Clinical pharmacokinetics and pharmacodynamics of the endothelin receptor antagonist macitentan

Identifying the Interaction Between Tuberculosis and SARS-CoV-2 Infections via Bioinformatics Analysis and Machine Learning

The number of patients with COVID-19 caused by severe acute respiratory syndrome coronavirus 2 is still increasing. In the case of COVID-19 and tuberculosis (TB), the presence of one disease affects the infectious status of the other. Meanwhile, coinfection may result in complications that make treatment more difficult. However, the molecular mechanisms underpinning the interaction between TB and COVID-19 are unclear. Accordingly, transcriptome analysis was used to detect the shared pathways and molecular biomarkers in TB and COVID-19, allowing us to determine the complex relationship between COVID-19 and TB. Two RNA-seq datasets (GSE114192 and GSE163151) from the Gene Expression Omnibus were used to find concerted differentially expressed genes (DEGs) between TB and COVID-19 to identify the common pathogenic mechanisms. A total of 124 common DEGs were detected and used to find shared pathways and drug targets. Several enterprising bioinformatics tools were applied to perform pathway analysis, enrichment analysis and networks analysis. Protein-protein interaction analysis and machine learning was used to identify hub genes (GAS6, OAS3 and PDCD1LG2) and datasets GSE171110, GSE54992 and GSE79362 were used for verification. The mechanism of protein-drug interactions may have reference value in the treatment of coinfection of COVID-19 and TB.

Bioequivalence and the food effect of macitentan/tadalafil 10/20 fixed-dose combination tablets versus the use of single-component tablets in healthy subjects

The primary aim was to demonstrate bioequivalence between the 10/20 mg fixed-dose combination (FDC) of macitentan/tadalafil in a single tablet and the free combination of both drugs, and to evaluate the food effect on the 10/20 mg FDC in healthy participants. In this single-center, randomized, open-label, 3-way crossover, single-dose Phase 1 study in healthy adult participants, macitentan/tadalafil was administered as a 10/20 mg FDC formulation and compared with the free combination of macitentan and tadalafil. The food effect on the FDC was also evaluated. Pharmacokinetic sampling (216 h) was conducted. The 90% confidence intervals (CIs) for the geometric mean ratios of maximum observed plasma analyte concentration (Cmax) and area under the plasma analyte concentration-time curves (AUCs) for Treatment A (FDC, fasted) versus C (free combination, fasted) were within bioequivalence limits demonstrating that the FDC formulation can be considered bioequivalent to the free combination. The 90% CIs for the geometric mean ratios of Cmax and AUC for Treatment B (FDC, fed) versus A (FDC, fasted) were contained within bioequivalence limits demonstrating that there was no food effect. The administration of the 10/20 mg FDC was generally safe and well tolerated in healthy participants. This study demonstrated bioequivalence between the FDC of macitentan/tadalafil (10/20 mg) in a single tablet and the free combination of both drugs in healthy participants, and that the FDC can be taken without regard to food, similarly to the individual components. The FDC was generally safe and well tolerated.

Resistant Hypertension: Disease Burden and Emerging Treatment Options

PURPOSE OF REVIEW

To define resistant hypertension (RHT), review its pathophysiology and disease burden, identify barriers to effective hypertension management, and to highlight emerging treatment options.

RECENT FINDINGS

RHT is defined as uncontrolled blood pressure (BP) ≥ 130/80 mm Hg despite concurrent prescription of ≥ 3 or ≥ 4 antihypertensive drugs in different classes or controlled BP despite prescription of  ≥ to 4 drugs, at maximally tolerated doses, including a diuretic. BP is regulated by a complex interplay between the renin-angiotensin-aldosterone system, the sympathetic nervous system, the endothelin system, natriuretic peptides, the arterial vasculature, and the immune system; disruption of any of these can increase BP. RHT is disproportionately manifest in African Americans, older patients, and those with diabetes and/or chronic kidney disease (CKD). Amongst drug-treated hypertensives, only one-quarter have been treated intensively enough (prescribed > 2 drugs) to be considered for this diagnosis. New treatment strategies aimed at novel therapeutic targets include inhibition of sodium-glucose cotransporter 2, aminopeptidase A, aldosterone synthesis, phosphodiesterase 5, xanthine oxidase, and dopamine beta-hydroxylase, as well as soluble guanylate cyclase stimulation, nonsteroidal mineralocorticoid receptor antagonism, and dual endothelin receptor antagonism. The burden of RHT remains high. Better use of currently approved therapies and integrating emerging therapies are welcome additions to the therapeutic armamentarium for addressing needs in high-risk aTRH patients.

