Disc Medicine Soars After Phase 3 Win Puts Rare-Disease Drug Back on Track for FDA
Bitopertin met every primary and secondary endpoint in APOLLO, eight months after the FDA turned down Disc’s first application.
Disc Medicine (NASDAQ: IRON) shares jumped about 60% early Monday, according to Investing.com, after its oral drug bitopertin succeeded on every endpoint in the Phase 3 APOLLO trial in erythropoietic protoporphyria (EPP), a rare genetic disease that makes sunlight exposure painful.
The result gives Disc a second shot at approval. In February, the FDA rejected the company’s application for accelerated approval, questioning whether the biomarker it relied on was reasonably likely to predict clinical benefit. Disc then cut about 20% of its workforce, and the stock had fallen 28% this year before Monday’s data, Endpoints News reported.
More Time in the Sun, Fewer Reactions
EPP causes a toxic, light-sensitive molecule called protoporphyrin IX (PPIX) to build up in the body, leading to severe pain, swelling and burning after sun exposure. Disc estimates the disease affects about 6,000 people in the U.S.
APOLLO enrolled 183 patients aged 12 and older, randomized to a 60 mg daily dose of bitopertin or placebo for six months. The drug hit both co-primary endpoints:
PPIX reduction: whole-blood PPIX fell 41.4% versus placebo (p<0.0001).
Pain-free time in light: average monthly pain-free time in light rose 12.2 hours versus placebo in month six (p=0.0010).
Every secondary endpoint was also positive, including fewer phototoxic reactions, and patient-reported quality-of-life measures improved significantly. Dizziness was the most common side effect, reported by half of treated patients, and was mild or moderate and generally transient. There were no adverse events above Grade 3.
“We could not have hoped for a better outcome,” said Disc CEO John Quisel.
A Disease-Modifying Approach
Bitopertin blocks glycine transporter 1, reducing the production of PPIX at its source. The only FDA-approved EPP therapy today is Clinuvel’s Scenesse, a surgically implanted hormone that stimulates melanin. Leo Pharma expects an FDA decision on dersimelagon, an oral drug with a similar tanning-based mechanism, in February.
Disc plans to resubmit its New Drug Application by the end of 2026, now seeking traditional approval, with an FDA decision expected by mid-2027. Wall Street analysts have projected peak sales of up to $1 billion, according to Endpoints.
The FDA’s original objection was that PPIX alone wasn’t proof patients would benefit. APOLLO answers that directly: PPIX fell, and patients spent more time in light without pain. That pairing is what makes the resubmission a stronger application than the first.
