Linagliptin: a review of its use in the management of type 2 diabetes mellitus

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.

Comparative effects of glucagon-like peptide-1 receptors agonists, 4-dipeptidyl peptidase inhibitors, and metformin on metabolic syndrome

AIMS

To assess the comparative effects of glucagon-like peptide-1 receptor agonists (GLP-1RA), 4-dipeptidyl peptidase inhibitors (DPP-4I), and metformin treatment during one year on metabolic syndrome (MetS) components and severity in MetS patients.

METHODS

Prospective study (n = 6165 adults) within the frame of PREDIMED-Plus trial. The major end-point was changes on MetS components and severity after one- year treatment of GLP-1RA, DPP-4I, and metformin. Anthropometric measurements (weight, height and waist circumference), body mass index (BM), and blood pressure were registered. Blood samples were collected after overnight fasting. Plasma glucose, glycosylated hemoglobin (HbA1c), plasma triglycerides and cholesterol were measured. Dietary intakes as well as physical activity were assessed through validated questionnaires.

RESULTS

MetS parameters improved through time. The treated groups improved glycaemia compared with untreated (glycaemia ∆ untreated: -1.7 mg/dL(± 13.5); ∆ metformin: - 2.5(± 23.9) mg/dL; ∆ DPP-4I: - 4.5(± 42.6); mg/dL ∆ GLP-1RA: - 4.3(± 50.9) mg/dL; and HbA1c: ∆ untreated: 0.0(± 0.3) %; ∆ metformin: - 0.1(± 0.7) %; ∆ DPP-4I: - 0.1(± 1.0) %; ∆ GLP-1RA: - 0.2(± 1.2) %. Participants decreased BMI and waist circumference. GLP-1RA and DPP-4I participants registered the lowest decrease in BMI (∆ untreated: -0.8(± 1.6) kg/m²; ∆ metformin: - 0.8(± 1.5) kg/m²; ∆ DPP-4I: - 0.6(± 1.3) kg/m²; ∆ GLP-1RA: - 0.5(± 1.2) kg/m². and their waist circumference (∆ untreated: -2.8(± 5.2) cm; ∆ metformin: - 2.6(± 15.2) cm; ∆ DPP-4I: - 2.1(± 4.8) cm; ∆ GLP-1RA: - 2.4(± 4.1) cm.

CONCLUSION

In patients with MetS and healthy lifestyle intervention, those treated with GLP-1RA and DPP-4I obtained better glycemic profile. Anthropometric improvements were modest.

Comparison of Adverse Events Occurred During Administration of Dipeptidyl Peptidase-4 Inhibitor in Patients with Diabetes Using FDA Adverse Event Reporting System

BACKGROUND AND OBJECTIVE

Various dipeptidyl peptidase-4 (DPP-4) inhibitors have been approved for the treatment of diabetes. The frequencies of known serious side effects might differ among DPP-4 inhibitors, therefore a large sample size is needed to study them in prospective clinical trials. We examined the adverse events that occurred during the administration of a DPP-4 inhibitor in patients with diabetes using FDA Adverse Event Reporting System (FAERS) data.

METHODS

We used FAERS data reported between January 2013 and March 2022 in patients with diabetes who received a DPP-4 inhibitor. Statistical analyses were conducted to calculate reporting odds ratio (ROR) and adjusted ROR (aROR) controlling for differences in patient background.

RESULTS

The 9 target DPP-4 inhibitors were sitagliptin (N = 26,843), vildagliptin (N = 4767), alogliptin (N = 2085), linagliptin (N = 7969), saxagliptin (N = 3334), teneligliptin (N = 461), anagliptin (N = 102), trelagliptin (N = 17), and omarigliptin (N = 12). Compared with sitagliptin, aROR of acute kidney injury was significantly < 1.000 for alogliptin (0.247 [95% confidence interval (CI) 0.150-0.408], p < 0.001) but aROR of pemphigoid was significantly > 1.000 for alogliptin (3.082 [95% CI 2.156-4.406], p < 0.001). Similar statistical analyses were conducted for other adverse events and the types of adverse events with aROR of significantly < 1.000 or > 1.000 differed depending on the type of DPP-4 inhibitor.

