Anti-CD37 CAR-T (The General Hospital Corp)

We report a first-in-human clinical trial using chimeric antigen receptor (CAR) T cells targeting CD37, an antigen highly expressed in B- and T-cell malignancies. Five patients with relapsed or refractory CD37+ lymphoid malignancies were enrolled and infused with autologous CAR-37 T cells. CAR-37 T cells expanded in the peripheral blood of all patients and, at peak, comprised >94% of the total lymphocytes in 4 of 5 patients. Tumor responses were observed in 4 of 5 patients with 3 complete responses, 1 mixed response, and 1 patient whose disease progressed rapidly and with relative loss of CD37 expression. Three patients experienced prolonged and severe pancytopenia, and in 2 of these patients, efforts to ablate CAR-37 T cells, which were engineered to coexpress truncated epidermal growth factor receptor, with cetuximab were unsuccessful. Hematopoiesis was restored in these 2 patients after allogeneic hematopoietic stem cell transplantation. No other severe, nonhematopoietic toxicities occurred. We investigated the mechanisms of profound pancytopenia and did not observe activation of CAR-37 T cells in response to hematopoietic stem cells in vitro or hematotoxicity in humanized models. Patients with pancytopenia had sustained high levels of interleukin-18 (IL-18) with low levels of IL-18 binding protein in their peripheral blood. IL-18 levels were significantly higher in CAR-37–treated patients than in both cytopenic and noncytopenic cohorts of CAR-19–treated patients. In conclusion, CAR-37 T cells exhibited antitumor activity, with significant CAR expansion and cytokine production. CAR-37 T cells may be an effective therapy in hematologic malignancies as a bridge to hematopoietic stem cell transplant. This trial was registered at www.ClinicalTrials.gov as #NCT04136275.

Chimeric antigen receptor (CAR) T cells have emerged as a novel form of treatment of patients with B-cell malignancies. In particular, anti-CD19 CAR T-cell therapy has effected impressive clinical responses in B-cell acute lymphoblastic leukemia and diffuse large B-cell lymphoma. However, not all patients respond, and relapse with antigen loss has been observed in all patient subsets. Here, we report on the design and optimization of a novel CAR directed to the surface antigen CD37, which is expressed in B-cell non-Hodgkin lymphomas, in chronic lymphocytic leukemia, and in some cases of cutaneous and peripheral T-cell lymphomas. We found that CAR-37 T cells demonstrated antigen-specific activation, cytokine production, and cytotoxic activity in models of B- and T-cell lymphomas in vitro and in vivo, including patient-derived xenografts. Taken together, these results are the first showing that T cells expressing anti-CD37 CAR have substantial activity against 2 different lymphoid lineages, without evidence of significant T-cell fratricide. Furthermore, anti-CD37 CARs were readily combined with anti-CD19 CARs to generate dual-specific CAR T cells capable of recognizing CD19 and CD37 alone or in combination. Our findings indicate that CD37-CAR T cells represent a novel therapeutic agent for the treatment of patients with CD37-expressing lymphoid malignancies.