Discovery of ß-arrestin-biased ß2-adrenoceptor agonists from 2-amino-2-phenylethanol derivatives.

ß-Arrestins are a small family of proteins important for signal transduction at G protein-coupled receptors (GPCRs). ß-Arrestins are involved in the desensitization of GPCRs. Recently, biased ligands possessing different efficacies in activating the G protein- versus the ß-arrestin-dependent signals downstream of a single GPCR have emerged, which can be used to selectively modulate GPCR signal transduction in such a way that desirable signals are enhanced to produce therapeutic effects while undesirable signals of the same GPCR are suppressed to avoid side effects. In the present study, we evaluated agonist bias for compounds developed along a drug discovery project of ß2-adrenoceptor agonists. About 150 compounds, including derivatives of fenoterol, 2-amino-1-phenylethanol and 2-amino-2-phenylethanol, were obtained or synthesized, and initially screened for their ß-adrenoceptor-mediated activities in the guinea pig tracheal smooth muscle relaxation assay or the cardiomyocyte contractility assay. Nineteen bioactive compounds were further assessed using both the HTRF cAMP assay and the PathHunter ß-arrestin assay. Their concentration-response data in stimulating cAMP synthesis and ß-arrestin recruitment were applied to the Black-Leff operational model for ligand bias quantitation. As a result, three compounds (L-2, L-4, and L-12) with the core structure of 5-(1-amino-2-hydroxyethyl)-8-hydroxyquinolin-2(1H)-one were identified as a new series of ß-arrestin-biased ß2-adrenoceptor agonists, whereas salmeterol was found to be Gs-biased. These findings would facilitate the development of novel drugs for the treatment of both heart failure and asthma.

Synthesis and biological evaluation of ß2-adrenoceptor agonists bearing the 2-amino-2-phenylethanol scaffold.

A new series of ß2-adrenoceptor agonists bearing the 2-amino-2-phenylethanol scaffold was synthesized. Evaluation of the compounds using cell assays and an in vitro guinea pig trachea relaxation assay showed that 8-hydroxy-5-(2-hydroxy-1-((4-hydroxyphenethyl)amino)ethyl)quinolin-2(1H)-one (compound 5j) has the best pharmacological profile among all the evaluated compounds. The (S)-isomer of 5j was subsequently found to be the active enantiomer with a promising EC50 value of 1.26 nM in stimulating ß2-adrenoceptor-mediated cAMP accumulation and a substantially higher selectivity for the ß2 than for the ß1 subtype. The putative binding mode of (S)-5j revealed by molecular docking of the ß2-adrenoceptor resembles that in agonist binding. Taken together, these results showed that compound (S)-5j is a promising compound worthy of further study for the development of ß2-adrenoceptor agonists.

Synthesis, biological evaluation and molecular modeling of 2-amino-2-phenylethanol derivatives as novel ß2-adrenoceptor agonists.

A novel series of 2-amino-2-phenylethanol derivatives were developed as ß2-adrenoceptor agonists. Among them, 2-amino-3-fluoro-5-(2-hydroxy-1-(isopropylamino)ethyl)benzonitrile (compound 2f) exhibited the highest activity (EC50 = 0.25 nM) in stimulating ß2-adrenoceptor-mediated cellular cAMP production with a 763.6-fold selectivity over the ß1-adrenoceptor. The (S)-isomer of 2f was subsequently found to be 8.5-fold more active than the (R)-isomer. Molecular docking was performed to determine the putative binding modes of this new class of ß2-adrenoceptor agonists. Taken together, these data show that compound 2f is a promising lead compound worthy of further study for the development of ß2-adrenoceptor agonists.

[Recent advances in study of long ß(2)-adrenoceptor agonist].

ß2-Adrenoceptor agonists are highly effective bronchodilators and are widely used in the treatment of both chronic obstructive pulmonary disease (COPD) and asthma. In the last 15 years, there has been great interest within the pharmaceutical industry in the discovery of a long ß2-adrenoceptor agonist for a mono-therapy or combination therapy. The search for new long-acting ß2-adrenoreceptor agonists (LABA's), for the treatment of asthma and COPD, has become a very active area of drug discovery. This article reviews the mechanisms, potential candidates and research advances of long ß2-adrenoceptor agonists.