Tryptamine-based human beta3-adrenergic receptor agonists. Part 2: SAR of the methylene derivatives

Discovery of Novel Indazole Derivatives as Orally Available β3-Adrenergic Receptor Agonists Lacking Off-Target-Based Cardiovascular Side Effects

We previously discovered that indazole derivative 8 was a highly selective β₃-adrenergic receptor (β₃-AR) agonist, but it appeared to be metabolically unstable. To improve metabolic stability, further optimization of this scaffold was carried out. We focused on the sulfonamide moiety of this scaffold, which resulted in the discovery of compound 15 as a highly potent β₃-AR agonist (EC₅₀ = 18 nM) being inactive to β₁-, β₂-, and α_1A-AR (β₁/β₃, β₂/β₃, and α_1A/β₃ > 556-fold). Compound 15 showed dose-dependent β₃-AR-mediated responses in marmoset urinary bladder smooth muscle, had a desirable metabolic stability and pharmacokinetic profile (C_max and AUC), and did not obviously affect heart rate or mean blood pressure when administered intravenously (3 mg/kg) to anesthetized rats. Thus, compound 15 is a highly potent, selective, and orally available β₃-AR agonist, which may serve as a candidate drug for the treatment of overactive bladder without off-target-based cardiovascular side effects.

2D-QSAR and 3D-QSAR/CoMSIA Studies on a Series of (R)-2-((2-(1H-Indol-2-yl)ethyl)amino)-1-Phenylethan-1-ol with Human β₃-Adrenergic Activity

The β₃ adrenergic receptor is raising as an important drug target for the treatment of pathologies such as diabetes, obesity, depression, and cardiac diseases among others. Several attempts to obtain selective and high affinity ligands have been made. Currently, Mirabegron is the only available drug on the market that targets this receptor approved for the treatment of overactive bladder. However, the FDA (Food and Drug Administration) in USA and the MHRA (Medicines and Healthcare products Regulatory Agency) in UK have made reports of potentially life-threatening side effects associated with the administration of Mirabegron, casting doubts on the continuity of this compound. Therefore, it is of utmost importance to gather information for the rational design and synthesis of new β₃ adrenergic ligands. Herein, we present the first combined 2D-QSAR (two-dimensional Quantitative Structure-Activity Relationship) and 3D-QSAR/CoMSIA (three-dimensional Quantitative Structure-Activity Relationship/Comparative Molecular Similarity Index Analysis) study on a series of potent β₃ adrenergic agonists of indole-alkylamine structure. We found a series of changes that can be made in the steric, hydrogen-bond donor and acceptor, lipophilicity and molar refractivity properties of the compounds to generate new promising molecules. Finally, based on our analysis, a summary and a regiospecific description of the requirements for improving β₃ adrenergic activity is given.

Comparative 3D QSAR study on β(1)-, β(2)-, and β(3)-adrenoceptor agonists

A quantitative structure–activity relationship study of tryptamine-based derivatives of β₁-, β₂-, and β₃-adrenoceptor agonists was conducted using comparative molecular field analysis (CoMFA). Correlation coefficients (cross-validated r²) of 0.578, 0.595, and 0.558 were obtained for the three subtypes, respectively, in three different CoMFA models. All three CoMFA models have different steric and electrostatic contributions, implying different requirements inside the binding cavity. The CoMFA coefficient contour plots of the three models and comparisons among these plots provide clues regarding the main chemical features responsible for the biological activity variations and also result in predictions which correlate very well with the observed biological activity. Based on the analysis, a summary regeospecific description of the requirements for improving β-adrenoceptor subtype selectivity is given.

Tryptamine-based human β3-adrenergic receptor agonists. Part 3: Improved oral bioavailability via modification of the sulfonamide moiety

The continued SAR investigation of tryptamine-based human beta(3)-adrenergic receptor (AR) agonists is reported. Prior efforts resulted in the identification of 2 as a potent beta(3)-AR agonist. Further modification of the left side arylsulfonamide portion in 2 provided compounds with good cell permeability, which have potent agonistic activity for beta(3)-AR. Cinnamylamine analog 16i exhibited an excellent agonistic profile in vitro and good oral bioavailability in rats.