Design,synthesis and anti-diabetic activity of triazolotriazine derivatives as dipeptidyl peptidase-4 (DPP-4) inhibitors

Type 2 diabetes mellitus (T2DM) is one of the major global metabolic disorders characterized by insulin resistance and chronic hyperglycemia. Inhibition of the enzyme, dipeptidyl peptidase-4 (DPP-4) has been proved as successful and safe therapy for the treatment of T2DM since last decade. In order to design novel DPP-4 inhibitors, various in silico studies such as 3D-QSAR, pharmacophore modeling and virtual screening were performed and on the basis of the combined results of them, total 50 triazolo[5,1-c][1,2,4]triazine derivatives were designed and mapped on the best pharmacophore model. From this, best 25 derivatives were docked onto the active site of DPP-4 enzyme and in silico ADMET properties were also predicted. Finally, top 17 derivatives were synthesized and characterized using FT-IR, Mass, ¹H NMR and ¹³C NMR spectroscopy. Purity of compounds was checked using HPLC. These derivatives were then evaluated for in vitro DPP-4 inhibition. The most promising compound 15q showed 28.05 μM DPP-4 IC₅₀ with 8–10-fold selectivity over DPP-8 and DPP-9 so selected for further in vivo anti-diabetic evaluation. During OGTT in normal C57BL/6J mice, compound 15q reduced blood glucose excursion in a dose-dependent manner. Chronic treatment for 28 days with compound 15q improved the serum glucose levels in type 2 diabetic Sprague Dawley rats wherein diabetes was induced by high fat diet and low dose streptozotocin. This suggested that compound 15q is a moderately potent and selective hit molecule which can be further optimized structurally to increase the efficacy and overall pharmacological profile as DPP-4 inhibitor.     

Synthesis and biological evaluation of novel benzyl-substituted (S)-phenylalanine derivatives as potent dipeptidyl peptidase 4 inhibitors

A series of novel benzyl-substituted (S)-phenylalanine derivatives were synthesized and evaluated for their dipeptidyl peptidase 4 (DPP-4) inhibitory activity and selectivity. It was found that most synthesized target compounds were potent DPP-4 inhibitors with IC₅₀ values in 3.79–25.52 nM, which were significantly superior to that of the marketed drug sitagliptin. Furthermore, the 4-fluorobenzyl substituted phenylalanine derivative 6g not only displayed the potent DPP-4 inhibition with an IC₅₀ value of 3.79 nM, but also showed better selectivity against DPP-4 over other related enzymes including DPP-7, DPP-8, and DPP-9. In an oral glucose tolerance test (OGTT) in normal Sprague Dawley rats, compound 6g reduced blood glucose excursion in a dose-dependent manner.     

(R)-3-Amino-1-((3aS,7aS)-octahydro-1H-indol-1-yl)-4-(2,4,5-trifluorophenyl)butan-1-one derivatives as potent inhibitors of dipeptidyl peptidase-4: Design,synthesis, biological evaluation,and molecular modeling

A series of (R)-3-amino-1-((3aS,7aS)-octahydro-1H-indol-1-yl)-4-(2,4,5-trifluorophenyl)butan-1-one derivatives was designed, synthesized, and evaluated as novel inhibitors of dipeptidyl peptidase-4 (DPP-4) for the treatment of type 2 diabetes. Most of the synthesized compounds demonstrated good inhibition activities against DPP-4. Among these, compounds 3e, 4c, 4l, and 4n exhibited prominent inhibition activities against DPP-4, with IC₅₀s of 0.07, 0.07, 0.14, and 0.17 μM, respectively. The possible binding modes of compounds 3e and 4n with dipeptidyl peptidase-4 were also explored by molecular docking simulation. These potent DPP-4 inhibitors were optimized for the absorption, distribution, metabolism, and excretion (ADME) properties, and compound 4n displayed an attractive pharmacokinetic profile (F = 96.3%, t_1/2 = 10.5 h).     

