Harnessing the CD2 axis to broaden and enhance the efficacy of CAR T-cell therapies

ABSTRACT: Patients with T-cell lymphomas and leukemias have overall poor outcomes because of the lack of targeted and effective treatments, particularly in the relapsed and refractory settings. The development of chimeric antigen receptor (CAR) T cells against T-cell neoplasms is limited by a lack of discriminating T-cell antigens that allow for effective antitumor responses while preventing CAR T-cell fratricide. We hypothesized that targeting CD2, a pan-T-cell antigen, with anti-CD2 CAR T cells engineered to lack CD2 expression (CART2) would improve manufacturability and preclinical efficacy. Optimized CD2-knockout CART2 cells, generated using CRISPR-Cas9, eradicated primary patient-derived CD2+ hematological neoplasms in vitro and in vivo, secreted effector cytokines, and exhibited adequate proliferative capacity. Nevertheless, CD2 has a key costimulatory function, and its deletion could lead to CAR T-cell dysfunction. Therefore, we tested the role of the CD2:CD58 axis in CAR T cells, using the anti-CD19 CART models. We demonstrate that CD2 loss attenuates CART19 efficacy by reducing avidity for tumor antigen, costimulation, and ultimately in vivo activity. Analogously, we show that tumor CD58 loss reduces CART19 efficacy. To overcome this issue, we developed a novel programmed cell death protein 1 (PD-1):CD2 switch receptor that rescues intracellular CD2 signaling, particularly when programmed death-ligand 1 is engaged, thereby improving in vivo outcomes. Collectively, we studied the role of CD2 both as a target for CAR T-cell therapy and as a critical costimulatory protein, whose signaling can be rescued using the PD-1:CD2 switch receptor. This receptor can be incorporated into CAR T cells and provides an effective strategy to overcome CD2-signaling deficiencies.