The FDA issued a complete response letter rejecting Biohaven’s application for troriluzole in spinocerebellar ataxia after the company relied heavily on real‑world evidence (RWE) and an external control cohort. The agency cited concerns about potential bias, confounding and study design, according to coverage of Biohaven’s announcement and regulatory documents. Biohaven said it will seek a meeting with the FDA to clarify evidence requirements while reprioritizing its pipeline and cutting R&D spending. The decision illustrates growing regulatory scrutiny of RWE and external‑control strategies; agencies are increasingly demanding pre‑specified designs and robust bias mitigation before accepting non‑randomized evidence as primary support for approval.