Abstract LB165: GFH547: An orally bioavailable, cyclophilin A-hijacking panRAS(on) inhibitor with broad spectrum anti-tumor activities

Abstract KRAS has recently become druggable with the approval of two KRAS G12C inhibitors - sotorasib and adagrasib. However, current SIIP-based KRAS inhibitors preferentially target the inactive, GDP-bound KRAS and thus are susceptible to adaptive resistance due to MAPK pathway reactivation. Furthermore, RTK pathway alterations frequently emerge to cause acquired resistance. These drawbacks limit the rate and duration of anti-tumor response. Developing more robust small molecule RAS (on) inhibitors that target active, GTP-bound RAS proteins is a promising new approach to enhance clinical benefits. Here we report preclinical characterization of a novel RAS (on) inhibitor - GFH547, designed to treat cancers carrying multiple RAS mutations. In biochemical assays, GFH547 disrupted the binding of GMPPNP-bound G12V, G12D or wild type KRAS to RAF1 in a CypA-dependent manner, as the inhibitory effect was significantly abolished in the absence of CypA. GFH547 suppressed phosphor-ERK1/2 (p-ERK) levels in KRAS G12V- and G12D-mutated cells with IC50s 1 nM, and demonstrated potent tumor-suppressive effect in 29 cancer cell lines carrying diverse KRAS (G12A, G12C, G12V, G12R, G12S or G13D), NRAS (G12D or Q61L) or HRAS (Q61H) mutations, with IC50s of 0. 04-1. 9 nM. In addition, GFH547 was also cytotoxic in 9 cancer cell lines carrying EGFR or FGFR2/3 amplification, mutation or fusion, with IC50s of 0. 12-198 nM. Conversely, GFH547 was inactive against 4 BRAF V600E-mutated, RAS-independent cancer cell lines. In KRAS-mutated xenograft models, oral administration of GFH547 elicited rapid and potent inhibition of intratumoral p-ERK levels, and led to tumor regression at dose levels as low as 1 mg/kg QD. In contrast to sotorasib and adagrasib, GFH547 was not susceptible to RTK-reactivation following EGF stimulation, and remained effective against cell lines carrying KRAS mutations that confer acquired resistance to SIIP-based KRAS inhibitors. At 10 μM, GFH547 showed no off-target activity in 72-kinase selectivity and SafetyScreen44 panels. GFH547 has a bioavailability of 76% and was well tolerated in mice, with an estimated therapeutic index 20. Taken together, by hijacking CypA to block oncogenic RAS proteins broadly in their active forms, GFH547 represents a new generation of RAS inhibitors that are superior to the mainstream SIIP-based KRAS inhibitors in overcoming adaptive and acquired resistance. The compound demonstrated strong therapeutic activities in tumors with activating RAS and RTK mutations/alterations. Based on these promising results, we are advancing a CypA-binding panRAS (on) inhibitor into the clinic as targeted therapy for cancers addicted to RAS pathways. Citation Format: Feng Yan, Jichen Zhao, Tao Liang, Tao Jiang, Chonglan Lin, Ling Peng, Kai Ma, Huabin Yang, Wan He, Zhen Li, Leitao Zhang, Xiaoming Xu, Yanhui Zhao, Xiaohui Zhang, Yonghong Ni, Qiang Liu, Jinting Gao, Fubo Xie, Xueyan Gao, Xiaoling Lan, Li Wang, Jingyang Zhang, Hongcan Ren, Dong Liu, Siyuan Le, Fusheng Zhou, Jiong Lan, Qiang Lu. GFH547: An orally bioavailable, cyclophilin A-hijacking panRAS (on) inhibitor with broad spectrum anti-tumor activities 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 LB165.