Abstract 2654: HPK1 inhibits CD8+ T cell effector gene expression following T cell activation

Abstract Hematopoietic progenitor kinase 1 (HPK1) has been shown to act as a negative regulator of T cell receptor signaling and of subsequent effector T cell function. Inhibiting HPK1 to enhance T cell activity has emerged as a promising strategy for cancer immunotherapy. Upon T cell receptor engagement, the kinase domain of HPK1 is activated and targets components of the T cell receptor (TCR) signaling pathway for degradation, including SLP76. However, the molecular events connecting HPK1 kinase activity to observed T cell functions downstream of proximal TCR signaling are not well understood. Through transcriptional profiling of HPK1-kinase-dead (HPK1-KD) versus wild-type CD8+ T cells following an acute, attenuated Listeria monocytogenes infection, we observed increased expression of many genes associated with T cell activation and effector function, including changes in expression of several key transcription factors and their targets. Upon activation, HPK1-KD T cells, as well as T cells treated with our small-molecule HPK1 inhibitor, produce higher levels of a wide range of effector cytokines in vitro and in vivo. Treatment of mice with the HPK1 inhibitor also inhibited tumor growth in several syngeneic tumor models. These data expand our understanding of the role of HPK1 in inhibiting CD8+ T cell effector programs, and, importantly, the impact of HPK1 inhibitors on T cell function. Citation Format: Rachel Y. Ames, Rongqi Zhao, Parker Mace, Adam Grant, Guorui Xie, Heather Milestone, Molly Grandcolas, Eva Fang, Nicolae Kiosea, Stephen Wong, Martin Brovarney, Scott Jacobson, Danilo Nebalasca, Jorge Arguello, Blanca Gomez, Hiranmayee Kandala, Michelle Y. Ko, Lan Nguyen, Omar Robles, Grant Shibuya, Anton A. Shakhmin, Parcharee Tivitmahaisoon, Vi-Anh Vu, Ashkaan Younai, Mikhail Zibinsky, Babu Subramanyam, Daniel Poon, Mohsen Sabouri Ghomi, David J. Wustrow, Paul D. Kassner, George E. Katibah, Dirk G. Brockstedt. HPK1 inhibits CD8+ T cell effector gene expression following T cell activation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2654.