Laflunimus (HR325) is an immunosuppressive agent and an analogue of the Leflunomide-active metabolite A77 1726. Laflunimus is an orally active inhibitor of dihydroorotate dehydrogenase (DHODH). Laflunimus suppresses immunoglobulin (Ig) secretion, with IC50 values of 2.5 and 2 μM for IgM and IgG, respectively. Laflunimus also is a prostaglandin endoperoxide H synthase (PGHS) -1 and -2 inhibitor.