Magnetic resonance studies of intramuscular interferon β-1a for relapsing multiple sclerosis

The Multiple Sclerosis Collaborative Research Group trial was a double- blind, randomized, multicenter, phase III, placebo-controlled study of interferon β-1a (IFNβ-1a; AVONEX) in relapsing forms of multiple sclerosis. Initial magnetic resonance imaging results have been published; this report provides additional results. Treatment with IFNβ-1a, 30 μg once weekly by intramuscular injection, resulted in a significant decrease in the number of new, enlarging, and new plus enlarging T2 lesions over 2 years. The median increase in T2 lesion volume in placebo and IFNβ-1a patients was 455 and 152 mm³, respectively, at 1 year and 1,410 and 628 mm³ at 2 years, although the treatment group differences did not reach statistical significance. For active patients, defined as those with gadolinium enhancement at baseline, the median change in T2 lesion volume in placebo and IFNβ-1a patients was 1,578 and -12 mm³ and 2,980 and 1,285 mm³ at 1 and 2 years, respectively. Except for a minimal correlation of 0.30 between relapse rate and the number of gadolinium-enhanced lesions, correlations between MR and clinical measures at baseline and throughout the study were in general poor. Once weekly intramuscular IFNβ-1a appears to impede the development of multiple sclerosis lesions at an early stage and has a favorable impact on the long- term sequelae of these inflammatory events as indicated by the slowed accumulation of T2 lesions.