Hemodynamics and pharmacokinetics of tezosentan, a dual endothelin receptor antagonist, in patients with cirrhosis

Microarray analysis demonstrates up-regulation of the endothelin-1 gene with compensatory down-regulation of the ETA receptor gene in human portal vein

High blood pressure in the portal vein, portal hypertension (PH), is the final common pathway in liver cirrhosis regardless of aetiology. Complications from PH are the major cause of morbidity and mortality in these patients. Current drug therapy to reduce portal pressure is mainly limited to β-adrenergic receptor blockade but approximately 40% of patients do not respond. Our aim was to use microarray to measure the expression of ∼20,800 genes in portal vein from patients with PH undergoing transplantation for liver cirrhosis (PH, n=12) versus healthy vessels (control, n=9) to identify potential drug targets to improve therapy. Expression of 9,964 genes above background was detected in portal vein samples. Comparing PH veins versus control (adjusted P-value < 0.05, fold change > 1.5) identified 548 up-regulated genes and 1,996 down-regulated genes. The 2,544 differentially expressed genes were subjected to pathway analysis. We identified 49 significantly enriched pathways. The endothelin pathway was ranked the tenth most significant, the only vasoconstrictive pathway to be identified. ET-1 gene (EDN1) was significantly up-regulated, consistent with elevated levels of ET-1 peptide previously measured in PH and cirrhosis. ETA receptor gene (EDNRA) was significantly down-regulated, consistent with an adaptive response to increased peptide levels in the portal vein but there was no change in the ETB gene (EDNRB). The results provide further support for evaluating the efficacy of ETA receptor antagonists as a potential therapy in addition to β-blockers in patients with PH and cirrhosis.

Repurposing of the Drug Tezosentan for Cancer Therapy

Tezosentan is a vasodilator drug that was originally developed to treat pulmonary arterial hypertension. It acts by inhibiting endothelin (ET) receptors, which are overexpressed in many types of cancer cells. Endothelin-1 (ET1) is a substance produced by the body that causes blood vessels to narrow. Tezosentan has affinity for both ET_A and ET_B receptors. By blocking the effects of ET1, tezosentan can help to dilate blood vessels, improve the blood flow, and reduce the workload on the heart. Tezosentan has been found to have anticancer properties due to its ability to target the ET receptors, which are involved in promoting cellular processes such as proliferation, survival, neovascularization, immune cell response, and drug resistance. This review intends to demonstrate the potential of this drug in the field of oncology. Drug repurposing can be an excellent way to improve the known profiles of first-line drugs and to solve several resistance problems of these same antineoplastic drugs.

Emerging Therapeutic Targets for Portal Hypertension

Purpose of Review

Portal hypertension is responsible of the main complications of cirrhosis, which carries a high mortality. Recent treatments have improved prognosis, but this is still far from ideal. This paper reviews new potential therapeutic targets unveiled by advances of key pathophysiologic processes.

Recent Findings

Recent research highlighted the importance of suppressing etiologic factors and a safe lifestyle and outlined new mechanisms modulating portal pressure. These include intrahepatic abnormalities linked to inflammation, fibrogenesis, vascular occlusion, parenchymal extinction, and angiogenesis; impaired regeneration; increased hepatic vascular tone due to sinusoidal endothelial dysfunction with insufficient NO availability; and paracrine liver cell crosstalk. Moreover, pathways such as the gut-liver axis modulate splanchnic vasodilatation and systemic inflammation, exacerbate liver fibrosis, and are being targeted by therapy. We have summarized studies of new agents addressing these targets.

Summary

New agents, alone or in combination, allow acting in complementary mechanisms offering a more profound effect on portal hypertension while simultaneously limiting disease progression and favoring regression of fibrosis and of cirrhosis. Major changes in treatment paradigms are anticipated.

Investigational drugs in early clinical development for portal hypertension

INTRODUCTION

Advanced chronic liver disease is considered a reversible condition after removal of the primary aetiological factor. This has led to a paradigm shift in which portal hypertension (PH) is a reversible complication of cirrhosis. The pharmacologic management of PH is centered on finding targets to modify the natural history of cirrhosis and PH.

