The paradox-breaking panRAF plus SRC family kinase inhibitor, CCT3833, is effective in mutant KRAS-driven cancers

Background: KRAS is mutated in ~90% of pancreatic ductal adenocarcinomas (PDAC), ~35% of colorectal cancers (CRC) and ~20% of non-small-cell lung cancers (NSCLC). There has been recent progress in targeting G12C KRAS specifically, but therapeutic options for other mutant forms of KRAS are limited, largely because the complexity of downstream signaling and feedback mechanisms mean that targeting individual pathway components is ineffective. Design: The protein kinases RAF and SRC are validated therapeutic targets in KRAS -mutant PDAC, CRC and NSCLC and we show that both must be inhibited to block growth of these cancers. We describe CCT3833, a new drug that inhibits both RAF and SRC which may be effective in KRAS -mutant cancers. Results: We show that CCT3833 inhibits RAF and SRC in KRAS -mutant tumors in vitro and in vivo , and that it inhibits tumor growth at well-tolerated doses in mice. CCT3833 has been evaluated in a Phase I clinical trial (NCT02437227) and we report here that it significantly prolongs progression-free survival of a patient with a G12V KRAS spindle cell sarcoma who did not respond to a multi kinase inhibitor and therefore had limited treatment options. Conclusions: New drug CCT3833 elicits significant pre-clinical therapeutic efficacy in KRAS -mutant colorectal, lung and pancreatic tumor xenografts, demonstrating a treatment option for several areas of unmet clinical need. Based on these pre-clinical data, and the Phase I clinical unconfirmed response in a patient with KRAS -mutant spindle cell CCT3833 requires further evaluation in patients with other KRAS -mutant cancers.