Rare Disease New Drug Halted... FDA Suspends Review of Light-Sensitive Skin Disorder Treatment

Disc Medicine, Inc. (NASDAQ: IRON) announced on February 13 that it received a Complete Response Letter (CRL) from the U.S. Food and Drug Administration (FDA) for its investigational new drug application for bitopertin, a candidate therapy for erythropoietic protoporphyria (EPP). While the FDA acknowledged the reductions in protoporphyrin IX observed in the AURORA and BEACON Phase 2 studies, it determined that the company has not sufficiently demonstrated how these biomarker changes translate into clinically meaningful improvements in sunlight-related symptoms. Disc Medicine plans to complete enrollment in its ongoing Phase 3 APOLLO trial by March 2026 and, based on top-line data expected in the fourth quarter of 2026, will supplement its submission and target a mid-2027 re-review. The company reported cash reserves of approximately $791 million as of year-end 2025 (around 1.07 trillion KRW), which it expects to support operations through 2029.

Following the CRL announcement, Disc Medicine’s stock tumbled more than 20% in a single day, prompting the company to hold a conference call to discuss the FDA’s decision and outline its strategic response to investors. Investors have been closely watching bitopertin, especially after the therapy received Fast Track designation and a Priority Review voucher from the FDA—factors that had fueled expectations for an accelerated approval in 2025 or 2026. Market attention will now shift to the Phase 3 APOLLO data and any additional clinical endpoints the company may establish.

Headquartered in Massachusetts, Disc Medicine is a clinical-stage biopharmaceutical company focused on novel therapies for blood disorders with high unmet needs. Its lead programs target rare genetic conditions such as erythropoietic protoporphyria and myelofibrosis-related anemia, as well as hematologic disorders like polycythemia vera. In addition to bitopertin, the company’s pipeline includes candidates such as DISC-0974 and DISC-3405 as it seeks to broaden its portfolio in the erythrocyte and iron metabolism disease space. Disc Medicine is operating in an increasingly competitive landscape, as smaller biotech firms vie for leadership in rare diseases and adjacent hematologic oncology markets.