To investigate the efficacy and safety of leflunomide beyond 2 years in a multinational, open-label extension of 2 phase III double-blind studies.


Patients with rheumatoid arthritis (RA) who received leflunomide (100 mg/day for 3 days, 10 mg/day or 20 mg/day thereafter) in the 2 phase III studies and who completed 2 years of treatment were offered inclusion in the open-label extension phase and were maintained on the same dosage of leflunomide. The American College of Rheumatology revised criteria for 20% improvement (ACR20), ACR50, and ACR70 response rates, the Stanford Health Assessment Questionnaire (HAQ) scores, and C-reactive protein (CRP) levels were assessed. Safety measures included monitoring of adverse events and laboratory values.


A total of 214 patients (mean age 57 years) were treated with leflunomide for >2 years; 74.8% of the patients were female. The mean disease duration was 4.1 years (range 0.1–26.6 years), and in 44% of patients, RA was first diagnosed within 2 years of entry into the phase III studies. The mean duration of leflunomide treatment was 4.6 years (range 2.8–5.8 years), and 32% of patients had received no previous treatment with disease-modifying antirheumatic drugs. ACR20, ACR50, and ACR70 response rates and HAQ scores at 1 year were maintained through year 4 or until the end point. No new types of adverse events were observed, and liver function was normal at baseline and at the end point in the majority of patients.


The improvements in both functional ability and physician-based efficacy measures seen with leflunomide after 1 year were maintained for up to 5 years (maximum treatment duration 5.8 years), demonstrating that the early efficacy of leflunomide in patients with RA is sustained long-term, and that the long-term safety profile of leflunomide is no different from that observed in phase III trials.