Optimization of therapeutic T cell expansion in G-Rex device and applicability to large-scale production for clinical...

Our center performs experimental clinical studies with advanced therapy medicinal products (ATMPs) based on polyclonal T cells, all of which are currently expanded in standard T-flasks. Given the need to increase the efficiency and safety of large-scale T cell expansion for clinical use, we have optimized the method to expand in G-Rex devices both cytokine-induced killer cells (CIKs) from peripheral or cord blood and blinatumomab-expanded T cells (BETs). We show that the G-Rex reproducibly allowed the expansion of >30 × 10⁶ CD3⁺ cells/cm² of gas-permeable membrane in a mean of 10 to 11 days in a single unit, without manipulation, except for addition of cytokines and sampling of supernatant for lactate measurement every 3 to 4 days. In contrast, 21 to 24 days, twice-weekly cell resuspension and dilution into 48 to 72 T-flasks were required to complete expansions using the standard method. We show that the CIKs produced in G-Rex (CIK-G) were phenotypically very similar, for a large panel of markers, to those expanded in T-flasks, although CIK-G products had lower expression of CD56 and higher expression of CD27 and CD28. Functionally, CIK-Gs were strongly cytotoxic in vitro against the NK cell target K562 and the REH pre-B ALL cell line in the presence of blinatumomab. CIK-Gs also showed therapeutic activity in vivo in the Ph⁺ pre-B ALL-2 model in mice. The expansion of both CIKs and BETs in G-Rex was validated in good manufacturing practices (GMP) conditions, and we plan to use G-Rex for T cell expansion in future clinical studies.