Abstract 1821: Discovery of XNW21015, a novel, potent HPK1 inhibitor with excellent immune modulatory activity

Abstract Hematopoietic progenitor kinase 1 (HPK1), also known as MAP4K1, is a member of the STE20 family of serine/threonine kinases, and restrictedly expressed in hematopoietic cells. In T cells, HPK1 negatively regulated TCR signaling by phosphorylating the adaptor protein SLP76 on Ser376, which leads to the dissociation of the SLP-76/LAT signalosomes and downregulation of T cell priming and activation. HPK1 knockout (KO) or kinase-inactive (KI) mice spontaneously reject tumors with an enhanced immune response compared to wild-type ones. Thus, HPK1 is a novel immuno-oncology (I/O) target. In this work, we described the discovery of a potent HPK1 inhibitor starting from comprehensive SAR-based design with guidance from X-ray crystallography and computational modeling. These efforts led to identification of the potent azaindole inhibitor XNW21015, with excellent kinase selectivity and promising PK profile of low clearance and sufficient exposure for in vivo animal studies. XNW21015 dose-dependently inhibited phosphorylation of SLP76(Ser376) in vitro and in vivo in response to anti-CD3 agonist antibody, with concomitant enhancement in T cell activation. Oral administration of XNW21015 in mouse syngeneic tumor models showed favorable PK profile and robust anti-tumor activity as both single agent and in combination with immune checkpoint inhibitors. In a humanized PDX (patient-derived xenograft) model, XNW21015 enhanced tumor-infiltrated lymphocytes (TIL). In summary, we have discovered a novel, highly potent and selective HPK1 inhibitor XNW21015 as promising small molecule I/O agent, as monotherapy or in combination with immune checkpoint inhibitors. Citation Format: Yuchuan Wu, Rui Hao, Xi Chen, Xiao Liu, Yonghua Xie, Shihua Wang, Bingquan Gao, Jichun Wen, Zhenwei Wu, Wengui Wang, Haiyang Wei, Yonghan Hu, Xiaojun Liu, Meijie Le, Jing Qiang. Discovery of XNW21015, a novel, potent HPK1 inhibitor with excellent immune modulatory activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1821.