Impact of cellular composition and T-cell senescence of mononuclear cell concentrates on the manufacturing process of chimeric antigen receptor (CAR) T-cells.

Background: Apheresis procedure of autologous lymphocytes competent for proliferation and expansion is a crucial step in the production of chimeric antigen receptor (CAR) T-cells. Previous therapies or disease status prior to collection may negatively impact the collections.

Study design and methods: We performed a retrospective analysis with the aim to determine cellular factors in association with the collection of autologous T-cells and subsequent CAR T manufacturing toward tisagenlecleucel (tisa-cel). Between February 2019 and February 2022, 63 collections of 54 patients were performed for subsequent therapy with tisa-cel.

Results: We observed no difference in median CD3+ cell yields according to the number of prior therapy lines (>3 vs. ≤3, p = .335), prior treatment with bendamustine (p = .954) or marrow infiltration (p = .634). Fifty-six collections were sent for manufacturing, of which 22 (39%) resulted in manufacturing failures, namely terminations (n = 12) or out-of-specification events (n = 10). Collections resulting in manufacturing failures yielded significantly lower CD3+ (p = .005), CD3+CD4+ (p = .044), and non-senescent CD3+CD27+CD28+ (p = .003) counts. Multivariable analysis identified the absolute number of CD3+CD27+CD28+ cells as relevant, with a calculated cut-off of ≥34.58 × 10⁸ CD3+CD27+CD28+ cells for 89.5% probability of successful CAR T-cell production.

Discussion: In summary, we report a positive influence of a higher number of non-senescent Τ-cells on successful manufacturing. Further analyses are required to determine measures for further optimization of collection outcomes.