Endothelin Receptor Antagonist Research Articles

Effects of Bosentan on Hypoxia, Inflammation and Oxidative Stress in Experimental Blunt Thoracic Trauma Model.

Background and Objectives: In this study, we aimed to investigate the effects of bosentan, an endothelin receptor antagonist, on endothelin-1 (ET-1), hypoxia-inducible factor-1 (HIF-1), nuclear factor-kappa B (NF-κB), and tumor necrosis factor (TNF)-α as inflammation markers, pro-oxidant antioxidant balance (PAB), and total antioxidant capacity (TAC) levels as oxidative stress parameters in lung tissues of rats in an experimental model of pulmonary contusion (PC) induced by blunt thoracic trauma. Materials and Methods: Thirty-seven male Sprague-Dawley rats were divided into five groups. C: The control group (n = 6) consisted of unprocessed and untreated rats. PC3 (n = 8) underwent 3 days of PC. PC-B3 (n = 8) received 100 mg/kg bosentan and was given orally once a day for 3 days. The PC7 group (n = 7) underwent 7 days of PC, and PC-B7 (n = 8) received 100 mg/kg bosentan and was given orally once a day for 7 days. Results: ET-1, NF-κB, TNF-α, HIF-1α, and PAB levels were higher, while TAC activity was lower in all groups compared with the control (p < 0.05). There was no significant difference in ET-1 and TNF-α levels between the PC-B3 and PC-B7 groups and the control group (p < 0.05), while NF-κB, HIF-1α, and PAB levels were still higher in both the PC-B3 and PC-B7 groups than in the control group. Bosentan decreased ET-1, NF-κB, TNF-α, HIF-1α, and PAB and increased TAC levels in comparison to the nontreated groups (p < 0.05). Conclusions: Bosentan decreased the severity of oxidative stress in the lungs and reduced the inflammatory reaction in rats with PC induced by blunt thoracic trauma. This suggests that bosentan may have protective effects on lung injury mechanisms by reducing hypoxia, inflammation, and oxidative stress. If supported by similar studies, bosentan can be used in both pulmonary and emergency clinics to reduce ischemic complications, inflammation, and oxidative stress in some diseases that may be accompanied by ischemia.

Utilizing phospholipid as an amphiphilic carrier for solid dispersion of ambrisentan: formulation and evaluation

ABSTRACT: The partial water solubility of ambrisentan poses a challenge to its oral administration despite being the second oral endothelin A-receptor antagonist approved in the United States. In this study, we aimed to improve ambrisentan’s solubility and bioavailability using an amphiphilic phospholipid carrier. Phospholipids, with their glycerol-bound, phosphorus-containing amphiphilic nature, are known to prolong drug lifespan by facilitating drug penetration across cell membranes through hydrogen bonds or van der Waals interactions. Moreover, phospholipid compounds have been shown to significantly enhance drug solubility, permeability, and bioavailability in various studies. We optimized the ratios of ambrisentan and phospholipid carriers (1:1, 1:3, and 1:5) based on saturation and phase solubility experiments. Solid dispersion was prepared using the solvent evaporation technique. Differential scanning calorimetry (DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses confirmed the conversion of ambrisentan from a crystalline to an amorphous form in the solid dispersion. The solubility of ambrisentan in the solid dispersion increased by 13-fold with a 1:5 ratio of ambrisentan to phospholipid carrier. The release profile indicated rapid release of the active substance within the first 15 min, corresponding to the peak phospholipid concentration. Pharmacokinetic studies demonstrated higher bioavailability of the medicine compared to the pure drug. This study suggests that phospholipids can effectively enhance drug solubility and bioavailability in solid dispersion systems.

Can Combination Therapy with Endothelin Receptor Antagonist and PDE5 Inhibitors Prevent Echocardiographic Findings Suspicious for Pulmonary Arterial Hypertension? Description of a Real-Life Case Series.

