Discovery of triazolopyrimidine-based PDE8B inhibitors: exceptionally ligand-efficient and lipophilic ligand-efficient compounds for the treatment of diabetes.

PDE8B is a cAMP-specific isoform of the broader class of phosphodiesterases (PDEs). As no selective PDE8B inhibitors had been reported, a high throughput screen was run with the goal of identifying selective tools for exploring the potential therapeutic utility of PDE8B inhibition. Of the numerous hits, one was particularly attractive since it was amenable to rapid deconstruction leading to inhibitors with very high ligand efficiency (LE) and lipophilic ligand efficiency (LLE). These triazolopyrimidines were optimized for potency, selectivity and ADME properties ultimately leading to compound 42. This compound was highly potent and selective with good bioavailability and advanced into pre-clinical development.

1-((3S,4S)-4-amino-1-(4-substituted-1,3,5-triazin-2-yl) pyrrolidin-3-yl)-5,5-difluoropiperidin-2-one inhibitors of DPP-4 for the treatment of type 2 diabetes.

A 3-amino-4-substituted pyrrolidine series of dipeptidyl peptidase IV (DPP-4) inhibitors was rapidly developed into a candidate series by identification of a polar valerolactam replacement for the lipophilic 2,4,5-trifluorophenyl pharmacophore. The addition of a gem-difluoro substituent to the lactam improved overall DPP-4 inhibition and an efficient asymmetric route to 3,4-diaminopyrrolidines was developed. Advanced profiling of a subset of analogs identified 5o with an acceptable human DPP-4 inhibition profile based on a rat PK/PD model and a projected human dose that was suitable for clinical development.

Piperidinyl-2-phenethylamino inhibitors of DPP-IV for the treatment of type 2 diabetes.

A highly ligand efficient lead molecule was rapidly developed into a DPP-IV selective candidate series using focused small library synthesis. A significant hurdle for series advancement was genetic safety since some agents in this series impaired chromosome division that was detected using the in vitro micronucleus assay. A recently developed high-throughput imaging-based in vitro micronucleus assay enabled the identification of chemical space with a low probability of micronucleus activity. Advanced profiling of a subset within this space identified a compound with a clean safety profile, an acceptable human DPP-IV inhibition profile based on the rat PK/PD model and a projected human dose that was suitable for clinical development.

(3,3-Difluoro-pyrrolidin-1-yl)-[(2S,4S)-(4-(4-pyrimidin-2-yl-piperazin-1-yl)-pyrrolidin-2-yl]-methanone: a potent, selective, orally active dipeptidyl peptidase IV inhibitor.

A series of 4-substituted proline amides was synthesized and evaluated as inhibitors of dipeptidyl pepdidase IV for the treatment of type 2 diabetes. (3,3-Difluoro-pyrrolidin-1-yl)-[(2S,4S)-(4-(4-pyrimidin-2-yl-piperazin-1-yl)-pyrrolidin-2-yl]-methanone (5) emerged as a potent (IC(50) = 13 nM) and selective compound, with high oral bioavailability in preclinical species and low plasma protein binding. Compound 5, PF-00734200, was selected for development as a potential new treatment for type 2 diabetes.

(3R,4S)-4-(2,4,5-Trifluorophenyl)-pyrrolidin-3-ylamine inhibitors of dipeptidyl peptidase IV: synthesis, in vitro, in vivo, and X-ray crystallographic characterization.

A series of pyrrolidine based inhibitors of dipeptidyl peptidase IV were developed from a high throughput screening hit for the treatment of type 2 diabetes. Potency, selectivity, and pharmacokinetic properties were optimized resulting in the identification of a pre-clinical candidate for further profiling.

cis-2,5-dicyanopyrrolidine inhibitors of dipeptidyl peptidase IV: synthesis and in vitro, in vivo, and X-ray crystallographic characterization.

Inhibitors of the glucagon-like peptide-1 (GLP-1) degrading enzyme dipeptidyl peptidase IV (DPP-IV) have been shown to be effective treatments for type 2 diabetes in animal models and in human subjects. A novel series of cis-2,5-dicyanopyrrolidine alpha-amino amides were synthesized and evaluated as inhibitors of dipeptidyl peptidase IV (DPP-IV) for the treatment of type 2 diabetes. 1-({[1-(Hydroxymethyl)cyclopentyl]amino}acetyl)pyrrolidine-2,5-cis-dicarbonitrile (1c) is an achiral, slow-binding (time-dependent) inhibitor of DPP-IV that is selective for DPP-IV over other DPP isozymes and proline specific serine proteases, and which has oral bioavailability in preclinical species and in vivo efficacy in animal models. The mode of binding of the cis-2,5-dicyanopyrrolidine moiety was determined by X-ray crystallography. The hydrochloride salt of 1c was further profiled for development as a potential new treatment for type 2 diabetes.

