Antihypertensive effects of fasidotril, a dual inhibitor of neprilysin and angiotensin-converting enzyme, in rats and humans

New drugs, procedures, and devices for hypertension

Successful treatment of hypertension is difficult despite the availability of several classes of antihypertensive drug, and the value of strategies to combat the effect of adverse lifestyle behaviours on blood pressure. In this paper, we discuss two promising therapeutic alternatives for patients with resistant hypertension: novel drugs, including new pharmacological classes (such as vasopeptidase inhibitors and aldosterone synthase inhibitors) and new molecules from present pharmacological classes with additional properties in blood-pressure or metabolism pathways; and new procedures and devices, including stimulation of arterial baroreceptors and catheter-based renal denervation. Although several pharmacological targets have been discovered with promising preclinical results, the clinical development of novel antihypertensive drugs has been more difficult and less productive than expected. The effectiveness and safety of new devices and procedures should be carefully assessed in patients with resistant hypertension, thus leading to a new era of outcome trials and evidence-based guidelines.

Dual inhibition: a novel promising pharmacological approach for different disease conditions

To overcome the problems associated with polypharmacy, which include medication non compliance, adverse drug reactions, drug-drug interactions and increased pill-burden, various strategies, such as sustained-release drugs and fixed-dose combination regimens (polypills), have been developed. Out of these, a novel and very much promising approach is the use of dual-action drugs. Amongst the dual-action drugs, there is a class of compounds known as dual inhibitors, which possess the dual inhibitory activity. The most common examples of dual inhibitors are rivastigmine, ladostigil, asenapine, phenserine, amitriptyline, clomipramine, doxepin and desipramine. This review article focuses on the conventional drugs used in different diseases which possess dual inhibition activity as well as those which are still in the preclinical/clinical phase.

A computational approach to the study of the binding mode of dual ACE/NEP inhibitors

Combined blockade of the renin-angiotensin-aldosterone system (RAAS) is an attractive therapeutic strategy for the treatment of cardiovascular diseases. Vasopeptidase inhibitors are a group of compounds capable of inhibiting more than one enzyme, which leads to potentiation of natriuretic peptide actions and suppression of the RAAS. In this study, molecular modeling has been used to elucidate key structural features that govern the binding and/or selectivity of a single compound toward the zinc catalytic sites of the N- and C-domains of the angiotensin-converting enzyme (ACE) and the neutral endopeptidase (NEP). Eleven dual inhibitors were categorized in three classes, according to their zinc binding groups. Analysis of their docked conformers revealed the molecular environment of the catalytic sites and the specific interactions between the inhibitors and amino acid residues that are important for selectivity and cooperativity. In addition, inhibitors were predicted to bind to the C-domain of the ACE with greater affinity than the N-domain, with an average difference in the free energy of binding approximately 2-3 kcal mol(-1). Residues that were identified to actively participate in the binding and stabilizing of the enzyme-inhibitor complexes were analyzed in a consensus way for both the ACE and the NEP. These atomic-level insights into enzyme-ligand binding can be used to drive new structure-based drug design processes in the quest for more selective and effective vasopeptidase inhibitors.

Sex differences in circulating and renal angiotensins of hypertensive mRen(2). Lewis but not normotensive Lewis rats

