Yesterday, Elan (NYSE:ELN) and Biogen IDEC (NASDAQ:BIIB) announced that the Food and Drug Administration (FDA) has given Antegren priority review for the treatment of multiple sclerosis (MS). Back in May, Elan and Biogen filed their Biologics License Application with the FDA, which has 60 days to decide whether to formally accept the filing. That should occur by the end of July.

The priority review status means the FDA sets a target date for responding to the BLA submission at six months after the BLA filing, rather than the standard 10-month review time. Assuming the FDA accepts the BLA filing next month -- which is highly likely -- it should make a decision on the drug by the end of November if it stays within the priority review time frame. This is compared to the standard review time line, which would have led to an FDA decision by the end of March 2005.

Basically, the priority review designation bumps up the time line for approval. For a good review of the FDA's regulatory terminology, I recommend this article from Signals Magazine. The article includes a comment from an FDA official stating that the agency only does priority review after the BLA has been submitted and the data suggests the drug has therapeutic potential. I view priority review as an early vote of confidence from the agency.

At this time, all investors have to go on to evaluate Antegren is data from an earlier trial, published in the Jan. 2, 2003, issue of The New England Journal of Medicine. The data from that trial indicated a reduction in relapses and fewer new brain lesions developing in patients taking Antegren compared to the placebo group. Data from the phase 3 trial has not yet been released, but Elan's management has stated that it will make it available this October. That will be a highly anticipated event by both investors and the MS community.

For another Foolish perspective on Elan, see this Take from Jeff Hwang.

Fool contributor Charly Travers does not own shares of any companies mentioned in this article.