The efficacy of the entire-vial dosing of emicizumab: Real-world evidence on plasma concentrations, bleeds, and drug waste

Background: Prophylaxis with emicizumab provides effective bleeding protection in persons with hemophilia A (PwHA) but pressures healthcare budgets. The body weight–adjusted dosing at 7-, 14-, or 28-day intervals, according to the label, often mismatches the vial content. Entire-vial dosing resulted in therapeutic concentrations according to pharmacokinetic simulations and was introduced to avoid waste. Objectives: The objective of this study was to evaluate the efficacy of entire-vial dosing of emicizumab by investigating real-world evidence of plasma concentrations, bleeds, and drug waste. Methods: This is a single-center, observational study with PwHA receiving emicizumab in mg/kg doses according to label but dosing interval extrapolated to the nearest vial size. Patient characteristics and bleeds were compared 1 year before starting emicizumab and during emicizumab until January 2022. Concentrations were assessed at weeks 4, 12, and annually. The mean (95% CI) annualized bleed rates were compared by using negative binomial regression. Drug waste between label-based dosing and entire-vial dosing was compared. Results: A total of 112 individuals (94% severe phenotype and 9% positive FVIII inhibitors) were followed for a median of 56 weeks (interquartile range [IQR] 52-68) before and 51 weeks (IQR 29-75) after starting emicizumab. The median emicizumab dose was 5.9 (IQR 5.5-6.2) mg/kg/4 wk with median concentrations of 63 (IQR 51-80) μg/mL. The annualized bleed rate of treated bleeds before emicizumab was 3.6 (95% CI 2.9-4.4) and was 0.8 (95% CI 0.6-1.1) during emicizumab (P < .001). Drug waste was reduced by 9%. Conclusion: The entire-vial dosing of emicizumab is an attractive treatment option for PwHA leading to therapeutic plasma concentrations, good bleeding control, and drug waste avoidance.