AREAS COVERED

This paper offers an overview of the use of pharmacological strategies in early clinical development that modify PH. Papers included were selected from searching clinical trials sites and PubMed from the last 10 years.

EXPERT OPINION

A paradigm shift has generated a new concept of PH in cirrhosis as a reversible complication of a potentially curable disease. Decreasing portal pressure to prevent decompensation and further complications of cirrhosis that may lead liver transplantation or death is a goal. Therapeutic strategies also aspire achieve total or partial regression of fibrosis thus eliminating the need for treatment or screening of PH.

Test-Retest Reliability and Consistency of HVPG and Impact on Trial Design: A Study in 289 Patients from 20 Randomized Controlled Trials

BACKGROUND AND AIMS

Portal hypertension (PH) is a major driver for cirrhosis complications. Portal pressure is estimated in practice by the HVPG. The assessment of HVPG changes has been used for drug development in PH. This study aimed at quantifying the test-retest reliability and consistency of HVPG in the specific context of randomized controlled trials (RCTs) for the treatment of PH in cirrhosis and its impact on power calculations for trial design.

APPROACH AND RESULTS

We conducted a search of published RCTs in patients with cirrhosis reporting individual patient-level data of HVPG at baseline and after an intervention, which included a placebo or an untreated control arm. Baseline and follow-up HVPGs in the control groups were extracted after digitizing the plots. We assessed reliability and consistency and the potential impact of study characteristics. We retrieved a total of 289 before and after HVPG measurements in the placebo/untreated groups from 20 RCTs. The time span between the two HVPG measurements ranged between 20 minutes and 730 days. Pre-/post-HVPG variability was lower in studies including only compensated patients; therefore, modeled sample size calculations for trials in compensated cirrhosis were lower than for decompensated cirrhosis. A higher proportion of alcohol-associated cirrhosis and unicentric trials was associated with lower differences between baseline and follow-up measurements. The smallest detectable difference in an individual was 26% and 30% in compensated and decompensated patients, respectively.

CONCLUSIONS

The test-retest reliability of HVPG is overall excellent. Within-individual variance was higher in studies including higher proportions of decompensated patients. These findings should be taken into account when performing power analysis for trials based on the effects on HVPG or when considering HVPG as a tool to guide therapy of PH.

The Role of Hepatic Venous Pressure Gradient in the Management of Cirrhosis

Quantifying the degree of portal hypertension provides useful information to estimate prognosis and to evaluate new therapies for portal hypertension. This quantification is done in clinical practice with the measurement of the hepatic venous pressure gradient. This article addresses the applications of measuring portal pressure in cirrhosis, including the differential diagnosis of portal hypertension; estimation of prognosis in cirrhosis, including preoperative evaluation before hepatic and extrahepatic surgery; assessment of the response to drug therapy (mainly in the context of drug development); and assessing the regression of portal hypertension syndrome.

Effect of ET-A blockade on portal pressure and hepatic arterial perfusion in patients with cirrhosis: A proof of concept study

BACKGROUND/AIM

Endothelin causes vasoconstriction via the endothelin-A receptor (ET-A) in the intrahepatic circulation in cirrhosis and its increase leads to portal hypertension. The aim of the study was to investigate the acute effect of a selective ET-A antagonist in patients with portal hypertension and cirrhosis.

METHODS

Proof-of-concept study with two different substudies: (a) local intrahepatic administration of the ET-A antagonist BQ 123 and (b) systemic oral administration of the ET-A antagonist Ambrisentan. Portal pressure was determined by hepatic venous pressure gradient (HVPG, both substudies) and hepatic arterial blood flow (HABF) by intra-arterial Doppler measurements (substudy 1) before and under the ET-A antagonist. Systemic haemodynamic parameters were measured in substudy 2.

RESULTS

Twelve patients (Child-Pugh [CP] B/C n = 7/5) were included in substudy 1 and 14 patients (CP A/B/C n = 4/6/4) in substudy 2. The relative decrease in HVPG was -12.5% (IQR: -40% to 0%; P = .05) in substudy 1 and -5.0% (IQR: -11.5% to 0%; P = .01) in substudy 2. Substudy 1 revealed higher decrease in HVPG in CP B patients. HABF increased significantly and patients without portal pressure decrease showed a higher increase of HABF. Substudy 2 showed a slight decrease in the mean arterial pressure without changes of other systemic haemodynamic parameters.

