Biogen Idec has filed a pegylated version of its blockbuster Avonex, called Plegridy, with the US Food and Drug Administration for relapsing forms of multiple sclerosis.

The submission was based on the results from the first year of a Phase III study which demonstrated that Plegridy (peginterferon beta-1a), met all primary and secondary endpoints by significantly reducing disease activity including relapses, disability progression and brain lesions compared to placebo. It also has a good safety and tolerability profile.

The benefits of Plegridy are that it will require less frequent injections and they will be administered subcutaneously. It should therefore be less painful, seeing as Avonex (interferon beta-1a) is given intramuscularly.

Biogen's R&D chief Douglas Williams said that based on the efficacy and safety Plegridy has demonstrated, "in addition to its less frequent dosing schedule, it has the potential to become a preferred interferon treatment option". A filing is expected in Europe in the next few weeks.

Approval would add to Biogen's already-mighty MS portfolio, which also includes Tysabri (natalizumab) and potentially the jewel in the crown, the oral drug Tecfidera (dimethyl fumarate).