This is a Phase 2, multi-center, double-blind, placebo-controlled, parallel group study of bitopertin to evaluate the safety, tolerability, efficacy, and PPIX concentration change in participants with EPP. Participants may roll over to an open label extension portion after completing the double-blind treatment period.

Inclusion Criteria:

1. Aged 18 years or older at the time of signing the informed consent form (ICF).
2. Diagnosis of EPP, based on medical history by ferrochelatase ( FECH) genotyping or by biochemical porphyrin analysis.
3. Body weight ≥50 kg.
4. Washout of at least 2 months prior to Screening of afamelanotide and dersimelagon, if applicable.
5. Aspartate aminotransferase (AST) and alanine transaminase (ALT) <2× upper limit of normal (ULN) and total bilirubin <ULN (unless documented Gilbert syndrome) at Screening. Albumin >lower limit of normal (LLN).

Exclusion Criteria:

Medical History:

1. Major surgery within 8 weeks before Screening or incomplete recovery from any previous surgery.

2. Other than EPP, an inherited or acquired red cell disease associated with anemia.

3. A history or known allergic reaction to any investigational product excipients or history of anaphylaxis to any food or drug.

4. History of liver transplantation.

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

6. Human immunodeficiency virus (HIV), active Hepatitis B, or C.

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

8. Condition or concomitant medication that would confound the ability to interpret clinical, clinical laboratory, or participant diary data, including a major psychiatric condition that has had an exacerbation or required hospitalization in the last 6 months.

   Treatment History:

9. Concurrent or planned treatment with afamelanotide or dersimelagon during the study period.

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

11. New treatment for anemia, including initiation of iron supplementation, in the 2 months prior to Screening.

12. Current or planned use of any drugs or herbal remedies known to be strong inhibitors or inducers of CYP3A4 enzymes for 28 days prior to the first dose and throughout the study.

    Laboratory Exclusions:

13. Hemoglobin <10 g/dL at Screening.