Metabolism and action of urodilatin infusion in healthy volunteers

Randomized clinical trial on safety of the natriuretic peptide ularitide as treatment of refractory cirrhotic ascites

BACKGROUND

Sodium and water retention is a mainstay of the pathophysiology leading to ascites formation in patients with advanced cirrhosis. Refractory ascites denotes the most severe ascites status with limited treatment options and a poor prognosis. We investigated the efficacy and safety of the natriuretic peptide ularitide in patients with refractory cirrhotic ascites.

METHODS

We conducted a randomized placebo-controlled trial investigating ularitide to manage refractory ascites. Until trial termination after interim analyses, we randomized 17 participants in a 2:1 ratio between ularitide (n=11) and placebo (n=6). While hospitalized, the participants received treatment for up to 48 hours. The primary efficacy endpoint was a change in renal water excretion, and secondary end points included changes in renal sodium excretion rate and body weight. The starting dose was 30 ng/kg/min, though later reduced to 20 for safety reasons.

RESULTS

In contrast to the study hypothesis, the mean urine production decreased after 24 hours of ularitide treatment compared with the baseline level (22.8 vs. 47.5 mL/h, p=0.04) and decreased more in participants randomized to ularitide than placebo (24.7 vs. -6.2 mL/h, p=0.05). Ularitide did not increase the renal sodium excretion rate or reduce the weight gain. The incidence rate ratio of adverse reactions in ularitide versus placebo was 8.5 (95% CI: 2-35, p=0.003). Participants treated with ularitide developed serious blood pressure reductions, impacting their renal responsiveness.

CONCLUSIONS

Ularitide in doses of 20-30 ng/kg/min did not benefit urine production and renal sodium excretion rate in patients with refractory ascites. The participants randomized to ularitide overall developed more adverse reactions than placebo. EudraCT no. 2019-002268-28.

Rationale for and design of the TRUE-AHF trial: the effects of ularitide on the short-term clinical course and long-term mortality of patients with acute heart failure

The TRUE-AHF is a randomized, double-blind, parallel-group, placebo-controlled trial which is evaluating the effects of a 48-h infusion of ularitide (15 ng/kg/min) on the short- and long-term clinical course of patients with acute heart failure. Noteworthy features of the study include the early enrolment of patients following their initial clinical presentation (within 12 h), and entry blood pressure criteria and thresholds for the adjustment of drug infusion rates, which aim to minimize the risk of hypotension. The trial has two primary endpoints: (i) cardiovascular mortality during long-term follow-up; and (ii) the clinical course of patients during their index hospitalization. Cardiovascular mortality is evaluated in this event-driven trial by following all randomized patients for the occurrence of death until the end of the entire study without truncation at an arbitrarily determined early time point. The clinical course during the index hospitalization is evaluated using the hierarchical clinical composite endpoint, which combines information regarding changes in symptoms and the occurrence of in-hospital worsening heart failure events and death into a single ranked metric that captures interval clinical events and minimizes the likelihood of missing data and confounding due to intensification of background therapy. The design of the TRUE-AHF trial capitalizes on lessons learned from earlier trials and aims to evaluate definitively the potential benefit of ularitide in patients with acute heart failure.

TRIAL REGISTRATION

NCT01661634.

Novel vasodilators in heart failure

Heart failure is an important public health problem that is increasing in prevalence throughout the world. Not only is this condition common, but it is associated with significant morbidity and mortality as well as high costs to medical care systems. Vasodilator drugs help unload the heart and may have other effects that could benefit heart failure patients. Consequently, they have emerged as an important therapeutic approach for patients with this condition. Novel vasodilator therapies that are currently in development target new pathways, potentially giving clinicians alternate options for improving outcomes in this vulnerable population. This review focuses on investigational drugs that have the ability to dilate blood vessels amongst their therapeutic properties. These drugs include the natriuretic peptides that activate particulate guanylate cyclase, the novel agent cinaciguat that activates the soluble guanylate cyclase system, and finally a recombinant form of the naturally occurring vasodilating agent relaxin, a hormone that mediates many of the changes that allows the cardiovascular system to successfully adapt to pregnancy.

