Vasopressin receptor antagonists in the management of acute heart failure

Vasopressin is a potent vasoconstrictor and plays a significant role in the regulation of volume homeostasis. Several non-peptide vasopressin receptor antagonists (vaptans) have emerged as promising drugs in the management of acute heart failure. Results of early trials with tolvaptan (selective vasopressin subtype 2 receptor antagonist) and conivaptan (dual vasopressin subtypes 1a and 2 receptor antagonist) have demonstrated improvement in the fluid status, osmotic balance and haemodynamic profile in patients with heart failure presenting with signs and symptoms of decompensation. Nevertheless, their comparative long-term safety and efficacy remains to be determined in large-scale clinical trials.     

Lixivaptan: a novel vasopressin receptor antagonist

Arginine vasopressin, also known as antidiuretic hormone, is a neuropeptide that functions in the maintenance of body water homeostasis. Inappropriate secretion of vasopressin has been implicated in the pathophysiology of multiple diseases, including polycystic kidney disease, syndrome of inappropriate antidiuretic hormone (SIADH) secretion, and the hyponatremia commonly associated with cirrhosis and congestive heart failure. Vasopressin receptor antagonists are novel agents that block the physiologic actions of vasopressin. Lixivaptan is a vasopressin receptor antagonist with high V2 receptor affinity and is now undergoing Phase III clinical trials. Studies so far have demonstrated that lixivaptan is efficacious in the correction of hyponatremia in SIADH, heart failure and liver cirrhosis with ascites, and few adverse effects have been noted. Thus, lixivaptan remains a promising therapeutic modality for the treatment of multiple diseases and prevention of the associated morbidity and mortality associated with hyponatremia.     

Tolvaptan: a selective vasopressin type 2 receptor antagonist in congestive heart failure

The neurohormone arginine vasopressin plays a significant role in the regulation of volume homeostasis, which is mediated via vasopressin type 2 (V2) receptors in the collecting tubules of the kidney. Diseases that are accompanied by abnormal volume homeostasis, including congestive heart failure and cirrhosis, are a frequent cause of hospital admissions and increasing healthcare costs. Recently, several nonpeptide V2 receptor antagonists have emerged as promising agents in the management of these conditions with the advantage of having no electrolyte abnormalities, neurohormonal activation or worsening renal insufficiency. Tolvaptan, a highly selective nonpeptide V2 receptor antagonist, has demonstrated an improvement in the volume status, osmotic balance and haemodynamic profile in preclinical and Phase II trials in patients with congestive heart failure and is currently undergoing testing in Phase III trials. This review discusses the evidence for the potential uses of tolvaptan, and its pharmacology and pharmacokinetics, particularly in congestive heart failure.     

Lixivaptan, a non-peptide vasopressin V2 receptor antagonist for the potential oral treatment of hyponatremia

Lixivaptan (VPA-985), being developed by Biogen Idec and Cardiokine, under license from Wyeth (now part of Pfizer), is a non-peptide, selective vasopressin V2 receptor antagonist for the potential oral treatment of hyponatremia associated with heart failure. Arginine vasopressin, the native V2 receptor ligand, stimulates water reabsorption via activation of V2 receptors that are expressed in the collecting ducts of the kidney. In preclinical studies, lixivaptan displayed competitive antagonist activity at V2 receptors in vitro, and increased urine volume and decreased urine osmolality in rats and dogs. The therapeutic benefits of lixivaptan are being evaluated in patients with conditions that are associated with water excess and hyponatremia. Phase II clinical trials in patients with congestive heart failure, liver cirrhosis with ascites or syndrome of inappropriate antidiuretic hormone have demonstrated that, unlike traditional diuretics, lixivaptan increases water clearance without affecting renal sodium excretion or activating the neurohormonal system. Administration of lixivaptan in combination with the diuretic furosemide has been tested in rats as well as in trials in healthy volunteers, in which the two agents were well tolerated. Ongoing phase III trials will determine the role of lixivaptan in the management of hyponatremia, especially when associated with heart failure.     

