Biogen ( BGEN) said the Food and Drug Administration has approved a new prefilled syringe for Avonex, the company's treatment for people with multiple sclerosis. Biogen expects the prefilled syringe to be available in August and replace the currently marketed form of Avonex. As with the current form of Avonex, the new formulation will be indicated to slow the progression of disabilities and reduce the frequency of relapses in MS patients. Avonex is administered once a week by intramuscular injection. Shares of Biogen closed Wednesday at $42.37 in Nasdaq trading.