Characterisation of exposure versus response of edoxaban in patients undergoing total hip replacement surgery

Edoxaban is an oral direct factor Xa inhibitor approved for the prevention of venous thromboembolism (VTE) in Japan. The objectives of this analysis were to characterise the population pharmacokinetics (PK) of edoxaban and the relationships between edoxaban exposure and clinical outcomes in a phase IIb study of surgical patients following total hip replacement (THR). A total of 1,795 subjects from a phase IIb study, 10 phase I studies, and three phase IIa studies were included in the PK analysis. The exposure-response analysis included data from surgical patients assigned to edoxaban in the phase IIb study. Edoxaban disposition in healthy and post-surgical patients was well-described with a linear, two-compartment model. Creatinine clearance was significantly correlated with edoxaban clearance and the rate of oral absorption was affected by surgery. The probability of a post-operative VTE was significantly correlated with steady-state metrics of edoxaban exposure estimated for each subject by Bayesian post-hoc methods with age and gender being the significant and expected covariates. The incidence of bleeding was low in these studies and hence no exposure-response relationship could be identified. These analyses suggest that edoxaban has a predictable anticoagulant effect in this patient population leading to dose-proportional reduction in incidence of VTE with low incidence of bleeding.