Vertical pathway inhibition overcomes adaptive feedback resistance to KRASG12C inhibition

Abstract

Purpose: Although KRASrepresents the most commonly mutated oncogene, it has long been considered an "undruggable" target. Novel covalent inhibitors selective for the KRAS^G12Cmutation offer the unprecedented opportunity to target KRAS directly. However, prior efforts to target the RAS-MAPK pathway have been hampered by adaptive feedback, which drives pathway reactivation and resistance. Experimental Design: A panel of KRAS^G12Ccell lines were treated with the KRAS^G12Cinhibitors ARS-1620 and AMG 510 to assess effects on signaling and viability. Isoform-specific pulldown of activated GTP-bound RAS was performed to evaluate effects on the activity of specific RAS isoforms over time following treatment. RTK inhibitors, SHP2 inhibitors, and MEK/ERK inhibitors were assessed in combination with KRAS^G12Cinhibitors in vitro and in vivo as potential strategies to overcome resistance and enhance efficacy. Results: We observed rapid adaptive RAS pathway feedback reactivation following KRAS^G12Cinhibition in the majority of KRAS^G12Cmodels, driven by RTK-mediated activation of wild type RAS, which cannot be inhibited by G12C-specific inhibitors. Importantly, multiple RTKs can mediate feedback, with no single RTK appearing critical across all KRAS^G12Cmodels. However, co-inhibition of SHP2, which mediates signaling from multiple RTKs to RAS, abrogated feedback reactivation more universally, and combined KRAS^G12C/SHP2 inhibition drove sustained RAS pathway suppression and improved efficacy in vitro and in vivo. Conclusions: These data identify feedback reactivation of wild type RAS as a key mechanism of adaptive resistance to KRAS^G12Cinhibitors and highlight the potential importance of vertical inhibition strategies to enhance the clinical efficacy of KRAS^G12Cinhibitors.