CONCLUSIONS

Although it is impossible to select a DPP-4 inhibitor with aROR of < 1.000 of all occurrences of adverse events, these results may be used for drug selection when the patient has adverse events that need to be avoided. We provided the sample code of software R that can reproduce the results.

Natural Compounds as DPP-4 Inhibitors: 3D-Similarity Search, ADME Toxicity, and Molecular Docking Approaches

Type 2 diabetes mellitus is one of the most common diseases of the 21st century, caused by a sedentary lifestyle, poor diet, high blood pressure, family history, and obesity. To date, there are no known complete cures for type 2 diabetes. To identify bioactive natural products (NPs) to manage type 2 diabetes, the NPs from the ZINC15 database (ZINC-NPs DB) were screened using a 3D shape similarity search, molecular docking approaches, and ADMETox approaches. Frequently, in silico studies result in asymmetric structures as “hit” molecules. Therefore, the asymmetrical FDA-approved diabetes drugs linagliptin (8-[(3R)-3-aminopiperidin-1-yl]-7-but-2-ynyl-3-methyl-1-[(4-methylquinazolin-2-yl)methyl]purine-2,6-dione), sitagliptin ((3R)-3-amino-1-[3-(trifluoromethyl)-6,8-dihydro-5H-[1,2,4]triazolo[4,3-a]pyrazin-7-yl]-4-(2,4,5-trifluorophenyl)butan-1-one), and alogliptin (2-[[6-[(3R)-3-aminopiperidin-1-yl]-3-methyl-2,4-dioxopyrimidin-1-yl]methyl]benzonitrile) were used as queries to virtually screen the ZINC-NPs DB and detect novel potential dipeptidyl peptidase-4 (DPP-4) inhibitors. The most promising NPs, characterized by the best sets of similarity and ADMETox features, were used during the molecular docking stage. The results highlight that 11 asymmetrical NPs out of 224,205 NPs are potential DPP-4 candidates from natural sources and deserve consideration for further in vitro/in vivo tests.

Comparison of effects of Empagliflozin and Linagliptin on renal function and glycaemic control: a double-blind, randomized clinical trial

Background

This study aimed to compare the effects of Linagliptin and Empagliflozin on renal function and glycaemic control in patients with type 2 diabetes mellitus (DM).

Method

We conducted a randomized, double-blind, parallel trial on patients aged 30 to 80 years with type 2 DM and HbA1c ≤ 9%, regardless of background medical therapy, to compare the effects of Empagliflozin and Linagliptin on albuminuria, FBS, HbA1c, and eGFR. Participants were given the mentioned drugs for 12 weeks. Statistical analysis was performed using appropriate tests in IBM™SPSS® statistics software for windows version 24.

Results

In total, 60 patients participated in the study, thirty patients in each group. The mean age of participants was 56.8 (SD = 8.15) in the Empagliflozin group and 60.9 (SD = 7.22) in the Linagliptin group. Before the intervention, FBS, HbA1C, and albuminuria values were significantly higher in the Empagliflozin group than those in the Linagliptin group (P < 0.05), but there was no significant difference between groups regarding eGFR (P = 0.271). Changes in the FBS, HbA1C, and eGFR were not significantly different between groups (P > 0.05), but there was more decrease in albuminuria in the Empagliflozin group compared to the Linagliptin group (P = 0.001, Cohen’s d = 0.98).

Conclusions

Regardless of baseline albuminuria, eGFR, or HbA1c, Empagliflozin 10 mg daily significantly reduced albuminuria at 12 weeks compared to Linagliptin 5 mg daily in patients with type 2 diabetes.

Trial registration

Iranian Registry of Clinical Trials, IRCT20200722048176N1. Registered 3 August 2020.

Long-term safety and effectiveness of linagliptin by baseline body mass index in Japanese patients with type 2 diabetes: a 3-year post-marketing surveillance study

BACKGROUND

A recent 3-year post-marketing surveillance (PMS) study reaffirmed the safety and effectiveness of linagliptin in linagliptin-naïve Japanese patients with type 2 diabetes (T2D). We present further analyses from this study by body mass index (BMI).

