Gene Therapy Program

Gene Therapy for Ornithine Transcarbamylase (OTC) Deficiency

Ornithine transcarbamylase (OTC) deficiency is genetic condition caused by a mutation in the OTC gene. Ordinarily, the OTC gene provides instructions to make the ornithine transcarbamylase enzyme, responsible for detoxification of ammonia, which forms when proteins are broken down in the body. With an OTC deficiency, ammonia builds up in the bloodstream and can become toxic at high levels, potentially resulting in neurological deficits and eventual liver damage.

The most common form of OTC deficiency, occurring in both males and females, is late-onset, which although considered milder than neonatel-onset OTC deficiency, is still considered a serious condition. Currently, the only curative treatment is liver transplantation.

How gene therapy for OTC deficiency works

Gene therapy is designed to provide a healthy copy of the OTC gene. In the laboratory, a normal OTC gene is packaged into a modified adeno-associated virus (AAV) that targets liver cells. This virus, which has acts as a delivery vehicle, or vector, is introduced into a patient's body with a single intravenous infusion. The vector with the functional copy of the OTC gene then travels to the liver and enters the liver cells, enabling the body to make the ornithine transcarbamylase enzyme.

OTC deficiency gene therapy clinical trial

Safety and Dose-Finding Study of DTX301 (scAAV8OTC) in Adults With Late-Onset OTC Deficiency (CAPtivate)
Boston Children’s Hospital

Started: Jan. 2017

Wen-Hann Tan, MD, principal investigator
Contact: Farah Ridore, clinical research specialist, at 617-919-6897 or

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