PEGylated interferon beta-1a

Update: Plegridy (peginterferon beta-1a) injection, for subcutaneous injection, was approved for the treatment of relapsing-remitting multiple sclerosis in August 2014. For more information about Plegridy, click here.

Avonex is an interferon beta disease-modifying treatment approved for use in relapsing forms of MS. In its standard formulation, Avonex is taken by intramuscular injection once weekly. However, the manufacturer Biogen Idec has reformulated Avonex for monthly dosing (PEGylated inteferon beta-1a). Monthly Avonex meets an unmet treatment need among people with MS because decreasing the frequency of interferon dosing can reduce side effects and make it easier for a person to continue taking the medication for the long term. To increase the exposure and reduce how quickly the drug clears from the body, a molecule called polyethylene glycol, or PEG for short, was added to Avonex to make it PEGylated interferon beta-1a.


How far along is monthly Avonex in the development process?

PEGylated inteferon beta-1a is currently being evaluated in a large, 2-year Phase 3 study (ADVANCE). Recognizing the importance of this development effort to people with MS, the FDA has given this new formulation of Avonex fast track designation, which will expedite the approval review process.


What evidence do we have that PEGylated inteferon beta-1a is effective?

Results from Phase 1a and 2b studies of PEGylated interferon beta-1a have demonstrated that a subcutaneous dose of 125 μg (μg and mcg are short for micrograms) taken every 2 or 4 weeks is comparable with an intramuscular dose of Avonex 30 μg taken weekly.

The 2-year, Phase 3 ADVANCE study, a randomized, double-blind, placebo-controlled study is currently underway. The study will include 1,500 people with relapsing forms of MS and will randomly assign participants to doses of PEGylated interferon beta-1a once every 2 or 4 weeks or placebo. After 1 year, people in the placebo group will be re-randomized to one of the two doses of PEGylated interferon beta-1a for the remainder of the study. Once the ADVANCE study is completed, participants will have the option to take part in an open-label extension study (ATTAIN).


What are the most common side effects with PEGylated inteferon beta-1a?

The most common side effects or adverse effects with monthly Avonex reported in Phase 1 and 2 studies were flu-like symptoms, including fever, chills, body aches, and muscle aches. These symptoms appeared to resolve with continued dosing of Avonex.

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Written by: Jonathan Simmons | Last reviewed: May 2015.