Recent approaches to medicinal chemistry and therapeutic potential of dipeptidyl peptidase-4 (DPP-4) inhibitors

Discovery of the selective and nanomolar inhibitor of DPP-4 more potent than sitagliptin by structure-guided rational design

Various therapeutic targets and approaches are commonly employed in the management of Type 2 Diabetes. These encompass diverse groups of drugs that target different mechanisms involved in glucose regulation. Inhibition of the DPP-4 enzyme has been proven an excellent target for antidiabetic drug design. Our previous work on discovering multitarget antidiabetic drugs led to the identification of a gallic acid-thiazolidinedione hybrid as a potent DPP4 inhibitor (IC50 = 36 nM). In current research, our efforts resulted in a new dihydropyrimidine-based scaffold with enhanced DPP4 inhibition potential. After virtual evaluation, the designed molecules with excellent interaction patterns and binding energy values were synthesized in the wet laboratory. The inhibition potential of synthesized compounds was assessed against the DPP-4 enzyme. Compound 46 with single digit IC50 value 2 nM exhibited 4-fold and 18-fold higher activity than Sitagliptin and our previously reported hybrid respectively. Moreover, compounds 46, 47 and 50 have shown manyfold selectivity against DPP8 and DPP9. Further pretreatment with compounds 43, 45-47 and 50 (at doses of 10 and 20 mg/kg) in OGTT conducted on rats resulted in a significant decrease in the serum glucose levels compared to the control group. In the long-term STZ-induced diabetic rats, tested compound 50 performed similarly to the reference drug. Molecular dynamics simulations and in-silico molecular docking studies were employed to elucidate the time-dependent interactions of inhibitors within the active sites of DPP4. The compounds examined in this work might serve as a possible lead in the development of effective diabetic mellitus treatments.

Design, synthesis, biological evaluation and computational studies of 4-Aminopiperidine-3, 4-dihyroquinazoline-2-uracil derivatives as promising antidiabetic agents

A novel series of 4-aminopiperidin-3,4-dihyroquinazoline-2-uracil derivatives (9a-9 L) were logically designed and synthesized as potent DPP4 inhibitors as antidiabetic agents. Chemical structure of all new compounds were confirmed by different spectroscopic methods. The designed compounds were evaluated using a MAK 203 kit as DPP4 inhibitors in comparison with Sitagliptin. The biological evaluation revealed that compound 9i bearing chloro substitution on phenyl moiety of 6-bromo quinazoline ring had promising inhibitory activity with IC50 = 9.25 ± 0.57 µM. The toxicity test of all compounds confirmed safety profile of them. Kinetic studies showed that compound 9i exhibited a competitive-type inhibition with a Ki value of 12.01 µM. Computational approach supported the rationality of our design strategy, as 9i represented appropriate binding interactions with the active sites of DPP4 target. MD simulation outputs validated the stability of ligand 9i at DPP4 active site. Also, Density functional theory (DFT) including HOMO-LUMO energies, ESP map, thermochemical parameters, and theoretical IR spectrum was employed to study the reactivity descriptors of 9i and 9a as the most and least potent compounds respectively. Based on the DFT study, compound 9i was softer and, as a result, more reactive than 9a. Taken together, our results showed the potential of 4-aminopiperidin-3,4-dihyroquinazoline-2-uracil derivatives as promising candidates for developing some novel DPP4 inhibitors for managing of type 2 diabetes.

Bis(benzimidazol-2-yl)amine-Based DPP-4 Inhibitors Potentially Suitable for Combating Diabetes and Associated Nervous System Alterations

Bis(benzimidazol-2-yl)amine scaffold is not present in dipeptidyl peptidase-4 (DPP-4) inhibitors published so far. Herein, the inhibitory potential of bis(benzimidazol-2-yl)amine derivatives against DPP-4 was evaluated. In non-competitive inhibition mode, three representatives 5, 6, and 7 inhibited DPP-4 in vitro with IC50 values below 50 μM. The assessed binding pocket of DPP-4 for these benzimidazoles includes the S2 extensive subsite's residues Phe357 and Arg358. None of the lead compounds showed cytotoxicity to human neuroblastoma SH-SY5Y cells at concentrations lower than 10 μM. None showed significant binding affinity at dopamine D2, D3, and histamine H1, H3 receptors, at concentrations lower than 10 μM, leading to preferable outcomes due to mutually opposite effects of these neurotransmitters on each other. The potential beneficial effects on dopamine synthesis and the survival of dopaminergic neurons could be mediated by DPP-4 inhibition. These effective noncompetitive DPP-4 inhibitors, with inhibitory potential better than reference diprotin A (relative inhibitory potency compared to diprotin A is 3.39 and 1.54 for compounds 7 and 5, respectively), with the absence of cytotoxicity to SH-SY5Y cells, are valuable candidates for further evaluation for the treatment of diabetes and associated disruption of neuronal homeostasis.

Exploring the dipeptidyl peptidase IV inhibitory potential of probiotic-fermented milk: An in vitro and in silico comprehensive investigation into peptides from milk of different farm animals

Bioactive peptides produced via enzymatic hydrolysis have been widely investigated for their dipeptidyl peptidase-IV (DPP-IV) inhibitory properties. However, deficit of studies on fermentation as a mean to produce DPP-IV inhibitory peptides prompted us to draw a comparative study on DPP-IV inhibitory peptides generated from cow, camel, goat, and sheep milk using probiotic fermentation. Further, peptide identification, in silico molecular interactions with DPP-IV, and ensemble docking were performed. Results obtained suggested that goat milk consistently exhibited higher hydrolysis than other milk types. Further, Pediococcus pentosaceus (PP-957) emerged as a potent probiotic, with significantly lower DPP-IV-IC50 values 0.17, 0.12, and 0.25 µg/mL protein equivalent in fermented cow, camel, and goat milk, respectively. Overall, peptides (RPPPPVAM, CHNLDELKDTR, and VLSLSQPK) exhibited strong binding affinity with binding energies of -9.31, -9.18 and -8.9 Kcal·mol-1, respectively, suggesting their potential role as DPP-IV inhibitors. Overall, this study, offers valuable information toward antidiabetic benefits of fermented milk products via inhibition of DPP-IV.

Synthesis and clinical application of representative small-molecule dipeptidyl Peptidase-4 (DPP-4) inhibitors for the treatment of type 2 diabetes mellitus (T2DM)

Diabetes mellitus is a chronic metabolic disorder characterized by high blood glucose levels, which can cause many diseases, including osteoporosis, fractures, arthritis, and foot complications. The inhibitors of dipeptidyl peptidase-4 (DPP-4), an enzyme involved in glucose metabolism regulation, are essential for managing Type 2 Diabetes Mellitus (T2DM). The inhibition of DPP-4 has become a promising treatment approach for T2DM because it can increase levels of active glucagon-like peptide-1 (GLP-1), leading to improved insulin secretion in response to glucose and reduced release of glucagon. The review commences by elucidating the role of DPP-4 in glucose homeostasis and its significance in T2DM pathophysiology. Furthermore, it presents the mechanism of action, preclinical pharmacodynamics, clinical efficacy, and toxicity profiles of small-molecule DPP-4 inhibitors across various clinical stages. This comprehensive review provides valuable insights into the synthesis and clinical application of DPP-4 inhibitors, serving as an invaluable resource for researchers, clinicians, and pharmaceutical professionals interested in diabetes therapeutics and drug development.

Protective effects and mechanisms of dapagliflozin on renal ischemia/reperfusion injury

BACKGROUND

Renal diseases have a significant negative impact on human health and the quality of life. Renal ischemia/reperfusion (I/R) injury is considered as one of the leading causes of renal dysfunction and tissue damage. Oxidative stress and inflammation are responsible for cellular apoptosis playing critical roles in renal I/R injury. Recent studies suggested that dapagliflozin-a medication used to treat Type 2 Diabetes-may exert protective effects on I/R injury in kidneys by alleviating oxidative stress and inflammation. Our study evaluated the protective effects of dapagliflozinon in renal I/R injury.

