Time course of glatiramer acetate efficacy in patients with RRMS in the GALA study

OBJECTIVE: To determine the time to efficacy onset of glatiramer acetate (GA) 40 mg/mL 3-times-weekly formulation (GA40). METHODS: This post hoc analysis of data from the 1-year, double-blind, placebo-controlled phase of the Glatiramer Acetate Low-Frequency Administration study (NCT01067521) of GA40 in patients with relapsing-remitting MS (RRMS) sought to determine the timing of efficacy onset using a novel data-censoring approach. RESULTS: Compared with placebo-treated patients, those receiving GA40 exhibited a >30% reduction in the accumulated annualized relapse rate (ARR) within 2 months of initiating treatment and generally sustained this treatment difference during the 1-year study. Similarly, the proportion of GA40-treated patients who remained relapse-free was distinctly greater by month 2 and continued to increase up to a 10.8% difference at the end of the study. In addition, GA40 treatment was associated with a significant reduction in the number of gadolinium-enhancing T1 lesions and new/enlarging T2 lesions by month 6, with full treatment effect observed after 1 year. CONCLUSIONS: GA40 contributes to efficacy within 2 months of the start of treatment in patients with RRMS. These results are consistent with the observed time to efficacy onset for patients treated with GA 20 mg/mL daily in previous randomized, placebo-controlled clinical trials. CLASSIFICATION OF EVIDENCE: This study provides Class II evidence that for patients with RRMS, a 3-times-weekly formulation of GA 40 mg/mL leads to a >30% reduction in the ARR within 2 months.