Is endothelin targeting finally ready for prime time?

The endothelin family of peptides has long been recognized as a physiological regulator of diverse biological functions and mechanistically involved in various disease states, encompassing, among others, the cardiovascular system, the kidney, and the nervous system. Pharmacological blockade of the endothelin system, however, has encountered strong obstacles in its entry into the clinical mainstream, having obtained only a few proven indications until recently. This translational gap has been attributable predominantly to the relevant side effects associated with endothelin receptor antagonism (ERA), particularly fluid retention. Of recent, however, an expanding understanding of the pathophysiological processes involving endothelin, in conjunction with the development of new antagonists of endothelin receptors or adjustment of their doses, has driven a flourish of new clinical trials. The favorable results of some of them have extended the proven indications for ET targeting to a variety of clinical conditions, including resistant arterial hypertension and glomerulopathies. In addition, on the ground of strong preclinical evidence, other studies are ongoing to test the potential benefits of ERA in combination with other treatments, such as sodium-glucose co-transporter 2 inhibition in fluid retentive states or anti-cancer therapies in solid tumors. Furthermore, antibodies providing long-term blockade of endothelin receptors are under testing to overcome the short half-life of most small molecule endothelin antagonists. These efforts may yet bring new life to the translation of endothelin targeting strategies in clinical practice.

Maximizing the Therapeutic Effect of Endothelin Receptor Antagonists in Pulmonary Fibrosis: A Paradigm for Treating the Disease.

Using a lipopolysaccharide model of acute lung injury, we previously showed that endothelin-1 (ET-1), a potent mediator of vasoconstriction, may act as a "gatekeeper" for the influx of inflammatory cells into the lung. These studies provided a rationale for testing the effect of HJP272, an endothelin receptor antagonist (ERA), in hamster models of pulmonary fibrosis induced by intratracheal instillation of either bleomycin (BLM) or amiodarone (AM). To determine the temporal effects of blocking ET-1 activity, animals were given HJP272 either 1 h before initiation of lung injury or 24 h afterward. The results indicated that pretreatment with this agent caused significant reductions in various inflammatory parameters, whereas post-treatment was ineffective. This finding suggests that ERAs are only effective at a very early stage of pulmonary fibrosis and explains their lack of success in clinical trials involving patients with this disease. Nevertheless, ERAs could serve as prophylactic agents when combined with drugs that may induce pulmonary fibrosis. Furthermore, developing a biomarker for the initial changes in the lung extracellular matrix could increase the efficacy of ERAs and other therapeutic agents in preventing the progression of the disease. While no such biomarker currently exists, we propose the ratio of free to peptide-bound desmosine, a unique crosslink of elastin, as a potential candidate for detecting the earliest modifications in lung microarchitecture associated with pulmonary fibrosis.

Comparative adherence of macitentan versus ambrisentan and bosentan in Australian patients with pulmonary arterial hypertension: a retrospective real-world database study.

AIM: Bosentan, ambrisentan, and macitentan are endothelin receptor antagonists (ERAs), currently available in Australia for treatment of pulmonary arterial hypertension (PAH). This study assessed the comparative adherence of these ERAs for PAH in Australian patients. METHODS: This retrospective, observational study used data for adults with PAH from the Services Australia 10% Pharmaceuticals Benefits Scheme (PBS) dataset (01/2006-10/2020). The primary outcome was treatment adherence (i.e. receiving ≥80% of ERA doses over 12 months). Secondary outcomes were time to treatment change (add-on or switch) and overall survival. RESULTS: The study included 436 patients who took bosentan (n = 200), ambrisentan (n = 69), or macitentan (n = 167). Treatment adherence was significantly greater in patients who received macitentan (65.3%) versus ambrisentan (56.5%) and bosentan (58.0%), with odds ratios (ORs; 95% CI) of 0.51 (0.30-0.88; p = 0.016) for bosentan versus macitentan and 0.48 (0.24-0.96; p = 0.037) for ambrisentan versus macitentan. The median time to treatment change was 47.2 and 43.4 months for bosentan and ambrisentan, respectively (not calculated for macitentan because of insufficient duration of data). LIMITATIONS AND CONCLUSIONS: Real-world data for Australian patients with PAH showed that treatment adherence for ERAs was suboptimal. Adherence was higher for macitentan compared with ambrisentan and bosentan.

Sparsentan: the first and only non-immunosuppressive therapy for the reduction of proteinuria in IgA nephropathy.

