BAY 81‐8973 Demonstrates Long‐Term Safety and Efficacy in Children With Severe Haemophilia A: Results From the LEOPOLD Kids Extension Study

OBJECTIVES: To report the long-term safety and efficacy of BAY 81-8973 in the LEOPOLD Kids extension phase. METHODS: Patients received BAY 81-8973 (25-50 IU/kg) at least twice weekly. The primary endpoint was safety, assessed in all patients who entered the extension phase (n = 82). Efficacy endpoints were assessed in patients without high-titre inhibitors/immune tolerance induction (n = 67). RESULTS: Children (n = 82) received BAY 81-8973 for a median of 3.1 years per patient and a median of 405 exposure days per patient. Long-term BAY 81-8973 treatment was well tolerated, with no cases of de novo inhibitor development in the extension phase. Annualised bleeding rates (ABRs) within 48 h of prophylaxis were low for all bleeds (median [IQR], 0.7 [0-1.9]; mean, 1.4 [SD, 2.1]) and for joint bleeds (median [IQR], 0 [0-0.7]; mean, 0.5 [SD, 1.1]) (n = 67). Twenty-one of 67 patients (31.3%) had zero bleeds within 48 h of prophylaxis; the treatment response was 'good'/'excellent' in 87.9% of bleeds, and most bleeds resolved with ≤ 2 BAY 81-8973 infusions (83.5%). CONCLUSION: Long-term BAY 81-8973 treatment is well tolerated and maintains low ABRs for all bleeds and joint bleeds in children with severe haemophilia A. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT01311648.