Mukul Jain

Discovery of potent, selective and orally bioavailable triaryl-sulfonamide based PTP1B inhibitors

A novel series of pTyr mimetics containing triaryl-sulfonamide derivatives (5a-r) are reported as potent and selective PTP1B inhibitors. Some of the test compounds (5o and 5p) showed excellent selectivity towards PTP1B over various PTPs, including TCPTP (in vitro). The lead compound 5o showed potent antidiabetic activity (in vivo), along with improved pharmacokinetic profile. These preliminary results confirm discovery of highly potent and selective PTP1B inhibitors for the treatment of T2DM.

Inhibition of the methionine aminopeptidase 2 enzyme for the treatment of obesity.

Worldwide prevalence of obesity has nearly doubled since 1980. Obesity is the result of interactions among the environmental factors, genetic predisposition, and human behavior. Even modest weight reduction in obese patients provides beneficial health outcomes. For effective weight reduction, a drug should either increase energy expenditure or decrease energy intake without causing serious adverse effects. To overcome lack of efficacy and central nervous system related side effects, exploitation of the peripheral mechanism of anti-obesity action is needed. Inhibition of pathological angiogenesis in adipose tissue is one such peripheral mechanism that has attracted the attention of researchers in this area. Although originally developed as anti-cancer agents, methionine aminopeptidase (MetAP2) inhibitors induce significant and sustained weight reduction. Here, we review preclinical and clinical pharmacology of MetAP2 inhibitors. Beloranib is a prototype MetAP2 inhibitor, and currently in advanced clinical trials for the treatment of obesity. Clinical data of beloranib indicate that MetAP2 inhibitors could be a future treatment option for weight reduction without serious adverse effects. Further clinical data from Phase III trials will add to our growing knowledge of MetAP2 inhibitor potential for anti-obesity therapy.

Co-agonist of glucagon and GLP-1 reduces cholesterol and improves insulin sensitivity independent of its effect on appetite and body weight in diet-induced obese C57 mice

Dual agonism of glucagon and glucagon-like peptide-1 (GLP-1) receptors reduce body weight without inducing hyperglycemia in rodents. However, the effect of a co-agonist on insulin sensitivity and lipid metabolism has not been thoroughly assessed. Diet-induced obese (DIO) mice received 0.5 mg·kg(-1) of co-agonist or 2.5 mg·kg(-1) of glucagon or 8 μg·kg(-1) of exendin-4 by subcutaneous route, twice daily, for 28 days. A separate group of mice was pair-fed to the co-agonist-treated group for 28 days. Co-agonist treatment reduced food intake and reduced body weight up to 28 days. In addition, it reduced leptin levels and increased fibroblast growth factor 21 (FGF21) levels in plasma, when compared with control and pair-fed groups. Co-agonist treatment decreased triglyceride levels in serum and liver and reduced serum cholesterol, mainly due to reduction in low-density lipoprotein (LDL) cholesterol. These changes were not seen with pair-fed controls. Co-agonist treatment improved glucose tolerance and increased insulin sensitivity, as observed during glucose and insulin-tolerance test, hyperinsulinemic clamp, and reduced gluconeogenesis, as observed in pyruvate-tolerance test. The effects on insulin sensitivity and lipid levels are mostly independent of the food intake or body weight lowering effect of the co-agonist.

Exendin-4 reduces glycemia by increasing liver glucokinase activity: an insulin independent effect.

Exendin-4 is a stable peptide agonist of GLP-1 receptor that exhibits insulinotropic actions. Some in vivo studies indicated insulin-independent glucoregulatory actions of exendin-4. That finding prompted us to evaluate effects of exendin-4 on liver glucose metabolism. Acute and chronic treatment of exendin-4 resulted in increased hepatic glucokinase activity in db/db mice but not in lean C57 mice. The stimulatory effect of exendin-4 on glucokinase activity was abrogated by exendin 9-39, a GLP-1 antagonist. Exposure of hepatocytes isolated from db/db mice to exendin-4 elicited a rapid increase in cAMP, which was synergized by IBMX, an inhibitor of cAMP degradation. The GLP-1 antagonist, exendin 9-39, has abolished the cAMP generating effects of exendin-4 as well. Furthermore, chronic treatment of exendin-4 in streptozotocin-treated C57 mice resulted in restoration of hepatic glycogen, an indicator of improved glucose metabolism, without apparent changes in serum insulin levels. In conclusion, exendin-4 increased glucokinase enzyme protein and activity in liver via a mechanism parallel to and independent of insulin. Exendin-4-induced increase in hepatic glucokinase activity is more pronounced in the presence of hepatic insulin resistance. This beneficial effect of exendin-4 on liver glucokinase activity may be mediated by GLP-1 receptor.

