Randomized controlled trials to assess therapies for multiple sclerosis.

MS poses formidable challenges to clinical investigators. Obstacles to the study of MS therapies include disease chronicity, an unpredictable clinical course, radiologic and pathologic heterogeneity, and limited understanding of the underlying pathophysiology. Randomized controlled trials (RCTs) provide a means to assess therapeutic efficacy while reducing the risks of study bias and confounding factors that influence interpretation of results. RCTs have demonstrated that type 1 interferons and glatiramer acetate alter the short-term natural history of MS and have served as the basis of approval for the marketing of these treatments. Improvements and optimization of trial methodology may hasten the discovery of effective therapies and facilitate better comparisons of the results of individual drug trials. The most urgent need is for improved surrogate end points for clinical outcome with predictive validity for long-term disability. Even if RCT methodology is optimal, however, several limitations inherent to MS trials threaten to impede further progress, including obstacles to long-term studies (e.g., costs), patient withdrawal, and escalating sample size requirements to detect partial therapeutic benefit. There is a crucial need to develop alternative investigative methods, possibly through enhanced collaboration across centers and with industry, and by exploring innovative techniques to use existing RCT and natural history databases to greater advantage.