Direct renin inhibition: an evaluation of the safety and tolerability of aliskiren

Involvement of multiple cytochrome P450 isoenzymes in drug interactions between ritonavir and direct oral anticoagulants

Herein, we aimed to determine the significance of drug interactions (DIs) between ritonavir and direct oral anticoagulants (DOACs) and identify the involved cytochrome P450 (CYP) isoenzymes. Using an in vitro cocktail method with human liver microsomes (HLM), we observed that ritonavir strongly inhibited CYPs in the following order: CYP3A, CYP2C8, CYP2D6, CYP2C9, CYP2C19, CYP2B6, and CYP2J2 (IC50: 0.023-6.79 μM). The degree of CYP2J2 inhibition was inconclusive, given the substantial discrepancy between the HLM and human expression system. Selective inhibition of CYP3A decreased the O-demethylation of apixaban by only 13.4%, and the involvement of multiple CYP isoenzymes was suggested, all of which were inhibited by ritonavir. Multiple CYP isoenzymes contributed also to the metabolism of rivaroxaban. Replacement of the incubation medium with phosphate buffer instead of HEPES enhanced apixaban hydroxylation. On surveying the FDA Adverse Event Reporting System, we detected that the signal of the proportional reporting ratio of "death" and found increase for "hemoglobin decreased" (12.5-fold) and "procedural hemorrhage" (201.9-fold) on administering apixaban with ritonavir; these were far less significant for other CYP3A inhibitors. Overall, these findings suggest that co-administration of ritonavir-boosted drugs with DOACs may induce serious DIs owing to the simultaneous inhibition of multiple CYP isoenzymes.

Renin-angiotensin-aldosterone pathway modulators in chronic kidney disease: A comparative review

Chronic kidney disease presents a health challenge that has a complex underlying pathophysiology, both acquired and inherited. The pharmacotherapeutic treatment options available today lower the progression of the disease and improve the quality of life but cannot completely cure it. This poses a challenge to the healthcare provider to choose, from the available options, the best way to manage the disease as per the presentation of the patient. As of now, the recommended first line of treatment to control the blood pressure in chronic kidney disease is the administration of renin-angiotensin-aldosterone system modulators. These are represented mainly by the direct renin inhibitor, angiotensin-converting enzyme inhibitors, and angiotensin II receptor blockers. These modulators are varied in their structure and mechanisms of action, hence showing varying treatment outcomes. The choice of administration of these modulators is determined by the presentation and the co-morbidities of the patient, the availability and affordability of the treatment option, and the expertise of the healthcare provider. A direct head-to-head comparison between these significant renin-angiotensin-aldosterone system modulators is lacking, which can benefit healthcare providers and researchers. In this review, a comparison has been drawn between the direct renin inhibitor (aliskiren), angiotensin-converting enzyme inhibitors, and angiotensin II receptor blockers. This can be of significance for healthcare providers and researchers to find the particular loci of interest, either in structure or mechanism, and to intervene as per the case presentation to obtain the best possible treatment option.

Safety and efficacy of aliskiren in the treatment of hypertension: a systematic overview

INTRODUCTION

Aliskiren is the first orally active direct renin inhibitor approved for the treatment of hypertension. Aliskiren's inhibitory effect on angiotensin I generation, through renin blockade, is highly specific and long-lasting (24 hours). This feature differentiates aliskiren from traditional antihypertensive drugs.

AREAS COVERED

This paper reviews the results of various clinical trials which investigate the safety and efficacy of aliskiren on blood pressure (BP) reduction and clinical end points.

EXPERT OPINION

Aliskiren is suitable for once-daily administration. Its antihypertensive effect is comparable or superior to that of other antihypertensive agents at recommended doses. The tolerability profile of aliskiren is placebo-like at the licensed doses of 150 and 300 mg. In particular, the discontinuation of therapy due to clinical adverse events occurs similarly among patients treated with either aliskiren or placebo. Aliskiren is not recommended in association with ACE-inhibitors or angiotensin II receptor blockers in patients with type 2 diabetes and renal impairment. Pending disclosure of full results, the early termination of the ALTITUDE seems to confirm previous concerns about the safety of the dual pharmacological blockade of the renin-angiotensin system in these patients. Aliskiren is a well-tolerated antihypertensive drug that may help to achieve the recommended targets of BP control.

