IL-6R, is part of the signaling pathway for IL-6, a pro-inflammatory cytokine central to RA pathogenesis. By blocking IL-6R, sarilumab suppresses downstream JAK/STAT signaling, leading to decreased production of acute-phase reactants, reduced synovial inflammation, and alleviation of systemic symptoms. It is often used in patients with inadequate response to conventional disease-modifying antirheumatic drugs (DMARDs).