Randomized Trial of Macitentan/Tadalafil Single-Tablet Combination Therapy for Pulmonary Arterial Hypertension

BACKGROUND

Endothelin receptor antagonist (ERA) and phosphodiesterase 5 inhibitor (PDE5i) combination therapy is recommended for low-/intermediate-risk pulmonary arterial hypertension (PAH) patients. A fixed-dose combination of the ERA macitentan and PDE5i tadalafil (M/T FDC) in a once-daily, single tablet would simplify treatment.

OBJECTIVES

The multicenter, double-blind, adaptive phase 3 A DUE study investigated the efficacy and safety of M/T FDC vs macitentan 10 mg and vs tadalafil 40 mg monotherapies in PAH patients, including treatment-naïve and prior ERA or PDE5i monotherapy-treated patients.

METHODS

World Health Organization functional class II-III patients were randomized to M/T FDC, macitentan, or tadalafil depending on their PAH treatment (treatment-naïve, ERA, or PDE5i monotherapy) at baseline. The primary endpoint was change in pulmonary vascular resistance (PVR) at week 16.

RESULTS

In total, 187 patients were randomized to single-tablet M/T FDC (n = 108), macitentan (n = 35), or tadalafil (n = 44). PVR reduction with M/T FDC was significantly greater vs macitentan (29%; geometric mean ratio 0.71; 95% CL: 0.61-0.82; P < 0.0001) and vs tadalafil (28%; geometric mean ratio 0.72; 95% CL: 0.64-0.80; P < 0.0001). Three patients died in the M/T FDC arm (judged unrelated to treatment). Adverse events (AEs) leading to discontinuation, serious AEs, and those of special interest (anemia, hypotension, and edema) were more frequent with M/T FDC.

CONCLUSIONS

Macitentan and tadalafil FDC significantly improved PVR vs monotherapies in PAH patients, with a safety and tolerability profile consistent with the individual components. The A DUE study supports M/T FDC as a once-daily, single-tablet combination for initial therapy and escalation to double combination therapy in patients with PAH. (Clinical Study to Compare the Efficacy and Safety of Macitentan and Tadalafil Monotherapies With the Corresponding Fixed-dose Combination Therapy in Subjects With Pulmonary Arterial Hypertension [PAH]) [A DUE]; NCT03904693).

Endothelin Receptor Antagonists in Kidney Disease

Endothelin (ET) is found to be increased in kidney disease secondary to hyperglycaemia, hypertension, acidosis, and the presence of insulin or proinflammatory cytokines. In this context, ET, via the endothelin receptor type A (ET_A) activation, causes sustained vasoconstriction of the afferent arterioles that produces deleterious effects such as hyperfiltration, podocyte damage, proteinuria and, eventually, GFR decline. Therefore, endothelin receptor antagonists (ERAs) have been proposed as a therapeutic strategy to reduce proteinuria and slow the progression of kidney disease. Preclinical and clinical evidence has revealed that the administration of ERAs reduces kidney fibrosis, inflammation and proteinuria. Currently, the efficacy of many ERAs to treat kidney disease is being tested in randomized controlled trials; however, some of these, such as avosentan and atrasentan, were not commercialized due to the adverse events related to their use. Therefore, to take advantage of the protective properties of the ERAs, the use of ET_A receptor-specific antagonists and/or combining them with sodium-glucose cotransporter 2 inhibitors (SGLT2i) has been proposed to prevent oedemas, the main ERAs-related deleterious effect. The use of a dual angiotensin-II type 1/endothelin receptor blocker (sparsentan) is also being evaluated to treat kidney disease. Here, we reviewed the main ERAs developed and the preclinical and clinical evidence of their kidney-protective effects. Additionally, we provided an overview of new strategies that have been proposed to integrate ERAs in kidney disease treatment.

Endothelin-1 is increased in the plasma of patients hospitalised with Covid-19

Virus induced endothelial dysregulation is a well-recognised feature of severe Covid-19 infection. Endothelin-1 (ET-1) is the most highly expressed peptide in endothelial cells and a potent vasoconstrictor, thus representing a potential therapeutic target. ET-1 plasma levels were measured in a cohort of 194 Covid-19 patients stratified according to the clinical severity of their illness. Hospitalised patients, including those who died and those developing acute myocardial or kidney injury, had significantly elevated ET-1 plasma levels during the acute phase of infection. The results support the hypothesis that endothelin receptor antagonists may provide clinical benefit for certain Covid-19 patients.

Prostacyclins and pulmonary arterial hypertension in children

OBJECTIVE

Despite its low incidence, pulmonary hypertension in children places a substantial burden on families and society because survival can be shorter than 10 months and treatment options are limited and ineffective. Drugs to treat pulmonary hypertension include endothelin antagonists, phosphodiesterase type 5 inhibitors and prostacyclin, which is the most widely used to treat pediatric pulmonary hypertension. The main aim of this study was to provide a comprehensive overview of the advantages and disadvantages of prostacyclin and its analogs for treating pulmonary hypertension in children.

MATERIALS AND METHODS

To retrieve a thorough collection of studies, we performed a search in PubMed using the following combination of keywords: (Prostacyclins) or (Epoprostenol) or (Iloprost) or (Treprostinil) or (Beraprost), (children) and (pulmonary arterial hypertension). The time limits used for the search were December 1983 to May 2021.

RESULTS

The search retrieved a total of 238 articles. Titles and abstracts of articles were screened for relevance, and all relevant articles published in English were included.

CONCLUSIONS

Epoprostenol can be effective against severe pulmonary hypertension. Iloprost can treat severe persistent pulmonary hypertension in newborns and inhaled iloprost can be used in pulmonary vasoreactivity testing. Treprostinil is a long-acting prostacyclin analog, and it shows the highest antiproliferative activity among prostacyclins. Beraprost may be effective in premature infants, but available evidence comes from only one patient, so more clinical testing is needed.

Ameliorative role of bosentan, an endothelin receptor antagonist, against sodium arsenite-induced renal dysfunction in rats

Arsenic exposure is well documented to cause serious health hazards, such as cardiovascular abnormalities, neurotoxicity and nephrotoxicity. In the present study, we intended to explore the role of bosentan, an endothelial receptor antagonist, against sodium arsenite-induced nephrotoxicity and hepatotoxicity in rats. Sodium arsenite (5 mg/kg, oral) was administered for 4 weeks to induce renal dysfunction in rats. Sodium arsenite intoxicated rats were treated with bosentan (50 and 100 mg/kg, oral) for 4 weeks. Arsenic led renal damage was demonstrated by significant increase in serum creatinine, urea, uric acid, potassium, fractional excretion of sodium, microproteinuria and decreased creatinine clearance in rats. Sodium arsenite resulted in marked oxidative stress in rat kidneys as indicated by profound increase in lipid peroxides, and superoxide anion generation alongwith decrease in reduced glutathione levels. Hydroxyproline assay highlighted arsenic-induced renal fibrosis in rats. Hematoxylin-eosin staining indicated glomerular and tubular changes in rat kidneys. Picrosirius red staining highlighted collagen deposition in renal tissues of arsenic treated rats. Immunohistological results demonstrated the reduction of renal eNOS expression in arsenic treated rats. Notably, treatment with bosentan attenuated arsenic-induced renal damage and resisted arsenic-led reduction in renal eNOS expression. In addition, sodium arsenite-induced alteration in hepatic parameters (serum aspartate aminotransferase, alanine transferase, alkaline phosphatase, bilirubin), oxidative stress and histological changes were abrogated by bosentan treatment in rats. Hence, we conclude that bosentan treatment attenuated sodium arsenite-induced oxidative stress, fibrosis and reduction in renal eNOS expression in rat kidneys. Moreover, bosentan abrogated arsenic led hepatic changes in rats.

