Safety and Efficacy of Self Administered Injections of Pegvaliase (>40mg/Day Dose) in Adults With PKU

Pegvaliase dosing will continue without interruption from Parent Study 165-302 (NCT02468570) or Parent Study PAL-003 (NCT00924703). Beginning on Day 1, subjects will receive the same dose and regimen of pegvaliase they were receiving in either 165-302 or PAL-003. A subject who reduces to a dose of 40 mg/day or lower for 32 consecutive weeks will be discontinued from study drug and withdrawn from the study as they will have the option to transition to commercial drug. Dose reductions may be performed if warranted due to AEs or hypophenylalaninemia. Dose increases to up to 60 mg/day may be performed per investigator discretion in consultation with the sponsor's medical monitor. Dosing will continue for approximately 121 weeks.