Leflunomide

Leflunomide is an inhibitor of dihydroorotate dehydrogenase with IC50 of 2.5 μM. Leflunomide inhibits de novo pyrimidine synthesis in human T-cells in vitro. Leflunomide also inhibits lymphocyte proliferation. The inhibition of human DHODH by A77 1726, the active metabolite of leflunomide, occurs at levels (approximately 600 nM) that are achieved during treatment of rheumatoid arthritis (RA).