CombiRx is a randomized clinical trial to determine if the combined use of interferon beta-1a (IFN) and glatiramer acetate (GA) is a measurably better therapy than either agent used individually in patients with relapsing-remitting (RR) multiple sclerosis (MS).  This is a multicenter, double blind, RCT examining combination therapy versus single agent therapy with three-year follow-up on the last patient randomized. All patients will remain on therapy until the last patient completes the study. All patients will then be transitioned, based on the findings, to open label of combination with continued follow-up or some recommendation about single agent therapy. While the study design benefits from having two arms of single agent therapy to examine the important question of whether there are differences between the single agents, the primary interest is in combination therapy. Therefore, a two-group combination versus single agent concept was used - splitting the population into single agent and combination therapy equally. The single agent arm is divided into two groups, IFN and GA providing for 3 treatment arms: IFN intramuscularly (IM) and GA subcutaneously (SC) (50% of the patients), IFN IM and placebo SC (25% of the patients) and GA SC and placebo IM (25% of the patients).

• 68 international sites
• 1008 participants randomized
• 3-group RCT
• NCT: NCT00211887
• Clinicaltrials.gov website: https://clinicaltrials.gov/study/NCT00211887?term=NCT00211887&rank=1