Collaborative registry of pulmonary hypertension in Argentina (RECOPILAR). Final analysis

The epidemiology of pulmonary hypertension (PH), especially pulmonary arterial hypertension (PAH), has not been evaluated in our country, therefore there is no reference parameter to establishing the representativeness of this information in the national order. This registry represents the first collaborative effort to provide a knowledge base of this disease, including 5 scientific societies that represent different specialties (pediatrics, rheumatology, pulmonology and cardiology) with data from 23 Argentine provinces. These efforts involved five societies of various adult (cardiology, rheumatology, and pulmonology) and pediatric (cardiology) specialties. Subjects were grouped (1-5) in accord with the 2013 Nice classification. A total of 627 patients (mean age, 50.8 ± 18 years; women, 69.2%) were recruited. Incident cases accounted for 53%. Functional class III-IV accounted for 69% at time of diagnosis and 33.4% at time of inclusion. Distributions in groups 1-5 were 63.6%, 15.9%, 8.3%, 9.7%, and 2.4%, respectively. Treatment consisted of diuretics (51.2%), mineralocorticoid receptor antagonists (44.7%), digoxin (16.6%), anticoagulants (39.2%), renin-angiotensin antagonists (15.5%), beta blockers (15.6%), and calcium channel blockers (8%). Rates of specific therapies usage in PAH vs. non-PAH group were 80.5% vs. 40.8% (phosphodiesterase-5 inhibitors: 71% vs. 38.6%; endothelin receptor antagonists: 54.4% vs. 14.5%; prostanoids: 14.3 vs. 3.1%; all p < 0.001). Three-year survival in PAH and non-PAH differed significantly (82.8% vs. 73.3%; p = 0.001). In the Argentine RECOPILAR registry, the clinic-epidemiologic profile was that of advanced-stage disease. Diagnostic workups and therapeutics interventions, including use of specific therapy for PAH, were consistent with current recommendations. Despite delays in diagnosis, survival was aligned with other contemporary registries.

[Pulmonary arterial hypertension (PAH ) : a new era of pulmonary arterial vasodilatators]

Pulmonary arterial hypertension (PAH) is a rare disease, characterized by a progressive increase in pulmonary arterial pressure. The therapeutic management of PAH patients has evolved significantly over the past decades following the appearance of new specific therapies, but also the performance of multiple clinical studies in an otherwise rare pathology. As a result, the care is very well codified and makes it possible to treat all patients at best. To date, we can cite four therapeutic families: endothelin receptor antagonists (ERA), drugs that interfere with the cyclic guanosine monophosphate (cGMP) pathway such as phosphodiesterase type 5 inhibitors (PDE5i) or the stimulator of soluble guanylate cyclase, prostacyclin analogues, and, finally, calcium antagonists. The therapeutic approach, formerly sequential, has proven to be insufficient in favor of an aggressive and rapidly progressive upfront therapeutic approach, making it possible to greatly improve the morbidity and mortality of patients. In this context, early management remains the most appropriate attitude and justifies recourse, from the first symptoms, to a competence center.

Involvement of Endothelin Receptors in Peripheral Sensory Neuropathy Induced by Oxaliplatin in Mice

The aim of this study was to evaluate the participation of the endothelin ET_A and ET_B receptors and the effects of bosentan in oxaliplatin-induced peripheral sensory neuropathy (OIN) in mice. Adult male Swiss mice received 1 mg/kg of oxaliplatin intravenously, twice a week for 5 weeks. Dorsal root ganglia (DRG) and spinal cords were removed for evaluation of the endothelin ET_A and ET_B receptor expression. Afterwards, selective (BQ-123 and BQ-788; 10 nmol in 30 μL, intraplantarly) and non-selective (bosentan, 100 mg/kg, orally) antagonists were administered in order to evaluate the involvement of the endothelin receptors in OIN. Mechanical and thermal nociception tests were performed once a week for 56 days. Oxaliplatin induced mechanical and thermal hypersensitivity and increased the endothelin ET_A receptor expression in both the DRG and spinal cord (P < 0.05). Endothelin ET_B receptor expression was increased in the DRG (P < 0.05) but not in the spinal cord. Both endothelin ET_A and ET_B receptor selective antagonists partially prevented mechanical hyperalgesia in mice with OIN (P < 0.05). Moreover, bosentan prevented mechanical and thermal hypersensitivity in oxaliplatin-treated mice (P < 0.05). In conclusion, both endothelin ET_A and ET_B receptors seem to be involved in the OIN in mice and they should be considered possible targets for the management of this clinical feature.

Sitaxsentan for Treatment of Pulmonary Hypertension

Objective:

To review the literature pertinent to the efficacy and safety of sitaxsentan, a selective endothelin (ET)-A receptor antagonist under evaluation for the treatment of pulmonary arterial hypertension (PAH).

Data Sources:

Articles were identified through searches of the MEDLINE (1966–November 2006) and International Pharmaceutical Abstracts (1970–November 2006) databases, using the key words endothelin antagonist, pulmonary arterial hypertension, pulmonary hypertension, sitaxsentan, and TBC11251. Searches were limited to articles published in English.

Study Selection And Data Extraction:

Due to the limited number of articles on sitaxsentan, all studies captured in the search results were evaluated.

Data Synthesis:

Four studies of sitaxsentan in humans with PAH have been published to date. An uncontrolled open-label study and a randomized placebo-controlled study (STRIDE-1; Sitaxsentan to Relieve Impaired Exercise-1) showed sitaxsentan to improve exercise tolerance in patients with PAH, as evidenced by significant increases in the distance walked in 6 minutes. Significant hepatotoxicity developed in patients receiving sitaxsentan 300 mg. The benefits of sitaxsentan with respect to exercise tolerance and hemodynamics were sustained in a one year extension of the placebo-controlled study. The results of a multicenter, randomized, placebo-controlled trial of 2 doses of sitaxsentan with an open-label bosentan arm (STRIDE-2) suggested that only the 100 mg dose provided superior benefit in exercise tolerance and improvement in functional class. Treatment-related adverse effects were similar for all groups.

Conclusions:

Sitaxsentan appears to be superior to placebo in improving exercise tolerance in patients with PAH but may produce therapeutic outcomes similar to those of bosentan, a comparator agent. The optimal dose of sitaxsentan appears to be 100 mg once daily. Information about the use of sitaxsentan in a greater number of patients with PAH for longer periods is necessary to further define its place in the treatment of PAH.

