Tyrosine Kinase Inhibitors for Gastrointestinal Stromal Tumor After Imatinib Resistance.

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract, primarily driven by activating mutations in KIT (CD117) and platelet-derived growth factor receptor alpha (PDGFRA). The introduction of tyrosine kinase inhibitors (TKIs), especially imatinib, has significantly transformed GIST treatment. However, the emergence of both primary and secondary resistance to imatinib presents ongoing therapeutic challenges. This review comprehensively explores the mechanisms underlying imatinib resistance and evaluates subsequent TKI therapies. Sunitinib, regorafenib, and ripretinib are currently approved as standard second-, third-, and fourth-line therapies, each demonstrating efficacy against distinct mutational profiles. Avapritinib, notably effective against PDGFRA D842V mutations, represents a milestone for previously untreatable subgroups. Several alternative agents-such as nilotinib, masitinib, sorafenib, dovitinib, pazopanib, and ponatinib-have shown varying degrees of success in refractory cases or specific genotypes. Investigational compounds, including crenolanib, bezuclastinib, famitinib, motesanib, midostaurin, IDRX-42, and olverembatinib, are under development to address resistant or wild-type GISTs. Despite progress, long-term efficacy remains limited due to evolving resistance. Future strategies include precision medicine approaches such as ctDNA-guided therapy, rational drug combinations, and novel drug delivery systems to optimize bioavailability and reduce toxicity. Ongoing research will be crucial for refining treatment sequencing and expanding therapeutic options, especially for rare GIST subtypes.