masitinib + methotrexate

**Masitinib + methotrexate** is an investigational oral combination therapy being evaluated for the treatment of **active rheumatoid arthritis (RA)** in patients with inadequate response to methotrexate or other disease-modifying antirheumatic drugs (DMARDs). **Masitinib** is a selective small molecule tyrosine kinase inhibitor with potent inhibitory activity against c-KIT (a receptor tyrosine kinase), as well as blocking other kinases like PDGFR and LYN, leading to suppression of mast cell and microglia activity, which are hypothesized to play crucial roles in RA pathogenesis[1][3][5]. **Methotrexate** is a well-established anti-folate antimetabolite and DMARD, with immunosuppressive and anti-inflammatory activity through inhibition of dihydrofolate reductase and effects on purine/pyrimidine synthesis. Their combination is intended to provide complementary anti-inflammatory and disease-modifying mechanisms for improved control in RA patients refractory to methotrexate alone.