rac A77 1726 is the active metabolite of Leflunomide, a potent disease-modifying antirheumatic drug used in the treatment of rheumatoid arthritis. LEF-M interferes with dendritic cell function. The second Phase III study evaluating the efficacy of Genzyme's teriflunomide therapy against relapsing forms of multiple sclerosis found the once-daily oral drug to be no less effective than injectable interferon beta 1a (Rebif®).