Population pharmacokinetics of recombinant coagulation factor VIII-SingleChain in patients with severe hemophilia A

Background: Single-chain recombinant coagulation factor VIII (rVIII-SingleChain) is a unique recombinant coagulation factor VIII molecule. Objectives: To: (i) characterize the population pharmacokinetics (PK) of rVIII-SingleChain in patients with severe hemophilia A; (ii) identify correlates of variability in rVIII-SingleChain PK; and (iii) simulate various dosing scenarios of rVIII-SingleChain. Patients/ Methods: A population PK model was developed, based on FVIII activity levels of 130 patients with severe hemophilia A (n = 91 for >= 12-65 years; n = 39 for < 12 years) who had participated in a single-dose PK investigation with rVIII-SingleChain 50 IU kg(-1). PK sampling was performed for up to 96 h. Results: A two-compartment population PK model with first-order elimination adequately described FVIII activity. Body weight and predose level of von Willebrand factor were significant covariates on clearance, and body weight was a significant covariate on the central distribution volume. Simulations using the model with various dosing scenarios estimated that > 85% and > 93% of patients were predicted to maintain FVIII activity level above 1 IU dL(-1), at all times with three-times-weekly dosing (given on days 0, 2, and 4.5) at the lowest (20 IU kg(-1)) and highest (50 IU kg(-1)) doses, respectively. For twice weekly dosing (days 0 and 3.5) of 50 IU kg(-1) rVIII-SingleChain, 62-80% of patients across all ages were predicted to maintain a FVIII activity level above 1 IU dL(-1) at day 7. Conclusions: The population PK model adequately characterized rVIII-SingleChain PK, and the model can be utilized to simulate FVIII activity-time profiles for various dosing scenarios.