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.     

非肽类精氨酸加压素受体拮抗剂的研究进展

精氨酸加压素(AVP)可以通过与不同的AVP受体亚型结合产生抗利尿、收缩血管、加强记忆、参与体温和免疫调节、参与社会行为调节等不同的生理作用。AVP在体内参与雷诺氏综合征、痛经、焦虑症、抑郁症、慢性充血性心力衰竭、肝硬化、抗利尿激素分泌紊乱综合征等疾病的过程。新型高效的非肽类AVP受体拮抗剂一直是世界范围内的研究热点,本文从结构及构效关系等方面介绍了非肽类AVP受体拮抗剂的研究进展。     

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.     

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.     

托伐普坦片治疗低钠血症的效果及安全性观察

目的观察托伐普坦片对抗利尿激素分泌不高(SIADH)及其它原因引起的非低容量性、非急性低钠血症患者的疗效及安全性。方法 38例因充血性心力衰竭、肝功能衰竭伴腹水形成、慢性肾功能不全或抗利尿激素分泌不当等疾病引起体液潴留和低钠血症的患者,予口服托伐普坦片治疗。结果口服托伐普坦片者都有血钠浓度和血渗透压的显著升高。结论托伐普坦片能够显示良好的提高血清钠浓度作用,对低钠血症患者有明显疗效。没有严重并发症和不良反应,临床应用中简便且安全。     

Development and therapeutic indications of orally-active non-peptide vasopressin receptor antagonists

Vasopressin (AVP) is a cyclic nonapeptide hormone that exhibits many physiological effects including free water reabsorption, vasoconstriction, cellular proliferation and adrenocorticotrophic hormone (ACTH) secretion. In a healthy organism, AVP plays an important role in the homeostasis of fluid osmolality and volume status. However, in several diseases or conditions such as the syndrome of inappropriate secretion of AVP (SIADH), congestive heart failure, arterial hypertension, liver cirrhosis, nephrotic syndrome, dysmenorrhoea and ocular hypertension, AVP may play an important role in their pathophysiology. Recently, orally-active non-peptide AVP receptor antagonists were developed by random screening of chemical entities and optimisation of lead compounds. These include agents specific for the V₁-vascular and V₂-renal AVP receptor subtypes. Dual V₁/V₂ AVP receptor antagonists are also being studied. Some of these non-peptide receptor antagonists have been studied extensively, while others are currently under investigation. Potential therapeutic indications for AVP receptor antagonists comprise (1) The blockade of V1-vascular AVP receptors in arterial hypertension, congestive heart failure, Raynaud's syndrome, peripheral vascular disease and dysmenorrhoea. (2) The blockade of V2-renal AVP receptors in the syndrome of inappropriate secretion of vasopressin, congestive heart failure, liver cirrhosis, nephrotic syndrome and any state of excessive retention of free water and subsequent dilutional hyponatraemia. (3) The blockade of V3-pituitary AVP receptors in ACTH-secreting tumours. This review examines the pharmacology of orally-active non-peptide AVP receptor antagonists and their clinical applications.     

A novel vasopressin dual V1A/V2 receptor antagonist, conivaptan hydrochloride, improves hyponatremia in rats with syndrome of inappropriate secretion of antidiuretic hormone (SIADH)

We investigated the effects of intravenous administration of conivaptan hydrochloride, a dual vasopressin V1A and V2 receptor antagonist, on blood electrolytes and plasma osmolality in rats with an experimental syndrome of inappropriate secretion of antidiuretic hormone (SIADH). The experimental SIADH rat model was developed by means of continuous administration of arginine vasopressin (AVP) via a subcutaneously implanted osmotic mini pump, and hyponatremia was induced by additional water loading. This model possesses similar characteristics to those observed in patients with SIADH, specifically decreases in blood sodium concentration and plasma osmolality. In this experimental model, intravenous administration of conivaptan (0.1, 1 mg/kg) significantly increased blood sodium concentration and plasma osmolality. On the other hand, intravenous administration of furosemide (10 mg/kg) did not increase either blood sodium concentration or plasma osmolality in the SIADH rats. Moreover, furosemide significantly lowered blood potassium concentration. These results show that conivaptan improves hyponatremia in rats with SIADH, supporting the therapeutic potential of conivaptan in treatment of patients with hyponatremia associated with SIADH.     

