A Study to Evaluate the Pharmacodynamics and Safety of ARCT-810 in Participants With OTCD

Inclusion Criteria

• Willingness and ability to comply with all the protocol requirements, complete all study visits and sign informed consent.
• Males and Females aged ≥12 years, at Screening.
• Documented clinical diagnosis of OTC deficiency.
• History of symptomatic hyperammonemia or elevated plasma ammonia or glutamine with clinical stability for at least 1 month prior to Screening.
• Medically managed for OTC deficiency and receiving a stable protein-restricted diet, dietary supplements, and/or ammonia scavenger regimen (if applicable) for at least 28 days.
• Good general health with no clinically significant abnormal findings that would interfere with study procedures (including plasma ammonia within participant's historical range).
• Must be willing to adhere to contraception guidelines.

Exclusion Criteria

• Uncontrolled hypertension.
• Symptoms of infection for at least 7 days prior to dosing.
• Malignancy within 5 years, except for basal or squamous cell carcinoma of the skin or carcinoma in situ of the cervix that has been successfully treated.
• History of any OTC gene therapy, or history of liver-derived stem cell therapy in the past 2 years.
• History of any organ transplant.
• History of severe allergic reaction to a liposomal or PEG-containing product.
• History of congenital or acquired cardiac disorders.
• Abuse of medications, illicit drugs or alcohol.
• Blood donation of 50 to 499 mL within 30 days of screening or of >499 mL within 60 days of screening.
• Clinically significant laboratory abnormalities on screening labs including INR >1.5, eGFR\< 60 mL/min/1.73m2 or positive test results for HIV, HBV, or HCV.
• Inadequately controlled diabetes.
• Clinically significant anemia.
• Changes in maintenance therapies for OTC deficiency with 28 days prior to dosing.
• Medical history requiring continuous or intermittent systemic corticosteroid administration.
• Receipt of inhibitors of urea synthesis or drugs that significantly affect renal clearance.
• Recent treatment with another investigational drug, biological agent, or device.
• Treatment with any oligonucleotide (siRNA or mRNA) within 6 months prior to screening. COVID-19 vaccines are not exclusionary.
• Involved in study conduct or an immediate family member of an individual involved in the study.
• Participated in another dosing cohort of the study.
• Any other conditions, in the opinion of the investigator, that would interfere with participation.