New fluorinated pyrrolidine and azetidine amides as dipeptidyl peptidase IV inhibitors.

Cyclohexylglycine amides of various fluorinated pyrrolidines and azetidines were prepared and tested for activity against dipeptidyl peptidase IV and in vivo in the KK mouse model of type 2 diabetes. The tetrafluoropyrrolidide, cis-3,4-difluoropyrrolidide and the fluorinated azetidides displayed unexpectedly strong activity.

Synergistic effect on insulin secretion from INS-1 cells of a sulfonylurea and a phosphodiesterase 3 inhibitor.

The effects on insulin secretion from INS-1 cells of varying concentrations of the sulfonylurea glyburide and the PDE3 inhibitor milrinone, separately and in combination were measured. Over a range of concentrations the effects of the two drugs in combination were more than additive. A response surface model was fit to the data and was found to describe the data well. From this model, it was apparent that a significant synergistic effect upon insulin secretion existed over a wide range of combinations of the two drugs.

Troglitazone: the discovery and development of a novel therapy for the treatment of Type 2 diabetes mellitus.

Prior to the introduction of troglitazone, it had been more than 30 years since the last significant improvement in antidiabetic therapy. In view of the pressing need for more effective oral agents for the treatment of Type 2 diabetes mellitus, troglitazone was granted priority review by the FDA and was launched in the USA in 1997. The first of the thiazolidinedione insulin sensitizing agents, troglitazone was quickly followed by rosiglitazone and pioglitazone. The glitazones proved to be effective not only in lowering blood glucose, but also to have beneficial effects on cardiovascular risk. Troglitazone was subsequently withdrawn because of concerns about hepatotoxicity, which appears to be less of a problem with rosiglitazone and pioglitazone. Recent insights into the molecular mechanism of action of the glitazones, which are ligands for the peroxisome proliferator-activated receptors, open the prospect of designing more effective, selective and safer antidiabetic agents. This document will review the history of troglitazone from discovery through clinical development.

CJ-21,164, a new D-glucose-6-phosphate phosphohydrolase inhibitor produced by a fungus Chloridium sp.

A new D-glucose-6-phosphate phosphohydrolase (G6Pase) inhibitor, CJ-21,164 (1) was isolated from the fermentation broth of the fungus Chloridium sp. CL48903. The structure was elucidated to be a novel tetramer of the salicylic acid derivatives by spectroscopic analyses. Compound I inhibited G6Pase in rat liver microsomes with an IC50 of 1.6 microM. Glucose output from hepatocytes isolated from rat liver was inhibited when I was present in the incubation medium, consistent with the role of I as a G6Pase inhibitor.

Glycemic control in mice with targeted disruption of the glucagon receptor gene.

The action of glucagon in the liver is mediated by G-coupled receptors. To examine the role of glucagon in glucose homeostasis, we have generated mice in which the glucagon receptor was inactivated (GR(-/-) mice). Blood glucose levels were somewhat reduced in GR(-/-) mice relative to wild type, in both the fed and fasted state. Plasma insulin levels were not significantly affected. There was no significant effect on fasting plasma cholesterol or triglyceride levels associated with deletion of the glucagon receptor. Glucose tolerance, as assessed by an oral glucose tolerance test, improved. Plasma glucagon levels were strikingly elevated in both fed and fasted animals. Despite a total absence of glucagon receptors, these animals maintained near-normal glycemia and normal lipidemia, in the presence of circulating glucagon concentrations that were elevated by two orders of magnitude.

Thielavins as glucose-6-phosphatase (G6Pase) inhibitors: producing strain, fermentation, isolation, structural elucidation and biological activities.

High-throughput screening of microbial extracts using rat hepatic microsomal glucose-6-phosphatase (G6Pase) led us to find thielavin B as a G6Pase inhibitor with inhibition of glucose output from glucagon-stimulated hepatocytes. Further searching for more potent analogs identified 11 new thielavins F-P in addition to the known thielavins A and B from a fungus Chaetomium carinthiacum ATCC 46463. Thielavin G showed the strongest activity as a G6Pase inhibitor (IC50=0.33 microM), while the IC50 of thielavin B was 5.5 microM. According to the structure-activity relationship, including authentic thielavins C, D and 3 partial hydrolysates from thielavins A and B, 3 benzoic acid-units and carboxylic acid functions are essential for G6Pase inhibition.