Effects of bergapten on the pharmacokinetics of macitentan in rats both in vitro and in vivo

Macitentan was approved by the United States Food and Drug Administration (FDA) in 2013 for the treatment of pulmonary arterial hypertension (PAH). Bergapten is a furanocoumarin that is abundant in Umbelliferae and Rutaceae plants and is widely used in many Chinese medicine prescriptions. Considering the possible combination of these two compounds, this study is aimed to investigate the effects of bergapten on the pharmacokinetics of macitentan both in vitro and in vivo. Rat liver microsomes (RLMs), human liver microsomes (HLMs), and recombinant human CYP3A4 (rCYP3A4) were used to investigate the inhibitory effects and mechanisms of bergapten on macitentan in vitro. In addition, pharmacokinetic parameters were also studied in vivo. Rats were randomly divided into two groups (six rats per group), with or without bergapten (10 mg/kg), and pretreated for 7 days. An oral dose of 20 mg/kg macitentan was administered to each group 30 min after bergapten or 0.5% CMC-Na administration on day 7. Blood was collected from the tail veins, and the plasma concentrations of macitentan and its metabolites were assessed by ultra-performance liquid chromatography - tandem mass spectrometer (UPLC-MS/MS). Finally, we analyzed the binding force of the enzyme and two small ligands by in silico molecular docking to verify the inhibitory effects of bergapten on macitentan. The in vitro results revealed that the IC₅₀ values for RLMs, HLMs, and rCYP3A4 were 3.84, 17.82 and 12.81 μM, respectively. In vivo pharmacokinetic experiments showed that the AUC_(0-t), AUC_(0-∞), and C_max of macitentan in the experimental group (20,263.67 μg/L*h, 20,378.31 μg/L*h and 2,999.69 μg/L, respectively) increased significantly compared with the control group (7,873.97 μg/L*h, 7,897.83 μg/L*h and 1,339.44 μg/L, respectively), while the CL_z/F (1.07 L/h/kg) of macitentan and the metabolite-parent ratio (MR) displayed a significant decrease. Bergapten competitively inhibited macitentan metabolism in vitro and altered its pharmacokinetic characteristics in vivo. Further molecular docking analysis was also consistent with the experimental results. This study provides a reference for the combined use of bergapten and macitentan in clinical practice.

Current Status of Endothelin Receptor Antagonists in Pulmonary Arterial Hypertension: A Combined Study Results and Pharmacology-Based Review

Pulmonary arterial hypertension (PAH) affects a wide range of people globally and has a poor prognosis despite many advancements in available treatment options. Among the available treatments, endothelin receptor antagonists (ERA) are among the most widely used drugs. These drugs have been evaluated in scientific trials. We included free full texts in the English language from the last ten years and reviewed them. We are writing this review to amalgamate the pharmacological aspects and the previous studies on ERAs to demonstrate a comprehensive overview of the current status of ERAs for PAH treatment. We focused on the structure, pharmacodynamics, pharmacokinetics, and efficacy and safety of the three most widely used ERAs: Bosentan, Ambrisentan, and Macitentan. These drugs have different receptor affinities, bioavailability, excretion routes, and different levels of safety profiles. There are three available studies, the RCT, the ARIES series, and the SERAPHIN studies, for assessing the safety and efficacy of Bosentan, Ambrisentan, and Macitentan, respectively. All the studies and some additional studies for combination therapy have proven all three drugs effective in treating PAH. The side effects (SE) varied from headache and hepatic enzyme elevation to worsening the PAH status of varied severities. Although these studies provided valuable insight into the role of ERAs, there is still enough scope for more studies on ERAs, both as monotherapy and combination therapy for PAH.

Nanomedicine-mediated therapeutic approaches for pulmonary arterial hypertension

Nanomedicine has emerged as a field in which there are opportunities to improve the diagnosis, treatment and prevention of incurable diseases. Pulmonary arterial hypertension (PAH) is known as a severe and fatal disease affecting children and adults. Conventional treatments have not produced optimal effectiveness in treating this condition. Several reasons for this include drug instability, poor solubility of the drug and a shortened duration of pharmacological action. The present review focuses on new approaches for delivering anti-PAH drugs using nanotechnology with the aim of overcoming these shortcomings and increasing their efficacy. Solid-lipid nanoparticles, liposomes, metal-organic frameworks and polymeric nanoparticles have demonstrated advantages for the potential treatment of PAH, including increased drug bioavailability, drug solubility and accumulation in the lungs.

Pharmacological counseling in hepatotoxicity induced by macitentan and selexipag: a case report

Background

Pulmonary arterial hypertension is a progressive, debilitating condition characterized by increased resistance in the pulmonary arterial circulation. Current treatments for pulmonary arterial hypertension include endothelin receptor antagonists such as bosentan, sitaxentan, ambrisentan, macitentan, and oral prostacyclin receptor agonists such as selexipag. Endothelin receptor antagonists have been associated with liver injury, while hepatotoxicity was not reported for selexipag. Although genetic variability has been indisputably associated with variability in drug response, no study has been designed until now to assess its effects on the pharmacokinetics of endothelin receptor antagonists or selexipag.

Case presentation

We report the case of a 58-year-old female Caucasian patient with a dramatic increase in plasma levels of transaminases after treatment with macitentan and selexipag, drugs whose risk of causing liver injury has so far been considered limited. After therapy discontinuation, plasma levels of transaminases returned to baseline, thus suggesting a role of these drugs in the observed hepatotoxicity. After pharmacological counseling, we decided to introduce ambrisentan for the patient’s treatment. After 7 months of treatment, no liver injury has been reported. To evaluate the role of genetic factors in the observed hepatotoxicity, we genotyped the patient for single-nucleotide polymorphisms previously associated with macitentan, ambrisentan, or selexipag metabolism. We found a genetic profile associated with a poor metabolizer (PM) phenotype for CYP2C8 and CYP2C9, key enzymes for elimination of both macitentan and selexipag. The reported results suggest that an allelic profile associated with low activity for CYP2C8 and CYP2C9 enzyme could be a potential risk factor for macitentan and selexipag-induced liver injury and could provide a possible marker for early identification of subjects at higher risk of developing hepatotoxicity.

