The FDA rejected Disc Medicine’s bitopertin application for porphyria, citing uncertainties about the link between the blood biomarker used in trials and clinical benefit. The agency’s decision clears the letter publicly and sent Disc shares sharply lower. STAT and other outlets reported the agency’s rejection and noted the drug had been routed through a new priority review voucher program. The agency flagged the surrogate endpoint’s correlation with patient outcomes as insufficient to establish efficacy. Disc had hoped the expedited pathway would accelerate review; the FDA’s refusal underscores renewed skepticism of biomarker-based approvals and of the new voucher mechanism that had been used earlier this cycle.