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.
