Abstract 5493: Activity of RP12146, a novel, selective, and potent small molecule inhibitor of PARP 1/2, in solid tumors

Abstract

Abstract Introduction: The Poly (ADP-ribose) polymerase (PARP) family plays an important role in the regulation of transcription, apoptosis and DNA damage response. Several PARP inhibitors have been approved for the treatment of BRCA-mutated ovarian, breast and pancreatic cancer. Through ‘synthetic lethality’, the applicability PARP inhibitors can be expanded to cancers beyond the well-defined BRCA defects either as monotherapy or in combination with established therapy across various solid tumor types. Herein, we describe the efficacy of RP12146 as a single agent and in combination with approved therapies in preclinical models of solid tumors. Methods: Enzymatic potency was evaluated using a PARP Chemiluminescent Activity Assay Kit (BPS biosciences). Cell growth was determined following incubation with RP12146 as a single agent or in combination with approved agents in various solid tumor cell lines. Apoptosis was evaluated following incubation of cell lines with compound for 48 or 72 h, subsequent staining with Annexin-V-PE and 7-AAD, and analysis by flow cytometry. Anti-tumor potential of RP12146 as a single agent or in combination with chemotherapeutic agents was tested in OVCAR-3 and NCI-H69 Xenografts. Expression of downstream PAR, PARP-trapping, and cleaved PARP expression were determined in cell lines and xenograft tumor samples by Western blotting. Plasma and tumor concentration of RP12146 in NCI-H69 xenograft samples were also determined. Results: RP12146 demonstrated equipotent inhibition of PARP1 (0.6 nM) and PARP2 (0.5 nM) with several fold selectivity over the other members of the PARP family. Compound caused a dose-dependent growth inhibition of both BRCA mutant and non-mutant cancer cell lines with GI50 in the range of 0.04 µM to 9.6 µM. Combination of RP12146 with Temozolomide, Topotecan, Lurbinectedin, and Abemaciclib demonstrated either additive or synergistic effects manifested by an inhibition in growth of solid tumor cell lines. RP12146 exhibited anti-tumor potential with TGI of 28% and 21.8% as a single agent in OVCAR-3 and NCI-H69 Xenograft model respectively. In NCI-H69 xenograft model, RP12146 in combination with cisplatin exhibited TGI of 69.3 %. Conclusion: Data demonstrate the therapeutic potential of RP12146 as single agent and in combination in solid tumors. RP12146 is currently being evaluated in Phase 1 clinical trials in patients with locally advanced or metastatic solid tumors (NCT05002868). Citation Format: Srikant Viswanadha, Satyanarayana Eleswarapu, Kondababu Rasamsetti, Haritha Polimati, Sridhar Veeraraghavan, Swaroop Vakkalanka. Activity of RP12146, a novel, selective, and potent small molecule inhibitor of PARP 1/2, in solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5493.