Biohaven’s recent troubles center on VYGLXIA – its lead drug candidate for spinocerebellar ataxia, a degenerative brain disorder that currently has no approved treatmentreuters.com. On November 4, 2025, after market close, Biohaven announced that the FDA had issued a Complete Response Letter rejecting the company’s New Drug Application. This CRL cited multiple concerns with Biohaven’s data: potential bias, design limitations, lack of pre-specification, and unmeasured confounding factors in the supporting studiesstocktwits.comstocktwits.com. In simpler terms, the FDA was uneasy with how Biohaven ran and analyzed its trials – particularly its use of real-world evidence and an external control group instead of a standard placebo-controlled trialreuters.com.
