Disc Medicine, Inc. announced that the U.S. Food and Drug Administration (FDA) issued a Complete Response Letter (CRL) for the New Drug Application (NDA) for bitopertin as a treatment for patients with erythropoietic protoporphyria (EPP). Bitopertin has been under review for accelerated approval and as part of the Commissioner?s National Priority Voucher (CNPV) pilot program. Accelerated approval relies on (1) whether there is evidence of an effect on the proposed surrogate endpoint (% change in whole blood metal-free PPIX) and (2) whether the proposed surrogate endpoint, including the magnitude of change, is reasonably likely to predict a clinical benefit.
On the first point, the FDA agreed that AURORA and BEACON provided sufficient evidence that bitopertin significantly lowers whole blood metal-free PPIX. On the second, based on review of AURORA and BEACON results, the FDA concluded that the trials did not show evidence of association between percent change in PPIX and sunlight exposure-based endpoints, as measured in the trials, despite the strong mechanistic and biological plausibility supporting the use of the PPIX biomarker in protoporphyria. The FDA indicated results of the APOLLO study could serve as evidence to support traditional approval.
Disc believes the issue raised is readily addressable, given the APOLLO study is already well underway with topline data expected in fourth quarter. Disc plans to request a Type A meeting to review approach with the FDA. A blinded sample size re-estimation of the APOLLO study was conducted in January and no modifications to sample size were needed based on statistical analysis.
There has been significant patient and physician enthusiasm around the APOLLO trial, allowing Disc to complete trial enrollment in March 2026, several months earlier than expected. Upon completion of APOLLO, Disc would then file a response to the CRL and expect an updated FDA decision by mid-2027. Disc has approximately $791 million at December 31, 2025 in unaudited cash, cash equivalents, and marketable securities and maintains guidance of providing runway into 2029.