To retrospectively evaluate the incidence rate (IR) of elevated echocardiographic estimated systolic pulmonary artery pressure (sPAP), suspected for pulmonary hypertension (PH), in systemic sclerosis (SSc) patients after the introduction of a combination therapy with bosentan and sildenafil for treatment or prevention of digital ulcers. Patients attending the Scleroderma Unit of the Universital Hospital of Careggi from July 2010 to July 2023 were enrolled. Patients older than 18 years old with a history of digital ulcers, treated with bosentan and sildenafil in combination for at least 12 months, were included. Patients with a diagnosis of PH preceding the introduction of the therapy were excluded. Demographical data, disease duration, laboratoristic, and instrumental data (pulmonary function tests, echocardiographic estimation of sPAP, and ultrasonographic value of renal resistive index) were collected. The IR of echocardiographic signs suspected of pulmonary hypertension and their 95% confidence interval were calculated in events/1000 patients-years. Thirty-five patients were enrolled; the mean disease duration was 12.82 years (SD 5.92). The mean duration of the combination treatment was 81.03 (SD 43.1.3) months, and the total at-risk time was 2674 months. Two patients (5.7%) presented echocardiographic signs of PH (sPAP 50 mmHg and 40 mmHg); the IR was calculated to be 9/1000 patients-years (95% CI 7.95-10.12). In one of the two patients, right heart catheterism (RHC) excluded PAH, while the other patient refused to undergo RHC, and PAH could not be confirmed/excluded. The stability of PFTs and echocardiographic sPAP was observed during the observation time. The results of this retrospective study suggest that combination therapy with endothelin receptor antagonists and phosphodiesterase-5 (PDE5) inhibitors could help in preventing PAH in SSc; prospective case-control studies on a larger population are needed to improve knowledge in this field.

Effects of Zibotentan Alone and in Combination with Dapagliflozin on Fluid Retention in Patients with CKD.

Endothelin receptor antagonists (ERAs) reduce albuminuria but are limited by fluid retention risk, particularly in patients with chronic kidney disease (CKD). Combining ERAs with sodium-glucose cotransporter 2 (SGLT2) inhibitors, which have diuretic effects, offers a promising strategy to mitigate fluid retention. In this post-hoc analysis of the ZENITH-CKD trial, we assessed fluid dynamics in patients with CKD treated with the ERA zibotentan alone, and in combination with the SGLT2 inhibitor dapagliflozin. In ZENITH-CKD, 508 patients with CKD (estimated glomerular filtration rate ≥ 20 mL/min/1.73m2 and a urinary albumin-to-creatinine ratio of 150-5000 mg/g) were randomized to treatment with placebo, dapagliflozin 10 mg plus placebo, zibotentan (0.25, 1.5 or 5 mg) plus dapagliflozin 10 mg and zibotentan 5 mg plus placebo. We evaluated correlations between changes in fluid retention markers and bioimpedance-measured extracellular fluid (ECF) in response to zibotentan treatment. We used Cox proportional hazards regression to assess the association between zibotentan/dapagliflozin treatment, baseline characteristics, and fluid retention, and the relationship between zibotentan plasma exposure and fluid retention. After 3 weeks of treatment with zibotentan 0.25, 1.5 or 5 mg plus dapagliflozin 10 mg, changes in body weight (β=0.36 [95%CI 0.26,0.45]) per kg, B-type natriuretic peptide (β=0.38 [95%CI 0.22, 0.54]) per doubling, and hemoglobin (β=-0.29 [95%CI -0.48, -0.10]) per g/dL were independently associated with changes in ECF. Higher doses of zibotentan were associated with significantly higher risk of fluid retention compared to dapagliflozin alone (zibotentan 5 mg HR 8.50 (95%CI 3.40, 21.30). The hazard ratio attenuated when zibotentan was combined with dapagliflozin (HR zibotentan/dapagliflozin 5/10 mg 3.09 [95%CI 1.08, 8.80], zibotentan/dapagliflozin 1.5/10 mg 2.70 [95%CI 1.44, 5.07] and zibotentan/dapagliflozin 0.25/10 mg HR 1.21 [95%CI 0.50, 2.91]). The risk of fluid retention was higher with higher zibotentan exposure and lower eGFR. High doses of zibotentan were associated with a higher risk of fluid retention, which was attenuated with lower doses and the addition of dapagliflozin.

