Treatment of pulmonary arterial hypertension with bosentan: from pathophysiology to clinical evidence

Current and investigational drugs in early clinical development for portal hypertension

Introduction

The development of portal hypertension leads to a majority of complications associated with chronic liver disease. Therefore, adequate treatment of portal hypertension is crucial in the management of such patients. Current treatment options are limited and consist mainly of medications that decrease the hyperdynamic circulation, such as non-selective beta blockers, and treatment of hypervolemia with diuretics. Despite these options, mortality rates have not improved over the last two decades. Newer, more effective treatment options are necessary to help improve survival and quality of life in these patients.

Areas covered

Multiple preclinical models and clinical studies have demonstrated potential efficacy of a variety of new treatment modalities. We introduce treatment options including the use of vasodilation promotors, vasoconstriction inhibitors, anticoagulants, antiangiogenics, and anti-inflammatory drugs. We examine the most recent studies for treatment options within these drug classes and offer insights as to which show the most promise in this field.

Methodology

Published studies that identified novel medical treatment options of portal hypertension were searched using PubMed (https://pubmed.ncbi.nlm.nih.gov/). Clinical trials listed in Clinicaltrials.gov were also searched with a focus on more recent and ongoing studies, including those with completed recruitment. Searching with key terms including "portal hypertension" as well as individually searching specific treatment medications that were listed in other publications was carried out. Finally, current societal guidelines and recent review articles relevant to the management of portal hypertension were evaluated, and listed references of interest were included.

Conclusion

Many ongoing early phase studies demonstrate promising results and may shape the field of portal hypertension management in future. As concrete results become available, larger RCTs will be required before making definitive conclusions regarding safety and efficacy and whether or not they can be incorporated into routine clinical practice. Statins, anticoagulants, and PDE inhibitors have been among the most studied and appear to be most promising.

The adrenergic system in pulmonary arterial hypertension: bench to bedside (2013 Grover Conference series)

In heart failure with reduced left ventricular ejection fraction (HFrEF), adrenergic activation is a key compensatory mechanism that is a major contributor to progressive ventricular remodeling and worsening of heart failure. Targeting the increased adrenergic activation with β-adrenergic receptor blocking agents has led to the development of arguably the single most effective drug therapy for HFrEF. The pressure-overloaded and ultimately remodeled/failing right ventricle (RV) in pulmonary arterial hypertension (PAH) is also adrenergically activated, which raises the issue of whether an antiadrenergic strategy could be effectively employed in this setting. Anecdotal experience suggests that it will be challenging to administer an antiadrenergic treatment such as a β-blocking agent to patients with established moderate-severe PAH. However, the same types of data and commentary were prevalent early in the development of β-blockade for HFrEF treatment. In addition, in HFrEF approaches have been developed for delivering β-blocker therapy to patients who have extremely advanced heart failure, and these general principles could be applied to RV failure in PAH. This review examines the role played by adrenergic activation in the RV faced with PAH, contrasts PAH-RV remodeling with left ventricle remodeling in settings of sustained increases in afterload, and suggests a possible approach for safely delivering an antiadrenergic treatment to patients with RV dysfunction due to moderate-severe PAH.

Meta-analysis of randomized controlled trials of bosentan for treatment of pulmonary arterial hypertension

BACKGROUND/AIMS

We assessed the efficacy and safety of bosentan in patients with pulmonary arterial hypertension (PAH).

METHODS

We surveyed randomized controlled trials (RCTs) of the efficacy and safety of bosentan in patients with PAH using MEDLINE, EMBASE, the Cochrane Controlled Trials Register, and manual searches. Meta-analysis of RCTs was performed to determine treatment efficacy and safety outcomes. Results are presented as odds ratios (ORs) or weighted mean differences (WMDs).

