Safety, Tolerability and Efficacy of ACTIMMUNE® Dose Escalation in Friedreich's Ataxia Study

Participants who complete 26 weeks of blinded treatment in HZNP-ACT-301 (NCT02415127), will
be eligible to enter this 6-month study. All participants will receive ACTIMMUNE® 3 times a
week (TIW) for 26 weeks. In order to maintain the study blind in HZNP-ACT-301 (NCT02415127),
all participants in this open-label extension study will undergo ACTIMMUNE® titration,
regardless if they received ACTIMMUNE® or placebo in HZNP-ACT-301 (NCT02415127). The Week 26
Visit from HZNP-ACT-301 (NCT02415127) will serve as the Baseline Visit (Day 1) for this
study. During the treatment period, additional clinic visits are scheduled at Weeks 4, 13,
and 26; in between clinic visits, participants (and/or caregivers) will be monitored via
emails/phone calls on a weekly basis until participants reach their maximum tolerated dose,
and on a monthly basis thereafter.

Inclusion Criteria:

- Written informed consent and child assent, if applicable.

- Completed 26 weeks of blinded treatment in Study HZNP-ACT-301 (NCT02415127).

- If female, the subject is not pregnant or lactating or intending to become pregnant
during the study, or within 30 days after the last dose of study drug. Female subjects
of child-bearing potential must have a negative urine pregnancy test result at
Baseline/Day 1 (Week 26 of Study HZNP-ACT-301 [NCT02415127]), and agree to use a
reliable method of contraception throughout the study and for 30 days after the last
dose of study drug.

Exclusion Criteria:

- Subjects will be ineligible if, in the opinion of the Investigator, they are unlikely
to comply with the study protocol or have a concomitant disease or condition that
could interfere with the conduct of the study or potentially put the subject at
unacceptable risk.

NOTE: Additional inclusion/exclusion criteria may apply.