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.     

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.     

Syndrome of inappropriate antidiuretic hormone-induced hyponatremia associated with amiodarone

The syndrome of inappropriate antidiuretic hormone (SIADH), the most common cause of euvolemic hyponatremia, is due to nonphysiologic release of arginine vasopressin from the posterior pituitary. Hyponatremia induced by SIADH can be caused by several conditions, such as central nervous system disorders, malignancies, various nonmalignant lung diseases, hypoadrenalism, and hypothyroidism. A 67-year-old man developed hyponatremia consistent with SIADH. Although common comorbid conditions associated with SIADH were excluded as possible causes, his medical history and drug regimen were extensive. However, he had been taking spironolactone, amiodarone, and simvastatin for less than 3 months. Amiodarone was discontinued based on a case report suggesting that this drug can cause SIADH-induced hyponatremia. The patient's serum sodium level began to rise within 3 days of discontinuation and returned to normal within 1 month. Although SIADH-induced hyponatremia occurs only rarely, it should be recognized as a possible adverse effect of amiodarone.     

颅脑损伤后抗利尿激素分泌异常综合征

目的:探讨颅脑损伤后抗利尿激素分泌异常综合征(SIADH)的诊断与治疗。方法:回顾性分析近7年收治的11例颅脑损伤并发SIADH的临床特点。首先按真性失盐常规补钠治疗,2～3d后血钠不回升或继续降低,补钠量与失钠量相当,考虑为SIADH,改为限水限钠治疗。结果:11例颅脑损伤合并SIADH均具有以下临床特点:低钠血症、低血浆渗透压、尿渗透压与血浆渗透压之比>1。治愈10例,死亡1例。结论:颅脑损伤并发SIADH的发病机制与治疗措施不同于低钠血症,早期诊治能降低颅脑损伤患者的病残率和病死率。     

Effects of demeclocycline on psychiatric polydipsia in schizophrenic patients]

Excess intake of water by schizophrenic patients is referred to as psychiatric polydipsia. This symptom causes incontinence, vomiting and hyponatremia, and may sometimes lead to death. We have no effective therapeutic methods other than administrating sodium chloride solution and diuretics, or restricting the intake itself. A case was reported stating that demeclocycline, used in case where there is the syndrome of inappropriate secretion of antidiuretic hormone (SIADH), was effective for the treatment of psychiatric polydipsia. We administered demeclocycline to 8 schizophrenic patients with psychiatric polydipsia, and noticed improvement in incontinence, vomiting and hyponatremia. There was also a decrease of polydipsic behavior. Demeclocycline inhibits the antidiuretic effect of vasopressin on the distal renal tubule. Considering the function of demeclocycline and the relevance of vasopressin to the central nervous system, it has been suggested that demeclocycline has effects on the central nerve through vasopressin or cyclic AMP.     

