The U.S. Food and Drug Administration (FDA) has issued Chemistry, Manufacturing, and Control (CMC) recommendations for Investigational New Drug (IND) applications for human investigational gene therapies. The focus of the guidance is on SISPQ (safety, identity, strength, purity and quality), critical quality attributes (CQAs) and risk assessment. These apply to new cell/gene therapy products that have been developed in recent years. The FDA’s requirements, updated in January 2020, cover critical factors such as:
- Specification/characterization of manufacturing materials
- Filing and submission practices (i.e. eCTD or not)
- Manufacturing processes/procedures
- Product testing considerations
Cell and Gene Therapy (CGT) (a.k.a. ATMPs or Advanced Therapy Medicinal Products) has advanced significantly in recent years. After decades of work, new gene therapy products have been approved by the FDA and brought to market. This has permitted learning opportunities for the industry and regulators. The original 2008 guidance on CMC has been superseded with industry guidance in 2020, entitled “Chemistry, Manufacturing, and Control (CMC) Information for Human Gene Therapy Investigational New Drug Applications (INDs).”
Human gene therapy works by altering genetic sequences or by transcribing or translating genetic material transferred in the process. Cell therapy is the transfer of cells into a patient to treat or cure a disease, which works in several ways. Examples include blood transfusions or the process of removing cells from the body, introducing a new gene or correcting a defective one, and reintroducing the cell into the body.
In 2017, the FDA approved three new gene therapy products, including:
- KYMRIAH: Developed by Novartis, it became the first gene therapy product to treat acute lymphoblastic leukemia in patients up to 25 years old, using genetically modified autologous T cells.
- YESCARTA: Developed by GileadKite Pharma, it uses modified T cells to treat adults with large B-cell lymphoma (relapsed or refractory).
- Luxturna: A genetically modified virus developed by Spark Therapeutics, it delivers a healthy gene into the eyes of patients diagnosed with retinal dystrophy, an inherited form of vision loss.
Current estimates indicate that there are more than 289 novel gene and cell therapy products at various stages of development from pre-IND thru Phase III. Below is an overview of key elements of the FDA’s specific CMC requirements for CGT and IND development.
Specification and Characterization of Manufacturing Materials
Developing CGT products comes with the significant challenge of selecting the most suitable materials. Not only must they be high-grade, but also compliant and include regulatory documentation that supports their efficacy. Key aspects of manufacturing materials to consider include:
- Vectors: A vector, or vector construct, is a means by which genes are transferred into cells. The FDA requires that the vector be identified including the gene insert, regulatory regions, and other elements relevant to the IND. Details of changes to the vector or its construct must be documented throughout the development of the product.
- Cells: The cells used can be from the patient (autologous) or from another person (allogeneic). In addition to providing detailed cell processing descriptions and gene modification procedures, documentation must include descriptions of cell and tissue type. Testing of allogeneic cells for HIV, HBV, HCV, syphilis, and CJD is required as well. The method used to mobilize cells, or collect them from bone marrow, must be explained, as should the history, frequency, source, derivation, and characterization of testing at master cell banks and working cell banks.
- Reagents: Reagents are used in manufacturing processes and are not intended to be in the final product. It is expected that the developer will have methods to demonstrate the clearance of these reagents to levels ensuring patient safety in the final product.
- Excipients: Excipients are the inactive components intended to be part of the final product. Details and demonstrated control of these components is also critical as they may impact efficacy or safety of the product.
Manufacturing Process and Procedures
Manufacturing of these therapeutics to support IND studies and submissions involves many materials, procedures, and challenges. The FDA requires thorough descriptions of processes and procedures, process controls, and testing. Here are some other required considerations during the manufacturing process:
- Cell Culture (Vector Production): All steps to manufacturing and inserting a gene therapy vector must be thoroughly illustrated. Documentation should include details on the gene, promoters and selection markers used, and all steps involving cell culture, harvesting, vector purification, and in-process testing. The entire vector must be sequenced for vectors less than 40 kilobases; for larger vectors, minimum sequencing should include the gene insert, flanking regions, and any modified region.
