HELIOS: Open-Label, Long-Term Extension Study to Investigate the Safety, Tolerability, and Efficacy of DISC-1459 (Bitopertin) in Participants With EPP or XLP

Inclusion Criteria: * Participants with diagnosis of EPP who are participating (or who have participated) in a prior Disc Medicine bitopertin study and who have completed the randomized treatment phase and End-of-Study visit * Aged ≥12 years upon study consent * Body weight ≥32 kg for participants \<18 years of age and BMI ≥18.5 kg/m2 for adult participants * Willing to practice highly effective methods of birth control (both males who have partners of childbearing potential and females of childbearing potential during the study, while taking study drug, and for at least 30 days after the last dose of study drug. * Negative urine or serum pregnancy test (females of childbearing potential). * Able to understand the study aims, procedures, and requirements, and provide written informed consent (and assent if necessary). * Able to comply with all study procedures. Exclusion Criteria: * Participants who have an ongoing SAE from a clinical study that is assessed by the investigator as related to bitopertin * Other medical or psychiatric condition or laboratory finding not specifically noted above that, in the judgement of the Investigator or Sponsor, would put the participant at unacceptable risk or otherwise preclude participation in the study * 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…