INTRODUCTION: IgA nephropathy is one of the most common forms of glomerular disease. Patients with persistent proteinuria are at increased risk of progression to kidney failure. There is a significant need for safe and effective therapies to lower proteinuria in these patients. Sparsentan is a non-immunosuppressive agent that acts as a dual angiotensin and endothelin receptor antagonist. It lowers proteinuria in experimental models of glomerular disease and in affected patients. AREAS COVERED: This review covers the immunological and non-immunological actions of sparsentan in glomerular disease. It reviews the clinical trials that evaluated the impact of the drug in pediatric and adult patients with IgA nephropathy. It places the use of sparsentan in an overall treatment paradigm for the full spectrum of patients with IgA nephropathy including nonspecific renoprotective agents such as inhibitors of the renin-angiotensin-aldosterone axis and SGLT2 transporter and immunosuppressive drugs. The review represents a search of the current literature about the effect of the drug on normal physiology and the pathogenesis of IgA nephropathy. EXPERT OPINION: The safety, tolerability, and therapeutic efficacy of sparsentan have been demonstrated in long-term studies of patients with primary glomerular diseases extending over 5 years. The evidence in support of a beneficial treatment effect of sparsentan is stronger in IgAN than in FSGS. It is anticipated that sparsentan will supplant the use of ACEI or ARB as the first-line therapy to reduce proteinuria prior to the implementation of immunosuppressive agents in patients with IgA nephropathy. It may be combined with other renoprotective drugs like SGLT2 inhibitors. Practice guidelines are needed to promote safe and effective use of this new drug by nephrologists caring for patients with IgAN in all clinical settings.

Clinical course of COPD patients with exercise-induced elevation of pulmonary artery pressure or less severe pulmonary hypertension presenting with respiratory symptoms and the impact of bosentan intervention-prospective, single-center, randomized, parallel-group study.

BACKGROUND: The data on bosentan were lacking for the treatment of exercise-induced elevation of pulmonary artery pressure (eePAP) or less severe PH in COPD. This study was conducted to investigate long-term efficacy and safety of bosentan for the treatment of eePAP or less severe PH in COPD. METHODS: COPD patients diagnosed at this hospital as having COPD (WHO functional class II, III or IV) with eePAP or less severe PH whose respiratory symptoms were stable but remained and gradually progressed even after COPD therapy were randomly assigned in a 1:1 ratio to receive either bosentan or no PH treatment for two years and assessed at baseline and every 6 months for respiratory failure, activities of daily living (ADL), lung and heart functions by right heart catheterization (RHC), and other parameters. RESULTS: A total of 29 patients who underwent RHC for detail examination were enrolled in the current study between August 2010 and October 2018.No death occurred in drug-treated group (n = 14) for 2 years; 5 patients died in untreated group (n = 15). Significant differences were noted between the 2 group in hospital-free survival (686.00 ± 55.87 days vs. 499.94 ± 53.27 days; hazard ratio [HR], 0.18; P = 0.026) and overall survival (727 days vs. 516.36 ± 55.38 days; HR, 0.095; P = 0.030) in all causes of death analysis, but not in overall survival in analysis of respiratory-related death. Bosentan was not associated with increased adverse events including requiring O2 inhalation. CONCLUSIONS: This study suggested that the prognosis for COPD patients with eePAP or less severe PH presenting with respiratory symptoms was very poor and that bosentan tended to improve their prognosis and suppress ADL deterioration without worsening respiratory failure. TRIAL REGISTRATION: This study was registered with UMIN-CTR Clinical Trial as UMIN000004749 . First trial registration at 18/12/2010.

Endothelin System in Hypertension and Chronic Kidney Disease.

ET (endothelin) is a powerful vasoconstrictor 21-amino acid peptide present in many tissues, which exerts many physiological functions across the body and participates as a mediator in many pathological conditions. ETs exert their effects through ETA and ETB receptors, which can be blocked by selective receptor antagonists. ETs were shown to play important roles among others, in systemic hypertension, particularly when resistant or difficult to control, and in pulmonary hypertension, atherosclerosis, cardiac hypertrophy, subarachnoid hemorrhage, chronic kidney disease, diabetic cardiovascular disease, scleroderma, some cancers, etc. To date, ET antagonists are only approved for the treatment of primary pulmonary hypertension and recently for IgA nephropathy and used in the treatment of digital ulcers in scleroderma. However, they may soon be approved for the treatment of patients with resistant hypertension and different types of nephropathy. Here, the role of ETs is reviewed with a special emphasis on participation in and treatment of hypertension and chronic kidney disease.

[Targeted therapy for pulmonary arterial hypertension in patients without comorbidities]. / Gezielte medikamentöse Therapie der pulmonalarteriellen Hypertonie bei Patient*innen ohne Komorbiditäten.

