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.     

Design,synthesis and biological evaluation of novel pyrimidinedione derivatives as DPP-4 inhibitors

A series of novel pyrimidinedione derivatives were designed and evaluated for in vitro dipeptidyl peptidase-4 (DPP-4) inhibitory activity and in vivo anti-hyperglycemic efficacy. Among them, the representative compounds 11, 15 and 16 showed excellent inhibitory activity of DPP-4 with IC₅₀ values of 64.47?nM, 188.7?nM and 65.36?nM, respectively. Further studies revealed that compound 11 was potent in vivo hypoglycemic effect. The structure–activity relationships of these pyrimidinedione derivatives had been discussed, which would be useful for developing novel DPP-4 inhibitors as treating type 2 diabetes.     

New dipeptidyl peptidase 4 inhibitors among adamantane derivatives

Fifteen adamantane derivatives were synthesized. Preliminary evaluation of their potential as dipeptidyl peptidase 4 (DPP-4) inhibitors was performed in silico by the Microcosm informational technology, PASS system, and docking in AutoDock Vina. The DPP-4 inhibition was studied in vitro. The selectivity of action of the most active compounds was studied by the direct inhibition of human plasma DPP-4 and recombinant human DPP-8. The highest activity was found for the compounds containing a nitrogen atom in the β-position of the side chain, namely, derivatives of adamantane carboxylic acid and N-(3-adamantyl-allyl) thiourea. We demonstrated that the most active compound of the series, 3,5-dimethyladamantane 1-carboxamide, was a selective DPP-4 inhibitor with IC₅₀ 53.94 μM.     

Synthesis and biological evaluation of azobicyclo[3.3.0] octane derivatives as dipeptidyl peptidase 4 inhibitors for the treatment of type 2 diabetes

A series of novel azobicyclo[3.3.0]octane derivatives were synthesized and evaluated as dipeptidyl peptidase 4 (DPP-4) inhibitors. The effort resulted in the discovery of inhibitor 2a, which exhibited excellent efficacies in an oral glucose tolerance test. Introduction of methyl group (2j) could prolong the inhibition of serum DPP-4 activity.     

4-arylcyclohexylalanine analogs as potent, selective, and orally active inhibitors of dipeptidyl peptidase IV

A novel series of 4-arylcyclohexylalanine DPP-4 inhibitors was synthesized and tested for inhibitory activity as well as selectivity over the related proline-specific enzymes DPP-8 and DPP-9. Optimization of this series led to 28 (DPP-4 IC(50)=4.8 nM), which showed an excellent pharmacokinetic profile across several preclinical species. Evaluation of 28 in an oral glucose tolerance test demonstrated that this compound effectively reduced glucose excursion in lean mice.     

Surrogating and redirection of pyrazolo[1,5-a]pyrimidin-7(4H)-one core,a novel class of potent and selective DPP-4 inhibitors

The initial focus on characterizing novel pyrazolo[1,5-a]pyrimidin-7(4H)-one derivatives as DPP-4 inhibitors, led to a potent and selective inhibitor compound b2. This ligand exhibits potent in vitro DPP-4 inhibitory activity (IC₅₀: 80?nM), while maintaining other key cellular parameters such as high selectivity, low cytotoxicity and good cell viability. Subsequent optimization of b2 based on docking analysis and structure-based drug design knowledge resulted in d1. Compound d1 has nearly 2-fold increase of inhibitory activity (IC₅₀: 49?nM) and over 1000-fold selectivity against DPP-8 and DPP-9. Further in vivo IPGTT assays showed that compound b2 effectively reduce glucose excursion by 34% at the dose of 10?mg/kg in diabetic mice. Herein we report the optimization and design of a potent and highly selective series of pyrazolo[1,5-a]pyrimidin-7(4H)-one DPP-4 inhibitors.     

Discovery of DA-1229: a potent, long acting dipeptidyl peptidase-4 inhibitor for the treatment of type 2 diabetes

A series of β-amino amide containing substituted piperazine-2-one derivatives was synthesized and evaluated as inhibitors of dipeptidyl pepdidase-4 (DPP-4) for the treatment of type 2 diabetes. As results of intensive SAR study of the series, (R)-4-[(R)-3-amino-4-(2,4,5-trifluorophenyl)-butanoyl]-3-(t-butoxymethyl)-piperazin-2-one (DA-1229) displayed potent DPP-4 inhibition pattern in several animal models, was selected for clinical development.     

