Phase I Dose-Escalation Trial of CD19/CD20 Bispecific Chimeric Antigen Receptor (CAR) T-Cells for the Treatment of Relapsed or Refractory B-Cell Lymphomas and Chronic Lymphocytic Leukemia

Background:

Single-input anti-CD19 CAR T-cells have demonstrated clinical efficacy for relapsed or refractory (R/R) non-Hodgkin B-cell lymphoma (NHL) and chronic lymphocytic leukemia (CLL). Despite excellent response rates, over 50% of CD19 CAR T-cell recipients relapse. Preclinical data show engineering of bispecific anti-CD19/CD20 CAR T-cells via lentiviral transduction effectively targets tumor cells and overcomes antigen escape (Zah E et al., Cancer Immunol Res, 2016). Based on these promising preclinical results and the limitations of single-input anti-CD19 CARs, we investigated the bispecific anti-CD19/CD20 CAR naïve/memory T-cells in a phase I dose-escalation clinical trial for patients with R/R NHL/CLL (NCT04007029).

Methods:

This trial includes patients who have measurable disease after 2 lines of therapy for diffuse large B-cell lymphoma (DLBCL) and primary mediastinal B-cell lymphoma (PMBCL), and after 3 lines of therapy for mantle cell lymphoma (MCL), follicular lymphoma (FL), CLL and small lymphocytic leukemia (SLL). Eligible participants received lymphodepleting chemotherapy with fludarabine 30 mg/m² and cyclophosphamide 500 mg/m² for three days, followed by anti-CD19/CD20 CAR T-cell infusion. The CAR T-cell infusion will be given with standard "3+3" dose escalation to determine the maximum tolerated dose (MTD), with a dose range of 5 x 10⁷ to 6 x 10⁸ CAR-positive cells per patient.

Results:

To date, three patients received treatment on cohort 1 with 5 x 10⁷ CD19/CD20 CAR T-cells for R/R MCL, FL and PMBCL, with an average age of 49.3 (range, 29-60) and a mean of 3.7 prior regimens (range, 3-4). All 3 patients' lymphomas were CD19+/CD20+ on tissue biopsy prior to CAR infusion and all 3 received bridging chemotherapy. The infusion was well tolerated and no major infusion reactions occurred. Peak expansion was noted on day 14. No dose limiting toxicities were identified. The maximum grade CRS was 1 and there was no ICANS. At the 6.0-month cutoff date, 2 of the 3 patients remain in ongoing complete remission. Unfortunately, one patient developed progressive disease 0.5 months after CAR infusion, yet remains alive after treatment with immunotherapy. Both of the responders continue to demonstrate ongoing CAR T-cell persistence and B-cell aplasia by 3.0 and 6.0-month follow up, respectively.

Conclusions:

Here we demonstrate impressive responses in 2 of 3 patients at the 5 x 10⁷ CD19/CD20 CAR T-cell dosages. Bispecific CD19/CD20 CAR T-cell therapy appears to be safe and effective in patients with R/R NHL and CLL and obviates the challenges with the single antigen directed CARs by decreasing risk of target antigen loss and expression downregulation. A longer follow up period is required to determine the impact of modifying naïve/memory T cells and the durability of response. The trial continues to enroll patients and additional clinical and translational data are being collected on the initial patient cohort.