FDA Rejects Accelerated Approval for Disc Medicine's Bitopertin for EPP
The FDA rejected accelerated approval for Disc Medicine's bitopertin for erythropoietic protoporphyria, citing insufficient evidence that biomarker reductions translate to clinical benefit. The agency wants to see results from the ongoing Phase 3 APOLLO trial before considering traditional approval, pushing any decision to at least mid-2027. Disc Medicine plans to address FDA concerns with APOLLO data expected in Q4 2026.
The U.S. Food and Drug Administration has issued a complete response letter rejecting accelerated approval for Disc Medicine's new drug application for bitopertin as a treatment for erythropoietic protoporphyria. The agency acknowledged that Phase 2 AURORA and BEACON data showed bitopertin significantly lowers the PPIX biomarker, but found no sufficient evidence that reductions in PPIX translated into improved sunlight-exposure outcomes in those trials.
The FDA indicated that results from the ongoing Phase 3 APOLLO trial could support traditional approval, effectively pushing any U.S. decision on bitopertin into at least mid-2027. The accelerated approval process required evidence of impact on a surrogate endpoint, the percentage change in whole blood metal-free protoporphyrin IX, and whether this change is likely to predict clinical benefit.
Disc expects issues raised by the FDA can be addressed through data from the APOLLO study, with topline data anticipated in the fourth quarter of 2026. The company intends to seek a Type A meeting with the FDA and plans to respond to the complete response letter, anticipating receiving a revised decision by mid-2027.
The last participant has been randomized and dosed in the Phase 3 APOLLO study of bitopertin in erythropoietic protoporphyria, with the study size expanded to 183 participants due to patient and physician demand. Results of the APOLLO study are expected in Q4 2026.
Bitopertin is an investigational, clinical-stage, orally administered inhibitor of glycine transporter 1 that is designed to modulate heme biosynthesis. Disc is developing bitopertin as a potential treatment for a range of hematologic diseases including erythropoietic porphyrias, where it has potential to be the first disease-modifying therapy.
The company held about $791 million in cash and securities at year-end 2025 and maintains it has funding runway into 2029. In January 2025, Disc raised $225.5 million via an upsized public offering to support its pipeline, which included bitopertin.