Study for Adolescents and Adults With Ornithine Transcarbamylase Deficiency to Evaluate Safety and Tolerability of ARCT-810

Key Inclusion Criteria: 1. Adequate cognitive ability to understand study requirements and give informed consent 2. Males and females aged 12 to 65 years inclusive, at Screening 3. Documented diagnosis of OTC deficiency 4. Clinical stability (no clinical symptoms of hyperammonemia within 1 month, no hospitalizations for metabolic decompensation within 3 months, ≤ 2 hospitalizations within 1 year) 5. Stable protein-restricted diet, dietary supplements, and ammonia scavenger regimen (if applicable) for at least 28 days. 6. BMI = 18.0 - 32.0 kg/m2, inclusive for adults, and \>5th percentile for adolescents ≥12 to 17 years 7. Must be willing to adhere to contraception guidelines Key Exclusion Criteria: 1. History of any OTC gene therapy, or history of liver-derived stem cell therapy in the past 3 years 2. History of other medical conditions that may make the participant unsuitable for inclusion or could interfere with study participation (e.g., uncontrolled hypertension or diabetes, malignancy, HIV, hepatitis B or C) 3. History of severe allergic reaction to liposomal or PEG-containing products 4. Abuse of illicit drugs, medications or alcohol 5. Clinically significant laboratory abnormalities on screening labs