Abstract 239: RCZY-690 and RCZY-680: Novel, highly potent, and orally bioavailable, tri-complex pan RAS-MULTI(ON) inhibitors with distinctive oral pharmacokinetic profiles, exhibiting broad anti-tumor activities in CDX models

Abstract Alterations in RAS proteins, including KRAS, HRAS, and NRAS, are common in cancer. KRAS mutations drive 85% of RAS-driven cancers, including lethal types like pancreatic ductal adenocarcinoma (PDAC), non-small-cell lung cancer (NSCLC), and colorectal cancer (CRC). These mutations impair GTP hydrolysis, locking RAS in an active GTP-bound state that promotes unchecked cell proliferation and survival. Although KRAS G12C inhibitors like sotorasib and adagrasib show promise for NSCLC, resistance develops rapidly, and effective therapies are still lacking for over 85% of RAS-driven or RAS-amplified cancers. Herein, we report RCZY-690 and RCZY-680 as novel and potent tri-complex RAS-MULTI(ON) inhibitors. These compounds form a tri-complex with active GTP-bound RAS proteins and cyclophilin A (CyPA) through a RAS-targeting strategy pioneered by Revolution Medicine. This approach, exemplified by the lead compound RMC-6236, has shown promise in KRAS-mutant PDAC and NSCLC patients in phase 1 study. RCZY-690 and RCZY-680 demonstrated high binding affinity to CyPA, as confirmed by surface plasmon resonance assays, and potent nanomolar EC50 values for binding to CyPA and KRAS mutants (G12C, G12V, G12D) in HTRF assays. Both compounds achieved potent IC50 values in disrupting interactions between NRAS, HRAS, and various KRAS subtypes (e.g., G12C, G12D, G12V, G12R, G12S, G13C, G61L) with the CRAF-RAS binding domain, as determined by HTRF. Their efficacy in blocking the RAS/RAF/MAPK pathway was demonstrated by sub-nanomolar IC50 values for suppressing p-ERK in cancer cell lines with diverse RAS mutations, including HPAC and Capan-2. CellTiter-Glo assays further revealed sub-nanomolar IC50 values for cellular cytotoxicity across multiple RAS-mutant human cancer cell lines. As expected, RCZY-690 and RCZY-680 were inactive in BRAF V600E-mutated and RAS-independent cancer cell lines. Both compounds exhibited favorable in vitro ADME properties. They have excellent and yet distinctive oral pharmacokinetic profiles across multiple species. At tolerable doses, oral administration of RCZY-690 and RCZY-680 showed potent anti-tumor efficacy in a KRAS G12D-mutant HPAC pancreatic xenograft model, with sustained inhibition of intratumoral p-ERK and DUSP6 levels. The superior anti-tumor efficacy may be attributed to their highly potent cellular cytotoxicity, long mouse half-lives (10.1 h and 4.8 h, respectively), and high oral exposure levels. In conclusion, RCZY-690 and RCZY-680 are tri-complex pan RAS-MULTI(ON) inhibitors with best-in-class clinical potential for treating RAS-driven solid tumors. Citation Format: Celia X.-J. Chen, Lin Wang, Yu Bai, Xiaohong Liu, Qiaoni You, Jianming Bao. RCZY-690 and RCZY-680: Novel, highly potent, and orally bioavailable, tri-complex pan RAS-MULTI(ON) inhibitors with distinctive oral pharmacokinetic profiles, exhibiting broad anti-tumor activities in CDX models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 239.