Synthesis and evaluation of cyclohexane carboxylic acid head group containing isoxazole and thiazole analogs as DGAT1 inhibitors.

Diacylglycerol acyltransferase 1 (DGAT1) is known to play an important catalytic role in the final step of triglyceride biosynthesis. High fat diet fed DGAT1 knockout mice were resistant to weight gain and exhibited increased insulin and leptin sensitivity thereby indicating a plausible role for DGAT1 inhibitors in the treatment of obesity. 4-Phenylpiperidine-1-carbonyl cyclohexanecarboxylic acid (compound 6, DGAT1 IC50 = 57 nM) has been lately reported as a potent DGAT1 inhibitor. In our search for newer scaffolds possessing potent DGAT1 activity we undertook a systematic diversification of compound 6 to identify a 4-(5-phenylthiazole-2-carboxamido)cyclohexanecarboxylic acid scaffold. Further linker optimization of this scaffold identified compound 9e (DGAT1 IC50 = 14.8 nM) as a potent DGAT1 inhibitor. Coupled with its in vitro potency, compound 9e also exhibited 112 percent plasma triglyceride reduction at a 3 mpk dose in an oral fat tolerance test (FTT) when studied in Swiss mice.

Evaluation of thiazole containing biaryl analogs as diacylglycerol acyltransferase 1 (DGAT1) inhibitors.

Biphenyl carboxylic acids, exemplified by compound 5, are known potent inhibitors of diacylglycerol acyltransferase, DGAT1, an enzyme involved in the final committed step of triglyceride biosynthesis. We have synthesized and evaluated 2-phenylthiazole, 4-phenylthiazole, and 5-phenylthiazole analogs as DGAT1 inhibitors. The 5-phenylthiazole series exhibited potent DGAT1 inhibition when evaluated using an in vitro enzymatic assay and an in vivo fat tolerance test in mice. Compound 33 (IC50 = 23 nM) exhibiting promising oral pharmacokinetic parameters (AUCinf = 7058 ng h/ml, T1/2 = 0.83 h) coupled with 87 percent reduction of plasma triglycerides in vivo may serve as a lead for developing newer anti-obesity agents.

Lead optimization of isocytosine-derived xanthine oxidase inhibitors.

We report our attempts at improving the oral efficacy of low-nanomolar inhibitors of xanthine oxidase from isocytosine series through chemical modifications. Our lead compound had earlier shown good in vivo efficacy when administered intraperitoneally but not orally. Several modifications are reported here which achieved more than twofold improvement in exposure. A compound with significant improvement in oral efficacy was also obtained.

Isocytosine-based inhibitors of xanthine oxidase: design, synthesis, SAR, PK and in vivo efficacy in rat model of hyperuricemia.

Structure-activity relationship studies were carried out for lead generation following structure-guided design approach from an isocytosine scaffold identified earlier for xanthine oxidase inhibition. A 470-fold improvement in in vitro IC(50) was obtained in the process. Five most potent compounds with nanomolar IC(50) values were selected for pharmacokinetics and in vivo experiments. The best compound showed good in vivo activity when administered intraperitoneally but was not active by oral route. The results suggest that improvement in oral exposure could improve the in vivo efficacy of this series.

Synthesis and biological evaluation of isoxazole, oxazole, and oxadiazole containing heteroaryl analogs of biaryl ureas as DGAT1 inhibitors.

Diacylglycerol acyltransferase, DGAT1, is a promising target enzyme for obesity due to its involvement in the committed step of triglyceride biosynthesis. Amino biphenyl carboxylic acids, exemplified by compound 4, are known potent inhibitors of hDGAT1. However the high cLogP and poor solubility of these biphenyl analogs might tend to limit their development. We have synthesized and evaluated compounds containing 3-phenylisoxazole, 5-phenyloxazole, and 3-phenyl-1,2,4-oxadiazole biaryl units for their hDGAT1 inhibition. Our aim in synthesizing such heterocyclic analogs was to improve the cLogP and solubility of these molecules while retaining hDGAT1 potency. Several compounds within the 3-phenylisoxazole series exhibited potent hDGAT1 inhibition when evaluated using an in vitro enzymatic assay. Certain promising compounds were studied for their potential to reduce triglyceride levels using an in vivo fat tolerance test in mice and were also evaluated for any possible improvement to their solubility. Compound 40a (IC(50) = 64 nM) with an in vivo plasma triglyceride reduction of 90 percent, and a solubility of 0.43 mg/ml at pH 7.4 may serve as a new lead for developing newer anti-obesity agents.

