Optimising and adapting perfusion feeds in serum-free medium to intensify CAR-T cell expansion in stirred-tank bioreactors

The <i>ex vivo</i> expansion of autologous chimeric antigen receptor (CAR) T cells to reach a therapeutic dose significantly prolongs manufacturing time and increases overall costs. The common use of animal- or human-derived serum in T cell expansion culture media further contributes to process variability, costs and introduces additional safety concerns. To address these challenges, this study focused on intensifying CAR-T cell expansion using perfusion processes in xeno-free (XF) and serum-free (SF) culture medium. The impacts of alternative tangential flow (ATF) perfusion rates, perfusion start times and donor variability were evaluated using a Design of Experiments (DOE) approach in the Ambr^® 250 High-Throughput Perfusion stirred-tank bioreactor. This allowed the identification of optimal combinations of perfusion parameters on a per-donor basis, enabling 4.5-fold improvements in final cell yields and over 50% reductions in the expansion time required to reach a representative CAR-T dose compared to a fed-batch process. Subsequent process development then established an adaptive perfusion strategy enabling 130 ± 9.7-fold expansions to achieve final cell densities of 33.5 ± 3 × 10⁶ cells/mL while reducing medium requirements by 11% without compromising CAR-T cell quality attributes compared to static well-plate cultures. Harvested cells predominantly expressed naïve and central memory markers, low levels of exhaustion markers, and maintained cytotoxicity and cytokine release <i>in vitro</i>. This study demonstrates the potential of optimising and adapting perfusion strategies in XF/SF-culture medium to enhance CAR-T cell yields, shorten expansion times and reduce medium consumption while addressing patient variability in clinical manufacturing. Key considerations for future implementation and improvement of adaptive perfusion feeds for clinical CAR-T manufacturing are also discussed.