BAY 81-8973 safety and efficacy for prophylaxis and treatment of bleeds in previously treated children with severe haemophilia A: Results of the LEOPOLD Kids Trial

Introduction: BAY 81-8973, a full-length, unmodified, recombinant factor VIII (FVIII) in development for treatment of haemophilia A, has the same primary amino acid sequence as Bayer's sucrose-formulated recombinant FVIII but is produced with more advanced manufacturing technologies. Aim: To demonstrate safety and efficacy of BAY 81-8973 for prophylaxis and treatment of bleeds in previously treated children. Methods: In this phase III, multicentre, open-label, nonrandomized study, boys aged ≤12 years with severe haemophilia A and ≥50 exposure days (EDs) to FVIII products received prophylaxis with BAY 81-8973 25-50 IU kg^-1 ≥2 times weekly for ≥50 EDs. The efficacy endpoint was annualized number of total bleeds. Adverse events (AEs) and immunogenicity were assessed. Results: Fifty-one patients were treated (age: <6 years, n = 25; 6-<12 years, n = 26) with a 2× per week (43%) or >2× per week (57%) regimen at study start. Median [quartile 1; quartile 3 (Q1; Q3)] annualized number of bleeds for the combined age groups was 1.90 (0; 6.02) for total bleeds, 0 (0; 2.01) for joint bleeds and 0 (0; 0) for spontaneous bleeds. Median (Q1; Q3) annualized number of total bleeds within 48 h of previous prophylaxis infusion was 1.88 (0; 3.97) for children aged <6 years and 0 (0; 1.96) for children aged 6-<12 years. No drug-related serious AEs or inhibitors were reported. Conclusions: Prophylaxis with BAY 81-8973 using individualized prophylaxis regimens of 2× per week, 3× per week and every-other-day infusions was efficacious in prevention and treatment of bleeds in children with severe haemophilia A. Treatment with BAY 81-8973 was well tolerated.