METHODS

A group of 32 male Sprague-Dawley rats were divided into four groups: 1) control group without any manipulation; 2) sham-operated control group with surgery but without I/R injury; 3) experimental group with 30-min I/R injury; and 4) therapeutic group with 30-min IR injury and dapagliflozin therapy. The fourth therapeutic group received 1 mg/kg dapagliflozin delivered once daily by oral gavage. All rats were evaluated by measurements of neutrophil gelatinase-associated lipocalin (NGAL), creatinine kinase (CR), blood urea nitrogen (BUN), kidney injury molecule-1 (KIM-1), myoglobin (MYO), creatinine kinase (CK), lactate dehydrogenase (LDH) LD, GSH, superoxide dismutase (SOD), MDA, interleukin-6 (IL-6), and tumor necrosis factor-a (TNF-a and glutathione peroxidase (GSH-Px) levels. TUNEL and flow cytometry assays evaluated apoptosis.

RESULTS

Overall, the 30-min exposure to I/R injury significantly elevated levels of NGAL, CR, BUN, CK, LDH, KIM-1, and MYO (all p < 0.05). Inflammatory cytokine levels (IL-6 and TNF-a) were also increased after I/R injury (p > 0.05). At the same time, I/R injury decreased levels of SOD and GSH-Px (p > 0.05). In contrast, administration of dapagliflozin following I/R injury reduced renal damage, enhanced antioxidant capacity, and suppressed inflammatory responses (all p > 0.05), thus improving renal function, while reducing oxidative stress status and inflammatory responses. Further investigations revealed that dapagliflozin exerted its protective effects on renal tissues by activating the phosphatidylinositol 3-kinase-protein kinase B (PI3K-AKT) signaling pathway, inhibiting cellular apoptosis, and promoting proliferation and autophagy through bone morphogenetic protein 4 (BMP4).

CONCLUSION

These findings documented that dapagliflozin protected kidneys from I/R injury suggesting its therapeutic potential.

Stereochemical insights into β-amino-N-acylhydrazones and their impact on DPP-4 inhibition

Dipeptidyl peptidase IV (DPP-4) is a key enzyme that regulates several important biological processes and it is better known to be targeted by gliptins as a modern validated approach for the management of type 2 diabetes mellitus (T2DM). However, new generations of DPP-4 inhibitors capable of controlling inflammatory processes associated with chronic complications of T2DM are still needed. In this scenario, we report here the design by molecular modelling of new β-amino-N-acylhydrazones, their racemic synthesis, chiral resolution, determination of physicochemical properties and their DPP4 inhibitory potency. Theoretical and experimental approaches allowed us to propose a preliminary SAR, as well as to identify LASSBio-2124 (6) as a new lead for DPP-4 inhibition, with good physicochemical properties, favourable eudismic ratio, scalable synthesis and anti-diabetes effect in a proof-of-concept model. These findings represent an interesting starting point for the development of a new generation of DPP-4 inhibitors, useful in the treatment of T2DM and comorbidities.

GLP-1/GIP Agonist as an Intriguing and Ultimate Remedy for Combating Alzheimer's Disease through its Supporting DPP4 Inhibitors: A Review

BACKGROUND

Alzheimer's disease (AD) is a widespread neurological illness in the elderly, which impacted about 50 million people globally in 2020. Type 2 diabetes has been identified as a risk factor. Insulin and incretins are substances that have various impacts on neurodegenerative processes. Preclinical research has shown that GLP-1 receptor agonists decrease neuroinflammation, tau phosphorylation, amyloid deposition, synaptic function, and memory formation. Phase 2 and 3 studies are now occurring in Alzheimer's disease populations. In this article, we present a detailed assessment of the therapeutic potential of GLP-1 analogues and DPP4 inhibitors in Alzheimer's disease.

AIM

This study aimed to gain insight into how GLP-1 analogues and associated antagonists of DPP4 safeguard against AD.

METHODS

This study uses terms from search engines, such as Scopus, PubMed, and Google Scholar, to explore the role, function, and treatment options of the GLP-1 analogue for AD.

RESULTS

The review suggested that GLP-1 analogues may be useful for treating AD because they have been linked to anti-inflammatory, neurotrophic, and neuroprotective characteristics. Throughout this review, we discuss the underlying causes of AD and how GLP signaling functions.

CONCLUSION

With a focus on AD, the molecular and pharmacological effects of a few GLP-1/GIP analogs, both synthetic and natural, as well as DPP4 inhibitors, have been mentioned, which are in the preclinical and clinical studies. This has been demonstrated to improve cognitive function in Alzheimer's patients.

GLP-1 Analogs, SGLT-2, and DPP-4 Inhibitors: A Triad of Hope for Alzheimer's Disease Therapy

Alzheimer's is a prevalent, progressive neurodegenerative disease marked by cognitive decline and memory loss. The disease's development involves various pathomechanisms, including amyloid-beta accumulation, neurofibrillary tangles, oxidative stress, inflammation, and mitochondrial dysfunction. Recent research suggests that antidiabetic drugs may enhance neuronal survival and cognitive function in diabetes. Given the well-documented correlation between diabetes and Alzheimer's disease and the potential shared mechanisms, this review aimed to comprehensively assess the potential of new-generation anti-diabetic drugs, such as GLP-1 analogs, SGLT-2 inhibitors, and DPP-4 inhibitors, as promising therapeutic approaches for Alzheimer's disease. This review aims to comprehensively assess the potential therapeutic applications of novel-generation antidiabetic drugs, including GLP-1 analogs, SGLT-2 inhibitors, and DPP-4 inhibitors, in the context of Alzheimer's disease. In our considered opinion, antidiabetic drugs offer a promising avenue for groundbreaking developments and have the potential to revolutionize the landscape of Alzheimer's disease treatment.

Integration of Deep Learning and Sequential Metabolism to Rapidly Screen Dipeptidyl Peptidase (DPP)-IV Inhibitors from Gardenia jasminoides Ellis

Traditional Chinese medicine (TCM) possesses unique advantages in the management of blood glucose and lipids. However, there is still a significant gap in the exploration of its pharmacologically active components. Integrated strategies encompassing deep-learning prediction models and active validation based on absorbable ingredients can greatly improve the identification rate and screening efficiency in TCM. In this study, the affinity prediction of 11,549 compounds from the traditional Chinese medicine system's pharmacology database (TCMSP) with dipeptidyl peptidase-IV (DPP-IV) based on a deep-learning model was firstly conducted. With the results, Gardenia jasminoides Ellis (GJE), a food medicine with homologous properties, was selected as a model drug. The absorbed components of GJE were subsequently identified through in vivo intestinal perfusion and oral administration. As a result, a total of 38 prototypical absorbed components of GJE were identified. These components were analyzed to determine their absorption patterns after intestinal, hepatic, and systemic metabolism. Virtual docking and DPP-IV enzyme activity experiments were further conducted to validate the inhibitory effects and potential binding sites of the common constituents of deep learning and sequential metabolism. The results showed a significant DPP-IV inhibitory activity (IC50 53 ± 0.63 μg/mL) of the iridoid glycosides' potent fractions, which is a novel finding. Genipin 1-gentiobioside was screened as a promising new DPP-IV inhibitor in GJE. These findings highlight the potential of this innovative approach for the rapid screening of active ingredients in TCM and provide insights into the molecular mechanisms underlying the anti-diabetic activity of GJE.

Development of Long-Acting Dipeptidyl Peptidase-4 Inhibitors: Structural Evolution and Long-Acting Determinants

Considerable effort has been made to achieve less frequent dosing in the development of DPP-4 inhibitors. Enthusiasm for long-acting DPP-4 inhibitors is based on the promise that such agents with less frequent dosing regimens are associated with improved patient adherence, but the rational design of long-acting DPP-4 inhibitors remains a major challenge. In this Perspective, the development of long-acting DPP-4 inhibitors is comprehensively summarized to highlight the evolution of initial lead compounds on the path toward developing long-acting DPP-4 inhibitors over nearly three decades. The determinants for long duration of action are then examined, including the nature of the target, potency, binding kinetics, crystal structures, selectivity, and preclinical and clinical pharmacokinetic and pharmacodynamic profiles. More importantly, several possible approaches for the rational design of long-acting drugs are discussed. We hope that this information will facilitate the design and development of safer and more effective long-acting DPP-4 inhibitors and other oral drugs.