Conclusions

A multidisciplinary approach based on clinical evaluation, as well as pharmacological counseling and evaluation of the patient’s genetic profile, might be useful for identification of patients with a high chance of drug-induced liver injury, avoiding unnecessary risks in therapy selection and prescription.

Protective Effect of Triclosan in Monocrotaline-Induced Pulmonary Arterial Hypertension: FASN Inhibition a Novel Approach

Background

Novel pharmacological approaches are needed to improve the outcomes of patients with idiopathic pulmonary hypertension. Fatty acid synthase (FASN) inhibitors have shown beneficial effects in preclinical models of pulmonary arterial hypertension (PAH), because of their role in the regulation of pulmonary artery vasoconstrictor tone and remodeling.

Objective

We compared a Triclosan (FASN inhibitor), for the first time with the dual endothelin receptor antagonist, macitentan, in a monocrotaline-induced rat pulmonary hypertension model.

Methods

Different methods (hemodynamics, histology of right ventricle and pulmonary vessels, and circulating biomarkers) showed consistently that 30 mg/kg daily of Triclosan (FASN inhibitor) and 10 mg/kg daily of macitentan slowed the progression of PAH both at the functional and structural levels.

Results

Treatments started on day 14 after monocrotaline injection and lasted 14 days. The findings of all experimental methods show that the FASN inhibitor has more similar effects as compared to macitentan.

Conclusion

Our study reveals that inhibition of FAS decreases RV hypertrophy and improves cardiac function associated with PAH with the regulation of metabolic functions and governs further studies to establish "FASN inhibitor as a potential therapeutic approach" for the management of PAH.

Effects of Concomitant Administration of PXR Ligand Drugs on the Anticoagulant Effects of Warfarin

We encountered cases in which the anticoagulant effects of warfarin (CYP2C9 substrate) were reversibly attenuated by the concomitant administration of rifampicin or bosentan, which are potent pregnane X receptor (PXR) ligands. The purpose of the present study is to report the previous case with rifampicin, and to evaluate the changes in the warfarin anticoagulant effects when withdrawing or switching bosentan treatment. The former is a case study of a 4-year-old girl undergoing warfarin treatment. The latter is a longitudinal study of 20 pediatric patients receiving stable warfarin treatment. The prothrombin time and international normalized ratio (PT-INR) values were extracted from the medical records and normalized by the daily-dose per body size as an index for the warfarin anticoagulant effects. Rifampicin treatment resulted in a 52.0% decrease in the anticoagulant index. On the other hand, 10 of 20 patients started bosentan and their anticoagulant index was reduced by a median of 2.00. Bosentan was withdrawn in 4 of 20 patients and their anticoagulant index increased by a median of 3.67. Six of 20 patients switched from bosentan to macitentan, which is considered not to activate PXR in clinical settings. However, switching from bosentan to macitentan resulted in a median of 2.25 reduction of the anticoagulant index rather than recovery of the response to warfarin. This study suggests not only the possibility of heterogeneity in the response to PXR activation and deactivation, but also the importance of long-term monitoring of drug-drug interactions when switching from bosentan to macitentan.

The Endothelin Receptor Antagonist Macitentan Inhibits Human Cytomegalovirus Infection

Human cytomegalovirus (HCMV) infection is an important cause of morbidity and mortality in immunocompromised patients and a major etiological factor for congenital birth defects in newborns. Ganciclovir and its pro-drug valganciclovir are the preferred drugs in use today for prophylaxis and treatment of viremic patients. Due to long treatment times, patients are at risk for developing viral resistance to ganciclovir and to other drugs with a similar mechanism of action. We earlier found that the endothelin receptor B (ETBR) is upregulated during HCMV infection and that it plays an important role in the life cycle of this virus. Here, we tested the hypothesis that ETBR blockade could be used in the treatment of HCMV infection. As HCMV infection is specific to humans, we tested our hypothesis in human cell types that are relevant for HCMV pathogenesis; i.e., endothelial cells, epithelial cells and fibroblasts. We infected these cells with HCMV and treated them with the ETBR specific antagonist BQ788 or ETR antagonists that are approved by the FDA for treatment of pulmonary hypertension; macitentan, its metabolite ACT-132577, bosentan and ambrisentan, and as an anti-viral control, we used ganciclovir or letermovir. At concentrations expected to be relevant in vivo, macitentan, ACT-132577 and BQ788 effectively inhibited productive infection of HCMV. Of importance, macitentan also inhibited productive infection of a ganciclovir-resistant HCMV isolate. Our results suggest that binding or signaling through ETBR is crucial for viral replication, and that selected ETBR blockers inhibit HCMV infection.