RESULTS

Meta-analysis of seven RCTs including a total of 410 patients and 296 controls revealed that the 6-minute work distance was significantly higher in the bosentan group than in the placebo group (WMD, 46.19; 95% confidence interval [CI], 21.20 to 71.19; p = 2.9 × 10(-5)). Compared with the placebo, bosentan significantly reduced the mean pulmonary arterial pressure in patients with PAH (WMD, -6.026; 95% CI, -8.785 to -3.268, p = 1.8 × 10(-6)). The bosentan therapy group worsened less clinically than the placebo group (OR, 0.252; 95% CI, 0.140 to 0.454; p = 4.6 × 10(-7)). The incidence of serious adverse events did not differ between the bosentan and placebo groups (OR, 0.948; 95% CI, 0.556 to 1.614; p = 0.843). However, the results of the abnormal liver function test (LFT) were significantly higher in the bosentan group than in the placebo group (OR, 2.312; 95% CI, 1.020 to 5.241; p = 0.045).

CONCLUSIONS

This meta-analysis shows that bosentan can treat PAH effectively. However, bosentan increased the incidence of abnormal LFT results compared with the placebo.

Survival after the initiation of combination therapy in patients with pulmonary arterial hypertension: an Australian collaborative report

BACKGROUND

  Several cellular pathways are implicated in the pathogenesis of pulmonary arterial hypertension (PAH) and attempts to arrest disease progression with a single drug would not be expected to succeed in the medium term. In clinical practice, combination therapy is often used in patients deteriorating on monotherapy, despite the absence of firm evidence from randomized controlled controls.

METHODS

  From January 2005 to August 2009, 112 patients with World Health Organisation Functional Class (FC) II-IV PAH deteriorating on monotherapy received non-parenteral combination therapy at six Australian PAH expert hospitals. Combination therapy included bosentan, sitaxentan, ambrisentan, iloprost and sildenafil. Data were prospectively collected for survival status, 6-min walk distance, FC and echocardiographic parameters at the start of monotherapy through to commencement of combination therapy and at 6-monthly intervals thereafter.

RESULTS

  After varying periods of monotherapy (18.7±13.4onths), survival estimates on combination therapy were 88%, 71% and 61% for the additional 1, 2 and 3years respectively. Survival on dual therapy in patients with idiopathic PAH/familial PAH was 93% at 1year and 79% at 2years, and for scleroderma-related PAH, 72% at 1 year and 48% at year 2 after initiation of combination therapy. In survivors, dual therapy reversed the deterioration in FC, from 3.1±0.6 on monotherapy to 2.2±0.6 at 12months. Similarly, dual therapy improved 6-min walk distance from 316±119m to 406±129m at 12months, and sequential echocardiography demonstrated a fall in pulmonary artery systolic pressure and improved right ventricular function.

CONCLUSIONS

  Dual non-parenteral therapy appears safe and effective and should be considered for PAH patients who are deteriorating on monotherapy to improve long-term outcomes.

Integrated care and optimal management of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) may occur as an idiopathic process or as a component of a variety of diseases, including connective tissue diseases, congenital heart disease, and exposure to appetite suppressants or infectious agents such as HIV. Untreated, it is a potentially devastating disease; however, diagnosis can be difficult due to the non-specific nature of symptoms during the early stages, and the fact that patients often present to a range of different medical specialties. The past decade has seen remarkable improvements in our understanding of the pathology associated with the condition and the development of PAH-specific therapies with the ability to alter the natural history of the disease. This article reviews the evidence for screening and diagnosis of susceptible patient groups and discusses treatment selection and recommendations based on data available from randomized controlled trials. In addition, due to the complexity of the diagnostic evaluation required and the treatment options available, this review mandates for a multidisciplinary approach to the management of PAH. We discuss the roles and organizational structure of a specialized PAH center in Perth, Western Australia to highlight these issues.

Current understanding of the role of bosentan in inoperable chronic thromboembolic pulmonary hypertension

Chronic thromboembolic pulmonary hypertension may occur in the context of incomplete lysis of acute pulmonary emboli, resulting in the obstruction of pulmonary blood flow, as well as progressive right ventricular dysfunction and failure. The treatment of choice for this condition is surgical removal of the obstructing material. However, in many patients, surgery is not possible due to either an unfavourable distribution of the disease, the development of a concurrent small vessel pulmonary arteriopathy, or the presence of significant comorbid conditions. There is increasing evidence that the medical therapies that are used in other forms of pulmonary hypertension may also be effective in inoperable chronic thromboembolic pulmonary hypertension. This article examines the rationale for the use of the oral dual endothelin receptor antagonist bosentan in this life-threatening condition.

