Biogen Idec announced Tuesday that the European Commission

approved an injectable pen version of its multiple sclerosis therapy Avonex (interferon beta-1a)

for patients who have experienced a single demyelinating event or who have relapsing forms of the disease.

The single-use Avonex pen uses the already approved Avonex prefilled syringe, but with a shorter needle.

The approval was based in part on a late-stage study involving patients with MS who had previously used the Avonex prefilled syringe.

Data showed that the overall success rate for patients using the Avonex pen was 89 percent and 94 percent of patients said they preferred the pen over the prefilled syringe version.

Biogen Idec said it will start making the pens available in Europe over the next few weeks. Company officials noted that further filings are also planned in other markets. Avonex garnered worldwide sales of $2.5 billion in 2010.