Pharmacological Management of Hypertension: New Drugs and Mechanisms

Hypertension remains a leading global health challenge, contributing significantly to morbidity and mortality due to cardiovascular diseases. Traditional antihypertensive therapies, while effective for many, often fall short in certain populations, necessitating the development of novel pharmacological agents. This review explores recent advancements in the pharmacological management of hypertension, focusing on new drug classes and their mechanisms of action. We discuss innovations such as angiotensin receptor-neprilysin inhibitors (ARNIs), endothelin receptor antagonists, and sodium-glucose co-transporter 2 (SGLT2) inhibitors, highlighting their clinical efficacy and safety profiles. Additionally, we examine emerging mechanisms targeted by these drugs, including modulation of the renin-angiotensin-aldosterone system (RAAS), endothelial function enhancement, and metabolic pathway alteration. The review also addresses the potential for personalized medicine approaches in optimizing hypertension management. By elucidating these advancements, we aim to provide a comprehensive understanding of the future directions in hypertensive therapy, paving the way for improved patient outcomes through more precise and effective treatment strategies.

Recent developments in the management of resistant hypertension: focus on endothelin receptor antagonists.

Resistant hypertension is characterized by the inability of guideline-recommended triple combination therapy to control blood pressure(BP) to target. It is associated with a significantly increased risk of adverse outcomes. Despite abundant preclinical evidence supporting thecritical role of the endothelin pathway in resistant hypertension (RH), clinical implementation of endothelin antagonists for the treatment of hypertension was hindered by various factors. Recently, the novel dual endothelin-receptor antagonist aprocitentan was tested in individuals with resistant hypertension in the PRECISION trial and provided compelling evidence supporting both short and longer-term safety and clinically meaningful and sustained BP lowering efficacy.These findings resulted in therecent regulatory approval of aprocitentanby the FDA. Aprocitentan may be a particularly useful antihypertensive option for individuals with advanced age, chronic kidney disease, and albuminuria.

Removing the FDA’s Boxed Hepatotoxicity Warning and Liver Function Testing Requirement for Ambrisentan

Endothelin receptor antagonists are first-line therapy for pulmonary arterial hypertension (PAH). The first 2 agents approved in the class, bosentan and ambrisentan, initially carried boxed warnings for hepatotoxicity and required monthly liver function tests (LFTs) as part of a risk evaluation and mitigation strategy (REMS); however, in 2011, as further safety data emerged on ambrisentan, the boxed hepatotoxicity warning and LFT requirements were removed. To analyze changes in the use of and LFT monitoring for ambrisentan and bosentan after changes to the ambrisentan labeling and REMS. This serial cross-sectional study used data from 3 longitudinal health care insurance claims databases-Medicaid, Optum's deidentified Clinformatics Data Mart, and Merative Marketscan-to perform an interrupted time series analysis of prescription fills and LFTs for patients taking ambrisentan and bosentan. Participants were patients filling prescriptions for ambrisentan and bosentan from July 1, 2007, to December 31, 2018. Data analysis was performed from April 2021 to August 2023. Removal of the boxed warning for hepatotoxicity and the REMS LFT monitoring requirements on ambrisentan in March 2011. The primary outcomes were use of ambrisentan (ie, individuals with at least 1 dispensing per 1 000 000 individuals enrolled in the 3 datasets) vs bosentan and LFT monitoring (ie, proportion of initiators with at least 1 ordered test) before initiation and before the first refill. A total of 10 261 patients received a prescription for ambrisentan during the study period (7442 women [72.5%]; mean [SD] age, 52.6 [17.6] years), and 11 159 patients received a prescription for bosentan (7931 women [71.1%]; mean [SD] age, 47.7 [23.7] years). Removal of the ambrisentan boxed hepatotoxicity warning and LFT monitoring requirement was associated with an immediate increase in the use of ambrisentan (1.50 patients per million enrollees; 95% CI, 1.08 to 1.92 patients per million enrollees) but no significant change in the use of bosentan. There were reductions in recorded LFTs before drug initiation (13.1% absolute decrease; 95% CI, -18.2% to -8.0%) and before the first refill (26.4% absolute decrease; 95% CI, -34.4% to -18.5%) of ambrisentan but not bosentan. In this serial cross-sectional study of ambrisentan, labeling changes and removal of the REMS-related LFT requirement were associated with shifts in prescribing and testing behavior for ambrisentan but not bosentan. Further clinician education may be needed to maximize the benefits of REMS programs and labeling warnings designed to ensure the safe administration of high-risk medications.

