Imatinib methanesulfonate, also known as STI-571, is a methanesulfonate (mesylate) salt that is the monomesylate salt of imatinib. Used for treatment of chronic myelogenous leukemia and gastrointestinal stromal tumours. It has a role as an antineoplastic agent, an apoptosis inducer, a tyrosine kinase inhibitor and an anticoronaviral agent. It contains an imatinib.