Identification of novel isocytosine derivatives as xanthine oxidase inhibitors from a set of virtual screening hits.

In recent years, xanthine oxidase has emerged as an important target not only for gout but also for cardiovascular and metabolic disorders involving hyperuricemia. Contrary to popular belief, recent clinical trials with uricosurics have demonstrated that enhanced excretion of uric acid is, by itself, not adequate to treat hyperuricemia; simultaneous inhibition of production of uric acid by inhibition of xanthine oxidase is also important. Virtual screening of in-house synthetic library followed by in vitro and in vivo testing led to the identification of a novel scaffold for xanthine oxidase inhibition. In vitro activity results corroborated the results from molecular docking studies of the virtual screening hits. The isocytosine scaffold maintains key hydrogen bonding and pi-stacking interactions in the deep end of the xanthine-binding pocket, which anchors it in an appropriate pose to inhibit binding of xanthine and shows promise for further lead optimization using structure-based drug design approach.

Fermentation, Isolation, Structure, and antidiabetic activity of NFAT-133 produced by Streptomyces strain PM0324667.

Type-2 diabetes is mediated by defects in either insulin secretion or insulin action. In an effort to identify extracts that may stimulate glucose uptake, similar to insulin, a high throughput-screening assay for measuring glucose uptake in skeletal muscle cells was established. During the screening studies to discover novel antidiabetic compounds from microbial resources a Streptomyces strain PM0324667 (MTCC 5543, the Strain accession number at Institute of Microbial Technology, Chandigarh, India), an isolate from arid soil was identified which expressed a secondary metabolite that induced glucose uptake in L6 skeletal muscle cells. By employing bioactivity guided fractionation techniques, a tri-substituted simple aromatic compound with anti-diabetic potential was isolated. It was characterized based on MS and 2D NMR spectral data and identified as NFAT-133 which is a known immunosuppressive agent that inhibits NFAT-dependent transcription in vitro. Our investigations revealed the antidiabetic potential of NFAT-133. The compound induced glucose uptake in differentiated L6 myotubes with an EC50 of 6.3 ± 1.8 µM without activating the peroxisome proliferator-activated receptor-γ. Further, NFAT-133 was also efficacious in vivo in diabetic animals and reduced systemic glucose levels. Thus it is a potential lead compound which can be considered for development as a therapeutic for the treatment of type-2 diabetes. We have reported herewith the isolation of the producer microbe, fermentation, purification, in vitro, and in vivo antidiabetic activity of the compound.

Exploration of pyridine containing heteroaryl analogs of biaryl ureas as DGAT1 inhibitors.

The diacylglycerol acyltransferase enzyme, DGAT1, presents itself as a potential target for obesity as this enzyme is dedicated to the final committed step in triglyceride biosynthesis. Biphenyl ureas, exemplified by compound 4, have been reported to be potent hDGAT1 inhibitors. We have synthesized and evaluated 2-pyridyl and 3-pyridyl containing biaryl ureas as hDGAT1 inhibitors. Our aim was to incorporate a heteroaryl scaffold within these molecules thereby improving the cLogP profile and making these compounds more drug-like. Compounds within this series exhibited potent hDGAT1 inhibition when evaluated using an in vitro enzymatic assay. Selected compounds were also subjected to an oral fat tolerance test in mice where the percent triglyceride reduction versus a vehicle control was evaluated. Of the studied heteroaryl analogs compound 44 exhibited an in vitro IC(50) of 17nM and a plasma triglyceride reduction of 79% along with a 12-fold improvement in solubility over the biphenyl urea compound 4.

Discovery and development of selective PPAR gamma modulators as safe and effective antidiabetic agents.

IMPORTANCE OF THE FIELD: PPARgamma full agonists (pioglitazone and rosiglitazone) are the mainstay drugs for the treatment of type 2 diabetes; however, mechanism-based side effects have limited their full therapeutic potential. In recent years, much progress has been achieved in the discovery and development of selective PPARgamma modulators (SPPARgammaMs) as safer alternatives to PPARgamma full agonists. AREAS COVERED IN THIS REVIEW: This review focuses on the preclinical and clinical data of all the SPPARgammaMs discovered so far, retrieved by searching PubMed, Prous Integrity database and company news updates from 1999 to date. WHAT THE READER WILL GAIN: Here we thoroughly discuss SPPARgammaMs' mode of action, briefly examine new ways to identify superior SPPARgammaMs, and finally, compare and contrast the pharmacological and safety profile of various agents. TAKE HOME MESSAGE: The preclinical and clinical findings clearly suggest that selective PPARgamma modulators have the potential to become the next generation of PPARgamma agonists: effective insulin sensitizers with a superior safety profile to that of PPARgamma full agonists.

