Real‐World Safety and Effectiveness of Glatiramer Acetate in Patients With Multiple Sclerosis: Final Results of Post‐Marketing Surveillance in Japan

Background Glatiramer acetate is an injectable disease‐modifying therapy indicated for multiple sclerosis (MS). Aim To evaluate the real‐world safety and effectiveness of glatiramer acetate for MS in Japan. Methods A prospective, multicenter, observational, all‐case post‐marketing survey was conducted in Japan between November 2015 and March 2024 (NCT03209479). Patients who initiated glatiramer acetate for MS were enrolled and followed for 24 months. The primary safety outcome was incidence of adverse drug reactions (ADRs); effectiveness outcomes included annual rate of MS relapse, brain magnetic resonance imaging (MRI) findings, and Expanded Disability Status Scale (EDSS) scores. Results The safety analysis population included 1155 patients (mean age, 38.0 years; 81.0% women). The median duration of treatment was 180 days; the most common reason for discontinuation was adverse events (42.6%). ADR incidence was 77.6%, most of which were injection site reactions (70.0%) and non‐serious. In the effectiveness analysis population ( n = 1149), the annual relapse rate during the observation period was 0.60 relapses/year (95% confidence interval, 0.54–0.65), which was lower than the prespecified effectiveness criterion of 1.2 relapses/year. The mean number of T1‐weighted gadolinium‐enhancing lesions, new or enlarged T2‐weighted lesions, and new or enlarged fluid‐attenuated inversion recovery (FLAIR) lesions on brain MRI, as well as EDSS scores, tended to remain stable or improve slightly over 24 months. Safety and effectiveness were generally consistent across subgroups stratified by patient characteristics and treatment factors. Conclusion This large‐scale dataset elucidated real‐world use of glatiramer acetate in Japan and demonstrated its safety and effectiveness in > 1000 patients with MS. Trial Registration This survey was registered with ClinicalTrials.