Disc Medicine said its oral drug bitopertin met all primary and secondary goals in a Phase 3 trial for erythropoietic porphyria, a rare disease that causes painful reactions to bright light. The company's shares jumped more than 35% on the news. Disc now plans to resubmit an approval application to the FDA by the end of the year, with a possible launch in 2027.
The FDA rejected an accelerated approval request in February, saying the evidence did not clearly link reductions in the toxic substance PPIX to better sunlight tolerance. However, the agency's complete response letter left the door open for traditional approval if a Phase 3 trial succeeded. Since then, FDA leadership has shifted toward a more flexible stance on rare disease medicines, which could work in Disc's favor.
In the trial, bitopertin lowered PPIX by about 46% after six months, compared with just over 4% for placebo, and increased pain-free time in light by 12.2 hours relative to placebo. The drug was well-tolerated, with dizziness as the most common side effect. Analysts called the data compelling and strongly supportive of full approval, with one projecting a $1 billion to $2 billion market opportunity.