Tolvaptan: a selective vasopressin type 2 receptor antagonist in congestive heart failure

The neurohormone arginine vasopressin plays a significant role in the regulation of volume homeostasis, which is mediated via vasopressin type 2 (V₂) receptors in the collecting tubules of the kidney. Diseases that are accompanied by abnormal volume homeostasis, including congestive heart failure and cirrhosis, are a frequent cause of hospital admissions and increasing healthcare costs. Recently, several nonpeptide V₂ receptor antagonists have emerged as promising agents in the management of these conditions with the advantage of having no electrolyte abnormalities, neurohormonal activation or worsening renal insufficiency. Tolvaptan, a highly selective nonpeptide V₂ receptor antagonist, has demonstrated an improvement in the volume status, osmotic balance and haemodynamic profile in preclinical and Phase II trials in patients with congestive heart failure and is currently undergoing testing in Phase III trials. This review discusses the evidence for the potential uses of tolvaptan, and its pharmacology and pharmacokinetics, particularly in congestive heart failure.     

The potential role for lixivaptan in heart failure and in hyponatremia

INTRODUCTION: Hypervolemia and hyponatremia are common features in heart failure and have been associated with increased morbidity and mortality. Stimulation of arginine vasopressin (AVP) plays an important role in the development of both hypervolemia and hyponatremia. Lixivaptan is a selective vasopressin type 2 (V(2)) receptor antagonist that has been demonstrated to have the ability to induce aquaresis, the electrolyte sparing excretion of water, resulting in fluid removal as well as correction of hyponatremia. AREAS COVERED: This article describes the prevalence, pathophysiology and current treatment limitations of hyponatremia, highlights the importance of arginine vasopressin and the potential role of arginine vasopressin antagonists and reviews all available literature on lixivaptan, a selective V(2) receptor antagonist. EXPERT OPINION: The available experience of lixivaptan in heart failure, although limited, is encouraging. Its aquaretic effect provides the basis for its use to correct hypervolemia and hyponatremia in patients with heart failure, and the absence of neurhormonal stimulation provides positive signal for the exploration of its potential in improving outcomes.     

Tolvaptan: a vasopressin antagonist for the management of euvolemic and hypervolemic hyponatremia

Tolvaptan is a new vasopressin antagonist developed for the treatment of hypervolemic or euvolemic hyponatremia. It has greater affinity for the V(2) receptor than native vasopressin or any other vasopressin antagonist. Blockade of the V(2) receptor induces solute-free water excretion without affecting normal electrolyte excretion. The pharmacokinetics and pharmacodynamics of tolvaptan are suitable for once-daily dosing. Throughout all phases of clinical studies, it was shown to be safe for short- and long-term use. Tolvaptan effectively increases serum sodium levels in patients with heart failure, cirrhosis and syndrome of inappropriate secretion of antidiuretic hormone. In patients hospitalized owing to heart failure, tolvaptan decreased bodyweight, increased urine output and improved dyspnea compared with placebo. However, tolvaptan has not proven to be beneficial for the long-term management of heart failure. Currently, tolvaptan is the only oral agent in its class available in the USA and Europe.     

伴有低钠血症的心力衰竭的治疗进展

心力衰竭时的低钠血症是一种高容量性稀释性低钠血症,其发生机制与心输出量减少,使血管升压素分泌增加,使肾小管对水的重吸收增加所致。常规治疗方法疗效不佳。血管升压素受体拮抗药是伴有低钠血症的心力衰竭治疗的最有效方法。     

Effect of the vasopressin receptor antagonist conivaptan in rats with heart failure following myocardial infarction

Myocardial infarction often induces congestive heart failure accompanied by a significant increase in plasma vasopressin concentration. To delineate the role of vasopressin in the pathogenesis of congestive heart failure, the acute hemodynamic and aquaretic effects of conivaptan (YM087, 4'-(2-methyl-1,4,5,6-tetrahydroimidazo[4,5-d][1]benzoazepine-6-carbonyl)-2-phenylbenzanilide monohydrochloride), a combined vasopressin V(1A) and V(2) receptor antagonist, were assessed in rats with heart failure induced by myocardial infarction. Left coronary artery ligation resulted in decreased left ventricular systolic pressure and first derivatives of left ventricular developed pressure, as well as increased left ventricular end-diastolic pressure, lung and right ventricular weight. Single oral administration of conivaptan (0.3 to 3.0 mg/kg) dose-dependently increased urine volume and decreased urine osmolality in heart failure rats. Furthermore, conivaptan (3.0 mg/kg) attenuated the changes in left ventricular end-diastolic pressure, lung and right ventricular weight induced by heart failure while reducing blood pressure. These results show that vasopressin plays a significant role in elevating vascular tone through vasopressin V(1A) receptors and plays a major role in retaining free water through vasopressin V(2) receptors in this model of congestive heart failure. Additionally, conivaptan, with its dual vasopressin V(1A) and V(2) receptor-inhibiting properties, could exert a beneficial effect on cardiac function in the congestive heart failure rat model.     

