Issue link: https://www.e-digitaleditions.com/i/1248960
Pharmaceutical Technology BIOLOGICS AND STERILE DRUG MANUFACTURING 2020 33 cell banking and cell characterization to support scale up. This includes establishing and testing the working cell bank (WCB) and cells at the limit of in-vitro cell age (LIVCA) separate from the original master cell bank (MCB). Bulpin points out that the specific requirements for the detection of contaminants at the WCB and LIVCA level are laid out in relevant regulations and guidelines for advanced therapy medicinal products (ATMPs). These requirements are similar to the requirements for the MCB, with less testing required at the WCB level. "In particular, the risk of introducing contaminants during scale-up must be addressed through testing, including the detection of human viruses, bacteria, fungi, mycoplasma, and pyrogens," he says. The requirements are similar for controlling the vector material and associated production cells. Rig- orous testing should be performed on all starting and in-process materials, such as plasmids, vector produc- tion cell banks, vector bulk harvests, and purified bulk, says Bulpin. It is at this stage that specific risks, such as the presence of replication-competent viral vectors in bulk harvest and transduced cells must be addressed, he explains. Cell purity validation When moving from clinical to commercial-scale manufacturing for a cell therapy, other consid- erations must be taken into account, and phase- appropriate validations used to assess the mate- rials. During early clinical phases, for example, assays used for the release of clinical material should be suitably validated and qualified in the presence of a test matrix that uses a single batch of material. For late-stage or commercial-scale development, assays should be fully validated and qualif ied in the presence of a test matrix using a minimum of three batches under a for- mal product-specific qualification, Bulpin says. A battery of tests is generally used to assess and validate the purity of the cell therapy end-product. Tests include PCR assays for viral pathogens and my- coplasma and a sterility assay for bacteria and fungi. For cell therapies that have been transduced using a viral vector, the risk of replication-competent virus being present must be addressed, Bulpin asserts. This is typically done using a detector cell-based in-vitro cultivation assay with a vector-specific endpoint test. "Furthermore, purity of the cell therapy must be au- thenticated to the level of the individual. Finally, as- says used for lot release of clinical or commercial ma- terial should be suitably validated and qualified in the presence of test matrix," he concludes. Advanced assays The complex nature of cells and cell-to-cell interac- tions calls for advanced assays to help detect even minute levels of contamination and to validate their purity. The most advanced analytical as- says that are used for detecting contamination in human cell sources include novel molecular sen- sitive techniques with broad molecular detection capabilities. Examples include deep sequencing/ next-generation sequencing/high-throughput se- quencing, degenerate polymerase chain reaction for whole virus families or random priming meth- ods, hybridization to oligonucleotide arrays, and mass spectrometry, according to Bulpin. References 1. D. Clarke, et al., Cytotherapy 18 (9) 1063–1076 (2016). 2. ARM, "Cell Therapy," alliancerm.org/technologies/cell-therapy, accessed March 20, 2020. 3. R. Hansen, "Reducing the Risk of Bio-contamination in Gene, Cell and CAR-T Therapy," Bioquell.com/news, August 2018. 4. Microrite, "Mitigating Contamination Challenges in Cell Based Re- generative Therapies," microrite.com, accessed March 13, 2020. PT