Hocine, Ganbaatar, and Amador-Molina et al. developed an IL7Rα (CD127)-targeted chimeric antigen receptor (CAR) T cells and demonstrated their efficacy against T-ALL in vitro and in vivo, including in a patient-derived xenograft model using matched patient-derived CAR T cells. Low-affinity CAR T cells outperformed high-affinity cells, but maintained higher expression of CD127, putting them at risk of fratricide after tumor eradication. To reduce fratricide, genetic KO of CD127, a natural selection method, and co-culture with dasatinib (a tyrosine kinase inhibitor), during manufacturing were each tested, with dasatinib emerging as the most viable option.
Contributed by Lauren Hitchings
ABSTRACT: On the basis that T-cell acute lymphoblastic leukemia (T-ALL) cells overexpress IL7 receptor (IL7R), which promotes resistance to chemotherapy and disease relapse, here we develop IL7Rα (CD127)-targeted chimeric antigen receptor (CAR) T cells with low- and high-affinity single-chain variable fragments. We establish the antitumor efficacy of CD127 CAR against T-ALL cells in vitro, in female mouse models of T-ALL, and against blasts from patients with T-ALL using the patients' own T cells transduced with CD127 CAR. Antitumor efficacy is higher with low-affinity CAR T cells than high-affinity CAR T cells, albeit with fratricide of CAR T cells following eradication of CD127-overexpressing blasts. CRISPR-Cas9 knockout of CD127 eliminates fratricide at the risk of prolonged lymphopenia in vivo. To overcome fratricide, we investigate short-term ( < 7 days) co-culture with or without dasatinib, a tyrosine kinase inhibitor, versus a natural selection method (10 days) and demonstrate that co-culturing with dasatinib facilitates higher CAR T-cell yield, improved fitness, and preserved functionality. In vivo, dasatinib can be used to temporarily and reversibly suppress CAR T-cell activity. With this supporting translational data, we are initiating a trial with low-affinity CD127 CAR T cells for adult and pediatric patients with relapsed or refractory T-ALL.