Therapeutic potential of vasopressin receptor antagonists

Arginine vasopressin (AVP) is a neuropeptide hormone that plays an important role in circulatory and sodium homeostasis, and regulating serum osmolality. Several clinical conditions have been associated with inappropriately elevated levels of AVP including heart failure, cirrhosis of the liver and the syndrome of inappropriate secretion of antidiuretic hormone. Three receptor subtypes that mediate the actions of AVP have been identified (V(1A), V(2) and V(1B)). Activation of V(1A) receptors located in vascular smooth muscle cells and the myocardium results in vasoconstriction and increased afterload and hypertrophy. The V(2) receptors located primarily in the collecting tubules mediate free water absorption. The V(1B) receptors are located in the anterior pituitary and mediate adrenocorticotropin hormone release. The cardiovascular and renal effects of AVP are mediated primarily by V(1A) and V(2) receptors. Antagonism of V(1A) receptors results in vasodilatation and antagonism of V(2) receptors resulting in aquaresis, an electrolyte-sparing water excretion. Several non-peptide AVP antagonists (vasopressin receptor antagonists [VRAs]) also termed 'vaptans' have been developed and are vigorously being studied primarily for treating conditions characterised by hyponatraemia and fluid overload. Conivaptan is a combined V(1A)/V(2)-receptor antagonist that induces diuresis as well as haemodynamic improvement. It has been shown in clinical trials to correct euvolaemic and hypervolaemic hyponatraemia, and has been approved by the US FDA for the treatment of euvolaemic hyponatraemia as an intravenous infusion. Tolvaptan, a selective V(2)-receptor antagonist, has undergone extensive clinical studies in the treatment of hyponatraemia and heart failure. It has been shown to effectively decrease fluid in volume overloaded patients with heart failure and to correct hyponatraemia. A large outcome study (n = 4133 patients) will define its role in the management of heart failure. Lixivaptan and satavaptan (SR-121463) are other selective V(2)-receptor antagonists being evaluated for the treatment of hyponatraemia. In addition, a potential role for the vaptans in attenuating polyuria in nephrogenic diabetes insipidus and cyst development in polycystic kidney disease is being explored. Ongoing clinical trials should further define the scope of the potential therapeutic role of VRAs.     

Hyponatremia: an update on current pharmacotherapy

Introduction: Hyponatremia is the most common electrolyte disorder in clinical practice, and it is associated with adverse outcomes. Severe hyponatremia can result in cerebral edema and hypoxia. Moreover, even mild hyponatremia can lead to gait instability and cognitive dysfunction, especially in the elderly. The main cause of hyponatremia is nonosmotic secretion of arginine vasopressin with resultant electrolyte-free water retention. Thus, the available management for chronic hyponatremia must increase solute-free water excretion, such as occurs with blocking vasopressin receptors with selective V2 antagonists.

Areas covered: Several recent trials have assessed the efficacy and safety of hyponatremia treatment using vasopressin receptor antagonists (vaptans). These trials documented the efficacy of vaptans to reverse hyponatremia. Moreover, treatment of hypervolemic hyponatremia, such as in heart failure or liver cirrhosis, with vasopressin receptor antagonist results in increased solute-free excretion without activation of the neurohumoral systems. The current review covers results on management of hyponatremia with different vasopressin receptor antagonists.

Expert opinion: Approaches, such as vasopressin receptor antagonists or urea, have been shown to reverse moderate hyponatremia. However, these agents have not been used to treat severe hyponatremia in clinical trials. Future studies in severe hyponatremic states are required to assess the impact of vaptans on clinically significant end points, such as morbidity and mortality.     