The 2022 guidelines on pulmonary hypertension from the European Society of Cardiology (ESC) and the European Respiratory Society (ERS) provide therapeutic strategies that account for the variability in the clinical presentation of newly diagnosed patients. We summarize treatment recommendations for pulmonary arterial hypertension (PAH) in patients without significant comorbidities, particularly for idiopathic, hereditary, drug/toxin-induced, or connective tissue disease-associated PAH. In this group of patients, multidimensional assessments for short-term mortality risk guide initial treatment decisions and treatment decisions during follow-up. Upfront dual combination therapy (phosphodiesterase type-5 inhibitor and endothelin receptor antagonist) is recommended for low- and intermediate-risk patients, and triple therapy including a parenteral prostacyclin should be considered in high- or intermediate-high-risk patients. If a low or intermediate-low-risk profile cannot be achieved during therapy, sequential add-on therapy escalation with parenteral prostacyclin or a prostacyclin receptor agonist should be considered, and switching from a phosphodiesterase type-5 inhibitor to a guanylate cyclase stimulator may also be considered.

[Pulmonary hypertension - The new ESC guideline]. / Pulmonale Hypertonie ­ Die neue ESC-Leitlinie.

The current guidelines on the diagnosis and treatment of pulmonary hypertension (PH) contain several important new aspects. The definition of PH is changed to a mean pulmonary arterial pressure (mPAP) of >20mmHg in combination with PVR threshold value of >2 Wood units to a define a precapillary component. The clinical classification of PH still distinguishes 5 main groups. The diagnostic algorithm begins with the evaluation of dyspnea in primary care and early referral of patients with suspected PAH (group I), CTEPH (group IV) or severe PH of other groups.Initial treatment planning in PAH is guided by complex risk assessment in 3 risk levels, follow-up assessment is performed using 3 parameters (WHO-FC, NT-proBNP, and 6MWD) with 4 risk levels or individually in patients with comorbidities.For low or intermediate risk patients, initial combination therapy with a phosphodiesterase type 5 inhibitor and an endothelin receptor antagonist is recommended. In high-risk patients, initial triple combination therapy with additional prostacyclin analogues should be considered.Diagnosis and treatment of CTEPH including pulmonary endarterectomy, medical therapy and pulmonary balloon angioplasty should be carried out in CTEPH centers.Patients with severe PH (PVR >5WE) due to PH group II, III or V should be referred to the PH center for study inclusion or individual therapy.

A case-control study of phosphodiesterase-5 inhibitor use and Alzheimer's disease and related dementias among male and female patients aged 65 years and older supporting the need for a phase III clinical trial.

BACKGROUND: Phosphodiesterase-5 inhibitors (PDE5i) have been evaluated as a novel treatment for Alzheimer's disease and related dementias (ADRD), but two recent cohort studies have offered opposing conclusions. METHODS: We performed an unmatched case-control study using electronic medical records from a large healthcare system to evaluate the association of PDE5i use and ADRD in patients ≥65 years old. RESULTS: Odds of PDE5i exposure were 64.2%, 55.7%, and 54.0% lower in patients with ADRD than controls among populations with erectile dysfunction, benign prostatic hyperplasia, and pulmonary hypertension, respectively. We observed odds ratios less than unity among males and females and with exposure to the PDE5i sildenafil (Viagra®) and tadalafil (Cialis®). We also evaluated the odds of exposure to two other common treatments for pulmonary hypertension: endothelin receptor antagonists (ERA) and calcium channel blockers (CCB). The odds of ERA exposure were 63.2% lower, but the odds of CCB exposure were 30.7% higher, in patients with ADRD than controls among the population with pulmonary hypertension. CONCLUSIONS: Our results reconcile the opposing conclusions from the previous observational studies and support further research into using PDE5i for prevention and treatment of ADRD.

Stem cell therapy in pulmonary hypertension: current practice and future opportunities.

Pulmonary hypertension (PH) is a progressive disease characterised by elevated pulmonary arterial pressure and right-sided heart failure. While conventional drug therapies, including prostacyclin analogues, endothelin receptor antagonists and phosphodiesterase type 5 inhibitors, have been shown to improve the haemodynamic abnormalities of patients with PH, the 5-year mortality rate remains high. Thus, novel therapies are urgently required to prolong the survival of patients with PH. Stem cell therapies, including mesenchymal stem cells, endothelial progenitor cells and induced pluripotent stem cells, have shown therapeutic potential for the treatment of PH and clinical trials on stem cell therapies for PH are ongoing. This review aims to present the latest preclinical achievements of stem cell therapies, focusing on the therapeutic effects of clinical trials and discussing the challenges and future perspectives of large-scale applications.