Sex differences in blood pressure are evident in experimental models and human subjects, yet the mechanisms underlying this disparity remain equivocal. The current study sought to define the extent of male-female differences in the circulating and tissue renin-angiotensin aldosterone systems (RAASs) of congenic mRen(2). Lewis and control Lewis rats. Male congenics exhibited higher systolic blood pressure than females [200 +/- 4 vs. 146 +/- 7 mmHg, P < 0.01] or Lewis males and females [113 +/- 2 vs. 112 +/- 2 mmHg, P > 0.05]. Plasma ANG II levels were twofold higher in male congenics [47 +/- 3 vs. 19 +/- 3 pM, P < 0.01] and fivefold higher than in male or female Lewis rats [6 +/- 1 vs. 6 +/- 1 pM]. ANG I levels were also highest in the males; however, plasma ANG-(1-7) was higher in female congenics. Male congenics exhibited greater circulating renin and angiotensin-converting enzyme (ACE) activities, as well as angiotensinogen, than female littermates. Renal cortical and medullary ANG II levels were also higher in the male congenics versus all the other groups; ANG I was lower in the males. Cortical ACE2 activity was higher in male congenics, yet neprilysin activity and protein were greater in the females, which may contribute to reduced renal levels of ANG II. These data reveal that sex differences in both the circulating and renal RAAS are apparent primarily in the hypertensive group. The enhanced activity of the RAAS in male congenics may contribute to the higher pressure and tissue injury evident in the strain.

Towards triple vasopeptidase inhibitors for the treatment of cardiovascular diseases

Cardiovascular diseases (CDs) are among the most encountered pathologies in western countries; with obesity reaching pandemic proportions, they are soon to become a worldwide problem. High blood pressure is the main risk factor for CDs, and its tight control is an imperative for the treatment of complications such as renal diseases, heart failure, and atherosclerosis. Blood homeostasis and vascular tone are regulated through at least 3 major closely interrelated pathways in which zinc metallopeptidases modulate the concentration of vasoactive mediators. Those extensively studied vasopeptidases were therefore rapidly targeted with specific inhibitors in order to control the levels of vasoconstrictors [angiotensin II (AII) and endothelin-1 (ET-1)] and vasodilators [bradykinin (BK) and atrial natriuretic peptide (ANP)], thereby controlling blood pressure. The first class of inhibitors to be developed were against angiotensin-converting enzyme (ACE), recently followed by dual inhibitors of ACE/neprylisin (NEP), NEP/endothelin-converting enzyme (ECE), and finally triple ACE/NEP/ECE inhibitors. The dual and triple inhibitors are defined as vasopeptidase inhibitors (VPI). In addition to their ability to effectively lower blood pressure in hypertensive patients, drugs targeting these enzymes also displayed antiinflammatory and antifibrotic activities. The major point emerging from recent studies undertaken to improve the management of CDs is that the combined action of different therapeutic strategies (ie, simultaneous modulation of several neurohumoral mediators) shows better results than conservative therapeutic approaches. In this review, we historically present the advances made in the comprehension of the different mechanisms of blood pressure regulation and some of the drugs that arose from this understanding.

A randomized, double-blind, placebo-controlled, parallel-group study to assess the efficacy and safety of dual ACE/NEP inhibitor GW660511X in mild-to-moderate hypertensive patients

This multicentre, double-blind, placebo-controlled, parallel-group study determined the efficacy and safety of GW660511 200 mg, a dual inhibitor of angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP), in mild-to-moderate hypertensive patients (diastolic blood pressure (DBP), > or =90 and < or =109 mm Hg; systolic blood pressure (SBP), > or =150 and < or =180 mm Hg). After a single-blind 2- to 4-week placebo run-in period, 123 patients (aged 18-65 years) were randomized to either placebo (n=62) or to active treatment (n=61) consisting of two consecutive 3-day dose titration periods of GW660511X 50 mg once daily and 100 mg once daily followed by GW660511X 200 mg once daily for 14 days. GW660511X 200 mg significantly lowered (baseline and placebo-corrected) both trough mean cuff SBP (-8.00 mm Hg, P=0.002) and DBP (-5.38 mm Hg, P=0.003). GW660511X 200 mg significantly reduced placebo-corrected mean 24-h and daytime but not night-time ambulatory SBP and DBP. Over the 0-24 h time period following GW660511X 200 mg, there were significant (P<0.001) reductions in serum ACE activity and significant (P<0.001) increases in plasma ANP concentration compared with placebo in terms of both peak and trough effects. In addition, treatment with GW660511X 200 mg significantly (P=0.003) increased (placebo-corrected, 1.52-fold) urinary excretion of cGMP over the 0-24 h interval. Treatment-related adverse events were experienced by 43% of the patients administered GW660511X 200 mg and 44% of those dosed with placebo with headache the most commonly reported. In conclusion, GW660511X 200 mg is an effective antihypertensive in mild-to-moderate hypertensive patients with potent effects on biological markers of ACE and NEP inhibition.