The effect of endothelin a receptor inhibition and biological sex on cutaneous microvascular function in non-Hispanic Black and White young adults.

The purpose of this study was to investigate whether endothelin-A receptor (ETAR) inhibition in non-Hispanic Black (NHB) and White (NHW) young adults depends on biological sex. We recruited females during low hormone (n = 22) and high hormone (n = 22) phases, and males (n = 22). Participants self-identified as NHB (n = 33) or NHW (n = 33). Participants were instrumented with two microdialysis fibers: (1) lactated Ringer's (control) and (2) 500 nM BQ-123 (ETAR antagonist). Local heating was used to elicit cutaneous vasodilation, and an infusion of 20 mM L-NAME to quantify NO-dependent vasodilation. At control sites, NO-dependent vasodilation was lowest in NHB males (46 ± 13 %NO) and NHB females during low hormone phases (47 ± 12 %NO) compared to all NHW groups. Inhibition of ETAR increased NO-dependent vasodilation in NHB males (66 ± 13 %NO), in both groups of females during low hormone phases (NHW, control: 64 ± 12 %NO, BQ-123: 85 ± 11 %NO; NHB, BQ-123: 68 ± 13 %NO), and in NHB females during high hormone phases (control: 61 ± 11 %NO, BQ-123: 83 ± 9 %NO). There was no effect for ETAR inhibition in NHW males or females during high hormone phases. These data suggest the effect of ETAR inhibition on NO-dependent vasodilation is influenced by biological sex and racial identity.

Semaglutide in Chronic Kidney Disease: Great Enthusiasm. But How Does It Work?

Chronic Kidney Disease (CKD) is a clinical condition characterized by the progressive loss of kidney function. 10% of the world's population is affected by this condition, which represents the fifth leading cause of death globally. Furthermore, CKD is associated with increased risk of fatal and non-fatal cardiovascular events, and progression to end-stage renal disease. Over the last twenty years, an exponential growth in its prevalence and incidence has been observed. For this reason, various drugs have been developed and implemented in clinical practice, with various mechanisms, with the aim of reducing and minimizing this dramatic "cardio-renal" risk. These include SGLT2 inhibitors, mineralocorticoid receptor antagonists, and endothelin receptor antagonists. However, a large proportion of CKD patients do not respond sufficiently to these treatments. GLP-1 receptor agonists represent a class of antidiabetic and nephroprotective drugs that are very promising in improving the prognosis of patients with CKD, especially if associated with one of the above-mentioned classes. In this article, we discuss the direct and indirect mechanisms through which one of the GLP-1 agonists, semaglutide, ensures nephro- and cardioprotection in patients with CKD and type 2 diabetes.

Liver injury associated with endothelin receptor antagonists: a pharmacovigilance study based on FDA adverse event reporting system data.

Endothelin receptor antagonists are commonly used in clinical practice, with concerns about their hepatotoxicity. This study aimed to conduct a comprehensive pharmacovigilance study based on FDA adverse event reporting system data to evaluate the possible association between endothelin receptor antagonists and drug-induced liver injury. Adverse event reports from FDA adverse event reporting system between January 2004 and December 2022 were analyzed. Disproportionality algorithms, including reporting odds ratio and information component, were used to evaluate the association between endothelin receptor antagonists and liver injury. Sex- and age-stratified analyses of drug-induced liver injury events were also conducted in relation to endothelin receptor antagonists. Significant associations between bosentan, macitentan, and liver injury were identified. Bosentan showed a strong link with liver injury, with reporting odds ratios for cholestatic injury at 7.59 (95% confidence interval: 6.90-8.35), hepatocellular injury at 5.63 (5.29-6.00), and serious drug-related hepatic disorders events at 1.33 (1.24-1.43). Drug-induced liver injury signals associated with bosentan were detected in all age groups. Macitentan was associated with liver injury, with reporting odds ratios for hepatic failure at 1.64 (1.39-1.94), cholestatic injury at 1.62 (1.43-1.83), and serious drug-related hepatic disorders events at 1.40 (1.29-1.51). No drug-induced liver injury signal was detected for ambrisentan, and no significant sex differences were observed in drug-induced liver injury events. Both bosentan and macitentan are associated with liver injury. Routine monitoring of serum aminotransferase levels is recommended, especially in patients at higher risk of liver injury. Further research into drug-drug interactions involving endothelin receptor antagonists is warranted.

