The Evolving Role of Second- and Third-Generation Tyrosine Kinase Inhibitors in Gastrointestinal Malignancies: Advances in Targeted Therapy with Sunitinib, Regorafenib, and Avapritinib

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. While imatinib revolutionized first-line therapy, resistance and specific mutation profiles necessitate subsequent generations of tyrosine kinase inhibitors (TKIs). Sunitinib, regorafenib, and avapritinib represent second-line, third-line, and mutation-specific therapies, respectively, offering improved precision and disease control. This review summarizes clinical trial evidence, real-world data, and translational studies evaluating the efficacy, safety, and mechanistic basis of second- and third-generation TKIs in GIST. Emphasis is placed on therapeutic sequencing, resistance mechanisms, and molecularly guided treatment selection. Sunitinib, a multitargeted TKI inhibiting KIT, PDGFR, and VEGFR, provides effective disease control in imatinib-resistant or intolerant patients. Regorafenib, a broad-spectrum multikinase inhibitor, improves progression-free survival in refractory GIST and targets additional angiogenic and oncogenic pathways. Avapritinib, a next-generation TKI, selectively inhibits PDGFRA D842V and KIT exon 17 mutations, addressing a previously untreatable, mutation-driven subgroup. Integration of these agents into treatment algorithms exemplifies a shift toward personalized therapy, with outcomes guided by mutation profiling and biomarker-driven decisions. Second- and third-generation TKIs have transformed the management of advanced GIST, extending survival and offering mutation-specific precision therapy. Ongoing research into resistance mechanisms, combination strategies, and novel inhibitors promises further optimization of patient-centered care.