Biohaven Shares Slide Premarket After FDA Rejects Vyglxia

By Colin Kellaher

Biohaven shares tumbled in premarket trading Wednesday after the U.S. Food and Drug Administration turned away the clinical-stage biopharmaceutical company's proposed Vyglxia treatment for the rare genetic disease spinocerebellar ataxia.

Biohaven late Tuesday said it received a so-called complete response letter from the FDA, indicating the agency won't approve the New Haven, Conn., company's application for Vyglxia in its current form.

Shares of Biohaven, which closed Tuesday at $13.95, were recently down 42% to $8.09 in premarket trading.

Biohaven said it is extremely disappointed with the FDA's action, which comes despite data from a pivotal three-year, real-world evidence study that showed a slowing of disease progression by 50%-70%.

The company said that despite the study achieving statistical significance in its primary and secondary outcome efficacy endpoints, the FDA cited issues that can be inherent to real-world evidence and external-control studies, including potential bias, design flaws, lack of pre-specification and unmeasured confounding factors.

Biohaven said it is committed to working with the FDA to find a path forward for Vyglxia, and that it plans to meet with the agency to discuss potential next steps.

In the meantime, the company said it is initiating portfolio and cost-optimization measures to prioritize three key, late-stage, clinical programs and reduce annual direct research-and-development spending by about 60%.

A green light would have made Vyglxia the first and only FDA-approved treatment for spinocerebellar ataxia, a life-threatening neurodegenerative disease characterized by progressive loss of voluntary motor control and atrophy of the cerebellum and brainstem.

Write to Colin Kellaher at colin.kellaher@wsj.com

(END) Dow Jones Newswires

November 05, 2025 06:36 ET (11:36 GMT)