Natriuretic peptides in therapy for decompensated heart failure

Congestive heart failure (CHF) is the most frequent cause of hospitalization for patients >65 years of age and continues to be a major public health burden among the ageing population. Unlike therapy for chronic CHF, there has been only modest progress in medical treatment for acutely decompensated CHF over the past several decades. Moreover, current treatment-consisting generally of diuretic, inotropic, and vasodilatory agents-is associated with many limitations in clinical practice. Natriuretic peptides provide a promising mechanism of action in the pathophysiologic background for CHF treatment based on their vasodilatory and diuretic properties and effective inhibition of the renin-angiotensin-aldosterone system, which is activated early in the course of CHF. Nesiritide (Natrecor® or Noratak®) is a recombinant natriuretic peptide that has the same 32 amino-acid sequence as human B-type natriuretic peptide. Nesiritide has been shown to improve dyspnea and hemodynamic parameters in patients with decompensated heart failure. Ularitide is a synthetic form of urodilatin, a natriuretic peptide hormone secreted by the kidney. Recent clinical studies suggest that ularitide may play a role in managing decompensated heart failure. This review provides an update on natriuretic peptides and their therapeutic potential in advanced CHF.

Role of guanylate cyclase modulators in decompensated heart failure

In this review we investigate the role of particulate and soluble guanylate cyclase (pGC and sGC, respectively) pathways in heart failure, and several novel drugs that modify guanylate cyclase. Nesiritide and ularitide/urodilatin are natriuretic peptides with vasodilating, natriuretic and diuretic effects, acting on pGC, whilst cinaciguat (BAY 58-2667) is a novel sGC activator. Cinaciguat has a promising and novel mode of action because it can stimulate cyclic guanosine-3',5'-monophosphate synthesis by targeting sGC in its nitric oxide-insensitive, oxidised ferric (Fe(3+)) or haem-free state. Thus, cinaciguat may also be effective under oxidative stress conditions resulting in oxidised or haem-free sGC refractory to traditional organic nitrate therapies. Preliminary studies of cinaciguat in patients with acute decompensated heart failure show substantial improvements in haemodynamics and symptoms, whilst maintaining renal function.

New pharmacologic therapies for acute heart failure

Given the limitations of high-dose diuretics and vasodilators and the increasing literature showing that inotropes, regardless of the dose used, have a detrimental effect on mortality, a variety of new agents are under investigation for the treatment of pulmonary and systemic congestion and restoration of cardiac output in the setting of acute heart failure syndromes. The new therapeutic approach is based on two goals: short-term improvement in symptoms together with long-term improvement of cardiac function. This review describes new agents that are in preclinical and in clinical phases with realistic prospects: anti-endothelin, natriuretic peptides, istaroxime, levosimendan, myosin activators, and vasopressin antagonists. Those new therapeutic strategies aim to act at the cellular level to improve vessel and heart functions, with minimal side effects, together with improved sodium and water balance.

Urodilatin: a better natriuretic peptide?

The kidney natriuretic peptide urodilatin (ie, ularitide) decreases pulmonary capillary wedge pressure (PCWP) but does not cause diuresis in persons with congestive heart failure (CHF). Thirty-three percent of patients with CHF treated with 30 ng/kg/min ularitide develop hypotension with systolic blood pressures below 90 mmHg. Nesiritide and atrial natriuretic peptide lower PCWP and cause hypotension. They do not produce diuresis or natriuresis in patients with CHF. The best natriuretic peptide for treating CHF is the cardiac hormone vessel dilator which decreases PCWP and decreases systemic and pulmonary vascular resistance while simultaneously increasing cardiac output and cardiac index. What makes the vessel dilator markedly better than atrial natriuretic peptide, nesiritide, and ularitide for treatment of CHF is that it enhances sodium excretion fivefold and causes a fivefold enhanced diuresis in patients with CHF with its biologic effects lasting over 6 hours compared with less than 30 minutes for the above peptides.

Renal effects of urodilatin in healthy subjects are independent of blockade of the cyclooxygenase and angiotensin II receptor

OBJECTIVE

Little is known about the role of the renin-angiotensin-aldosterone system and the renal prostaglandins in modulating the renal vasoconstrictive and natriuretic effects of synthetic urodilatin (URO) in healthy humans.

