DHODH and rheumatoid arthritis: Leflunomide, a human DHODH (HsDHODH) inhibitor currently used for the treatment of rheumatoid arthritis (RA), has been reported to have an anti-cancer and anti-viral activity (Teschner and Burst, 2010; Vyas and Ghate, 2011; Lolli et al., 2018).