Comparison of Macitentan and Bosentan on Right Ventricular Remodeling in a Rat Model of Non-vasoreactive Pulmonary Hypertension

Dual ETA-ETB receptor antagonism improves metabolic syndrome-induced heart failure with preserved ejection fraction

BACKGROUND

Metabolic syndrome (MetS) is a multifaceted disease associated with heart failure (HF), which affects the vascular system. The endothelin (ET) system is a key player in MetS and HF; therefore, targets for ET receptors are of therapeutic interest.

OBJECTIVES

This study sought to evaluate the effects of macitentan, a dual endothelin receptor antagonist (ERA), in a rat model of MetS-induced heart failure with preserved ejection fraction (HFpEF).

METHODS

We assessed in 12-week-old Zucker fa/fa rats the effects of macitentan (10 mg/kg/day as a food additive for short-term/7- or long-term/90-day treatment) on right ventricular (RV) and left ventricular (LV) function/remodelling (MRI), RV and LV haemodynamics (catheterization) and RV and LV coronary function (myograph).

RESULTS

After 7- and 90-days, untreated Zucker fa/fa rats presented isolated LV diastolic dysfunction (illustrated by elevated LV end-diastolic pressure [EDP] and LV end-diastolic pressure-volume relationship [EDPVR] without changes in LV EDPVR). This was associated with increased collagen deposition and impaired endothelium-dependent coronary artery relaxation. Macitentan 7- and 90-day treatment significantly decreased blood pressure and prevented LV, RV and coronary dysfunctions and long-term treatment reduced LV collagen density. Moreover, 7- and 90-day macitentan treatment significantly reduced cardiac inflammation and reactive oxygen species (ROS) production.

CONCLUSIONS

Dual ERA macitentan improved both LV and RV diastolic dysfunction. This was associated with improved coronary vasodilation, diminished cardiac oxidative stress and improved blood composition. These results suggest that antagonizing the ET system with macitentan is a promising approach to treat HFpEF and its complications.

Improvement in idiopathic interstitial pneumonia by adding macitentan to a patient unresponsive to nintedanib

A 69-year-old woman was diagnosed with idiopathic interstitial pneumonia (IIP). The patient underwent a combination therapy of steroid therapy and intravenous cyclophosphamide, long-term oxygen therapy, and the initiation of Nintedanib. However, there was no improvement in IIP, and as a result, the activities of daily living also declined. As one of the various examinations conducted, the results of the right heart catheterization diagnosed the patient with mild pulmonary hypertension, and Macitentan therapy was initiated. The subsequent clinical course appeared to show an improvement in Idiopathic Interstitial Pneumonia (IIP) by adding Macitentan therapy to Nintedanib therapy.

Comprehensive review of potential drugs with anti-pulmonary fibrosis properties

Pulmonary fibrosis is a chronic and progressive lung disease characterized by the accumulation of scar tissue in the lungs, which leads to impaired lung function and reduced quality of life. The prognosis for idiopathic pulmonary fibrosis (IPF), which is the most common form of pulmonary fibrosis, is generally poor. The median survival for patients with IPF is estimated to be around 3-5 years from the time of diagnosis. Currently, there are two approved drugs (Pirfenidone and Nintedanib) for the treatment of IPF. However, Pirfenidone and Nintedanib are not able to reverse or cure pulmonary fibrosis. There is a need for new pharmacological interventions that can slow or halt disease progression and cure pulmonary fibrosis. This review aims to provide an updated overview of current and future drug interventions for idiopathic pulmonary fibrosis, and to summarize possible targets of potential anti-pulmonary fibrosis drugs, providing theoretical support for further clinical combination therapy or the development of new drugs.

A Bioinformatic Algorithm based on Pulmonary Endoarterial Biopsy for Targeted Pulmonary Arterial Hypertension Therapy

Background

Optimal pharmacological therapy for pulmonary arterial hypertension (PAH) remains unclear, as pathophysiological heterogeneity may affect therapeutic outcomes. A ranking methodology based on pulmonary vascular genetic expression analysis could assist in medication selection and potentially lead to improved prognosis.

Objective

To describe a bioinformatics approach for ranking currently approved pulmonary arterial antihypertensive agents based on gene expression data derived from percutaneous endoarterial biopsies in an animal model of pulmonary hypertension.

Methods

We created a chronic PAH model in Micro Yucatan female swine by surgical anastomosis of the left pulmonary artery to the descending aorta. A baseline catheterization, angiography and pulmonary endoarterial biopsy were performed. We obtained pulmonary vascular biopsy samples by passing a biopsy catheter through a long 8 French sheath, introduced via the carotid artery, into 2- to 3-mm peripheral pulmonary arteries. Serial procedures were performed on days 7, 21, 60, and 180 after surgical anastomosis. RNA microarray studies were performed on the biopsy samples.

Results

Utilizing the medical literature, we developed a list of PAH therapeutic agents, along with a tabulation of genes affected by these agents. The effect on gene expression from pharmacogenomic interactions was used to rank PAH medications at each time point. The ranking process allowed the identification of a theoretical optimum three-medication regimen.

Conclusion

We describe a new potential paradigm in the therapy for PAH, which would include endoarterial biopsy, molecular analysis and tailored pharmacological therapy for patients with PAH.

Macitentan in the Young-Mid-term Outcomes of Patients with Pulmonary Hypertensive Vascular Disease treated in a Pediatric Tertiary Care Center

BACKGROUND

Pulmonary hypertension (PH) is a severe hemodynamic condition with high morbidity and mortality. Approved targeted therapies are limited for pediatric subjects, and treatments are widely adopted from adult algorithms. Macitentan is a safe and effective drug used for adult PH, but data on pediatric patients are limited. In this prospective single-center study, we investigated mid- and long-term effects of macitentan in children with advanced pulmonary hypertensive vascular disease.

METHODS

Twenty-four patients were enrolled in the study for treatment with macitentan. Efficacy was determined by echo parameters and brain natriuretic peptide levels (BNP) at 3 months and 1 year. For detailed analysis, the entire cohort was subgrouped into patients with congenital heart disease-related PH (CHD-PH) and non-CHD-PH patients, respectively.

