The FDA issued a complete response letter for Biohaven’s troriluzole New Drug Application for spinocerebellar ataxia, citing methodological issues with the company’s reliance on external control and real‑world evidence. The agency highlighted risks of bias, confounding and non‑prespecified analyses that undermined the submission’s robustness. In the wake of the CRL, Biohaven announced a major reprioritization: plans to cut annual research spending by roughly 60% and to refocus on a smaller set of late‑stage programs. Management said it will pursue regulatory dialogue to define data requirements for any future resubmission but indicated the CRL has immediate impacts on corporate planning and headcount. Why it matters: the FDA decision underscores the agency’s caution toward RWE‑based pivotal evidence and signals higher evidentiary bars for externally controlled rare‑disease submissions, with direct consequences for biotech financing and program continuity.