Renin inhibition with aliskiren

Aliskiren-Loaded Nanoparticles Downregulate (Pro)renin Receptor and ACE Gene Expression in the Heart of Spontaneously Hypertensive Rats: Effect on NADPH Oxidase

We aimed to determine effects of aliskiren, a direct renin inhibitor, loaded onto polymeric nanoparticles on the (pro)renin receptor (Atp6ap2), angiotensin II type 1 receptor (Agtr1), and angiotensin-converting enzyme (ACE) gene expression in the heart of spontaneously hypertensive rats (SHR). Twelve-week-old male SHRs were divided into an untreated group and groups treated with powdered aliskiren or aliskiren-loaded nanoparticles (25 mg/kg/day). After three weeks, the accumulation of aliskiren, distribution of polymeric nanoparticles, gene expression of Atp6ap2 and Agtr1 receptors and ACE, and protein expression of NADPH oxidase along with the conjugated diene (CD) concentration were analyzed. The accumulation of aliskiren in the heart was higher in the aliskiren-loaded nanoparticle group than in the powdered group. The fluorescent signals of nanoparticles were visible in cardiomyocytes, vessel walls, and erythrocytes. Aliskiren-loaded nanoparticles decreased the gene expression of Atp6ap2 and ACE, while not affecting Agtr1. Both forms of aliskiren decreased the protein expression of NADPH oxidase, with a more pronounced effect observed in the aliskiren-loaded nanoparticle group. CD concentration was decreased only in the aliskiren-loaded nanoparticle group. We hypothesize that aliskiren-loaded nanoparticle-mediated downregulation of Atp6ap2 and ACE may contribute to a decrease in ROS generation with beneficial effects in the heart. Moreover, polymeric nanoparticles may represent a promising tool for targeted delivery of aliskiren.

Synthetic strategies, SAR studies, and computer modeling of indole 2 and 3-carboxamides as the strong enzyme inhibitors: a review

Abstract

Indole derivatives have been the focus of many researchers in the study of pharmaceutical compounds for many years. Researchers have investigated the effect of carboxamide moiety at positions 2 and 3, giving unique inhibitory properties to these compounds. The presence of carboxamide moiety in indole derivatives causes hydrogen bonds with a variety of enzymes and proteins, which in many cases, inhibits their activity. In this review, synthetic strategies of indole 2 and 3-carboxamide derivatives, the type, and mode of interaction of these derivatives against HLGP, HIV-1, renin enzyme, and structure–activity studies of these compounds were investigated. It is hoped that indole scaffolds will be tested in the future for maximum activity in pharmacological compounds.

Graphic abstract

Formulation and in vivo evaluation of aliskiren-loaded poly(lactic-co-glycolic) acid nanoparticles

Aliskiren (ALS) is a direct renin inhibitor with low bioavailability and high drug cost. The goal of this study was to increase the bioavailability of ALS through nanoformulation. The optimized formulation was then evaluated in spontaneously hypertensive rats (SHRs). We developed an ALS poly(lactic- co-glycolic) acid nanoparticle (ALS-NP) through the emulsion–diffusion–evaporation method with various solvents, stabilizer concentrations, and centrifugation speeds. SHRs were orally dosed with 30 mg/kg ALS or dose equivalent ALS-NP. Several parameters were assayed in plasma and/or urine at baseline and 24 h post-dose, while pharmacokinetic analysis included serial sampling. The optimum formulation was found with ethyl acetate, a 1.00% w/v didodecyldimethylammonium bromide concentration, and a 10,000 r/min (15,554 g) centrifugation speed. A 168% relative bioavailability was observed as a result of ALS-NP administration along with significant, as determined by Student’s t-test, increases in the maximum ALS plasma concentration ( p = 0.0189) and the area under the plasma concentration–time curve from 0 to infinity ( p = 0.0095). Conversely, a reduction was found in oral volume of distribution ( p = 0.0009) and oral clearance ( p = 0.0298). Blood urea nitrogen increased significantly after dosing in both groups ( p < 0.0001 and p < 0.0001); however, no statistical difference was found between endpoint levels ( p > 0.05) following one-way analysis of variance (ANOVA). Kidney injury molecule-1 increased following ALS dosing ( p = 0.0486), while ALS-NP showed a decrease ( p = 0.027) which was also significantly decreased compared to ALS-Final ( p = 0.0008) when examined using two-way ANOVA. Urinary potassium excretion decreased significantly, as shown by two-way ANOVA, only in the ALS group ( p = 0.0274) which was also significantly reduced compared to ALS-NP-Final ( p = 0.016). Using the current formulation and at the dosage tested, ALS-NP showed a more favorable pharmacokinetic profile and positive kidney changes compared to ALS in regard to select outcomes. Thus, NP formulation may further improve ALS renoprotection in addition to increasing bioavailabilty.