RESULTS

Mean age of the patients was 10.7 ± 7.6 years; median observation period was 36 months. Twenty of 24 patients were on additional sildenafil and/or prostacyclins. Two of 24 patients discontinued because of peripheral edema. Within the entire cohort, BNP levels and all echo measures such as right ventricular systolic pressure (RVSP), right ventricular end-diastolic diameter (RVED), tricuspid annular plane systolic excursion (TAPSE), pulmonary velocity time integral (VTI), and pulmonary artery acceleration time (PAAT) improved significantly after 3 months (p ≤ 0.01), whereas in the long term significant improvement persisted for BNP levels (-16%), VTI (+14%) and PAAT (+11%) (p < 0.05). By subgroup analysis, non-CHD PH patients showed significant improvements in BNP levels (-57%) and all echo measures (TAPSE +21%, VTI +13%, PAAT +37%, RVSP -24%, RVED -12%) at 3 months (p ≤ 0.01), whereas at 12 months, improvements persisted (p < 0.05) except for RVSP and RVED (nonsignificant). In CHD-PH patients, none of the measures changed (nonsignificant). 6-MWD (distance walked in 6 minutes) slightly increased but was not statistically evaluated.

CONCLUSION

Data presented herein account for the largest cohort of severely affected pediatric patients receiving macitentan. Overall, macitentan was safe and associated with significant beneficial effects and sustained positive signals after 1 year, albeit in the long term disease progression remains a major concern. Our data suggest limited efficacy in CHD-related PH, whereas favorable outcomes were mainly driven by improvements in patients with PH not related to CHD. Larger studies are needed to verify these preliminary results and to prove efficacy of this drug in different pediatric PH entities.

Disruption of GCN2 Pathway Aggravates Vascular and Parenchymal Remodeling during Pulmonary Fibrosis

Pulmonary fibrosis (PF) and pulmonary hypertension (PH) are chronic diseases of the pulmonary parenchyma and circulation, respectively, which may coexist, but underlying mechanisms remain elusive. Mutations in the GCN2 (general control nonderepressible 2) gene (EIF2AK4 [eukaryotic translation initiation factor 2 alpha kinase 4]) were recently associated with pulmonary veno-occlusive disease. The aim of this study is to explore the involvement of the GCN2/eIF2α (eukaryotic initiation factor 2α) pathway in the development of PH during PF, in both human disease and in a laboratory animal model. Lung tissue from patients with PF with or without PH was collected at the time of lung transplantation, and control tissue was obtained from tumor resection surgery. Experimental lung disease was induced in either male wild-type or EIF2AK4-mutated Sprague-Dawley rats, randomly receiving a single intratracheal instillation of bleomycin or saline. Hemodynamic studies and organ collection were performed 3 weeks after instillation. Only significant results (P < 0.05) are presented. In PF lung tissue, GCN2 protein expression was decreased compared with control tissue. GCN2 expression was reduced in CD31+ endothelial cells. In line with human data, GCN2 protein expression was decreased in the lung of bleomycin rats compared with saline. EIF2AK4-mutated rats treated with bleomycin showed increased parenchymal fibrosis (hydroxyproline concentrations) and vascular remodeling (media wall thickness) as well as increased right ventricular systolic pressure compared with wild-type animals. Our data show that GCN2 is dysregulated in both humans and in an animal model of combined PF and PH. The possibility of a causative implication of GCN2 dysregulation in PF and/or PH development should be further studied.

Bleomycin-induced lung injury: Revisiting an old tool to model group III PH associated with pulmonary fibrosis

Pulmonary hypertension (PH) is a chronic disorder of the pulmonary circulation that often associates with other respiratory diseases (i.e., group III PH), leading to worsened symptoms and prognosis, notably when combined with interstitial lung diseases such as pulmonary fibrosis (PF). PH may lead to right ventricular (RV) failure, which accounts for a substantial part of the mortality in chronic lung disease patients. The disappointing results of pulmonary arterial hypertension (PAH)-related therapies in patients with PF emphasize the need to better understand the pathophysiologic mechanisms that drive PH development and progression in this specific setting. In this work, we validated an animal model of group III PH associated with PF (PH-PF), by using bleomycin (BM) intratracheal instillation and characterizing the nature of induced lung and vascular remodeling, including the influence on RV structure and function. To our knowledge, this is the first work describing this dose of BM in Sprague Dawley rats and the effects upon the heart and lungs, using different techniques such as echocardiography, heart catheterization, and histology. Our data shows the successful implementation of a rat model that mimics combined PF-PH, with most features seen in the equivalent human disease, such as lung and arterial remodeling, increased mPAP and RV dysfunction.

Macitentan attenuates cardiovascular remodelling in infant rats with chronic lung disease

Background

Cardiovascular impairment contributes to increased mortality in preterm infants with chronic lung disease. Macitentan, an endothelin-1 receptor antagonist, has the potential to attenuate pulmonary and cardiovascular remodelling.

Methods

In a prospective randomized placebo-controlled intervention trial, Sprague–Dawley rats were exposed to 0.21 or 1.0 fraction of inspired oxygen (FiO2) for 19 postnatal days. Rats were treated via gavage with placebo or macitentan from days of life 5 to 19. Alveoli, pulmonary vessels, α-smooth muscle actin content in pulmonary arterioles, size of cardiomyocytes, right to left ventricular wall diameter ratio, and endothelin-1 plasma concentrations were assessed.

Results

FiO2 1.0 induced typical features of chronic lung disease with significant alveolar enlargement (p = 0.012), alveolar (p = 0.048) and pulmonary vessel rarefaction (p = 0.024), higher α-smooth muscle actin content in pulmonary arterioles (p = 0.009), higher right to left ventricular wall diameter ratio (p = 0.02), and larger cardiomyocyte cross-sectional area (p < 0.001). Macitentan treatment significantly increased pulmonary vessel count (p = 0.004) and decreased right to left ventricular wall diameter ratios (p = 0.002). Endothelin-1 plasma concentrations were higher compared to placebo (p = 0.015). Alveolar number and size, α-smooth muscle actin, and the cardiomyocyte cross-sectional area remained unchanged (all p > 0.05).