18F9 (4-(3,6-bis (ethoxycarbonyl)-4,5,6,7-tetrahydrothieno (2,3-c) pyridin-2-ylamino)-4-oxobutanoic acid) enhances insulin-mediated glucose uptake in vitro and exhibits antidiabetic activity in vivo in db/db mice.

Insulin resistance is central to the pathogenesis of type 2 diabetes mellitus. Previous studies have demonstrated that compounds that cause adipogenesis and improve glucose uptake in 3T3-L1 cells are potential insulin sensitizers. Therefore, we evaluated one such compound, 18F9, for (1) adipogenesis in human subcutaneous preadipocyte (SQ) cells, (2) glucose uptake in human skeletal muscle myotubes and SQ cells, and (3) antidiabetic activity in db/db mice. We also investigated its effect on ex vivo glucose uptake in soleus muscle isolated from continuously treated db/db mice. Gene expression profiling in soleus muscle and epididymal fat of db/db mice was performed to understand its effect on glucose metabolism, lipid metabolism, and thermogenesis. 18F9 enhanced adipogenesis in SQ cells and increased glucose uptake in SQ and human skeletal muscle myotubes cells. In db/db mice, 18F9 exhibited dose-dependent reduction in plasma glucose and insulin level. Interestingly, 18F9 was as efficacious as rosiglitazone but did not cause body weight gain and hepatic adverse effects. In addition, 18F9 demonstrated no change in plasma volume in Wistar rats. Furthermore, it enhanced ex vivo glucose uptake in soleus muscles in these mice, which substantiates our in vitro findings. Human peroxisome proliferator activated receptor-gamma transactivation assay revealed a weak peroxisome proliferator activated receptor-gamma transactivation potential (44% of rosiglitazone at 10 mumol/L) of 18F9. Gene expression profiling indicated that 18F9 increased insulin sensitivity mainly through a phosphoinositide 3-kinase-dependent mechanism. 18F9 also up-regulated genes involved in lipid transport and synthesis at par with rosiglitazone. Unlike rosiglitazone, 18F9 elevated the expression of Pdk4. In addition, 18F9 elevated the expression of glycogen synthase and adiponectin significantly higher than rosiglitazone. Taken together, these observations suggest that 18F9 is a safer and potent insulin sensitizer that demonstrates promising antidiabetic activity and is worth further development.

Acute administration of GPR40 receptor agonist potentiates glucose-stimulated insulin secretion in vivo in the rat.

Recently, several in vitro studies have shown that GPR40 receptor activation by free fatty acids (FFAs) results in glucose-dependent insulin secretion. However, whether GPR40 receptor activation results in glucose-dependent insulin secretion in vivo in rats is not known. Therefore, we evaluated the effect of synthetic GPR40 receptor agonist (compound 1) on glucose tolerance test (GTT) in fed, fasted, and insulin-resistant rats. In oral GTT, intraperitoneal GTT, and intravenous GTT, GPR40 receptor agonist improved glucose tolerance, which was associated with increase in plasma insulin level. Interestingly, in GTTs, the rise in insulin levels in agonist-treated group was directly proportional to the rate of rise and peak levels of glucose in control group. Although glibenclamide, a widely used insulin secretagogue, improved glucose tolerance in all GTTs, it did not display insulin release in intraperitoneal GTT or intravenous GTT. In the absence of glucose load, GPR40 receptor agonist did not significantly change the plasma insulin concentration, but did decrease the plasma glucose concentration. Fasted rats exhibited impaired glucose-stimulated insulin secretion (GSIS) as compared with fed rats. Compound 1 potentiated GSIS in fasted state but failed to do so in fed state. Suspecting differential pharmacokinetics, a detailed pharmacokinetic evaluation was performed, which revealed the low plasma concentration of compound 1 in fed state. Consequently, we examined the absorption profile of compound 1 at higher doses in fed state; and at a dose at which its absorption was comparable with that in fasted state, we observed significant potentiation of GSIS. Chronic high-fructose (60%) diet feeding resulted in impaired glucose tolerance, which was improved by GPR40 receptor agonist. Therefore, our results demonstrate for the first time that acute GPR40 receptor activation leads to potentiation of GSIS in vivo and improves glucose tolerance even in insulin-resistant condition in rats. Taken together, these results suggest that GPR40 receptor agonists could be potential therapeutic alternatives to sulfonylureas.