FDA Wants Clarity From Valeant

"There has been some evidence that Zelapar ... has an even lower risk than selegiline, though this data may not have been enough to satisfy the FDA," a BioMedTracker report says. Sagient doesn't own shares or have a financial relationship with companies it evaluates.

At best, Zelapar could reach the market in a few months, Sagient says. "In the worst-case scenario, an additional [clinical] trial could be required to support efficacy or safety, which could take years," the firm says.

Zelapar belongs to a class of drugs called selective irreversible monoamine oxidase type B inhibitors, or MAO-B inhibitors.

MAO-B is an enzyme that breaks down dopamine, a chemical produced in the brain to help maintain balance and movement. When dopamine-producing cells die, people develop tremors and other neurological impairments. MAO-B inhibitor drugs try to thwart the damage caused by MAO-B enzymes, but their impact usually doesn't last very long.

Zelapar is the second MAO-B inhibitor to recently receive a conditional approval notice from the FDA. Two months ago, Teva Pharmaceutical Industries (TEVA Quote) got conditional clearance for Agilect.

Teva wouldn't discuss details. At the time, the company said "there remain a number of issues that Teva believed it had resolved with its submissions, but as to which the FDA continues to have concerns." Sagient Research speculates that the government agency may have raised food-related concerns about the Teva drug, too.