Bitopertin cleared both co-primary goals and every secondary one in a rare light-sensitivity disorder, adding a patient-experience measure that Disc says addresses the FDA's concern. Shares rose about 36% to about $77.50 after briefly touching $93 shortly after the release, and the company expects an FDA decision by mid-2027.
In February, the Food and Drug Administration told Disc Medicine that a blood test alone was not enough. On Monday, the company produced the rest of its case.
In APOLLO, the late-stage study in erythropoietic protoporphyria, a rare disorder that makes exposure to light painful, the oral drug "met all its primary and secondary endpoints," Disc said. The 183-patient study randomized patients to bitopertin or placebo for six months. On the first co-primary endpoint, levels of protoporphyrin IX, the toxic compound behind the disease, fell 41.4% versus placebo (p<0.0001). On the second, patients on the drug gained an average of 12.2 more hours a month in light without pain during month six than those on placebo (p=0.0010).
Every secondary endpoint was also statistically significant, as were patients' own assessments of their condition. Dizziness was the most common side effect, affecting 50% of patients on the drug; Disc said it was mild or moderate and generally short-lived, and there were no adverse events above Grade 3.
The company intends to refile with the FDA before the year is out and expects the agency to rule by the middle of 2027.
Why the second endpoint matters
The FDA rejected Disc's first application on Feb. 13, with its main objection centered on whether the blood marker was a sufficient stand-in for clinical benefit. The agency said it needed to see the APOLLO results. In June, Disc said it had agreed with the FDA that a successful APOLLO could serve as the basis for its response.
APOLLO now pairs the biomarker with a measure of what patients experience. Disc presents that as the answer to the stated reason for the rejection; the FDA will make its own judgment.
The price path
The stock's reaction was large but uneven. Shares closed Friday at $56.84. After the 7 a.m. release, they touched about $93 in premarket trading before falling back to open near $73. By early afternoon they were at about $77.52, up about 36%, against a gain of about 2.4% for the SPDR S&P Biotech ETF. The move added roughly $800 million to Disc's market value.
Even after the jump, the stock sits about 22% below its 52-week high of $99.50. It is about 8% above its close of $71.65 on Feb. 12. The next day, when the FDA's rejection was announced, the shares fell about 22%.
What remains open
Disc reserved detailed results for a future medical meeting. The release does not give patients' baseline time in light, which determines how meaningful 12.2 extra hours a month is in practice, or how many patients dropped out because of side effects. One approved therapy, Scenesse, already treats the disease. Disc reported about $791 million of cash at the end of 2025.
Market implications
One reading is that the drug has been substantially de-risked. Every endpoint hit, the trial is built around the agency's stated concern and the safety profile was clean at the most severe grades.
A second reading is that the market is right to hold back. The FDA has already said no once, the decision is months away, half of treated patients reported dizziness, and the stock's fade from $93 suggests investors want the full data before paying for approval.
What to watch
The full data set at a medical meeting; the refiling; whether the FDA accepts it and sets an action date; and whether the shares hold their gain relative to biotech indexes over the coming sessions. A detailed data set showing low discontinuation rates would strengthen the first reading.