The FDA rejected Disc Medicine’s bitopertin application, marking a high-profile rebuke of a rare-disease submission that had been expedited under a new priority-review voucher program. STAT reported the agency cited uncertainties about the correlation between the blood-based biomarker used in trials and actual clinical benefit. The agency’s decision sent Disc shares sharply lower and raises questions about the durability of biomarker-based approval pathways. A second report from MedCity News confirmed the FDA posted a formal rejection letter and noted the drug — intended for a porphyria-related indication — had been routed through the commissioner’s new accelerated-review mechanism. Regulators stressed that surrogate or biomarker endpoints must show a clear and clinically meaningful link to patient outcomes. The twin accounts underscore immediate regulatory risk for companies relying on novel biomarkers for accelerated approvals.