What happened

Shares of Biogen (NASDAQ:BIIB) were jumping 4.3% higher as of 3:42 p.m. EDT on Wednesday after rising as much as 9.9% earlier in the day. The gain came after the biotech announced that it had completed the submission of a biologics license application (BLA) to the U.S. Food and Drug Administration (FDA) for aducanumab as a treatment for Alzheimer's disease.

So what

The regulatory filing for aducanumab marked a critical milestone for Biogen. It's not an exaggeration to state that much of the future fortunes for the biotech stock ride on success for the drug.

Businessman holding blocks in his hand that spell FDA

Image source: Getty Images.

It's been a wild ride to get to this point. At one point, some analysts thought that aducanumab could generate peak annual sales in the ballpark of $20 billion if approved. However, hopes were dashed last year after Biogen halted two late-stage studies of aducanumab after an independent data-monitoring committee determined that the experimental drug was unlikely to be effective.

But that wasn't the end of the story for aducanumab. In October 2019, Biogen announced one of the biggest bombshells in biotech history: It intended to file for FDA approval after all. The company made the decision based on a new analysis of a larger data set from its two late-stage studies.

Biogen now has hopes that the FDA could even grant priority review designation for aducanumab. If the designation is granted, the FDA would complete its review of aducanumab within six months of acceptance of the BLA instead of the usual 10 months.

Now what

The ball is now in the FDA's court. The agency has up to 60 days to determine whether or not it will accept Biogen's BLA for aducanumab. In the meantime, Biogen is also working with regulatory authorities in Europe, Japan, and elsewhere about filing for approval of the drug.