Diurnal variation in blood pressure and arterial stiffness in chronic kidney disease: the role of endothelin-1

Hypertension and arterial stiffness are important independent cardiovascular risk factors in chronic kidney disease (CKD) to which endothelin-1 (ET-1) contributes. Loss of nocturnal blood pressure (BP) dipping is associated with CKD progression, but there are no data on 24-hour arterial stiffness variation. We examined the 24-hour variation of BP, arterial stiffness, and the ET system in healthy volunteers and patients with CKD and the effects on these of ET receptor type A receptor antagonism (sitaxentan). There were nocturnal dips in systolic BP and diastolic BP and pulse wave velocity, our measure of arterial stiffness, in 15 controls (systolic BP, −3.2±4.8%, P<0.05; diastolic BP, −6.4±6.2%, P=0.001; pulse wave velocity, −5.8±5.2%, P<0.01) but not in 15 patients with CKD. In CKD, plasma ET-1 increased by 1.2±1.4 pg/mL from midday to midnight compared with healthy volunteers (P<0.05). Urinary ET-1 did not change. In a randomized, double-blind, 3-way crossover study in 27 patients with CKD, 6-week treatment with placebo and nifedipine did not affect nocturnal dips in systolic BP or diastolic BP between baseline and week 6, whereas dipping was increased after 6-week sitaxentan treatment (baseline versus week 6, systolic BP: −7.0±6.2 versus −11.0±7.8 mm Hg, P<0.05; diastolic BP: −6.0±3.6 versus −8.3±5.1 mm Hg, P<0.05). There was no nocturnal dip in pulse pressure at baseline in the 3 phases of the study, whereas sitaxentan was linked to the development of a nocturnal dip in pulse pressure. In CKD, activation of the ET system seems to contribute not only to raised BP but also the loss of BP dipping. The clinical significance of these findings should be explored in future clinical trials.

Endothelin receptor antagonists

Three pathways have been identified in the pathogenesis of pulmonary arterial hypertension (PAH): the endothelin (ET), nitric oxide (NO) and prostacyclin pathways. These pathways represent the targets of approved PAH therapies and their discovery has facilitated significant progress in the understanding and treatment of PAH. The ET system is well established as a key player in the pathophysiology of PAH, with deleterious effects mediated by both the ETA and ETB receptors. Endothelin receptor antagonists (ERAs) are an important part of PAH therapy, with two ERAs currently approved for the treatment of PAH and a novel ERA that has recently been investigated in a Phase III clinical trial. This chapter describes the role of ET in the pathogenesis of PAH, reviews experimental data and examines the clinical status of ERAs in PAH treatment.

Drug treatment of pulmonary hypertension in children

Pulmonary arterial hypertension (PAH) is a rare disease in infants and children that is associated with significant morbidity and mortality. The disease is characterized by progressive pulmonary vascular functional and structural changes resulting in increased pulmonary vascular resistance and eventual right heart failure and death. In the majority of pediatric patients, PAH is idiopathic or associated with congenital heart disease and rarely is associated with other conditions such as connective tissue or thromboembolic disease. Although treatment of the underlying disease and reversal of advanced structural changes has not yet been achieved with current therapy, quality of life and survival have been improved significantly. Targeted pulmonary vasodilator therapies, including endothelin receptor antagonists, prostacyclin analogs, and phosphodiesterase type 5 inhibitors, have demonstrated hemodynamic and functional improvement in children. The management of pediatric PAH remains challenging, as treatment decisions continue to depend largely on results from evidence-based adult studies and the clinical experience of pediatric experts. This article reviews the current drug therapies and their use in the management of PAH in children.

Evaluation of the endothelin receptor antagonists ambrisentan, bosentan, macitentan, and sitaxsentan as hepatobiliary transporter inhibitors and substrates in sandwich-cultured human hepatocytes

Background

Inhibition of the transporter-mediated hepatobiliary elimination of bile salts is a putative mechanism for liver toxicity observed with some endothelin receptor antagonists (ERAs).

Methods

Sandwich-cultured human hepatocytes were used to study the hepatobiliary distribution and accumulation of exogenous taurocholate, ERAs and endogenous bile acids. The molecular mechanisms for findings in hepatocytes or clinical observations were further explored using either vesicular assays (efflux transporters) or transfected cell-lines (uptake transporters). Inhibition constants (IC₅₀) were measured for the human hepatobiliary transporters bile salt export pump (BSEP), sodium taurocholate cotransporting polypeptide (NTCP), multidrug resistance protein 2 (MRP2), P-glycoprotein (Pgp), breast cancer resistance protein (BCRP), organic anion-transporting polypeptide 1B1 (OATP1B1) and OATP1B3.

Results

The ERAs showed dose-dependent reductions in exogenous taurocholate cellular accumulation in human hepatocytes, with macitentan having the greatest effect. Consistent with their effects on bile acids, the ERAs inhibited bile transporters. IC₅₀ values for OATP1B1 and OATP1B3 ranged from 2 µM for macitentan to 47 µM for ambrisentan. Macitentan and bosentan also inhibited NTCP with IC₅₀ values of 10 and 36 µM, respectively. Similar to previously reported findings with sitaxsentan, BSEP inhibition was observed for bosentan and macitentan with IC₅₀ values of 42 and 12 µM, respectively. In contrast, ambrisentan showed little or no inhibition of these transporters. Other transporters tested were weakly inhibited by the ERAs. Accumulation in hepatocytes was also a factor in the effects on bile transport. Macitentan demonstrated the greatest accumulation in human hepatocytes (∼100x) followed by sitaxsentan (∼40x), bosentan (∼20x) and ambrisentan (∼2x).

Conclusions

Significant differences in the inhibition of hepatic transporters were observed between the evaluated ERAs in vitro. Macitentan had the highest level of cellular accumulation and caused the greatest effects on bile acid distribution in human hepatocytes followed by sitaxsentan and bosentan. Ambrisentan showed a low potential to affect bile acids.

Bosentan

Bosentan (Tracleer, Actelion Pharmaceuticals Ltd) is an oral dual endothelin receptor antagonist approved for use in functional class III to IV pulmonary arterial hypertension. In two placebo-controlled trials, patients receiving bosentan showed improved functional class, 6-minute walk distance and hemodynamics over a 12- to 16-week period. Follow-up data over 3 years has shown few deteriorations,with the majority of patients maintaining their response to bosentan alone. Investigations exploring the use of bosentan as an add-on agent to intravenous epoprostenol (Flolan, GlaxoSmithKline Plc) in those with the most severe disease are ongoing. Bosentan may also have antifibrotic properties and its use in pulmonary fibrosis is being explored. Ease of administration of bosentan with twice-daily oral dosing will provide many patients with pulmonary hypertension an option for treatment without the risks and discomforts of continuous intravenous medication.