[RhCp*Cl2]2-Catalyzed Indole Functionalization: Synthesis of Bioinspired Indole-Fused Polycycles

Polycyclic fused indoles are ubiquitous in natural products and pharmaceuticals due to their immense structural diversity and biological inference, making them suitable for charting broader chemical space. Indole-based polycycles continue to be fascinating as well as challenging targets for synthetic fabrication because of their characteristic structural frameworks possessing biologically intriguing compounds of both natural and synthetic origin. As a result, an assortment of new chemical processes and catalytic routes has been established to provide unified access to these skeletons in a very efficient and selective manner. Transition-metal-catalyzed processes, in particular from rhodium(III), are widely used in synthetic endeavors to increase molecular complexity efficiently. In recent years, this has resulted in significant progress in reaching molecular scaffolds with enormous biological activity based on core indole skeletons. Additionally, Rh(III)-catalyzed direct C-H functionalization and benzannulation protocols of indole moieties were one of the most alluring synthetic techniques to generate indole-fused polycyclic molecules efficiently. This review sheds light on recent developments toward synthesizing fused indoles by cascade annulation methods using Rh(III)-[RhCp*Cl2]2-catalyzed pathways, which align with the comprehensive and sophisticated developments in the field of Rh(III)-catalyzed indole functionalization. Here, we looked at a few intriguing cascade-based synthetic designs catalyzed by Rh(III) that produced elaborate frameworks inspired by indole bioactivity. The review also strongly emphasizes mechanistic insights for reaching 1-2, 2-3, and 3-4-fused indole systems, focusing on Rh(III)-catalyzed routes. With an emphasis on synthetic efficiency and product diversity, synthetic methods of chosen polycyclic carbocycles and heterocycles with at least three fused, bridged, or spiro cages are reviewed. The newly created synthesis concepts or toolkits for accessing diazepine, indol-ones, carbazoles, and benzo-indoles, as well as illustrative privileged synthetic techniques, are included in the featured collection.

Insight into Structure Activity Relationship of DPP-4 Inhibitors for Development of Antidiabetic Agents

This article sheds light on the various scaffolds that can be used in the designing and development of novel synthetic compounds to create DPP-4 inhibitors for the treatment of type 2 diabetes mellitus (T2DM). This review highlights a variety of scaffolds with high DPP-4 inhibition activity, such as pyrazolopyrimidine, tetrahydro pyridopyrimidine, uracil-based benzoic acid and esters, triazole-based, fluorophenyl-based, glycinamide, glycolamide, β-carbonyl 1,2,4-triazole, and quinazoline motifs. The article further explains that the potential of the compounds can be increased by substituting atoms such as fluorine, chlorine, and bromine. Docking of existing drugs like sitagliptin, saxagliptin, and vildagliptin was done using Maestro 12.5, and the interaction with specific residues was studied to gain a better understanding of the active sites of DPP-4. The structural activities of the various scaffolds against DPP-4 were further illustrated by their inhibitory concentration (IC50) values. Additionally, various synthesis schemes were developed to make several commercially available DPP4 inhibitors such as vildagliptin, sitagliptin and omarigliptin. In conclusion, the use of halogenated scaffolds for the development of DPP-4 inhibitors is likely to be an area of increasing interest in the future.

In Vitro Assessment Methods for Antidiabetic Peptides from Legumes: A Review

Almost 65% of the human protein supply in the world originates from plants, with legumes being one of the highest contributors, comprising between 20 and 40% of the protein supply. Bioactive peptides from various food sources including legumes have been reported to show efficacy in modulating starch digestion and glucose absorption. This paper will provide a comprehensive review on recent in vitro studies that have been performed on leguminous antidiabetic peptides, focusing on the α-amylase inhibitor, α-glucosidase inhibitor, and dipeptidyl peptidase-IV (DPP-IV) inhibitor. Variations in legume cultivars and methods affect the release of peptides. Different methods have been used, such as in sample preparation, including fermentation (t, T), germination (t), and pre-cooking; in protein extraction, alkaline extraction, isoelectric precipitation, phosphate buffer extraction, and water extraction; in protein hydrolysis enzyme types and combination, enzyme substrate ratio, pH, and time; and in enzyme inhibitory assays, positive control type and concentration, inhibitor or peptide concentration, and the unit of inhibitory activity. The categorization of the relative scale of inhibitory activities among legume samples becomes difficult because of these method differences. Peptide sequences in samples were identified by means of HPLC/MS. Software and online tools were used in bioactivity prediction and computational modelling. The identification of the types and locations of chemical interactions between the inhibitor peptides and enzymes and the type of enzyme inhibition were achieved through computational modelling and enzyme kinetic studies.

Identification, Screening, and Comprehensive Evaluation of Novel DPP-IV Inhibitory Peptides from the Tilapia Skin Gelatin Hydrolysate Produced Using Ginger Protease

PURPOSE

Inhibition of dipeptidyl peptidase-IV (DPP-IV) is an effective therapy for treating type II diabetes (T2D) that has been widely applied in clinical practice. We aimed to evaluate the DPP-IV inhibitory properties of ginger protease hydrolysate (GPH) and propose a comprehensive approach to screen and evaluate DPP-IV inhibitors.

METHODS

We evaluated the in vitro inhibitory properties of fish skin gelatin hydrolysates produced by five proteases, namely, neutral protease, alkaline protease, bromelain, papain, and ginger protease, toward DPP-IV. We screened the most potent DPP-IV inhibitory peptide (DIP) using liquid chromatography-tandem mass spectrometry (LC-MS/MS) coupled with in silico analysis. Next, surface plasmon resonance (SPR) technology was innovatively introduced to explore the interactions between DPP-IV and DIP, as well as the IC₅₀. Furthermore, we performed oral administration of DIP in rats to study its in vivo absorption.

RESULTS

GPH displayed the highest degree of hydrolysis (20.37%) and DPP-IV inhibitory activity (65.18%). A total of 292 peptides from the GPH were identified using LC-MS/MS combined with de novo sequencing. Gly-Pro-Hyp-Gly-Pro-Pro-Gly-Pro-Gly-Pro (GPXGPPGPGP) was identified as the most potent DPP-IV inhibitory peptide after in silico screening (Peptide Ranker and molecular docking). Then, the in vitro study revealed that GPXGPPGPGP had a high inhibitory effect on DPP-IV (IC₅₀: 1012.3 ± 23.3 μM) and exhibited fast kinetics with rapid binding and dissociation with DPP-IV. In vivo analysis indicated that GPXGPPGPGP was not absorbed intact but partially, in the form of dipeptides and tripeptides.

CONCLUSION

Overall, the results suggested that GPH would be a natural functional food for treating T2D and provided new ideas for searching and evaluating potential antidiabetic compounds. The obtained GPXGPPGPGP can be structurally optimized for in-depth evaluation in animal and cellular experiments.

Repurposing of existing antibiotics for the treatment of diabetes mellitus

Proline specific serine protease enzyme, dipeptidyl peptidase IV (DPP-4) has become a promising target for diabetes, as it stops glucagon-like peptide 1 (GLP-1) from becoming inactive, resulting in higher levels of active GLP-1. This lowers glucose levels by increasing insulin secretion and decreasing glucagon secretion. DPP-4 is also linked to a higher BMI and a 0.7 to 1% reduction in HbA1c. Currently available DPP-4 inhibitor drugs showed less promising anti-diabetic activity as this class associated with many side effects due to non-selectivity and therefore searching on more potent DPP-4 inhibitors are still ongoing. In our present study, we investigate the inhibition of DPP-4 through a series of antibiotic compounds which were previously reported to be used in diabetic foot infections and compared with existing DPP-4 inhibitors. To obtain this objective, three-dimensional crystal structure of DPP-4 was retrieved from the protein data bank (PDB id: 1 × 70). A systematic computational method combining molecular docking, MM-GBSA binding energy calculation, MD simulations, MM-PBSA binding free energy calculations and ADME were used to find best DPP-4 inhibitor. Molecular docking results revealed that clindamycin has a higher affinity towards the catalytic sides of DPP-4 and built solid hydrophobic and polar interactions with the amino acids involved in the binding region of DPP-4, such as S1 subsite, S2 subsite and S2 extensive subsite. MD simulations results showed clindamycin as potent virtual hit and suggested that it binds with DPP-4 in competitive manner, which virtually indicate that besides antibiotic activity clindamycin has anti-diabetic activity.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40203-021-00118-6.