Angiotensin II receptor antagonists and heart failure: angiotensin-converting-enzyme inhibitors remain the first-line option

(1) Some angiotensin-converting-enzyme inhibitors (ACE inhibitors) reduce mortality in patients with heart failure (captopril, enalapril, ramipril and trandolapril), and in patients with recent myocardial infarction and heart failure or marked left ventricular dysfunction (captopril, ramipril and trandolapril). (2) Angiotensin II receptor antagonists, otherwise known as angiotensin receptor blockers, have haemodynamic effects similar to ACE inhibitors, but differ in their mechanism of action and certain adverse effects. (3) Five clinical trials have evaluated angiotensin II receptor antagonists (candesartan, losartan and valsartan) in terms of their effect on mortality and on the risk of clinical deterioration in patients with symptomatic heart failure, but without severe renal failure, hyperkalemia or hypotension. In these trials, candesartan and valsartan were used at much higher doses than those recommended for the treatment of arterial hypertension. (4) In patients with heart failure who were not taking an angiotensin II receptor antagonist or an ACE inhibitor at enrollment, no significant difference was found between losartan and captopril in terms of mortality or the risk of clinical deterioration. (5) In patients with heart failure who had stopped taking an ACE inhibitor because of adverse effects, candesartan had no effect on mortality as compared with placebo, but it did reduce the risk of clinical deterioration (3 fewer hospitalisations per year per 100 patients). However, candesartan was associated with adverse effects such as renal failure and hyperkalemia, especially in patients who had experienced these same adverse effects while taking an ACE inhibitor. (6) In patients with heart failure who were already taking an ACE inhibitor, adjunctive candesartan or valsartan treatment did not influence mortality in comparison to the addition of a placebo. Adding candesartan or valsartan reduced the risk of hospitalisation (between 1 and 3 fewer hospitalisations per year per 100 patients), but increased the risk of renal failure and hyperkalemia. (7) In patients with heart failure and incapacitating dyspnea despite ACE inhibitor + diuretic combination therapy, there are no trials comparing the addition of an angiotensin II receptor antagonist versus spironolactone. Adjunctive spironolactone therapy prevents 5 to 6 deaths per year per 100 patients in this setting. (8) In patients with heart failure who do not have markedly altered cardiac contractility, candesartan appears to have no clinical advantages over placebo. (9) In some of these trials, mortality was higher with angiotensin II receptor antagonist therapy than with placebo among patients who were already taking a betablocker. (10) Two trials have compared an angiotensin II receptor antagonist with an ACE inhibitor in patients with recent myocardial infarction who had heart failure or an altered left ventricular ejection fraction, but who did not have hypotension or severe renal failure. However, there are no placebo-controlled randomised trials assessing the effects of angiotensin II receptor antagonists on mortality. (11) In patients with recent myocardial infarction, these trials showed no difference in mortality between angiotensin II receptor antagonist treatment (losartan or valsartan) and captopril. They did not rule out the possibility that these angiotensin II receptor antagonists are moderately less effective than captopril. Adding valsartan to ongoing captopril therapy did not reduce mortality or morbidity as compared with placebo, but did increase the risk of adverse effects. (12) Overall, these trials confirm the advantage of angiotensin II receptor antagonists over ACE inhibitors with respect to some adverse effects (cough, skin rash, etc.). However, the two drug classes share certain serious adverse effects such as hyperkalemia, renal failure and hypotension. In one trial, angioedema was less frequent with angiotensin II receptor antagonist therapy (one less case per 500 patients).     

Tolvaptan: a vasopressin antagonist for the management of euvolemic and hypervolemic hyponatremia

Tolvaptan is a new vasopressin antagonist developed for the treatment of hypervolemic or euvolemic hyponatremia. It has greater affinity for the V₂ receptor than native vasopressin or any other vasopressin antagonist. Blockade of the V₂ receptor induces solute-free water excretion without affecting normal electrolyte excretion. The pharmacokinetics and pharmacodynamics of tolvaptan are suitable for once-daily dosing. Throughout all phases of clinical studies, it was shown to be safe for short- and long-term use. Tolvaptan effectively increases serum sodium levels in patients with heart failure, cirrhosis and syndrome of inappropriate secretion of antidiuretic hormone. In patients hospitalized owing to heart failure, tolvaptan decreased bodyweight, increased urine output and improved dyspnea compared with placebo. However, tolvaptan has not proven to be beneficial for the long-term management of heart failure. Currently, tolvaptan is the only oral agent in its class available in the USA and Europe.     

