Corina Becker

Pharmacokinetics of the soluble guanylate cyclase stimulator riociguat in individuals with renal impairment

Riociguat is the first oral soluble guanylate cyclase stimulator for the treatment of pulmonary hypertension. This pooled analysis of two non-randomized, non-blinded, observational studies evaluated the pharmacokinetics of riociguat and its metabolite M1 (BAY 60-4552) in individuals with and without renal impairment. Participants were assigned to 1 of 4 groups according to their creatinine clearance (CLCR): group 1, CLCR > 80 mL/min; group 2, CLCR 50–80 mL/min; group 3, CLCR 30–49 mL/min; group 4, CLCR < 30 mL/min. In the first study, group 4 received 0.5 mg riociguat; all other participants in both studies received 1 mg (single tablet doses). Pharmacokinetics were assessed using dense sampling. 63 participants (40 m, 23 f; age 36–78 years) completed the study. Riociguat was rapidly absorbed; median time to reach maximum concentration in plasma was 1 h in all 4 groups. Mean half-life of total riociguat was longer in groups 2–4 (9.5–11.4 h) than in group 1 (6.2 h), and renal clearance decreased with decreasing renal function. Exposure to total riociguat (mean area under the concentration–time curve/dose per kg body weight), was up to ∼100% higher in groups 2–4 than in group 1. However, exposure was highly variable in groups 2–4. Results for unbound riociguat and unbound M1 were similar to those for total riociguat and total M1. No serious or severe adverse events occurred. No change in safety or tolerability was observed with decreasing CLCR. Thus, the safety profile of riociguat in individuals with renal impairment was similar to that in healthy controls. Riociguat exposure was greater in individuals with renal impairment than in healthy controls, and was highly variable.

Assessment of the Effects of Hepatic Impairment and Smoking on the Pharmacokinetics of a Single Oral Dose of the Soluble Guanylate Cyclase Stimulator Riociguat (BAY 63-2521):

Riociguat, a soluble guanylate cyclase stimulator developed for the treatment of pulmonary hypertension, is metabolized in part by the liver. Expression of one of the metabolizing enzymes, CYP1A1, is induced by aromatic hydrocarbons in tobacco smoke. Two non-∗∗∗randomized, nonblinded studies were conducted to investigate the pharmacokinetics of riociguat in individuals with mild (Child-Pugh A) or moderate (Child-Pugh B) hepatic impairment associated with liver cirrhosis compared with that in age-, weight-, and sex-matched healthy controls: study 1 included smokers and nonsmokers, and study 2 included nonsmokers only. Data from these studies were integrated for analysis. All participants (N = 64) received a single oral dose of riociguat 1.0 mg. Riociguat exposure was significantly higher in individuals with Child-Pugh B hepatic impairment than in healthy controls (ratio: 153% [90% confidence interval: 103%-228%]) but was similar in those with Child-Pugh A hepatic impairment and controls. The half-life of the riociguat metabolite M1 was prolonged in patients with Child-Pugh B or A hepatic impairment compared with that in controls by approximately 43% and 24%, respectively. Impaired hepatic function was associated with higher riociguat exposure in nonsmokers compared with the population of smokers and nonsmokers combined. Riociguats safety profile was similar in individuals with impaired or normal liver function. In conclusion, moderate hepatic impairment was associated with increased riociguat exposure compared with that in controls, probably as a result of reduced clearance of the metabolite M1. This suggests that dose titration of riociguat should be administered with particular care in patients with moderate hepatic impairment.

Pharmacokinetic interaction of ketoconazole, clarithromycin, and midazolam with riociguat

Background Riociguat, an oral soluble guanylate cyclase stimulator, is under investigation for pulmonary hypertension treatment. Cytochrome P450 (CYP)-mediated oxidative metabolism is one of the major riociguat clearance pathways. The pharmacokinetic interactions between riociguat and ketoconazole (multi-pathway CYP and P-glycoprotein/ breast cancer resistance protein [P-gp/BCRP] inhibitor), clarithromycin (CYP3A4 inhibitor), and midazolam (CYP3A4 substrate) were investigated.

