Disc’s Phase 3 APOLLO study delivered positive top-line results for bitopertin in erythropoietic protoporphyria (EPP), clearing key efficacy doubts that had contributed to earlier FDA concerns. The company said the glycine transporter 1 (GlyT1) inhibitor met both co-primary endpoints in the randomized trial. Compared with placebo, bitopertin reduced whole-blood PPIX levels by 41.4% (p<0.0001) and increased average monthly time in light without pain by 12.2 hours at month six (p=0.001). The readout helped Disc’s shares surge nearly 40% on the announcement. Disc’s result matters because EPP patients experience debilitating phototoxicity, and endpoint selection—biomarker dynamics and clinically meaningful time in pain-free light exposure—directly affects regulatory defensibility. With the study meeting its co-primary targets, Disc now has a clearer path to re-engage regulators with a more complete efficacy package. The broader lesson for the sector is that regulatory objections can turn into trial design refinements, with subsequent Phase 3 data providing the evidence regulators were signaling they needed earlier.