Darusentan is a potent inhibitor of endothelin signaling and function in both large and small arteriesThis article is one of a selection of papers published in the two-part special issue entitled 20 Years of Endothelin Research.

Abstract

Endothelin is a potent vasoconstrictor often up-regulated in hypertension. Endothelin vasoconstriction is mediated via the G-protein coupled endothelin A (ETA) receptor present on vascular smooth muscle. Endothelin receptor antagonists (ERAs) have been shown to antagonize ET-induced vasoconstriction. We describe the primary pharmacology of darusentan, a propanoic acid based ERA currently in phase 3 clinical trials for resistant hypertension. Darusentan was tested in membrane-, cell-, and tissue-based assays to determine its biochemical and functional potency. Rat aortic vascular smooth muscle cells (RAVSMs) were characterized using flow cytometry. RAVSM membrane fractions tested in saturation experiments exhibited moderate endothelin receptor density. Receptor counting revealed that >95% of the endothelin receptors in these fractions were the ETA subtype. (S)-Darusentan competed for radiolabeled endothelin binding in RAVSM membranes with single-site kinetics, exhibiting a Ki = 13 nmol/L. (R)-Darusentan exhibited no binding activity. In cultured RAVSMs, endothelin induced increases in inositol phosphate and Ca2+ signaling, both of which were attenuated by (S)-darusentan in a concentration-dependent manner. In isolated endothelium-denuded rat aortic rings, (S)-darusentan inhibited endothelin-induced vascular contractility with a pA2 = 8.1 +/- 0.14 (n = 4 animals; mean +/- SD). (R)-Darusentan had no effect. The vasorelaxant potency of (S)-darusentan did not change when determined in isolated denuded rat mesenteric arterioles, suggesting a similar mode of action in both conductance and resistance arteries. In vascular smooth muscle, (S)-darusentan is an ERA with high affinity for the ET receptor, which in this preparation is predominantly ETA receptors. (S)-Darusentan inhibits endothelin-induced signaling related to pro-contractile activity and is a potent inhibitor of vasoconstriction in large and small arteries.

Determination of darusentan enantiomers in rat plasma by enantioselective liquid chromatography with tandem mass spectrometry using cellulose‐based chiral stationary phase

“…Darusentan ((+)‐(S)‐2‐(4,6‐dimethoxypyrimidin‐2‐yl)oxy‐3‐methoxy‐3,3‐diphenylpropanoic acid) (Fig. 1), an orally active potent propanoic acid class endothelin receptor antagonist (ERA), selectively blocks endothelin‐1 (ET‐1) at the endothelin‐A (ETA) receptor, which inhibits endothelin‐induced signaling related to pro‐contractile activity and is a potent inhibitor of vasoconstriction in large and small arteries 1–4. Darusentan has been studied for the treatment of cardiovascular and renal disease such as hypertension 5–7, congestive heart failure 8, 9, pulmonary hypertension 8, 10 and glomerulosclerosis 11, 12.…”

“…Darusentan has been studied for the treatment of cardiovascular and renal disease such as hypertension 5–7, congestive heart failure 8, 9, pulmonary hypertension 8, 10 and glomerulosclerosis 11, 12. However, the R‐enantiomer had no effect on endothelin‐induced vascular contractility 2. Additionally, due to the different pharmacological and toxicological activities, it is necessary to study the individual enantiomers of chiral drugs in detail.…”