Conclusion

The endothelin-1 receptor antagonist macitentan attenuated cardiovascular remodelling in an infant rat model for preterm chronic lung disease. This study underscores the potential of macitentan to reduce cardiovascular morbidity in preterm infants with chronic lung disease.

Cardioprotective effects of bosentan in 5-fluorouracil-induced cardiotoxicity

5-fluorouracil (5-FU) is a widely used chemotherapeutic agent but cardiotoxicity challenges its clinical usefulness. Thus, searching for more cardioprotective drugs is highly required to prevent the accompanied cardiac hazards. Up to date, the different mechanisms involved in 5-FU cardiotoxicity are still unclear and there is no evaluation of bosentan's role in controlling these cardiac complications. This forced us to deeply study and evaluate the possible cardiopreserving properties of bosentan and different mechanisms involved in mediating it. 32 Wistar albino rats were included in our experiment and induction of cardiotoxicity was performed via administration of 5-FU (150 mg/kg) on 5th day of the experiment by intraperitoneal (i.p.) injection with or without co-administration of bosentan (50 mg/kg/day) orally for 7days. Our data revealed that 5-FU could induce cardiotoxicity which was detected as significant increases of troponin I, lactate dehydrogenase (LDH), creatine kinase- MB (CK-MB), endothelin receptors, malondialdehyde (MDA), toll like receptor4 (TLR4), myeloid differentiation primary response 88 (MyD88), nuclear factor kappa B (NFκB), and caspase 3 levels. However, there is marked decrease in endothelial nitric oxide synthase (eNOS), reduced glutathione (GSH) and total antioxidant capacity (TAC). In addition, the histopathological examination showed severe toxic features of cardiac injury. Interestingly, co-administration of bosentan could ameliorate 5-FU-induced cardiotoxicity via improving the detected biochemical and histopathological changes besides modulation of TLR4/MyD88/NFκB signaling pathway, eNOS, and endothelin receptors. Bosentan had a significant cardioprotective effect against 5-FU induced cardiac damage. This effect may be attributed to its ability to inhibit endothelin receptors, stimulates eNOS, anti-oxidant, anti-inflammatory, anti-apoptotic properties with modulation of TLR4/MyD88/NFκB signaling pathway.

Novel Targets in a High-Altitude Pulmonary Hypertension Rat Model Based on RNA-seq and Proteomics

High-altitude pulmonary hypertension (HAPH) is a complication arising from an inability to acclimatize to high altitude and is associated with high morbidity and mortality. We aimed to analyze the effects of macitentan, selexipag, riociguat, and reoxygenation on HAPH, and to screen possible targets of these treatments for future drug screening. Rats were subjected to hypobaric hypoxia for 35 days to induce HAPH, and treated with vehicle or selexipag, macitentan, riociguat, or with reoxygenation, from days 21 to 35. Selexipag, macitentan, and reoxygenation prevented an increase in mean pulmonary artery pressure and hypoxia-induced right ventricular hypertrophy, compared to the vehicle. Riociguat had little effect. RNA-seq and proteomics revealed strong correlations between responses to the three drugs, which had almost identical effects. GO-enrichment revealed that the differentially expressed genes included those involved in metabolic regulation, transcription, and translation. Various molecular pathways were annotated. Selexipag, macitentan, and reoxygenation ameliorated HAPH. Serpina1, Cryz, and Cmc1 were identified, via multi-omics screening, as key genes involved in HAPH. These findings provide new insights into the targeted drug mechanisms in HAPH.

The REPAIR Study: Effects of Macitentan on RV Structure and Function in Pulmonary Arterial Hypertension

OBJECTIVES

The REPAIR (Right vEntricular remodeling in Pulmonary ArterIal hypeRtension) study evaluated the effect of macitentan on right ventricular (RV) and hemodynamic outcomes in patients with pulmonary arterial hypertension (PAH), using cardiac magnetic resonance (CMR) and right heart catheterization (RHC).

BACKGROUND

RV failure is the primary cause of death in PAH. CMR is regarded as the most accurate noninvasive method for assessing RV function and remodeling and CMR measures of RV function and structure are strongly prognostic for survival in patients with PAH. Despite this, CMR is not routinely used in PAH clinical trials.

METHODS

REPAIR was a 52-week, open-label, single-arm, multicenter, phase 4 study evaluating the effect of macitentan 10 mg, with or without phosphodiesterase type-5 inhibition, on RV remodeling and function and cardiopulmonary hemodynamics. Primary endpoints were change from baseline to week 26 in RV stroke volume, determined by CMR; and pulmonary vascular resistance, determined by RHC. Efficacy measures were assessed for all patients with baseline and week 26 data for both primary endpoints.

RESULTS

At a prespecified interim analysis in 42 patients, both primary endpoints were met, enrollment was stopped, and the study was declared positive. At final analysis (n = 71), RV stroke volume increased by 12 mL (96% confidence level: 8.4-15.6 mL; P < 0.0001) and pulmonary vascular resistance decreased by 38% (99% confidence level: 31%-44%; P < 0.0001) at week 26. Significant positive changes were also observed in secondary and exploratory CMR (RV and left ventricular), hemodynamic, and functional endpoints at week 26. Improvements in CMR RV and left ventricular variables and functional parameters were maintained at week 52. Safety (n = 87) was consistent with previous clinical trials.

CONCLUSIONS

In the context of this study, macitentan treatment in patients with PAH resulted in significant and clinically-relevant improvements in RV function and structure and cardiopulmonary hemodynamics. At 52 weeks, improvements in RV function and structure were sustained. (REPAIR: Right vEntricular remodeling in Pulmonary ArterIal hypeRtension [REPAIR]; NCT02310672).

