Novel and potent human and rat beta3-adrenergic receptor agonists containing substituted 3-indolylalkylamines

Pharmacophore-guided Virtual Screening to Identify New β3-Adrenergic Receptor Agonists

The β₃‐adrenergic receptor (β₃‐AR) is found in several tissues such as adipose tissue and urinary bladder. It is a therapeutic target because it plays a role in thermogenesis, lipolysis, and bladder relaxation. Two β₃‐AR agonists are used clinically: mirabegron 1 and vibegron 2, which are indicated for overactive bladder syndrome. However, these drugs show adverse effects, including increased blood pressure in mirabegron patients. Hence, new β₃‐AR agonists are needed as starting points for drug development. Previous pharmacophore modeling studies of the β₃‐AR did not involve experimental in vitro validation. Therefore, this study aimed to conduct prospective virtual screening and confirm the biological activity of virtual hits. Ligand‐based pharmacophore modeling was performed since no 3D structure of human β₃‐AR is yet available. A dataset consisting of β₃‐AR agonists was prepared to build and validate the pharmacophore models. The best model was employed for prospective virtual screening, followed by physicochemical property filtering and a docking evaluation. To confirm the activity of the virtual hits, an in vitro assay was conducted, measuring cAMP levels at the cloned β₃‐AR. Out of 35 tested compounds, 4 compounds were active in CHO−K1 cells expressing the human β₃‐AR, and 8 compounds were active in CHO−K1 cells expressing the mouse β₃‐AR.

Enantioselective Chromatographic Separation and Lipase Catalyzed Asymmetric Resolution of Biologically Important Chiral Amines

Cyanoacetamides are vital synthons in synthetic organic chemistry. However, methods to enantiopure cyanoacetamides have not yet been well explored. In this work, the preparation of cyanoacetamide synthons RS-(1a–4a) or methoxyacetamides RS-(1b–4b) in enantiopure/enriched form was investigated. Compounds S-1, S-2, R-1b, R-1a, andR-2b were prepared in enantiopure form (ee > 99%) while compounds S-4, R-2a, and R-4a were achieved in ee 9%, 80%, and 76%, respectively. Many baselines enantioselective HPLC separations of amines 1–4, their cyanoacetamides (1a–4a), and methoxyacetamides (1b–4b) were achieved by utilizing diverse mobile-phase compositions and two cellulose-based CSPs (ODH® and LUX-3® columns). Such enantioselective HPLC separations were used to monitor the lipase-catalyzed kinetic resolution of amines RS-(1–4).

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.

Structural characterization and computer-aided optimization of a small-molecule inhibitor of the Arp2/3 complex, a key regulator of the actin cytoskeleton

CK-666 (1) is a recently discovered small-molecule inhibitor of the actin-related protein 2/3 (Arp2/3) complex, a key actin cytoskeleton regulator with roles in bacterial pathogenesis and cancer cell motility. Although 1 is commercially available, the crystal structure of Arp2/3 complex with 1 bound has not been reported, making its mechanism of action uncertain. Furthermore, its relatively low potency increases its potential for off-target effects in vivo, complicating interpretation of its influence in cell biological studies and precluding its clinical use. Herein we report the crystal structure of 1 bound to Arp2/3 complex, which reveals that 1 binds between the Arp2 and Arp3 subunits to stabilize the inactive conformation of the complex. Based on the crystal structure, we used computational docking and free-energy perturbation calculations of monosubstituted derivatives of 1 to guide optimization efforts. Biochemical assays of ten newly synthesized compounds led to the identification of compound 2, which exhibits a threefold increase in inhibitory activity in vitro relative to 1. In addition, our computational analyses unveiled a surface groove at the interface of the Arp2 and Arp3 subunits that can be exploited for additional structure-based optimization.

