This potent, selective and orally available endothelin A receptor blocker (FW = 479.51 g/mol; CAS 290815-26-8; Soluble in DMSO), also known by its code names SPP301 and Ro 67-0565, induces the dose-dependent reduction in the fractional renal excretion of sodium (up to 8.7% at 50 mg avosentan), with a paralleled dose-related increase in proximal sodium reabsorption. Avosentan reduces albuminuria, when added to standard treatment in patients with type 2 diabetes and overt nephropathy, but induces significant fluid overload and congestive heart failure.