U.S. health regulators Friday approved Avanir Pharmaceuticals Inc’s Zenvia, a treatment for pseudobulbar affect, or involuntary emotional expression syndrome, a neurological disorder in which patients cannot control outbursts of crying or laughter. Zenvia is the first drug approved for the treatment of the little known, but not that rare, condition

Shares of Avanir Pharmaceuticals soared 112 percent as the news spread. Peak sales for the new drug are projected to hit $350 million to $500 million and some analysts quickly began buzzing about a potential takeover in the wake of an approval.

The approval marks a major success for Avanir, which had to go back to the drawing board four years ago after the FDA told the developer that it was worried about the potential impact of one of the chemical ingredients in the therapy. Investigators then cut the dose level of quinidine by a third and reported more than a year ago that the new formulation of Nuedexta, once called Zenvia, met the primary endpoint in a new trial.

More than two million people with neurological conditions like Lou Gehrig’s disease and Alzheimer’s suffer from involuntary emotional outbursts, crying and laughing jags that occur with no warning. “We like to refer to PBA as one of the most common diseases that people have never heard of,” Avanir CEO Keith Katkin told the New York Times.