efficiency, growth rate, cell phenotype and functional analysis are all key quality attributes of CTL019, and these attributes have been well understood and controlled. The cell phenotype includes measurements such as the distribution of T cell subsets (helper or cytotoxicity, effector or memory, etc.) and functionality (cell killing, cytokine release, proliferation capacity, failure, apoptosis, etc.). These key quality attributes will be coordinated with process understanding to develop consistent manufacturing processes and control strategies to ensure product consistency. Examples include the percentage of CD3 + T cells in the product and the measurement of potency.
In view of the success of CAR T cells in the treatment of B cell malignancies in the United States, expanding the production capacity of CAR T cells will help to examine the safety and effectiveness of CAR T cell therapy in more patients around the world. However, when trying to introduce cell therapies with complex manufacturing processes to more international patient populations, many manufacturing and regulatory challenges need to be considered. Predicting regulatory and manufacturing problems before they arise, and proactively addressing them, will help speed up the process of bringing this promising treatment to more patients.