Randomised, double-blind, placebo-controlled, dose-escalating phase I study of QGC001, a centrally acting aminopeptidase a inhibitor prodrug

BACKGROUND AND OBJECTIVES

Inhibition of brain aminopeptidase A (APA), which converts angiotensin II into angiotensin III, has emerged as a novel antihypertensive treatment, as demonstrated in several experimental animal models. QGC001 (originally named RB150) is a prodrug of the specific and selective APA inhibitor EC33, and as such it is the prototype of a new class of centrally acting antihypertensive agents. Given by the oral route in hypertensive rats, it enters the brain and generates EC33, which blocks the brain renin-angiotensin system activity and normalises blood pressure. The aim of the present study was to evaluate the safety, pharmacokinetics and pharmacodynamic effects of QGC001 in humans.

DESIGN AND METHODS

Fifty-six healthy male volunteers were randomly assigned to receive in double-blind and fasted conditions single oral doses of 10, 50, 125, 250, 500, 750, 1,000 and 1,250 mg of QGC001 (n = 6/dose) or placebo (n = 2/dose). We measured plasma and urine concentrations of both QGC001 and EC33 by liquid chromatography-tandem mass spectrometry, plasma renin concentrations (PRC), plasma and free urine aldosterone (PAldo and UAldo), plasma copeptine (PCop), and plasma and urine cortisol (PCort and UCort) concentrations, and supine systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR) at various time points.

RESULTS

All doses of QGC001 were clinically and biologically well-tolerated. Peak plasma concentrations (Cmax) of QGC001 and EC33 increased linearly with the dose, with a median time to reach Cmax (tmax) of 1.5 h for QGC001 and 3.0 h for EC33. The median plasma elimination half-life of QGC001 was 1.6 h consistently throughout doses. Urinary excretion of QGC001 and EC33 was below 2% of the administered dose. When compared with placebo, QGC001 did not significantly change PRC, PAldo, UAldo, PCop, PCort or UCort. No significant change was observed for supine HR, SBP and DBP in any treatment group.

CONCLUSION

Single oral administration of QGC001 up to 1,250 mg in healthy volunteers was well-tolerated. Following oral administration, QGC001 is absorbed via the gastrointestinal tract and converted partially into its active metabolite EC33 in plasma. As in animal experiments, in normotensive subjects QGC001 had no effect on the systemic renin-angiotensin-aldosterone parameters and on PCop concentrations, a marker of vasopressin release. In normotensive subjects, a single dose of QCG001 had no effect on SBP, DBP or HR. These data support further evaluation of multiple oral doses of QGC001 in human volunteers and its clinical efficacy in hypertensive patients.

How are physicians prescribing the direct renin inhibitor aliskiren in the management of essential hypertension? A French observational study

OBJECTIVES

The aim of this French observational study was to evaluate how the direct renin inhibitor aliskiren is being prescribed to treat hypertension by primary care providers (PCPs) and office-based cardiologists.