β(3)-Adrenoceptor agonists and (antagonists as) inverse agonists history, perspective, constitutive activity, and stereospecific binding

β(3)-Adrenergic receptor (β(3)-AR) is expressed in several tissues and is considered a drug target for the treatment of several pathologies such as obesity, type 2 diabetes, cachexia, metabolic syndrome, heart failure, anxiety and depressive disorders, preterm labor, overactive bladder, control colon motility, and of coadjuvants in colon cancer therapy. It is a seven-transmembrane domain (7TD) G-protein coupled receptor and is usually coupled to a Gs-protein (Gi-protein in very few cases), and its stimulation increases the production of cAMP. A lot of β(3)-AR agonists have been uncovered and extensively characterized. Conversely, very little is known about β(3)-AR inverse agonists that would suppress the agonist-independent activity (constitutive activity) of the receptor by stabilizing it in its inactive state. This chapter attempts to outline (a) the importance of the β(3)-AR as a therapeutic target through the disquisition of its role in human health (physiology) and disease (pathology); (b) the description of β(3)-AR structure [amino acid sequence and 7TD organization]; (c) the medicinal chemistry of β(3)-AR: 7TD amino acid-ligand specific interactions, β-adrenoreceptor subtype selectivity, stereospecific interactions and biological activity relationships, inverse agonism and blockage of β(3)-adrenoceptor constitutive activity; and (d) β(3)-AR inverse agonists. The detailed procedure to prepare and assess the biological activity/selectivity of the more potent and selective β(3)-AR inverse agonists (SP-1e and SP-1g) up to now known is also described.

Spirotetrahydro beta-carbolines (spiroindolones): a new class of potent and orally efficacious compounds for the treatment of malaria

The antiplasmodial activity of a series of spirotetrahydro β-carbolines is described. Racemic spiroazepineindole (1) was identified from a phenotypic screen on wild type Plasmodium falciparum with an in vitro IC₅₀ of 90 nM. Structure−activity relationships for the optimization of 1 to compound 20a (IC₅₀ = 0.2 nM) including the identification of the active 1R,3S enantiomer and elimination of metabolic liabilities is presented. Improvement of the pharmacokinetic profile of the series translated to exceptional oral efficacy in the P. berghei infected malaria mouse model where full cure was achieved in four of five mice with three daily doses of 30 mg/kg.

The tertiary amine nitrogen atom of piperazine sulfonamides as a novel determinant of potent and selective beta3-adrenoceptor agonists

Novel compounds were prepared in fair to good yields as human beta(3)-adrenoceptor (beta(3)-AR) agonists. In particular, aryloxypropanolamines 7 a-d (EC(50)=0.57-2.1 nM) and arylethanolamines 12 a,b,e (EC(50)=6.38-19.4 nM) were designed to explore the effects of modifications at the right-hand side of these molecules on their activity as beta(3)-AR agonists. Piperidine sulfonamides 15 a-c, e-g (EC(50)=6.1-36.2 nM) and piperazine sulfonamide derivatives 20-29 (EC(50)=1.79-49.3 nM) were examined as compounds bearing a non-aromatic linker on the right- and left-hand sides of the molecules. Some piperazine sulfonamides were found to be potent and selective beta(3)-AR agonists, even if the amine nitrogen atom is tertiary and not secondary, as is the case for all beta(3)-AR agonists reported so far. (S)-3-{4-{N-{4-{2-[2-Hydroxy-3-(4-hydroxyphenoxy)propylamino]ethyl}phenyl}sulfamoyl}phenoxy}propanoic acid (7 d; EC(50)=0.57 nM), (R)-N-{4-[2-(2-hydroxy-2-phenylethylamino)ethyl]phenyl}-4-(3-octylureido)benzenesulfonamide (12 e; EC(50)=6.38 nM), (R)-2-[1-(4-methoxyphenylsulfonyl)piperidin-4-ylamino]-1-phenylethanol (15 f; EC(50)=6.1 nM), and (S)-4-{2-hydroxy-3-[4-(4-methoxyphenylsulfonyl)piperazin-1-yl]propoxy}phenol (25; EC(50)=1.79 nM) were found to be the most potent beta(3)-AR agonists of the aryloxypropanolamine, arylethanolamine, piperidine sulfonamide, and piperazine sulfonamide classes, respectively. The two most potent compounds were identified as possible candidates for further development of beta(3)-AR agonists useful in the treatment of beta(3)-AR-mediated pathological conditions.