Conivaptan: a selective vasopressin antagonist

Complex neurohormonal interactions dictate the body's volume status in different disease states. Besides the known pathologic activation of the renin-angiotensin-aldosterone axis and the effect of the adrenergic system, arginine vasopressin (AVP) represents a key element that is responsible for volume homeostasis. Serum AVP levels have been shown to be chronically elevated in different pathologic conditions that exhibit an imbalance in volume status, particularly in congestive heart failure. Evidently, elevated levels of AVP play an important role in the pathogenesis and progression of these diseases. AVP has many other receptor-mediated deleterious effects on vascular smooth muscles and cardiomyocytes. These effects are an integral part of the neurohormonal milieu in patients with heart failure. This assumption has propelled agents that antagonize the effects of vasopressin receptors to the forefront of clinical research, especially in heart failure management. This paper reviews current knowledge on conivaptan, a novel dual V1a/V2 vasopressin receptor antagonist.     

V2 receptor antagonism with tolvaptan in heart failure

The prevalence and incidence of congestive heart failure continues to increase. The two hallmarks of this syndrome, sodium and water retention, are frequently a therapeutic challenge. Most conventional diuretics act primarily as saluretics by inhibiting renal tubular electrolyte reabsorption, which, due to osmotic pressure, promotes excretion of isotonic fluid. The peptide hormone arginine vasopressin vasoconstricts at the V(1A) receptor and promotes water reabsorption via the V(2) receptor in the renal collecting duct by inserting aquaporin-2 water channels into the luminal membrane. Tolvaptan, the first orally available non-peptide V(2) receptor antagonist, acts as a potent aquaretic. In this paper, the authors review the pharmacology of tolvaptan and discuss the results of the initial clinical trials with this potent new drug.     

Tolvaptan (Otsuka)

Otsuka is developing tolvaptan (OPC-41061), an orally active non-peptide vasopressin V2 antagonist, as a diuretic for the potential treatment of congestive heart failure. By November 2003, tolvaptan was undergoing phase III clinical trials.     

Tolvaptan: the evidence for its therapeutic value in acute heart failure syndrome

Introduction:

Acute heart failure syndrome (AHFS) is one of the leading causes of hospital admission in the US. Tolvaptan is a vasopressin V₂ receptor antagonist that blocks the effect of arginine vasopressin (AVP) in reabsorbing water from the collecting ducts of the nephrons in congestive heart failure.

Aims:

To review the evidence for utilizing tolvaptan in the treatment of AHFS.

Evidence review:

Several clinical trials have sought to assess the clinical effects of tolvaptan in heart failure. Compared with placebo, tolvaptan has been shown to reduce bodyweight and improve serum sodium in patients with AHFS without worsening renal function. Tolvaptan appeared to be well tolerated with a good safety profile. It caused a significant reduction in pulmonary capillary wedge pressure compared with placebo, but has yet to demonstrate reversal of cardiac remodeling. A large-scale mortality trial showed no differences in long-term mortality rates between tolvaptan and placebo, although early symptom relief was apparent with tolvaptan and lower diuretic use.

Place in therapy:

Tolvaptan has shown to be safe and effective in treating congestion in AHFS. Free water excretion in fluid-overloaded patients vulnerable to cardiorenal compromise with standard diuretic therapy makes V₂ vasopressin receptor blockade an attractive adjunct to standard medical therapy aimed at reducing congestion in AHFS.     