Therapeutic approaches for pulmonary hypertension in patients with chronic kidney disease.

Pulmonary hypertension is a common comorbidity in patients with chronic kidney disease (CKD), but therapeutic options are limited. We discuss the epidemiology of pulmonary hypertension in patients with CKD and review therapies for pulmonary hypertension with a focus on emerging treatments for pulmonary arterial hypertension (PAH). The definition of pulmonary hypertension has been updated to a lower threshold of mean pulmonary artery pressures of more than 20 mmHg, potentially leading to more patients with CKD to qualify for the diagnosis of pulmonary hypertension. Endothelin receptor antagonists, a class of medications, which demonstrated efficacy in patients with PAH, have been shown to slow progression of CKD, but their efficacy in lowering pulmonary artery pressures and their effects on reducing cardiovascular mortality in this population remains unproven. Sotatercept, a novel activin signaling inhibitor, which was previously studied in dialysis patients has been shown to increase exercise capacity in patients with PAH. These studies may lead to new specific therapies for pulmonary hypertension in patients with CKD. Pulmonary hypertension is common in patients with CKD. Although our understanding of factors leading to pulmonary hypertension in this population have evolved, evidence supporting disease-specific therapy in CKD is limited arguing for larger, long-term studies.

Hypertension and Heart Failure: From Pathophysiology to Treatment.

Hypertension represents one of the primary and most common risk factors leading to the development of heart failure (HF) across the entire spectrum of left ventricular ejection fraction. A large body of evidence has demonstrated that adequate blood pressure (BP) control can reduce cardiovascular events, including the development of HF. Although the pathophysiological and epidemiological role of hypertension in the development of HF is well and largely known, some critical issues still deserve to be clarified, including BP targets, particularly in HF patients. Indeed, the management of hypertension in HF relies on the extrapolation of findings from high-risk hypertensive patients in the general population and not from specifically designed studies in HF populations. In patients with hypertension and HF with reduced ejection fraction (HFrEF), it is recommended to combine drugs with documented outcome benefits and BP-lowering effects. In patients with HF with preserved EF (HFpEF), a therapeutic strategy with all major antihypertensive drug classes is recommended. Besides commonly used antihypertensive drugs, different evidence suggests that other drugs recommended in HF for the beneficial effect on cardiovascular outcomes exert advantageous blood pressure-lowering actions. In this regard, type 2 sodium glucose transporter inhibitors (SGLT2i) have been shown to induce BP-lowering actions that favorably affect cardiac afterload, ventricular arterial coupling, cardiac efficiency, and cardiac reverse remodeling. More recently, it has been demonstrated that finerenone, a non-steroidal mineralocorticoid receptor antagonist, reduces new-onset HF and improves other HF outcomes in patients with chronic kidney disease and type 2 diabetes, irrespective of a history of HF. Other proposed agents, such as endothelin receptor antagonists, have provided contrasting results in the management of hypertension and HF. A novel, promising strategy could be represented by small interfering RNA, whose actions are under investigation in ongoing clinical trials.

The Anti-Atherosclerotic Effects of Endothelin Receptor Antagonist, Bosentan, in Combination with Atorvastatin-An Experimental Study.

