iStock

Shares of Acadia Pharmaceuticals Inc.  (ACAD - Get Report) fell sharply in after-hours trading Monday after the company said its supplemental treatment for schizophrenia failed to meet key benchmarks in a late phase trial.

Shares fell $3.43, or 13%, to $22.54 in recent after-hours trading.

The treatment, called Pimavanserin, "did not a achieve a statistically significant reduction" in symptoms in the phase 3 trial conducted with 396 patients, Acadia President Serge Stankovic said in a statement.

The company is continuing to evaluate the medication for other applications.