- Genetically Modified Cell Production: Producers of gene therapy products must describe their method of cell processing, including the source material, collection of cellular material, and storage at the collection site. A description of shipping and handling procedures must be included. Cell selection, isolation, and enrichment steps are required in the documentation, as are cell expansion conditions, hold times, and transfer steps as well as any cell harvest and purification procedures used.
- Irradiated Cells: The FDA requires details on the irradiator source to be provided, including calibration of the source. Data supporting proof the irradiated cells have been rendered unable to replicate, yet still retain the desired characteristics, must be included as well.
- Filling, Storage, and Transportation: Documentation of process controls associated with the filling, storage, and shipping of the product must be provided. This includes a description of the container closure system used, the materials it’s made of, and whether the container or closure has been approved or cleared for use with similar products. The FDA recommends using materials that provide protection from moisture, gases, and light, and that are safe and perform well under expected storage and transport conditions.
- Final Formulation: Container closures should be compatible with the formulation, with issues such as leaching and adsorption to the container having been addressed before the filling stage. As for the formulation itself, all sources, vendors, and component concentrations must be accurately identified.
Testing is mandatory during gene/cell therapy product development. In order to meet the established criteria, your product must at a minimum be examined by the following tests or test categories:
- Microbial Testing: At various steps in the manufacturing process, sterility testing should be performed. This should be done before a product is frozen, purified, or cultured. Repeat sterility testing may be needed if the product is manipulated after thawing. Rapid microbial testing can be performed if product stability is a concern following the thawing process. Testing methods include:
- Mycoplasma testing: Is recommended to detect contamination at any manufacturing stage. Either the culture or rapid PCR method may be used.
- Adventitious agent testing: Required for the final product and includes vitro viral and vivo viral testing. Antibody production tests can be used to detect CMV, HIV, HBV, B18, and other viruses, while reverse transcriptase assays and electron microscope analysis can be used to test for retroviruses.
- Identity: The FDA recommends a final cell product undergoes an identity test if it is ex vivo genetically modified. At this stage, an assay to measure the presence of vector material should be performed. An assay for cell surface markers or other specifics pertaining to the sample is also recommended. Other identity tests include expression assays, vector genome, sequencing, and restriction digest testing. Final tests should identify all contents of the final labeled product.
- Purity: Includes testing for pyrogenicity, endotoxins, residual contaminants, antibodies, serum, and solvents. For many of the common safety tests, there are compendial tests that are preferred. Residual contaminants may include host cell DNA, RNA, and proteins, cell debris, cytokines, and growth factors. In addition, there are standard acceptance limits based on dosing which are recommended.
- Potency: Potency assays (established and validated) are typically part of release testing for materials used in phase three clinical trials. These methods should represent the mode of action (MOA) of the drug and be quantitative in nature. There should be a means to measure the expressed product and not the vector. Prior to Phase III assays that are not as well defined may be used including those which quantify the gene therapy vector expression. While the FDA doesn’t require potency to be measured in early phase trials, it is recommended to determine dosage using appropriate mechanisms.
- Viability: The FDA recommends a minimum viability of 70% for ex vivo genetically modified cells. When this level cannot be achieved, manufacturers can submit data to support and demonstrate the effectiveness of a product with a lower viability specification. The main concern is whether dead cells and cell debris affect a product’s administration and therapeutic effect.
- Cell Number/Dose: With any genetically modified cell therapy, the final product should specify the minimum number of viable cells. In the case of gene vectors, the dose should be described as a concentration of plasmid DNA, a viral particle number, or titer. Dose should be determined prior to any clinical study and is an important aspect of a drug product’s specifications.
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BioAgilytix provides testing services to support drug development and clinical research for biotechnology and pharmaceutical companies around the world. Capabilities include large molecule bioanalysis, clinical assays, diagnostics, and viral and antibody testing.
Our research team is current on all the latest recommended CMC requirements in supporting the manufacture of new CGT and IND products. From sample analysis (at any phase of development) to lot release testing, we support every stage of our clients’ workflow. To learn more or partner with us, contact BioAgilytix today at our USA headquarters: 919-381-6097.