Sunitinib-induced cardiac hypertrophy and the endothelin axis

Anti-angiogenics drugs in clinical use for cancer treatment induce cardiotoxic side effects. The endothelin axis is involved in hypertension and cardiac remodelling, and addition of an endothelin receptor antagonist to the anti-angiogenic sunitinib was shown to reduce cardiotoxicity of sunitinib in mice. Here, we explored further the antidote effect of the endothelin receptor antagonist macitentan in sunitinib-treated animals on cardiac remodeling.

Methods: Tumor-bearing mice treated per os daily by sunitinib or vehicle were imaged before and after 1, 3 and 6 weeks of treatment by positron emission tomography using [¹⁸F]fluorodeoxyglucose and by echocardiography. Non-tumor-bearing animals were randomly assigned to be treated per os daily by vehicle or sunitinib or macitentan or sunitinib+macitentan, and imaged by echocardiography after 5 weeks. Hearts were harvested for histology and molecular analysis at the end of in vivo exploration.

Results: Sunitinib treatment increases left ventricular mass and ejection fraction and induces cardiac fibrosis. Sunitinib also induces an early increase in cardiac uptake of [¹⁸F]fluorodeoxyglucose, which is significantly correlated with increased left ventricular mass at the end of treatment. Co-administration of macitentan prevents sunitinib-induced hypertension, increase in ejection fraction and cardiac fibrosis, but fails to prevent increase of the left ventricular mass.

Conclusion: Early metabolic changes predict sunitinib-induced cardiac remodeling. Endothelin blockade can prevent some but not all cardiotoxic side-effects of sunitinib, in particular left ventricle hypertrophy that appears to be induced by sunitinib through an endothelin-independent mechanism.

Strategies for the management of pulmonary arterial hypertension in patients with congenital heart disease

Background

Pulmonary hypertension (PH) is commonly seen in adults who have congenital heart disease (CHD). Therapy is available for pulmonary arterial hypertension (PAH) and has greatly benefitted many patients with PAH related to CHD (PAH-CHD) over the last 15 years, with evidence of improved quality of life and prognosis in those with Eisenmenger syndrome and repaired PAH-CHD.

In this review, we describe the standard management and advanced therapies for PAH, which are available in specialist PH centres around the UK and Ireland, and how these are used in PAH-CHD. Decisions around the choice of therapy are governed by commissioning and available evidence.

Conclusion

We explain the different pathways for action and the variety of medications now at our disposal to help this important group of patients.

Long-term treatment of pulmonary arterial hypertension with macitentan in Japanese patients

Objective: Macitentan, a novel dual endothelin receptor antagonist, was approved for the treatment of pulmonary arterial hypertension (PAH) in Japan. However, long-term effects in Japanese patients of macitentan are currently unavailable. This study sought to assess the long-term efficacy and safety of macitentan in Japanese patients with PAH.Methods: In this multicenter, open-label, clinical extension study (JapicCTI-121986), efficacy was evaluated based on the change from baseline at 24, 48, 72, 96 and 120-week in the 6-minute walk distance (6MWD), World Health Organization (WHO) functional class, and serum N-terminal pro-brain natriuretic peptide (NT-pro-BNP) levels. In addition, the time to a hospitalization related to PAH and a morbidity/mortality event was determined. As for safety, the incidence of adverse events and changes in laboratory data and vital signs were assessed.Results: Macitentan was administered at a once-daily dose of 10 mg in 30 PAH patients with a median treatment period of 2.4 years (range, 229-1037 days). The improvements in 6MWD, WHO functional class and NT-pro-BNP at week 24 were maintained throughout the long-term follow-up. Hospitalization related to PAH occurred in 2 patients. Levels of liver enzyme and hemoglobin remained unchanged throughout the study period.Conclusions: This study suggests that the long-term use of macitentan is well tolerated and effective in Japanese patients with PAH. We concluded that macitentan can be a possible approach to reduce morbidity/mortality in Japanese PAH patients.

Clinical efficacy and safety of switch from bosentan to macitentan in children and young adults with pulmonary arterial hypertension: extended study results

BACKGROUND

Macitentan is an orally active, potent, dual endothelin receptor antagonist and is the only registered treatment for pulmonary arterial hypertension that significantly reduced morbidity and mortality in a long-term study.

AIM

We have recently reported that switch from bosentan to macitentan significantly improved exercise capacity in children and young adults with pulmonary arterial hypertension in a 24-week prospective study and well tolerated without adverse events. We now aimed to evaluate clinical efficacy, safety of switch in a larger patient population, in a 24-month prospective study.

METHODS

This is a single-institution, 24-month prospective study. Patients ≥12 years with idiopathic/heritable, pulmonary arterial hypertension, or related to CHD or residual pulmonary arterial hypertension due to repaired congenital systemic-to-pulmonary shunts and on bosentan treatment were included. Concomitant treatment with oral phosphodiesterase type 5 inhibitors/inhaled prostanoids was allowed. Outcome measures included change from baseline to 24 months, in the 6-minute walk distance, functional class, oxygen saturation at rest/after walk distance test, and natriuretic peptide levels. Safety end points included adverse events, laboratory abnormalities.

RESULTS

Twenty-seven patients (19 adults/8 children, mean age: 21.1 ± 6.3 years (12-36), weight: 53.1 ± 15.7 kgs (26-87)) were included. Mean duration of macitentan treatment: 22.3 ± 3.9 months (9-24). Six-minute walk distance significantly improved from baseline (mean: 458 ± 79 m (300-620)) at 6 months (mean: 501 ± 73 m (325-616) + 43 m) (p < 0.05), at 12 months (mean: 514 ± 82 m (330-626) + 56 m) (p < 0.05), and at 24 months (mean: 532 ± 85 m (330-682) + 74 m) (p < 0.05). We observed a significant improvement during the first 6 months but no incremental improvement after 6 months (p > 0.05). Macitentan did not significantly change functional class, oxygen saturation, and natriuretic levels (p > 0.05). None of the patients had anaemia, hepatotoxicity, and peripheral edema.