Chemical modification of therapeutic drugs or drug vector systems to achieve targeted therapy: looking for the grail

Most therapeutic drugs distribute to the whole body, which results in general toxicity and poor acceptance of the treatments by patients. The targeted delivery of chemotherapeutics to defined cells, either stromal or cancer cells in cancer lesions, or defined inflammatory cells in immunological disorders, is one of the main challenges and a very active field of research in the development of treatment strategies to minimize side-effects of drugs. Disease-associated cells express molecules, including proteases, receptors, or adhesion molecules, that are different or differently expressed than their normal counterparts. Therefore one goal in the field of targeted therapies is to develop chemically derivatized drugs or drug vectors able to target defined cells via specific recognition mechanisms and also able to overcome biological barriers. This article will review the approaches which have been explored to achieve these goals and will discuss in more detail three examples (i) the use of nanostructures to take advantage of increased vascular permeability in some human diseases, (ii) the targeting of therapeutic drugs to an organ, the brain, protected against foreign molecules by the blood-brain barrier, and (iii) the use of the folate receptor to target either tumor cells or activated macrophages.

Sildenafil for pulmonary arterial hypertension: when blue turns into white

Pulmonary arterial hypertension is a life-threatening, rare disease characterised by vasoconstriction and vascular remodelling of pulmonary artery vessels. Pulmonary arterial hypertension can occur without an obvious cause or can be secondary. Until several years ago, therapeutic approaches were represented mainly by 'conventional therapy' (anticoagulants, calcium channel blockers, diuretics and digoxin, and oxygen therapy). But recently 'specific therapies' (i.e., therapies targeting specific pathogenic pathways) have become available; these are therapies represented by prostacyclin and its derivatives, endothelin receptor antagonists or phosphodiesterase-5 inhibitors. Sildenafil citrate is a phosphodiesterase-5 inhibitor and is the second oral pharmacological agent recently approved for the treatment of pulmonary arterial hypertension. Sildenafil has demonstrated short- and long-term clinical efficacy in the treatment of various forms of pulmonary arterial hypertension, either alone or in combination with other agents, but its safety profile needs further assessment.

Bosentan treatment for pulmonary arterial hypertension related to connective tissue disease: a subgroup analysis of the pivotal clinical trials and their open-label extensions

BACKGROUND

Endothelin-1 is considered to be a central pathogenic factor in connective tissue diseases (CTDs) such as systemic sclerosis (SSc), leading to vasoconstriction, fibrosis, hypertrophy and inflammation. A frequent complication of CTD is pulmonary arterial hypertension (PAH), which has a major effect on functioning and quality of life, and is associated with a particularly poor prognosis.

OBJECTIVE

To present a subgroup analysis that summarises experiences from the pivotal studies and their open-label extensions with the oral dual endothelin-1 receptor antagonist bosentan in patients with PAH and CTD, mostly SSc and lupus erythematosus.

METHODS

66 patients with PAH secondary to CTD, in World Health Organization functional class III or IV, were randomised to two double-blind, placebo-controlled studies and followed up for 12 and 16 weeks, respectively. The primary end point was change in exercise capacity, assessed using the 6-min walk test. In both studies and their extensions, survival was assessed from start of treatment to death or data cut-off and analysed as Kaplan-Meier estimates.

RESULTS

44 patients with PAH secondary to CTD who were treated with bosentan were stable in 6-min walk distance at the end of the study (+19.5 m, 95% confidence interval (CI) -3.2 to 42.2), whereas patients treated with placebo deteriorated (-2.6 m, 95% CI -54.0 to 48.7). 64 patients subsequently received bosentan in an open-label long-term extension study. Mean (standard deviation (SD)) exposure to bosentan was 1.6 (0.9) years, and duration of observation was 1.8 (0.8) years. 8 (16%) patients received epoprostenol as add-on treatment and 7 (14%) after discontinuation of bosentan. Survival in those receiving bosentan was 85.9% after 1 year and 73.4% after 2 years.

CONCLUSION

Short-term bosentan treatment in a subgroup of patients with PAH secondary to CTD seems to have a favourable effect compared with placebo. The long-term follow-up of these patients suggests that first-line bosentan, with the subsequent addition of other PAH treatments if required, is safe for long-term treatment and may have a positive effect on outcome.