Design and synthesis of quinazoline-3,4-(4H)-diamine endowed with thiazoline moiety as new class for DPP-4 and DPPH inhibitor

New N3-benzylidene (substituted)-2-phenyl-N4-(thiazol-2-yl)-quinazoline-3,4-(4H)-diamine derivatives were design and synthesized by a sequence of reactions starting from appropriate 6-methyl anthranilic acid. The title compounds were screened for in vitro dipeptidyl peptidase IV (DPP-4) inhibitory activity and diphenyl-2-picryl-hydrazyl (DPPH) assay and results showed significant to good activity in compared to Linagliptin for antidiabetic activity and Ascorbic acid for antioxidant activity. Compound 7g (IC₅₀ = 0.76 nM) exhibited most promising DPP-4 inhibitory activity and also showed good antioxid and result. Docking study was also performed to provide an insight about the binding mode into binding sites of DPP-4 enzyme. Hopefully in future, compound 7g could be used as a lead compound for developing new antidiabetic agent with good antioxidant property.     

Synthesis and activity of novel tetrazole compounds and their pyrazole-4-carbonitrile precursors against Leishmania spp

A new series of 5-(1-aryl-3-methyl-1H-pyrazol-4-yl)-1H-tetrazole derivatives (4a–m) and their precursor 1-aryl-3-methyl-1H-pyrazole-4-carbonitriles (3a–m) were synthesized and evaluated as antileishmanials against Leishmania braziliensis and Leishmania amazonensis promastigotes in vitro. In parallel, the cytotoxicity of these compounds was evaluated on the RAW 264.7 cell line. The results showed that among the assayed compounds the substituted 3-chlorophenyl (4a) (IC₅₀/24 h = 15 ± 0.14 μM) and 3,4-dichlorophenyl tetrazoles (4d) (IC₅₀/24 h = 26 ± 0.09 μM) were the most potent against L. braziliensis promastigotes, as compared the reference drug pentamidine, which presented IC₅₀ = 13 ± 0.04 μM. In addition, 4a and 4d derivatives were less cytotoxic than pentamidine. However, these tetrazole derivatives (4) and pyrazole-4-carbonitriles precursors (3) differ against each of the tested species and were more effective against L.braziliensis than on L. amazonensis.     

Synthesis and biological evaluation of 5-carbamoyl-2-phenylpyrimidine derivatives as novel and potent PDE4 inhibitors

5-Carbamoyl-2-phenylpyrimidine derivative 2 has been identified as a phosphodiesterase 4 (PDE4) inhibitor with moderate PDE4B inhibitory activity (IC₅₀ = 200 nM). Modification of the carboxylic acid moiety of 2 gave N-neopentylacetamide derivative 10f, which had high in vitro PDE4B inhibitory activity (IC₅₀ = 8.3 nM) and in vivo efficacy against lipopolysaccharide (LPS)-induced pulmonary neutrophilia in mice (ID₅₀ = 16 mg/kg, ip). Furthermore, based on the X-ray crystallography of 10f bound to the human PDE4B catalytic domain, we designed 7,8-dihydro-6H-pyrido[4,3-d]pyrimidin-5-one derivative 39 which has a fused bicyclic lactam scaffold. Compound 39 exhibited excellent inhibitory activity against LPS-induced tumor necrosis factor alpha (TNF-α) production in mouse splenocytes (IC₅₀ = 0.21 nM) and in vivo anti-inflammatory activity against LPS-induced pulmonary neutrophilia in mice (41% inhibition at a dose of 1.0 mg/kg, i.t.).     

