Long-Term Safety Extension Study of ACTIMMUNE® (Interferon γ-1b) in Children and Young Adults With Friedreich's Ataxia

This is a multi-center, open-label, long-term safety extension study of ACTIMMUNE® in the
treatment of FA in children and young adults. Participants who complete 26 weeks of treatment
and the Week 28 Follow-Up Visit in HZNP-ACT-302 (NCT02593773) will be eligible to enter this
long-term safety extension protocol. The Day 1 Visit of this study (HZNP-ACT-303) occurs on
the same day as the Week 28 Follow-Up Visit for HZNP-ACT-302 (NCT02593773). Participants will
be required to return for clinic visits at least every 6 months. The treatment duration is
open-ended, and treatment will continue until ACTIMMUNE® is commercially available for the
treatment of FA in the United States or until the Sponsor decides not to continue development
for the treatment of FA.

Inclusion Criteria:

- Written informed consent and child assent, if applicable.

- Completed 26 weeks of treatment and the Week 28 Follow-Up visit in Study HZNP-ACT-302
(NCT02593773).

- 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 Week 26
of Study HZNP-ACT-302 (NCT02593773) 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:

- If in the opinion of the Investigator, patients have a concomitant disease or
condition that could interfere with the conduct of the study or potentially put the
subject at unacceptable risk, the subject will be excluded from the study.