CONCLUSIONS

Our study is the first study which showed that switch from bosentan to macitentan improved exercise capacity in children and young adults with pulmonary arterial hypertension significantly in the first 6 months and compared to baseline in 24 months and well tolerated without adverse events.

Pharmacological characterization of a highly selective Rho kinase (ROCK) inhibitor and its therapeutic effects in experimental pulmonary hypertension

Studies on the role of Rho-associated protein kinase (ROCK) in experimental pulmonary artery hypertension (PAH) relies mainly on the use of pharmacological inhibitors. However, interpreting these data is hampered by the lack of specificity of commonly utilized inhibitors. To fill this gap, we have selected and characterized a novel ROCK inhibitor, Compound 3, previously described in a patent. Inhibitory potency of Compound 3 against enzymatic activity of ROCK-1 and 2 (IC₅₀ = 10 ± 3.1 and 7.8 ± 0.5 nM, respectively) was accompanied by a strong vasodilating effect in phenylephrine pre-contracted isolated rat pulmonary artery rings (IC₅₀ = 51.7 ± 9.1 nM) as well as in aortic rings (IC₅₀ = 45.5 ± 1.1 nM). Compound 3 showed a remarkable selectivity towards ROCK 1 and 2 when tested against a large panel (>400) of human kinases. A partial explanation for its selectivity is provided from docking simulations within ROCK-1. Pharmacokinetic studies showed that Compound 3 is suitable for a twice daily administration without significant accumulation upon repeated dosing. In rats with monocrotaline (MCT)-induced pulmonary hypertension, therapy with Compound 3, (1 and 3 mg/kg, s.c., b.i.d.), started 14 days after induction of the disease, attenuated right ventricle systolic pressure (RVSP) increase. Morphometric histological analysis showed that Compound 3, at both doses, counteracted MCT-induced medial thickening of lung distal arterioles with an effect comparable to macitentan (10 mg/kg, p.o., q.d.). Compound 3 is a potent and highly selective ROCK inhibitor that ameliorates hemodynamic parameters and counteracts pulmonary vascular remodeling in experimental PAH.

Correlation of cardiomyocyte apoptosis with duration of hypertension, severity of hypertension and caspase-3 expression in hypertensive rats

Correlation of cardiomyocyte apoptosis with duration of hypertension, severity of hypertension and caspase-3 expression in hypertensive rats was analyzed. Sixty male Sprague-Dawley (SD) rats were selected and randomly divided into the observation group (n=30) and control group (n=30), and the rat models of hypertension were established by virtue of transverse aortic constriction (TAC). The rats in the two groups were further divided into the 7-day subgroup (n=10), 14-day subgroup (n=10) and 28-day subgroup (n=10), respectively according to their survival time after TAC. The blood pressure values of the rats in each group were measured through intubation of carotid artery to calculate the mean arterial pressure (MAP). The conditions of cardiomyocyte apoptosis were detected using terminal dexynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay. Enzyme-linked immunosorbent assay (ELISA) was applied to measure the expression of caspase-3 in the myocardial tissues, and correlation analysis was performed. The MAPs in 7-, 14- and 28-day subgroups of the observation group were significantly higher than those in the corresponding subgroups of the control group (P<0.05). The 7-, 14- and 28-day subgroups of the observation group had remarkably elevated myocardial caspase-3 expression levels compared with the subgroups of the control group (P<0.05). The apoptosis rates of myocardial cells in the three subgroups of the observation group were obviously higher than those in the corresponding subgroups of the control group (P<0.05). Pearson's correlation analysis indicated that the cardiomyocyte apoptosis rate of hypertensive rats was positively correlated with the duration of hypertension, severity of hypertension and caspase-3 expression (P<0.05). Hypertension can induce apoptosis of myocardial cells, and the apoptosis becomes more serious with the constantly elevated level and prolonged duration of hypertension. In addition, the activity of caspase-3 has a close correlation with cardiomyocyte apoptosis.

Highlights from the ERS International Congress 2018: Assembly 13 - Pulmonary Vascular Diseases

The 2018 European Respiratory Society (ERS) International Congress in Paris, France, highlighted the subject of pulmonary vascular disease (PVD). 2018 was an exciting year for the PVD community as it was the first ERS International Congress since the formation of Assembly 13, which is dedicated to PVD, pulmonary embolism and the right ventricle. This article aims to summarise the high-quality studies presented at the 2018 Congress into four subject areas: the use of risk stratification in pulmonary arterial hypertension, the molecular mechanisms and treatment of pulmonary hypertension (PH), understanding and improving the right ventricle in PH, and finally, advances in the field of acute pulmonary embolus.

The Role of G Protein-Coupled Receptors in the Right Ventricle in Pulmonary Hypertension

Pressure overload of the right ventricle (RV) in pulmonary arterial hypertension (PAH) leads to RV remodeling and failure, an important determinant of outcome in patients with PAH. Several G protein-coupled receptors (GPCRs) are differentially regulated in the RV myocardium, contributing to the pathogenesis of RV adverse remodeling and dysfunction. Many pharmacological agents that target GPCRs have been demonstrated to result in beneficial effects on left ventricular (LV) failure, such as beta-adrenergic receptor and angiotensin receptor antagonists. However, the role of such drugs on RV remodeling and performance is not known at this time. Moreover, many of these same receptors are also expressed in the pulmonary vasculature, which could result in complex effects in PAH. This manuscript reviews the role of GPCRs in the RV remodeling and dysfunction and discusses activating and blocking GPCR signaling to potentially attenuate remodeling while promoting improvements of RV function in PAH.