[Choice of novel endpoints in clinical trials evaluating the efficiency of drug therapy in patients with pulmonary hypertension]

Pulmonary hypertension (PH) is characterized by a poor prognosis: the three-year survival rate in patients with PH is not greater than 60% as evidenced by current national registries. In the past decade, there have been drugs that are able to relieve symptoms of the disease, to slow down its progression, and improve quality of life. Historically, clinical trials dealing with PH have had a fixed and rather short-tern period and most commonly used the index "the change in the distance covered in the 6-minute walk test" as a primary endpoint. Further optimization of PH therapy requires that the efficacy of drugs and the strategies of therapy be evaluated with respect to their effects on morbidity and mortality, i.e. on prognosis. The SERAPHIN trial is now the only completed and published clinical trial using the combined index of morbidity and mortality as a primary endpoint. It demonstrates that that therapy with the novel drug macitentan causes a reduction in morbidity and mortality in patients with PH.

[Bosentan: a considerable increase in the survival of patients with pulmonary hypertension associated with systemic rheumatic diseases]

AIM

To evaluate the short-term efficacy of the nonselective endothelin receptor antagonist bosentan in the treatment of pulmonary hypertension (PH) associated with diffuse connective tissue diseases (CTD), as well as its effect on survival in both monotherapy and in combination with other PH-specific agents.

SUBJECTS AND METHODS

The study included 20 CDT-associated PH patients who had been hospitalized in 2009-2013. All the patients had valid diagnoses of scleroderma systematica (SDS) (n = 18) or systemic lupus erythematosus (SLE) (n = 2). Bosentan was given in an initial dose of 62.5 mg/day twice for 4 weeks, then 125 mg/day twice.

RESULTS

Eighteen patents completed therapy at 16 weeks. One patient with Functional Class (FC) IV PH associated with SDS died after 10 weeks of treatment because of PH progression; bosentan was discontinued in another patient following 4 weeks because of the enhanced activity of transaminases. The patients who had completed the investigation showed a significant FC decrease (from 2.9 +/- 1.0 to 2.4 +/- 1.0 following 16 weeks; p = 0.03), an increase in 6-minute walking distance (from 298 +/- 140 to 375 +/- 94 m; p < 0.002), a significant reduction in mean pulmonary artery pressure (from 48.2 +/- 15.0 to 42.8 +/- 12.0 mm Hg; p = 0.002), and pulmonary vascular resistance (PVR) (from 819 +/- 539 to 529 +/- 220 din/sec/cm(-5); p = 0.003). Right atrial pressure fell from 9.8 +/- 7.0 to 8.8 +/- 7.0 mm Hg; however, the changes were insignificant. There was a significant rise in cardiac index from 2.64 +/- 0.95 to 3.26 +/- 0.75 l/min/m2 (p = 0.005) and a significant decrease in uric acid levels from 562 +/- 254 to 469 +/- 194 micromol/l (p = 0.006). Overall 1-, 3-, and 5-year survival rates in patients with PH in the presence of CTD from PH onset were 100, 93, and 72%, respectively, in their treatment with endothelin receptor antagonists and differed significantly from the historical control group (87, 30, and 4%, respectively) when PH-specific therapy was unavailable.

CONCLUSION

The survival of the bosentan-treated patients with SDS and PH becomes similar to that in the patients with classical SDS. Analysis of the findings revealed the association of survival with lower PVR at 16 weeks of bosentan therapy, which is indicative of the need for hemodynamic monitoring of therapeutic effectiveness.

[Pulmonary arterial hypertension, a rare entity]

Pulmonary arterial hypertension (PAH) is a rare disease. It is characterized by the progressive remodeling of the small pulmonary arteries that lead to an elevation of the pulmonary vascular resistance and right ventricular dysfunction. Early diagnosis and prompt treatment avoid the deterioration of the patient's quality of life. Statistics show that there are 15 cases per million people worldwide, the majority comprised of young women, with an age at diagnosis of 30 to 40 years. At present, the exact processes that initiate the pathophysiologic changes observed in PAH are unknown; it is thought to be multifactorial. Diagnosis in PAH must be done in a step by step manner. Under the suspicion of pulmonary hypertension (PH), the first thing to do is confirm the diagnosis. The second step is to identify the specific etiology and lastly evaluate the severity by echocardiography, hemodynamic parameters, biomarkers and exercise capacity. PH treatment, particularly PAH, has evolved over the last 2 decades due to the advance in disease knowledge and the availability of agents that act on different pathways. Concerning surgical treatment, it is indicated in PAH when there is not an adequate response to medical treatment. In conclusion, PAH is recognized worldwide as a rare or infrequent disease. The countries that have a registry for the diagnostics, treatment, follow-up and prevalence of PH are mainly in Europe. With the exception of the United States and Canada, there are no registries in America. Recent years have shown an important advance in Latin America.

Effect of endothelin inhibition on lung fibroblasts on patients with systemic sclerosis

AIM

The aim of the study was to investigate the effect of selective ETRA Sitaxsentan on viability and differentiation into myofibroblasts of lung fibroblasts derived from SSc-ILD patients and the ability of this drug to modify the lung fibroblast synthesis of VEGF, type I collagen and fibronectin.

METHODS

Primary human lung fibroblast cultures were obtained from BAL of SSc-ILD patients. Cell cultures were exposed for 48 h to crescent concentrations of Sitaxsentan (10 -6M to 10 -4M). In these experimental conditions we evaluated cell viability through crystal violet staining, the production and mRNA expression of VEGF, fibronectin and type I collagen respectively through ELISA and real-Time PCR. Further, we detected alpha-Smooth Muscle Actin (α-SMA) through immunocytochemical assay.

RESULTS

The lowest concentration of sitaxsentan (10-6M) did not affect fibroblasts viability; conversely at higher concentrations, sitaxsentan induced a significant inhibition of cell viability. Synthesis and mRNA expression of VEGF, type 1 collagen and fibronectin were significantly reduced in treated lung fibroblasts compared to the untreated ones, in a dose-dependent manner. At higher concentrations, Sitaxsentan reduced the expression of α-SMA.

CONCLUSION

The results of this study show that sitaxentan is able in vitro to reduce both cell viability than production of VEGF and extra-cellular matrix components in SSc lung fibroblasts, confirming the anti-fibrotic potential of ETRA in SSc. The decreased expression of α-SMA in treated cells indicate that sitaxsentan may inhibit the fibroblast differentiation toward a myo-fibroblast phenotype and further support the hypothesis that the selective ETRAs may be beneficial in patients with SSc-ILD as anti fibrotic agents.

Riociguat for the treatment of pulmonary arterial hypertension

BACKGROUND

Riociguat, a soluble guanylate cyclase stimulator, has been shown in a phase 2 trial to be beneficial in the treatment of pulmonary arterial hypertension.

METHODS

In this phase 3, double-blind study, we randomly assigned 443 patients with symptomatic pulmonary arterial hypertension to receive placebo, riociguat in individually adjusted doses of up to 2.5 mg three times daily (2.5 mg-maximum group), or riociguat in individually adjusted doses that were capped at 1.5 mg three times daily (1.5 mg-maximum group). The 1.5 mg-maximum group was included for exploratory purposes, and the data from that group were analyzed descriptively. Patients who were receiving no other treatment for pulmonary arterial hypertension and patients who were receiving endothelin-receptor antagonists or (nonintravenous) prostanoids were eligible. The primary end point was the change from baseline to the end of week 12 in the distance walked in 6 minutes. Secondary end points included the change in pulmonary vascular resistance, N-terminal pro-brain natriuretic peptide (NT-proBNP) levels, World Health Organization (WHO) functional class, time to clinical worsening, score on the Borg dyspnea scale, quality-of-life variables, and safety.

