The Mayo Clinic-Canadian Cooperative trial of sulfasalazine in active multiple sclerosis

Objective: To determine whether sulfasalazine is better than placebo in slowing disability progression in MS. Methods: In this randomized, double- blind, placebo-controlled phase III trial, 199 patients with active relapsing-remitting (n = 151) or progressive (n = 48) MS were evaluated at 3- month intervals for a minimum of 3 years (94% completed 3 years of follow- up; mean follow-up, 3.7 years). MRI studies were performed at 6-month intervals on a subset of 89 patients. Results: Sulfasalazine failed to slow or prevent disability progression as measured by the primary outcome (confirmed worsening of the Expanded Disability Status Scale [EDSS] score by at least 1.0 point on two consecutive 3-month visits). Sulfasalazine influenced favorably a number of secondary outcomes during the first 18 months of the trial (e.g., annualized relapse rate, proportion of relapse- free patients; progressive subgroup only: rate of EDSS progression at 1 and 2 years, median time to EDSS progression) but these positive findings were not sustained into the second half of the trial. Conclusions: Sulfasalazine does not prevent EDSS score progression in the subset of MS patients studied by this protocol. Treatments may improve relapse-related outcomes in MS, at least temporarily, without providing sustained slowing of EDSS progression. Phase III MS trials should be of sufficient length to determine a meaningful impact on disease course.