OC 30.4 - Emicizumab real world experience using the entire-vial based dosing regimen in for patients with haemophilia A: AN UPDATE

Background: Emicizumab is a subcutaneous FVIII mimetic that effectively reduces bleeds in patients with haemophilia A. The registered maintenance dose is based on body-weight: 6 mg/kg/4 weeks (with varying intervals). The dose per administration, given an individual weight difference, often does not match vial content leading to medication spillage. The long elimination half-life of emicizumab enables use of entire vials by varying the dosing interval (7 to 28 days). Entire-vial based dosing was introduced for patients receiving emicizumab.

Aims: To report real-world experience of the entire-vial based dosing regimen of emicizumab in patients with haemophilia A by investigating emicizumab concentrations.

Methods: Monocenter, observational cohort study. All haemophilia A patient receiving emicizumab as maintenance therapy for >2 months with plasma emicizumab concentrations available, were included. Loading doses were administered according to label. Maintenance treatment was dosed 6mg/kg/4 weeks using entire vial regimen by varying interval 7 to 28 days. Plasma emicizumab concentrations were measured using a fully validated mass spectrometry-method.

Results: A total of 89 patients were included see table 1. Their median age at start of emicizumab was 18.5 years (P25-P75 (IQR): 8.8 – 53.1), weight was 66.0 kg (IQR 31.5- 85.7). Patients received a median of 115 days (IQR 103-370) emicizumab maintenance treatment. The median emicizumab dose of 5.9 mg/kg/4 weeks administered in 7 – 28 days intervals, with 31% of patients using intervals >12 days. Median plasma concentration of emicizumab was 61.7 µg/ml (IQR 49.0 – 79.9) with no differences observed between adults and children, see figure 1. A total of 74 patients (83%) demonstrated emicizumab concentration ≥ 40 µg/ml during maintenance therapy using entire vials based dose regimen.

Conclusion(s): Dosing emicizumab using entire vials with varying intervals to achieve 6mg/kg/4weeks, resulted in effective concentrations of emicizumab in both children and adults. This dosing strategy can be applied to avoid medication spillage.