Conivaptan: a dual vasopressin receptor v1a/v2 antagonist [corrected

Several fluid retentive states such as heart failure, cirrhosis of the liver, and syndrome of inappropriate antidiuretic hormone secretion are associated with inappropriate elevation in plasma levels of arginine vasopressin (AVP), a neuropeptide that is secreted by the hypothalamus and plays a critical role in the regulation of serum osmolality and in circulatory homeostasis. The actions of AVP are mediated by three receptor subtypes V1a, V2, and V1b. The V1a receptor regulates vasodilation and cellular hypertrophy while the V2 receptor regulates free water excretion. The V1b receptor regulates adrenocorticotropin hormone release. Conivaptan is a nonpeptide dual V1a/V2 AVP receptor antagonist. It binds with high affinity, competitively, and reversibly to the V1a/V2 receptor subtypes; its antagonistic effect is concentration dependent. It inhibits CYP3A4 liver enzyme and elevates plasma levels of other drugs metabolized by this enzyme. It is approved only for short-term intravenous use. Infusion site reaction is the most common reason for discontinuation of the drug. In animals conivaptan increased urine volume and free water clearance. In heart failure models it improved hemodynamic parameters and free water excretion. Conivaptan has been shown to correct hyponatremia in euvolemic or hypervolemic patients. Its efficacy and safety for short-term use have led to the Food and Drug Administration (FDA) approval of its intravenous form for the correction of hyponatremia in euvolemic and hypervolemic states. Despite its ability to block the action of AVP on V1a receptors, no demonstrable benefit from this action was noted in patients with chronic compensated heart failure and it is not approved for this indication. Consideration should be given to further evaluation of its potential benefits in patients with acute decompensated heart failure.     

Vasopressin receptor antagonists: pharmacological tools and potential therapeutic agents

The present survey deals with the development and applications of non-peptidergic vasopressin receptor antagonists. The existence of at least three vasopressin receptors (V(1), V(2) and V(3) respectively) is firmly established. V(1)-receptors play a relevant role in the regulation of vascular tone, whereas V(2)-receptors are known to mediate the antidiuretic activity of vasopressin at the level of the renal collecting ducts. The V(3)-receptor appears to be involved in the release of the adreno-corticotropic hormone. Vasopressin receptor antagonists which are peptides have been known for several decades, more recently, both V(1)- and V(2)-receptor blockers which are non-peptidergic have been introduced, as well as agents with affinity for both V(1)- and V(2)-receptor subtypes. A survey of these non-peptidergic antagonists is presented here. Such compounds are useful as pharmacological tools, and they can also be thought of as therapeutic agents as therapeutic agents in cardiovascular and renal diseases. Selective V(1)- and V(2)-receptor antagonists were used to study the interaction between vasopressin receptors and sympathetic neurones. Depending on the experimental model used this interaction can occur at either the pre- or postsynaptic sites. In both cases predominantly V(1)-receptors are involved. A brief survey is given of the potential use of V-receptor antagonists in the drug therapy of syndrome of inappropriate antidiuretic hormone secretion and other water retaining disorders, congestive heart failure and certain forms of hypertension (in particular in the Negroid hypertensive patients).     

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。     

Treatment of hyponatremia: the role of lixivaptan

Hyponatremia is the most common electrolyte disorder and is associated with serious neurologic sequelae and increased mortality. Conventional treatment options for hyponatremia, such as fluid restriction, hypertonic saline, loop diuretics, demeclocycline or urea, are ineffective in the long-term. The present review considers the role of vasopressin receptor inhibitors (vaptans), focusing on lixivaptan, in the treatment of patients with euvolemic or hypervolemic hyponatremia. Lixivaptan is an oral selective V2 receptor inhibitor, which produces a significantly greater increase of serum sodium levels compared with placebo. These effects seem promising, but more trials are needed to examine whether the beneficial effect of lixivaptan on serum sodium concentration translates into clinical benefit in these patient populations.     

Management of the syndrome of inappropriate secretion of antidiuretic hormone

The etiology, pathophysiology, clinical features, diagnosis, and medical treatment of the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) are reviewed. SIADH is a common cause of hyponatremia in hospitalized patients. Increased concentrations of antidiuretic hormone (ADH) result in retention of free water, increased excretion of sodium, and hyponatremia. Symptoms generally occur only when hyponatremia is severe (less than or equal to 125 meq/L) and may include anorexia, vomiting, and confusion, followed by seizures, coma, and death. SIADH may result from a variety of diseases, as well as from the use of drugs such as chlorpropamide, carbamazepine, diuretics, and some antineoplastic agents. Diagnosis of SIADH is confirmed by demonstration of a high urine osmolality with a low plasma osmolality, in the absence of diuretic use. Immediate treatment of the symptomatic patient with SIADH includes intravenous furosemide and 3% sodium chloride injection to produce a negative free-water balance. If the underlying cause of SIADH cannot be corrected, the treatment of choice for chronic SIADH is fluid restriction. If this is not tolerated by the patient, demeclocycline can be used to induce a negative free-water balance. Urea, lithium, phenytoin, and loop diuretics have been reported to be effective, but there are few data to support their use. Future research into the treatment of SIADH must be directed at developing effective antagonists of ADH. Treatment of SIADH consists of elimination of underlying causes and restriction of fluid intake; if these measures are unsuccessful or poorly tolerated, long-term drug therapy may be indicated.     