METHODS

Each participating physician included the first three consecutive hypertensive patients who had been prescribed aliskiren at least 4 weeks beforehand and noted whether aliskiren was prescribed: alone or as part of a combination; as first-line therapy, to replace another drug or as an add-on therapy.

RESULTS

Five thousand, four hundred and eleven patients were analyzed [mean age, 63; 58% men; 24% diabetic; mean blood pressure (BP) 148/85 mmHg]. A total of 23.6% of patients had a controlled BP. Aliskiren was prescribed alone in 49.4% patients and as part of a combination in 50.6% (bitherapy 28.3%, tritherapy 14.7%, and quadri+therapy 7.6%), at the higher recommended dosage (300 mg daily) to two-thirds of cases. Aliskiren replaced another drug in 71.9% [mainly an angiotensin receptor blocker (ARB) or an angiotensin-converting enzyme inhibitor (ACEi)] and was added to an existing regimen in 22.5%. For bitherapy, aliskiren was combined with a diuretic (D; 39%) or a calcium channel blocker (CCB; 32%). For tritherapy, it was prescribed with CCB and D in 28% and β-blocker and D in 26%. In 8.9% of patients, aliskiren was prescribed with an ACEi or an ARB.

CONCLUSION

French physicians are generally following the current prescribing recommendations for aliskiren, but the place of this new class of antihypertensive in the management of essential hypertension will become clearer with longer experience, especially concerning effective doses and combinations.

The role of direct renin inhibitors in the treatment of the hypertensive diabetic patient

Hypertensive patients with diabetes exhibit an increased risk for cardiovascular complications, such as acute coronary syndrome, stroke, heart failure and chronic kidney disease (CKD). These two chronic diseases are linked to a high rate of morbidity and mortality and for this reason it is important for the clinician to recognize the need for effective treatment of hypertension, which can require combination therapy to achieve blood pressure (BP) goals. Direct renin inhibitors (DRIs) may be useful in combination with angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin II receptor blockers (ARBs) as they provide a more complete blockade of the renin-angiotensin-aldosterone system (RAAS), effectively suppressing residual angiotensin II production and the counter-regulatory increase in plasma renin activity observed in patients receiving monotherapy with ACEIs or ARBs. Some questions regarding the action of aliskiren in cardiovascular and renal disorders are open. In particular, the combination therapy of aliskiren and a RAAS blocker in diabetic hypertensive patients with CKD is controversial. Several published studies demonstrated that aliskiren is suitable for once-daily administration and its antihypertensive effect is comparable or superior to that of other antihypertensive agents at recommended doses, with a good tolerability profile. At the moment the association with ACEIs and ARBs is not recommended in patients with type 2 diabetes mellitus (T2DM) and renal impairment even if a recent published open-label study of low-dose aliskiren (150 mg/daily) in association with ACEIs or ARBs has demonstrated a good tolerability profile without the adverse events found in other studies. This review provides a brief overview of RAAS blocking, in particular the rationale and clinical evidence supporting the use of the DRI aliskiren, in high-risk patients with T2DM.

Renin inhibitors and cardiovascular and renal protection: an endless quest?

Renin-angiotensin system (RAS) blockade with angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs) has become a major therapeutic approach in medicine since the end of the 1970's. Although these molecules were the first RAS blockers to be developed, it would have been physiologically and pharmacologically more pertinent to selectively inhibit renin itself. Indeed, the reaction between renin and its unique substrate, angiotensinogen, is the highly regulated and rate-limiting step of the RAS. The development of direct renin inhibitors (DRI) has been a slow and complex process and the synthesis of the first orally active DRI, aliskiren, was only achieved in the 2000's. Its pharmacological profile in patients with hypertension, diabetic nephropathy or heart failure, in addition to experimental evidence, suggests that aliskiren may be of value for the management of cardiovascular and renal diseases. However, the long-term, randomized, placebo-controlled, morbidity/mortality trial, ALTITUDE, which included 8,600 patients with type 2 diabetes, proteinuria and a high cardiovascular risk already treated with ACE inhibitors or ARBs was terminated in December 2011 because of futility and an increased incidence of serious adverse events in the aliskiren 300 mg arm. Other long-term studies are still ongoing to demonstrate the safety and efficacy of aliskiren to reduce cardiovascular morbidity and mortality in patients with heart failure and in elderly individuals (≥65 years) with systolic blood pressure of 130 to 159 mmHg, no overt cardiovascular disease, and a high cardiovascular risk profile. In the meantime, according to the European Medicines Agency recommendations, aliskiren should not be prescribed to diabetic patients in combination with ACE inhibitors or ARBs.

