Abstract Number: PB0915
Meeting: ISTH 2020 Congress
Theme: Hemophilia and Rare Bleeding Disorders » Hemophilia - Clinical
Background: Emicizumab is a bispecific monoclonal antibody which mimics the function of factor VIIIa. It is licensed for patients of any age with haemophilia A with and without inhibitors. The HAVEN trial data has shown that at steady state (1.5mg/kg/week) emicizumab concentration is 40-60ug/ml. In real world paediatric care the actual dose may vary due to vial sizes and inter-current growth between prescriptions.
Aims: Does the timing since last emicizumab dose affect emicizumab concentration?
Does real world variation in emicizumab dose correlate with emicizumab concentration?
Methods: All patients in a single paediatric comprehensive care center on an equivalent dose of 1.5mg/kg/week of emicizumab were reviewed. Emicizumab concentrations were analyzed on a CS2000i (Sysmex) using a modified one stage clotting assay comprising an Emicizumab specific calibrator and controls (R2 diagnostics, Enzyme Research Laboratories), Actin FS APTT reagent and Factor VIII deplete plasma (Siemens) in accordance with best practice guidelines.
Results: Twenty-one patients met the criteria, with a mean age 7.3 years (range 11 months – 15.6 years) at time of starting emicizumab and emicizumab for a mean 22 months (range 3 months – 41 months).
The time since last dose and emicizumab concentration was 6 and 8 days for weekly and fortnightly dosing respectively. Although there is a downward trend the emicizumab concentration remains within the expected range (figure 1). The mean actual emicizumab dose was 1.45mg/kg/week (range 1.23 – 1.65mg/kg/week). The mean emicizumab concentration was 51.8ug/ml (range 12.8 – 88.0ug/ml) (figure 2).
There were no bleeding episodes that required factor replacement.
Conclusions: Once in steady state, timing of venepuncture and slight variation in dosage do not significantly affect emicizumab concentration.
There was no correlation/linearity between emicizumab dose and concentration. This raises the question of whether emicizumab dosing should be based on concentrations as well as patient weight, and if so, what target is optimal.
[Figure 1. Emicizumab concentration compared to time since last emicizumab dose]
[Figure 2 Emicizumab concentration compared to actual emicizumab dose]
To cite this abstract in AMA style:
Gosrani D, Burgess C, Alaoye F, Taylor A, Sibson K, Badle S, Barrie A, Efford J, Spires J, Mathias M, Liesner R. Emicizumab Concentration in Children: A Single Centre Real World Experience [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/emicizumab-concentration-in-children-a-single-centre-real-world-experience/. Accessed September 29, 2023.« Back to ISTH 2020 Congress
ISTH Congress Abstracts - https://abstracts.isth.org/abstract/emicizumab-concentration-in-children-a-single-centre-real-world-experience/