Bosentan, an endothelin receptor antagonist (ERA), has potential anti-atherosclerotic properties. We investigated the complementary effects of bosentan and atorvastatin on the progression and composition of the atherosclerotic lesions in diabetic mice. Forty-eight male ApoE-/- mice were fed high-fat diet (HFD) for 14 weeks. At week 8, diabetes was induced with streptozotocin, and mice were randomized into four groups: (1) control/COG: no intervention; (2) ΒOG: bosentan 100 mg/kg/day per os; (3) ATG: atorvastatin 20 mg/kg/day per os; and (4) BO + ATG: combined administration of bosentan and atorvastatin. The intra-plaque contents of collagen, elastin, monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor-a (TNF-a), matrix metalloproteinases (MMP-2, -3, -9), and TIMP-1 were determined. The percentage of lumen stenosis was significantly lower across all treated groups: BOG: 19.5 ± 2.2%, ATG: 12.8 ± 4.8%, and BO + ATG: 9.1 ± 2.7% compared to controls (24.6 ± 4.8%, p < 0.001). The administration of both atorvastatin and bosentan resulted in significantly higher collagen content and thicker fibrous cap versus COG (p < 0.01). All intervention groups showed lower relative intra-plaque concentrations of MCP-1, MMP-3, and MMP-9 and a higher TIMP-1concentration compared to COG (p < 0.001). Importantly, latter parameters presented lower levels when bosentan was combined with atorvastatin compared to COG (p < 0.05). Bosentan treatment in diabetic, atherosclerotic ApoE-/- mice delayed the atherosclerosis progression and enhanced plaques' stability, showing modest but additive effects with atorvastatin, which are promising in atherosclerotic cardiovascular diseases.

Aprocitentan (Tryvio) for hypertension.

The FDA has approved the dual endothelin receptor antagonist aprocitentan (Tryvio – Idorsia) for use in combination with other antihypertensive drugs to treat hypertension in adults whose blood pressure is not adequately controlled on other drugs. Three other dual endothelin receptor antagonists, ambrisentan (Volibris, and generics), bosentan (Tracleer, and generics), and macitentan (Opsumit), are available in the US for treatment of pulmonary arterial hypertension.

Targeting the endothelium by combining endothelin-1 antagonism and SGLT-2 inhibition: better together?

Endothelin A and B receptors, together with sodium-glucose cotransporter-2 (SGLT-2) channels are important targets in improving endothelial function and intervention with inhibitors has been the subject of multiple mechanistic and clinical outcome trials over recent years. Notable successes include the treatment of pulmonary hypertension with endothelin receptor antagonists, and the treatment of heart failure and chronic kidney disease with SGLT-2 inhibitors. With distinct and complementary mechanisms, in this review, we explore the logic of combination therapy for a number of diseases which have endothelial dysfunction at their heart.

Exploring Novel Therapeutic Approaches for Chronic Kidney Disease

Chronic kidney disease (CKD) is a significant global health burden, affecting millions of individuals worldwide. Despite current treatment strategies focusing on glycemic control and renin-angiotensin system blockade, these approaches merely delay the progression to end-stage renal disease (ESRD) and are associated with potential adverse effects. Recent advancements in our understanding of the complex pathophysiology of CKD have unveiled various unique processes contributing to its development, including vascular alterations, podocyte and renal epithelial cell loss, matrix deposition, inflammation, and metabolic dysregulation. This comprehensive review critically evaluates novel therapeutic approaches targeting these distinct pathways implicated in CKD pathogenesis. Strategies discussed include endothelial glycocalyx restoration, endothelin receptor antagonists, anti-apoptotic and podocyte regeneration therapies, anti-inflammatory and antioxidant agents, sodium-glucose co-transporter 2 (SGLT2) inhibitors, mitochondria-targeted therapies, anti-fibrotic agents, and interventions targeting epithelial-to-mesenchymal transition (EMT). While preclinical studies have demonstrated promising results for many of these approaches, their translation to clinical settings has been challenging due to safety concerns, lack of efficacy in trials, and the heterogeneity of CKD pathogenesis. The review highlights the importance of identifying appropriate patient populations, developing precision medicine strategies, exploring combination therapies, and leveraging novel drug delivery systems and regenerative medicine approaches to overcome current obstacles and improve therapeutic outcomes for CKD patients

US commercial health plan coverage dynamics in pulmonary arterial hypertension therapies.