Renin and cardiovascular disease: Worn-out path, or new direction

Inhibition of the renin angiotensin system has beneficial effects in cardiovascular prevention and treatment. The advent of orally active direct renin inhibitors adds a novel approach to antagonism of the renin-angiotensin system. Inhibition of the first and rate-limiting step of the renin angiotensin cascade offers theoretical advantages over downstream blockade. However, the recent discovery of the (pro)renin receptor which binds both renin and prorenin, and which can not only augment catalytic activity of both renin and prorenin in converting angiotensinogen to angiotensin I, but also signal intracellularly via various pathways to modulate gene expression, adds a significant level of complexity to the field. In this review, we will examine the basic and clinical data on renin and its inhibition in the context of cardiovascular pathophysiology.

Direct renin inhibitors as antihypertensive agents

Hypertension, a serious disease affecting almost a billion people (25% of adults) worldwide, is a major modifiable risk factor for cardiovascular (CV) and renal disease. Despite numerous advances in the pharmacologic treatment of high blood pressure (BP) and availability of several antihypertensive drugs to treat hypertension, a significant proportion of treated hypertensive patients still have uncontrolled high BP, and thus, face serious morbidity and mortality. Furthermore, it is not sufficient to aim for optimum BP control, but to treat all CV risk factors, protect end-organ damage, prevent progression of disease, and prevent long-range adverse effects of the drugs. Therefore, new therapeutic modalities have to be developed to achieve the above objectives. Some years ago, investigators identified renin inhibition as the preferred pharmacologic approach to blockade of the renin-angiotensin system. Renin is a monospecific enzyme that catalyzes the rate-limiting step in the synthesis of angiotensin II. Amplified enzymatic activity and additional physiologic effects occur when renin and prorenin bind to the (pro)renin receptor. Until very recently, development of clinically effective renin inhibitors remained elusive but molecular modeling was used to develop aliskiren and other renin inhibitors that produce sustained suppression of plasma renin activity after oral administration with a dose-dependent BP. Additional studies will ultimately determine the place of renin inhibition in the treatment of hypertension and related CV disorders.

Blocking the RAAS at different levels: an update on the use of the direct renin inhibitors alone and in combination

The renin–angiotensin–aldosterone system (RAAS), an important regulator of blood pressure and mediator of hypertension-related complications, is a prime target for cardiovascular drug therapy. Angiotensin-converting enzyme inhibitors (ACEIs) were the first drugs to be used to block the RAAS. Angiotensin II receptor blockers (ARBs) have also been shown to be equally effective for treatment. Although these drugs are highly effective and are widely used in the management of hypertension, current treatment regimens with ACEIs and ARBs are unable to completely suppress the RAAS. Combinations of ACEIs and ARBs have been shown to be superior than to either agent alone for some, but certainly not all, composite cardiovascular and kidney outcomes, but dual RAAS blockade with the combination of an ACEI and an ARB is sometimes associated with an increase in the risk for adverse events, primarily hyperkalemia and worsening renal function. The recent introduction of the direct renin inhibitor, aliskiren, has made available new combination strategies to obtain a more complete blockade of the RAAS with fewer adverse events. Renin system blockade with aliskiren and another RAAS agent has been, and still is, the subject of many large-scale clinical trials and furthermore, is already available in some countries as a fixed combination.