Brain neprilysin activity and susceptibility to transgene-induced Alzheimer amyloidosis

Neprilysin (NEP) is a zinc metalloproteinase that degrades enkephalins, endothelins, and the Alzheimer's disease amyloid beta (Abeta) peptides. NEP-deficient mice possess increased levels of brain Abeta(1-40) and Abeta(1-42). The objective of this study was to determine whether tissue NEP specific activity differs according to age and/or across mouse strains, especially those strains predisposed toward formation of Abeta-amyloid plaques following overexpression of the human Alzheimer amyloid precursor protein (APP). The C57Bl/6J mouse strain appears to be relatively susceptible to cerebral amyloidosis, whereas the Swiss Webster (SW) strain appears more resistant. We investigated whether NEP specific activity in brain and kidney homogenates from SW and C57 mice of 6, 40, and 80 weeks old varied according to mouse strain, age, and gender. Among the variables tested, NEP specific activity varied most dramatically across mouse strain, with the kidney and brain of SW mice displaying the highest activities. Aging was associated with a reduction in brain NEP specific activity in both strains. Gender-specific differences were identified in kidney but not in brain. We conclude that aging- and strain-dependent differences in NEP specific activity may play a role in the differential susceptibility of some mouse strains for developing cerebral amyloidosis following human APP overexpression.

Vasopeptidase inhibitors: will they have a role in clinical practice?

The human cardiovascular system is regulated by haemodynamic, neurohumoral and structural mechanisms. The endothelium and the neurohumoral system play a key role in modulating both vascular tone and structure by producing vasoactive substances, and in the modulation of blood cell adhesion. Although the neurohormonal systems are essential in vascular homeostasis, they become maladaptive in conditions such as hypertension, coronary disease and heart failure. The clinical success of blocking the renin-angiotensin system by angiotensin converting enzyme (ACE)-inhibitors and the sympathetic nerve system by beta-blockers demonstrates the importance of neurohumoral blockade. The inadequate effect of angiotensin converting enzyme (ACE) or neutral endopeptidase (NEP) inhibitor monotherapy seen in some patients treated for hypertension or congestive heart failure, and the promising effect seen after their combination, led to the development of drugs that simultaneously inhibit both enzyme systems. Neutral endopeptidase, like ACE, is an endothelial cell surface zinc metallopeptidase with similar structure and catalytic site to ACE. NEP is the major enzymatic pathway for degradation of natriuretic peptides. The natriuretic peptide system can be viewed as the endogenous inhibitor of the renin angiotensin system. The dual metalloprotease inhibitors of ACE and NEP, called vasopeptidase inhibitors therefore represent a new and attractive therapeutic strategy for the treatment of cardiovascular disease. The ability to add incremental benefit over already proven therapy, with an acceptable side-effect profile however, is questionable in this new class of agents.

Transmembrane proteases in cell growth and invasion: new contributors to angiogenesis?

Transmembrane proteases (TPs) are proteins anchored in the plasma membrane with their catalytic site exposed to the external surface of the membrane. TPs are widely expressed, and their dysregulated expression is associated with cancer, infection, inflammation, autoimmune and cardiovascular diseases, all diseases where angiogenesis is part of the pathology. TPs participate in extracellular proteolysis (degradation of extracellular matrix components, regulation of chemokine activity, release of membrane-anchored cytokines, cytokine receptors and adhesion molecules) and influence cell functions (growth, secretion of angiogenic molecules, motility). Recent attention has been focused on the ADAM-17 (a disintegrin and metalloprotease)/TACE/CD156q, the MT1-MMP (membrane-type-1 matrix metallo proteinase)/MMP-14, and the ectopeptidases aminopeptidase N (APN/CD13), dipeptidyl peptidase IV (DPPIV/CD26) and angiotensin-converting enzyme (ACE/CD143), that appear to have a critical role in angiogenesis. This article summarizes current knowledge on these TPs, and reviews recent investigations that document their participation during angiogenic-related events. Through their multiple roles, TPs may thereby provide critical links in angiogenesis.

