KRAS (G12D)-selective inhibitor MRTX1133 suppresses proliferation and differentially modulates chemosensitivity in...

Ovarian mucinous carcinoma (OMC) is a rare subtype of ovarian cancer characterized by frequent KRAS mutations and a poor response to platinum- and taxane-based chemotherapy, underscoring the need for novel therapeutic strategies. MRTX1133, a recently developed non-covalent and selective KRAS (G12D) inhibitor, has demonstrated potent antitumor activity in pancreatic and colorectal cancers; however, its efficacy in OMC remains unexplored. In the present study, the antitumor effects of MRTX1133 in the KRAS (G12D)-mutant OMC cell line MCAS and its interactions with conventional chemotherapeutic agents were evaluated. Cell viability was assessed using WST-1 assays, ERK phosphorylation was evaluated by western blotting and gene expression levels were analyzed by reverse transcription-quantitative PCR. Results indicated that MRTX1133 suppressed MCAS cell proliferation in a concentration-dependent manner, whereas proliferation of KRAS wild-type and KRAS (G12S)-mutant cells was not significantly inhibited. Treatment markedly inhibited ERK phosphorylation, suggesting suppression of the MAPK pathway. MRTX1133 reduced the mRNA expression of Ki-67 and numerous cyclins (D1, A2 and B1), suggesting attenuation of proliferative signaling. When combined with cytotoxic agents, including paclitaxel, SN38, gemcitabine and cisplatin, MRTX1133 reduced the sensitivity to cell cycle-dependent chemotherapeutic agents, namely paclitaxel, SN38 and gemcitabine, while not affecting the activity of the non-cell cycle-dependent agent cisplatin. The present study therefore provided preclinical evidence for the potential utility of KRAS (G12D)-targeted therapy in OMC and highlights the importance of sequential rather than concurrent scheduling of MRTX1133 with cell cycle-dependent chemotherapy to optimize therapeutic efficacy.