Zafgen Inc. on Wednesday reported a second patient death in an ongoing study of its potential treatment for a rare genetic disorder linked to obesity.
The Boston-based company's shares plunged 56 percent in premarket trading Wednesday.
The biotechnology company said the patient died from a blockage in an artery in the lung, or blood clots, in the late-stage study of beloranib. It reported a previous death in October in the same study, but the cause is unknown.
The Food and Drug Administration placed a partial hold on the study following the first reported death.
Beloranib is the company's lead drug candidate and is aimed at treating the rare genetic disorder called Prader Willi syndrome. The condition has multiple symptoms and is linked to obesity.
The company said it is in discussions with the FDA to determine next steps for the program. Results of from another portion of the study are expected during the first quarter.
Zafgen shares dropped $8.95, or 56.2 percent, to $6.98 in premarket trading about an hour before the market open.