RESULTS

By week 12, the 6-minute walk distance had increased by a mean of 30 m in the 2.5 mg-maximum group and had decreased by a mean of 6 m in the placebo group (least-squares mean difference, 36 m; 95% confidence interval, 20 to 52; P<0.001). Prespecified subgroup analyses showed that riociguat improved the 6-minute walk distance both in patients who were receiving no other treatment for the disease and in those who were receiving endothelin-receptor antagonists or prostanoids. There were significant improvements in pulmonary vascular resistance (P<0.001), NT-proBNP levels (P<0.001), WHO functional class (P=0.003), time to clinical worsening (P=0.005), and Borg dyspnea score (P=0.002). The most common serious adverse event in the placebo group and the 2.5 mg-maximum group was syncope (4% and 1%, respectively).

CONCLUSIONS

Riociguat significantly improved exercise capacity and secondary efficacy end points in patients with pulmonary arterial hypertension. (Funded by Bayer HealthCare; PATENT-1 and PATENT-2 ClinicalTrials.gov numbers, NCT00810693 and NCT00863681, respectively.).

Simulation of the Impact of Atropisomer Interconversion on Plasma Exposure of Atropisomers of an Endothelin Receptor Antagonist

BMS-207940, a potent endothelin receptor antagonist, exists as rapidly interconverting atropisomers. The plasma interconversion t(1/2) is approximately 2.5 hours at 400 microg/mL under room temperature and decreases to < 0.1 hours at 20 microg/mL, making it extremely difficult to conduct pharmacokinetic studies of individual atropisomers. The pharmacokinetics of the 50/50 racemate of BMS-207940 in humans were reasonably described by a one-compartmental model with an apparent terminal elimination t(1/2) of 15 hours. Given the above rates, simulations were conducted based on a one-compartmental model to explore the possible range of individual rates of atropisomer elimination and potential difference in plasma exposure to the two atropisomers. Simulations demonstrated that the elimination rates of the individual atropisomers are bounded between 0 and 0.046 h(-1) and between 0.046 and 0.092 h(-1), respectively. The estimation of the upper bounds for atropisomer elimination rate constants is robust and relatively insensitive to the rate of atropisomer interconversion compared to the rate of racemate elimination. Simulations of the administration of a single atropisomer or the 50/50 racemate, based on all the possible scenarios of individual atropisomer elimination, showed little difference in plasma exposure to the two atropisomers. Potential differences in plasma exposure to the two atropisomers depend, to a larger extent, on the ratio of the rate of atropisomer interconversion versus racemate elimination and, to a lesser extent, on the conformation of atropisomers administered. When atropisomer interconversion is 10-fold or more rapid than racemate elimination, the largest possible difference in plasma exposure between the two atropisomers is below 20%, regardless of the route and conformation of the atropisomer(s) administered.

Influence of Ethnic Origin and Sex on the Pharmacokinetics of Clazosentan

This study investigated the influence of ethnic origin and, as a secondary objective, sex on the pharmacokinetics of the parenteral endothelin receptor antagonist clazosentan in healthy Caucasian and Japanese subjects. Twelve subjects of each ethnic origin (female/male ratio 1:1) were treated with sequential 4-hour infusions of 1, 5, and 15 mg/h. Blood samples were taken frequently to determine plasma levels of clazosentan. The exposure to clazosentan was approximately 16% higher in Japanese subjects compared with Caucasian subjects and 18% higher in females compared with males. These differences were mainly attributable to a difference in clearance. A 3-compartment model well described the plasma concentration-time profiles of clazosentan with disposition half-lives of approximately 6 minutes, 21 minutes, and 2.7 hours. The data suggest that Caucasian and Japanese patients can be treated with a similar dosing regimen of clazosentan. At the doses infused, administration of clazosentan was safe and well tolerated in both ethnic groups.

Endothelin receptor antagonists for pulmonary arterial hypertension

BACKGROUND

Pulmonary arterial hypertension is a devastating disease, which leads to right heart failure and premature death. Recent evidence suggests that endothelin receptor antagonists may be promising drugs in the treatment of pulmonary arterial hypertension.

OBJECTIVES

To evaluate the efficacy of endothelin receptor antagonists in pulmonary arterial hypertension.

SEARCH METHODS

We searched CENTRAL (Cochrane Central Register of Controlled Trials), MEDLINE, EMBASE, and the reference section of retrieved articles. Searches are current as of January 2012.

SELECTION CRITERIA

We included randomised trials (RCTs) and quasi-randomised trials involving patients with pulmonary arterial hypertension.

DATA COLLECTION AND ANALYSIS

Five review authors independently selected studies, assessed study quality and extracted data.

MAIN RESULTS

We included 12 randomised controlled trials involving 1471 patients. All the trials were of relatively short duration (12 weeks to six months). After treatment, patients treated with endothelin receptor antagonists could walk on average 33.71 metres (95% confidence interval (CI) 24.90 to 42.52 metres) further than those treated with placebo in a six-minute walk test. Endothelin receptor antagonists improved more patients' World Health Organization/New York Heart Association (WHO/NYHA) functional class status than placebo (odds ratio (OR) 1.60; 95% CI 1.20 to 2.14), and reduced the odds of functional class deterioration compared with placebo (OR 0.26; 95% CI 0.16 to 0.42). There was a reduction in mortality that did not reach statistical significance on endothelin receptor antagonists (OR 0.57; 95% CI 0.26 to 1.24), and limited data suggest that endothelin receptor antagonists improve the Borg dyspnoea score and cardiopulmonary haemodynamics in symptomatic patients. Hepatic toxicity was not common, and endothelin receptor antagonists were well tolerated in this population. However, several cases of irreversible liver failure caused by sitaxsentan have been reported that led to license holder for sitaxsentan to withdraw the product from all markets worldwide.

AUTHORS' CONCLUSIONS

Endothelin receptor antagonists can increase exercise capacity, improve WHO/NYHA functional class, prevent WHO/NYHA functional class deterioration, reduce dyspnoea and improve cardiopulmonary haemodynamic variables in patients with pulmonary arterial hypertension with WHO/NYHA functional class II and III. However, there was only a trend towards endothelin receptor antagonists reducing mortality in patients with pulmonary arterial hypertension. Efficacy data are strongest in those with idiopathic pulmonary hypertension. The irreversible liver failure caused by sitaxsentan and its withdrawal from global markets emphasise the importance of hepatic monitoring in patients treated with endothelin receptor antagonists.

