Biohaven Pharmaceutical Holding Co Ltd. (BHVN) shares plummeted 10.43% in pre-market trading on Thursday, following an announcement that the U.S. Food and Drug Administration (FDA) has extended the review period for the company's New Drug Application (NDA) for troriluzole.

The FDA has pushed back the Prescription Drug User Fee Act (PDUFA) date for troriluzole, Biohaven's investigational treatment for spinocerebellar ataxia, a rare genetic disease. The regulatory agency's Division of Neurology 1 informed the company that it plans to hold an advisory committee meeting, although no date has been set. As a result of this extension, the FDA's decision regarding the NDA is now expected in the fourth quarter of 2025, a three-month delay from the original timeline.

This setback for troriluzole, a crucial drug in Biohaven's pipeline, has clearly unsettled investors. The extended review period not only postpones potential revenue from the drug but also introduces additional uncertainty into the approval process. While the FDA did not raise any new concerns in its communication with the company, the delay and the planned advisory committee meeting have sparked investor concerns. This sharp pre-market decline adds to Biohaven's woes, as the company's shares have already dropped about 47% since the start of the year, highlighting the challenges Biohaven faces in bringing its novel treatments to market.