CONCLUSION

Administration of a selective ET-A antagonist decreases the portal pressure in cirrhotic patients. This decrease was higher in CP B patients and the non-responders showed a higher increase in hepatic arterial flow. Selective ET-A antagonists might be a future treatment option in patients with portal hypertension.

Regression of portal hypertension: underlying mechanisms and therapeutic strategies

Portal hypertension is the main non-neoplastic complication of chronic liver disease, being the cause of important life-threatening events including the development of ascites or variceal bleeding. The primary factor in the development of portal hypertension is a pathological increase in the intrahepatic vascular resistance, due to liver microcirculatory dysfunction, which is subsequently aggravated by extra-hepatic vascular disturbances including elevation of portal blood inflow. Evidence from pre-clinical models of cirrhosis has demonstrated that portal hypertension and chronic liver disease can be reversible if the injurious etiological agent is removed and can be further promoted using pharmacological therapy. These important observations have been partially demonstrated in clinical studies. This paper aims at providing an updated review of the currently available data regarding spontaneous and drug-promoted regression of portal hypertension, paying special attention to the clinical evidence. It also considers pathophysiological caveats that highlight the need for caution in establishing a new dogma that human chronic liver disease and portal hypertension is reversible.

Pharmacologic Management of Portal Hypertension

Terlipressin, somatostatin, or octreotide are recommended as pharmacologic treatment of acute variceal hemorrhage. Nonselective β-blockers decrease the risk of variceal hemorrhage and hepatic decompensation, particularly in those 30% to 40% of patients with good hemodynamic response. Carvedilol, statins, and anticoagulants are promising agents in the management of portal hypertension. Recent advances in the pharmacologic treatment of portal hypertension have mainly focused on modifying an increased intrahepatic resistance through nitric oxide and/or modulation of vasoactive substances. Several novel pharmacologic agents for portal hypertension are being evaluated in humans.

Advances in therapeutic options for portal hypertension

Portal hypertension represents one of the major clinical consequences of chronic liver disease, having a deep impact on patients' prognosis and survival. Its pathophysiology defines a pathological increase in the intrahepatic vascular resistance as the primary factor in its development, being subsequently aggravated by a paradoxical increase in portal blood inflow. Although extensive preclinical and clinical research in the field has been developed in recent decades, no effective treatment targeting its primary mechanism has been defined. The present review critically summarizes the current knowledge in portal hypertension therapeutics, focusing on those strategies driven by the disease pathophysiology and underlying cellular mechanisms.

Novel treatment options for portal hypertension

Portal hypertension is most frequently associated with cirrhosis and is a major driver for associated complications, such as variceal bleeding, ascites or hepatic encephalopathy. As such, clinically significant portal hypertension forms the prelude to decompensation and impacts significantly on the prognosis of patients with liver cirrhosis. At present, non-selective β-blockers, vasopressin analogues and somatostatin analogues are the mainstay of treatment but these strategies are far from satisfactory and only target splanchnic hyperemia. In contrast, safe and reliable strategies to reduce the increased intrahepatic resistance in cirrhotic patients still represent a pending issue. In recent years, several preclinical and clinical trials have focused on this latter component and other therapeutic avenues. In this review, we highlight novel data in this context and address potentially interesting therapeutic options for the future.

Emerging therapies for portal hypertension in cirrhosis

INTRODUCTION

Counteracting splanchnic vasodilatation and increased portal-collateral blood flow has been the mainstay for the treatment of portal hypertension (PH) over the past three decades. However, there is still large room for improvement in the treatment of PH.

AREAS COVERED

The basic mechanism leading to portal hypertension is the increased hepatic vascular resistance to portal blood flow caused by liver structural abnormalities inherent to cirrhosis and increased hepatic vascular tone. Molecules modulating microvascular dysfunction which have undergone preclinical and clinical trials are summarized, potential drug development issues are addressed, and situations relevant to design of clinical trials are considered.