Interaction profile of macitentan, a new non-selective endothelin-1 receptor antagonist, in vitro

Macitentan is a new non-selective endothelin-1 receptor antagonist under development for the treatment of pulmonary arterial hypertension. Information on the potential for macitentan to influence the pharmacokinetics of concomitantly administered drugs by inhibition or induction of drug metabolising enzymes or drug transporters is sparse. We therefore studied the potential of macitentan to inhibit and induce critical targets of drug metabolism and drug distribution (transporters) in vitro. Induction was quantified at the mRNA level by real-time RT-PCR in LS180 cells and revealed that macitentan significantly induced mRNA expression of cytochrome P450 3A4 (CYP3A4), P-glycoprotein (P-gp, ABCB1), solute carrier of organic anions 1B1 (SLCO1B1), and uridinediphosphate-glucuronosyltransferase 1A3 (UGT1A9). By means of a reporter gene assay our study establishes macitentan as a potent activator of pregnane X receptor (PXR). Inhibition of drug transporters was evaluated by using transporter over-expressing cell lines and fluorescent specific substrates of the respective transporters and revealed that macitentan is an inhibitor of P-gp, breast cancer resistance protein (BCRP), SLCO1B1, and SLCO1B3. Using commercial kits macitentan was demonstrated to be a moderate inhibitor of CYP3A4 and CYP2C19. In conclusion our data provide a comprehensive analysis of the interaction profile of macitentan with drug metabolising and transporting enzymes in vitro. Although macitentan has a similar or higher potency for induction and inhibition of drug metabolising enzymes and transporters than bosentan, its low plasma concentrations and minimal accumulation in the liver suggest that it will be markedly less prone to drug-drug interactions than bosentan.

Potential new treatments for diabetic kidney disease

Antifibrotic agents, antioxidant agents, ET-a receptor antagonists, and a few other agents with nonspecific or multifaceted mechanisms of action have been evaluated and progressed to small clinical studies in human subjects. Although there are limited data at the present time, these early evaluations have produced some favorable results that at least warrant further investigation. There is certainly not enough compelling evidence to justify the routine use of any of these products specifically for DKD at the moment; however, more well-controlled and adequately powered studies in several hundred patients will help determine which of these may have a place in the DKD treatment armamentarium of the future.

[First clinical experience with endothelin receptor antagonist bosentan used in patients with pulmonary hypertension: results of a one-year study]

AIM

To evaluate the efficiency and safety of long-term (12-month) treatment with the endothelin receptor antagonist bosentan (tracleer (Actelion, Switzerland)) in patients with pulmonary hypertension (PH).

SUBJECTS AND METHODS

The prospective observational study enrolled 10 patients (8 with idiopathic PH and 2 with PH and systemic scleroderma). The patients' mean age was 50.0 +/- 6.9 years; mean pulmonary artery pressure (mPAP) 65 +/- 12 mm Hg; cardiac output (CO) 3.4 +/- 0.8 l/min; 6-minute walk test (6'WT) distance, 318 +/- 94 m. Before and 3, 6, and 12 months after the treatment, the patients underwent Doppler echocardiography, arterial blood gas analysis, external respiratory function test, and dyspnea evaluation using the MRC scale and 6'WT. The initial dose of bosentan was 62.5 mg b.i.d., then 125 mg b.i.d. following 4 weeks.

RESULTS

Bosentan treatment resulted in a reduction in pulmonary artery systolic pressure and mPAP (at 12 months: 76.8 +/- 11.5 and 58.8 +/- 11.4 mm Hg, respectively; p < 0.01) and an increase in CO (at 12 months: 4.2 +/- 1.2 l/min; p = 0.002). Six patients were observed to have a lower WHO classification functional class (FC). Lung diffusing capacity tended to improve (at 12 months, the increment was more than 6% of the reference value; p = 0.059). In the patients, dyspnea was relieved as shown by MRS scores from 3.1 +/- 0.7 (at baseline) to 2.1 +/- 0.6 (at 12 months); p = 0.002. The 6'WT distance increased up to 342 +/- 67 m (at 12 months); p = 0.005. The drug was well tolerated; only one patient had a transient increase in the activity of liver enzymes.

CONCLUSION

The long-term bosentan treatment in patients with PH leads to improvements in pulmonary hemodynamics, WHO classification functional class, a reduction in dyspnea, and a rise in exercise tolerance.

sGC stimulation totally reverses hypoxia-induced pulmonary vasoconstriction alone and combined with dual endothelin-receptor blockade in a porcine model

AIM

Stimulation of soluble guanylate cyclase (sGC) with BAY 41-8543 was hypothesized to attenuate acute hypoxic pulmonary vasoconstriction alone and combined with dual endothelin (ET)-receptor antagonist tezosentan.

METHODS

Measurements were taken in 18 anaesthetized pigs with a mean ± SEM weight of 31.1 ± 0.4 kg, in normoxia (FiO(2)~0.21) and hypoxia (FiO(2)~0.10) without (control protocol, n = 6), and with right atrial infusion of BAY 41-8543 at 1, 3, 6, 9 and 12 μg min(-1) per kg (protocol 2, n = 6) or tezosentan at 5 mg kg(-1) followed by BAY 41-8543 at 1, 3 and 6 μg min(-1) per kg (protocol 3, n = 6).

RESULTS

Hypoxia (n = 18) increased (P < 0.001) mean pulmonary artery pressure (MPAP) and pulmonary vascular resistance (PVR) by 14.2 ± 0.6 mmHg and 2.8 ± 0.3 WU respectively. During sustained hypoxia without treatment, MPAP and PVR remained stable. BAY 41-8543 (n = 6) dose-dependently decreased (P < 0.001) MPAP and PVR by 15.0 ± 1.2 mmHg and 4.7 ± 0.7 WU respectively. Tezosentan (n = 6) decreased (P < 0.001) MPAP and PVR by 11.8 ± 1.2 mmHg and 2.0 ± 0.2 WU, respectively, whereafter BAY 41-8543 (n = 6) further decreased (P < 0.001) MPAP and PVR by 6.6 ± 0.9 mmHg and 1.9 ± 0.4 WU respectively. Both BAY 41-8543 and tezosentan decreased (P < 0.001) systemic arterial pressure and systemic vascular resistance. Blood-O(2) consumption remained unaltered (P = ns) during all interventions.

CONCLUSION

BAY 41-8543 totally reverses the effects of acute hypoxia-induced pulmonary vasoconstriction, and enhances the attenuating effects of tezosentan, without affecting oxygenation. Thus, sGC stimulation, alone or combined with dual ET-receptor blockade, could offer a means to treat pulmonary hypertension related to hypoxia and potentially other causes.

