One of the potential growth drivers from AbbVie's (NYSE:ABBV) acquisition of Allergan was just shot down by the Food and Drug Administration. The agency issued a complete response letter (the FDA's euphemism for a rejection) for AbbVie's abicipar pegol, which Allergan and Switzerland-based Molecular Partners were developing for wet age-related macular degeneration.

The FDA decided the benefits of abicipar pegol didn't outweigh the side effects. Specifically, the agency is worried about the high number of patients who had inflammation in their eyes. In two phase 3 clinical trials, 15.1% to 15.7% of patients had inflammation in their eyes, compared with 0% to 0.6% of patients treated with Roche's (OTC:RHHB.Y) Lucentis.

The drugmaker plans to meet with the FDA to discuss the decision. "We are committed to working with the FDA to determine the appropriate next steps for abicipar pegol," Michael Robinson, vice president and global therapeutic area head for ophthalmology at AbbVie, said in a statement.

Doctor looking at a patient's eye.

Image source: Getty Images.

Abicipar pegol certainly has substantial potential, given that Regeneron Pharmaceuticals' (NASDAQ:REGN) Eylea, which treats wet age-related macular degeneration and related eye diseases, generated $4.6 billion in sales last year in the U.S. alone.

At this point, AbbVie's best hope might be to try to get the drug approved for patients with advanced cases of the disease, where the risk of having inflammation would be more justified given that the risk of doing nothing would eventually result in blindness.

Investors appear to be shaking off the news, with shares down just 1% at 1:13 p.m. EDT, less than the decline in the broader markets.