Abstract 4845: Preclinical evaluation of HWH340, a novel PARP inhibitor

Objective: Poly-ADP-ribose polymerase (PARP) participates in DNA repair, replication and transcription, and is important to maintaining genome stability and integrity. PARP inhibitors have proven to be efficacious in the clinic to treat BRCA-deficient cancers. PARP inhibitors may also be used as sensitizing agent in combination with other antitumor agents. The purpose of this study is to investigate in preclinical models the antitumor activity of HWH340, a novel potent and selective PARP inhibitor currently undergoing clinical investigation. Method: HWH340 was evaluated for its PARP1/2 enzymatic activity in corresponding enzyme assays and its cellular PARylation inhibitory activity in HCC1937 cells. The anti-proliferative activity and the synergistic effect in combination with temozolamide (TMZ) were evaluated in vitro in a BRCA-deficient cell line MDA-MB-436 and BRCA proficient cell line MDA-MB-231. Antitumor activity was evaluated by daily oral administration of in xenograft tumor models. Synergistic effect in combination with TMZ was also determined. The animal models used were PARP highly expressed patient-derived xenograft (PDX) model of small cell lung cancer (SCLC) LU-01-0547 and BRCA1/2-deficient CDX models of breast cancer MDA-MB-436 and pancreatic cancer CAPAN-1. Result: HWH340 displayed potent PARP1/2 enzymatic inhibitory activity with IC50 1.14 nM and 1.72 nM respectively. It also potently inhibited cellular PARylation in HCC1937 cell with IC50 2.77 nM. In BRCA proficient cell line MDA-MB-231, HWH340 showed no synergistic effect when combined with TMZ and a weak anti-proliferative activity with IC50 5.83 uM and 4.86 uM. In contrast, it displayed potent anti-proliferative activity and a synergistic effect in combination with TMZ with IC50 of 71 nM and 7 nM in the BRCA1/2-deficient MDA-MB-436 cells, respectively. HWH340 showed excellent in vivo antitumor efficacy in PARP overexpressed SCLC LU-01-0547 PDX model (TGI=81.69%@50mpk, QD). In BRCA-deficient breast cancer MDA-MB-436 CDX model, HWH340 showed potent antitumor efficacy as single agent (TGI=122% @12.5mpk, QD). In BRCA-deficient pancreatic cancer CAPAN-1 CDX model, it showed potent antitumor efficacy in combination with TMZ (TGI=79.61% @25mpk+ TMZ 30mpk, QD). Conclusion: HWH340 is a potent PARP inhibitor. Its antitumor activity in the preclinical tumor models together with its excellent pharmaceutical properties provide confidence that HWH340 may have high potential in the clinic for treatment of BRCA deficient solid cancers. Citation Format: Wenjie Sun, Yang Yue, Hailiang Chen, Ronghua Tu, Jie Shen, Gang Li, Guoqiang Ma, Zhixiang Zhang, Charles Z. Ding, Shuhui Chen. Preclinical evaluation of HWH340, a novel PARP inhibitor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4845.