Slow receptor dissociation kinetics differentiate macitentan from other endothelin receptor antagonists in pulmonary arterial smooth muscle cells

Two endothelin receptor antagonists (ERAs), bosentan and ambrisentan, are currently approved for the treatment of pulmonary arterial hypertension (PAH), a devastating disease involving an activated endothelin system and aberrant contraction and proliferation of pulmonary arterial smooth muscle cells (PASMC). The novel ERA macitentan has recently concluded testing in a Phase III morbidity/mortality clinical trial in PAH patients. Since the association and dissociation rates of G protein-coupled receptor antagonists can influence their pharmacological activity in vivo, we used human PASMC to characterize inhibitory potency and receptor inhibition kinetics of macitentan, ambrisentan and bosentan using calcium release and inositol-1-phosphate (IP₁) assays. In calcium release assays macitentan, ambrisentan and bosentan were highly potent ERAs with K_b values of 0.14 nM, 0.12 nM and 1.1 nM, respectively. Macitentan, but not ambrisentan and bosentan, displayed slow apparent receptor association kinetics as evidenced by increased antagonistic potency upon prolongation of antagonist pre-incubation times. In compound washout experiments, macitentan displayed a significantly lower receptor dissociation rate and longer receptor occupancy half-life (ROt_1/2) compared to bosentan and ambrisentan (ROt_1/2∶17 minutes versus 70 seconds and 40 seconds, respectively). Because of its lower dissociation rate macitentan behaved as an insurmountable antagonist in calcium release and IP₁ assays, and unlike bosentan and ambrisentan it blocked endothelin receptor activation across a wide range of endothelin-1 (ET-1) concentrations. However, prolongation of the ET-1 stimulation time beyond ROt_1/2 rendered macitentan a surmountable antagonist, revealing its competitive binding mode. Bosentan and ambrisentan behaved as surmountable antagonists irrespective of the assay duration and they lacked inhibitory activity at high ET-1 concentrations. Thus, macitentan is a competitive ERA with significantly slower receptor dissociation kinetics than the currently approved ERAs. Slow dissociation caused insurmountable antagonism in functional PASMC-based assays and this could contribute to an enhanced pharmacological activity of macitentan in ET-1-dependent pathologies.

Endothelin receptor antagonists for subarachnoid hemorrhage

BACKGROUND

A subarachnoid hemorrhage (SAH) is a serious and potentially life-threatening condition where blood leaks out of blood vessels over the surface of the brain. Delayed ischemic neurological deficit (DIND) and the related feature of vasospasm, where patients experience a delayed deterioration, have long been recognized as the leading potentially treatable cause of death and disability in patients with SAH. Endothelin is a potent, long-lasting endogenous vasoconstrictor that has been implicated in the pathogenesis of DIND. Therefore, endothelin receptor antagonists (ETAs) have emerged as a promising therapeutic option for SAH-induced cerebral vasospasm.

OBJECTIVES

To assess the efficacy and tolerability of ETAs for SAH.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (December 2011), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2011, Issue 11), MEDLINE (1950 to December 2011), EMBASE (1946 to December 2011) and the Chinese Biomedical Database (1978 to December 2011). In an effort to identify further published, unpublished and ongoing trials we searched additional Chinese databases, ongoing trials registers, Google Scholar and Medical Matrix, handsearched journals, scanned reference lists, and contacted researchers and pharmaceutical companies.

SELECTION CRITERIA

We only included randomized controlled trials (RCTs) that compared an ETA with placebo for SAH in adult (18 years of age or older) patients who met the diagnostic criteria for SAH based on clinical symptoms, with confirmation on computerized tomography scan results or angiography. Two review authors independently selected RCTs according to the inclusion criteria. We resolved disagreements by discussion with a third review author.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected relevant articles and assessed their eligibility according to the inclusion and exclusion criteria. We resolved disagreements by discussion with a third review author. We used the random-effects model and expressed the results as risk ratio (RR) for dichotomous outcomes and mean difference (MD) for continuous outcomes with 95% confidence intervals (CI).

MAIN RESULTS

We included four RCTs with 2024 participants that compared ETAs with placebo for SAH. All RCTs were multicenter, double-blind studies with a low risk of bias. ETAs reduced the incidence of DIND (RR 0.80; 95% CI 0.67 to 0.95) and angiographic vasospasm (RR 0.62; 95% CI 0.52 to 0.72) but did not reduce the incidence of unfavorable outcomes (RR 0.87; 95% CI 0.74 to 1.02) or mortality (RR 1.05; 95% CI 0.77 to 1.45). ETAs increased the incidence of hypotension (RR 2.53; 95% CI 1.77 to 3.62) and pneumonia (RR 1.56; 95% CI 1.23 to 1.97).

AUTHORS' CONCLUSIONS

ETAs appear to reduce DIND and angiographic vasospasm but there were adverse events and the impact on clinical outcome is unclear. Additional well-designed RCTs are needed.

Insulin and Endothelin in the Acute Regulation of Adiponectin in Vivo in Humans

OBJECTIVE

In vitro, insulin and endothelin (ET) both modulate adiponectin secretion from adipocyte cell lines. The current studies were performed to assess whether endogenous ET contributes to the acute action of insulin infusions on adiponectin levels in vivo in humans.

RESEARCH METHODS AND PROCEDURES

We studied 17 lean and 20 obese subjects (BMI 21.8 +/- 2.2 and 34.0 +/- 5.0 kg/m(2), respectively). Hyperinsulinemic euglycemic clamp studies were performed using insulin infusion rates of 10, 30, or 300 mU/m(2) per minute alone or with concurrent infusion of BQ123, an antagonist of type A ET receptors. Circulating adiponectin levels were assessed at baseline and after achievement of steady-state glucose with the insulin infusion.

RESULTS

Adiponectin levels were lower in obese than lean subjects (6.76 +/- 3.66 vs. 8.37 +/- 2.79 microg/mL, p = 0.0148 adjusted for differences across gender). Insulin infusions suppressed adiponectin by a mean of 7.8% (p < 0.0001). In a subset of 13 lean and 14 obese subjects for whom data with and without BQ123 were available, there was no evident effect of BQ123 to modulate clamp-associated suppression of adiponectin (p = 0.16). Surprisingly, there was no evident relationship between steady-state insulin concentrations and adiponectin suppression (r = 0.14, p = 0.30), and again no effect of BQ123 to modify this relationship was seen.

DISCUSSION

Despite baseline differences in adiponectin levels, we observed equal suppression of adiponectin with insulin infusions in lean and obese subjects. ET receptor antagonism with BQ123 did not modulate this effect, suggesting that endogenous ET does not have a role in modifying the acute effects of insulin on adiponectin production and/or disposition.

Changes in exercise capacity and cardiac performance in a series of patients with Eisenmenger's syndrome transitioned from selective to dual endothelin receptor antagonist

BACKGROUND

Differences in clinical effects between selective and dual endothelin (ET) receptor antagonists (ERA) in patients with pulmonary arterial hypertension (PAH) are currently unknown. We aimed to assess prospectively how transition from selective (sitaxsentan) to dual (bosentan) ERA affected exercise capacity and cardiocirculatory performance in patients with Eisenmenger's syndrome.

METHODS

A series of seven stable patients with Eisenmenger's syndrome aged 40.0 (30.0-56.0) years old treated with sitaxsentan were assessed before and three months after transition to bosentan. Six minute walk test and magnetic resonance to assess LV and RV mass, volume and ejection fraction, and pulmonary flow, and laboratory tests were performed.

RESULTS

We observed an increase in LV mass [96.5 (66.0-116.0) vs. 123.0 (93.0-146.0)g; p=0.03], LV ejection fraction [55.0 (44.0-63.0) vs. 65.0 (58.0-70.0)%; p=0.02)], and pulmonary flow [64 (53.0-71.0) vs. 69.0 (55.0-84.0)ml/beat; p=0.046]. This was accompanied by an increase of oxygen saturation, elongation of 6MWD [435.0 (378.0-482.3) vs. 474 (405.0-534.7); p=0.02], decrease of NTproBNP level and increase of ET-1 level.