Bioequivalence and food effect of a fixed-dose combination of macitentan and tadalafil: Adaptive design in the COVID-19 pandemic

The COVID‐19 pandemic has forced clinical studies to accommodate imposed limitations. In this study, the bioequivalence part could not be conducted as planned. Thus, the aim was to demonstrate bioequivalence, using an adaptive study design, of tadalafil in fixed‐dose combination (FDC) tablets of macitentan/tadalafil with single macitentan and tadalafil (Canadian‐sourced) tablets and assess the effect of food on FDC tablets in healthy subjects. This Phase 1, single‐center, open‐label, single‐dose, two‐part, two‐period, randomized, crossover study enrolled 62 subjects. Tadalafil bioequivalence as part of FDC of macitentan/tadalafil (10/40 mg) with single‐component tablets of macitentan (10 mg) and tadalafil (40 mg) was determined by pharmacokinetic (PK) assessment under fasted conditions. The effect of food on FDC was evaluated under fed and fasted conditions. Fasted 90% confidence intervals (CIs) for geometric mean ratios (GMRs) were within bioequivalence limits for tadalafil and macitentan. Fed and fasted 90% CIs for area under the curve (AUC) GMR were within bioequivalence limits. However, 90% CIs for maximum plasma concentration (C_max) GMR for macitentan and tadalafil were outside bioequivalence limits. One FDC‐treated subject experienced a serious adverse event of transient ischemic attack (bioequivalence part). To address pandemic‐imposed limitations, an adaptive study design was implemented to demonstrate that the FDC tablet was bioequivalent to the free combination of macitentan and tadalafil (Canadian‐sourced). No clinically significant differences in PK were determined between fed and fasted conditions; the FDC formulation could be taken irrespective of meals. The FDC formulation under fasted and fed conditions was well tolerated with no clinically relevant differences in safety profiles between the treatment groups.

NCT Number: NCT04235270.

Liver abnormalities in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a cardiopulmonary disease with high mortality. In recent years, it has been recognized that PAH is a multi-organ system disease, involving the systemic circulation, kidneys, skeletal muscles, and the central nervous system, among others. Right heart failure produces congestive hepatopathy, a disease state that has direct consequences on liver biochemistry, histology, and systemic glucose and lipid metabolism. This article aims to summarize the consequences of congestive hepatopathy with an emphasis on liver biochemistry, histology, and PAH-targeted therapy. Furthermore, PAH-specific changes in glucose and lipid metabolism will be discussed.

A Population Pharmacokinetic Model of Macitentan and Its Active Metabolite Aprocitentan in Healthy Volunteers and Patients with Pulmonary Arterial Hypertension

BACKGROUND

Macitentan and its active metabolite, aprocitentan, are non-peptide, potent, dual endothelin receptor antagonists. Macitentan is approved for the treatment of pulmonary arterial hypertension in adults, at a dose of 10 mg/day.

OBJECTIVE

The objective of this study was to develop a comprehensive population model to describe the pharmacokinetics of macitentan and aprocitentan in healthy adults and adult subjects with pulmonary arterial hypertension.

METHODS

Pharmacokinetic data of 452 subjects in nine studies, after single and repeated doses (dose range 0.2-600 mg), were pooled for a non-linear mixed-effects analysis and the assessment of covariates, i.e., body weight, age, sex, race, renal and hepatic impairment, health status (healthy volunteers vs patients with pulmonary arterial hypertension), and formulation (capsules vs tablets) on pharmacokinetic parameters.

RESULTS

The final model was an open one-compartment disposition model, with linear elimination for macitentan and linear formation and elimination for aprocitentan. A semi-mechanistic absorption model described the dose dependency and multiple peaks observed for macitentan. For a female patient with pulmonary arterial hypertension after oral administration at 10 mg, macitentan reached a maximum concentration after 9 h and, following daily dosing, reached steady state after 3 days with a twofold accumulation factor. The apparent volume of distribution was 34 L and clearance was 1.39 L/h. Aprocitentan reached maximum concentration after 51 h and steady state after 9 days, with a 12.5-fold accumulation factor. Body weight, sex, race, renal impairment, health status, and formulation were statistically significant covariates on pharmacokinetic parameters.

CONCLUSIONS

The comprehensive population pharmacokinetic model adequately described the pharmacokinetics of macitentan and aprocitentan across different dose concentrations, regimens, and formulations. Several covariates significantly influenced the pharmacokinetics of macitentan and aprocitentan, but none was considered clinically relevant.

The endothelin receptor antagonist macitentan for the treatment of pulmonary arterial hypertension: A cross-species comparison of its cytochrome P450 induction pattern

The dual endothelin receptor antagonist macitentan was approved in 2013 for the treatment of pulmonary arterial hypertension. Macitentan is an inducer of cytochrome P450 expression in vivo in animal species but not in man. In rat and dog, changes in P450 expression manifest as autoinduction upon repeat dosing. The induction pattern, however, significantly differed between both species, and between male and female rats. While macitentan exposure steadily declined with dose in the dog, P450 induction was saturable in the rat reaching levels of 40%-60% and 60%-80% at steady-state in male and female animals, respectively. The nature and number of P450 enzymes involved in macitentan clearance were identified as a major reason for the observed species differences. In the dog, macitentan was metabolized by a single P450 enzyme, that is, Cyp3a12, whereas several members of the Cyp2c and Cyp3a families were involved in the rat. Macitentan selectively upregulated Cyp3a expression in rat, whereas the expression of the Cyp2c enzymes involved in macitentan metabolism remained mostly unchanged, eventually leading to a higher contribution of Cyp3a upon induction. Macitentan also induced CYP3A4 expression in human hepatocytes via initial activation of the human pregnane X receptor. No such induction was evident in humans at the therapeutic macitentan dose of 10 mg as shown in a clinical drug-drug interaction study with the CYP3A4 substrate sildenafil.