MATERIAL AND METHODS

Twelve volunteers were pretreated in a randomized, single-blind, crossover study with losartan 50 mg a day or placebo for 5 days. Another 12 healthy subjects received indomethacin 25 mg three times a day or placebo for 4 days and a single dose on day 5. All subjects received a URO infusion (15 ng kg(-1) min(-1)) on day 5. Radioactive tracers and the lithium clearance technique were used.

RESULTS

The effective renal plasma flow (ERPF) decreased significantly during URO infusion: losartan pretreatment 573+/-63 to 461+/-76 mL/min versus placebo 540+/-89 to 432+/-90 mL/min. The urinary sodium excretion rate (UNa) increased significantly during URO infusion: losartan 335+/-115 to 502+/-134 umol/min (micromol/min) (UNa) versus placebo 386+/-142 to 476+/-137 umol/min (micromol/min) (UNa). In the indomethacin pretreated subjects, ERPF decreased significantly from 530+/-109 to 446+/-55 mL/min versus 533+/-89 to 449+/-69 mL/min in the placebo group. UNa increased significantly from 395+/-142 to 768+/-254 umol/min (micromol/min) (UNa) in the indomethacin group versus 282+/-117 to 552+/-242 umol/min (micromol/min) (UNa) in placebo.

CONCLUSION

The renal vasoconstrictive and natriuretic effects of synthetic URO are not modified by sustained inhibition of the angiotensin II receptor or the cyclooxygenase in man in a sodium replete state.

Natriuretic peptides and therapeutic applications

Since the discovery of atrial natriuretic factor by de Bold et al., there has been tremendous progress in our understanding of the physiologic, diagnostic and therapeutic roles of the natriuretic peptides (NPs) in health and disease. Natriuretic peptides are endogenous hormones that are released by the heart in response to myocardial stretch and overload. Three mammalian NPs have been identified and characterized, including atrial natriuretic peptide (ANP or atrial natriuretic factor), B-type natriuretic peptide (BNP), and C-type natriuretic peptide (CNP). In addition, Dendroaspis natriuretic peptide (DNP) has been isolated from the venom of Dendroaspis angusticeps (the green mamba snake), and urodilatin from human urine. These peptides are structurally similar and they consist of a 17-amino-acid core ring and a cysteine bridge. Both ANP and BNP bind to natriuretic peptide receptor A (NPR-A) that are expressed in the heart and other organs. Activation of NPR-A generates an increase in cyclic guanosine monophosphate, which mediates natriuresis, inhibition of renin and aldosterone, as well as vasorelaxant, anti-fibrotic, anti-hypertrophic, and lusitropic effects. The NP system thus serves as an important compensatory mechanism against neurohumoral activation in heart failure. This provides a strong rationale for the use of exogenous NPs in the management of acutely decompensated heart failure. In this article, the therapeutic applications of NPs in the acute heart failure syndromes are reviewed. Emerging therapeutic agents and areas for future research are discussed.

Effects of urodilatin on natriuresis in cirrhosis patients with sodium retention

BACKGROUND

Sodium retention and ascites are serious clinical problems in cirrhosis. Urodilatin (URO) is a peptide with paracrine effects in decreasing sodium reabsorption in the distal nephron. Our aim was to investigate the renal potency of synthetic URO on urine sodium excretion in cirrhosis patients with sodium retention and ascites.

METHODS

Seven cirrhosis patients with diuretics-resistant sodium retention received a short-term (90 min) infusion of URO in a single-blind, placebo-controlled cross-over study. In the basal state after rehydration the patients had urine sodium excretion < 50 mmol/24 h.

RESULTS

URO transiently increased urine sodium excretion from 22 +/- 16 micromol/min (mean +/- SD) to 78 +/- 41 mumol/min (P < 0.05) and there was no effect of placebo (29 +/- 14 to 44 +/- 32). The increase of URO's second messenger after the receptor, cGMP, was normal. URO had no effect on urine flow or on blood pressure. Most of the patients had highly elevated plasma levels of renin, angiotensin II and aldosterone and URO did not change these.

CONCLUSION

The short-term low-dose URO infusion increased the sodium excretion of the patients. The increase was small but systematic and potentially clinically important for such patients. The small response contrasts the preserved responsiveness of the URO receptors. The markedly activated systemic pressor hormones in cirrhosis evidently antagonized the local tubular effects of URO.