The U.S. Food and Drug Administration issued a Complete Response Letter on February 13 2026 rejecting Disc Medicine’s bitopertin for the treatment of erythropoietic protoporphyria (EPP). The letter cited insufficient data to support accelerated approval and a lack of a clear link between the surrogate endpoint—reduction in whole‑blood metal‑free protoporphyrin IX (PPIX)—and clinical benefit.
The CRL highlights the FDA’s concern that the surrogate endpoint used in earlier trials does not demonstrate a reliable correlation with improved sunlight tolerance, the key clinical outcome for patients with EPP. Although Disc Medicine had previously secured support for accelerated approval based on PPIX reduction, the agency now requires definitive evidence from the ongoing Phase 3 APOLLO trial.
The decision delays the company’s anticipated launch of bitopertin, undermining projected revenue streams and extending the period during which the firm must fund its pre‑launch commercial infrastructure without product sales. Disc Medicine reported $791 million in cash, cash equivalents, and marketable securities as of December 31 2025, a reserve that the company believes will sustain operations through 2029.
"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," said John Quisel, President and Chief Executive Officer of Disc Medicine.
The company remains confident that the APOLLO trial will provide the necessary clinical data. Topline results are expected in the fourth quarter of 2026, with an updated FDA decision anticipated by mid‑2027. In the meantime, Disc Medicine continues to develop other pipeline candidates and monitors competitive developments, including Mitsubishi Tanabe Pharma’s dersimelagon and GondolaBio/Portal Therapeutics’ PORT‑77.
Investors reacted negatively to the CRL, reflecting concerns about the delayed revenue timeline and the need for additional clinical evidence before the drug can reach market.
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