Bioequivalence of macitentan and tadalafil given as fixed-dose combination or single-component tablets in healthy subjects

Aims

To demonstrate the bioequivalence of macitentan/tadalafil fixed‐dose combination (FDC) tablets with single‐component tablets of macitentan and tadalafil in healthy subjects.

Methods

Studies AC‐077‐101 and AC‐077‐103 were single‐centre, open‐label, single‐dose, 2‐period, randomized, crossover Phase 1 studies conducted in healthy subjects. Two FDCs were investigated: FDC‐1 and FDC‐2 in Study AC‐077‐101 and FDC‐2 in Study AC‐077‐103. Both FDCs contained 10 mg/40 mg of macitentan/tadalafil and differed in excipients and coating materials used. In both studies, pharmacokinetic sampling over 216 hours was conducted, and pharmacokinetic parameters were derived using noncompartmental methods.

Results

Bioequivalence of macitentan, its active metabolite ACT‐132577, and tadalafil was established for FDC‐2 in both studies AC‐077‐101 and AC‐077‐103 in which tadalafil as a single component was sourced from the USA and EU, respectively, to fulfil regional regulatory requirements. The area under the plasma concentration–time curve and maximum plasma concentration with 90% confidence intervals of all components were entirely within the bioequivalence limits (0.8000–1.2500). No subject died and no serious adverse events were reported in either studies.

Conclusion

The FDC‐2 tablet containing 10 mg/40 mg of macitentan/tadalafil was bioequivalent to the free combination of 10 mg macitentan and 40 mg tadalafil (both US and EU sourced). Macitentan and tadalafil were well tolerated when administered as FDC or as a free combination.

Relative bioavailability of a pediatric dispersible tablet and adult film-coated tablet of macitentan in healthy volunteers

To compare the pharmacokinetic (PK) properties of the pediatric dispersible tablet formulation of macitentan and the adult film-coated tablet formulation of macitentan in healthy subjects. A randomized, open-label, single-dose, two-sequence, two-period, crossover, Phase 1 study was conducted in 12 healthy adults. Subjects were randomized to one of the two possible treatment sequences A/B or B/A on Day 1 under fasted conditions. Treatment A was a single 10 mg dose of macitentan (film-coated adult formulation) and Treatment B was a single 10 mg dose of macitentan, consisting of two 5 mg dispersible tablets (pediatric formulation). PK sampling over 216 hours was conducted, and PK parameters were derived using non-compartmental methods. For macitentan, geometric means ratio of peak plasma concentrations (Cmax ), plasma concentration-time curve from zero to the time of the last quantifiable concentration (AUC0-t ), and plasma concentration-time curve from zero to infinity (AUC0-∞ ) were 1.140, 0.974, and 0.974, respectively. The corresponding 90% confidence intervals fell entirely within the referenced range of 0.8000 to 1.2500, which is used for evaluation of bioequivalence. These results indicate no significant differences between the pediatric dispersible tablet and the adult film-coated tablet. Both formulations were well tolerated. The pediatric dispersible tablet is biocomparable to the adult film-coated tablet formulation.

Effect of Macitentan on the Pharmacokinetics of the Breast Cancer Resistance Protein Substrates, Rosuvastatin and Riociguat, in Healthy Male Subjects

Background

Macitentan is a clinically approved endothelin receptor antagonist for the treatment of pulmonary arterial hypertension (PAH). Increasing use of combination drug therapy in PAH means that it is important to recognize potential drug–drug interactions (DDIs) that could affect the efficacy and safety of macitentan in patients with PAH.

Objective

Two Phase 1 studies were conducted to investigate the effect of macitentan at steady-state on the pharmacokinetics of the breast cancer resistance protein (BCRP) substrates, rosuvastatin and riociguat in healthy male subjects. Another objective was to determine the safety and tolerability of concomitant administration of rosuvastatin or riociguat with macitentan.

Methods

Healthy male subjects received a single oral dose of rosuvastatin 10 mg (n = 20) or riociguat 1 mg (n = 20) on Day 1 (reference treatment). A loading oral dose of macitentan 30 mg was administered on Day 5 followed by macitentan 10 mg once-daily from Day 6 to Day 15 (riociguat study) or Day 6 to Day 16 (rosuvastatin study). A concomitant oral dose of rosuvastatin 10 mg or riociguat 1 mg was administered on Day 10 (test treatment). Pharmacokinetics were evaluated for 96 h after treatment on Day 1 and for 144 h (riociguat study) or 168 h (rosuvastatin study) after treatment on Day 10. To compare the reference and test treatments, the geometric mean ratio was calculated for the maximum plasma concentration (C_max), the area under the plasma concentration-time curve (AUC) from zero (pre-dose) to time of the last measured concentration above the limit of quantification (AUC_0–t), the AUC from zero to infinity (AUC_0–∞) and the terminal elimination half-life (t_½) of rosuvastatin, riociguat and riociguat’s metabolite, M1. The difference in the time to reach maximum plasma concentration (t_max) was determined by the Wilcoxon test. Trough levels of macitentan and its metabolite, ACT-132577, were measured and safety was monitored throughout.

