| Biological Description |
Bosentan hydrate is a competitive and dual antagonist of endothelin-1 (ET) for the ETA and ETB receptors with Ki of 4.7 nM and 95 nM in human SMC, respectively.
IC50 & Target: Ki: 4.7 nM (ETA receptor, in human SMC), 95 nM (ETA receptor, in human SMC)[1]
In Vitro: Bosentan (BOS) competitively and specifically antagonizes binding of 125I-labelled ET-1 to ETA receptors on human smooth muscle cells (SMC) and ETB receptors on human placenta cells. The in vitro binding affinity of Bosentan to ETA receptors on human SMC is 4.7 nM and to ETB receptors on human SMC or placenta cells is 41 or 95 nM. Bosentan has 67-fold greater selectivity for ETA than ETB receptors (mean IC50=7.1 vs 474.8 nM) in an in vitro 125I-labeling assay[1].
In Vivo: Single-dose Bosentan 62.5 mg significantly (p<0.01 vs baseline) plasma ET-1 levels by 2-fold in 7 pts with WHO class II or III idiopathic or CTD-associated PAH, with peak levels achieved at 8 h[1]. In hypertensive rats, Macitentan 30 mg/kg further decreases mean arterial blood pressure (MAP) by 19 mm Hg when given on top of Bosentan 100 mg/kg. Conversely, Bosentan given on top of Macitentan fails to induce an additional MAP decrease. In pulmonary hypertensive rats, Macitentan 30 mg/kg further decreases mean pulmonary artery pressure (MPAP) by 4 mm Hg on top of Bosentan, whereas a maximal effective dose of Bosentan given on top of Macitentan does not cause any additional MPAP decrease[3]. |