Dual Endothelin Antagonism with Aprocitentan as a Novel Therapeutic Approach for Resistant Hypertension.

PURPOSE OF REVIEW: Resistant hypertension (RH) defined as uncontrolled blood pressure despite the use of a combination of a renin-angiotensin system blocker, a calcium channel blocker, and a diuretic at maximally tolerated doses is associated with a substantially increased risk of cardiovascular and renal events. Despite targeting relevant pathophysiological pathways contributing to elevated blood pressure, approximately 10-15% of hypertensive patients remain above recommended blood pressure targets. Further optimization of blood pressure control is particularly challenging in patient populations who frequently present with RH such as elderly and patients with chronic kidney disease, due to the unfavorable safety profile of the recommended fourth-line therapy with mineralocorticoid receptor antagonists. This review explores the potential role of endothelin antagonists as an alternative fourth-line therapy. RECENT FINDINGS: Despite the well-described role of the endothelin pathway in the pathogenesis of hypertension, it is currently not targeted therapeutically. Recently however, main outcome data from the PRECISION study, a randomized placebo-controlled phase 3 trial, in patients with RH on guideline-recommended standardized single-pill background therapy convincingly demonstrated the safety and blood pressure-lowering efficacy of the dual endothelin antagonist Aprocitentan. Findings from the phase 3 PRECISION study could signify a turning point in the utilization of endothelin receptor antagonists as a standard treatment for patients with RH.

Aprocitentan: A new development of resistant hypertension.

As the blood pressure threshold for commencing antihypertensive treatment diminishes, the cohort suffering from resistant hypertension (RH) correspondingly expands. Notwithstanding the availability of known antihypertensive medications, there exists a conspicuous lacuna in therapeutic options specifically intended for the management of RH. Currently, aprocitentan is the sole endothelin receptor antagonist (ERA) under development for addressing this pressing clinical challenge. Aprocitentan (ACT-132577), deriving its active form as a metabolite of macitentan, demonstrates oral potency as a dual endothelin (ET) receptor antagonist. This compound effectively obstructs the binding of endothelin-1 (ET-1) to both ETA and ETB receptors, exhibiting an inhibitory potency ratio of 1:16. Clinical investigation of aprocitentan has advanced to phase 3 trials, yielding promising preliminary outcomes.

Management of Pulmonary Arterial Hypertension.

Pulmonary arterial hypertension (PAH) is a rare pulmonary vascular disease characterized by progressive pulmonary arterial remodeling, increased pulmonary vascular resistance, right ventricular dysfunction, and reduced survival. Effective therapies have been developed that target three pathobiologic pathways in PAH: nitric oxide, endothelin-1, and prostacyclin. Approved therapies for PAH include phosphodiesterase type-5 inhibitors, soluble guanylate cyclase stimulators, endothelin receptor antagonists, prostacyclin analogs, and prostacyclin receptor agonists. Management of PAH in the modern era incorporates multidimensional risk assessment to guide the use of these medications. For patients with PAH and without significant comorbidities, current guidelines recommend two oral medications (phosphodiesterase type-5 inhibitor and endothelin receptor antagonist) for low- and intermediate-risk patients, with triple therapy including a parenteral prostacyclin to be considered in those at high or intermediate-high risk. Combination therapy may be poorly tolerated and less effective in patients with PAH and cardiopulmonary comorbidities. Thus, a single-agent approach with individualized decisions to add-on other PAH therapies is recommended in older patients and those with significant comorbid conditions. Management of PAH is best performed in multidisciplinary teams located in experienced centers. Other core pillars of PAH management include supportive and adjunctive treatments including oxygen, diuretics, rehabilitation, and anticoagulation in certain patients. Patients with PAH who progress despite optimal treatment or who are refractory to best medical care should be referred for lung transplantation, if eligible. Despite considerable progress, PAH is often fatal and new therapies that reverse the disease and improve outcomes are desperately needed.

Insights into Endothelin Receptors in Pulmonary Hypertension.