RESEARCH DESIGN AND METHODS

Safety and effectiveness were assessed across BMI subgroups (<25, 25 to <30, and ≥30 kg/m²).

RESULTS

Data were available for 876, 566, and 201 patients in the BMI subgroups, respectively. Incidence of adverse drug reactions [ADR] with linagliptin was 11.42%, 11.31%, 10.45%, respectively. The most common ADR of special interest was hepatic disorders (n [%]: 6 [0.68], 7 [1.24] and 3 [1.49], respectively). Additional use of glucose-lowering drugs (GLDs) increased with BMI (15.0%, 19.1%, 24.4% of patients; P < 0.001). In the overall population, a sustained decrease in HbA1c was observed in all BMI subgroups. In patients receiving linagliptin with no additional GLDs, changes in HbA1c were -0.58%±0.04, -0.62%±0.04, and -0.77%±0.11.

CONCLUSIONS

In this study of linagliptin in Japanese patients with T2D, across BMI subgroups no new safety concerns were observed. The proportion of patients with additional GLD use increased with baseline BMI. Decreases in HbA1c were observed in all subgroups, including in patients with no additional GLD use.

CLINICALTRIALS.GOV

NCT01650259.

Therapeutic Advances in Diabetes, Autoimmune, and Neurological Diseases

Since 2015, 170 small molecules, 60 antibody-based entities, 12 peptides, and 15 gene- or cell-therapies have been approved by FDA for diverse disease indications. Recent advancement in medicine is facilitated by identification of new targets and mechanisms of actions, advancement in discovery and development platforms, and the emergence of novel technologies. Early disease detection, precision intervention, and personalized treatments have revolutionized patient care in the last decade. In this review, we provide a comprehensive overview of current and emerging therapeutic modalities developed in the recent years. We focus on nine diseases in three major therapeutics areas, diabetes, autoimmune, and neurological disorders. The pathogenesis of each disease at physiological and molecular levels is discussed and recently approved drugs as well as drugs in the clinic are presented.

Application of online liquid chromatography/quadrupole time-of-flight electrospray ionization tandem mass spectrometry for structural characterization of linagliptin degradation products and related impurities

RATIONALE

Linagliptin is a drug used for the management of type 2 diabetes, which is a leading cause of global ill health and mortality. Impurities can affect the quality and safety of drug products and eventually may affect human health. A robust, sensitive and reliable analytical method is required to detect, characterize, quantify and control the presence of impurities in finished pharmaceutical products such as linagliptin.

METHODS

Linagliptin was stressed under harsh conditions as in the ICH Q1A (R2) guidelines to generate degradation products. The degradation products and process-related impurities were separated using an InertSustain C8 column (4.6 mm × 150 mm, 5 μm) and characterized by tandem quadrupole time-of-flight mass spectrometry in positive mode electrospray ionization. The developed method was validated according to the ICH Q2 (R1) guidelines.

RESULTS

Upon forced degradation, 12 degradation products were obtained (6 in oxidative stress and 3 in each of acid and alkaline hydrolysis). The special finding here was the presence of a pair of isomeric degradation products in acid hydrolysis and the formation of degradation products in base hydrolysis and oxidative degradation caused by the use of acetonitrile as a diluent. The 12 degradation products and 6 process-related substances were successfully identified using liquid chromatography/tandem mass spectrometry.

CONCLUSIONS

A reversed-phase high-performance liquid chromatography method was developed and validated for the separation of the 12 degradation products and 6 process-related impurities. Structural characterization of all impurities was carried out using fragmentation pathways obtained from tandem mass spectrometry. The method was sufficiently sensitive and reproducible for quality control of linagliptin and for further research studies.

