Study of Bitopertin in Participants With EPP or XLP (APOLLO)

The goal of this clinical trial is to learn if bitopertin works and is safe to treat EPP or XLP in participants 12 years or older. The main questions it aims to answer are: * Whether bitopertin increases pain-free sunlight exposure after 6 months of treatment in participants with EPP or XLP. * How PPIX concentration levels change from before bitopertin treatment to after 6 months of treatment. Researchers will compare bitopertin to a placebo look-alike substance that contains no drug. Participants will complete daily questionnaires and attend study visits…

• : 1. Aged 12 years or older at the time of study consent. 2. Diagnosis of EPP or XLP, based on medical history by ferrochelatase (FECH) or aminolevulinic acid synthase 2 (ALAS2) genotyping or by biochemical porphyrin analysis. 3. Minimum daily Sun Exposure Diary compliance ≥85% on Days -14 through Day -1, inclusive, during screening, and at least 1 successfully completed Sun Exposure Challenge (adults only, as this assessment is optional for adolescents) or historical recall of time to prodrome 4. Body weight ≥32 kg (ages 12 to 7 days at any point during the study. 12. New treatment for anemia, including initiation of iron supplementation, within 1 month of screening. 13. Current or planned use of any drugs or herbal remedies known to be strong or moderate inhibitors or inducers of cytochrome P450 (CYP)3A4 enzymes for 28 days prior to the first dose and throughout the study. 14. Current or planned treatment with antipsychotic medication. Laboratory Exclusions: 15. Hemoglobin

Use the source registry for the full inclusion and exclusion criteria before discussing referral or enrolment.