Abstract LB031: Discovery and Characterization of HH100937, a potent and selective SOS1 inhibitor demonstrates synergistic efficacy in combination with KRAS/MAPK therapies

Abstract Besides marketed inhibitors targeting KRAS G12C, novel therapies are needed to effectively treat cancer patients harboring other KRAS mutations. SOS1, a guanine nucleotide-exchange factors (GEFs), plays a critical role in catalyzing the conversion of KRAS from its GDP- to GTP-bound form, regardless of KRAS mutation status and represents a promising therapeutic target for all KRAS-driven tumors. Up to date, several SOS1 inhibitors have entered early phase clinical trials. But a more potent SOS1 inhibitor with improved drug-like properties is still needed to prove efficacy as monotherapy or in combination with other drugs targeting the KRAS/MAPK pathway. We discovered a potent SOS1 inhibitor, HH100937 that effectively disrupted the interaction between SOS1 and wild-type KRAS or with G12C, G12D or G12V mutations. HH100937 exhibited lower IC50s than BI-3406 and MTRX0902 in blocking ERK phosphorylation and cancer cell proliferation, leading to better anti-tumor efficacies in xenografts than reference compounds at same doses. HH100937 also showed synergistic effect with AMG510 in cancer cells with KRAS G12C mutation but refractory to AMG510. The combination of HH100937 and AMG510 in xenografts led to tumor regression in all mice, while some tumors did not response well to AMG510 monotherapy. Our SOS1 inhibitor also exhibited synergistic effect with HH2710, a clinical-stage ERK inhibitor, in a broad panel of cancer cells with KRAS mutations. The pharmacological potency of HH100937 was highly selective over SOS2, other kinases tested or other targets in a safety panel of 47 targets. HH100937 was well tolerated in 28-day DRF study in rats and dogs up to 250 mg/kg QD and 30 mg/kg QD, respectively. The AUC of drug exposure in DRF studies was approximately three to six times higher than that at the efficacious dose. HH100937 also showed favorable DMPK properties in mice, rats and dogs, and acceptable safety profiles in vitro. Taken together, HH100937 is a highly potent and selective SOS1 inhibitor with better anti-tumor activities than some SOS1 inhibitors at clinical stage. It can be developed as mono therapy or in combination with other KRAS/MAPK targeting therapies. Citation Format: Qing Xie, Dongsheng Li, Shujuan Jiang, Jie Zhu, Songda Yu, Maozhi Yang, Yalei Cai, Lei Liu, Bing Yu, Wangyang Tu, Yixiang Zhang, Leping Li. Discovery and Characterization of HH100937, a potent and selective SOS1 inhibitor demonstrates synergistic efficacy in combination with KRAS/MAPK therapies abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (7Suppl): Abstract nr LB031.