Disc Medicine reports bitopertin Phase 3 success in EPP

Both main endpoints were met in a Phase 3 erythropoietic protoporphyria trial as Disc Medicine, Inc. NASDAQIRON reported positive bitopertin results on Monday. The 183-patient APOLLO study also met every secondary endpoint, supporting a planned FDA resubmission by the end of 2026.

Disc shares NASDAQIRON rose 36.79 per cent to US$77.75 in New York at 12:11 p.m. EDT on Monday, according to Google Finance.

Disc is a clinical-stage blood-disease drug developer based in Watertown, Mass., with a portfolio focused on red-blood-cell biology.

The results follow an earlier FDA rejection of bitopertin. In its June 9 account of an FDA meeting, Disc said the agency agreed a successful APOLLO study could support a response to its complete response letter and potentially traditional approval.

APOLLO Met Both Primary Endpoints

The double-blind study enrolled patients aged 12 or older with erythropoietic protoporphyria, or EPP, including X-linked protoporphyria. Participants were randomized in a one-to-one ratio to receive 60 milligrams of oral bitopertin or placebo daily for six months.

Whole-blood metal-free protoporphyrin IX, or PPIX, fell 41.4 per cent versus placebo, with a p value below 0.0001. Average monthly time in light without pain increased by 12.2 hours versus placebo during the sixth month, with p=0.0010.

The clinical endpoint measures functional benefit alongside the biochemical reduction. Disc had identified both measures as co-primary endpoints in its June account of the FDA meeting, before reporting the results.

Phototoxic reaction frequency declined over the treatment period, while cumulative time in light without pain increased; both secondary endpoints had p values below 0.0001. The topline summary did not quantify the reduction in reaction frequency.

Time in sunlight before early symptoms also improved in adults, with p=0.0077. Patient-rated global impressions of change and severity improved with p values below 0.0001, but Disc classified those quality-of-life measures as exploratory.

Dizziness affected 50 per cent of bitopertin recipients and was mild or moderate and generally transient; Disc reported no treatment-emergent adverse events above Grade 3. Its topline safety summary did not give a placebo dizziness rate or discontinuation totals by treatment arm.

"These results are compelling evidence of the clinical benefit of a mechanism aimed at reducing the production of PPIX, the fundamental cause of disease," Disc chief medical officer Will Savage said in the release.

SCENESSE Is Already Approved In Canada

An established EPP competitor is CLINUVEL Pharmaceuticals Ltd ASXCUV OTCMKTSCLVLY, whose July 13 notice announced Canadian approval of SCENESSE. APOLLO compared bitopertin with placebo, so its results do not establish comparative efficacy against SCENESSE.

Privately held Tanabe Pharma Corporation, which came under Bain Capital ownership in 2025, has another oral candidate, dersimelagon. Tanabe's Aug. 18 announcement said it submitted an FDA application for EPP and X-linked protoporphyria on June 30, putting another oral treatment ahead of Disc's planned resubmission.

The broader State Street SPDR S&P Biotech ETF NYSEARCAXBI rose 2.34 per cent to US$147.69 at 12:13 p.m. EDT on Monday, according to Google Finance.

Disc's July 30 financial report put cash, cash equivalents and marketable securities at US$717.7 million on June 30. Management said that balance would fund operating plans into 2029, beyond its anticipated bitopertin decision.

The next regulatory step is Disc's planned resubmission by the end of 2026. Disc anticipates an FDA decision by mid-2027; that timing is the company's expectation, rather than an agency-assigned decision deadline.