New class of agents for treatment of hypertension: focus on direct renin inhibition

Aliskiren, the first orally active direct renin inhibitor, is an effective antihypertensive drug with distinctive characteristics, including good blockade of the renin-angiotensin system, a prolonged duration of action, pharmacologic effects that persist after drug discontinuation, and favorable tolerability comparable with placebo. The blood pressure-lowering effect of aliskiren monotherapy is similar, if not superior, to that of other first-line antihypertensive agents, and is greatly enhanced when aliskiren is combined with various other antihypertensive medications, without any adverse drug interactions. Aliskiren is also an effective and well tolerated therapy in special populations, including diabetic, obese, and elderly hypertensives. Beyond its blood pressure-lowering efficacy, results from experimental and clinical trials suggest that aliskiren has positive effects on markers of cardiovascular and renal damage. The ASPIRE (Aliskiren Study in Post-MI patients to Reduce rEmodelling) HIGHER clinical trials program is further assessing whether the promising pharmacologic properties of aliskiren translate into reduced risk of adverse cardiovascular and renal outcomes.

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.

Renal and cardio-protective effects of direct renin inhibition: a systematic literature review

BACKGROUND

Blockade of the renin-angiotensin-aldosterone system (RAAS) at its rate-limiting step by means of renin inhibition has led to the development of direct renin inhibitors (DRIs). Given the renal and cardioprotective effects of RAAS blockade by angiotensin-converting enzyme inhibitors and angiotensin-receptor blockers, DRIs may increase the armamentarium for further organ protection. Over the last two decades the effects of DRIs on biomarkers for renal and cardiovascular disease have been investigated. This systematic review aims to delineate the effects of DRIs on surrogate markers of renal and cardiovascular function.

METHODS

MEDLINE and previous systematic reviews were searched for articles reported between 1980 and 2008. A standardized dataset was extracted from articles describing the effects of DRIs on markers of renal and cardiac damage and hard outcomes.

RESULTS

Fifty-two articles were included. Blood pressure reductions were generally insufficient using early generation DRIs. However, recent DRIs have greater blood pressure-lowering effects. Preclinical and clinical studies showed profound effects of DRIs on markers of renal function, including clear increases in renal plasma flow and reductions in albuminuria. These effects were observed either alone or in combination with other RAAS inhibitors and suggest potential large renal protective benefit. DRIs improved hemodynamic cardiovascular parameters, such as total peripheral resistance, arterial pressure and left ventricular mass index, to a similar extent as those observed with other RAAS inhibitors. Furthermore, addition of DRIs to optimal heart failure treatment resulted in further reductions in B-type natriuretic peptide.

CONCLUSIONS

Evidence from preclinical and clinical studies suggests that DRIs may have renal and cardiovascular effects beyond their ability to lower blood pressure. Results of ongoing hard outcome trials are awaited to definitively assess the renal and cardio-protective effects of these agents.

Potential roles of melatonin and chronotherapy among the new trends in hypertension treatment

The number of well-controlled hypertensives is unacceptably low worldwide. Respecting the circadian variation of blood pressure, nontraditional antihypertensives, and treatment in early stages of hypertension are potential ways to improve hypertension therapy. First, prominent variations in circadian rhythm are characteristic for blood pressure. The revolutionary MAPEC (Ambulatory Blood Pressure Monitoring and Cardiovascular Events) study, in 3000 adult hypertensives investigates, whether chronotherapy influences the cardiovascular prognosis beyond blood pressure reduction per se. Second, melatonin, statins and aliskiren are hopeful drugs for hypertension treatment. Melatonin, through its scavenging and antioxidant effects, preservation of NO availability, sympatholytic effect or specific melatonin receptor activation exerts antihypertensive and anti-remodeling effects and may be useful especially in patients with nondipping nighttime blood pressure pattern or with nocturnal hypertension and in hypertensives with left ventricular hypertrophy (LVH). Owing to its multifunctional physiological actions, this indolamine may offer cardiovascular protection far beyond its hemodynamic benefit. Statins exert several pleiotropic effects through inhibition of small guanosine triphosphate-binding proteins such as Ras and Rho. Remarkably, statins reduce blood pressure in hypertensive patients and more importantly they attenuate LVH. Addition of statins should be considered for high-risk hypertensives, for hypertensives with LVH, and possibly for high-risk prehypertensive patients. The direct renin inhibitor, aliskiren, inhibits catalytic activity of renin molecules in circulation and in the kidney, thus lowering angiotensin II levels. Furthermore, aliskiren by modifying the prorenin conformation may prevent prorenin activation. At present, aliskiren should be considered in hypertensive patients not sufficiently controlled or intolerant to other inhibitors of renin-angiotensin system. Third, TROPHY (Trial of Preventing Hypertension) is the first pharmacological intervention for prehypertensive patients revealing that treatment with angiotensin II type 1 receptor blocker attenuates hypertension development and thus decreases the risk of cardiovascular events.