Health plan coverage is central to patient access to care, especially for rare, chronic diseases. For specialty drugs, coverage varies, resulting in barriers to access. Pulmonary arterial hypertension (PAH) is a rare, progressive, and fatal disease. Guidelines suggest starting or rapidly escalating to combination therapy with drugs of differing classes (phosphodiesterase 5 inhibitors [PDE5is], soluble guanylate cyclase stimulators [sGC stimulators], endothelin receptor antagonists [ERAs], and prostacyclin pathway agents [PPAs]). To assess the variation in commercial health plan coverage for PAH treatments and how coverage has evolved. To examine the frequency of coverage updates and evidence cited in plan policies. We used the Tufts Medical Center Specialty Drug Evidence and Coverage database, which includes publicly available specialty drug coverage policies. Overall, and at the drug and treatment class level, we identified plan-imposed coverage restrictions beyond the drug's US Food and Drug Administration label, including step therapy protocols, clinical restrictions (eg, disease severity), and prescriber specialty requirements. We analyzed variation in coverage restrictiveness and how coverage has changed over time. We determined how often plans update their policies. Finally, we categorized the cited evidence into 6 different types. Results reflected plan coverage policies for 13 PAH drugs active between August 2017 and August 2022 and issued by 17 large US commercial health plans, representing 70% of covered lives. Coverage restrictions varied mainly by step therapy protocols and prescriber restrictions. Seven plans had step therapy protocols for most drugs, 9 for at least one drug, and 1 had none. Ten plans required specialist (cardiologist or pulmonologist) prescribing for at least one drug, and 7 did not. Coverage restrictions increased over time: the proportion of policies with at least 1 restriction increased from 38% to 73%, and the proportion with step therapy protocols increased from 29% to 46%, with generics as the most common step. The proportion of policies with step therapy protocols increased for every therapy class with generic availability: 18% to 59% for ERAs, 33% to 77% for PDE5is, and 33% to 43% for PPAs. The proportion of policies with prescriber requirements increased from 24% to 48%. Plans updated their policies 58% of the time annually and most often cited the 2019 CHEST clinical guidelines, followed by randomized controlled trials. Plan use of coverage restrictions for PAH therapies increased over time and varied across both drugs and plans. Inconsistency among health plans may complicate patient access and reduce the proportion who can persist on PAH treatments.

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.

#362 Dosing low, winning high: unlocking the promise of endothelin antagonism for the treatment of CKD in the zibotentan/dapagliflozin ZENITH trials

Abstract Background and Aims The Phase 2b ZENITH-CKD trial demonstrated that combined treatment with the endothelin A receptor (ETAR) antagonist zibotentan and the sodium-glucose co-transporter-2 inhibitor (SGLT2i) dapagliflozin yields a robust and significant reduction in albuminuria in individuals with chronic kidney disease (CKD), compared to dapagliflozin treatment alone [1]. This is hypothesized to translate into a significant reduction of kidney function decline and may further confer cardiometabolic benefits including reducing blood pressure, LDL cholesterol and (in type 2 diabetes) HbA1c in the ongoing Phase 3 ZENITH High Proteinuria trial. The usage of ETAR antagonists has until now been limited by the class effect of fluid retention, which is associated with an increased risk of heart failure in the at-risk CKD population. Zibotentan has previously been investigated at 10 mg per day in Phase 3 for the treatment of prostate cancer. Method Model-Informed Drug Development (MIDD) was integrated with clinical pharmacology data to develop the dose strategy for both ZENITH trials. A low-dose strategy was selected considering the increased plasma exposure of zibotentan in kidney impairment. The Phase 2b dose steps were selected based on an exposure response model for the efficacy marker urinary albumin to creatinine ratio (uACR) and were supported using clinical trial simulations. The dose strategy for Phase 3 was defined based on a combined analysis of ZENITH-CKD results for both efficacy and tolerability: efficacy (uACR reduction on top of dapagliflozin) was analysed with a Dose-Response Mixed Model for Repeated Measures, and tolerability (fluid retention events, defined as a combination of specified body weight and BNP increase) was evaluated with Kaplan Meier analyses. Results Zibotentan doses of 0.25 mg and 1.5 mg (in a first, discontinued study part also 5 mg), in combination with dapagliflozin 10 mg, were selected for ZENITH-CKD. Clinical trial simulations indicated that inclusion of the low dose of 0.25 mg was crucial to characterise the dose-response relationship. Dose-uACR response modelling of ZENITH-CKD data predicted a zibotentan dose of 0.75 mg to result in a mean uACR reduction of around 25% in addition to the reduction with dapagliflozin. A post-hoc regression analysis of uACR mean changes from baseline, stratified by dose, showed a trend towards lower uACR reduction with higher eGFR levels. Kaplan-Meier analyses of the fluid retention risk in different eGFR subgroups indicated that the fluid retention risk increased with increasing zibotentan dose for eGFR levels &amp;lt;45 mL/min/1.73 m2, while for higher eGFR levels, no differences were observed between treatments with dapagliflozin alone and added zibotentan 0.25 mg or 1.5 mg. Therefore, a kidney-function based zibotentan dose strategy was selected for the ZENITH High Proteinuria trial: Combined zibotentan/dapagliflozin is being compared against dapagliflozin alone; within the combination treatment arm, 0.25 mg zibotentan is selected for participants with baseline eGFR levels &amp;lt;45 mL/min/1.73 m2, and 0.75 mg is selected for higher eGFR level, with a tolerance eGFR window for participants whose eGFR declines below this cut-off, and with the possibility to reduce the dose to 0.25 mg in case of tolerability findings. Conclusion The favourable benefit/risk profile that was demonstrated for combined zibotentan/dapagliflozin in ZENITH-CKD was enabled by the zibotentan low-dose strategy. The wide dose ranging and MIDD further enabled selection of a kidney-function based zibotentan dosing strategy for ZENITH High Proteinuria which is designed to further balance benefit/risk. The low-dose zibotentan strategy and the combination with dapagliflozin opened for the first time a therapeutic window for ETAR antagonists, with the potential to redefine their value for the treatment of CKD. This work was sponsored by AstraZeneca.