EXPERT OPINION

Experimental and clinical evidence indicates that molecules modulating liver microvascular dysfunction may allow for 30-40% reduction in portal pressure. Several agents could be utilized in the earlier stages of cirrhosis (antifibrotics, antiangiogenics, etiological therapies) may allow reduction of fibrosis and halt progression of PH. This 'nip at the bud' policy, by combining therapies with existing agents used in advanced phase of cirrhosis and novel agents which could be used in early phase of cirrhotic spectrum, which are likely to hit the market soon would be the future strategy for PH therapy.

[Aspects of pathogenetc pharmacotherapy for portal hypertension in liver cirrhosis]

The review of literature considers the principles of medical treatment for portal hypertension in liver cirrhosis, which are based on the current views of its development mechanisms. It describes both current pharmacotherapy methods for portal hypertension and drugs, the efficacy of which is being investigated.

Contemporary concepts of the medical therapy of portal hypertension under liver cirrhosis

Severe complications of liver cirrhosis are mostly related to portal hypertension. At the base of the pathogenesis of portal hypertension is the increase in hepatic vascular resistance to portal blood flow with subsequent development of hyperdynamic circulation, which, despite of the formation of collateral circulation, promotes progression of portal hypertension. An important role in its pathogenesis is played by the rearrangement of vascular bed and angiogenesis. As a result, strategic directions of the therapy of portal hypertension under liver cirrhosis include selectively decreasing hepatic vascular resistance with preserving or increasing portal blood flow, and correcting hyperdynamic circulation and pathological angiogenesis, while striving to reduce the hepatic venous pressure gradient to less than 12 mmHg or 20% of the baseline. Over the last years, substantial progress in understanding the pathophysiological mechanisms of hemodynamic disorders under liver cirrhosis has resulted in the development of new drugs for their correction. Although the majority of them have so far been investigated only in animal experiments, as well as at the molecular and cellular level, it might be expected that the introduction of the new methods in clinical practice will increase the efficacy of the conservative approach to the prophylaxis and treatment of portal hypertension complications. The purpose of the review is to describe the known methods of portal hypertension pharmacotherapy and discuss the drugs that may affect the basic pathogenetic mechanisms of its development.

Effect of reducing portal pressure on intestinal barrier function in patients with decompensated cirrhosis

AIM: To explore the effect of reducing portal pressure on intestinal barrier function in patients with decompensated cirrhosis.

METHODS: Eighty-six patients with decompensated viral liver cirrhosis or alcoholic cirrhosis were randomly divided into either an experiment group or a control group. The control group received conventional symptomatic and supportive treatment, and the experiment group was additionally given propranolol hydrochloride tablets. The width of the portal vein, alanine aminotransferase (ALT), aspartic transaminase (AST), total bilirubin (TBIL), serum albumin (ALB), plasma endotoxin level, D-lactic acid content and plasma diamine oxidase (DAO) were compared between the two groups.

