This clinical trial is focused on studying a condition known as Ornithine Transcarbamylase (OTC) deficiency, which is a rare genetic disorder that affects the body’s ability to eliminate ammonia, a waste product. The study is investigating a treatment called Avalotcagene ontaparvovec, also known by its code name DTX301. This treatment involves a type of gene therapy using a virus to deliver a healthy copy of the OTC gene to the patient’s cells. The virus used in this therapy is a recombinant adeno-associated viral vector, which is designed to be safe and effective in transferring the gene.

The purpose of the study is to evaluate the long-term safety of this gene therapy in adults who have late-onset OTC deficiency. Participants in the study will receive a single dose of the treatment through an intravenous infusion, which means it will be administered directly into the bloodstream. The study will follow participants over an extended period to monitor their health and any changes in their condition. This will help researchers understand how the treatment affects the body over time and whether it can safely reduce the symptoms of OTC deficiency.

Throughout the study, researchers will collect information on any side effects experienced by participants and how these relate to the treatment. They will also measure changes in the levels of ammonia in the blood and the body’s ability to produce urea, a process known as ureagenesis. These measurements will help determine the effectiveness of the treatment in managing OTC deficiency. The study aims to provide valuable insights into the potential of gene therapy as a long-term solution for individuals with this condition.