An Open-label Study to Investigate ECUR-506 in Male Babies Less Than 9 Months of Age With Neonatal Onset OTC Deficiency (OTC-HOPE)

Ornithine Transcarbamylase (OTC) deficiency, the most common urea cycle disorder, is an inherited metabolic disorder caused by a genetic defect in a liver enzyme responsible for detoxification of ammonia. Individuals with OTC deficiency can build-up excess levels of ammonia in their blood, potentially resulting in devastating consequences, including cumulative and irreversible neurological damage, coma and death. The severe form of the condition emerges shortly after birth and is more common in boys than girls.

This is a Phase 1/2, open-label, multicenter, safety and dose finding study of ECUR-506 in male babies with neonatal onset OTC deficiency. The primary objective of this study is to evaluate the safety and tolerability of multiple dose levels of ECUR-506 following intravenous (IV) administration of a single dose.

The study drug, ECUR-506, is an investigational gene editing therapy. Gene editing is a way to repair, replace, or introduce new copies of genes that don't work. The study drug contains a working copy of the OTC gene that will be delivered by an IV infusion. It also contains a gene to encode the editing enzyme which is the part of the study drug that can cut DNA so that the OTC gene can be inserted. The study drug was designed to introduce a working copy of the OTC gene and a gene to encode the editing enzyme. A gene cannot enter cells by itself, it needs a delivery mechanism to move the gene into the cells. In this study, a commonly used virus called adeno-associated virus (AAV) is used to enter the cells and deliver the genes.

Eligibility Criteria:
Key Inclusion Criteria:

1. Male sex
2. Gestational age ≥ 37 weeks
3. Age at screening is 24 hours to 7 months\*
4. Weight ≥ 3.5 kg and ≤ 10.0 at screening
5. Has received all age-appropriate vaccinations
6. Genetically confirmed OTCD
7. Severe neonatal OTCD defined by hyperammonemic crisis within first week of life
8. Current or historical biochemical profile consistent with OTCD
9. Participant's parent(s)/LAR must be able to comprehend and be willing to provide a signed IRB/IEC-approved ICF.

Key Exclusion Criteria:

1. Neonatal diagnosis of severe to profound Hypoxic Ischemic Encephalopathy due to birth injury
2. Requiring urgent liver transplant due to liver failure as assessed by the PI.
3. Contiguous gene deletion involving the OTC gene
4. Known or suspected major organ injury/dysfunction/anomalies.
5. Treatment with any other gene therapy or gene editing therapy
6. Co-enrollment in any other clinical study with an investigational product prior to or during the duration of this trial would require the participant to be withdrawn from this study
7. Any condition, that in the opinion of the Investigator, would compromise the safety of the participant or study data
8. Documented vertical transmission of HSV, HIV, or HepA/HepB/HepC
9. Documented in-utero teratogen, substance, and/or alcohol exposure, which in the opinion of the Investigator may increase the participant's risk of developmental delays, congenital anomalies, and/or significant medical complications