Pulmonary hypertension (PH) is a disease which affects the cardiopulmonary system; it is defined as a mean pulmonary artery pressure (mPAP) > 20 mmHg as measured by right heart catheterization at rest, and is caused by complex and diverse mechanisms. In response to stimuli such as hypoxia and ischemia, the expression and synthesis of endothelin (ET) increase, leading to the activation of various signaling pathways downstream of it and producing effects such as the induction of abnormal vascular proliferation during the development of the disease. This paper reviews the regulation of endothelin receptors and their pathways in normal physiological processes and disease processes, and describes the mechanistic roles of ET receptor antagonists that are currently approved and used in clinical studies. Current clinical researches on ET are focused on the development of multi-target combinations and novel delivery methods to improve efficacy and patient compliance while reducing side effects. In this review, future research directions and trends of ET targets are described, including monotherapy and precision medicine.

Prescribing of endothelin receptor antagonists and riociguat in women of childbearing age in a large German claims database study.

Use of endothelin receptor antagonists (ERAs) and riociguat, approved for treatment of pulmonary hypertension (PH), is contraindicated during pregnancy due to reported teratogenicity in animals. We aimed to investigate prescribing of these drugs in girls/women of childbearing age and to explore - as a secondary aim - the occurrence of pregnancies exposed to these drugs. Using the German Pharmacoepidemiological Research Database (GePaRD, claims data from 20% of the German population) we conducted cross-sectional analyses to determine prescribing prevalence of ERAs and riociguat between 2004 and 2019 and to characterize users and prescribing patterns. In a cohort analysis, we assessed the occurrence of pregnancies exposed to these drugs in the critical time window. Overall, we identified 407 women with ≥ 1 dispensation of bosentan between 2004 and 2019; the respective number was 73 for ambrisentan, 182 for macitentan, 31 for sitaxentan, and 63 for riociguat. In nearly all years, more than 50% of the girls/women were ≤ 40 years. Age-standardized prevalence was highest for bosentan (0.04/1000) in 2012 and 2013, followed by macitentan (0.03/1000) in 2018 and 2019. We observed 10 exposed pregnancies: 5 to bosentan, 3 to ambrisentan, and 2 to macitentan. The increased prevalence of macitentan and riociguat from 2014 onwards might reflect changes in PH treatment. Even though PH is a rare disease and pregnancy should be avoided in women with PH, particularly if they use ERAs, we identified pregnancies exposed to ERAs. Multi-database studies will be needed to assess the risk of these drugs on the unborn child.

Advances in the discovery of drugs that treat pulmonary arterial hypertension.

INTRODUCTION: Distal pulmonary arterial remodeling and elevated pulmonary vascular resistance are characteristic of pulmonary arterial hypertension (PAH). Current approved vasodilator-specific PAH therapy that includes phosphodiesterase-5 inhibitors, soluble guanylate cyclase stimulators, endothelin receptor antagonists, and prostanoids has demonstrated dramatic enhancement in functional capacity, quality of life, and invasive hemodynamics. However, none of these treatments are curative, underscoring the need to identify new pathophysiologic signaling pathways. AREAS COVERED: The author provides a comprehensive review on current knowledge and recent development in the understanding of PAH. Furthermore, the author discusses PAH potential genetic causes as well as novel molecular signaling pathways. This article also reviews the currently approved PAH specific therapy based on pivotal clinical trials and ongoing clinical trials using novel compounds that specifically target PAH pathogenesis. EXPERT OPINION: The discovery of novel signaling pathways - growth factors, tyrosine kinases, BMPs, estrogen, and serotonin - involved in the PAH pathobiology will lead within the next 5 years to the approval of new therapeutic agents targeting these different pathways. If proven beneficial, these new agents may reverse or at least prevent the progression of this devastating and lethal disease.

Treatment of digital ulcers in systemic sclerosis: recent developments and future perspectives.

Digital ulcers (DUs) comprise the main manifestation of vasculopathy and are a major cause of disability in patients with systemic sclerosis (SSc). A literature search in Web of Science, PubMed and Directory of Open Access Journals was performed in December 2022 to identify articles published in the last decade regarding the management of DUs. Prostacyclin analogues, endothelin antagonists and phosphodiesterase 5 inhibitors have shown promising results both as a stand-alone treatment and in combination for the treatment of existing and prevention of new DUs. Moreover, autologous fat grafting and botulinum toxin injections, although not readily available, can be of use in recalcitrant cases. Many investigational treatments with promising results could pave the way for a paradigm shift in the treatment of DUs in the future. Despite these recent advances, challenges remain. Better-designed trials are of paramount importance to optimise DU treatment in the years to come. Key Points • DUs are a major cause of pain and reduced quality of life in patients with SSc. • Prostacyclin analogues and endothelin antagonists have shown promising results both as a stand-alone treatment and in combination for the treatment of existing and prevention of new DUs. • In the future, a combination of more powerful vasodilatory drugs, perhaps in conjunction with topical approaches, may improve outcomes.