<p>Leflunomide is an isoxazole immunomodulatory agent which inhibits de novo pyrimidine synthesis and has anti-proliferative activity. Following oral administration, it is rapidly metabolized to A771726, which is active in vitro and is presumed to be the active drug in vivo. Leflunomide has demonstrated prophylactic and therapeutic effects in animal models of autoimmune disease. In addition, leflunomide has exhibited anti-inflammatory and weak analgesic and antipyretic activity. In a model of experimental septicemia, leflunomide did not alter the resistance of mice to bacterial pathogens.</p>