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

Inclusion Criteria:

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) oraminolevulinic acid synthase 2 (ALAS2) genotyping or by biochemical porphyrinanalysis.

3. Minimum daily Sun Exposure Diary compliance ≥85% on Days -14 through Day -1,inclusive, during screening, and at least 1 successfully completed Sun ExposureChallenge (adults only, as this assessment is optional for adolescents) orhistorical recall of time to prodrome

4. Body weight ≥32 kg (ages 12 to <18 years), body mass index ≥18.5 kg/m2 (ages ≥18years) at screening.

5. Washout of at least 2 months prior to screening of afamelanotide and dersimelagon,if applicable.

6. Aspartate aminotransferase and alanine transaminase <3× upper limit of normal (ULN)and total bilirubin <2× ULN (unless documented Gilbert syndrome) at screening.Albumin >lower limit of normal (LLN).

7. Willing to practice highly effective methods of birth control (both males who havepartners of childbearing potential and females of childbearing potential duringscreening, while taking study drug, and for at least 30 days after the last dose ofstudy drug).

Exclusion Criteria:

1. Major surgery within 8 weeks before screening or incomplete recovery from anyprevious surgery.

2. Other than EPP or XLP, an inherited intrinsic or extrinsic red cell diseaseassociated with anemia.

3. Known hypersensitivity to any component of the study drug.

4. History of liver transplantation or anticipated need for liver transplantation.

5. History of alcohol dependence or excessive alcohol consumption, as assessed by theInvestigator.

6. Active human immunodeficiency virus (HIV), active hepatitis B or C.

7. Other medical or psychiatric condition or laboratory finding not specifically notedabove that, in the judgment of the Investigator or Sponsor, would put theparticipant at unacceptable risk or otherwise preclude the participant fromparticipating in the study.

8. Condition or concomitant medication that would confound the ability to interpretclinical, clinical laboratory, or participant diary data, including a majorpsychiatric condition that has had an exacerbation or required hospitalization inthe last 6 months. Treatment History:

9. Prior exposure to bitopertin.

10. Concurrent or planned treatment with afamelanotide or dersimelagon during the studyperiod.

11. Treatment with opioids for any period >7 days in the 2 months prior to screening oranticipated to require opioid use for >7 days at any point during the study.

12. New treatment for anemia, including initiation of iron supplementation, within 1month of screening.

13. Current or planned use of any drugs or herbal remedies known to be strong ormoderate inhibitors or inducers of cytochrome P450 (CYP)3A4 enzymes for 28 daysprior to the first dose and throughout the study.

14. Current or planned treatment with antipsychotic medication. Laboratory Exclusions:

15. Hemoglobin <10 g/dL at screening. Miscellaneous:

16. Participation in other interventional clinical studies within 30 days prior toscreening.

17. If female, pregnant or breastfeeding.