Patients: 25 previously treated children with severe or moderately severe hemophilia B. Children were ≤12 years old, had an FIX activity level of ≤2%, had a history of ≥ 50 exposure days to other FIX products, and weighed ≥10 kg.
Study design: International, multicenter, open-label, non-controlled, single-arm trial designed following EMA guidelines. Patients were stratiﬁed into two age groups: 0–6 years and 7–12 years. The trial consisted of a main phase of 52 weeks, and an extension phase, which is still ongoing. All patients received a ﬁxed dose of 40 IU/kg of Rebinyn® intravenously once weekly for prophylaxis. A pharmacokinetic (PK) assessment was conducted after the first dose of Rebinyn®, with the last PK sample collected 1 week after that dose and just prior to administration of the second dose. Breakthrough bleeds were treated with a single dose of 40 IU/kg of Rebinyn® (mild-to-moderate bleeds) or 80 IU/kg of Rebinyn® (severe bleeds).
Primary endpoint: Immunogenicity of Rebinyn® as measured by the occurrence of FIX inhibitors (≥0.6 BU) over at least 50 exposure days.
Secondary endpoint: Efficacy of Rebinyn® in long-term prophylaxis as assessed by the estimated number of bleeds per year, success in treating breakthrough bleeds, and safety other than immunogenicity. FIX activity was also a secondary endpoint, measured after the first single-dose exposure and again at steady state.