Avapritinib is a targeted therapy used primarily in the treatment of certain gastrointestinal stromal tumors (GIST) that have specific mutations in the PDGFRA gene, particularly the exon 18 mutations including D842V. It is especially effective in cases where tumors are resistant to other tyrosine kinase inhibitors. The drug works by selectively inhibiting the abnormal KIT and PDGFRA proteins that drive tumor growth, leading to reduced cancer cell proliferation and tumor shrinkage. It is also approved for use in adults with unresectable or metastatic GIST with PDGFRA exon 18 mutations. Additionally, avapritinib has shown clinical activity in systemic mastocytosis, particularly in advanced forms such as aggressive systemic mastocytosis or systemic mastocytosis with associated hematological neoplasm, where it targets the D816V mutation in the KIT receptor. Due to its ability to cross the blood-brain barrier, avapritinib is being investigated in cancers with central nervous system involvement. Its high selectivity reduces off-target effects, making it a valuable option in precision oncology for patients with defined genetic alterations.