Nevala, Wendy K

Abstract The recent FDA approval of the first T-cell receptor–engineered (TCR) T-cell cancer therapy has solidified the treatment as a viable therapeutic strategy. However, only a fraction of patients who received this treatment achieved substantial and long-lasting responses, highlighting the need to understand the molecular underpinnings of these responses and develop more effective strategies to improve this therapy. Previous research has demonstrated that the activation of myeloid differentiation primary response 88 (MyD88) signaling in tumor-specific T cells functions as a robust costimulatory signaling pathway that promotes effective antitumor T-cell responses. In this study, we developed a strategy for improving TCR T-cell therapies by creating a synthetic TCR in which the intracellular domain of CD3ζ and a modified MyD88 are appended to the β-chain of a tumor-reactive TCR. The β:CD3ζ:MyD88 TCR activated MyD88 signaling in a tumor antigen/TCR-specific manner, and β:CD3ζ:MyD88 TCR T cells exhibited enhanced functionality and a reduced propensity to become exhausted. Furthermore, MyD88 signaling promoted T-cell persistence and expansion in vitro. In vivo, tumor-infiltrating β:CD3ζ:MyD88 TCR T cells skewed the immunosuppressive tumor microenvironment toward a less immunosuppressive state. Finally, β:CD3ζ:MyD88 TCR T cells substantially delayed tumor growth kinetics in a melanoma model. These findings introduce an approach for improving TCR-dependent T-cell responses by directly appending signaling domains to the full-length TCR and exemplify the utility of activating MyD88 signaling in tumor-specific T cells. Significance: A chimeric β:CD3ζ:MyD88 TCR reduces exhaustion and improves antitumor T-cell responses, overcoming the limited efficacy of current TCR-engineered T-cell cancer therapies.

Abstract The receptor tyrosine kinase AXL is a member of the TYRO3, AXL, and proto-oncogene tyrosine-protein kinase MER family and plays pleiotropic roles in cancer progression. AXL is expressed in immunosuppressive cells, which contributes to decreased efficacy of immunotherapy. Therefore, we hypothesized that AXL inhibition could serve as a strategy to overcome resistance to chimeric antigen receptor T (CAR T)–cell therapy. To test this, we determined the impact of AXL inhibition on CD19-targeted CAR T (CART19)–cell functions. Our results demonstrate that T cells and CAR T cells express high levels of AXL. Specifically, higher levels of AXL on activated Th2 CAR T cells and M2-polarized macrophages were observed. AXL inhibition with small molecules or via genetic disruption in T cells demonstrated selective inhibition of Th2 CAR T cells, reduction of Th2 cytokines, reversal of CAR T-cell inhibition, and promotion of CAR T-cell effector functions. AXL inhibition is a novel strategy to enhance CAR T-cell functions through two independent, but complementary, mechanisms: targeting Th2 cells and reversing myeloid-induced CAR T-cell inhibition through selective targeting of M2-polarized macrophages.