Real-world Evaluation of the Transition Between Originator and Follow-on Glatiramer Acetate in People with Multiple Sclerosis: the "GA Transition" Study.

INTRODUCTION AND OBJECTIVE:The introduction of follow-on formulations of glatiramer acetate (GA) has raised questions regarding their equivalence to the originator in real-world practice. This study aimed to evaluate the clinical effectiveness and safety of switching from originator GA to its follow-on product, Copemyl® (CO), in people with multiple sclerosis (MS). METHODS:A multicenter, retrospective observational study was conducted, including patients with MS treated for at least two years with GA followed by at least two years with CO. The primary outcome was the annualized relapse rate (ARR), whereas secondary outcomes included disability progression assessed by the Expanded Disability Status Scale (EDSS), MRI activity, and adverse events (AEs). RESULTS:A total of 138 patients were included. The ARR was very low and comparable across treatments (GA: 0.028; CO: 0.019), with a mean paired difference of -0.009 (95 % CI -0.028 to 0.010; p = 0.38), falling within the predefined equivalence margin. Disability progression over six months occurred in 6.0 % of GA and 7.3 % of CO periods (HR 1.53; 95 % CI 0.74-3.16; p = 0.26). No significant difference was found in MRI activity (52.2 % vs 60.1 %, p = 0.14). Safety profiles were comparable, with mostly mild to moderate AEs; four serious AEs occurred under CO, two of them possibly treatment-related. CONCLUSIONS:Switching from originator GA to CO did not influence clinical outcomes or safety. These findings support the therapeutic equivalence of the two formulations in real-world clinical practice, by supporting previous evidence from randomized trials.