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

Multicenter, Safety and Efficacy, Open-Label Extension Study of ACTIMMUNE® (Interferon γ-1b) in Children and Young Adults With Friedreich's Ataxia

The purpose of this phase 3 multi-center, open-label extension study is to evaluate the long-term safety of ACTIMMUNE® (interferon-γ 1b) in participants with Friedreich's Ataxia.

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.

Study with completed results acquired from Horizon in 2024.

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.