Pathophysiological Mechanism of Bone Loss in Type 2 Diabetes Involves Inverse Regulation of Osteoblast Function by PGC-1α and Skeletal Muscle Atrogenes: AdipoR1 as a Potential Target for Reversing Diabetes-Induced Osteopenia

Type 2 diabetes is associated with increased fracture risk and delayed facture healing; the underlying mechanism, however, remains poorly understood. We systematically investigated skeletal pathology in leptin receptor–deficient diabetic mice on a C57BLKS background (db). Compared with wild type (wt), db mice displayed reduced peak bone mass and age-related trabecular and cortical bone loss. Poor skeletal outcome in db mice contributed high-glucose– and nonesterified fatty acid–induced osteoblast apoptosis that was associated with peroxisome proliferator–activated receptor γ coactivator 1-α (PGC-1α) downregulation and upregulation of skeletal muscle atrogenes in osteoblasts. Osteoblast depletion of the atrogene muscle ring finger protein-1 (MuRF1) protected against gluco- and lipotoxicity-induced apoptosis. Osteoblast-specific PGC-1α upregulation by 6-C-β-d-glucopyranosyl-(2S,3S)-(+)-5,7,3′,4′-tetrahydroxydihydroflavonol (GTDF), an adiponectin receptor 1 (AdipoR1) agonist, as well as metformin in db mice that lacked AdipoR1 expression in muscle but not bone restored osteopenia to wt levels without improving diabetes. Both GTDF and metformin protected against gluco- and lipotoxicity-induced osteoblast apoptosis, and depletion of PGC-1α abolished this protection. Although AdipoR1 but not AdipoR2 depletion abolished protection by GTDF, metformin action was not blocked by AdipoR depletion. We conclude that PGC-1α upregulation in osteoblasts could reverse type 2 diabetes–associated deterioration in skeletal health.

11β-Hydroxysteroid dehydrogenase type 1: potential therapeutic target for metabolic syndrome

Obesity and associated metabolic syndrome is one of the greatest health threat to the modern society. Cortisol excess and the glucocorticoid receptor signaling pathway in the metabolically active tissues have been implicated in the development of diabetes and obesity. The key enzyme in the regeneration of intracellular cortisol is 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). 11β-HSD1 increases local cortisol production in metabolically active tissue types such as adipose and liver. Recent studies have shown that mice deficient in this enzyme are resistant to diet induced obesity and have increased insulin and leptin sensitivity. Clinical and preclinical studies indicate that 11β-HSD1 inhibitors are likely to exert major pharmacological actions in metabolically active tissues. These effects suggest that inhibition of 11β-HSD1 in vivo may be a novel therapeutic target for obesity, diabetes, and metabolic syndrome. The advancement of numerous structural classes of selective 11β-HSD1 inhibitors further indicates that more refined design and screening for isoform and tissue selectivity would yield potential therapeutics in this area.

Discovery of Orally Active, Potent, and Selective Benzotriazole-Based PTP1B Inhibitors**