Dual ACE and Neutral Endopeptidase Inhibitors

Elevated blood pressure is a risk factor for a variety of cardiovascular disorders, including coronary heart disease, peripheral vascular disease, cardiac failure and cerebrovascular disease. The prevailing view is that an elevated systolic rather than diastolic blood pressure is the major contributor in mortality and morbidity attributed to cardiovascular disorders. Isolated high systolic blood pressure, especially in the elderly, is a major risk factor and should undoubtedly be a target for drug treatment. In the general population, systolic and diastolic blood pressure are highly correlated, and thus it is difficult to dissociate the effects of these two components of the blood pressure and specifically ascribe cardiovascular risk factors to just elevated systolic blood pressure. Therefore, the goal in therapy of an individual with hypertension must be to reduce elevated systolic and diastolic blood pressure in order to reduce mortality and morbidity. ACE and neutral peptidase inhibitors are a new class of drugs that may be beneficial in the treatment of patients with hypertension and heart failure. They may also be useful in the treatment of diabetic patients with hypertension and/or heart failure. Drugs of this class are dual inhibitors of ACE and neutral endopeptidase, and are capable of affecting vascular tone and fluid balance. They are capable of producing vasodilatation by virtue of inhibiting the production of angiotensin II, degradation of natriuretic peptides and bradykinin. They also appear to promote natriuresis and diuresis by amplifying the actions of natriuretic peptidase and reducing aldosterone effects. In addition, they should also attenuate trophogenic actions of the renin angiotensin system and the sympathetic nervous system. Omapatrilat is one drug that appears to be at the advanced stages of clinical development. This drug has been shown to be quite effective in the treatment of hypertension. Evidence also seems to indicate that treatment with omapatrilat results in a higher tendency towards preventing death and worsening heart failure when compared with treatment with a pure ACE inhibitor in patients with advanced heart failure. Overall safety with omapatrilat appears to be good, but like other ACE inhibitors the incidence of cough is higher when compared with placebo. Other common adverse effects noted are headaches, facial flushing/warm sensation, dizziness, nausea and dyspnoea. Of greater concern is the occurrence of angio-oedema, the true incidence of which remains to be fully established as part of the published medical literature.

Vasopeptidase inhibitors

Vasopeptidase inhibitors are a new class of drugs that have dual inhibitory effects on two key enzymes involved in the metabolism of vasoactive peptides. Essentially, they inhibit angiotensin-converting enzyme (ACE), thereby blocking the generation of angiotensin II (Ang II); at the same time they prevent the breakdown of natriuretic peptides by the enzyme neutral endopeptidase. The combination of reduction of Ang II on a background of increased natriuretic peptide activity has several potential advantages for the treatment of cardiovascular and renal disease and in particular, hypertension and congestive heart failure (CHF). Several vasopeptidase inhibitors, such as sampatrilat, fasidotril, gemopatrilat and omapatrilat (Vanlev, the most clinically developed vasopeptidase inhibitor to date) are under intensive clinical investigation. Recent clinical trials have demonstrated effective antihypertensive activity in hypertension, independent of age, renin and salt status or ethnic origin, and have also highlighted the potential for vasopeptidase inhibition as a new therapeutic modality for the treatment of CHF. Moreover, ongoing research suggests that this new class of drugs may be an important approach, not only for the treatment of hypertension and of conditions associated with overt volume overload but also for ischaemic heart disease.

