Azathioprine versus beta interferons for relapsing-remitting multiple sclerosis: a multicentre randomized non-inferiority trial.

For almost three decades in many countries azathioprine has been used to treat relapsing-remitting multiple sclerosis. However its efficacy was usually considered marginal and following approval of β interferons for this indication it was no longer recommended as first line treatment, even if presently no conclusive direct β interferon-azathioprine comparison exists. To compare azathioprine efficacy versus the currently available β interferons in relapsing-remitting multiple sclerosis, a multicenter, randomized, controlled, single-blinded, non-inferiority trial was conducted in 30 Italian multiple sclerosis centers. Eligible patients (relapsing-remitting course; ≥ 2 relapses in the last 2 years) were randomly assigned to azathioprine or β interferons. The primary outcome was annualized relapse rate ratio (RR) over 2 years. Key secondary outcome was number of new brain MRI lesions. Patients (n = 150) were randomized in 2 groups (77 azathioprine, 73 β interferons). At 2 years, clinical evaluation was completed in 127 patients (62 azathioprine, 65 β interferons). Annualized relapse rate was 0.26 (95% Confidence Interval, CI, 0.19-0.37) in the azathioprine and 0.39 (95% CI 0.30-0.51) in the interferon group. Non-inferiority analysis showed that azathioprine was at least as effective as β interferons (relapse RRAZA/IFN 0.67, one-sided 95% CI 0.96; p