The U.S. Food and Drug Administration issued a complete response letter rejecting Biohaven’s New Drug Application for troriluzole in spinocerebellar ataxia, citing concerns about real‑world evidence and externally controlled trial design. The decision followed prolonged exchanges between the company and FDA and highlights regulatory skepticism about using natural‑history controls as primary evidence. In reaction, Biohaven disclosed plans to restructure and sharply reduce R&D spending—targeting roughly a 60% cut in annual research budgets—and to reprioritize its pipeline toward three late‑stage programs. Biohaven executives criticized the agency’s application of RWE standards while the FDA urged additional discussions on acceptable evidence for future filings. Investors reacted sharply to the CRL, reflecting broader market sensitivity to regulatory risk in rare‑disease development.