The FDA has rejected Biohaven’s approval request for troriluzole in spinocerebellar ataxia, delivering a complete response letter that questioned the real‑world evidence (RWE) and externally controlled analyses the company submitted. The agency cited potential bias, design flaws, lack of pre‑specification and unmeasured confounding in the RWE study, and recommended a meeting to outline evidence expectations for any future filing. Biohaven had previously touted three‑year RWE findings as supportive; the FDA found the submission insufficient. The rejection prompted a severe market reaction—Biohaven stock dropped roughly 44% premarket—and forced the company to prioritize other assets and cut R&D plans. Regulators’ skepticism about RWE as a primary basis for approval is likely to shape strategies across developers navigating accelerated or non‑randomized pathways.