<prompt> Leflunomide used against Rheumatoid arthritis acts by inhibiting:Ionisne monophosphate dehydrogenaseDihydroorotate dehydrogenaseAldehyde dehydrogenaseTNF-α receptor  <response>: Leflunomide inhibits Dihydroorotate Dehydrogenase and inhibits synthesis of pyrimidine and arrests growth of B-cells. 