Chimeric antigen receptor (CAR) T cell therapy has advanced into commercially available treatments that have driven an influx of companies into the immunotherapy landscape. In a standard workflow, a patient’s (autologous) or donor’s (allogeneic) genetically engineered T cells must be expanded ex vivo for clinical use. Typically, T cell expansion is the longest and one of the most critical phases in the CAR T workflow.

Engineered T cells are sensitive to their microenvironment and growth conditions. These responses can lead to potential undesirable cellular changes, which pose production and quality control challenges that could ultimately delay patient treatment.

One of the main objectives during the expansion phase is to maintain “younger”, less differentiated memory cell phenotypes. Figure 1 illustrates the spectrum of T cell differentiation with the less differentiated, most therapeutically desirable central memory T cells (TCM) on the left and less desirable, more mature effector memory T cells (TEM) and effector T cells (TEFF) on the right. Surface markers such as CD62L, CCR7, and CD28 are not present when T cells differentiate and transition toward the TEFF cell populations and become less efficacious.