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

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.

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.

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.

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.