By Siddhi Mahatole

(Reuters) -Shares of Biohaven fell more than 40% on Wednesday after the U.S. Food and Drug Administration declined to approve its experimental treatment for a rare brain disorder.

The company said late on Tuesday the FDA had issued a so-called “complete response letter” citing concerns with Biohaven’s use of real-world evidence and external control studies to support the marketing application for Vyglxia, also known as troriluzole.

The agency flagged potential bias, design limitations, and unmeasured or missing data.

Wall Street analysts said while the letter was disappointing, the outcome was unsurprising to many investors considering uncertainties around the evolving regulatory environment in the U.S.

“The outcome is clearly disappointing given troriluzole showed

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