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

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 asigned IRB/IEC-approved ICF.

Key Exclusion Criteria:

1. Neonatal diagnosis of severe to profound Hypoxic Ischemic Encephalopathy due tobirth 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 toor during the duration of this trial would require the participant to be withdrawnfrom this study

7. Any condition, that in the opinion of the Investigator, would compromise the safetyof 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 theopinion of the Investigator may increase the participant's risk of developmentaldelays, congenital anomalies, and/or significant medical complications