Results

Ninety percent confidence intervals of the geometric mean ratios were within the bioequivalence criteria of 0.80–1.25. There was no significant difference between test and reference t_max. Rosuvastatin or riociguat did not affect the steady-state concentrations of macitentan and ACT-132577. The adverse event profile was consistent with the known safety profiles of the drugs.

Conclusions

Macitentan 10 mg did not affect the pharmacokinetics of BCRP substrates, rosuvastatin or riociguat in healthy male subjects.

EudraCT numbers: 2017–003095–31 and 2017–003502–41.

Monocrotaline-induced pulmonary arterial hypertension: Time-course of injury and comparative evaluation of macitentan and Y-27632, a Rho kinase inhibitor

Novel pharmacological approaches are needed to improve outcomes of patients with idiopathic pulmonary hypertension. Rho-associated protein kinase (ROCK) inhibitors have shown beneficial effects in preclinical models of pulmonary arterial hypertension (PAH), because of their role in the regulation of pulmonary artery vasoconstrictor tone and remodeling. We compared a ROCK inhibitor, Y-27632, for the first time with the dual endothelin receptor antagonist, macitentan, in a monocrotaline-induced rat pulmonary hypertension model. Different methods (echocardiography, hemodynamics, histology of right ventricle and pulmonary vessels, and circulating biomarkers) showed consistently that 100 mg/kg daily of Y-27632 and 10 mg/kg daily of macitentan slowed the progression of PAH both at the functional and structural levels. Treatments started on day 14 after monocrotaline injection and lasted 14 days. The findings of all experimental methods show that the selective ROCK inhibitor Y-27632 has more pronounced effects than macitentan, but a major limitation to its use is its marked peripheral vasodilating action.

Single- and multiple-dose tolerability, safety, pharmacokinetics, and pharmacodynamics of the dual endothelin receptor antagonist aprocitentan in healthy adult and elderly subjects

Background

Aprocitentan is an orally active, dual endothelin (ET) receptor antagonist developed for the treatment of hypertension in which, despite available treatments, a medical need exists for drugs with a new mechanism of action.

Subjects and methods

In this study, the single- and multiple-dose tolerability, safety, pharmacokinetics (PK), and pharmacodynamics of up to 600 mg (single doses) and 100 mg once a day (qd; multiple doses) of aprocitentan were investigated in healthy male and female subjects. The effect of age on the tolerability and PK parameters was investigated at a dose of 100 mg qd.

Results

Aprocitentan was well tolerated across all doses. No serious adverse events (AEs) occurred. The most frequently reported AE was headache. Small increases in body weight were recorded in subjects receiving 100 mg qd. Plasma concentration-time profiles of aprocitentan were similar after single- and multiple-dose administration, and support a qd dosing regimen based on a half-life of 44 hours. After multiple doses, PK was dose proportional. Accumulation at steady state, reached by Day 8, was 3-fold. Only minor differences in exposure between healthy females and males, healthy elderly and adult subjects, and fed and fasted conditions were observed. Plasma ET-1 concentrations, reflecting ET_B receptor antagonism, significantly increased with doses ≥25 mg. Time-matched analysis of electrocardiogram (ECG) parameters did not suggest drug-induced ECG effects. Exposure-response analysis indicated no QTc prolongations at plasma levels up to 10 µg/mL.

Conclusion

Aprocitentan was well tolerated in healthy subjects with a PK profile favorable for qd dosing.

Rivaroxaban and macitentan can be coadministered without dose adjustment but the combination of rivaroxaban and St John's wort should be avoided

AIMS

We assessed the potential mutual interaction of oral macitentan (cytochrome P450 (CYP) 3A4 substrate) at steady-state with single-dose oral rivaroxaban (CYP3A4 and P-glycoprotein substrate) and evaluated the effect of the CYP3A and P-glycoprotein inducer St John's wort (SJW) on the pharmacokinetics of these drugs in healthy volunteers.

METHODS

Twelve healthy volunteers completed this open-label, monocentre, two-period, one-sequence phase I clinical trial. The pharmacokinetics of macitentan (10 mg) was assessed on study days 3 (single dose), 15 (steady-state), 16 (impact of rivaroxaban) and 29 (after induction by oral SJW), and of rivaroxaban on days 2 (single dose), 16 (impact of macitentan at steady-state) and 29 (after induction by SJW). Concurrently, we quantified changes of CYP3A activity using oral microdoses of midazolam (30 μg).

RESULTS

Rivaroxaban and macitentan did not significantly change the pharmacokinetics of each other. After induction with SJW, CYP3A activity increased by 272% and geometric mean ratios of macitentan AUC decreased by 48% and of C_max by 45%. Concurrently, also geometric mean ratios of rivaroxaban AUC and C_max decreased by 25%.

CONCLUSIONS

There is no evidence for a relevant pharmacokinetic interaction between macitentan and rivaroxaban suggesting that these two drugs can be combined without dose adjustment. SJW strongly increased CYP3A activity and substantially reduced rivaroxaban and macitentan exposure while estimated net endothelin antagonism only decreased by 20%, which is considered clinically irrelevant. The combination of SJW with rivaroxaban should be avoided.

