NEW YORK — Biogen Idec Inc. said Thursday its longer-lasting injectable multiple sclerosis drug, peginterferon beta-1a, helped reduce patients’ risk of relapse by 36 percent when given every two weeks, meeting the goals of a late-stage study.

The medicine reduced patients’ risk of flare-ups by 28 percent when dosed every four weeks compared with placebo, the Weston, Mass., firm said in a statement. Based on the results, Biogen said it plans to apply this year for regulatory approval in Europe and the United States.