FDA rejects Disc Medicine's bitopertin over surrogate-endpoint concerns
The FDA declined Disc Medicine’s bitopertin for erythropoietic protoporphyria, citing that the phase 2 trials used a surrogate endpoint (a ~40% drop in PPIX) whose link to meaningful clinical benefit—sun tolerance—remains unproven. The company plans to press on with the APOLLO phase 3 trial, which uses sun-exposure outcomes, while the broader regulatory environment and the CNPV priority voucher program continue to draw scrutiny.