In patients hospitalized with HF, istaroxime improved PCWP and possibly diastolic function. In contrast to available inotropes, istaroxime increased SBP and decreased HR. (A Phase II Trial to Assess Hemodynamic Effects of Istaroxime in Pts With Worsening HF and Reduced LV Systolic Function [HORIZON-HF]; NCT00616161).

The genetic and environmental heterogeneity of essential hypertension is responsible for the individual variability of antihypertensive therapy. An understanding of the molecular mechanisms underlying hypertension and related organ complications is a key aspect for developing new, effective, and safe antihypertensive agents able to cure the cause of the disease. Two mechanisms, among others, are involved in determining the abnormalities of tubular Na+ reabsorption observed in essential hypertension: the polymorphism of the cytoskeletal protein alpha-adducin and the increased circulating levels of endogenous ouabain (EO). Both lead to increased activity and expression of the renal Na+-K+ pump, the driving force for tubular Na transport. Morphological and functional vascular alterations have also been associated with EO. Rostafuroxin (PST 2238) is a new oral antihypertensive agent able to selectively antagonize EO, adducin pressor, and molecular effects. It is endowed with high potency and efficacy in reducing blood pressure and preventing organ hypertrophy in animal models representative of both adducin and EO mechanisms. At molecular level, in the kidney, Rostafuroxin antagonizes EO triggering of the Src-epidermal growth factor receptor (EGFr)-dependent signaling pathway leading to renal Na+-K+ pump, and ERK tyrosine phosphorylation and activation. In the vasculature, it normalizes the increased myogenic tone caused by nanomolar ouabain. A very high safety ratio and an absence of interaction with other mechanisms involved in blood pressure regulation, together with initial evidence of high tolerability and efficacy in hypertensive patients, indicate Rostafuroxin as the first example of a new class of antihypertensive agents designed to antagonize adducin and EO-hypertensive mechanisms.

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Twenty years of genetic studies have not contributed to improvement in the clinical management of primary arterial hypertension. Genetic heterogeneity, epistatic-environmental-biological interactions, and the pathophysiological complexity of hypertension have hampered the clinical application of genetic findings. In the companion article, we furnished data from rodents and human cells demonstrating two hypertension-triggering mechanisms-variants of adducin and elevated concentrations of endogenous ouabain (within a particular range)-and their selective inhibition by the drug rostafuroxin. Here, we have investigated the relationship between variants of genes encoding enzymes for ouabain synthesis [LSS (lanosterol synthase) and HSD3B1 (hydroxy-d-5-steroid dehydrogenase, 3b-and steroid d-isomerase 1)], ouabain transport {MDR1/ABCB1 [ATP-binding cassette, sub-family B (MDR/TAP), member 1]}, and adducin activity [ADD1 (adducin 1) and ADD3], and the responses to antihypertensive medications. We determined the presence of these variants in newly recruited, never-treated patients. The genetic profile defined by these variants predicted the antihypertensive effect of rostafuroxin (a mean placebo-corrected systolic blood pressure fall of 14 millimeters of mercury) but not that of losartan or hydrochlorothiazide. The magnitude of the rostafuroxin antihypertensive effect was twice that of antihypertensive drugs recently tested in phase 2 clinical trials. One-quarter of patients with primary hypertension display these variants of adducin or concentrations of endogenous ouabain and would be expected to respond to therapy with rostafuroxin. Because the mechanisms that are inhibited by rostafuroxin also underlie hypertensionrelated organ damage, this drug may also reduce the cardiovascular risk in these patients beyond that expected by the reduction in systolic blood pressure alone.

Acute heart failure syndromes (AHFS) are associated with the rapid onset of heart failure (HF) signs and symptoms. Hospitalizations for AHFS continue to rise and are associated with significant mortality and morbidity. Several pharmacological agents are currently approved for the treatment of AHFS, but their use is associated with an increase in short-term mortality. There is a need for new agents that can be given in the acute setting with increased efficacy and safety. Istaroxime is a unique agent with both inotropic and lusitropic properties which is currently being studied for the treatment of AHFS. Istaroxime inhibits the sodium-potassium adenosine triphosphatase (ATPase) and stimulates the sarcoplasmic reticulum calcium ATPase isoform 2 (SERCA-2) thereby improving contractility and diastolic relaxation. Early data from human studies reveal that istaroxime decreases pulmonary capillary wedge pressure (PCWP) and possibly improves diastolic function without causing a significant change in heart rate (HR), blood pressure, ischemic or arrhythmic events. Most commonly reported side effects were related to gastrointestinal intolerance and were dose related. In conclusion, istaroxime is a novel agent being investigated for the treatment of AHFS whose mechanism of action and cellular targets make it a promising therapy. Further studies with longer infusion times in patients with hypotension are required to confirm its efficacy and safety.