Flumatinib mesylate is primarily used in the treatment of chronic myeloid leukemia (CML). It functions as a tyrosine kinase inhibitor, specifically targeting the BCR-ABL fusion protein, which is a key driver of CML. By inhibiting this protein, it helps to reduce the proliferation of leukemia cells and control the progression of the disease. It is often prescribed for patients who are resistant or intolerant to other tyrosine kinase inhibitors, providing an alternative therapeutic option. The drug is administered orally, allowing for convenient and consistent dosing. Clinical studies have shown its efficacy in achieving significant hematologic and cytogenetic responses in CML patients.