The distribution of the magnetic resonance imaging response to glatiramer acetate in multiple sclerosis.

We investigated the distribution of the magnetic resonance imaging (MRI)-measured response to glatiramer acetate (GA) treatment in multiple sclerosis (MS) using data from a clinical trial of relapsing-remitting (RR) MS. A fixed and a random effects model were used to quantify the between-patient heterogeneity in treatment response, expressed as new enhancing lesion percentage reduction. In 95% of the patients, lesion reduction due to treatment was estimated to range between -20% and -54%, indicating a rather homogeneous effect of GA on MRI-measured disease activity in RRMS.