Identification of benzothiazole derived monosaccharides as potent, selective, and orally bioavailable inhibitors of human and mouse galectin-3; a rare example of using a S···O binding interaction for drug design.

As a result of our continued efforts to pursue Gal-3 inhibitors that could be used to fully evaluate the potential of Gal-3 as a therapeutic target, two novel series of benzothiazole derived monosaccharides as potent (against both human and mouse Gal-3) and orally bioavailable Gal-3 inhibitors, represented by 4 and 5, respectively, were identified. These discoveries were made based on proposals that the benzothiazole sulfur atom could interact with the carbonyl oxygen of G182/G196 in h/mGal-3, and that the anomeric triazole moiety could be modified into an N-methyl carboxamide functionality. The interaction between the benzothiazole sulfur and the carbonyl oxygen of G196 in mGal-3 was confirmed by an X-ray co-crystal structure of early lead 9, providing a rare example of using a S···O binding interaction for drug design. It was found that for both the series, methylation of 3-OH in the monosaccharides caused no loss in h & mGal-3 potencies but significantly improved permeability of the molecules.

Synthesis of Bicyclo[1.1.0]butanes from Iodo-Bicyclo[1.1.1]pentanes.

We describe a two-step process for the synthesis of substituted bicyclo[1.1.0]butanes. A photo-Hunsdiecker reaction generates iodo-bicyclo[1.1.1]pentanes under metal-free conditions at room temperature. These intermediates react with nitrogen and sulfur nucleophiles to afford substituted bicyclo[1.1.0]butane products.

Optimization of physicochemical properties of pyrrolidine GPR40 AgoPAMs results in a differentiated profile with improved pharmacokinetics and reduced off-target activities.

GPR40 AgoPAMs are highly effective antidiabetic agents that have a dual mechanism of action, stimulating both glucose-dependent insulin and GLP-1 secretion. The early lipophilic, aromatic pyrrolidine and dihydropyrazole GPR40 AgoPAMs from our laboratory were highly efficacious in lowering plasma glucose levels in rodents but possessed off-target activities and triggered rebound hyperglycemia in rats at high doses. A focus on increasing molecular complexity through saturation and chirality in combination with reducing polarity for the pyrrolidine AgoPAM chemotype resulted in the discovery of compound 46, which shows significantly reduced off-target activities as well as improved aqueous solubility, rapid absorption, and linear PK. In vivo, compound 46 significantly lowers plasma glucose levels in rats during an oral glucose challenge yet does not demonstrate the reactive hyperglycemia effect at high doses that was observed with earlier GPR40 AgoPAMs.

Amination of Nitro-Substituted Heteroarenes by Nucleophilic Substitution of Hydrogen.

An open-air method for the transition metal-free direct amination of nitro(hetero)arenes by anilines is disclosed. In this methodology, an aromatic C-H bond is substituted via oxidative nucleophilic aromatic substitution of hydrogen (ONSH). Density functional theory calculations and mechanistic studies support a dianion pathway with oxidation by molecular oxygen as the rate-limiting step.

Identification of Monosaccharide Derivatives as Potent, Selective, and Orally Bioavailable Inhibitors of Human and Mouse Galectin-3.

Galectin-3 (Gal-3), a member of the ß-galactoside-binding protein family, is implicated in a wide variety of human diseases. Identification of Gal-3 inhibitors with the right combination of potency (against both human and mouse Gal-3) and pharmacokinetic properties to fully evaluate the potential of Gal-3 for therapeutic intervention has been a major challenge due to the characteristics of its binding pocket: high hydrophilicity and key structural differences between human Gal-3 and the mouse ortholog. We report the discovery of a novel series of monosaccharide-based, highly potent, and orally bioavailable inhibitors of human and mouse Gal-3. The novel monosaccharide derivatives proved to be selective for Gal-3, the only member of the chimeric type of galectins, over Gal-1 and Gal-9, representative of the prototype and tandem-repeat type of galectins, respectively. The proposed binding mode for the newly identified ligands was confirmed by an X-ray cocrystal structure of a representative analogue bound to Gal-3 protein.

Discovery of BMS-986339, a Pharmacologically Differentiated Farnesoid X Receptor Agonist for the Treatment of Nonalcoholic Steatohepatitis.

While several farnesoid X receptor (FXR) agonists under clinical investigation for the treatment of nonalcoholic steatohepatitis (NASH) have shown beneficial effects, adverse effects such as pruritus and elevation of plasma lipids have limited their clinical efficacy and approvability. Herein, we report the discovery and preclinical evaluation of compound 32 (BMS-986339), a nonbile acid FXR agonist with a pharmacologically distinct profile relative to our previously reported agonist BMS-986318. Compound 32 exhibited potent in vitro and in vivo activation of FXR, albeit with a context-dependent profile that resulted in tissue-selective effects in vivo. To our knowledge, this is the first report that demonstrates differential induction of Fgf15 in the liver and ileum by FXR agonists in vivo. Compound 32 demonstrated robust antifibrotic efficacy despite reduced activation of certain genes in the liver, suggesting that the additional pharmacology of BMS-986318 does not further benefit efficacy, possibly presenting an opportunity for reduced adverse effects. Further evaluation in humans is warranted to validate this hypothesis.

