Laflunimus (HR-325; HR325), an analogue of the Leflunomide-active metabolite A-771726, is a novel and potent immunosuppressive agent that is orally bioactiveand acting ac an dihydroorotate dehydrogenase (DHODH) inhibitor. Laflunimus suppresses immunoglobulin (Ig) secretion, with IC50 values of 2.5 and 2 μM for IgM and IgG, respectively.