Endothelin-receptor antagonists in the management of pulmonary arterial hypertension: where do we stand?

Pulmonary arterial hypertension, a disease largely neglected until a few decades ago, is presently the object of intense studies by several research teams. Despite considerable progress, pulmonary arterial hypertension remains a major clinical problem, because it is not always easy to diagnose, treat, and prevent. The disease was considered incurable until the late 1990s, when Epoprostenol was introduced as the first tool against this illness. More recently, therapy for pulmonary arterial hypertension gained momentum after publication of the SERAPHIN and AMBITION trials, which also highlighted the importance of upfront therapy. This review also focuses on recent substudies from these trials and progress in drugs targeting the endothelin pathway. Future perspectives with regard to endothelin-receptor antagonists are also discussed.

A Focus on Macitentan in the Treatment of Pulmonary Arterial Hypertension

The approval of macitentan has increased the number of pharmacological treatments of pulmonary arterial hypertension (PAH). Here, we review the effect on PAH of macitentan compared to other endothelin receptor antagonists. Drugs targeting the endothelin (ET) pathway include the selective ET_A receptor antagonist ambrisentan, the ET_A /ET_B receptor antagonists, bosentan and macitentan, which were recently approved for PAH treatment. Macitentan exhibits higher antagonistic potency than bosentan and ambrisentan in pulmonary smooth muscle cells. Compared to ambrisentan and bosentan, macitentan has a longer duration of action, reflected by the longer half-life, as well as pharmacodynamics attributed to its active metabolite, ACT-132577. The efficacy of macitentan on PAH was investigated in the phase III SERAPHIN trial (NCT00660179). Macitentan significantly reduced morbidity and mortality. It improved the 6-min. walk distance (6MWD) among PAH patients. In the AMB-320/321-E (NCT00578786) study, ambrisentan improved exercise capacity. In the EARLY study (NCT00091715), bosentan showed improvements in 6MWD which were not statistically significant. Bosentan had an effect on PAH in patients with Eisenmenger syndrome (ES) in the BREATHE-5 study (NCT00367770), while macitentan did not improve 6MWD in these patients, but there are differences regarding study size and functional class, and that 30% of the patients treated with macitentan were already in treatment with a phosphodiesterase type 5 inhibitor. Macitentan revealed a lower risk of developing peripheral oedema and hepatotoxicity in the SERAPHIN study. In summary, macitentan has an efficiency comparable to bosentan and ambrisentan in the treatment of PAH. Patients treated with macitentan exhibited less adverse effects compared to bosentan and ambrisentan. In patients with PAH associated with ES, the trials with bosentan and macitentan do not seem comparable, and it needs to be clarified whether these drugs are effective when administered as part of a combination treatment in this condition.

Modeling of pharmacokinetics, efficacy, and hemodynamic effects of macitentan in patients with pulmonary arterial hypertension

BACKGROUND

Macitentan is the first endothelin receptor antagonist with demonstrated efficacy on morbidity and mortality in pulmonary arterial hypertension (PAH) in the pivotal study SERAPHIN.

METHODS

The pharmacokinetics (PK) of macitentan and its active metabolite, ACT-132577, were characterized in a population model. Efficacy and hemodynamics (pharmacodynamics, PD) were related to PK based on PK/PD modeling.

RESULTS

Sex, age, and body weight influenced the PK to a statistically significant extent. Model-based simulations showed that these variables are clinically not relevant. Concomitant use of PAH medication (PDE-5 inhibitors) did not influence macitentan trough concentration to a relevant extent. Efficacy and hemodynamics showed clear differences from placebo for macitentan concentrations on 3 and 10 mg with consistent superior effects for 10 mg. After 6 months, PAH patients showed model-predicted 6-min walk distance (6-MWD) improvements of 1.0 m on placebo compared to 29.8 and 34.1 m on 3 and 10 mg of macitentan, respectively. Higher macitentan concentrations were associated with reductions in pulmonary vascular resistance (PVR), mean right atrial and pulmonary arterial pressure, and total pulmonary resistance (TPR) and increases in cardiac index (CI) and mixed venous oxygen saturation. Statistical significance was determined for PVR, TPR, and CI but not for 6-MWD. In addition, PVR showed more pronounced differences between active treatment and placebo than 6-MWD.

CONCLUSIONS

Modeling identified statistically significant inter-patient differences; simulations to assess the magnitude of the effects permitted clinical judgment. The same approach will allow for extrapolation to children. Hemodynamic markers might be better markers of treatment effects than 6-MWD.

TRIAL REGISTRATION

The SERAPHIN study and its open-label extension are registered with ClinicalTrials.gov with identifiers NCT00660179 (https://www.clinicaltrials.gov/ct2/show/NCT00660179) and NCT00667823 (https://clinicaltrials.gov/ct2/show/NCT00667823) and with EudraCT with identifiers 2007-002440-14 (https://www.clinicaltrialsregister.eu/ctr-search/search?query=2007-002440-14) and 2007-003694-27 (https://www.clinicaltrialsregister.eu/ctr-search/search?query=2007-003694-27).

