4 November 2025 - Biohaven today announced that it has received a complete response letter from the US FDA for the new drug application seeking approval of Vyglxia (troriluzole) for the treatment of spinocerebellar ataxia.

The FDA issued a complete response letter despite Study 206-RWE being reviewed by FDA and achieving statistical significance in the study's pre-specified primary and secondary outcome efficacy outcomes. 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.