FDA issues Complete Response Letter for Disc Medicine's bitopertin EPP treatment

Disc Medicine Inc. (NASDAQ: IRON) received a Complete Response Letter from the U.S. Food and Drug Administration regarding its New Drug Application for bitopertin as a treatment for erythropoietic protoporphyria.

The FDA acknowledged that Disc Medicine's AURORA and BEACON studies provided sufficient evidence that bitopertin significantly lowers PPIX levels and recognized strong mechanistic and biological plausibility supporting the use of the PPIX biomarker in protoporphyria. However, the agency concluded the trials did not show evidence of association between percent change in PPIX and sunlight exposure-based endpoints.

The FDA indicated it needs to see results from the ongoing Phase 3 APOLLO study before making a decision on approval. The agency stated that results from the APOLLO study could serve as evidence to support traditional approval.

"While our efforts at utilizing expedited pathways to get bitopertin to patients quickly have not come to fruition, we are continuing to pursue all avenues in support of FDA approval," said John Quisel, President and Chief Executive Officer of Disc Medicine.

Disc Medicine completed enrollment for the APOLLO trial in March 2026, several months ahead of schedule. The company expects topline data from the study in the fourth quarter of 2026. Upon completion of APOLLO, Disc Medicine plans to file a response to the Complete Response Letter and expects an updated FDA decision by mid-2027.

The company reported approximately $791 million in cash, cash equivalents, and marketable securities as of December 31, 2025, providing runway into 2029. Bitopertin is an investigational oral inhibitor of glycine transporter 1 designed to modulate heme biosynthesis.

Disc Medicine plans to request a Type A meeting with the FDA to review its approach and will host an investor call on February 17th to discuss the outcome.

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