WATERTOWN, Massachusetts, June 9, 2026
Disc Medicine announced a regulatory update following a Type A meeting with the U.S. Food and Drug Administration (FDA) regarding the Complete Response Letter (CRL) issued for the New Drug Application (NDA) of bitopertin in erythropoietic protoporphyria (EPP). The company reported alignment with the FDA that the ongoing Phase 3 APOLLO trial, if successful, may serve as the basis for a CRL response and could potentially support traditional approval. Disc Medicine remains on track to submit its CRL response by the end of 2026, with a potential FDA decision anticipated in mid-2027.
FDA Provides Clear Regulatory Path Forward for Bitopertin
The FDA meeting provided Disc Medicine with important clarity regarding the future regulatory strategy for bitopertin. The agency agreed that positive results from the ongoing Phase 3 APOLLO study could support the company’s response to the CRL and potentially lead to traditional approval. This alignment reduces regulatory uncertainty and allows the company to focus on completing the pivotal study while preparing the necessary submission package. Management emphasized that the discussions reinforced confidence in the development program and the potential role of bitopertin as a treatment option for patients with EPP.
Phase 3 APOLLO Trial Remains Key Approval Study
The APOLLO trial is a global, randomized, double-blind, placebo-controlled Phase 3 study evaluating bitopertin in patients aged 12 years and older with erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP). The study is being conducted across sites in the United States, Canada, Europe, and Australia. Co-primary endpoints include measuring patients’ average monthly pain-free sunlight exposure and reductions in whole blood metal-free protoporphyrin IX (PPIX) levels after six months of treatment. Topline data from APOLLO are expected in the fourth quarter of 2026 and will play a critical role in determining the future approval pathway for the therapy.
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Bitopertin Targets Underlying Disease Biology
Bitopertin is an investigational oral inhibitor of glycine transporter 1 (GlyT1) designed to regulate heme biosynthesis. By modulating glycine availability during red blood cell production, the therapy aims to reduce the accumulation of toxic protoporphyrin compounds responsible for the severe light sensitivity experienced by patients with EPP and XLP. The drug has previously been evaluated in multiple clinical studies, including the Phase 2 BEACON, AURORA, and HELIOS trials. If approved, bitopertin has the potential to become the first disease-modifying therapy for erythropoietic porphyrias.
Disc Medicine Continues Focus on Rare Hematologic Diseases
Disc Medicine stated that it remains committed to advancing innovative treatments targeting disorders of heme biosynthesis and iron homeostasis. The company expects APOLLO results later this year and plans to submit its CRL response shortly thereafter. Success in the Phase 3 study could represent a major milestone for both Disc Medicine and patients with EPP, a rare genetic disease with limited treatment options. The company continues to build a pipeline of therapies aimed at addressing serious hematologic conditions through novel biological mechanisms.
Source: Disc Medicine press release
