The Food and Drug Administration (FDA) has approved Plegridy (peginterferon beta-1a; Biogen) for intramuscular (IM) administration to treat relapsing forms of multiple sclerosis (MS), to include clinically isolated syndrome, relapsing-remitting disease, and active secondary progressive disease, in adults.  Previously, the product had only been approved for subcutaneous (SC) administration.

The approval for IM use was based on data from an open-label, crossover study that assessed the bioequivalence of single doses of 125mcg of Plegridy administered as an SC and IM injection in 130 healthy volunteers. Findings showed similar pharmacokinetics between the SC and IM injections. Overall, injection site reactions were reported in 14% of individuals who received the IM injection vs 32% of those who received the SC injection.

Commenting on the approval, Maha Radhakrishnan, MD, Chief Medical Officer at Biogen, said: “Plegridy is a proven, effective therapy for relapsing MS, and this approval gives new and current MS patients a different delivery method that has the potential to significantly reduce injection site reactions.”

For patients being administered an IM injection for the first time, Plegridy should be titrated using the Plegridy Titration Kit, which is designed for use with the prefilled syringes. Plegridy for IM injection is supplied as a single-dose prefilled syringe containing 125mcg/0.5mL of peginterferon beta-1a and is packaged with a separate needle. The protective rubber cover of the prefilled syringe contains natural rubber latex which may cause allergic reactions for sensitive individuals.


1.      Biogen announces FDA approval of Plegridy® (peginterferon beta-1a) intramuscular administration for multiple sclerosis. [press release]. Cambridge, MA; Biogen; February 1, 2021.

2.      Plegridy [prescribing information]. Cambridge, MA: Biogen Inc; 2021.