Structural and Thermal Characterization of Halogenated Azidopyridines: Under-Reported Synthons for Medicinal Chemistry.

Owing to their participation in Click reactions, bifunctional azides are valuable intermediates in the preparation of medicines and biochemical tool compounds. Despite the privileged nature of pyridines among pharmaceutical scaffolds, reports of the synthesis and characterization of azidopyridines bearing a halogen substituent for further elaboration are almost completely unknown in the literature. As azidopyridines carry nearly equal numbers of nitrogen and carbon atoms, we hypothesized that safety concerns limited the application of these useful bifunctional building blocks in medicinal and biological chemistry. To address this concern, we prepared and characterized nine azidopyridines bearing a single fluorine, chlorine, or bromine atom. All were examined by differential scanning calorimetry (DSC), in which they demonstrated exotherms of 228-326 kJ/mol and onset temperatures between 119 and 135 °C. Selected azidopyridines were advanced to mechanical stress testing, in which impact sensitivity was noted for one regioisomer of C5H3FN4. The utility of these versatile intermediates was demonstrated through their use in a variety of Click reactions and the diversification of the halogen handles.

Discovery of an Oxycyclohexyl Acid Lysophosphatidic Acid Receptor 1 (LPA1) Antagonist BMS-986278 for the Treatment of Pulmonary Fibrotic Diseases.

The oxycyclohexyl acid BMS-986278 (33) is a potent lysophosphatidic acid receptor 1 (LPA1) antagonist, with a human LPA1 Kb of 6.9 nM. The structure-activity relationship (SAR) studies starting from the LPA1 antagonist clinical compound BMS-986020 (1), which culminated in the discovery of 33, are discussed. The detailed in vitro and in vivo preclinical pharmacology profiles of 33, as well as its pharmacokinetics/metabolism profile, are described. On the basis of its in vivo efficacy in rodent chronic lung fibrosis models and excellent overall ADME (absorption, distribution, metabolism, excretion) properties in multiple preclinical species, 33 was advanced into clinical trials, including an ongoing Phase 2 clinical trial in patients with lung fibrosis (NCT04308681).

Synthesis, Structure-Activity Relationships, and In Vivo Evaluation of Novel Tetrahydropyran-Based Thiodisaccharide Mimics as Galectin-3 Inhibitors.

Galectin-3 is a member of a family of ß-galactoside-binding proteins. A substantial body of literature reports that galectin-3 plays important roles in cancer, inflammation, and fibrosis. Small-molecule galectin-3 inhibitors, which are generally lactose or galactose-based derivatives, have the potential to be valuable disease-modifying agents. In our efforts to identify novel galectin-3 disaccharide mimics to improve drug-like properties, we found that one of the monosaccharide subunits can be replaced with a suitably functionalized tetrahydropyran ring. Optimization of the structure-activity relationships around the tetrahydropyran-based scaffold led to the discovery of potent galectin-3 inhibitors. Compounds 36, 40, and 45 were selected for further in vivo evaluation. The synthesis, structure-activity relationships, and in vivo evaluation of novel tetrahydropyran-based galectin-3 inhibitors are described.

Discovery of Pyrrolidine-Containing GPR40 Agonists: Stereochemistry Effects a Change in Binding Mode.

A novel series of pyrrolidine-containing GPR40 agonists is described as a potential treatment for type 2 diabetes. The initial pyrrolidine hit was modified by moving the position of the carboxylic acid, a key pharmacophore for GPR40. Addition of a 4-cis-CF3 to the pyrrolidine improves the human GPR40 binding Ki and agonist efficacy. After further optimization, the discovery of a minor enantiomeric impurity with agonist activity led to the finding that enantiomers (R,R)-68 and (S,S)-68 have differential effects on the radioligand used for the binding assay, with (R,R)-68 potentiating the radioligand and (S,S)-68 displacing the radioligand. Compound (R,R)-68 activates both Gq-coupled intracellular Ca2+ flux and Gs-coupled cAMP accumulation. This signaling bias results in a dual mechanism of action for compound (R,R)-68, demonstrating glucose-dependent insulin and GLP-1 secretion in vitro. In vivo, compound (R,R)-68 significantly lowers plasma glucose levels in mice during an oral glucose challenge, encouraging further development of the series.

Reductions in log P improved protein binding and clearance predictions enabling the prospective design of cannabinoid receptor (CB1) antagonists with desired pharmacokinetic properties.

Several strategies have been employed to reduce the long in vivo half-life of our lead CB1 antagonist, triazolopyridazinone 3, to differentiate the pharmacokinetic profile versus the lead clinical compounds. An in vitro and in vivo clearance data set revealed a lack of correlation; however, when compounds with <5% free fraction were excluded, a more predictable correlation was observed. Compounds with log P between 3 and 4 were likely to have significant free fraction, so we designed compounds in this range to give more predictable clearance values. This strategy produced compounds with desirable in vivo half-lives, ultimately leading to the discovery of compound 46. The progression of compound 46 was halted due to the contemporaneous marketing and clinical withdrawal of other centrally acting CB1 antagonists; however, the design strategy successfully delivered a potent CB1 antagonist with the desired pharmacokinetic properties and a clean off-target profile.