Macitentan reduces progression of TGF-β1-induced pulmonary fibrosis and pulmonary hypertension

Idiopathic pulmonary fibrosis (IPF) is a progressive disease with an unknown cause. Two drugs, nintedanib and pirfenidone, have been shown to slow, but not stop, disease progression. Pulmonary hypertension (PH) is a frequent complication in IPF patients and is associated with poor prognosis. Macitentan is a dual endothelin receptor antagonist that is approved for pulmonary arterial hypertension treatment. We hypothesised that using macitentan to treat animals with pulmonary fibrosis induced by adenoviral vector encoding biologically active transforming growth factor-β1 (AdTGF-β1) would improve the PH caused by chronic lung disease and would limit the progression of fibrosis.Rats (Sprague Dawley) which received AdTGF-β1 were treated by daily gavage of macitentan (100 mg·kg^-1·day^-1), pirfenidone (0.5% food admix) or a combination from day 14 to day 28. Pulmonary artery pressure (PAP) was measured before the rats were killed, and fibrosis was subsequently evaluated by morphometric measurements and hydroxyproline analysis.AdTGF-β1 induced pulmonary fibrosis associated with significant PH. Macitentan reduced the increase in PAP and both macitentan and pirfenidone stopped fibrosis progression from day 14 to day 28. Macitentan protected endothelial cells from myofibroblast differentiation and apoptosis whereas pirfenidone only protected against fibroblast-to-myofibroblast differentiation. Both drugs induced apoptosis of differentiated myofibroblasts in vitro and in vivoOur results demonstrate that dual endothelin receptor antagonism was effective in both PH and lung fibrosis whereas pirfenidone only affected fibrosis.

Hemodynamic and Histopathologic Benefits of Early Treatment with Macitentan in a Rat Model of Pulmonary Arterial Hypertension

BACKGROUND AND OBJECTIVES

Macitentan (MAC) reduces morbidity and mortality among advanced-stage pulmonary arterial hypertension (PAH) patients. However, data regarding the histopathologic and hemodynamic benefits of MAC treatment at an early stage of PAH is lacking.

METHODS

One week after monocrotaline (MCT) injection, rats were randomly assigned to MAC (n=16), MAC combined with sildenafil (SIL) (MAC+SIL, n=16), or normal saline (MCT, n=16). Twelve sham rats (Sham) were included for comparison. Right ventricular (RV) systolic function was assessed via echocardiography as the RV fractional area change (RV-FAC). An invasive pressure-volume analysis using a Millar conductance catheter was performed 7 weeks after MCT injection. Rats were subsequently euthanized for histopathologic analysis.

RESULTS

RV-right atrial pressure gradient on echocardiography was significantly increased 3 weeks after MCT injection, but was maintained in the Sham. RV-FAC was less deteriorated in the MAC, compared to that in the MCT (44±3% vs. 25±7%, p<0.05), and the co-administration of SIL showed no additional benefit (45±8%, p>0.05 vs. the MAC). On invasive hemodynamic analyses, RV end-systolic (196±78 μL) and end-diastolic volumes (310±86 μL), pulmonary artery systolic pressure (89±7.2 mmHg), and end-systolic pressure-volume relationship (-254±25.1) were significantly worse in the MCT vs. in the MAC (101±45 μL, 235±55 μL, 40±10.5 mmHg, and -145±42.1, respectively) and MAC+SIL (109±47 μL, 242±46 μL, 38±9.2 mmHg, and -151±39.2, respectively) (all p<0.05). However, the MAC and MAC+SIL did not differ (all p>0.05). On histopathology, both RV and lung fibrosis were significantly reduced in the MAC and MAC+SIL vs. in the MCT (all p<0.05); the 2 treatment groups did not differ.

CONCLUSIONS

MAC treatment at an earlier stage significantly attenuated experimental PAH progression hemodynamically and histopathologically.

Pulmonary hypertension in congenital heart disease

Pulmonary hypertension is defined as a mean pulmonary arterial pressure ≥25 mmHg. We focus on its relevance in congenital heart disease, reviewing pathophysiology, diagnosis and management. Pulmonary hypertension is a relatively common complication of congenital heart disease, with adult prevalence between 5 and 10%. A multifactorial cause is recognized, relating to the size and nature of cardiac defect as well as environmental and genetic factors. More complex disease is increasingly recognized rather than pure Eisenmenger complex. Remodeling of the pulmonary vascular bed causes increased pulmonary vascular resistance diagnosed by a collection of investigations including echocardiography, exercise testing, cardiac catheterization, MRI and CT scanning. Management employs disease-modifying medications which are now used with increasing benefit.

ECG Markers of Hemodynamic Improvement in Patients with Pulmonary Hypertension

Introduction

Several diagnostic tests have been recommended for risk assessment in pulmonary hypertension (PH), but the role of electrocardiography (ECG) in monitoring of PH patients has not been yet established. Therefore the aim of the study was to evaluate which ECG patterns characteristic for pulmonary hypertension can predict hemodynamic improvement in patients treated with targeted therapies.

Methods

Consecutive patients with pulmonary arterial hypertension (PAH) or chronic thromboembolic pulmonary hypertension (CTEPH) were eligible to be included if they had had performed two consecutive right heart catheterization (RHC) procedures before and after starting of targeted therapies. Patients were followed up from June 2009 to July 2017. ECG patterns of right ventricular hypertrophy according to American College of Cardiology Foundation were assessed.

Results

We enrolled 80 patients with PAH and 11 patients with inoperable CTEPH. The follow-up RHC was performed within 12.6 ± 10.0 months after starting therapy. Based on median change of pulmonary vascular resistance, we divided our patients into two subgroups: with and without significant hemodynamic improvement. R_V1, max⁡R_V1,2 + max⁡S_I,aVL − S_V1, and P_II improved along with the improvement of hemodynamic parameters including PVR. They predicted hemodynamic improvement with similarly good accuracy as shown in ROC analysis: R_V1 (AUC: 0.75; 95% CI: 0.63–0.84), P_II (AUC: 0.67, 95% CI: 0.56–0.77), and max⁡R_V1,2 + max⁡S_I,aVL − S_V1 (0.73; 95% CI: 0.63–0.82). In Cox regression only change in R_V1 remained significant mortality predictor (HR: 1.12, 95% CI: 1.01–1.24).

