VANCOUVER (FRONTLINE MEDICAL NEWS) Peginterferon beta-1a has durable efficacy for the treatment of relapsing-remitting multiple sclerosis, according to data from the ATTAIN extension study of a phase III trial.

With dosing every 2 weeks, as approved by the Food and Drug Administration, the 36% reduction in adjusted annualized relapse rate seen with peginterferon beta-1a relative to placebo in the first year persisted out to at least 6 years, investigators reported at the annual meeting of the American Academy of Neurology.

Additionally, the respective 67% and 86% reductions in new T2 lesions and gadolinium-enhancing lesions on magnetic resonance imaging that were observed in the first year of treatment persisted out to at least 4 years.

“Clinical and imaging [benefits were] sustained over up to a 6-year period in the pivotal and extension studies,” lead investigator Damian Fiore, Pharm.D., global medical director at Biogen in Cambridge, Mass., summarized in the emerging science session where he presented the data.

As the drug was approved based on the first-year findings, these new, longer-term data are a welcome confirmation of those initial benefits, according to session moderator Dr. José E. Cavazos, professor of neurology and assistant dean at the University of Texas Health Science Center at San Antonio.

“Despite the open-label design of this company-sponsored study, the results are very encouraging for patients with multiple sclerosis as the analysis reveals year-over-year results with sustained efficacy,” he said in comments provided by email.

The pivotal, 2-year ADVANCE randomized trial (Efficacy and Safety Study of Peginterferon Beta-1a in Participants With Relapsing Multiple Sclerosis) began with a year of placebo in some patients and compared dosing strategies of peginterferon beta-1a (Plegridy).

“The ADVANCE trial was the largest trial that’s been done with interferon, at 1,500 patients,” Dr. Fiore commented. “One other important thing to note is that our colleagues on the interferon-alpha side have been using pegylation for quite a while, but this represents the first use of pegylation in MS therapy.”

Main results were published 3 years ago (Lancet Neurol. 2014;13:657-65) and led to approval of peginterferon beta-1a by the Food and Drug Administration for this indication shortly thereafter.

A total of 730 patients who started active treatment in the first year of the trial continued treatment on the ATTAIN extension study (Long-Term Safety and Efficacy Study of Peginterferon Beta-1a). The investigators reported data for the 376 patients given the drug every 2 weeks, analyzed after all had completed at least 96 weeks on the extension study.

Results for the intention-to-treat population showed that the adjusted annualized relapse rate ranged from 0.055 to 0.241 with peginterferon beta-1a in years 1 through 6 of treatment, compared with 0.418 with placebo in year 1.

The pattern was similar for the mean number of new T1 hypointense lesions (0.7-1.7 vs. 3.8 with placebo), new or newly enlarging T2 lesions (1.9-3.9 vs. 10.9), and gadolinium-enhancing lesions (0.2-0.3 vs. 1.4) during the first 4 years of treatment.

Dr. Fiore disclosed that he is an employee and stockholder of Biogen, which sponsored the trial.