Here, we evaluated in vivo antitumor activity, target engagement, selectivity, and tumor specificity of ADT-1004, an orally bioavailable prodrug of ADT-007 having highly potent and selective pan-RAS inhibitory activity. ADT-1004 strongly blocked tumor growth and RAS activation in mouse PDAC models without discernable toxicity. As evidence of target engagement and tumor specificity, ADT-1004 inhibited activated RAS and ERK phosphorylation in PDAC tumors at dosages approximately 10-fold below the maximum tolerated dose and without discernable toxicity. ADT-1004 inhibited ERK phosphorylation in PDAC tumors. In addition, ADT-1004 blocked tumor growth and ERK phosphorylation in PDX PDAC models with KRAS G12D , KRAS G12V , KRAS G12C , or KRAS G13Q mutations. ADT-1004 treatment increased CD4 + and CD8 + T cells in the TME consistent with exhaustion and increased MHCII + M1 macrophage and dendritic cells. ADT-1004 demonstrated superior efficacy over sotorasib and adagrasib in tumor models involving human PDAC cells resistant to these KRAS G12C inhibitors. As evidence of selectivity for tumors from PDAC cells with mutant KRAS, ADT-1004 did not impact the growth of tumors from RAS WT PDAC cells. Displaying broad antitumor activity in multiple mouse models of PDAC, along with target engagement and selectivity at dosages that were well tolerated, ADT-1004 warrants further development.
Significance: ADT-1004 displayed robust antitumor activity in aggressive and clinically relevant PDAC models with unique tumor specificity to block RAS activation and MAPK signaling in RAS mutant cells. As a pan-RAS inhibitor, ADT-1004 has broad activity and potential efficacy advantages over allele-specific KRAS inhibitors by averting resistance. These findings support clinical trials of ADT-1004 for KRAS mutant PDAC.