Conclusion

Electrocardiogram may be useful in predicting hemodynamic effects of targeted therapy in precapillary pulmonary hypertension. Decrease of R_V1, max⁡R_V1,2 + max⁡S_I,aVL − S_V1, and P_II corresponds with hemodynamic improvement after treatment. Of these changes a decrease of R wave amplitude in V₁ is associated with better survival.

Impaired Pulmonary Arterial Vasoconstriction and Nitric Oxide-Mediated Relaxation Underlie Severe Pulmonary Hypertension in the Sugen-Hypoxia Rat Model

Pulmonary vasoreactivity could determine the responsiveness to vasodilators and, in turn, the prognosis of pulmonary hypertension (PH). We hypothesized that pulmonary vasoreactivity is impaired, and we examined the underlying mechanisms in the Sugen-hypoxia rat model of severe PH. Male Sprague-Dawley rats were injected with Sugen (20 mg/kg s.c.) and exposed to hypoxia (9% O2) for 3 weeks, followed by 4 weeks in normoxia (Su/Hx), or treated with Sugen alone (Su) or hypoxia alone (Hx) or neither (Nx). After hemodynamic measurements, the heart was assessed for right ventricular hypertrophy (Fulton's index); the pulmonary artery, aorta, and mesenteric arteries were isolated for vascular function studies; and contractile markers were measured in pulmonary arteries using quantitative polymerase chain reaction (PCR). Other rats were used for morphometric analysis of pulmonary vascular remodeling. Right ventricular systolic pressure and Fulton's index were higher in Su/Hx versus Su, Hx, and Nx rats. Pulmonary vascular remodeling was more prominent in Su/Hx versus Nx rats. In pulmonary artery rings, contraction to high KCl (96 mM) was less in Su/Hx versus Nx and Su, and phenylephrine-induced contraction was reduced in Su/Hx versus Nx, Hx, and Su. Acetylcholine (ACh)-induced relaxation was less in Su/Hx versus Nx and Hx, suggesting reduced endothelium-dependent vasodilation. ACh relaxation was inhibited by nitric oxide synthase (NOS) and guanylate cyclase blockade in all groups, suggesting a role of the NO-cGMP pathway. Nitrate/nitrite production in response to ACh was less in Su/Hx versus Nx, supporting reduced endothelial NO production. Sodium nitroprusside (10-8 M) caused less relaxation in Su/Hx versus Nx, Hx, and Su, suggesting a decreased responsiveness of vascular smooth muscle (VSM) to vasodilators. Neither contraction nor relaxation differed in the aorta or mesenteric arteries of all groups. PCR analysis showed decreased expression of contractile markers in pulmonary artery of Su/Hx versus Nx. The reduced responsiveness to vasoconstrictors and NO-mediated vasodilation in the pulmonary, but not systemic, vessels may be an underlying mechanism of severe PH in Su/Hx rats and appears to involve attenuation of the NO relaxation pathway and a switch of pulmonary VSM cells to a synthetic less reactive phenotype.

Macitentan in Pulmonary Arterial Hypertension: A Focus on Combination Therapy in the SERAPHIN Trial

SERAPHIN was a double-blind, placebo-controlled, event-driven phase III trial that evaluated the effects of long-term treatment with macitentan, an oral endothelin receptor antagonist, in patients with pulmonary arterial hypertension (PAH). The majority of patients were receiving PAH therapy at enrollment, providing the opportunity to evaluate the efficacy and safety of macitentan in combination with other PAH therapies (predominantly phosphodiesterase type 5 inhibitors [PDE-5i]). In patients receiving background therapy, macitentan reduced the risk of morbidity/mortality by 38% compared with placebo (hazard ratio [HR] 0.62; 95% confidence level [CL] 0.43-0.89; p = 0.009). Furthermore, patients receiving macitentan and background therapy had a 37% reduction in the risk of being hospitalized for PAH (HR 0.63; 95% CL 0.41-0.96) compared with patients receiving background therapy only (placebo arm). Macitentan treatment in combination with background therapy was also associated with improvements in exercise capacity, functional class, cardiopulmonary hemodynamics, and health-related quality of life compared with background therapy alone. The safety profile of macitentan as part of a combination therapy regimen was consistent with that of macitentan in the overall SERAPHIN population. The SERAPHIN study has provided evidence that combination therapy with macitentan and a PDE-5i is effective and well tolerated in the management of PAH. Based on these data, and those from subsequent long-term trials, combination therapy is increasingly recognized as an important treatment option for improving long-term outcomes in PAH.

CLINICAL TRIAL REGISTRATION NUMBER

NCT00660179.

Dual ETA/ETB blockade with macitentan improves both vascular remodeling and angiogenesis in pulmonary arterial hypertension

Dysregulated metabolism and rarefaction of the capillary network play a critical role in pulmonary arterial hypertension (PAH) etiology. They are associated with a decrease in perfusion of the lungs, skeletal muscles, and right ventricle (RV). Previous studies suggested that endothelin-1 (ET-1) modulates both metabolism and angiogenesis. We hypothesized that dual ET_A/ET_B receptors blockade improves PAH by improving cell metabolism and promoting angiogenesis. Five weeks after disease induction, Sugen/hypoxic rats presented severe PAH with pulmonary artery (PA) remodeling, RV hypertrophy and capillary rarefaction in the lungs, RV, and skeletal muscles (microCT angiogram, lectin perfusion, CD31 staining). Two-week treatment with dual ET_A/ET_B receptors antagonist macitentan (30 mg/kg/d) significantly improved pulmonary hemodynamics, PA vascular remodeling, and RV function and hypertrophy compared to vehicle-treated animals (all P = 0.05). Moreover, macitentan markedly increased lung, RV and quadriceps perfusion, and microvascular density (all P = 0.05). In vitro, these effects were associated with increases in oxidative phosphorylation (oxPhox) and markedly reduced cell proliferation of PAH-PA smooth muscle cells (PASMCs) treated with macitentan without affecting apoptosis. While macitentan did not affect oxPhox, proliferation, and apoptosis of PAH-PA endothelial cells (PAECs), it significantly improved their angiogenic capacity (tube formation assay). Exposure of control PASMC and PAEC to ET-1 fully mimicked the PAH cells phenotype, thus confirming that ET-1 is implicated in both metabolism and angiogenesis abnormalities in PAH. Dual ET_A/ET_B receptor blockade improved the metabolic changes involved in PAH-PASMCs' proliferation and the angiogenic capacity of PAH-PAEC leading to an increased capillary density in lungs, RV, and skeletal muscles.

