A Study of Safety of Weekly Subcutaneous Pegzilarginase in Subjects With Arginase 1 Deficiency

Inclusion Criteria: 1. Prior enrollment in pegzilarginase clinical studies, with completion of treatment or continued dosing as of the study termination date 2. Written informed consent by subject/parent/legal guardian, which includes compliance with the requirements and restrictions listed in the informed consent form and in this protocol 3. Negative pregnancy test within 7 days prior to dosing in childbearing subjects if they are sexually active 4. If the subject (male or female) is engaging in sexual activity that could lead to pregnancy, must be surgically sterile, post-menopausal (female), or must agree to use a highly effective method of birth control during the study and for a minimum of 30 days after the last study drug administration. Highly effective methods of contraception include combined (estrogen and progestogen-containing) hormonal contraception associated with inhibition of ovulation, progesterone-only hormonal contraception associated with inhibition of ovulation, intrauterine device, or intrauterine hormone-releasing system Exclusion Criteria: 1. Subjects with acute or ongoing hyperammonemia within 6 weeks of the first dose 2. Subjects with medical conditions or underlying issues that, in the opinion of the Investigator, would preclude participation in the study