Population pharmacokinetics of single-dose riociguat in patients with renal or hepatic impairment

This population pharmacokinetics (PK) analysis characterized the PK of the oral soluble guanylate cyclase stimulator riociguat in patients with renal or hepatic impairment and determined whether smoking affects riociguat dosing. Two phase 1 studies were performed in patients with renal impairment (n = 72, of whom 11 were smokers), and two were performed in those with hepatic impairment (n = 64, of whom 12 were smokers). Plasma and urine samples were collected after a single oral dose of riociguat 1.0 or 0.5 mg. Nonlinear mixed-effects modeling was used to develop a combined, two-compartment population PK model for riociguat and its main metabolite, M1. Riociguat and M1 clearance was split into renal and nonrenal parts; the nonrenal part for riociguat was divided into metabolism to M1 and a metabolic (nonrenal) part. Total clearance of riociguat was 1.912 L/h. The main route of riociguat clearance is metabolism to M1 (1.2 L/h). In this model, hepatic function biomarkers or Child-Pugh classification had no significant effect on riociguat or M1 clearance. Nonrenal (nonmetabolism) riociguat clearance was similar in all groups. Renal clearance (0.242 L/h) contributed less to riociguat total clearance, mainly determined by glomerular filtration (0.174 L/h). Renal impairment reduced riociguat and M1 clearance. Hepatic or renal impairment had limited effects on total exposure to riociguat. However, individual dose adjustment of riociguat should be administered with particular care in patients with moderate hepatic or renal impairment. Riociguat is not recommended in severe hepatic or renal impairment. Smoking reduced riociguat exposure by significantly increasing metabolism to M1.

Bioavailability, pharmacokinetics, and safety of riociguat given as an oral suspension or crushed tablet with and without food

Riociguat is approved for the treatment of pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension. Some patients have difficulty swallowing tablets; therefore, 2 randomized, nonblinded, crossover studies compared the relative bioavailability of riociguat oral suspensions and immediate-release (IR) tablet and of crushed-tablet preparations versus whole IR tablet. In study 1, 30 healthy subjects received 5 single riociguat doses: 0.3 and 2.4 mg (0.15 mg/mL suspensions), 0.15 mg (0.03 mg/mL), and 1.0 mg (whole IR tablet) under fasted conditions and 2.4 mg (0.15 mg/mL) after a high-fat, high-calorie American-style breakfast. In study 2, 25 healthy men received 4 single 2.5-mg doses: whole IR tablet and crushed IR tablet suspended in applesauce and water, respectively, under fasted conditions, and whole IR tablet after a continental breakfast. In study 1, dose-normalized pharmacokinetics of riociguat oral suspensions and 1.0-mg whole IR tablet were similar in fasted conditions; 90% confidence intervals for riociguat area under the curve (AUC) to dose and mean maximum concentration (Cmax) to dose were within bioequivalence criteria. After food, dose-normalized AUC and Cmax decreased by 15% and 38%, respectively. In study 2, riociguat exposure was similar for all preparations; AUC ratios for crushed-IR-tablet preparations to whole IR tablet were within bioequivalence criteria. The Cmax increased by 17% for crushed IR tablet in water versus whole IR tablet. Food intake decreased Cmax of the whole tablet by 16%, with unaltered AUC versus fasted conditions. Riociguat bioavailability was similar between the oral suspensions and the whole IR tablet; exposure was similar between whole IR tablet and crushed-IR-tablet preparations. Minor food effects were observed. Results suggest that riociguat formulations are interchangeable.

Pharmacokinetic interaction of riociguat with ketoconazole, clarithromycin, and midazolam

Riociguat is a soluble guanylate cyclase stimulator for the treatment of pulmonary hypertension that is principally metabolized via the cytochrome P450 (CYP) pathway. Three studies in healthy males investigated potential pharmacokinetic interactions between riociguat and CYP inhibitors (ketoconazole, clarithromycin, and midazolam). In two studies, subjects were pretreated with either once-daily ketoconazole 400 mg or twice-daily clarithromycin 500 mg for 4 days before cotreatment with either riociguat 0.5 mg ± ketoconazole 400 mg or riociguat 1.0 mg ± clarithromycin 500 mg. In the third study, subjects received riociguat 2.5 mg 3 times daily (tid) for 3 days, followed by cotreatment with riociguat 2.5 mg tid ± midazolam 7.5 mg. Pharmacokinetic parameters, the effect of smoking on riociguat pharmacokinetics, safety, and tolerability were assessed. Pre- and cotreatment with ketoconazole and clarithromycin led to increased riociguat exposure. Pre- and cotreatment with riociguat had no significant effect on midazolam plasma concentrations. In all studies, the bioavailability of riociguat was reduced in smokers because its clearance to the metabolite M1 increased. Riociguat ± ketoconazole, clarithromycin, or midazolam was generally well tolerated. The most common treatment-emergent adverse events (TEAEs) across all studies were headache and dyspepsia. One serious TEAE was reported in the midazolam study. Owing to the potential for hypotension, concomitant use of riociguat with multipathway inhibitors, such as ketoconazole, should be approached with caution. Coadministration of riociguat with strong CYP3A4 inhibitors, for example, clarithromycin, does not require additional dose adjustment. No significant drug-drug interaction was revealed between riociguat and midazolam.