RESULTS: The width of the portal vein in the experiment group posttreatment was significantly lower than that before treatment (1.37 cm ± 0.09 cm vs 1.41 cm ± 0.11 cm, P < 0.05) and that in the control group (1.37 cm ± 0.09 cm vs 1.39 cm ± 0.10 cm, P < 0.05). The levels of ALT, AST and TBIL in both groups posttreatment were significantly lower and the levels of ALB were significantly higher than those before treatment (35.15 U/L ± 11.92 U/L vs 42.76 U/L ± 18.06 U/L, 29.03 U/L ± 13.88 U/L vs 35.04 U/L ± 19.84 U/L, 19.57 μmol/L ± 10.59 μmol/L vs 25.65 μmol/L ± 15.09 μmol/L, 32.69 g/L ± 3.96 g/L vs 30.16 g/L ± 5.63 g/L, 34.03 U/L ± 11.46 U/L vs 42.91 U/L ± 17.67 U/L, 28.36 U/L ± 14.37 U/L vs 36.62 U/L ± 20.54 U/L, 18.94 μmol/L ± 9.56 μmol/L vs 24.92 μmol/L ± 16.60 μmol/L, 32.28 g/L ± 6.13 g/L vs 29.94 g/L ± 5.06 g/L, P < 0.05), although there were no significant differences in the levels of ALT, AST, TBIL and ALB between the two groups posttreatment (35.15 U/L ± 11.92 U/L vs 34.03 U/L ± 11.46 U/L, 29.03 U/L ± 13.88 U/L vs 28.36 ± 14.37 U/L, 19.57 μmol/L ± 10.59 μmol/L vs 18.94 μmol/L ± 9.56 μmol/L, 32.69 g/L ± 3.96 g/L vs 32.28 g/L ± 6.13 g/L, P > 0.05). Plasma endotoxin level, D-lactic acid content and DAO in the two groups posttreatment were significantly lower than those before treatment (0.53 EU/mL ± 0.12 EU/mL vs 0.72 EU/mL ± 0.11 EU/mL, 2.71 Ku/L ± 0.84 Ku/L vs 5.19 Ku/L ± 2.12 Ku/L, 7.85 mg/L ± 0.62 mg/L vs 12.95 mg/L ± 4.27 mg/L, 0.62 EU/mL ± 0.11 EU/mL vs 0.75 EU/mL ± 0.14 EU/mL, 3.83 Ku/L ± 1.70 Ku/L vs 5.34 Ku/L ± 2.08 Ku/L, 9.90 mg/L ± 6.70 mg/L vs 13.24 mg/L ± 4.42 mg/L, P < 0.05). Plasma endotoxin level, D-lactic acid content and DAO in the experiment group were significantly lower than those in the control group (0.53 EU/mL ± 0.12 EU/mL vs 0.62 EU/mL ± 0.11 EU/mL, 2.71 Ku/L ± 0.84 Ku/L vs 3.83 Ku/L ± 1.70 Ku/L, 7.85 mg/L ± 0.62 mg/L vs 9.90 mg/L ± 6.70 mg/L, P < 0.05).

CONCLUSION: Propranolol can not only improve liver function, reduce the width of the portal vein, decrease the levels of plasma endotoxin, D-lactic acid content and DAO, reduce portal hypertension, but also improve intestinal mucosal repair, reduce intestinal permeability, and improve intestinal barrier function.

Increased endothelin receptor B and G protein coupled kinase-2 in the mesentery of portal hypertensive rats

AIM: To elucidate the mechanisms of mesenteric vasodilation in portal hypertension (PHT), with a focus on endothelin signaling.

METHODS: PHT was induced in rats by common bile duct ligation (CBDL). Portal pressure (PP) was measured directly via catheters placed in the portal vein tract. The level of endothelin-1 (ET-1) in the mesenteric circulation was determined by radioimmunoassay, and the expression of the endothelin A receptor (ETAR) and endothelin B receptor (ETBR) was assessed by immunofluorescence and Western blot. Additionally, expression of G protein coupled kinase-2 (GRK2) and β-arrestin 2, which influence endothelin receptor sensitivity, were also studied by Western blot.

RESULTS: PP of CBDL rats increased significantly (11.89 ± 1.38 mmHg vs 16.34 ± 1.63 mmHg). ET-1 expression decreased in the mesenteric circulation 2 and 4 wk after CBDL. ET-1 levels in the systemic circulation of CBDL rats were increased at 2 wk and decreased at 4 wk. There was no change in ETAR expression in response to CBDL; however, increased expression of ETBR in the endothelial cells of mesenteric arterioles and capillaries was observed. In sham-operated rats, ETBR was mainly expressed in the CD31⁺ endothelial cells of the arterioles. With development of PHT, in addition to the endothelial cells, ETBR expression was noticeably detectable in the SMA⁺ smooth muscle cells of arterioles and in the CD31⁺ capillaries. Following CBDL, increased expression of GRK2 was also found in mesenteric tissue, though there was no change in the level of β-arrestin 2.

CONCLUSION: Decreased levels of ET-1 and increased ETBR expression in the mesenteric circulation following CBDL in rats may underlie mesenteric vasodilation in individuals with PHT. Mechanistically, increased GRK2 expression may lead to desensitization of ETAR, as well as other vasoconstrictors, promoting this vasodilatory effect.