Clinical applications of arterial stiffness: therapeutics and pharmacology

This short review describes the effects of drugs and nonpharmacologic treatments on large artery stiffness in clinical trials. Arterial stiffness is generally accepted as a predictive factor for cardiovascular morbidity and mortality. The drug-induced reduction in arterial stiffness may parallel the reduction in cardiovascular work. This review summarizes the discussion of a task force that worked on the therapeutic aspects during a Consensus Conference on the 'Clinical applications of arterial stiffness," held in Paris on June 17, 2000. The effects of drugs on arterial stiffness are detailed in patients with hypertension, heart failure, and other arterial diseases. Other issues are raised, including the reversibility of arterial changes following pharmacologic treatment, and the possibility for nonpharmacologic treatment to be effective on arterial stiffness. Directions for future therapeutic trials are suggested.

A review of vasopeptidase inhibitors: a new modality in the treatment of hypertension and chronic heart failure

Vasopeptidase inhibitors are a group of agents capable of inhibiting neutral endopeptidase and angiotensin-converting enzymes, which leads to potentiation of natriuretic peptide actions and suppression of the renin-angiotensin-aldosterone system. With this distinctively characteristic mechanism, these agents have emerged as a new drug class for management of hypertension and heart failure. Several vasopeptidase inhibitors are under clinical investigation. Omapatrilat is the most studied agent in this class. Clinical studies of omapatrilat in hypertension have consistently shown the agent's effectiveness in a variety of patient populations. In patients with heart failure, omapatrilat significantly improved neurohormonal and hemodynamic status. Long-term effects of omapatrilat in patients with heart failure recently were compared with those of conventional therapy in a large phase II trial. Results of the study appear promising. Large clinical trials are ongoing, and additional information regarding safety and efficacy from these studies may help define the place in therapy for this agent.

Vasopeptidase inhibitors

Vasopeptidase inhibitors are a new class of cardiovascular drug that simultaneously inhibit both neutral endopeptidase and angiotensin-converting enzyme (ACE). They increase the availability of peptides that have vasodilatory and other vascular effects; they also inhibit production of angiotensin II. In animal models vasopeptidase inhibitors decrease blood pressure in low, medium, and high renin forms of hypertension, and they also appear to confer benefits in models of heart failure and ischaemic heart disease. Studies in human hypertension show that these agents are effective in decreasing blood pressure regardless of race or age. Experience with omapatrilat, the most clinically advanced of these drugs, has shown it to be more effective than currently available ACE inhibitors or other widely used antihypertensive agents. Studies with omapatrilat in congestive heart failure have shown beneficial effects on haemodynamics and symptoms. The vasopeptidase inhibitors appear to have safety profiles similar to ACE inhibitors, though the frequency of side-effects such as angio-oedema and cough remains to be established. Large trials with clinical endpoints, some already in progress, are needed to establish the place of this class of drug beside that of established therapies in conditions such as hypertension, heart failure, ischaemic heart disease, and nephropathy.

Novel angiotensin II inhibitors in cardiovascular medicine

Blockade of the renin-angiotensin-aldosterone cascade is now recognised as a very effective approach to treat hypertensive, heart failure and high cardiovascular risk patients and to retard the development of renal failure. The purpose of this review is to discuss the state of development of currently available drugs blocking the renin-angiotensin system, such as angiotensin converting enzyme (ACE) inhibitors, renin inhibitors and angiotensin II receptor antagonists, with a special emphasis on the results of the most recent trials conducted with AT(2) receptor antagonists in heart failure and Type 2 diabetes. In addition, the future perspectives of drugs with dual mechanisms of action, such as NEP/ACE inhibitors, also named vasopeptidase inhibitors, are presented.

Novel approaches to the treatment of progressive renal disease

Diabetes and hypertension are major contributors to the increasing incidence of progressive renal disease. In addition to more potent antihypertensive agents that block the renin-angiotensin system, drugs that modulate other pathogenetic pathways are also in development. Recent preclinical studies indicate that compounds that interfere with the formation and action of advanced glycation end products may have a role in the treatment and prevention of diabetic nephropathy, as may agents targeting the activity of protein kinase C.