Anti-tumor efficacy of a potent and selective non-covalent KRAS^G12D inhibitor.

Area of Science:

• Oncology
• Molecular Biology
• Drug Discovery

Background:

• Targeting KRAS G12C has advanced cancer therapy.
• Alternative KRAS mutations, like KRAS G12D, remain significant therapeutic challenges.
• Developing selective inhibitors for KRAS mutants is crucial for effective cancer treatment.

Purpose of the Study:

• To evaluate the mechanism of action and anti-tumor efficacy of MRTX1133, a novel KRAS G12D inhibitor.
• To assess the selectivity and potency of MRTX1133 against KRAS G12D.
• To explore combination strategies for enhanced anti-tumor activity in KRAS G12D-mutant tumors.

Main Methods:

• Biochemical assays to determine binding affinity (K_D, IC_50) and selectivity.
• Co-crystal structural analysis to understand drug-target interaction.
• In vitro studies on KRAS G12D-mutant cell lines to assess inhibition of signaling pathways and cell viability.
• In vivo studies using xenograft models (cell-line and patient-derived) to evaluate anti-tumor efficacy.
• Pharmacological and CRISPR-based screens for combination therapy assessment.

Main Results:

• MRTX1133 demonstrated high-affinity binding to KRAS G12D (K_D ~0.2 pM) with ~700-fold selectivity over wild-type KRAS.
• Potent inhibition of ERK1/2 phosphorylation and cell viability in KRAS G12D-mutant cells (median IC_50 ~5 nM) with >1,000-fold selectivity.
• Significant tumor regression (≥30%) observed in a subset of xenograft models, including 73% of pancreatic ductal adenocarcinoma (PDAC) models.
• Co-targeting KRAS G12D with EGFR or PI3Kα enhanced anti-tumor activity.

Conclusions:

• MRTX1133 is a potent and selective non-covalent inhibitor of KRAS G12D.
• Selective targeting of KRAS mutants with small molecules is feasible.
• KRAS G12D-mutant tumors are therapeutically susceptible and depend on mutant KRAS for growth and survival.
• Combination strategies may enhance the efficacy of KRAS G12D inhibition.