A novel chimeric antigen receptor containing a JAK-STAT signaling domain mediates superior antitumor effects

Introductory paragraph

The adoptive transfer of anti-CD19 chimeric antigen receptor (CAR)-engineered T cells has shown impressive clinical responses in patients with refractory B-cell malignancies ^{1– 7} . However, the therapeutic effects of CAR-T cells targeting other malignancies have not yet resulted in significant clinical benefit ^{8– 11} . Although inefficient tumor trafficking and various immunosuppressive mechanisms can impede CAR-T cell effector responses, the signals delivered by the current CAR constructs may still be insufficient to fully activate antitumor T cell functions. Optimal T cell activation and proliferation requires multiple signals, including T cell receptor (TCR) engagement (signal 1), costimulation (signal 2), and cytokine engagement (signal 3) ¹² . However, CAR gene constructs currently being tested in the clinic contain a CD3z (TCR signaling) domain and a costimulatory domain(s) but not a domain transmitting signal 3 ^{13– 18} . Here, we have developed a novel CAR construct capable of inducing cytokine signaling upon antigen stimulation. This new generation CD19 CAR encodes a truncated cytoplasmic domain of IL-2Rβ and a STAT3-binding YXXQ motif together with CD3z and CD28 domains (28-ΔIL2RB-z (YXXQ)). The 28-ΔIL2RB-z (YXXQ) CAR-T cells showed antigen-dependent JAK-STAT3/5 pathway activation, which promoted their proliferation and prevented terminal differentiation in vitro. The 28-ΔIL2RB-z (YXXQ) CAR-T cells demonstrated superior in vivo persistence and antitumor effects in both liquid and solid tumor models compared with CAR-T cells with a CD28 or 4-1BB domain alone. Taken together, these results suggest that our new generation CAR has the potential to demonstrate superior antitumor effects with minimal toxicities in the clinic. Clinical translation of this novel CAR is warranted.