In vitro and in vivo pharmacological characterisation of the potent and selective vasopressin V(1A) receptor antagonist 4-[4-(4-Chloro-phenyl)-5-[1,2,3]triazol-2-ylmethyl-4H-[1,2,4]triazol-3-yl]-piperidin-1-yl-(3,5-difluoro-phenyl) methanone (PF-00738245)

The dysregulation of arginine vasopressin (AVP) release and activation of vasopressin receptors plays an important role in disease conditions including polycystic kidney disease, congestive heart failure and dysmenorrhoea. The development of potent and selective vasopressin receptor ligands is needed to help dissect the function of the specific subtypes in disease pathogenesis. Here we report the pharmacological characterisation of PF-00738245 in in vitro binding and functional assays using cells expressing vasopressin V(?A), V(?B) or V? receptors. PF-00738245 inhibited AVP binding to the recombinant human vasopressin V(?A) receptor (K(i)=2.85 nM) and blocked AVP-induced rat aortic ring and human myometrial contraction (pK(B)=7.35 and 8.62 respectively). PF-00738245 was selective for the vasopressin V(1A) receptor by demonstrating minimal binding to vasopressin V(?B) (3.6% inhibition at 10 μM) or functional activity at vasopressin V? receptors (8.1% agonist and -8.4% antagonist activity at 10 μM) as well as the oxytocin receptor (46.3% antagonist activity at 10 μM). The in vivo pharmacological properties were tested orally in the rat and PF-00738245 dose dependently blocked the effect of AVP on a capsaicin-induced cutaneous flare response. Taken together the data support the use of PF-00738245 as a potent and selective vasopressin V(?A) receptor antagonist which may have utility in the treatment of disease conditions which are propagated by elevation in vasopressin V(?A) receptor signalling.     

伴有低钠血症的心力衰竭治疗新药——托伐普坦

心力衰竭时常伴随低钠血症。心力衰竭的一般治疗方法对低钠血症疗效不佳。托伐普坦是精氨酸加压素V_2受体的拮抗药。托伐普坦通过抑制肾脏集合管水的重吸收,使肾脏对水的排泄增加,起到纠正低钠血症、增加尿量、改善心力衰竭症状等作用。临床研究表明托伐普坦在伴有低钠血症的心力衰竭治疗中发挥重要作用。     

Chronic vasopressin V(1A) but not V(2) receptor antagonism prevents heart failure in chronically infarcted rats

Evidence is increasing that therapeutic modulation of neurohormonal activation with vasopressin receptor antagonists via V(1A) and V(2) receptors may favourably affect prognosis of heart failure. This study was designed to compare in vivo hemodynamic effects of early treatment (1-21 days after infarction) with a V(1A) (SR-49059 or ((2S)1-[(2R3S)-5-chloro-3-(2-chlorophenyl)-1-(3,4-dimethoxybenzene-sulfonyl)-3-hydroxy-2,3-dihydro-1H-indole-2-carbonyl]-pyrrolidine-2-carboxamide); 0.3 mg/kg/day) and a V(2) (SR-121463B or (1-[4-(N-tert-Butylcarbamoyl)-2-methoxybenzene sulfonyl]-5-ethoxy-3-spiro-[4-(2-morpholinoethyoxy)-cyclo-hexane]indol-2one,furmate; 0.5 mg/kg/day) receptor antagonist in myocardial infarcted rats, chronically instrumented for hemodynamic measurements. Left ventricular dysfunction in conscious myocardial infarcted rats, which was evidenced by a significantly decreased cardiac output (myocardial infarction: 70+/-3 vs. sham: 81 +/- 3 ml/min) and stroke volume (myocardial infarction: 190 +/- 10 vs. sham: 221 +/- 7 microl), was restored by the vasopressin V(1A) (81+/-2 ml and 224 +/- 5 microl, respectively) but not V(2) receptor antagonist. Improved cardiac output with the vasopressin V(1A) receptor antagonist resulted from an increased stroke volume at a reduced myocardial infarction induced tachycardia. In addition to the hemodynamic measurements, left ventricular hypertrophy and capillary density were determined, histologically measured as the cross-sectional area of Gomori-stained myocytes and Lectin-stained capillaries per tissue area, respectively. The observed left ventricular concentric hypertrophy (myocardial infarction: 525 +/- 38 vs. sham: 347 +/- 28 microm(2); P < 0.05) and reduced capillary density (myocardial infarction: 2068 +/- 162 vs. sham: 2800 +/- 250 number/mm(2); P<0.05) in the spared myocardium of myocardial infarcted rats, remained unaffected by the vasopressin V(1A) or V(2) receptor antagonist. Thus, chronic vasopressin V(1A) but not V(2) receptor blockade prevents heart failure in 3-week-old infarcted rats. Moreover, the improved cardiac function could not attributed to changes in left ventricular hypertrophy and/or capillary density.