Abstract 2608: Pre-clinical evaluation of small molecule CHK2 inhibitor, ART-122 combined with olaparib in BRCA wild type tumors

Abstract Background: PARP inhibitors are widely used for BRCA-mutant cancers, but often tumors become resistant to PARP inhibitors. The resistance develops through various mechanisms, including BRCA1/2 reversion mutation. Several publications have suggested that CHK2 inhibition could help overcome the resistance to PARP inhibitors. We discovered a novel small molecule CHK2 inhibitor, ART-122, and conducted a series of experiments to explore the rationale for combining a PARP inhibitor and ART-122 to treat the BRCA wild-type ovarian and breast tumors. Results: In the LanthaScreen࣪ Kinase assay, ART-122 was shown to have the IC50 values of 0.57 nM and 10.85 nM, for CHK2 and CHK1, respectively. We observed the strong synergy between ART-122 and olaparib in the mouse xenograft model using the MDA-MB-231 cancer cells (BRCA1/2 wild type, triple-negative breast cancer cells). Animals were treated with 50 mg/kg olaparib on days 1-5, 30 mg/kg ART-122 on days 1-2 each week for 3 weeks, or both therapies. The result demonstrated approximately 41% reduction in tumor volume in mice treated with the combination therapy compared to the vehicle group. Animals treated with either of the single-agent therapies showed tumor growth similar to the vehicle group. We did not observe apparent toxicity or significant body weight differences among the animals. Additionally, the synergism between ART-122 and olaparib was confirmed in other cancer cell lines, including several BRCA wild-type and BRCA mutant cells lines such as CaOV3, SK-OV-3, UWB1.289, UWB1.289 with BRCA overexpression, HCC1937, MDA-MB-436, and MCF7. Conclusion: The combination of ART-122 and Olaparib demonstrated a synergistic effect in BRCA wild-type ovarian and breast tumor cell lines. In the mouse xenograft model, the CHK2 inhibitor ART-122 sensitized BRCA1/2 wild-type tumor cells MDA-MB-231 to olaparib treatment. The data provide a strong rationale for the further development of ART-122 as a therapeutic agent. Citation Format: Taegon Baik, Chaeun Park, Young Woo Kang, Danny Joh, Ha-Young Lee, Sojung Park, Supyong Hwang, In Ki Kim, Jong Oh Kim. Pre-clinical evaluation of small molecule CHK2 inhibitor, ART-122 combined with olaparib in BRCA wild type 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 2608.