FDA Delay for Disc Medicine’s Bitopertin: What’s Next for EPP Treatment?
Watertown, Massachusetts – Disc Medicine (NASDAQ:IRON) faced a setback this week as the U.S. Food and Drug Administration (FDA) issued a Complete Response Letter (CRL) for bitopertin, its investigational treatment for erythropoietic protoporphyria (EPP). While the news sent Disc Medicine’s stock price tumbling, the path forward isn’t entirely closed, with the ongoing Phase 3 APOLLO study holding the key to potential approval.
Understanding the FDA’s Concerns
The FDA acknowledged that data from the AURORA and BEACON trials demonstrated bitopertin’s ability to significantly lower protoporphyrin IX (PPIX) levels – a key biomarker in EPP. Still, the agency expressed concern that these trials didn’t definitively show a clear link between PPIX reduction and improvements in sunlight exposure-based symptoms, despite the strong biological rationale for such a connection. Essentially, the FDA wants more evidence that lowering PPIX translates to real-world benefits for patients.
The APOLLO Study: A Pivotal Moment
The FDA has indicated that the results of the ongoing Phase 3 APOLLO study could provide the necessary evidence for traditional approval. This study is already showing promising signs, with enrollment completed several months ahead of schedule in March 2026, fueled by strong enthusiasm from both patients and physicians. Topline data from APOLLO is anticipated in the fourth quarter of 2026.
“We are committed to delivering bitopertin to patients, knowing how critical this potentially disease-modifying therapy is to the EPP community,” stated John Quisel, J.D., Ph.D., President and CEO of Disc Medicine. “While our efforts at utilizing expedited pathways to obtain bitopertin to patients quickly have not arrive to fruition, we are continuing to pursue all avenues in support of FDA approval.”
What is EPP and Why is Bitopertin Essential?
Erythropoietic protoporphyria is a rare genetic disorder that causes painful skin reactions to sunlight. It’s caused by a deficiency in an enzyme needed to process heme, a component of hemoglobin. This leads to a buildup of PPIX in the blood and skin, causing photosensitivity and pain. Currently, treatment options are limited to managing symptoms, with no disease-modifying therapies available.
Bitopertin works by inhibiting glycine transporter 1 (GlyT1), aiming to modulate heme biosynthesis and reduce PPIX levels. If approved, it could represent a significant advancement in the treatment of EPP, offering a potential way to address the underlying cause of the disease.
Financial Outlook and Next Steps
Disc Medicine reported approximately $791 million in cash, cash equivalents, and marketable securities as of December 31, 2025, providing a financial runway into 2029. The company plans to request a Type A meeting with the FDA to discuss its approach and the APOLLO study results. If all goes well, Disc anticipates submitting a response to the CRL upon completion of APOLLO and expects an updated FDA decision by mid-2027.
Did you understand? The Commissioner’s National Priority Voucher (CNPV) pilot program, under which bitopertin was previously reviewed, is designed to incentivize the development of drugs for rare diseases.
Frequently Asked Questions
Q: What is a Complete Response Letter (CRL)?
A: A CRL means the FDA is not ready to approve a drug. It outlines the reasons for the delay and what the company needs to do to address the FDA’s concerns.
Q: What is the APOLLO study?
A: APOLLO is a Phase 3 clinical trial designed to confirm the efficacy of bitopertin in treating EPP. It’s considered crucial for potential FDA approval.
Q: What does this mean for patients with EPP?
A: While Here’s a setback, the ongoing APOLLO study offers hope for a potential recent treatment option in the future.
Q: What is PPIX?
A: Protoporphyrin IX is a chemical that builds up in the blood and skin of people with EPP, causing sensitivity to sunlight.
Pro Tip: Stay informed about clinical trials and research advancements in rare diseases through organizations like the National Organization for Rare Disorders (NORD).
Investors interested in learning more are encouraged to register for Disc Medicine’s investor call on February 17th. Further details can be found on the company’s investor relations website: https://ir.discmedicine.com/
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