The worldwide incidence of metabolic syndromes such as obesity and diabetes are increasing at an alarming rate. Patients that suffer from obesity-induced type 2 diabetes (informally known as diabesity) are at increased risk of cardiovascular disease; their numbers pose a significant economic burden on health services. Type 2 diabetes mellitus (T2DM) is clinically characterized by increased blood glucose levels, either due to defects in insulin secretion, insulin resistance, or both. Current treatments for diabetic patients include various oral antihyperglycemic agents; however, over a period of time nearly half of T2DM sufferers lose their response to these agents and thereby require insulin therapy. Except incretin therapies, most of the available anti-hyperglycemic agents including insulin promote weight gain, which further aggravates obesity-associated cardiovascular risk and insulin resistance. Thus, there is an urgent need to develop novel agents for glycemic control that can complement existing therapies and prevent the progression of secondary complications associated with diabesity. In recent years, development of protein tyrosine phosphatase 1B (PTP1B) inhibitors has been considered as one of the best validated biological targets for the treatment of T2DM. PTP1B acts as a negative regulator in insulin signaling pathways; it dephosphorylates key tyrosine residues within the regulatory domain of the b-subunit of the insulin receptor. Thus, the inhibition of PTP1B activity has the potential for enhancing insulin action by prolonging the phosphorylated state of the insulin receptor. Gene knockout studies in animals have also demonstrated that PTP1B / mice show increased insulin sensitivity and are resistant to diet-induced obesity. Over the past two decades, several structurally diverse small-molecule-based PTP1B inhibitors have been developed, including Ertiprotafib, which was discontinued in phase II clinical trials owing to lack of efficacy and dose-dependent side effects. Most of the initial PTP1B inhibitors, such as phosphonates, carboxylic acids, and difluoromethylphosphonates (DFMPs), were designed to bind to the active site (site 1/A) by mimicking the phosphotyrosine (pTyr) substrate. However, achieving PTP1B selectivity over closely associated PTPs (PTPa, LAR, CD45, VHR, SHP-1, SHP-2, and T-cell protein tyrosine phosphatase (TCPTP)) is one of the major challenges, as most of the closely associated PTPs, particularly TCPTP, share a high degree of primary sequence identity (92%) in the active site (pTyr binding pocket). Lack of oral bioavailability is another important issue in the development of potent and selective PTP1B inhibitors, as the majority of the active-site-directed PTP1B inhibitors exhibit limited cell permeability due to the presence of negatively charged polar groups. To address this problem, Zhang and colleagues identified an additional noncatalytic aryl phosphate binding site (site 2/B) proximal to the catalytic phosphate binding site. Site B of PTP1B differs from that of TCPTP by a few amino acids (F52Y and A27S) and thus offers an opportunity to improve selectivity over TCPTP. Consequently, dual-site inhibitors were designed to bind across both sites A and B, to achieve additive effects and thereby improve potency and selectivity toward PTP1B over closely associated PTPs. Based on this dual binding site concept, various DFMP-based PTP1B inhibitors such as arylketone 1, benzotriazoles 2a and 2b, and naphthyl derivative 3 were developed (Figure 1). The X-ray crystal structure of PTP1B in complex with compound 2b reveals that sites A and B each have a DFMP moiety anchored into it. The benzotriazole ring system also functions as an anchor and is located under the YRD loop, thereby rigidly locking the molecule into the active site and providing good selectivity for PTP1B over other PTPs. The fourth substituent (benzene ring) occupies a hydrophobic pocket. Altogether, this signifies that the presence of all four substituents oriented rigidly by the molecule’s stereocenter is essential for high potency and selectivity. Although results of oral bioavailability and in vivo antidiabetic activity assays for compound 2a have yet to be published, in vitro results show improved PTP1B inhibitory activity (IC50= 5 nm) and moderate selectivity (sevenfold) over TCPTP (IC50= 36 nm). The X-ray crystal structure of PTP1B in complex with compound 2a illustrates that a methoxy group aligns very closely (3.7 ) to the side chain of F52 (site B). Oral administration of compounds 1 and 3 demonstrated good antidiabetic activity (compound 3 : ED50=0.8 mgkg , p.o.) and oral bioavailability (compounds 1 and 3: F=13 and 24%, respectively) in different animal species, despite their moderate in vitro PTP1B inhibitory activity (IC50=120 nm) and poor selectivity [a] D. Patel, Dr. M. Jain, Dr. R. Bahekar, P. Jadav, B. Darji, Y. Siriki, Dr. D. Bandyopadhyay, Dr. A. Joharapurkar, S. Kshirsagar, H. Patel, M. Shaikh, Dr. K. V. V. M. Sairam, P. Patel Department of Medicinal Chemistry, New Drug Discovery Division Zydus Research Centre, Sarkhej-Bavla N.H. 8A Moraiya, Ahmedabad 382210 (India) Fax: (+91)2717-665-355 E-mail : rajeshbahekar@zyduscadila.com [b] D. Patel, Prof. S. R. Shah Department of Chemistry, Faculty of Science M.S. University of Baroda, Vadodara 390002 (India) Fax: (+91)0265-79-3693 E-mail : Shailesh-chem@msubaroda.ac.in [**] ZRC communication No. 378 (part of PhD thesis work of D.P.) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/cmdc.201100077.