Molecular design,synthesis and biological evaluation of cyclic imides bearing benzenesulfonamide fragment as potential COX-2 inhibitors. Part 2

A group of cyclic imides (1–10) was designed for evaluation as a selective COX-2 inhibitors and investigated in vivo for their anti-inflammatory activity. Compounds 6a, 6b, 8a, 8b, 9a, 9b, 10a and 10b were proved to be potent COX-2 inhibitors with IC₅₀ range of 0.1–4.0 μM. In vitro COX-1/COX-2 inhibition structure–activity studies identified compound 8a as a highly potent (IC₅₀ = 0.1 μM), and an extremely selective [COX-2 (SI) > 1000] comparable to celecoxib [COX-2 (SI) > 384], COX-2 inhibitor that showed superior anti-inflammatory activity (ED₅₀ = 72.4 mg/kg) relative to diclofenac (ED₅₀ = 114 mg/kg). Molecular modeling was carried out through docking the designed compounds into the COX-2 binding site to predict if these compounds have analogous binding mode to the COX-2 inhibitors. The study showed that the homosulfonamide fragment of 8a inserted deep inside the 2°-pocket of the COX-2 active site, where the SO₂NH₂ group underwent H-bonding interaction with Gln¹⁹²(2.95 Å), Phe⁵¹⁸(2.82 Å) and Arg⁵¹³(2.63 and 2.73 Å). Docking study of the synthesized compound 8a into the active site of COX-2 revealed a similar binding mode to SC-558, a selective COX-2 inhibitor.     

Design,synthesis, and pharmacological evaluation of N-(4-mono and 4,5-disubstituted thiazol-2-yl)-2-aryl-3-(tetrahydro-2H-pyran-4-yl)propanamides as glucokinase activators

A series of N-thiazole substituted arylacetamides were designed on the basis of metabolic mechanism of the aminothiazole fragment as glucokinase (GK) activators for the treatment of type 2 diabetes. Instead of introducing a substituent to block the metabolic sensitive C-5 position on the thiazole core directly, a wide variety of C-4 or both C-4 and C-5 substitutions were explored. Compound R-9k bearing an iso-propyl group as the C-4 substituent was found possessing the highest GK activation potency with an EC₅₀ of 0.026 μM. This compound significantly increased both glucose uptake and glycogen synthesis in rat primary cultured hepatocytes. Moreover, single oral administration of compound R-9k exerted significant reduction of blood glucose levels in both ICR and ob/ob mice. These promising results indicated that compound R-9k is a potent orally active GK activator, and is warranted for further investigation as a new anti-diabetic treatment.     

Identification of the fused bicyclic 4-amino-2-phenylpyrimidine derivatives as novel and potent PDE4 inhibitors

2-Phenyl-4-piperidinyl-6,7-dihydrothieno[3,4-d]pyrimidine derivative (2) was found to be a new PDE4 inhibitor with moderate PDE4B activity (IC₅₀ = 150 nM). A number of derivatives with a variety of 4-amino substituents and fused bicyclic pyrimidines were synthesized. Among these, 5,5-dioxo-7,8-dihydro-6H-thiopyrano[3,2-d]pyrimidine derivative (18) showed potent PDE4B inhibitory activity (IC₅₀ = 25 nM). Finally, N-propylacetamide derivative (31b) was determined as a potent inhibitor for both PDE4B (IC₅₀ = 7.5 nM) and TNF-α production in mouse splenocytes (IC₅₀ = 9.8 nM) and showed good in vivo anti-inflammatory activity in the LPS-induced lung inflammation model in mice (ID₅₀ = 18 mg/kg). The binding mode of the new inhibitor (31e) in the catalytic site of PDE4B is presented based on an X-ray crystal structure of the ligand–enzyme complex.     

New 1,2-diaryl-4-substituted-benzylidene-5-4H-imidazolone derivatives: Design,synthesis and biological evaluation as potential anti-inflammatory and analgesic agents

A new series of 1,2-diaryl-4-substituted-benzylidene-5-4H-imidazolone derivatives 10a-h was designed and synthesized for evaluation as selective COX-2 inhibitors, anti-inflammatory agents and as analgesic agents. All compounds were more selective for COX-2 isozyme and showed good in vivo anti-inflammatory activity. Compounds 10a, 10b, 10e and 10f were the most COX-2 selective compounds (S.I. = 10.76, 10.87, 8.69 and 9.14 respectively), the most potent anti-inflammatory derivatives (ED₅₀ = 65.7, 60.2, 76.3 and 107.4 μmol/kg respectively) in comparison with Celecoxib (COX-2 S.I. = 8.61, ED₅₀ = 82.2 μmol/kg) and were less ulcerogenic (ulcer indexes = 1.22–3.02) than Ibuprofen (ulcer index = 20.25) and comparable to Celecoxib (ulcer index = 2.93). The four derivatives (10a, 10b, 10e and 10f) showed considerable analgesic activities which are clearly parallel to their anti-inflammatory activities.     

