Long-term outcomes of peginterferon beta-1a in multiple sclerosis: results from the ADVANCE extension study, ATTAIN

BACKGROUND: ADVANCE was a phase III trial of the efficacy and safety of subcutaneous peginterferon beta-1a 125 µg every 2 or 4 weeks in patients with relapsing-remitting multiple sclerosis (RRMS). ATTAIN was a 2-year extension study of ADVANCE. The aim was to evaluate the long-term safety, tolerability, and efficacy of peginterferon beta-1a 125 µg every 2 or 4 weeks in ATTAIN. METHODS: ADVANCE dosing schedules were maintained in ATTAIN, except that every-4-weeks dosing patients were switched to every-2-weeks dosing after conversion of the study to an open-label protocol. ATTAIN was considered complete when the last patient completed the 96-week extension study. Primary endpoints included adverse event (AE) and serious AE (SAE) incidence. Secondary endpoints included relapse, magnetic resonance imaging, and disability outcomes. RESULTS: Of the 1512 patients randomized in ADVANCE, 1076 (71%) continued treatment in ATTAIN; of these, 842 (78%) completed the open-label extension study. During ATTAIN, 478 patients (87%) in the every-2-weeks group and 471 patients (89%) in the every-4-weeks group experienced an AE; SAEs were reported in 90 patients (16%) in the every-2-weeks group and 113 patients (21%) in the every-4-weeks group. The most frequent AEs reported were injection site reactions and flu-like symptoms, both of which numerically decreased over time. Peginterferon beta-1a every 2 weeks versus every 4 weeks significantly reduced the adjusted annualized relapse rate over 6 years (0.188 versus 0.263, p = 0.0052) and the risk of relapse over 5 years (36% versus 49%, p = 0.0018). Fewer new T1, new/newly enlarging T2, and gadolinium-enhancing magnetic resonance imaging lesions were observed with every-2-weeks dosing than every-4-weeks dosing over 4 years. CONCLUSIONS: Results from the ADVANCE extension study, ATTAIN, confirm the favorable long-term safety and tolerability profile of peginterferon beta-1a in patients with RRMS and provide additional evidence for the clinical and radiological benefits associated with this therapy.