Efficient Synthesis of Unsymmetrical Dibenzothiophenes by Acid-Mediated Intramolecular Cyclization of Biaryl Methyl Sulfoxides

Abstract A convenient and high-yielding synthesis of unsymmetrical dibenzothiophenes has been achieved by an acid-mediated ring closure of the biphenyl ring having a sulfoxide substituent at the ortho position. Various functional groups are well tolerated in this methodology. GRAPHICAL ABSTRACT

Saroglitazar, a novel PPARα/γ agonist with predominant PPARα activity, shows lipid‐lowering and insulin‐sensitizing effects in preclinical models

Saroglitazar is a novel nonthiazolidinediones (TZD) and nonfibric acid derivative designed to act as dual regulator of lipids and glucose metabolism by activating peroxisome proliferator‐activated receptors (PPAR). These studies evaluate the efficacy and safety profile of Saroglitazar in preclinical in vitro and in vivo models. The EC50 values of Saroglitazar assessed in HepG2 cells using PPAR transactivation assay for hPPARα and hPPARγ were 0.65 pmol/L and 3 nmol/L, respectively. In db/db mice, 12‐day treatment with Saroglitazar (0.01–3 mg/kg per day, orally) caused dose‐dependent reductions in serum triglycerides (TG), free fatty acids (FFA), and glucose. The ED50 for these effects was found to be 0.05, 0.19, and 0.19 mg/kg, respectively with highly significant (91%) reduction in serum insulin and AUC‐glucose following oral glucose administration (59%) at 1 mg/kg dose. Significant reduction in serum TG (upto 90%) was also observed in Zucker fa/fa rats, Swiss albino mice, and in high fat ‐high cholesterol (HF‐HC)‐fed Golden Syrian hamsters. LDL cholesterol was significantly lowered in hApoB100/hCETP double transgenic mice and HF‐HC diet fed Golden Syrian Hamsters. Hyperinsulinemic‐Euglycemic clamp study in Zucker fa/fa rats demonstrated potent insulin‐sensitizing activity. Saroglitazar also showed a significant decrease in SBP (22 mmHg) and increase (62.1%) in serum adiponectin levels in Zucker fa/fa rats. A 90‐day repeated dose comparative study in Wistar rats and marmosets confirmed efficacy (TG lowering) potential of Saroglitazar and has indicated low risk of PPAR‐associated side effects in humans. Based on efficacy and safety profile, Saroglitazar appears to have good potential as novel therapeutic agent for treatment of dyslipidemia and diabetes.

Cannabinoid receptor 1 antagonist treatment induces glucagon release and shows an additive therapeutic effect with GLP-1 agonist in diet-induced obese mice

Cannabinoid 1 (CB1) receptor antagonists reduce body weight and improve insulin sensitivity. Preclinical data indicates that an acute dose of CB1 antagonist rimonabant causes an increase in blood glucose. A stable analog of glucagon-like peptide 1 (GLP-1), exendin-4 improves glucose-stimulated insulin secretion in pancreas, and reduces appetite through activation of GLP-1 receptors in the central nervous system and liver. We hypothesized that the insulin secretagogue effect of GLP-1 agonist exendin-4 may synergize with the insulin-sensitizing action of rimonabant. Intraperitoneal as well as intracerebroventricular administration of rimonabant increased serum glucose upon glucose challenge in overnight fasted, diet-induced obese C57 mice, with concomitant rise in serum glucagon levels. Exendin-4 reversed the acute hyperglycemia induced by rimonabant. The combination of exendin-4 and rimonabant showed an additive effect in the food intake, and sustained body weight reduction upon repeated dosing. The acute efficacy of both the compounds was additive for inducing nausea-like symptoms in conditioned aversion test in mice, whereas exendin-4 treatment antagonized the effect of rimonabant on forced swim test upon chronic dosing. Thus, the addition of exendin-4 to rimonabant produces greater reduction in food intake owing to increased aversion, but reduces the other central nervous system side effects of rimonabant. The hyperglucagonemia induced by rimonabant is partially responsible for enhancing the antiobesity effect of exendin-4.