Synthesis,biological evaluation and docking analysis of 3-methyl-1-phenylchromeno[4,3-c]pyrazol-4(1H)-ones as potential cyclooxygenase-2 (COX-2) inhibitors

As a part of our continued efforts to discover new COX inhibitors, a series of 3-methyl-1-phenylchromeno[4,3-c]pyrazol-4(1H)-ones were synthesized and evaluated for in vitro COX inhibitory potential. Within this series, seven compounds (3a–d, 3h, 3k and 3q) were identified as potential and selective COX-2 inhibitors (COX-2 IC₅₀’s in 1.79–4.35 μM range; COX-2 selectivity index (SI) = 6.8–16.7 range). Compound 3b emerged as most potent (COX-2 IC₅₀ = 1.79 μM; COX-1 IC₅₀ >30 μM) and selective COX-2 inhibitor (SI >16.7). Further, compound 3b displayed superior anti-inflammatory activity (59.86% inhibition of edema at 5 h) in comparison to celecoxib (51.44% inhibition of edema at 5 h) in carrageenan-induced rat paw edema assay. Structure–activity relationship studies suggested that N-phenyl ring substituted with p-CF₃ substituent (3b, 3k and 3q) leads to more selective inhibition of COX-2. To corroborate obtained experimental biological data, molecular docking study was carried out which revealed that compound 3b showed stronger binding interaction with COX-2 as compared to COX-1.     

Discovery of novel free fatty acid receptor 1 agonists bearing triazole core via click chemistry

The free fatty acid receptor 1 (FFA1/GPR40) is a novel antidiabetic target based on particular mechanism in enhancing glucose-stimulated insulin secretion. Most of reported FFA1 agonists, however, have been suffered from relatively high lipophilicity and molecular weight. Aiming to develop potent agonists with improved physicochemical property, 25 compounds containing triazole scaffold and various carboxylic acid fragments were synthesized via the click chemistry. Among them, the optimal lead compound 26 with relatively low lipophicity (Log D_7.4 = 1.95) and molecular weight (Mw = 391.78) exhibited a considerable FFA1 agonistic activity (36.15%). In addition, compound 26 revealed a significant improvement in the glucose tolerance with a 21.4% and 14.2% reduction of glucose AUC_0–2h in normal ICR mice and type 2 diabetic C57BL/6 mice, respectively. All of these results demonstrated that compound 26 was considered to be a promising lead compound suitable for further optimization.     

Synthesis and anti-hyperglycemic activity of hesperidin derivatives

A series of hesperidin derivatives were prepared and identified by IR, ¹H NMR, and MS spectra. These compounds were evaluated in vitro and in vivo based on α-glucosidase inhibition, glucose consumption of HepG2 cells, and blood glucose level in streptozotocin-induced diabetic mice. The results revealed that all the compounds exhibited anti-hyperglycemic activities. The inhibition at 10^?3 M of compounds 3 and 7a on α-glucosidase were 55.02% and 53.34%, respectively, as compared to 54.80% by acarbose. Treated by compound 3 and the reference drug metformin, glucose consumption of HepG2 cell were 1.78 and 2.11 mM, respectively. After the streptozotocin-induced diabetic mice were oral administrated with compound 3 at 100 mg kg^?1 d^?1 for 10 days, the blood glucose level of 3 treated mice (13.23 mM, P <0.05) showed significant difference when compared to model control (23.03 mM). Thus, compound 3 exhibited promising anti-hyperglycemic activity.     