Arginine vasopressin (AVP) and treatment with arginine vasopressin receptor antagonists (vaptans) in congestive heart failure,liver cirrhosis and syndrome of inappropriate antidiuretic hormone secretion (SIADH)

Arginine vasopressin (AVP) is the major physiological regulator of renal water excretion and blood volume. The AVP pathways of V_1aR-mediated vasoconstriction and V₂R-induced water retention represent a potentially attractive target of therapy for edematous diseases. Experimental and clinical evidence suggests beneficial effects of AVP receptor antagonists by increasing free water excretion and serum sodium levels. This review provides an update on the therapeutic implication of newly developed AVP receptor antagonists in respective disorders, such as chronic heart failure, liver cirrhosis and syndrome of inappropriate antidiuretic hormone secretion.     

Development and therapeutic indications of orally-active non-peptide vasopressin receptor antagonists

Vasopressin (AVP) is a cyclic nonapeptide hormone that exhibits many physiological effects including free water reabsorption, vasoconstriction, cellular proliferation and adrenocorticotrophic hormone (ACTH) secretion. In a healthy organism, AVP plays an important role in the homeostasis of fluid osmolality and volume status. However, in several diseases or conditions such as the syndrome of inappropriate secretion of AVP (SIADH), congestive heart failure, arterial hypertension, liver cirrhosis, nephrotic syndrome, dysmenorrhoea and ocular hypertension, AVP may play an important role in their pathophysiology. Recently, orally-active non-peptide AVP receptor antagonists were developed by random screening of chemical entities and optimisation of lead compounds. These include agents specific for the V(1)-vascular and V(2)-renal AVP receptor subtypes. Dual V(1)/V(2) AVP receptor antagonists are also being studied. Some of these non-peptide receptor antagonists have been studied extensively, while others are currently under investigation. Potential therapeutic indications for AVP receptor antagonists comprise: 1) The blockade of V(1)-vascular AVP receptors in arterial hypertension, congestive heart failure, Raynaud's syndrome, peripheral vascular disease and dysmenorrhea. 2) The blockade of V(2)-renal AVP receptors in the syndrome of inappropriate secretion of vasopressin, congestive hart failure, liver cirrhosis, nephrotic syndrome and any state of excessive retention of free water and subsequent dilutional hyponatraemia. 3) The blockade of V(3)-pituitary AVP receptors in ACTH-secreting tumours. This review examines the pharmacology of orally-active non-peptide AVP receptor antagonists and their clinical applications.     

重型颅脑损伤后中枢性低钠血症临床观察及治疗

目的探讨重型颅脑损伤后中枢性低钠血症的治疗方法及临床疗效。方法选取本院26例重型颅脑损伤后中枢性低钠血症的患者为研究对象,根据其临床特点及检查结果分为抗利尿激素分泌不当综合征（SIADH）5例和脑性盐耗综合征（CSWS）21例,给予相应的治疗,总结两组的治疗效果。结果 CSWS组的中心静脉压（CVP）、抗利尿激素（ADH）显著低于SIADH组,CSWS组血浆心钠素（ANP）值显著高于SIADH组,P〈0.05。26例患者中,有2例患者死亡,24例患者低钠血症得到纠正。结论 SIADH和CSWS是引起重型颅脑损伤后中枢性低钠血症的主要原因,应针对不同的病因采取有针对性的治疗,降低病死率。