Discovery of tight-binding competitive inhibitors of dipeptidyl peptidase IV

Dipeptidyl peptidase IV (DPP-IV, EC 3.4.14.5) is an abundant serine aminopeptidase that preferentially cleaves N-terminal Xaa-Pro or Xaa-Ala dipeptides from oligopeptides. Inhibitors of DPP-IV activity are used for treating type 2 diabetes mellitus and other diseases. DPP-IV is also involved in tumor progression. We identified four new non-peptide tight-binding competitive inhibitors of porcine DPP-IV by virtual screening and enzymatic assays. Molecular docking simulations supported the competitive behavior, and the selectivity of one of the compounds in the DPP-IV family. Since three of these inhibitors are also aminopeptidase N (APN) inhibitors, we tested their impact on APN+/DPP-IV+ and DPP-IV+ human tumor cells' viability. Using kinetic assays, we determined that HL-60 tumor cells express both APN and DPP-IV activities and that MDA-MB-231 tumor cells express DPP-IV activity. The inhibitors had a slight inhibitory effect on human HEK-293 cell viability but reduced the viability of APN+/DPP-IV+ and DPP-IV+ human tumor cells more potently. Remarkably, the intraperitoneal injection of these compounds inhibited DPP-IV activity in rat brain, liver, and pancreas. In silico studies suggested inhibitors binding to serum albumin contribute to blood-brain barrier crossing. The spectrum of action of some of these compounds may be useful for niche applications.

DPP-IV Inhibitory Activity of the Ethanolic Extract of Red Gedi Leaves Abelmoschus manihot L. Medic

BACKGROUND: At present, there are many drugs used to manage diabetes including dipeptidyl peptidase-4 (DPP-IV) inhibitors which target insulin secretion. Abelmoschus manihot L. Medic, an endemic species of Minahasa, Indonesia, has been used as an antidiabetic herbal medicine. AIM: In this study, we studied its metabolites activities, in silico and in vitro, as inhibitor for DPP-IV, thus regulating insulin secretion. RESULTS: Of 38 identified metabolites, when docked into the catalytic site DPP-IV, 10 showed good binding energy within range of the standard gliptin drugs, that is, hibiscetin, gossypentin, gossypetin - 3-glucoside, myricetin, myricetin 3-glucoside, alpha spinasterol, quercetin, syringaresinol, stigmasterol, and isoquercetin. Three of those ten metabolites showed Ki within standard drugs values, that is, gossypetin, alpha spinasterol, and stigmasterol. The profile of molecular dynamic simulation, total energy and root mean square deviation of those metabolites were all similar with the standard gliptin drugs and predicted good stability of the complexes. The subsequent in vitro assay determining DPP-IV activity of the red Gedi leaves extract demonstrated that indeed the extract inhibited DPP-IV activity with IC50 860.67 μg/mL. Further studies are ongoing to prove the antidiabetic properties of the whole as well as isolated single compounds of the extract in particular gossypetin, alpha spinasterol, and stigmasterol as DPP-IV inhibitors. CONCLUSION: Our in silico studies showed that the compounds of ethanolic extract of red Gedi leaves potentially serve as DPP-IV inhibitors. Based on computed binding affinity, Ki, total energy, RMSD, and stability, the most potent compounds of the extract to inhibit DPP-IV activity are probably gossypetin, alpha spinasterol, and stigmasterol.

Inhibitory Effect and Potential Mechanism of Lactobacillus plantarum YE4 against Dipeptidyl Peptidase-4

This study investigated the inhibitory effect and mechanism of 12 LAB strains isolated from Chinese fermented foods on dipeptidyl peptidase-4 (DPP-4) using the Caco-2 cell model. The results showed that the inhibitory effect of cell-free extracts (CFEs) collected from each LAB strain on DPP-4 was higher than that of the cell-free excretory supernatants. The CFEs from Lactobacillus plantarum YE4 (YE4-CFE) exhibited the strongest DPP-4 inhibitory activity (24.33% inhibition). Furthermore, YE4-CFE altered the TNF and MAPK signaling pathways. Additionally, the YE4-CFE ultrafiltration fraction (<3 kDa) displayed a similar DPP-4 inhibitory activity to YE4-CFE. UHPLC-MS/MS identified 19 compounds with a relative proportion of more than 1% in the <3 kDa fraction, and adenine, acetylcholine, and L-phenylalanine were the top three substances in terms of proportion. Altogether, the inhibitory effect of YE4-CFE on DPP-4 was associated with the TNF and MAPK signaling pathways, and with the high proportion of adenine, acetylcholine, and L-phenylalanine.

Virtual screening of dipeptidyl peptidase-4 inhibitors using quantitative structure-activity relationship-based artificial intelligence and molecular docking of hit compounds

Dipeptidyl peptidase-4 (DPP-4) inhibitors are becoming an essential drug in the treatment of type 2 diabetes mellitus; however, some classes of these drugs exert side effects, including joint pain and pancreatitis. Studies suggest that these side effects might be related to secondary inhibition of DPP-8 and DPP-9. In this study, we identified DPP-4-inhibitor hit compounds selective against DPP-8 and DPP-9. We built a virtual screening workflow using a quantitative structure-activity relationship (QSAR) strategy based on artificial intelligence to allow faster screening of millions of molecules for the DPP-4 target relative to other screening methods. Five regression machine learning algorithms and four classification machine learning algorithms were applied to build virtual screening workflows, with the QSAR model applied using support vector regression (R²_pred 0.78) and the classification QSAR model using the random forest algorithm with 92.2% accuracy. Virtual screening results of > 10 million molecules obtained 2 716 hits compounds with a pIC₅₀ value of > 7.5. Additionally, molecular docking results of several potential hit compounds for DPP-4, DPP-8, and DPP-9 identified CH0002 as showing high inhibitory potential against DPP-4 and low inhibitory potential for DPP-8 and DPP-9 enzymes. These results demonstrated the effectiveness of this technique for identifying DPP-4-inhibitor hit compounds selective for DPP-4 and against DPP-8 and DPP-9 and suggest its potential efficacy for applications to discover hit compounds of other targets.

Pleiotropic Benefits of DPP-4 Inhibitors Beyond Glycemic Control

Dipeptidyl peptidase (DPP)-4 inhibitors are oral anti-diabetic medications that block the activity of the ubiquitous enzyme DPP-4. Inhibition of this enzyme increases the level of circulating active glucagon-like peptide (GLP)-1 secreted from L-cells in the small intestine. GLP-1 increases the glucose level, dependent on insulin secretion from pancreatic β-cells; it also decreases the abnormally increased level of glucagon, eventually decreasing the blood glucose level in patients with type 2 diabetes. DPP-4 is involved in many physiological processes other than the degradation of GLP-1. Therefore, the inhibition of DPP-4 may have numerous effects beyond glucose control. In this article, we review the pleiotropic effects of DPP-4 inhibitors beyond glucose control, including their strong beneficial effects on the stress induced accelerated senescence of vascular cells, and the possible clinical implications of these effects.

In silico analysis of novel dipeptidyl peptidase-IV inhibitory peptides released from Macadamia integrifolia antimicrobial protein 2 (MiAMP2) and the possible pathways involved in diabetes protection

The aim of the present study was to screen novel dipeptidyl peptidase IV (DPP-IV) inhibitory peptides from Macadamia integrifolia antimicrobial protein 2 (MiAMP2) and evaluate the potential antidiabetic targets and involved signaling pathways using in silico approaches. In silico digestion of MiAMP2 with pepsin, trypsin and chymotrypsin was performed with ExPASy PeptideCutter and the generated peptides were subjected to BIOPEP-UWM, iDrug, INNOVAGEN and Autodock Vina for further analyses. Six novel peptides EQVR, EQVK, AESE, EEDNK, EECK, and EVEE were predicted to possess good DPP-IV inhibitory potentials, water solubility, and absorption, distribution, metabolism, excretion, and toxicity properties. Molecular dynamic simulation and molecular docking displayed that AESE was the most potent DPP-IV inhibitory peptide and can bind with the active sites of DPP-IV through hydrogen bonding and van der Waals forces. The potential antidiabetic targets of AESE were retrieved from SwissTargetPrediction and GeneCards databases. Protein-protein interaction analysis identified BIRC2, CASP3, MMP7 and BIRC3 to be the hub targets. Moreover, the KEGG pathway enrichment analysis showed that AESE prevented diabetes through the apoptosis and TNF signaling pathways. These results will provide new insights into utilization of MiAMP2 as functional food ingredients for the prevention and treatment of diabetes.

