PROTECT-1: A Study of the Selective A1 Adenosine Receptor Antagonist KW-3902 for Patients Hospitalized With Acute HF and Volume Overload to Assess Treatment Effect on Congestion and Renal Function

Loop diuretics are generally first line therapy in patients hospitalized with acute heart failure syndrome (AHFS). Their use far exceeds that of vasoactive agents. Tubuloglomerular feedback (TGF) is the body's compensatory response to avoid excess fluid loss, and it is activated when elevated sodium concentrations in the distal tubule are detected. TGF is proposed as a contributing factor for the observed diuretic resistance that occurs in patients with heart failure. Higher doses of diuretics are required to overcome the decreased natriuresis and reduced RBF induced by TGF. Ultimately, this action creates a vicious cycle of worsening renal function and diminished diuretic effectiveness.

The primary pharmacologic rationale for the use of KW-3902 in subjects with AHFS is its mechanism of action as an adenosine A1 receptor antagonist. TGF promotes release of adenosine, and adenosine binding to A1 receptors causes vasoconstriction of the afferent arteriole, decreased RBF, and enhanced sodium reabsorption by the proximal tubule. This action results in a decrease in GFR, diminished renal function, and sodium and water retention. Blocking adenosine A1 receptors via a selective adenosine receptor antagonist may limit sodium reabsorption by the proximal tubules without triggering TGF. It promotes vasodilation of the afferent arteriole of the glomerulus, and thus, this strategy offers the potential to overcome diuretic resistance or enhance diuretic responsiveness. It may also reduce the need for increasing diuretic doses that have been associated with worse outcomes.

The objectives of this study are to evaluate the effect of KW-3902IV in addition to intravenous (IV) loop diuretics (such as furosemide) on heart failure signs and symptoms, renal function, and safety in subjects hospitalized with AHFS, volume overload, and renal impairment, and to estimate and compare within-trial medical resource utilization and direct medical costs between patients treated with KW-3902IV versus placebo.