Pharmacokinetics of idarucizumab and its target dabigatran in patients requiring urgent reversal of the anticoagulant effect of dabigatran

BACKGROUND: Idarucizumab is a monoclonal antibody fragment that reverses dabigatran anticoagulation. Pharmacokinetics (PK) of idarucizumab have been described in healthy, elderly, or renally impaired (RI) volunteers, but PK data in patients are lacking. OBJECTIVES: This analysis describes the PK of idarucizumab and its target dabigatran in bleeding/surgical patients. PATIENTS AND METHODS: Results from the Reversal Effects of Idarucizumab on Active Dabigatran study, a prospective, multicenter, single‐arm study demonstrated the reversal of dabigatran anticoagulation by idarucizumab in patients with uncontrollable bleeding (group A) or who needed urgent surgery (group B). Idarucizumab and unbound dabigatran concentrations, immunogenicity, and pharmacodynamics were assessed. RESULTS: Total and unbound dabigatran levels at baseline were 165 ng/mL vs 110 ng/mL and 103 ng/mL vs 69.5 ng/mL in group A and B patients, respectively. Maximum plasma concentrations and area under the curves (AUC (0‐24)) of idarucizumab in group A vs B, respectively, were 24 900 nmol/L vs 25 000 nmol/L and 76 600 nmol/h/L vs 68 000 nmol/h/L. Idarucizumab AUC(0–24) increased by 38% in mild, 90% in moderate, and 146% in severe RI patients vs normal renal function. Hepatic impairment or geographical region had no relevant effect on idarucizumab PK. Idarucizumab immediately decreased unbound dabigatran concentration (<20 ng/mL). A linear correlation was observed between unbound dabigatran and diluted thrombin time and ecarin clotting time. Antidrug antibody titers were low (1‐64 at day 30; 0‐16 at day 90) and had no impact on idarucizumab PK and pharmacodynamics. CONCLUSION: Idarucizumab PK in target patients was consistent with phase I data. Patient characteristics had no impact on PK, whereas RI increased the exposure of idarucizumab and dabigatran. Trial registration number: ClinicalTrials.gov NCT02104947.