The U.S. Food and Drug Administration issued a complete response letter for Biohaven’s troriluzole in spinocerebellar ataxia, and the company immediately moved to cut annual research spending by roughly 60%. FDA reviewers said the submission—largely supported by external historical controls and real‑world evidence—contained unresolved issues around bias, design and unmeasured confounding that undermined the strength of the efficacy claims. Biohaven’s leadership signaled a strategic reprioritization after the agency contact, announcing broad program cuts and a focus on other late‑stage assets. Management also said it will request a formal meeting with the FDA to clarify evidence expectations for a potential future filing. The decision underscores regulatory caution about using externally controlled trials and RWE as the primary basis for approval, and it will likely prompt sponsors of rare‑disease programs to reassess pivotal design and pre‑submission engagement strategies.