JAK1 and rheumatoid arthritis: Brepocitinib, a dual TYK2/JAK1 inhibitor, has shown clinical efficacy in the management of autoimmune diseases, yet its mechanistic impact on synoviocytes remains underexplored.<h4>Objectives</h4>To investigate the molecular and functional effects of brepocitinib on MH7A and RA-FLS synoviocytes, a key effector cell type in RA pathogenesis.<h4>Methods</h4>MH7A and RA-FLS cells were treated with brepocitinib (0.5 μM, 1 μM, and 5 μM) for 24 hours.