Direct renin inhibitor aliskiren in the treatment of cardiovascular and renal diseases

The role of renin-angiotensin-aldosterone system (RAAS) in regulating the volume and composition of extracellular fluid, blood pressure (BP) as well as onset and progression of cardiovascular and renal diseases has been studied for more than 150 years. The compounds that block the vital stages of the RAAS cascade, such as ACE-inhibitors (ACEI), AT₁-receptor blockers (ARB) and aldosterone receptor antagonists, importantly extended our treatment options. However, the positive therapeutic effects of these compounds also have certain negative consequences. Administration of ACEIs and ARBs interrupts physiological feedback for renal renin release and leads to reactive elevation of circulating active renin and greater production of angiotensin I and angiotensin II with subsequent return of aldosterone secretion to the pre-treatment levels ('escape' phenomenon). These possible adverse effects of the intermediary products of incomplete RAAS blockade leading to organ complications have facilitated the efforts to develop compounds blocking the initial stages of renin-angiotensin cascade - i.e. direct renin blockers. After several years of unsuccessful attempts, the recent years have seen development of the first non-peptide, orally long-term effective renin inhibitor, aliskiren fumarate. In monotherapy or in combination with other antihypertensives (hydrochlorothiazide, ARB, ACEI), aliskiren reduces BP in a dose-dependent manner (75-600 mg/den). Aliskiren reduces plasma renin activity (PRA) and neutralises hydrochlorothiazide-induced RAAS activation. Once daily administration of the drug leads to longer than 24-hour activity and its prolonged blocking effects on the kidneys are the basis for its renoprotectivity. In addition to the significant antihypertensive effect, clinical studies also showed a range of organoprotective properties in patients with left ventricle hypertrophy (ALLAY study), heart failure (ALOFT study) and diabetic nephropathy (AVOID study). Similar to other AT₁-blockers, aliskiren has a minimum of adverse side effects. Aliskiren for hypertension therapy was launched in clinical practice in USA in 2007 (Tekturna® and combination formulation TekturnaHCl®, respectively) and shortly after that in European Union as Rasilez®. In the Czech Republic, aliskiren (Rasilez®) was released for clinical use by diabetologists and nephrologists in patients with hypertension and concomitant diabetes, nephropathy and proteinuria in doses of 150-300 mg per day on 1. 8. 2009. It is recommended as monotherapy or in combination with other antihypertensives to treat conditions with elevated PRA, including PRA elevation following diuretic, ACEI or ARB administration. Aliskiren might be used in patients who do not tolerate ACEIs as well as in patients in whom angiotensin II participates in the pathogenesis of their diseases. Renoprotective properties leading to a reduction in proteinuria and delaying renal failure progression were observed in patients with diabetic as well as non-diabetic nephropathy. The drug is the subject to similar precautions and contraindications as ACEIs and ARBs, i.e. pregnancy and bilateral renal artery stenosis. To make meaningful conclusions about the so far positive contribution of this new treatment class and its broad applicability for the therapy of hypertension and other cardiovascular diseases, it will be imperative to assess its long-term effects on morbidity and mortality as well as to compare these agents with other RAAS blockers in long-term clinical studies; this represents a research effort for another 7-8 years.

Keywords: renin inhibitors; antihypertensive activity; organoprotective effects; preliminary study results; the role in hypertension treatment