We evaluated KRAS G12D -specific (MRTX1133) and pan-KRAS inhibitor (RMC-6236) in KRAS mut organoid and orthotopic PDX models of AA. Additionally, KRAS inhibition remodels TME and may enhance innate immune signaling. These findings support continued clinical development of KRAS inhibitors in AA and provide a rationale for combination strategies targeting resistance pathways and stromal remodeling.

P1, N=130, Not yet recruiting, Bayer

P1, N=42, Recruiting, D3 Bio (Wuxi) Co., Ltd | Not yet recruiting --> Recruiting

P3, N=588, Recruiting, Incyte Corporation

These findings underscore the importance of combination therapeutic approaches in overcoming resistance. This review summarizes current evidence on the mechanisms of action, resistance pathways, and potential combination strategies of MRTX1133 in digestive system cancers, and discusses its translational relevance and clinical implications for KRAS G12D mutant malignancies.

Through screening a 2,652-kinase inhibitor library, we discovered that Osimertinib, an EGFR tyrosine kinase inhibitor, and its analogs strongly synergize with MRTX1133 against both parental and MRTX1133-resistant cells. NT-1 strongly synergized with MRTX1133 to suppress EGFR/MAPK signaling and induce apoptosis in an MRTX1133-resistant patient-derived organoid model of CRC. We present novel small molecule combinations with the potential to overcome the limitations of KRAS inhibitors with direct clinical translational applications.

Collectively, our findings suggest that the combination of DT2216/everolimus potentiates the anti-tumor efficacy of MRTX1133 associated with enhanced apoptosis induction and inhibition of compensatory survival signaling.

P1, N=17, Terminated, AstraZeneca | Phase classification: P1/2 --> P1

Two covalent inhibitors, sotorasib and adagrasib, which target a specific codon 12 mutation (G12C), had received accelerated approvals for clinical use. This appears to be due to a lack of effect on downstream KRAS effectors such as the ribosomal protein S6, highlighting the need for strategies that take into account potential context-dependent processes. Together with other recent reports on high-affinity binding of MRTX1133 to other non-G12D KRAS mutants, our findings further reveal the usefulness of MRTX1133 as a chemical probe that continues to provide novel insights on KRAS biology and inhibition mechanisms.

While KRAS was long considered undruggable, the development of mutant-specific inhibitors, including covalent inhibitors targeting KRASG12C (such as Sotorasib and Adagrasib) and non-covalent inhibitors targeting KRASG12D (such as Mirati's MRTX1133), has shown promise. In cellular models of KRAS-mutated NSCLC and PDAC, this nanoplatform achieved comparable or superior therapeutic outcomes with respect to the individual drugs. This study provides a compelling proof-of-concept for the in vitro delivery of KRASG12C mutant-specific inhibitors and degraders to human tumors through a tumor microenvironment-activated nanomedicine approach and lays the groundwork for future studies in physiologically relevant models to assess TME-specific activation and tumor selectivity.

Notably, combining a G9a degrader (G9D-4) with the KRASG12D inhibitor MRTX1133 elicited synergistic anti-tumor effects in KRASG12D-mutant tumoroids. Overall, our study provides preclinical insights from a small PDAC and BTC tumoroid cohort, supporting tumoroid-based platforms for exploratory drug screening and pharmacogenomic analyses and suggesting potential therapeutic directions that warrant further validation.