GATEWAY: A Phase 2a Study of PORT-77 in Adults With Erythropoietic Protoporphyria

Major Inclusion Criteria: * BMI ≥18.0 and ≤35.0 kg/m2 and weight ≥50 kg * Known diagnosis of EPP and is currently symptomatic even if receiving treatment for EPP, including afamelanotide. * Willing and able to avoid exposure to sunlight when outside of the clinical research site. * Willing and able to follow protocol-specified contraception guidance. * Able to read and understand English * Able to understand the study procedures as described in the ICF and is willing and able to comply with the study requirements. Major Exclusion Criteria: * Is mentally or legally incapacitated * History or presence of any illness or clinically significant medical or psychiatric condition or disease that, in the opinion of the PI or designee, might confound the results of the study or pose an additional risk to the participant by their participation in the study. * History of gastrointestinal condition, including surgeries, which may affect absorption after oral administration. * History of cancer, with the exception of cutaneous non-melanoma skin cancer (basal or squamous cell carcinoma). * Participation in another clinical study within 28 days or within 5 half-lives (if known), prior to screening * Unable to refrain from or anticipates the use of medications/supplements known to confound PORT-77 beginning 28 days (or 5 half-lives, whichever is longer) prior to the first dose of study drug and throughout the study. * Estimated glomerular filtration rate \<80 mL/min/1.73 m2 using the CKD-EPI equation at screening * Hepatic impairment, with alanine aminotransferase, aspartate aminotransferase, or total bilirubin \>1.5 x ULN at screening * Female participant with a positive pregnancy test at screening or who is breastfeeding.