Abstract
The KRAS G12D mutation, defined by substitution of glycine with aspartic acid at codon 12 within the GTP-binding region of the KRAS gene, occurs with particularly high prevalence in digestive system malignancies, especially pancreatic ductal adenocarcinoma (PDAC) and colorectal cancer (CRC). Oncogenic KRAS variants drive persistent activation of downstream signaling cascades, including the MAPK and PI3K pathways, thereby circumventing upstream regulation and fueling tumor initiation, progression, and therapeutic resistance. Because of its high intrinsic affinity for GTP/GDP and the lack of a readily accessible binding pocket, KRAS was long considered a difficult therapeutic target. The emergence of MRTX1133, a highly selective, noncovalent inhibitor that specifically binds the Switch II pocket of KRAS G12D, represents a major advance in precision oncology. By engaging this unique pocket, MRTX1133 effectively blocks effector interactions and potently suppresses MAPK and PI3K signaling. Preclinical investigations have revealed that MRTX1133 elicits strong antitumor responses in KRAS G12D mutant PDAC and CRC models, including pronounced tumor regression, enhanced apoptosis, and inhibition of metastatic features. Nonetheless, as observed with other targeted agents, resistance can arise through feedback activation of receptor tyrosine kinases, reactivation of parallel signaling pathways, metabolic reprogramming, and tumor microenvironmental influences. 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.