Direct inhibition of renin: a physiological approach to treat hypertension and cardiovascular disease

Despite the last three decades of progress in improving cardiovascular outcomes via renin–angiotensin–aldosterone system (RAAS) blockade in hypertensive patients, substantial residual morbidity/mortality remains. Attempts to improve clinical outcomes by combining angiotensin-converting enzyme inhibitors and angiotensin receptor blockers have yielded mixed results. Adverse effects of RAAS blockade with angiotensin-converting enzyme inhibitors and angiotensin receptor blockers may relate to compensatory increases in plasma renin activity (PRA). The first-in-class direct renin inhibitor, aliskiren, blocks the RAAS at its point-of-activation, suppressing PRA and attenuating increases associated with other antihypertensives. Aliskiren (with or without other agents) provides significant and prolonged blood pressure reductions in a broad range of hypertensive patients and is well tolerated. Initial results from organ-protection studies are promising. Long-term outcomes studies should yield valuable information regarding the significance of direct renin inhibition in clinical practice.

Long-term safety, tolerability and efficacy of combination therapy with aliskiren and amlodipine in patients with hypertension

OBJECTIVE

Most patients with hypertension require antihypertensive combination therapy to achieve BP control. This study investigated the safety and efficacy of the direct renin inhibitor aliskiren combined with the calcium channel blocker amlodipine.

METHODS

Overall, 556 patients with hypertension (msDBP > or =95-<110 mmHg) received open-label aliskiren/amlodipine 150/5 mg for 2 weeks, followed by forced titration to aliskiren/amlodipine 300/10 mg for 52 weeks. Add-on hydrochlorothiazide (HCT) was permitted from week 10 to achieve BP control (<140/90 mmHg). The primary objective of the study was to evaluate the long-term safety and tolerability of aliskiren/amlodipine combination therapy; the BP-lowering efficacy of the combination was also assessed (week 54 endpoint; last observation carried forward).

TRIAL REGISTRATION

ClinicalTrials.gov identifier NCT00402103.

RESULTS

In total, 452 patients completed 54 weeks' treatment with aliskiren/amlodipine 300/10 mg, with or without add-on HCT. The most frequently reported adverse events (AEs) were peripheral edema, upper respiratory tract infection, headache and bronchitis. Peripheral edema (the most common AE), occurred in 22.7% of treated patients, and was generally mild or moderate in intensity and transient in nature. Few patients exhibited laboratory abnormalities. Aliskiren/amlodipine combination therapy provided a mean BP reduction from baseline to week 54 of 24.2/15.5 mmHg; 74.3% of patients achieved BP control. In the subgroup of patients with stage 2 hypertension (baseline msSBP > or =160 mmHg and/or msDBP > or =100 mmHg), the mean BP reduction at week 54 was 29.1/17.1 mmHg, and 67.0% of patients achieved BP control.

CONCLUSION

In this open-label study, aliskiren/amlodipine 300/10 mg combination therapy, with or without add-on HCT, effectively reduced BP, particularly in patients with stage 2 hypertension. The most common AE was peripheral edema, consistent with the known AE profile of high-dose (10 mg) amlodipine. Further studies comparing the aliskiren/amlodipine combination with the component monotherapies and other antihypertensive combinations are warranted.