Preparation of N-alkyl 2-pyridones via a lithium iodide promoted O- to N-alkyl migration: scope and mechanism.

An efficient and inexpensive LiI-promoted O- to N-alkyl migration of 2-benzyloxy-, 2-allyloxy-, and 2-propargyloxypyridines and heterocycles is reported. The reaction produces the corresponding N-alkyl 2-pyridones and analogues under green, solvent-free conditions in good to excellent yields (30 examples, 20-97% yield). This method has been shown to be intermolecular and requires heat and lithium cation to occur.

Cannabinoid CB(1) receptor ligand binding and function examined through mutagenesis studies of F200 and S383.

The cannabinoid CB(1) G protein-coupled receptor has been shown to be a regulator of food consumption and has been studied extensively as a drug target for the treatment of obesity. To advance understanding of the receptor's three-dimensional structure, we performed mutagenesis studies at human cannabinoid CB(1) receptor residues F200 and S383 and measured changes in activity and binding affinity of compounds from two recently discovered active chemotypes, arylsulfonamide agonists and tetrahydroquinoline-based inverse agonists, as well as literature compounds. Our results add support to previous findings that both agonists and inverse agonists show varied patterns of binding at the two mutated residue sites, suggesting multiple subsites for binding to the cannabinoid CB(1) receptor for both functional types of ligands. We additionally find that an F200L mutation in the receptor largely restores binding affinity to ligands and significantly decreases constitutive activity when compared to F200A, resulting in a receptor phenotype that is closer to the wild-type receptor. The results downplay the importance of aromatic stacking interactions at F200 and suggest that a bulky hydrophobic contact is largely sufficient to provide significant receptor function and binding affinity to cannabinoid CB(1) receptor ligands.

Aglycone exploration of C-arylglucoside inhibitors of renal sodium-dependent glucose transporter SGLT2.

Inhibition of sodium-dependent glucose transporter 2 (SGLT2), the transporter that is responsible for renal re-uptake of glucose, leads to glucosuria in animals. SGLT-mediated glucosuria provides a mechanism to shed excess plasma glucose to ameliorate diabetes-related hyperglycemia and associated complications. The current study demonstrates that the proper relationship of a 4'-substituted benzyl group to a beta-1C-phenylglucoside is important for potent and selective SGLT2 inhibition. The lead C-arylglucoside (7a) demonstrates superior metabolic stability to its O-arylglucoside counterpart (4) and it promotes glucosuria when administered in vivo.

Synthesis of substituted N-benzyl pyridones via an O- to N-alkyl migration.

A new LiI-promoted O- to N-alkyl migration has been developed for the conversion of O-alkylated 2-hydroxy pyridines, quinolines, and pyrimidines to the corresponding N-alkylated heterocycles in good to excellent yields (57-99%). This method serves as an efficient means for the preparation of N-benzyl pyridones, quinolones, and pyrimidones.

Discovery of dapagliflozin: a potent, selective renal sodium-dependent glucose cotransporter 2 (SGLT2) inhibitor for the treatment of type 2 diabetes.

The C-aryl glucoside 6 (dapagliflozin) was identified as a potent and selective hSGLT2 inhibitor which reduced blood glucose levels in a dose-dependent manner by as much as 55% in hyperglycemic streptozotocin (STZ) rats. These findings, combined with a favorable ADME profile, have prompted clinical evaluation of dapagliflozin for the treatment of type 2 diabetes.

Remarkable beta-selectivity in the synthesis of beta-1-C-arylglucosides: stereoselective reduction of acetyl-protected methyl 1-C-arylglucosides without acetoxy-group participation.

An efficient and practical process to generate beta-C-arylglucoside derivatives was achieved. The process described involves Lewis acid mediated ionic reduction of a peracetylated 1-C-aryl methyl glucoside derived from the addition of an aryl-Li to selectively protected delta-D-gluconolactone. The reduction of the 2-acetoxy-1-C-oxacarbenium ion intermediates proceeds with a high degree of selectivity to give beta-C-arylglucosides without 2-acetoxy group participation. Furthermore, during the reduction process we also identified an unprecedented critical role of water. By changing from the usual benzyl ether protecting groups because of cost and chemical compatibility concerns, the new process is made additionally efficient and highly selective.

Discovery of pyrazine carboxamide CB1 antagonists: the introduction of a hydroxyl group improves the pharmaceutical properties and in vivo efficacy of the series.

Structure-activity relationships for a series of pyrazine carboxamide CB1 antagonists are reported. Pharmaceutical properties of the series are improved via inclusion of hydroxyl-containing sidechains. This structural modification sufficiently improved ADME properties of an orally inactive series such that food intake reduction was achieved in rat feeding models. Compound 35 elicits a 46% reduction in food intake in ad libidum fed rats 4-h post-dose.