Synthesis and SAR of derivatives based on 2-biarylethylimidazole as bombesin receptor subtype-3 (BRS-3) agonists for the treatment of obesity

This Letter describes a series of potent and selective BRS-3 agonists containing a biarylethylimidazole pharmacophore. Extensive SAR studies were carried out with different aryl substitutions. This work led to the identification of a compound 2-{2-[4-(pyridin-2-yl)phenyl]ethyl}-5-(2,2-dimethylbutyl)-1H-imidazole 9 with excellent binding affinity (IC₅₀ = 18 nM, hBRS-3) and functional agonist activity (EC₅₀ = 47 nM, 99% activation). After oral administration, compound 9 had sufficient exposure in diet induced obese mice to demonstrate efficacy in lowering food intake and body weight via BRS-3 activation.     

Discovery and preclinical profile of teneligliptin (3-[(2S,4S)-4-[4-(3-methyl-1-phenyl-1H-pyrazol-5-yl)piperazin-1-yl]pyrrolidin-2-ylcarbonyl]thiazolidine): A highly potent,selective, long-lasting and orally active dipeptidyl peptidase IV inhibitor for the treatment of type 2 diabetes

Dipeptidyl peptidase IV (DPP-4) inhibition is suitable mechanism for once daily oral dosing regimen because of its low risk of hypoglycemia. We explored linked bicyclic heteroarylpiperazines substituted at the γ-position of the proline structure in the course of the investigation of l-prolylthiazolidines. The efforts led to the discovery of a highly potent, selective, long-lasting and orally active DPP-4 inhibitor, 3-[(2S,4S)-4-[4-(3-methyl-1-phenyl-1H-pyrazol-5-yl)piperazin-1-yl]pyrrolidin-2-ylcarbonyl]thiazolidine (8g), which has a unique structure characterized by five consecutive rings. An X-ray co-crystal structure of 8g in DPP-4 demonstrated that the key interaction between the phenyl ring on the pyrazole and the S₂ extensive subsite of DPP-4 not only boosted potency, but also increased selectivity. Compound 8g, at 0.03 mg/kg or higher doses, significantly inhibited the increase of plasma glucose levels after an oral glucose load in Zucker fatty rats. Compound 8g (teneligliptin) has been approved for the treatment of type 2 diabetes in Japan.     

Design,synthesis and biological evaluation of some novel benzothiazole/benzoxazole and/or benzimidazole derivatives incorporating a pyrazole scaffold as antiproliferative agents

In an aim at developing new antiproliferative agents, new series of benzothiazole/benzoxazole and/or benzimidazole substituted pyrazole derivatives 11a-c, 12a-c and 13a-c were prepared and evaluated for their antiproliferative activity against breast carcinoma (MCF-7) and non-small cell lung cancer (A549) cell lines. The target compound, 2-acetyl-4-[(3-(1H-benzimidazol-2-yl)-phenyl]-hydrazono-5-methyl-2,4-dihydropyrazol-3-one (12a) was the most active compound against both MCF-7 and A549 cell lines with half maximal inhibitory concentrations (IC₅₀) = 6.42 and 8.46 μM, respectively. Furthermore, the inhibitory activity of the all the target compounds against COX enzymes was recorded as a proposed mechanism for their antiproliferative activity. The obtained results revealed that the benzothiazolopyrazolone derivative 13c was the most potent COX-2 inhibitor (IC₅₀ = 0.10 μM), while the 5-acetylbenzimidazolylpyrazolone derivative 12a was the most COX-2 selective (S.I. = 104.67) in comparison with celecoxib (COX-2 IC₅₀ = 1.11 μM, S.I. = 13.33). Docking simulation on the most active compounds 12a and 13c had been performed to investigate the binding interaction of these active compounds within the binding site of COX-2 enzyme. Collectively, this work demonstrated the promising activity of the newly designed compounds as leads for further development into antiproliferative agents.     

