Development of novel bosentan analogues as endothelin receptor antagonists for pulmonary arterial hypertension

Since decades, bosentan has been in use for the treatment of pulmonary arterial hypertension (PAH). However, chronic exposure to bosentan leads to the development of resistance, tolerance, and serious adverse effects that have restricted its usage in clinical practices. To surmount these limitations, some new bosentan derivatives have been synthesized and evaluated for their therapeutic efficacy in PAH. Molecular docking analyses of all the synthesized derivatives were carried out using the endothelin (ET) receptor. In addition, the inhibitory ability of synthesized derivatives was determined in in vitro assay employing an ET-1 human ELISA kit. Among the synthesized derivatives, three derivatives namely 17d, 16j, and 16h with higher docking scores and lower IC50 values were selected for determination of the magnitude of the binding force between the derivative and ET receptor using molecular dynamics (MD) simulations study. Further, these derivatives were subjected to in vivo studies using monocrotaline (MCT) induced PAH in rat model. Results of in vivo studies inferred that the derivatives exhibit impressive ability to reduce PAH. Besides, its protective role was also evidenced in hemodynamic and right ventricular hypertrophy analyses, histological analysis, cardiac biomarkers, hypoxia-inducible factor 1 alpha (HIF1α) levels, and biochemical studies. Furthermore, gene quantification by quantitative RT-PCR and Western blot analysis was also performed to examine its effect on the expression of key proteins in PAH.

Notably, amongst three, derivative 16h exhibited the most encouraging results in molecular docking analysis, in vitro, in vivo, histopathological, biochemical, protein expression, and MD studies. Besides, derivative 16h also showed impressive pharmacokinetic features in ADMET analysis.

In conclusion, derivative 16 h could act as a reliable ET receptor antagonist and requires further exploration to attain its therapeutic utility in PAH management.