The first new drug application for an experimental therapy meant to prevent Alzheimer's disease from worsening finally reached regulators on Wednesday. Biogen (BIIB -1.35%) has finally submitted a biologics license application (BLA) for aducanumab, a monthly infusion that prevents amyloid plaques from forming in the brain.

The company's requested a shortened six-month review instead of the usual 10-month process. The Food and Drug Administration has 60 days to let Biogen know if it will review the aducanumab BLA in any form.

As of 3:35 p.m. EDT today, Biogen shares were up just over 4.2%. 

An Alzheimer's disease first

If approved, aducanumab would become the first available Alzheimer's therapy intended to modify the course of the disease. Unfortunately, the evidence supporting Biogen's mission-critical BLA might not be enough to persuade the FDA that this treatment's benefits outweigh the risks it presents.

Doctor with a stethoscope on a stock chart.

Image source: Getty Images.

Biogen ran a pair of pivotal studies with aducanumab, only one of which measured a significant benefit with regard to patients' dementia ratings after treatment with the highest dose tested. In both pivotal studies, though, more than one-third of patients presented signs of brain swelling, compared to just 2.7% of patients given a placebo. 

An estimated 5 million Americans have Alzheimer's at the moment, and by 2050 this figure is expected to reach 13.8 million. Sadly, the risks aducanumab presents will most likely prevent the FDA from granting the drug an approval to treat any of those patients.

While the vast majority of brain swelling cases were relatively innocuous, this isn't a cancer drug. Aducanumab wasn't effective when used by patients in later stages of this slowly progressing disease. If approved, aducanumab treatment would be used long term by relatively healthy Alzheimer's patients in the earliest stages of the disease.