[Update pulmonary arterial hypertension : Definitions, diagnosis, therapy]

The term pulmonary arterial hypertension comprises a group of pulmonary vascular diseases of different etiologies that are characterized by similar precapillary vascular remodeling processes and result in exertional dyspnea and right heart insufficiency. The specific pharmacological treatment approach considers the risk of mortality and phenotypical properties and includes treatment with phosphodiesterase type 5 inhibitors, endothelin receptor antagonists and prostanoids, as well as with more novel substances, such as a soluble guanylyl cyclase stimulator and an oral prostacyclin receptor agonist. The prognosis of the disease is mainly determined by the right heart insufficiency for which there is currently no specific pharmacological treatment. Lung transplantation may be offered as a last option. This review provides an overview of the current European guidelines from 2015 and the recommendations of the Cologne Consensus Conference for pulmonary hypertension from 2016.

Steps forward in the treatment of pulmonary arterial hypertension: latest developments and clinical opportunities

Pulmonary arterial hypertension (PAH) is a chronic disease that results in narrowing of the small pre-capillary pulmonary arteries leading to elevation of pulmonary artery pressure and pulmonary vascular resistance, subsequent right ventricular failure, and if unchecked, death. Advances in the treatment of PAH over the last two decades have markedly improved survival. These improvements reflect a combination of changes in treatments, improved patient care strategies, and varying disease phenotypes in the PAH population. Currently approved therapies for PAH are directed at the recognized abnormalities within the pulmonary vasculature and include endothelin receptor antagonists, phosphodiesterase-5 inhibitors, soluble guanylate cyclase stimulators, and prostacyclin pathway agents. Most of these drugs have been approved on the basis of short-term trials that mainly demonstrated improvements in exercise capacity. More recently, long-term, event-driven trials of novel drugs have been performed, demonstrating new efficacy parameters. There have also been exciting advances in the understanding of right heart failure pathophysiology in PAH that have the potential to inspire the development of right ventricular targeted therapy and continued discoveries in the heterogeneity of disease and response to treatment has great potential for developing more 'personalized' therapeutic options. In this article, we review the current available data regarding the management of PAH, with an emphasis on the pharmacologic therapies and discussion of novel therapeutic directions for the treatment of this fatal disease.

Role of Cytochrome P450 2C8 in Drug Metabolism and Interactions

During the last 10-15 years, cytochrome P450 (CYP) 2C8 has emerged as an important drug-metabolizing enzyme. CYP2C8 is highly expressed in human liver and is known to metabolize more than 100 drugs. CYP2C8 substrate drugs include amodiaquine, cerivastatin, dasabuvir, enzalutamide, imatinib, loperamide, montelukast, paclitaxel, pioglitazone, repaglinide, and rosiglitazone, and the number is increasing. Similarly, many drugs have been identified as CYP2C8 inhibitors or inducers. In vivo, already a small dose of gemfibrozil, i.e., 10% of its therapeutic dose, is a strong, irreversible inhibitor of CYP2C8. Interestingly, recent findings indicate that the acyl-β-glucuronides of gemfibrozil and clopidogrel cause metabolism-dependent inactivation of CYP2C8, leading to a strong potential for drug interactions. Also several other glucuronide metabolites interact with CYP2C8 as substrates or inhibitors, suggesting that an interplay between CYP2C8 and glucuronides is common. Lack of fully selective and safe probe substrates, inhibitors, and inducers challenges execution and interpretation of drug-drug interaction studies in humans. Apart from drug-drug interactions, some CYP2C8 genetic variants are associated with altered CYP2C8 activity and exhibit significant interethnic frequency differences. Herein, we review the current knowledge on substrates, inhibitors, inducers, and pharmacogenetics of CYP2C8, as well as its role in clinically relevant drug interactions. In addition, implications for selection of CYP2C8 marker and perpetrator drugs to investigate CYP2C8-mediated drug metabolism and interactions in preclinical and clinical studies are discussed.

Pharmacokinetic study of ACT-132577 in rat plasma by ultra performance liquid chromatography-tandem mass spectrometry

It was reported that macitentan was metabolized predominantly by cytochrome P450 3A4, and ACT-132577, its pharmacologically active metabolite, is fivefold less potent at blocking ET receptors than macitentan. In this work, a sensitive and selective ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for determination of ACT-132577 in rat plasma was developed and validated. After addition of diazepam as an internal standard (IS), protein precipitation by acetonitrile was used to prepare samples. Chromatographic separation was achieved on a UPLC BEH C18 column (2.1 mm × 100 mm, 1.7 μm) with 0.2% formic acid and methanol as the mobile phase with gradient elution. An electrospray ionization source was applied and operated in positive ion mode; multiple reactions monitoring (MRM) mode was used for quantification using target fragment ions m/z 546.9→200.6 for ACT-132577, and m/z 285.1→193.1 for IS. Calibration plots were linear throughout the range 10-4000 ng/mL for ACT-132577 in rat plasma. Mean recovery of ACT-132577 in rat plasma ranged from 82.6% to 90.6%, matrix effect of ACT-132577 in rat plasma ranged from 101.4% to 115.2%. RSD of intra-day and inter-day precision were both less than 11%. The accuracy of the method ranged from 96.1% to 103.5%. The method was successfully applied to pharmacokinetic study of ACT-132577 after oral and intravenous administration of macitentan.