Structure-Activity Relationship Analysis of Cocrystallized Gliptin-like Pyrrolidine, Trifluorophenyl, and Pyrimidine-2,4-Dione Dipeptidyl Peptidase-4 Inhibitors

Approved and potent reported dipeptidyl peptidase-4 (DPP-4) inhibitors with gliptin-like structures are classified here according to their structures and mechanisms of the inhibition in three groups: (i) those with pyrrolidine or analogs as P1 fragment with α-aminoacyl linker, (ii) structures with trifluorophenyl moiety or analogs as P1 fragment with β-aminobutanoyl linker, and (iii) DPP-4 inhibitors with pyrimidine-2,4-dione or analogs as P1' fragment. The structure-activity relationship analysis was performed for those whose cocrystallized structures with the enzyme were published. While inhibitors with pyrrolidine and trifluorophenyl moiety or analogs as P1 fragment bind in a similar way in S1, S2 and S2 extensive domains of the enzyme, the binding mode of pyrimidine-2,4-dione derivatives/analogs differs with additional interactions in S1' and S2' pockets. Three general schemes of fragmented gliptins and gliptin-like structures with the enzyme and protein-ligand interaction fingerprints were made, which might be useful in the creation of DPP-4 inhibitor's design strategies.

Characterization of peptides with antioxidant activity and antidiabetic potential obtained from chickpea (Cicer arietinum L.) protein hydrolyzates

Alcalase hydrolyzates were prepared from the albumin (AH) and globulin (GH) fractions of eight chickpea (Cicer arietinum L.) genotypes from Mexico and 10 from other countries. Protein content, antioxidant activity (AA) (ABTS, DPPH), and degree of hydrolysis were evaluated and the best genotype was selected by principal component analysis. The hydrolyzates of the chosen genotype were analyzed for its antidiabetic potential measured as inhibition of α-amylase, α-glucosidase, and dipeptidyl peptidase-4 (DPP4). Peptide profiles were obtained by liquid chromatography-mass spectrometry (UPLC-DAD-MS), and the most active peptides were analyzed by molecular docking. The average antioxidant activity of albumin hydrolyzates was higher than that of globulin hydrolyzates. ICC3761 was the selected genotype and peptides purified from the albumin hydrolyzate showed the best antioxidant activity and antidiabetic potential (FEI, FEL, FIE, FKN, FGKG, and MEE). FEI, FEL, and FIE were in the same chromatographic peak and this mixture showed the best ABTS scavenging (78.25%) and DPP4 inhibition (IC₅₀  = 4.20 µg/ml). MEE showed the best DPPH scavenging (47%). FGKG showed the best inhibition of α-amylase (54%) and α-glucosidase (56%) and may be a competitive inhibitor based on in silico-predicted interactions with catalytic amino acids in the active site of both enzymes. These peptides could be used as nutraceutical supplements against diseases related to oxidative stress and diabetes. PRACTICAL APPLICATION: This study showed that chickpea protein hydrolyzates are good sources of peptides with antidiabetic potential, showing high antioxidant activity and inhibition of enzymes related to carbohydrate metabolism and type 2 diabetes. These hydrolyzates could be formulated in functional foods for diabetes.

Deciphering the Neuroprotective Role of Glucagon-like Peptide-1 Agonists in Diabetic Neuropathy: Current Perspective and Future Directions

Diabetic neuropathy is referred to as a subsequential and debilitating complication belonging to type 1 and type 2 diabetes mellitus. It is a heterogeneous group of disorders with a particularly complex pathophysiology and also includes multiple forms, ranging from normal discomfort to death. The evaluation of diabetic neuropathy is associated with hyperglycemic responses, resulting in an alteration in various metabolic pathways, including protein kinase C pathway, polyol pathway and hexosamine pathway in Schwann and glial cells of neurons. The essential source of neuronal destruction is analogous to these respective metabolic pathways, thus identified as potential therapeutic targets. These pathways regulating therapeutic medications may be used for diabetic neuropathy, however, only target specific drugs could have partial therapeutic activity. Various antidiabetic medications have been approved and marketed, which possess the therapeutic ability to control hyperglycemia and ameliorate the prevalence of diabetic neuropathy. Among all antidiabetic medications, incretin therapy, including Glucagon-like peptide-1 receptor agonists and dipeptidyl peptidase-4 inhibitors, are the most favorable medications for the management of diabetes mellitus and associated peripheral neuropathic complications. Besides enhancing glucose-evoked insulin release from pancreatic β-cells, these therapeutic agents also play a vital role to facilitate neurite outgrowth and nerve conduction velocity in dorsal root ganglion. Furthermore, incretin therapy also activates cAMP and ERK signalling pathways, resulting in nerve regeneration and repairing. These effects are evidently supported by a series of preclinical data and investigations associated with these medications. However, the literature lacks adequate clinical trial outcomes related to these novel antidiabetic medications. The manuscript emphasizes the pathogenesis, current pharmacological approaches and vivid description of preclinical and clinical data for the effective management of diabetic neuropathy.

Pyrazole Incorporated New Thiosemicarbazones: Design, Synthesis and Investigation of DPP-4 Inhibitory Effects

Dipeptidyl peptidase-4 (DPP-4) inhibition has been recognized as a promising approach to develop safe and potent antidiabetic agents for the management of type 2 diabetes. In this context, new thiosemicarbazones (2a-o) were prepared efficiently by the reaction of aromatic aldehydes with 4-[4-(1H-pyrazol-1-yl)phenyl]thiosemicarbazide (1), which was obtained via the reaction of 4-(1H-pyrazol-1-yl)phenyl isothiocyanate with hydrazine hydrate. Compounds 2a-o were evaluated for their DPP-4 inhibitory effects based on a convenient fluorescence-based assay. 4-[4-(1H-pyrazol-1-yl)phenyl]-1-(4-bromobenzylidene)thiosemicarbazide (2f) was identified as the most effective DPP-4 inhibitor in this series with an IC₅₀ value of 1.266 ± 0.264 nM when compared with sitagliptin (IC₅₀ = 4.380 ± 0.319 nM). MTT test was carried out to assess the cytotoxic effects of compounds 2a-o on NIH/3T3 mouse embryonic fibroblast (normal) cell line. According to cytotoxicity assay, compound 2f showed cytotoxicity towards NIH/3T3 cell line with an IC₅₀ value higher than 500 µM pointing out its favourable safety profile. Molecular docking studies indicated that compound 2f presented π-π interactions with Arg358 and Tyr666 via pyrazole scaffold and 4-bromophenyl substituent, respectively. Overall, in vitro and in silico studies put emphasis on that compound 2f attracts a great notice as a drug-like DPP-4 inhibitor for further antidiabetic research.

Discovery of dipeptidyl peptidase 4 inhibitory peptides from Largemouth bass (Micropterus salmoides) by a comprehensive approach

Dipeptidyl peptidase-4 (DPP4) is the prime target for glycemic control by inactivating glucagon-like peptide and decreasing postprandial glucose levels. Food protein-derived peptides have been considered to be capable of inhibiting DPP4. In this study, a novel strategy was developed by coupling in silico gastrointestinal digestion, pharmacophore and three-dimensional quantitative structure-activity relationships (3D-QSAR) analysis to discover DPP4 inhibitory peptide, and in vitro assay was confirmed. Specifically, the simulated gastrointestinal hydrolysis was firstly performed on Largemouth bass (Micropterus salmoides) proteins, the generated peptides were used to establish peptide library. Secondly, 60 DPP4 inhibitors were selected and pharmacophore model was generated; moreover, 40 DPP4 inhibitory tripeptides were collected to construct 3D-QSAR model. Thirdly, the pharmacophore and 3D-QSAR models were employed to screen the above peptide library. Lastly, the in vitro activity assay was performed, which showed that the six tripeptides (VSM, ISW, VSW, ICY, ISD and ISE) exhibited inhibitory activities on DPP4, and ICY was the most active tripeptide with the IC₅₀ value of 0.73 mM. This is the first identification of Largemouth bass protein-derived peptides as DPP4 inhibitor, which is good for the development of food protein-derived peptides with glucose lowering activity.