#2661 High albuminuria in CKD: prevalence and characteristics in a real-world clinical setting

Abstract Background and Aims Chronic kidney disease (CKD) is estimated to affect 1 in 10 adults globally. CKD is associated with increased morbidity, mortality and decreased quality of life, and places a financial burden on the healthcare system. Furthermore, persistently high albuminuria is associated with an especially high risk of renal and cardiovascular complications in patients with CKD. With recent advances in therapeutic approaches for CKD management, both with sodium–glucose co-transporter-2 inhibitors (SGLT2i) and endothelin receptor antagonists as add-on to renin–angiotensin system blockade, it is important to highlight patients with persistent urine albumin-creatinine ratio (UACR; ≥700 mg/g). In patients with UACR &amp;gt;700 mg/g, a novel and highly selective endothelin receptor A antagonist (zibotentan) plus the SGLT2i dapagliflozin significantly reduced albuminuria versus dapagliflozin plus placebo (ZENITH-CKD trial). Hence, it is important to understand the prevalence and characteristics of patients with CKD and high albuminuria in a real-world clinical setting. Methods We used a large USA claims database (Optum's de-identified Clinformatics® Data Mart Database [CDM]) to identify patients aged ≥18 years with a CKD diagnosis and a UACR measurement ≥200 mg/g. Patients were indexed on 1st January 2022 and grouped into two UACR groups: ≥700UACR group (≥700 mg/g) and &amp;lt;700UACR group (200–699 mg/g). Continuous variables were calculated as medians with interquartile range (IQR). Baseline characteristics and comorbidities included age, sex, median UACR, median estimated glomerular filtration rate (eGFR) and a history of heart failure. Results Of 53,306 patients with CKD and UACR ≥200 mg/g, 22,504 (42%) were in the ≥700UACR group and 30,802 (58%) in the &amp;lt;700UACR group (Fig. 1). Patients were more frequently men in both groups (57%). Median UACR was 1459 mg/g (IQR 977–2473) in the ≥700UACR group and 341 mg/g (IQR 256–474) in the &amp;lt;700UACR group. Patients in the ≥700UACR group were slightly younger (72 vs 74 years), had a higher frequency of heart failure (42% vs 34%) and lower eGFR (37 mL/min/1.73 m2 [IQR 21–55] vs 49 mL/min/1.73 m2 [IQR 34–67]) compared to the &amp;lt;700UACR group. Conclusions In this contemporary study of patients with albuminuric CKD, more than 4 out of 10 had UACR levels ≥700 mg/g. These patients were slightly younger, had more severe CKD, and greater prevalence of cardiorenal disease compared to those with UACR 200–699 mg/g. Patients with UACR levels ≥700 mg/g have an urgent need for improved risk management.