Disc Medicine has received a Complete Response Letter (CRL) from the FDA for bitopertin, an oral drug to treat erythropoietic protoporphyria (EPP), despite bitopertin being under review for accelerated approval in the Commissioner’s National Priority Voucher (CNPV) pilot program.
In the Aurora and Beacon trials, bitopertin significantly lowered whole blood metal-free PPIX, which meets the FDA requirement of evidence of an effect on the proposed surrogate endpoint. However, accelerated approval also requires the proposed surrogate endpoint to be reasonably likely to predict a clinical benefit. The FDA determined that the results of the trials did not demonstrate an association between the percent change in PPIX and sunlight exposure-based endpoints.
The FDA has said it will need to see the results of the phase 3 Apollo study, which is currently in progress, before it is able to come to a decision. The study may be able to provide evidence to support a traditional approval. Topline data from this study is expected for Q4 2026.
The FDA announced the new CNPV program, designed to shorten drug review times for companies "aligned with U.S. national priorities” in June 2025. The voucher can be redeemed by drug developers to participate in a priority program that shortens its review time from approximately 10-12 months to 1-2 months following a sponsor’s final drug application submission.