Molecular dynamics simulation and free energy calculation studies of Coagulin L as dipeptidyl peptidase-4 inhibitor

Plant derived product can be used as other alternatives to currently used drugs for controlling chronic diseases like Diabetes mellitus. The potential of Coagulin L (a constituent of Withania coagulans) as dipeptidyl peptidase-4 (DPP-4) inhibitor was evaluated by molecular modelling study. It was observed that amino acid residues such as Glu205, Glu206, Tyr 547, His 740, and Try662 interacts with Coagulin L and Saxagliptin (a known DPP-4 inhibitor). Other nonbonded interactions of Coagulin L and Saxagliptin with DPP-4 binding residues were also found similar. The docking energy of Coagulin L was found to be -7.69 Kcal/mol whereas -8.44 kcal/mol was recorded for Saxagliptin. MD simulation study revealed stable binding throughout 100 ns simulation. RMSD plot of the complex was stabilized in 43 ns and remained stable during entire simulation(100 ns). RMSF plot of DPP-4 Coagulin L interaction showed major fluctuations at residue 246 and 766, however, Arg 125, Glu 205, Ser 209 and His 740 showed no major perturbations. Principal Component Analysis showed that important dynamics of the protein remain unchanged during entire simulation since the non-polar, van der waals, ionic interaction and solvation energy, altogether play important role in the complex stability. The molecular modelling study of DPP-4 with Coagulin L was an effort to establish correlation with traditional practices of Withania coagulans as antidiabetic agent in Indian subcontinent.Communicated by Ramaswamy H. Sarma.

Can dipeptidyl peptidase-4 inhibitors treat cognitive disorders?

The linkage of neurodegenerative diseases with insulin resistance (IR) and type 2 diabetes mellitus (T2DM), including oxidative stress, mitochondrial dysfunction, excessive inflammatory responses and abnormal protein processing, and the correlation between cerebrovascular diseases and hyperglycemia has opened a new window for novel therapeutics for these cognitive disorders. Various antidiabetic agents have been studied for their potential treatment of cognitive disorders, among which the dipeptidyl peptidase-4 (DPP-4) inhibitors have been investigated more recently. So far, DPP-4 inhibitors have demonstrated neuroprotection and cognitive improvements in animal models, and cognitive benefits in diabetic patients with or without cognitive impairments. This review aims to summarize the potential mechanisms, advantages and limitations, and currently available evidence for developing DPP-4 inhibitors as a treatment of cognitive disorders.

Drug discovery approaches targeting the incretin pathway

Incretin pathway plays an important role in the development of diabetes medications. Interventions in DPP-4 and GLP-1 receptor have shown remarkable efficacy in experimental and clinical studies and imperatively become one of the most promising therapeutic approaches in the T2DM drug discovery pipeline. Herein, we analyzed the actionmechanismsof DPP-4 and GLP-1 receptor targeting the incretin pathway in T2DM treatment. We gave an insight into the structural requirements for the potent DPP-4 inhibitors and revealed a classification of DPP-4 inhibitors by stressing on the binding modes of these ligands to the enzyme. We then reviewed the drug discovery strategies for the development of peptide and non-peptide GLP-1 receptor agonists (GLP-1 RAs). Furthermore, the drug design strategies for DPP-4 inhibitors and GLP-1R agonists were detailed accurately. This review might provide an efficient evidence for the highly potent and selective DPP-4 inhibitors and the GLP-1 RAs, as novel medicines for patients suffering from T2DM.

Extraction and characterization of novel multifunctional peptides from Trachinus Draco (greater weever) myofibrillar proteins with ACE/DPP4 inhibitory, antioxidant, and metal chelating activities

Marine organisms represent a great source of natural bioactive molecules, from which bioactive peptides are of great importance in biomedicine application in many diseases such as diabetes and its related complications. In this study, greater weever (Trachinus Draco) myofibrillar proteins were sequentially hydrolyzed and the different RP-HPLC purified fractions were tested for potential inhibitory activities of ACE and DPP4, in addition to metal chelation and antioxidant activities. Four fractions were found to have high levels of activity (with two peptides being multifunctional) and were subsequently sequenced using the de novo sequencing method. The results indicate that the peptides are novel and highly effective for each related activity compared to reference molecules. The current findings suggest these multifunctional peptides as promising therapeutics against oxidative stress, hypertension, and diabetes. PRACTICAL APPLICATIONS: We have described the finding of two multifunctional bioactive peptides from Trachinus Draco (greater weever) myofibrillar proteins having two or more activities. They have ACE inhibitory, DPP4 inhibitory, antioxidant, and metal chelation activities. These new peptides could be used for future biomedicine applications as a stand-alone treatment, in combination with other molecules, or as a supplement. Furthermore, after identification of their sequence in our work, it would have a great potential to be artificially synthesized. The field of food supplements could be explored further.

Comparison of persistence and adherence between DPP-4 inhibitor administration frequencies in patients with type 2 diabetes mellitus in Japan: a claims-based cohort study

Objective: To explore persistence and adherence with once-daily, twice-daily, or once-weekly DPP-4 inhibitors (DPP-4i) in Japanese patients with type 2 diabetes.Methods: This retrospective, longitudinal, observational cohort study used data from the Japanese nationwide hospital-based Medical Data Vision (MDV) administrative claims database. Data were collected for patients given a new DPP-4i prescription between May 2015 and June 2017 with 1-year follow-up until May 2018. Treatment persistence was defined as the total duration of continuous prescription. Adherence to treatment was measured as the proportion of days covered (PDC).Results: A total of 598,419 patients with a prescription for DPP-4i treatment were identified in the MDV database. Of the 39,826 patients who met the inclusion criteria, 82.4% were receiving once-daily DPP-4i, 15.6% twice-daily DPP-4i, and 2.0% once-weekly DPP-4i. Twelve-month persistence rates with once-daily regimens were 66.3% versus 64.7% with twice-daily (p = .1187), and versus 38.8% with once-weekly, regimens (p < .0001) in the overall population (including untreated [UT] and previously treated [PT] patients); 62.8% with once-daily versus 58.3% with twice-daily (p = .0309), and versus 12.3% with once-weekly regimens (p < .0001) in the UT cohort; and 68.6% with once-daily versus 67.9% with twice-daily (p = .5471), and versus 49.1% with once-weekly regimens (p < .0001) in the PT cohort. In the overall population, 97.8% of patients had a mean PDC of 0.97 with once- and twice-daily, and 65.8% of patients had a mean PDC of 0.74 with once-weekly, DPP-4i regimens.Conclusions: Overall, persistence at 12 months was highest in patients receiving once-daily DPP-4i regimens.

Treatment preference for weekly versus daily DPP-4 inhibitors in patients with type 2 diabetes mellitus: outcomes from the TRINITY trial

Objective: To examine patient preference for treatment with the oral once-weekly dipeptidyl peptidase-4 inhibitor (DPP-4i), trelagliptin, and oral once-daily DPP-4i, alogliptin, administered for 8 weeks each in patients with type 2 diabetes mellitus prescribed a daily DPP-4i.Methods: In this randomized, open-label, two-way crossover study, patients received trelagliptin followed by alogliptin (T-A group) or alogliptin followed by trelagliptin (A-T group), for 8 weeks each (NCT03231709, JapicCTI-173662). Treatment preference was assessed using a standardized questionnaire in the overall population and by baseline characteristics. Other outcomes included patient satisfaction with diabetes treatment (assessed using the Diabetes Treatment Satisfaction Questionnaire [DTSQ]), hemoglobin A1c (HbA1c) levels after 8 weeks of treatment with each agent, and safety.Results: Sixty patients from two clinical sites were randomized 1:1 to T-A and A-T groups (each n = 30); baseline characteristics were similar between groups. After 16 weeks of treatment, 51.7% of patients preferred treatment with alogliptin compared with 30.0% selecting trelagliptin (p = .014); preference for alogliptin was consistently greater than for trelagliptin in the secondary analyses by baseline characteristics. DTSQ score and HbA1c levels were similar between treatments after 8 weeks of therapy. Both treatments demonstrated favorable safety and tolerability profiles.Conclusions: Patients expressed a significantly greater treatment preference for once-daily alogliptin than once-weekly trelagliptin, although patient satisfaction and HbA1c levels were similar across treatments. The decision to administer a once-weekly or once-daily DPP-4i is likely to depend on patient preference, patient-physician discussions, and treatment practices of the prescribing physician.