Macitentan: A Review in Pulmonary Arterial Hypertension

Macitentan (Opsumit^®) is an orally active, potent, dual endothelin (ET) receptor antagonist that is indicated for the treatment of pulmonary arterial hypertension (PAH). In the pivotal SERAPHIN trial in patients aged ≥12 years with PAH, the risk of first PAH-related event or all-cause death (primary composite endpoint) was significantly reduced by 45 % with oral macitentan 10 mg once daily versus placebo. Macitentan significantly reduced the risk of the primary composite endpoint across various patient subgroups. The risk of all-cause hospitalization and PAH-related hospitalization was also significantly reduced by macitentan, according to post hoc analysis. Macitentan was generally well tolerated in SERAPHIN. In conclusion, macitentan is an important option for the treatment of PAH.

Endothelin research and the discovery of macitentan for the treatment of pulmonary arterial hypertension

Endothelin receptor antagonists (ERAs) are used for the treatment of pulmonary arterial hypertension (PAH). Macitentan, a dual (ETA+ETB) ERA approved for the long-term treatment of PAH, was discovered through a tailored research program aimed at improving efficacy and safety over the existing ERAs. The goal of improved efficacy was based on the understanding that not only the ETA receptor but also the ETB receptor contributed to the hemodynamic and structural changes induced by endothelin-1 (ET-1) in pathological conditions and on the predefined requirements for optimal tissue penetration and binding kinetics of the antagonist. The goal of improved safety was based on the discovery of the role of ETB receptors in vascular permeability and vasopressin release and on the elucidation of the mechanism by which bosentan (the first approved oral dual ETA/ETB ERA) caused liver enzyme changes. Our intention was to design a molecule that would block ETA and ETB receptors optimally and would not interfere with bile salt elimination. This review takes us through the drug discovery journey that led to the discovery, development, and registration of macitentan.

Efficacy and Safety of a Novel Endothelin Receptor Antagonist, Macitentan, in Japanese Patients With Pulmonary Arterial Hypertension

BACKGROUND

Macitentan is a novel, dual endothelin receptor antagonist with sustained receptor binding, used for the long-term treatment of pulmonary arterial hypertension (PAH). In the present study, we assessed the efficacy and safety of macitentan in Japanese patients with PAH.

METHODS AND RESULTS

Macitentan was administered at a once-daily dose of 10 mg in 30 patients. The primary endpoint was change in pulmonary vascular resistance (PVR) from baseline to week 24. Change to week 24 in the other hemodynamic parameters, 6-min walk distance (6MWD), World Health Organization (WHO) functional class, and plasmaN-terminal pro-brain natriuretic peptide (NT-pro-BNP), as well as time to clinical deterioration up to week 52 were also assessed as secondary endpoints. In the 28 patients on per-protocol analysis, PVR decreased from 667±293 to 417±214 dyn·sec·cm(-5)(P<0.0001). 6MWD increased from 427±128 to 494±116 m (P<0.0001). WHO functional class improved in 13 patients (46.4%) and was maintained in 15 patients (53.6%), and NT-pro-BNP was reduced by 18% (P<0.0001). The favorable treatment effect on PVR was apparent regardless of concomitant therapy for PAH.

CONCLUSIONS

Macitentan was efficacious and well tolerated and improved the hemodynamic parameters, exercise capacity, symptoms, and clinical biomarkers in Japanese PAH patients. Macitentan can be a valuable therapeutic option for Japanese patients with PAH. (

TRIAL REGISTRATION

JAPIC Clinical Trials Information [JapicCTI-121986].) (Circ J 2016; 80: 1478-1483).

The Effect of Sorafenib, Tadalafil and Macitentan Treatments on Thyroxin-Induced Hemodynamic Changes and Cardiac Abnormalities

Multikinase inhibitors (e.g. Sorafenib), phosphodiesterase-5 inhibitors (e.g. Tadalafil), and endothelin-1 receptor blockers (e.g. Macitentan) exert influential protection in a variety of animal models of cardiomyopathy; however, their effects on thyroxin-induced cardiomyopathy have never been investigated. The goal of the present study was to assess the functional impact of these drugs on thyroxin-induced hemodynamic changes, cardiac hypertrophy and associated altered responses of the contractile myocardium both in-vivo at the whole heart level and ex-vivo at the cardiac tissue level. Control and thyroxin (500 μg/kg/day)-treated mice with or without 2-week treatments of sorafenib (10 mg/kg/day; I.P), tadalafil (1 mg/kg/day; I.P or 4 mg/kg/day; oral), macitentan (30 and 100 mg/kg/day; oral), and their vehicles were studied. Blood pressure, echocardiography and electrocardiogram were non-invasively evaluated, followed by ex-vivo assessments of isolated multicellular cardiac preparations. Thyroxin increased blood pressure, resulted in cardiac hypertrophy and left ventricular dysfunction in-vivo. Also, it caused contractile abnormalities in right ventricular papillary muscles ex-vivo. None of the drug treatments were able to significantly attenuate theses hemodynamic changes or cardiac abnormalities in thyroxin-treated mice. We show here for the first time that multikinase (raf1/b, VEGFR, PDGFR), phosphodiesterase-5, and endothelin-1 pathways have no major role in thyroxin-induced hemodynamic changes and cardiac abnormalities. In particular, our data show that the involvement of endothelin-1 pathway in thyroxine-induced cardiac hypertrophy/dysfunction seems to be model-dependent and should be carefully interpreted.