Disc Medicine Inc (NASDAQ:IRON) saw its shares drop sharply, falling 21.1% on Friday after the U.S. Food and Drug Administration delivered a Complete Response Letter (CRL) regarding the company’s candidate therapy bitopertin for erythropoietic protoporphyria (EPP).
The CRL states that the FDA needs data from the ongoing Phase 3 APOLLO trial before it can make an approval determination. While the agency acknowledged that bitopertin produces a significant reduction in protoporphyrin IX (PPIX) levels and described the biomarker’s biological plausibility in protoporphyria, it concluded that prior studies did not sufficiently demonstrate a connection between reductions in PPIX and endpoints based on sunlight exposure.
Disc Medicine had been pursuing accelerated approval for bitopertin under the FDA’s Commissioner’s National Priority Voucher pilot program. Following the CRL, the company said it now expects to complete the APOLLO trial and report topline results in the fourth quarter of 2026. Disc Medicine added that it anticipates responding to the CRL and receiving an updated FDA decision by mid-2027.
In comments included with the company update, John Quisel, President and CEO of Disc Medicine, said: "We are committed to delivering bitopertin to patients, knowing how critical this potentially disease-modifying therapy is to the EPP community. 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."
The company noted that enrollment in the APOLLO trial is progressing ahead of schedule, with completion expected in March 2026. Disc Medicine reported approximately $791 million in cash, cash equivalents, and marketable securities as of December 31, 2025, and said it expects those resources to provide a runway into 2029.
The immediate market response was pronounced, reflected in the one-day share price decline after the regulatory communication. Moving forward, the regulatory timeline is tied to the APOLLO trial’s results and the company’s formal response to the CRL, with the next major milestones cited as topline data in late 2026 and a potential updated FDA decision by mid-2027.
What to watch next
- Completion of APOLLO enrollment, currently expected in March 2026.
- Topline APOLLO results expected in the fourth quarter of 2026.
- Company response to the CRL and an updated FDA decision anticipated by mid-2027.