iStock

By Marie Gendron

Shares of Acer Therapeutics (ACER)  plummeted by nearly 80% toward a record low after the pharmaceutical company said the Food and Drug Administration declined to approve its treatment for a genetic disorder that can cause blood vessels to fatally rupture.

The treatment, Edsivo (celiprolol), was developed to treat patients with vascular Ehlers-Danlos syndrome (vEDS), a rare but severe hereditary disorder of the connective tissue.

The stock finished 79% down at $4.12 in trading Tuesday.

In its response letter, the FDA has asked the company to conduct an "adequate and well-controlled trial" to determine whether Edsivo reduces the risk of clinical events in patients with vEDS. Edsivo's marketing application was based on data from an analysis of a 2010 European study involving 53 patients. The small group size, however, raised questions among experts about the adequacy of the trial results.

The company said it plans to request a meeting to discuss the FDA's response.

"We remain committed to working closely with the FDA to fully understand its response," Acer CEO and Founder Chris Schelling said in a statement. "We expect to respond to the FDA in the third quarter of this year."