Effects of age and sex on the pharmacokinetics of the soluble guanylate cyclase stimulator riociguat (BAY 63-2521)

Riociguat is a soluble guanylate cyclase stimulator approved for the treatment of pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH). This randomized, double-blind, placebo-controlled study investigated the pharmacokinetics of riociguat and its metabolite M1 in young (18–45 years) and elderly (64.5–80 years) healthy volunteers of both sexes to assist planning of the dose regimens for clinical trials. The data were also used to draw comparisons with the effects of age and sex on riociguat pharmacokinetics in patients with PAH and CTEPH from the riociguat phase 3 trials, PATENT and CHEST. Volunteers received an oral dose of either riociguat 2.5 mg or placebo, and the concentrations of riociguat and M1 in blood and urine samples were determined using mass spectrometry. In elderly healthy volunteers, overall riociguat and M1 exposure tended to be higher than in young healthy volunteers (P >0.05),partly because of reduced renal clearance (approximately 28% reduction) and differences in body weight. Although the mean maximum concentrations of riociguat and M1 were significantly higher in women than in men (35% and 50% higher, respectively), total exposure was similar. Despite differences in riociguat and M1 pharmacokinetics, riociguat was well tolerated with a comparable safety profile across all subgroups, suggesting that differences in drug exposure due to age or sex were not sufficient to warrant a dose adjustment in clinical trials. Furthermore, similar pharmacokinetics were observed in patients with PAH and CTEPH. However, particular care should be exercised during individual dose titration of riociguat in elderly patients.

Absorption of riociguat (BAY 63-2521): bioavailability, food effects, and dose proportionality

Riociguat (BAY 63-2521) is the first member of a novel class of compounds, the soluble guanylate cyclase (sGC) stimulators. Riociguat has a dual mode of action: it sensitizes sGC to endogenous nitric oxide (NO) and stimulates sGC independent of NO availability. To characterize the biopharmaceutical properties of riociguat, including absolute bioavailability, food interactions, and dose proportionality, riociguat (intravenous/oral) was administered to healthy male subjects in 3 open-label, randomized, crossover studies: absolute bioavailability (1 mg; n = 22), food effect (2.5 mg; n = 23), and dose proportionality (0.5–2.5 mg; n = 24). Absolute bioavailability was 94% (95% confidence interval [CI], 83%–107%). Riociguat absorption was delayed by a high-fat breakfast with little effect on the extent of absorption (area under the concentration-time curve [AUC]fed : AUCfasted, 88% [90% CI, 82%–95%]). Exposure to riociguat was dose proportional over all doses (common slope of AUC, 1.09 [90% CI, 1.04–1.14]; maximum concentration, 0.98 [90% CI, 0.93–1.04]). Intraindividual variability was low; interindividual variability was moderate to high. Riociguat was well tolerated, and adverse events were consistent with the mode of action. In conclusion, riociguat shows complete oral absorption, no clinically relevant food effects, and a dose-proportional increase in systemic exposure (0.5–2.5 mg). These data support the suitability of the individualized dose adjustment scheme employed in the phase 3 clinical studies.

Pharmacokinetic interaction study between riociguat and the combined oral contraceptives levonorgestrel and ethinylestradiol in healthy postmenopausal women.

Female patients requiring treatment for pulmonary arterial hypertension (PAH) are advised to avoid pregnancy because of the high associated mortality rate. Oral contraception is one of the main methods of preventing pregnancy in this context, mandating pharmacokinetic and safety studies for new agents in this setting. Riociguat is a soluble guanylate cyclase stimulator approved for treatment of PAH and inoperable and persistent or recurrent chronic thromboembolic pulmonary hypertension. This single-center, randomized, nonblinded study involving healthy postmenopausal women investigated the effect of riociguat on plasma concentrations of levonorgestrel (0.15 mg) and ethinylestradiol (0.03 mg) in a combined oral contraceptive. Treatment A was a single oral tablet of levonorgestrel-ethinylestradiol. In treatment B, subjects received 2.5 mg riociguat 3 times daily for 12 days. On the eighth day, they also received a single oral tablet of levonorgestrel-ethinylestradiol. Subjects received both regimens in a crossover design. There was no change in area under the plasma concentration—time curves of levonorgestrel or ethinylestradiol or maximum concentration in plasma (Cmax) of levonorgestrel during combined administration versus levonorgestrel-ethinylestradiol alone. A 20% increase in the Cmax of ethinylestradiol was noted during coadministration; this is not anticipated to adversely impact the contraceptive efficacy or to require any dose adjustment for ethinylestradiol. Plasma concentrations and exposures of riociguat were within the expected range and were not influenced by coadministration with levonorgestrel-ethinylestradiol. Combined treatment was safe and well tolerated. In conclusion, riociguat did not change the exposure to levonorgestrel or ethinylestradiol relative to oral contraceptive administered alone.

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.)