Discovery of novel HCV inhibitors: Synthesis and biological activity of 6-(indol-2-yl)pyridine-3-sulfonamides targeting hepatitis C virus NS4B

A novel series of 6-(indol-2-yl)pyridine-3-sulfonamides was prepared and evaluated for their ability to inhibit HCV RNA replication in the HCV replicon cell culture assay. Preliminary optimization of this series furnished compounds with low nanomolar potency against the HCV genotype 1b replicon. Among these, compound 8c has identified as a potent HCV replicon inhibitor (EC₅₀ = 4 nM) with a selectivity index with respect to cellular GAPDH of more than 2500. Further, compound 8c had a good pharmacokinetic profile in rats with an IV half-life of 6 h and oral bioavailability (F) of 62%. Selection of HCV replicon resistance identified an amino acid substitution in HCV NS4B that confers resistance to these compounds. These compounds hold promise as a new chemotype with anti-HCV activity mediated through an underexploited viral target.     

(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 (IC₅₀ = 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.     

1-(4-Methane(amino)sulfonylphenyl)-3-(4-substituted-phenyl)-5-(4-trifluoromethylphenyl)-1H-2-pyrazolines/pyrazoles as potential anti-inflammatory agents

2-Pyrazolins 14a–l and pyrazoles 15a–l were designed as celecoxib analogs for the evaluation of their in vitro COX-1/COX-2 inhibitory activity and the in vivo anti-inflammatory activity. Compounds 14i, 15a, 15d and 15f were the most COX-2 selective derivatives (S.I. = 5.93, 6.08, 5.03 and 5.27 respectively) while the pyrazoline derivatives 14g and 14i exhibited the highest AI activity (ED₅₀ = 190.5 and 160.1 μmol/kg po, respectively).     

Ethyl 2-(benzylidene)-7-methyl-3-oxo-2,3-dihydro-5H-thiazolo[3,2-a]pyrimidine-6-carboxylate analogues as a new scaffold for protein kinase casein kinase 2 inhibitor

Protein kinase casein kinase 2 (PKCK2) is a constitutively active, growth factor-independent serine/threonine kinase, and changes in PKCK2 expression or its activity are reported in many cancer cells. To develop a novel PKCK2 inhibitor(s), we first performed cell-based phenotypic screening using 4000 chemicals purchased from ChemDiv chemical libraries (2000: randomly selected; 2000: kinase-biased) and performed in vitro kinase assay-based screening using hits found from the first screening. We identified compound 24 (C24)[(Z)-ethyl 5-(4-chlorophenyl)-2-(3,4-dihydroxybenzylidene)-7-methyl-3-oxo-3,5-dihydro-2H-thiazolo[3,2-a] pyrimidine-6-carboxylate] as a novel inhibitor of PKCK2 that is more potent and selective than 4,5,6,7-tetrabromobenzotriazole (TBB). In particular, compound 24 [half maximal inhibitory concentration (IC₅₀) = 0.56 μM] inhibited PKCK2 2.2-fold more efficiently than did TBB (IC₅₀ = 1.24 μM), which is quite specific toward PKCK2 with respect to ATP binding, in a panel of 31 human protein kinases. The K_i values of compound 24 and TBB for PKCK2 were 0.78 μM and 2.70 μM, respectively. Treatment of cells with compound 24 inhibited endogenous PKCK2 activity and showed anti-proliferative and pro-apoptotic effects against stomach and hepatocellular cancer cell lines more efficiently than did TBB. As expected, compound 24 also enabled tumor necrosis factor-related apoptosis inducing ligand (TRAIL)-resistant cancer cells to be sensitive toward TRAIL. In comparing the molecular docking of compound 24 bound to PKCK2α versus previously reported complexes of PKCK2 with other inhibitors, our findings suggest a new scaffold for specific PKCK2α inhibitors. Thus, compound 24 appears to be a selective, cell-permeable, potent, and novel PKCK2 inhibitor worthy of further characterization.