Leflunomide (CAS 75706-12-6) is a small-molecule agonist targeting the aryl hydrocarbon receptor (AHR) pathway It is designed to modulate AHR signaling thereby enhancing regulatory T cell (Treg) numbers altering inflammatory cytokine profiles and influencing immune responses Leflunomide exerts its biological activity primarily through metabolic conversion to its active metabolite Teriflunomide (A771726) which mediates immunosuppressive effects It enhances IL-10 production and suppresses IL-17 and IL-23 secretion In cell-based studies leflunomide demonstrates anti-proliferative efficacy in human medullary thyroid carcinoma cells (MTC-TT) with IC50 values ranging from approximately 30 to 50 M depending on specific assay conditions Based on these pharmacological properties leflunomide holds research potential in ischemia-reperfusion renal injury sepsis-induced intestinal oxidative stress and tumor proliferation inhibition models