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.

Stereospecific synthesis and bio-activity of novel beta(3)-adrenoceptor agonists and inverse agonists

Since it is widely distributed into the body, beta(3)-adrenoceptor is becoming an attractive target for the treatment of several pathologies such as obesity, type 2 diabetes, metabolic syndrome, cachexia, overactive bladder, ulcero-inflammatory disorder of the gut, preterm labour, anxiety and depressive disorders, and heart failure. New compounds belonging to the class of arylethanolamines bearing one or two stereogenic centres were prepared in good yields as racemates and optically active forms. They were, then, evaluated for their intrinsic activity towards beta(3)-adrenoceptor and their affinity for beta(1)- and beta(2)-adrenergic receptors. Stereochemical features were found to play a crucial role in determining the behaviour of such compounds. In particular, alpha-racemic, (alphaR)- and (alphaS)-2-{4-[2-(2-hydroxy-2-phenylethylamino)ethyl]phenoxy}-2- methylpropanoic acid, (alpha-rac, beta-rac)-, (alphaR, betaS)- and (alphaR, betaR)- 2-{4-[2-(2-hydroxy-2-phenylethylamino)ethyl]phenoxy}propanoic acid were found to be endowed with beta(3)-adrenoceptor agonistic activity. Whereas, (alphaS, betaS)- and (alphaS, betaR)-2-{4-[2-(2-hydroxy-2-phenylethylamino)ethyl]phenoxy}propanoic acid behaved as beta(3)-adrenoceptor inverse agonists. Such compounds showed no affinity for beta(1)- and beta(2)-adrenergic receptor, respectively. Thus, resulting highly selective beta(3)-adrenoceptor ligands.

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

A series of tryptamine derivatives with modified sulfonamide were designed, synthesized, and evaluated for their ability to stimulate cAMP accumulation in CHO cells expressing the cloned human beta3-adrenergic receptor (AR). For this series of compounds, our objective was to symmetrize the alpha-position of the tryptamine moiety maintaining its activity and reducing the cost of production. Compound 11h, having m-aminobenzene, exhibited excellent agonistic activity for beta3-AR with excellent subtype selectivity.

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.

Discovery of 1,7-cyclized indoles as a new class of potent and highly selective human β3-adrenergic receptor agonists with high cell permeability

The synthesis and evaluation of a novel series of 1,7-cyclized indole-based human adrenergic receptor (beta3-AR) agonists are reported. The synthesis of a variety of 1,7-cyclized indole part was accomplished by the Mitsunobu reaction or a ring closing metathesis (RCM) reaction. SAR studies revealed that expansion of the ring size resulted in considerable selectivity against the beta1- and beta2-ARs. Compound 26, an eight-membered ring analogue with a double bond on its 1,7-linker portion, was found to be a potent beta3-AR agonist (EC50 = 0.75 nM, IA = 90%) with extremely high selectivity for the beta3-AR over the beta1- and beta2-ARs.

Discovery of a novel, potent and selective human β3-adrenergic receptor agonist

The discovery of a novel, potent and selective beta(3)-adrenergic receptor (AR) agonist is described. SAR studies demonstrated the structural requirements for activity and selectivity. Compound 1c, which showed good beta(3)-AR activity and selectivity, was identified and pharmacokinetics were investigated.

Tryptamine-based human β3-adrenergic receptor agonists. Part 1: SAR studies of the 7-position of the indole ring

A series of tryptamine-based 2-thiophenesulfonamide derivatives were prepared and their agonistic activity for the beta-adrenergic receptors (ARs) was evaluated. Compound 54, containing 7-methanesulfonyloxy tryptamine, was found to be a highly potent beta3-AR agonist (EC50=0.21 nM, IA=97%) with excellent selectivity for the beta3-AR over the beta1- and beta2-ARs (210- and 86-fold, respectively).