Benzo[4,5]thieno[2,3-d]pyrimidine phthalimide derivative, one of the rare noncompetitive inhibitors of dipeptidyl peptidase-4

A small library of benzo[4,5]thieno[2,3-d]pyrimidine phthalimide and amine derivatives was evaluated for inhibitory activity against dipeptidyl peptidase-4 (DPP-4). The phthalimide derivatives exhibited better activity than the amine precursors, with 2-(2-(3-chlorobenzyl)-5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidin-4-yl)isoindoline-1,3-dione (compound 14) as the most effective inhibitor (IC₅₀  = 34.17 ± 5.11 μM). The five most potent selected inhibitors did not show cytotoxicity to a greater extent on Caco-2 cells, even at a concentration of 250 μM. Compound 14 is considered as a novel representative of the rare noncompetitive DPP-4 inhibitors. Molecular docking and dynamics simulation indicated the importance of the Tyr547, Lys554, and Trp629 residues of DPP-4 in the formation of the enzyme-inhibitor complex. These observations could be potentially utilized for the rational design and optimization of novel (structurally similar, with phthalimide moiety, or different) noncompetitive DPP-4 inhibitors, which are anyway rare, but favorable in terms of the saturation of substrate competition.

A Randomized Pilot Study of the Effect of Trelagliptin and Alogliptin on Glycemic Variability in Patients with Type 2 Diabetes

INTRODUCTION

This open-label, parallel-group, exploratory study examined the effects of two dipeptidyl peptidase 4 (DPP4) inhibitors on glycemic variability (GV) in patients with type 2 diabetes.

METHODS

Randomized patients with glycated hemoglobin A1c of at least 6.5% to less than 8.5% received trelagliptin 100 mg (n = 13) once weekly or alogliptin 25 mg (n = 14) once daily for 29 days. Continuous glucose monitoring was performed before the start of the treatment period (baseline) and from day 21 to 29, inclusive. The primary endpoint was change from baseline in the standard deviation (SD) of 24-h blood glucose values, measured daily for 7 days (day 22-28) of the treatment period. Secondary and additional efficacy endpoints included changes in glycemic parameters and the rate of DPP4 inhibition, respectively. Adverse events (AEs) were monitored to assess safety.

RESULTS

Mean change from baseline in the SD of 24-h blood glucose (95% confidence interval) at day 28 was - 7.35 (- 15.13, 0.44) for trelagliptin and - 11.63 (- 18.67, - 4.59) for alogliptin. In both treatment groups, glycemic parameters improved and the rate of DPP4 inhibition was maintained. Three patients reported AEs; no severe treatment-emergent AEs were reported in either group.

CONCLUSION

Once-weekly trelagliptin and once-daily alogliptin improved glycemic control and reduced GV without inducing hypoglycemia.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT02771093) and JAPIC (JapicCTI-163250).

FUNDING

Takeda Pharmaceutical Company, Ltd.

Optimization of the benzamide fragment targeting the S2' site leads to potent dipeptidyl peptidase-IV inhibitors

Our recently successful identification of benzoic acid-based DPP-4 inhibitors spurs the further quest for in-depth structure-activity relationships (SAR) study in S₂' site DPP-4. Thus novel benzamide fragments were designed to target the S₂' site to compromise lipophilicity and improve oral activity. Exploring SAR by introduction of a variety of amide and halogen on benzene ring led to identification of several compounds, exerting moderated to excellent DPP-4 activities, in which 4'-chlorine substituted methyl amide 17g showed most potent DPP-4 activity with the IC₅₀ value of 1.6 nM. Its activity was superior to reference alogliptin. Docking study ideally verified and interpreted the obtained SAR of designed compounds. As a continuation, DPP-8/9 assays revealed the designed compounds exhibited good selectivity over DPP-8 and DPP-9. Subsequent cell-based test indicated compound 17g displayed low toxicity toward the LO2 cell line up to 100 μM. In vivo evaluation showed compound 17g robustly improved the glucose tolerance in normal mice. Importantly, 17g exhibited reasonable pharmacokinetic (PK) profiles for oral delivery. Overall, compound 17g has the potential to a safe and efficacious DPP-4 inhibitor for T2DM treatment.

Randomized Multicenter Evaluation of Quality of Life and Treatment Satisfaction in Type 2 Diabetes Patients Receiving Once-Weekly Trelagliptin Versus a Daily Dipeptidyl Peptidase-4 Inhibitor

INTRODUCTION

Dipeptidyl peptidase-4 (DPP-4) inhibitors are an established treatment in type 2 diabetes mellitus (T2DM). The objective of this study was to investigate differences in quality of life (QOL) and treatment satisfaction among treatment-naïve T2DM patients receiving once-weekly trelagliptin or a daily DPP-4 inhibitor.

METHODS

In this multicenter, randomized, open-label, parallel-group, phase IV study conducted in Japan, 218 patients were randomized to trelagliptin 100 mg once weekly or a once- or twice-daily DPP-4 inhibitor for 12 weeks (NCT03014479; JapicCTI-173482). QOL and treatment satisfaction were assessed using the Diabetes Therapy-Related QOL (DTR-QOL) Questionnaire and Diabetes Treatment Satisfaction Questionnaire (DTSQ), respectively. The primary endpoint was change from baseline in DTR-QOL total score at week 12. Secondary endpoints included further analysis of the DTR-QOL and DTSQ components. Other endpoints included glycemic control, treatment adherence, and safety.

RESULTS

The between-group difference in the change from baseline to week 12 in DTR-QOL total score was 2.418 (95% confidence interval - 1.546, 6.382; P = 0.2305). Analysis of the DTR-QOL and DTSQ results by subscales and stratification generally showed a numerical improvement with trelagliptin over daily DPP-4 inhibitors. QOL and treatment satisfaction improved with a reduction in frequency of concurrent and study drug dosing. Treatment adherence was > 97% for both groups. The effect of trelagliptin on glycemic control was similar to that seen with daily DPP-4 inhibitors. Trelagliptin and daily DPP-4 inhibitors were well-tolerated and demonstrated similar safety profiles.

CONCLUSIONS

Once-weekly trelagliptin 100 mg administered for 12 weeks resulted in a numerically, but not statistically, greater improvement in QOL and treatment satisfaction versus daily DPP-4 inhibitors. The decision to administer once-weekly or daily DPP-4 inhibitor treatment is likely to depend on patient preferences and the treatment policies of physicians.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT03014479) and JAPIC (JapicCTI-173482).

FUNDING

Takeda Pharmaceutical Company Ltd.

Mining large databases to find new leads with low similarity to known actives: application to find new DPP-IV inhibitors

Aim: Fragment-based drug design or bioisosteric replacement is used to find new actives with low (or no) similarity to existing ones but requires the synthesis of nonexisting compounds to prove their predicted bioactivity. Protein-ligand docking or pharmacophore screening are alternatives but they can become computationally expensive when applied to very large databases such as ZINC. Therefore, fast strategies are necessary to find new leads in such databases. Materials & methods: We designed a computational strategy to find lead molecules with very low (or no) similarity to existing actives and applied it to DPP-IV. Results: The bioactivity assays confirm that this strategy finds new leads for DPP-IV inhibitors. Conclusion: This computational strategy reduces the time of finding new lead molecules.

Design, Synthesis and Biological Evaluation of Spiro Cyclohexane-1,2- Quinazoline Derivatives as Potent Dipeptidyl Peptidase IV Inhibitors

OBJECTIVE

Inhibition of dipeptidyl peptidase IV (DPP-4) is currently one of the most valuable and potential chemotherapeutic regimes for the medication of Type 2 Diabetes Mellitus (T2DM).

