Abstract 1834: Discovery of a novel and highly selective PARP7 inhibitor for cancer immunotherapy

Abstract

Abstract Poly-ADP-ribose polymerase 7 (PARP7) is a member of the wider PARP enzyme family that modulate protein function by using nicotinamide adenine dinucleotide (NAD+) as a substrate to transfer an ADP-ribose monomer onto specific amino acid acceptor residues of target proteins. PARP7 acts as a key repressor of type I interferon (IFN) signaling. Its inhibition combats tumor regression by enhancing antitumor immunity that depends on STING pathway. Therefore, PARP7 is emerging as a promising drug target for new immunotherapy. Using structure-based drug design and optimization, we discovered a novel PARP7 inhibitor, HSN002066, with high inhibitory potency (Enzyme assay IC50 = 0.96 nM) and high selectivity for PARP7 over PARP1/2/12/5A/5B/10 (IC50 =163.4/4.7/345.2/1790/110.2/>10000 nM, respectively). In addition, HSN002066 has excellent ADMET profiles with CYPs inhibition, IC50 >10 μM, human LMS T1/2 > 60 min, hERG inhibition, IC50 > 30 μM,mouse oral bioavailability (F) 98.1%. Notably, HSN002066 and RBN-2397, the only PARP7 inhibitor currently in Ph 1/2 clinical development, displayed differentiated antiproliferative activities in cell line NCI-H1373 (IC50 are 387.8 nM and 15.2 nM, respectively). However, HSN002066 revealed remarkable antitumor effects as monotherapy (TGI 77% at 100 mg/kg) or combination with PD-1 antibody in CT-26 allograft model. The structure of HSN002066 was not presented and will not be disclosed at the time of presentation at AACR meeting. Citation Format: Xiaohui Liu, Ying Wang, Dongliang Xia, Wei Zhang, Shijie Tian, Yan He, Xuerong Feng, Xia Yang, Qi Zhang, Shiyi Jiang, Meifeng Wu, Jianfeng Deng, Yeye Wang, Yuxi Su, Min Yao, Weijiao Yuan, Xuedan You. Discovery of a novel and highly selective PARP7 inhibitor for cancer immunotherapy [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 1834.