Disc Medicine Eyes Mid-2026 Bitopertin Approval as EPP Trial Demand Surges

Key Points

• Disc Medicine said enrollment in its APOLLO confirmatory study for bitopertin in EPP reached 183 patients, above the original 150-patient target, reflecting strong demand in both the U.S. and Europe.
• The company expects APOLLO data in Q4 and plans a Type A meeting with the FDA to determine the resubmission path after a prior complete response letter; management still sees a potential approval around mid-2026.
• CEO John Quisel said the EPP patient pool may be larger than traditional estimates, and that adolescent data from APOLLO could support an initial label down to about age 12 if results are sufficient.

Disc Medicine NASDAQ: IRON Chief Executive Officer John Quisel said patient demand for the company’s bitopertin program in erythropoietic protoporphyria, or EPP, remains strong after the company enrolled 183 patients in the APOLLO confirmatory study, above its original target of 150.

Speaking at an H.C. Wainwright event hosted by Senior Analyst Doug Tsao, Quisel said the study’s enrollment pace reflected “tremendous demand and enthusiasm” in both the United States and Europe. He said U.S. enrollment was stopped earlier than expected as the company pursued an accelerated approval pathway, while European sites opened in November and quickly contributed enough patients to reach the 150-patient target by midwinter.

Quisel said Disc allowed additional enrollment because some European sites had not previously had access to bitopertin and had patients and physicians eager to participate. “Honestly, we would have enrolled more people because of the high level of interest,” he said.

Disc Sees EPP Patient Population as Larger Than Traditional Estimates

Quisel said the company’s clinical trial experience supports the view that the EPP patient population may be larger than some traditional epidemiology estimates suggest. He noted that academic papers have estimated prevalence at roughly 1 in 100,000 to 1 in 50,000, implying about 3,000 to 6,000 patients in the United States. He also cited a genetic analysis based on UK Biobank data from Massachusetts General Hospital that suggested the U.S. population could be closer to 20,000.

Disc’s own review of claims databases identified 14,000 patients in the U.S. who received care under the dedicated ICD-10 code for EPP, Quisel said. Of those, he described an “inner core” of about 6,000 patients who appeared more engaged in medical care.

Quisel said the rapid enrollment of multiple EPP studies, including Disc’s programs and trials for other therapies, suggests patients are “showing up” when treatment opportunities are available. He said many patients receive a diagnosis but then return to managing the disease largely by avoiding sunlight, particularly when therapeutic options are limited.

FDA Meeting to Focus on Resubmission Path for Bitopertin

Disc previously received a complete response letter from the U.S. Food and Drug Administration for its bitopertin application under the accelerated approval process. Quisel said the agency raised questions about the correlation between PPIX levels and disease symptoms, and acknowledged that the APOLLO study could address the issue.

Quisel said the company expects APOLLO data in the fourth quarter of this year. He said the main purpose of an upcoming Type A meeting with the FDA is to discuss how the Phase 3 data should be analyzed and packaged for a response to the CRL or a resubmission of the new drug application.

“Either way, then it sets up a six-month review period,” Quisel said, adding that the company’s guidance points to a potential approval around the middle of next year.

Quisel said Disc had expanded its organization in preparation for a potential near-term launch before the CRL and later reduced that team. He said the company retained about one-third of the launch-related team to continue market development, physician outreach and medical affairs work ahead of a possible future launch.

Adolescent Data Could Support Broader Initial Label

Quisel also discussed the pediatric and adolescent opportunity in EPP. He said there are currently no approved therapies for adolescents or younger pediatric patients. Disc included four adolescents in its Phase 2 program across the U.S. and Australia, and APOLLO has open enrollment for adolescents.

Quisel said the Phase 3 trial should provide a meaningful adolescent data set in addition to adult data. He said there is “no mechanistic reason” the disease would behave differently in adolescents and said Disc hopes an initial label could cover patients down to about age 12. He added that plans for younger pediatric patients remain in place.

DISC-0974 Data Expected at Medical Meetings

Turning to DISC-0974, Quisel said interim data from the RALLY-MF Phase 2 trial in myelofibrosis showed responses across patients receiving JAK inhibitors, including momelotinib and pacritinib, as well as patients not taking JAK inhibitors. He said enrollment of anemic patients already treated with momelotinib indicated that anemia remains an unmet need despite newer therapies.

Quisel said Disc’s upcoming presentations at ASCO and EHA will provide additional data. He said earlier data showed efficacy in non-transfused patients and encouraging results in low transfusion burden patients, while the high transfusion burden group had limited patient numbers. A recent company update showed three of six responders in the high transfusion burden group, which Quisel described as roughly consistent with response rates across groups.

Disc has stopped development of DISC-0974 in chronic kidney disease, Quisel said, after mixed data suggested responses may depend partly on endogenous EPO levels. He said the company continues to see promise in inflammatory bowel disease, where patients often have significant anemia, fatigue and high EPO levels. He also cited mouse model data showing improvements in anemia and signs of inflammatory disease improvement, while cautioning that translation to humans remains uncertain.

DISC-3405 Programs Target PV and Sickle Cell Disease

Quisel said Disc is positioning DISC-3405, a monoclonal antibody, as a potential iron-restriction therapy for polycythemia vera. He said rusfertide has helped establish that iron restriction can benefit PV patients, while Disc aims to offer a less frequent dosing approach with a favorable safety and tolerability profile.

Disc is also starting a study of DISC-3405 in sickle cell disease. Quisel said the theory of iron restriction in sickle cell disease has generated interest, noting that phlebotomy is already being used clinically in some patients as a “crude” way to achieve iron restriction. He said Disc believes a drug-based approach could provide benefit and potentially combine with other treatment mechanisms.

About Disc Medicine NASDAQ: IRON

Disc Medicine, Inc NASDAQ: IRON is a clinical-stage biotechnology company focused on discovering and developing precision medicines that restore normal cellular function in severe genetic and acquired diseases. The company employs a chemistry-driven approach to identify small molecules that selectively modulate RNA-binding proteins or splicing regulatory pathways. By leveraging proprietary screening and medicinal chemistry platforms, Disc Medicine aims to address diseases with high unmet medical needs and limited treatment options.

The company's pipeline is anchored by lead programs targeting neuromuscular and hematological disorders.

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