bosentan

Bosentan (Benzenesulfonamide) is a sulfonamide-derived, competitive and specific endothelin receptor antagonist with a slightly higher affinity for the endothelin A receptor than endothelin B receptor. Bosentan blocks the action of endothelin 1, an extremely potent endogenous vasoconstrictor and bronchoconstrictor, by binding to endothelin A and endothelin B receptors in the endothelium and vascular smooth muscle. Bosentan decreases both pulmonary and systemic vascular resistance and is particularly used in the treatment of pulmonary arterial hypertension.

Bosentan hydrate (Ro 47-0203) is a competitive and dual antagonist of endothelin-1 at the endothelin-A (ET-A) and endothelin-B (ET-B) receptors.

Hydroxy bosentan (Ro 48-5033) is a primary metabolite of Bosentan (BOS) metabolized by the cytochrome P450 system in the liver, assisting BOS pharmacologically with 10%-20% activity retention.

Hydroxy desmethyl Bosentan (Ro 64-105) is a metabolite of Bosentan formed by the liver cytochrome P450 enzymes CYP2C9 and CYP3A4.

Desmethyl bosentan, an active metabolite of the endothelin receptor antagonist bosentan, activates the pregnane X receptor (PXR) in CV-1 monkey kidney cells expressing the human receptor in a reporter assay at a concentration of 25 μM.

Bosentan-d4, the deuterium-labeled variant of Bosentan, serves as a competitive dual antagonist against endothelin-1 (ET) by targeting both ET A and ET B receptors. It exhibits binding affinities with K i values of 4.7 nM for ET A and 95 nM for ET B in human SMC.

Nebentan (YM598) is a potent, selective and orally active non-peptide endothelin ETA receptor antagonist through the modification of Bosentan . Nebentan inhibits [125I] endothelin-1 binding to cloned human endothelin ETA and ETB receptor, with Ki of 0.697 nM and 569 nM, respectively[1]. YM598 can ameliorate the progression of cor pulmonale and myocardial infarction in vivo[2]. Nebentan inhibits the specific binding of [125I] endothelin-1 to endothelin ETA and ETB receptors in a concentration dependent manner,Ki values are 0.697 nM and 1.53 nM for human and rat endothelin ETA receptors, respectively. In contrast, YM598 exhibits low affinities for human and rat endothelin ETB receptors, with Ki values of 569 nM and 155 nM,respectively[1].In measurement of intracellular Ca2+ concentration, Nebentan concentration-dependently inhibits the increase in [Ca2+]i induced by 10 nM endothelin-1 in both CHO cells and A10 cells, the IC50 values are 26.2 nM for CHO cells and 26.7 nM for A10 cells, respectively[1]. Nebentan (oral administration; 0.1-1 mg kg; 4 weeks) significantly inhibits the progression of pulmonary hypertension and the development of right ventricular hypertrophy[2].Nebentan (oral administration; 1 mg kg; 30 weeks) significantly ameliorates the poor survival rate of CHF rats, it markedly reduces the hypertrophy of both ventricles as well as pulmonary congestion[2]. [1]. Hironori Yuyama, et al. Pharmacological Characterization of YM598, an Orally Active and Highly Potent Selective Endothelin ET(A) Receptor Antagonist. Eur J Pharmacol. 2003 Sep 30;478(1):61-71. [2]. Akira Fujimori, et al. YM598, an Orally Active ET(A) Receptor Antagonist, Ameliorates the Progression of Cardiopulmonary Changes and Both-Side Heart Failure in Rats With Cor Pulmonale and Myocardial Infarction. J Cardiovasc Pharmacol. 2004 Nov;44 Suppl 1:S354-7.