Synthesis and biological evaluation of pyrrolidine-2-carbonitrile and 4-fluoropyrrolidine-2-carbonitrile derivatives as dipeptidyl peptidase-4 inhibitors for the treatment of type 2 diabetes

A novel series of pyrrolidine-2-carbonitrile and 4-fluoropyrrolidine-2-carbonitrile derivatives was designed, synthesized, and found to act as dipeptidyl peptidase-4 (DPP-4) inhibitors. From this series of compounds, compound 17a was identified as an efficacious, safe, and selective inhibitor of DPP-4. In vivo studies in ICR and KKAy mice showed that administration of this compound resulted in decreased blood glucose in these mice after an oral glucose challenge. Compound 17a showed high DPP-4 inhibitory activity (IC₅₀ = 0.017 μM), moderate selectivity against DPP-4 (selective ratio: DPP-8/DPP-4 = 1324; DPP-9/DPP-4 = 1164), and good efficacy in oral glucose tolerance tests in ICR and KKAy mice. These in vivo anti-diabetic properties and its desirable pharmacokinetic profile in Sprague–Dawley rats demonstrate that compound 17a is a promising candidate for development as an anti-diabetic agent.     

Novel series of 3-amino-N-(4-aryl-1,1-dioxothian-4-yl)butanamides as potent and selective dipeptidyl peptidase IV inhibitors

A series of novel 3-amino-N-(4-aryl-1,1-dioxothian-4-yl)butanamides were investigated as dipeptidyl peptidase IV (DPP-4) inhibitors. Introduction of a 4-phenylthiazol-2-yl group showed highly potent DPP-4 inhibitory activity. Among various derivatives, (3R)-3-amino-N-(4-(4-phenylthiazol-2-yl)-tetrahydro-2H-thiopyran-4-yl)-4-(2,4,5-trifluorophenyl)butanamide 1,1-dioxide (30) reduced blood glucose excursion in an oral glucose tolerance test by oral administration.     

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.     

Modeling assisted rational design of novel, potent, and selective pyrrolopyrimidine DPP-4 inhibitors

Molecular modeling was used to improve potency of the cyclohexylamine series. In addition, a 3-D QSAR method was used to gain insight for reducing off-target DPP-8/9 activities. Compounds 3, 4, and 5 were synthesized and found to be potent DPP-4 inhibitors, in particular 4 and 5 are designed to be highly selective against off-target DASH enzymes while maintaining potency on DPP-4.     

Design and synthesis of 3-pyridylacetamide derivatives as dipeptidyl peptidase IV (DPP-4) inhibitors targeting a bidentate interaction with Arg125

We have previously discovered nicotinic acid derivative 1 as a structurally novel dipeptidyl peptidase IV (DPP-4) inhibitor. In this study, we obtained the X-ray co-crystal structure between nicotinic acid derivative 1 and DPP-4. From these X-ray co-crystallography results, to achieve more potent inhibitory activity, we targeted Arg125 as a potential amino acid residue because it was located near the pyridine core, and some known DPP-4 inhibitors were reported to interact with this residue. We hypothesized that the guanidino group of Arg125 could interact with two hydrogen-bond acceptors in a bidentate manner. Therefore, we designed a series of 3-pyridylacetamide derivatives possessing an additional hydrogen-bond acceptor that could have the desired bidentate interaction with Arg125. We discovered the dihydrochloride of 1-{[5-(aminomethyl)-2-methyl-4-(4-methylphenyl)-6-(2-methylpropyl)pyridin-3-yl]acetyl}-l-prolinamide (13j) to be a potent and selective DPP-4 inhibitor that could interact with the guanidino group of Arg125 in a unique bidentate 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).     

Synthesis and biological evaluation of bicyclo[3.3.0] octane derivatives as dipeptidyl peptidase 4 inhibitors for the treatment of type 2 diabetes

A series of novel bicyclo[3.3.0]octane derivatives have been synthesized and found to be dipeptidyl peptidase 4 (DPP-4) inhibitors. Compounds 10a and 10b demonstrate good efficacies in oral glucose tolerance tests.     

