Abstract 4562: Activity of PARP1-selective inhibitor SNV-001 in models of HRD cancers as monotherapy and in combination

Abstract Current FDA approved poly (ADP-ribose) polymerase inhibitors (PARPi) inhibit both PARP1 and PARP2. Genetic studies indicate that loss of PARP1 is synthetic lethal with homologous recombination deficiency (HRD), including BRCA1/2 mutations, and PARP2 depletion may be linked to hematologic toxicity. To date, no first generation PARPi has been successfully combined with standard of care (SoC) agents in the clinic without significant reduction in dosing intensity because of overlapping toxicities. A selective inhibitor could potentially improve the therapeutic index and provide additional opportunities in combination strategies especially with drugs that are prone to myelosuppression. SNV-001 potently and selectively inhibits PARP1 in biochemical and cellular assays. SNV-001 inhibits PARylation in the low nanomolar range with over 500-fold selectivity against PARP2. SNV-001 did not inhibit any other PARP family member tested up to 10 uM in biochemical assays confirming its selectivity for PARP1. In human erythroid and myeloid colony formation assays, the IC50s of SNV-001 for both lineages were approximately 100-times higher than the target efficacious concentration based on the IC95 for inhibition of DLD1 (BRCA2 -/-) colony formation. In a subcutaneous MDA-MB-436 (BRCA1mut) xenograft model, oral administration of SNV-001 once daily resulted in a dose-dependent tumor regression. SNV-001 showed greater efficacy at lower doses compared to olaparib at 100 mg/kg or at equivalent doses of AZD9574. SNV-001 showed promising synergy with SoC chemotherapies or DDR inhibitors in cell proliferation assays. SNV-001 enhanced cytotoxicity of the DNA-damaging agent topotecan or carboplatin in Capan-1 (BRCA2mut) and HCC1395 (BRCA1mut) cells. Synergy was seen between SNV-001 and cell cycle check point inhibitors camonsertib (ATRi) or adavosertib (WEE1i) in DLD1 (BRCA2 -/-) and UWB1. 289 (BRCA1mut) cells, as DNA damage induced by PARP1 trapping relies on cell cycle modulation for repair. Combination of SNV-001 with polymerase theta inhibitor ART558 or USP1 inhibitor KSQ4279 exhibited synergistic effects in DLD1 (BRCA2 -/-) or UWB1. 289 (BRCA1mut) cells. These results suggest that inhibition of microhomology-mediated end-joining and translesion synthesis pathways may further exacerbate SNV-001-induced DDR in certain cellular contexts. In summary, the PARP1 selective inhibitor SNV-001 demonstrates potent antitumor activity and shows promising synergy between SoC chemotherapies or DDR inhibitors. Current data highlight a potential strategy for improving treatment efficacy and overcoming resistance. Further clinical investigations are warranted to validate this combination strategy. Citation Format: Zhentian Li, Qipeng Fan, Mingming Gao, Jun Pan, Liangxing Wu, Wenqing Yao, Phillip C. Liu. Activity of PARP1-selective inhibitor SNV-001 in models of HRD cancers as monotherapy and in combination 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 (6Suppl): Abstract nr 4562.