Population Pharmacokinetics and the Pharmacokinetic/Pharmacodynamic Relationship of Riociguat in Patients with Pulmonary Arterial Hypertension or Chronic Thromboembolic Pulmonary Hypertension

This analysis aimed to characterize the pharmacokinetics (PK) and PK/pharmacodynamic (PK/PD) relationship of riociguat and its metabolite M1 in patients with chronic thromboembolic pulmonary hypertension (CTEPH) or pulmonary arterial hypertension (PAH). Blood samples were collected in two phase 3 studies—PATENT‐1 (Pulmonary Arterial Hypertension Soluble Guanylate Cyclase‐Stimulator Trial 1; 12 weeks; PAH) and CHEST‐1 (Chronic Thromboembolic Pulmonary Hypertension Soluble Guanylate Cyclase–Stimulator Trial 1; 16 weeks; CTEPH)—and long‐term extensions. Patients were initially randomized to receive placebo or riociguat, and they received riociguat in the extensions. Nonlinear mixed‐effects modeling was used to develop a population PK model describing riociguat PK. PK/PD relationships were investigated by comparing derived PK parameters with changes in PD parameters. Covariate analyses included smoking status, bosentan comedication, bilirubin levels, and baseline creatinine clearance. The PK of riociguat/M1 was described by a one‐compartment model. Mean population estimates for riociguat absorption rate constant, clearance, and volume of distribution were 2.17/h, 1.81 L/h, and 32.3 L, respectively; for M1 they were 0.258/h, 3.16 L/h, and 124 L. Interindividual variability was moderate for riociguat and moderate to high for M1. There was no evidence of time‐ or dose‐dependent changes in riociguat/M1 PK. Riociguat clearance was higher in smokers (120% increase) and bosentan‐treated patients (36% increase) than in nonsmokers and those not receiving bosentan. There was an inverse correlation between bilirubin and riociguat clearance. In PK/PD analyses, 6‐minute walk distance was related to hemodynamic parameters, particularly pulmonary vascular resistance. Riociguat PK were described by a one‐compartment model. Effects of covariates on riociguat and M1 PK were established, and a PK/PD relationship was demonstrated. ( ClinicalTrials.gov identifiers: PATENT‐1, NCT00810693; PATENT‐2, NCT00863681; CHEST‐1, NCT00855465; CHEST‐2, NCT00910429.)