A pill that could let people with rare sunlight disorder step outside without pain

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Aged 12 years or older. * Clinical history of EPP, XLP, or EPP2 supported by genetic confirmation or historical laboratory test results * History of consistent, non-painful prodrome within approximately 45 minutes of sunlight exposure and prior to phototoxic attacks * Demonstrates ≥85% compliance with daily symptom diary during run-in period. * Body weight or BMI at Screening as follows: 1. For participants aged 12 to \<18 years: body weight ≥32 kg 2. For participants aged ≥18 years: BMI ≥18.5 kg/m2 * AST and ALT \<3 × ULN and total bilirubin \<2 × ULN (unless documented Gilbert syndrome) at Screening * Willing and able to provide informed consent and/or assent for the study. * Willing and able to comply with study visits, study procedures, and contraception guidance * Intends to remain in the same approximate geographic latitude for the duration of the placebo-controlled period, with no more than 14 days spent outside this region. Exclusion Criteria: * Diagnosis of another porphyria or another photodermatosis that may confound the evaluation of PORT-77 * Any evidence of clinically significant organ dysfunction or any clinically significant deviation from normal in the clinical or laboratory assessments * Major surgery within 8 weeks before Screening, incomplete recovery from any previous surgery, or major surgery planned to occur during the study * History of, or anticipated need for, liver transplantation or history of bone marrow transplantation * Active infection with hepatitis B or C * Unable to swallow tablets or has a disease that significantly affects gastrointestinal function * Any other disease, condition, or circumstance that, at the discretion of the Investigator or Sponsor, would interfere with the evaluation of PORT-77 or study participation, or would make study participation not in the best interest of the participant * History of drug or alcohol abuse within the last 12 months, or current or planned use of prohibited or illegal substances * Has taken any medication, vitamin, or supplement that alters sensitivity to light exposure (eg, afamelanotide, melanotan, beta carotene, dersimelagon) within 90 days of Day 1; or has taken bitopertin within 120 days of Day 1; or has taken iron within 30 days of Day 1 * Drugs or supplements that may impact or be impacted by PORT-77 * Concurrent or anticipated participation in an interventional clinical trial during the study period. * Received another investigational therapy within 5 half-lives, if the half-life is known, or within 30 days, if the half-life is unknown, prior to Day 1. * Known hypersensitivity to PORT-77 or excipients * Female who has a positive pregnancy test at Screening or Day 1 or is breastfeeding