Discovery of new binding elements in DPP-4 inhibition and their applications in novel DPP-4 inhibitor design

Probing with tool molecules, and by modeling and X-ray crystallography the binding modes of two structurally distinct series of DPP-4 inhibitors led to the discovery of a rare aromatic fluorine H-bond and the spatial requirement for better biaryl binding in the DPP-4 enzyme active site. These newly found binding elements were successfully incorporated into novel DPP-4 inhibitors.     

Synthesis of 4-cyano- and 4-nitrophenyl 2,5-anhydro- 1,6-dithio-alpha-D-gluco- and -alpha-L-guloseptanosides carrying different substituents at C-3 and C-4

Treatment of 1,6:2,5-dianhydro-3,4-di-O-methanesulfonyl-1-thio-D-glucitol in methanol with sodium hydroxide afforded 1,6:2,5:3,4-trianhydro-1-thio-allitol, 1,4:2,5-dianhydro-6-methoxy-1-thio-D-galactitol, 1,6:2,5-dianhydro-4-O-methyl-1 -thio-D-glucitol, 1 ,6:2,5-dianhydro-3-O-methanesulfonyl-1 -thio-D-glucitol and 1 ,6:2,5-dianhydro-4-deoxy-1-thio-D-erythro-hex-3-ulose (14) in 5, 4, 28, 5.5 and 41% yield, respectively. Formation of these derivatives can be explained via a common sulfonium intermediate. Reduction of 14 with sodium borohydride and subsequent acetylation afforded 3-O-acetyl-1,6:2,5-dianhydro-4-deoxy-1-thio-D-xylo-hexitol, the absolute configuration of which was proved by X-ray crystallography. The 1,6:2,5-dianhydro-1-thio-D-hexitol derivatives in which the free OH groups were protected by acetylation, methylation or mesylation were converted by a Pummerer reaction of their sulfoxides into the corresponding 1-O-acetyl hexoseptanose derivatives which were used as donors for the glycosidation of 4-cyano- and 4-nitrobenzenethiol, respectively. The Pummerer reaction of 1,6:2,5-dianhydro-4-deoxy-3-O-methyl-1-thio-D-xylo-hexitol S-oxide gave, besides 1-O-acetyl-2,5-anhydro-3-deoxy-4-O-methyl-6-thio-alpha-L- (23) and 1-O-acetyl-2,5-anhydro-4-deoxy-3-O-methyl-6-thio-alpha-D-xylo-hexoseptanose (25), 1-O-acetyl-4-deoxy-2,6-thioanhydro-D-lyxo-hexopyranose, formed in a rearrangement reaction. The same rearrangement took place, when a mixture of 23 and 25 was used as donor in the glycosidation reaction with 4-cyanobenzenethiol, applying trimethylsilyl triflate as promoter. The oral antithrombotic activity of the obtained alpha-thioglycosides was determined in rats, using Pescador's model.     

Discovery of triazines as potent,selective and orally active PDE4 inhibitors

Expanding on HTS hit 4 afforded a series of [1,3,5]triazine derivatives as novel PDE4 inhibitors. The SAR development and optimization process with the emphasis on ligand efficiency and physicochemical properties led to the discovery of compound 44 as a potent, selective and orally active PDE4 inhibitor.     

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.     

Discovery of triazole-based uracil derivatives bearing amide moieties as novel dipeptidyl peptidase-IV inhibitors

Dipeptidyl peptidase-IV (DPP-4) is a validated target for T2DM treatment. We previously reported a novel series of triazole-based uracil derivatives bearing aliphatic carboxylic acids with potent DPP-4 inhibitory activities in vitro, but these compounds showed poor hypoglycemic effects in vivo. Herein we further optimized the triazole moiety by amidation of the carboxylic acid to improve in vivo activities. Two series of compounds 3a-f and 4a-g were designed and synthesized. By screening in DPP-4, compound 4c was identified as a potent DPP-4 inhibitor with the IC₅₀ value of 28.62 nM. Docking study revealed compound 4c has a favorable binding mode and interpreted the SAR of these analogs. DPP-8 and DPP-9 tests indicated compound 4c had excellent selectivity over DPP-8 and DPP-9. Further in vivo evaluations revealed that compound 4c showed more potent hypoglycemic activity than its corresponding carboxylic acid in ICR mice and dose-dependently reduced glucose levels in type 2 diabetic C57BL/6 mice. The overall results have shown that compound 4c could be a promising lead for further development of novel DPP-4 agents treating T2DM.