Antihypertensive Effect of Different Doses of Rostafuroxin in Comparison With Losartan

About 30% of the world adult population is affected by hypertension in industrialised countries. Elevated arterial pressure is the major cause of cardiovascular mortality and international guidelines emphasise the benefits of reducing blood pressure. The current antihypertensive strategies may reduce by 20-30% the cardiovascular risk of hypertensive patients when this efficacy is measured in clinical trials in comparison with placebo. A precise world-wide estimation of this efficacy both in term of patient burden and healthcare costs is not available; however, a recent analysis suggests that the world-wide cost of hypertension associated cardiovascular complications is around 1,000 billions dollars. Therefore, effective improvement in the diagnosis and treatment of hypertension can provide the most significant contribution to the decrease of cardiovascular mortality and reduction of the world-wide costs associated to treatment of hypertension complications.

Most of clinical trials, performed with the aim to show a reduction of the systolic blood pressure in hypertensive patients, show that reduction of systolic blood pressure is independent from the class of tested drugs as diuretics, β blockers, Ca channel blockers or inhibitors of RAS seem to have roughly the same efficacy. These findings have been used as an argument to support the notion that the antihypertensive therapy efficacy in reducing cardiovascular risk depends on the magnitude of the blood pressure fall rather than on the mechanism of action of the drug. This view contrasts with the well established notion that the secondary prevention capacity in other cardiovascular diseases differs among these classes of drugs with minor difference on the prevention of heart failure or stroke between the Ca antagonist and the other classes of drugs.

Furthermore, the recent findings on genetic of hypertension taken together with the previous data on pathophysiology of hypertension and its cardiovascular complications are consistent with the notion that a variety of heterogeneous genetic-molecular mechanisms concur to develop the rather uniform clinical picture of primary hypertension. Drugs are small molecules that produce their effects by interacting with larger molecules (proteins) whose function or reactivity may vary from one patient to another because the variations within the gene encoding them. Therefore, it is logical to postulate that the consequence of this different interaction either in term of blood pressure reduction or cardiovascular risk prevention may vary from a patient to another according to the peculiar function of the proteins involved in a given patient.

Rostafuroxin was selected during a research program aimed to synthesizing and selecting new antihypertensive compounds able to interfere with abnormalities in Na tubular reabsorption due to humoral and/or genetic mechanisms leading to essential (or genetic) hypertension. Many studies performed on the Milan hypertensive strain of rats (MHS), bearing a primary renal alteration in the ability to excrete sodium and increased blood pressure levels, showed a clear capacity of Rostafuroxin to revert these alteration, reducing systemic blood pressure.

Rostafuroxin selectively interferes with the Na-K pump correcting its functional abnormalities without interfering with other receptors involved in blood pressure regulation or hormonal homeostasis. At nanomolar concentration, rostafuroxin reduces the Na-K pump hyperactivation induced in renal cell cultures by either incubation with nanomolar ouabain concentrations or cell transfection with the 'hypertensive' variant of adducin.

Similarly, less than 1 μg/kg os of rostafuroxin is able to completely normalize both blood pressure and the increased renal Na-K pump activity in rats made hypertensive by a chronic infusion of low-dose ouabain. The antihypertensive effect of rostafuroxin is long-lasting since it is still present 24 hours after oral administration. It is not associated with changes in heart rate. Moreover, the long-term antihypertensive activity of rostafuroxin is not associated with alterations of plasma potassium, RAAS, insulin resistance, plasma lipid profile and uricemia. These findings indicate that the normalization of renal sodium handling brought about by this compound is not accompanied by the typical side effects of diuretics, such as: hypokaliemia, increased plasma levels of renin, aldosterone, triglycerides and uric acid, or insulin resistance.

Increased levels of EO and the mutated adducin are both associated with the organ complications related to hypertension, namely cardiac hypertrophy and progression toward renal insufficiency. Cardiac and renal hypertrophy is induced in rats by chronic ouabain infusion. Rostafuroxin prevents the ouabain-induced organ hypertrophy.

Rostafuroxin has shown a high safety ratio in toxicological studies and was well tolerated in previous clinical trials.

Patients with mutated adducin and increased EO plasma levels share many functional, hormonal and biochemical characteristics with MHS rats, therefore Rostafuroxin could become a first choice treatment in such patients bearing specific gene mutations and presenting high arterial blood pressure levels.

Preliminary proof of concept studies have shown ability of Rostafuroxin to reduce arterial blood pressure levels in such a patients.