METHOD

Based on linagliptin, this study discusses the design, synthesis and biological evaluation of spiro cyclohexane-1,2'-quinazoline scaffold hybridized with various heterocyclic ring systems through different atomic spacers as a highly potent DPP-4 inhibitors. DPP-4 enzyme assay represented that most of the target compounds are 102-103 folds more active than the reference drug linagliptin (IC50: 0.0005-0.0089 nM vs 0.77 nM; respectively). Moreover, in vivo oral hypoglycemic activity assay revealed that most of the tested candidates were more potent than the reference drug, sitagliptin, producing rapid onset with long duration of activity that extends to 24 h. Interestingly, the derivatives 11, 16, 18a and 23 showed evidence of mild cytochrome P450 3A4 (CYP3A4) inhibition (IC50; > 210 µM) and their acute toxicity (LD50) was more than 1.9 gm/kg. Molecular simulation study of the new quinazoline derivatives explained the obtained biological results.

CONCLUSION

Finally, we conclude that our target compounds could be highly beneficial for diabetic patients in the clinic.

Identification of novel uracil derivatives incorporating benzoic acid moieties as highly potent Dipeptidyl Peptidase-IV inhibitors

Dipeptidyl Peptidase-IV (DPP-4) is a validated therapeutic target for type 2 diabetes. Aiming to interact with both residues Try629 and Lys554 in S₂' site, a series of novel uracil derivatives 1a-l and 2a-i incorporating benzoic acid moieties at the N₃ position were designed and evaluated for their DPP-4 inhibitory activity. Structure-activity relationships (SAR) study led to the identification of the optimal compound 2b as a potent and selective DPP-4 inhibitor (IC₅₀ = 1.7 nM). Docking study revealed the additional salt bridge formed between the carboxylic acid and primary amine of Lys554 has a key role in the enhancement of the activity. Furthermore, compound 2b exhibited no cytotoxicity in human hepatocyte LO2 cells up to 50 μM. Subsequent in vivo evaluations revealed that the ester of 2b robustly improves the glucose tolerance in normal mice. The overall results have shown that compound 2b has the potential to a safe and efficacious treatment for T2DM.

One-pot construction of diverse and functionalized isochromenoquinolinediones by Rh(iii)-catalyzed annulation of unprotected arylamides with 3-diazoquinolinediones and their application for fluorescence sensor

A facile and efficient Rh(iii)-catalyzed annulation of arylamides with 3-diazoquinolinediones for the construction of diverse and highly functionalized isochromenoquinolinediones is described. Furthermore, the methodology is applicable for delivering various relevant molecules such as pyridopyranoquinolindiones, thienopyranoquinolinones, and indolopyranoquinolinone. The reaction proceeds via cascade C–H activation, carbene insertion, and intramolecular lactonization. The reaction exhibits high atom economy, good functional group tolerance, and high regioselectivity. The synthesized compound can also behave as a potent fluorescence sensor for Fe³⁺ ion.

An efficient Rh(iii)-catalyzed annulation of arylamides with 3-diazoquinolinediones for the construction of diverse and highly functionalized isochromenoquinolinedione derivatives is described.

Clinical Use of DPP-4 Inhibitors

DPP-4 inhibitors were introduced for the treatment of type 2 diabetes in 2006. They stimulate insulin secretion and inhibit glucagon secretion by elevating endogenous GLP-1 concentrations without an intrinsic hypoglycaemia risk. Their efficacy potential to lower HbA1c is in the range between 0.5 and 1.0% and their safety profile is favorable. DPP-4 inhibitors are body weight neutral and they have demonstrated cardiovascular safety. Most compounds can be used in impaired renal function. Guidelines suggest the additional use of DPP-4 inhibitors after metformin failure in patients that do not require antidiabetic therapy with proven cardiovascular benefit. Recently, DPP-4 inhibitors have increasingly replaced sulfonylureas as second line therapy after metformin failure and many metformin/DPP-4 inhibitor fixed dose combinations are available. In later stages of type 2 diabetes, DPP-4 inhibitors are also recommended in the guidelines in triple therapies with metformin and SGLT-2 inhibitors or with metformin and insulin. A treatment with DPP-4 inhibitors should be stopped when GLP-1 receptor agonists are used. DPP-4 inhibitors can be used as monotherapy when metformin is contraindicated or not tolerated. Some studies have shown value of initial metformin-DPP-4 inhibitor combination therapy in special populations. This article gives an overview on the clinical use of DPP-4 inhibitors.

Plant dipeptidyl peptidase-IV inhibitors as antidiabetic agents: a brief review

Diabetes mellitus is an increasing public health problem in the world. Type 2 diabetes is the most common type of diabetes whose complications contribute to its high death rate. It seriously impacts healthcare systems and patients' quality of life. Therefore, effective measures and new treatment strategies are needed to solve this increasingly serious global problem. In recent years, inhibition of dipeptidyl peptidase IV (DPP-IV) has emerged as a new treatment option for Type 2 diabetes. This article reviews various plant DPP-IV inhibitors that showed inhibition toward enzyme as a major target for the management of Type 2 diabetes. These studies can contribute to the future development of DPP-IV inhibitors as drugs.

Activity and selectivity cliffs for DPP-IV inhibitors: Lessons we can learn from SAR studies and their application to virtual screening

The inhibition of dipeptidyl peptidase-IV (DPP-IV) has emerged over the last decade as one of the most effective treatments for type 2 diabetes mellitus, and consequently (a) 11 DPP-IV inhibitors have been on the market since 2006 (three in 2015), and (b) 74 noncovalent complexes involving human DPP-IV and drug-like inhibitors are available at the Protein Data Bank (PDB). The present review aims to (a) explain the most important activity cliffs for DPP-IV noncovalent inhibition according to the binding site structure of DPP-IV, (b) explain the most important selectivity cliffs for DPP-IV noncovalent inhibition in comparison with other related enzymes (i.e., DPP8 and DPP9), and (c) use the information deriving from this activity/selectivity cliff analysis to suggest how virtual screening protocols might be improved to favor the early identification of potent and selective DPP-IV inhibitors in molecular databases (because they have not succeeded in identifying selective DPP-IV inhibitors with IC₅₀ ≤ 100 nM). All these goals are achieved with the help of available homology models for DPP8 and DPP9 and an analysis of the structure-activity studies used to develop the noncovalent inhibitors that form part of some of the complexes with human DPP-IV available at the PDB.

Recent progress of the development of dipeptidyl peptidase-4 inhibitors for the treatment of type 2 diabetes mellitus

Diabetes is a fast growing chronic metabolic disorder around the world. Dipeptidyl peptidase-4 (DPP-4) is a new promising target during type 2 diabetes glycemic control. Thus, a number of potent DPP-4 inhibitors were developed and play a rapidly evolving role in the management of type 2 diabetes in recent years. This article reviews the development of synthetic and natural DPP-4 inhibitors from 2012 to 2017 and provides their physico-chemical properties, biological activities against DPP-4 and selectivity over dipeptidyl peptidase-8/9. Moreover, the glucose-lowering mechanisms and the active site of DPP-4 are also discussed. We also discuss strategies and structure-activity relationships for identifying potent DPP-4 inhibitors, which will provide useful information for developing potent DPP-4 drugs as type 2 diabtes treatments.

Structural insights of dipeptidyl peptidase-IV inhibitors through molecular dynamics-guided receptor-dependent 4D-QSAR studies

Dipeptidyl peptidase-IV (DPP-IV) inhibitors are promising antidiabetic agents. Currently, several DPP-IV inhibitors have been approved for therapeutic use in diabetes mellitus. Receptor-dependent 4D-QSAR is comparatively a new approach which uses molecular dynamics simulations to generate conformational ensemble profiles of compounds representing a dynamic state of compounds at a target's binding site. This work describes a receptor-dependent 4D-QSAR study on triazolopiperazine derivatives. QSARINS multiple linear regression method was adopted to generate 4D-QSAR models. A model with 9 variables was found to have better predictive accuracy with [Formula: see text], [Formula: see text] (leave-one-out) = 0.592 and [Formula: see text] predicted = 0.597. The location of these 9 variables at the binding site of DPP-IV revealed the importance of the residues Val711, Tyr662, Tyr666, Val202, Asp200 and Thr199 in making critical interactions with DPP-IV inhibitors. The study of these critical interactions revealed the structural features required in DPP-IV inhibitors. Thus, in this study the importance of a halogen substituent on a phenyl ring, the extent of substitution on the triazolopiperazine ring, the presence of an ionizable amino group and the presence of a hydrophobic substituent that can bind deeper in binding pocket of DPP-IV were revealed.