Population Pharmacokinetic/Pharmacodynamic Analyses of Avatrombopag in Patients With Chronic Liver Disease and Optimal Dose Adjustment Guide With Concomitantly Administered CYP3A and CYP2C9 Inhibitors

Avatrombopag, a c‐Mpl agonist, has been developed to provide an alternative therapy to standard platelet transfusion care for the treatment of thrombocytopenia. The main objectives of this article were to describe the pharmacokinetics (PK) of avatrombopag, to characterize the pharmacokinetic/pharmacodynamic (PK/PD) relationship between plasma avatrombopag concentrations and platelet count, and to identify potential intrinsic and extrinsic factors affecting PK or PK/PD in patients with chronic liver disease (CLD). Platelet count following avatrombopag administration with and without concomitant medication was further simulated using the final population PK/PD model to explore potential dose adjustments. Avatrombopag PK was described by a 1‐compartment model with combined first‐ and zero‐order absorption and linear elimination. The relationship between the plasma avatrombopag concentrations and platelet count was well described by a 6‐compartment life‐span model with a linear drug effect. The final PK and PK/PD models included statistically significant but not clinically relevant effects of body weight and CLD on apparent volume distribution and East Asian ethnicity, albumin, and thrombopoietin level on the slope parameter in the PK/PD relationship. PK/PD simulations showed comparable elevation in platelet count with and without concomitant cytochrome P450 (CYP) 3A and CYP2C9 inhibitors for the dosing regimens of 40 and 60 mg for 5 days, with predictions of <10% of CLD patients exceeding platelet count >200 × 10 9 /L. Dose adjustment is therefore not necessary with concomitant use of CYP3A and CYP2C9 interacting drugs considering the limited treatment duration (ie, 5 days) and lack of significant safety concerns in CLD patients.