Biogen Idec ( BIIB) and Irish drugmaker Elan ( ELN) Monday said the Food and Drug Administration had accepted their biologics license application for Antegren, the promising multiple sclerosis treatment. The FDA granted Antegren priority review status. As a result, the companies anticipate action six months from the submission date rather than the 10 months for a standard review. On May 25, 2004, the companies announced they had previously submitted the application. The FDA made its decision in June, according to Monday's news release. In February, the two companies stunned investors in announcing they would seek U.S. regulatory approval a year ahead of schedule after one year of phase 3 trials produced surprisingly positive test results. The companies, however, also said they would continue the testing program despite the decision to apply for early FDA approval. Multiple sclerosis is a chronic disease of the central nervous system that affects approximately 400,000 people in North America and approximately one million people worldwide, the majority of whom are women, according to the companies. Symptoms include vision problems, loss of balance, numbness, difficulty walking and paralysis. Shares of Biogen Idec, which reports quarterly earnings Wednesday, fell $1.63, or 2.9%, to $53.76. Elan's slumped $1.82, or 8.3%, to $19.98 in trading volume, twice the daily average of about 4.2 million shares.