Durable remission related to CAR-T persistence in R/R B-ALL and long-term persistence potential of prime CAR-T

CD19-targeted chimeric antigen receptor T lymphocytes (CAR-T) has demonstrated a high proportion of complete remission in the treatment of relapsed refractory acute B cell lymphoblastic leukemia (r/r B-ALL). It is of great clinical significance to explore which factors will impact long-term disease-free survival of patients with r/r B-ALL after CAR-T therapy without bridging bone marrow transplantation. Our study found that, in patients with r/r B-ALL without bridging transplantation, the patients' age; infusion dosage; whether they had undergone allo-stem cell transplantation before CAR-T therapy, using CD-19-targeted or CD19/CD22-dual-targeted CAR-T; whether there is fusion gene; tumor burden before therapy; and comorbidity had no significant relationship with their long-term disease-free survival. We found only that CAR-T persistence was highly correlated with patients' long-term disease-free survival. So, we further profiled CAR-T cells using single-cell sequencing and found that there is a specific T cell subset that may be associated with the long-term persistence of CAR-T. Finally, according to the single-cell sequencing results, we established cell production process named PrimeCAR, which shared common signaling pathways with the T cell subset identified. In the preliminary clinical study, prime CAR-Ts yield good persistence in peripheral blood of patients with B-ALL and lymphoma, without observing grade 2 or higher cytokine release syndrome.