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

Inclusion criteria:

- Must be enrolled in PAL-003 or 165-302 Part 4 at the time of screening for 165-304 and
most recently receiving pegvaliase at a dose > 40 mg/day

- Has identified a competent person or persons ≥ 18 years of age who can observe the
subject during study drug administration and for a minimum of 1 hour following
administration in situations required per protocol

- For females with childbearing potential, must have negative pregnancy test at
screening and be willing to have additional pregnancy tests during the study.

- If sexually active and not planning to become pregnant (self or partner), must be
willing to use 2 acceptable methods of contraception while participating in the study
and for 4 weeks after the study.

Exclusion criteria:

- Use of any investigational product (except pegvaliase) or investigational medical
device within 30 days prior to screening or requirement for any investigational agent
prior to completion of all scheduled study assessments.

- Use of any medication (except pegvaliase) intended to treat PKU, including the use of
large neutral amino acids, within 2 days prior to the administration of pegvaliase
(Day 1).

- Use or planned use of any injectable drugs containing PEG (other than pegvaliase),
including medroxyprogesterone injection, within 3 months prior to screening and during
study participation.

- Current participation in the Kuvan® registry study (PKU Demographics, Outcomes and
Safety [PKUDOS])

- A history of organ transplantation or on chronic immunosuppressive therapy