CONCLUSIONS

Three month follow-up of stable patients with Eisenmenger's syndrome transitioned from sitaxsentan to bosentan revealed improvement of exercise capacity despite significant elevation of ET-1 level. Concurrent increase of LV ejection fraction and pulmonary flow might have contributed to these favourable effects.

The endothelin receptor antagonist bosentan improves peripheral endothelial function in patients with type 2 diabetes mellitus and microalbuminuria: a randomised trial

AIMS/HYPOTHESIS

Endothelial dysfunction is important in the development of vascular complications in diabetes. Patients with type 2 diabetes have increased production of the vasoconstrictor and pro-inflammatory peptide, endothelin-1. Short-term intra-arterial administration of endothelin antagonists improves endothelium-dependent vasodilatation in patients with type 2 diabetes. We tested the hypothesis that oral administration of the dual endothelin receptor antagonist, bosentan, improves peripheral endothelial function in patients with type 2 diabetes and microalbuminuria.

METHODS

This placebo-controlled and double-blind study was performed on 46 patients with type 2 diabetes and microalbuminuria (urine albumin/creatinine ratio >3 mg/mmol) at a medical university department. Patients were randomised to bosentan, 125 mg two times per day (n = 28), or placebo (n = 28) for 4 weeks. The computer-generated randomisation code was kept in sealed envelopes. Patients and people doing examinations or assessing outcomes were blinded. The primary endpoint was change in microvascular endothelium-dependent vasodilatation, based on change in digital reactive hyperaemia index. The secondary endpoint was change in brachial artery flow-mediated vasodilatation.

RESULTS

Reactive hyperaemia index increased from 1.73 ± 0.43 (mean ± SD) at baseline to 2.08 ± 0.59 at follow-up (p < 0.05) in the bosentan group (n = 22), but did not change in the placebo group (1.84 ± 0.49 to 1.87 ± 0.47; n = 24). The change in reactive hyperaemia index from baseline was greater in the bosentan group than in the placebo group (p < 0.05). Nitroglycerine-induced digital hyperaemia was not affected. Brachial artery flow-mediated vasodilatation and blood pressure did not change during treatment.

CONCLUSIONS/INTERPRETATION

Oral treatment of 4 weeks duration with the dual endothelin receptor antagonist, bosentan, improves peripheral endothelial function in patients with type 2 diabetes and microalbuminuria.

Survival of Japanese patients with pulmonary arterial hypertension after the introduction of endothelin receptor antagonists and/or phosphodiesterase type-5 inhibitors

OBJECTIVE

Although endothelin receptor antagonists (ERAs) and phosphodiesterase type 5 (PDE5) inhibitors have become the most commonly used treatments for pulmonary arterial hypertension (PAH) since their introduction in 2005, it remains unknown whether these medications play a significant role in the survival of Japanese patients with PAH.

METHODS

The cardiac catheterization and survival data of 103 PAH patients were retrospectively reviewed. A comparison of survival benefits with regard to the type of PAH was completed in PAH patients diagnosed between 2005 and 2012 and those diagnosed between 1983 and 2004 and in patients undergoing treatment with ERAs and/or PDE5 inhibitors and those being treated with conventional therapy and/or oral beraprost. Although pulmonary vascular resistance (PVR) at baseline differed, the more recent group showed better survival rates compared with those observed in the early group (5-year survival: 70.1% vs. 44.8) (p<0.05). In addition, the survival of PAH patients treated with ERAs and/or PDE5 inhibitors was superior to that of the patients treated without these medications (5- and 8-year survival: 77.8% and 66.7% vs. 39.0% and 37.0%, respectively) (p<0.05), especially in patient with idiopathic and heritable PAH.

CONCLUSION

Superior survival rates are observed in patients with idiopathic and heritable PAH after introduction of ERAs and PDE5 inhibitors, and the use of these drugs provides benefits for survival.

[Chronic kidney disease, new therapeutic approaches]

Despite the use of angiotensin blockers, chronic kidney diseases still progress. New therapeutic approaches aim to strengthen and to complete angiotensin blocker effects. Endothelin receptor antagonists, in addition to angiotensin blockers reduce blood pressure and urinary albumin excretion in diabetic nephropathies but can induce fluid overload. A second therapeutic approach consists in preventing the development of interstitial renal fibrosis which is a prognostic factor of CKD. Transforming growth factor-beta (TGF-beta) plays a major role in this process. Several molecules such as pirfenidone, microARN are in development to block TGF-beta or its downstream signaling pathways. Another approach aims to promote resolution of inflammation and renal repair Interesting experimental results were obtained with tyrosine kinase inhibitors and with methyl of bardoxolone in humans.

Idiopathic pulmonary fibrosis: treatment update

Idiopathic pulmonary fibrosis (IPF) is the most common of the idiopathic interstitial pneumonias. Despite multiple recent clinical trials, there is no strong evidence supporting a survival advantage for any agent in the management of patients with IPF. The limited effectiveness of current treatment regimes has led to a search for novel therapies including antifibrotic strategies. This article reviews the evidence supporting the treatments currently used in the management of IPF.

[Do endothelin receptors antagonists have a place in the treatment of arterial hypertension?]

The discovery in 1988 of endothelin, the most potent human endogenous vasoconstrictor, has opened the race to the discovery of a new weapon against arterial hypertension. The development of the endothelin receptors antagonists (ERAs) and the demonstration of their efficacy in preclinical models initially raised a wave of enthusiasm, which was however tempered due to their unfavorable side effect profile. In this article we will review the phases of the development ERAs, and their current and future place as therapeutic tool against arterial hypertension.

[Digital ulcers in systemic sclerosis: use of endotheline antagonists]

INTRODUCTION

Systemic sclerosis (SSc) is a systemic disease, characterized by fibrosis and vasculopathy, with variable internal organ involvement. Skin is very often involved, namely digital ulcers (DU), seldom treatment resistant, responsible for important functional limitation. The DU can evolve from sclerodactily with superficial ulcers, isquemic lesions, deep necrosis, gangrene, loss of tissue, and consequently, to finger amputation.

METHODS

The authors describe the case of a 36 year old female patient, with SSc diagnosed 6 years previously, with skin, lung and gut manifestations. The patient showed uncontrolled Raynaud's phenomenon (RF), despite the adequate treatment using nifedidpine and general local warming measures, with progressively worsening DU and isquemia, especially in cold seasons. Bosentan, 62.5 mg twice daily was started, and a significant improvement in the peripheral isquemic lesions was achieved. The ulcers' healing was fast, the patient totally recovered function and regained quality of life, and no further lesions developed.

CONCLUSION

The authors review the RF and DU in SSc, as well as the use of bosentan, an endotheline receptor antagonist, and its indications. Although it is not formally approved, the use of bosentan in SS has shown benefits in reducing the incidence of DU, and despite no influence in the healing process, this drug prevents the development of new lesions.