Square-wave Adsorptive Anodic Stripping Voltammetric Determination of Antidiabetic Drug Linagliptin in Pharmaceutical Formulations and Biological Fluids Using a Pencil Graphite Electrode

A simple, sensitive, low-cost, quick and reliable square-wave anodic stripping voltammetric method is described for the determination of the antidiabetic drug Linagliptin (LNG) in pure form, tablets, and spiked human urine and plasma samples. Using a pencil graphite electrode (PGE), cyclic voltammetry (CV) was applied to study the electrochemical behavior of LNG. In a Teorell-Stenhagen buffer (pH 5.5) containing 0.1 M NaClO₄ as a supporting electrolyte, the LNG yields an irreversible well-defined oxidation peak at about 1.2 V vs. Ag/AgCl electrode. The various affecting factors, such as the pH, buffer type, supporting electrolyte, accumulation potential, scan rate and accumulation time, were tested and optimized. Also, square-wave adsorptive anodic stripping voltammetric (SWAdASV) studies show that the peak current various linearly over the LNG concentration range of 0.24 - 5.20 μg mL^-1 (R² = 0.9994). The detection and quantification limits were calculated to be 0.10 and 0.33 μg mL^-1, respectively. The proposed procedure exhibits a good precision, selectivity, and stability and was applied successfully to determine the LNG in pharmaceutical formulations (tablets) and biological fluids (spiked human urine and plasma samples).

Long-Term Safety and Effectiveness of Linagliptin in Japanese Patients with Type 2 Diabetes Mellitus: A 3-Year Post-Marketing Surveillance Study

INTRODUCTION

Clinical trials of linagliptin in Japanese patients conducted to date have had limited observational periods; therefore, there is a need for additional longer-term real-world data. The aim of this study was to investigate the long-term safety and effectiveness of linagliptin in routine clinical practice.

METHODS

This was a prospective, observational, post-marketing surveillance study conducted over 156 weeks in patients with type 2 diabetes mellitus who started linagliptin monotherapy. The primary endpoint was the incidence of adverse drug reactions (ADRs). The secondary endpoint was the change in glycated hemoglobin (HbA1c) from baseline to last available observation. Other effectiveness endpoints included the change in HbA1c and change in fasting plasma glucose (FPG) from baseline to week 26 and over the course of the treatment period.

RESULTS

Overall, 2235 and 2054 patients were included in the safety and effectiveness analysis sets, respectively. Patients were mostly male (58.4%), and the mean age was 66.7 years. The incidence of ADRs was 10.7% (n = 240). The most frequent ADRs according to MedDRA preferred terms were diabetes mellitus (n = 35 patients, 1.6%), constipation (n = 21, 0.9%), diabetes mellitus inadequate control (n = 13, 0.6%) and hypertension (n = 13, 0.6%). The mean change in HbA1c from baseline to last observation was - 0.67% [standard deviation (SD) 1.27%, 95% confidence interval - 0.72, - 0.61]. At week 26, HbA1c and FPG showed mean ± SD changes from baseline of - 0.73 ± 1.20% and - 21.02 ± 44.33 mg/dL, respectively, that were sustained until week 156.

CONCLUSIONS

In Japanese patients with type 2 diabetes mellitus, linagliptin produced sustained reductions in HbA1c and had a safety profile consistent with the established safety profile of linagliptin.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT01650259).

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.

Saudi Heart Association (SHA) guidelines for the management of heart failure

Heart failure (HF) is the leading cause of morbidity and mortality worldwide and negatively impacts quality of life, healthcare costs, and longevity. Although data on HF in the Arab population are scarce, recently developed regional registries are a step forward to evaluating the quality of current patient care and providing an overview of the clinical picture. Despite the burden of HF in Saudi Arabia, there are currently no standardized protocols or guidelines for the management of patients with acute or chronic heart failure. Therefore, the Heart Failure Expert Committee, comprising 13 local specialists representing both public and private sectors, has developed guidelines to address the needs and challenges for the diagnosis and treatment of HF in Saudi Arabia. The ultimate aim of these guidelines is to assist healthcare professionals in delivering optimal care and standardized clinical practice across Saudi Arabia.

DPP-4 Inhibition Leads to Decreased Pancreatic Inflammatory Profile and Increased Frequency of Regulatory T Cells in Experimental Type 1 Diabetes

Sitagliptin is a dipeptidyl peptidase-4 inhibitor (iDPP-4), which has been used for type 2 diabetes treatment. Recently, iDPP-4 has been described as a promising treatment of type 1 diabetes (T1D) but is still necessary to evaluate immune effects of sitagliptin. C57BL/6 mice were induced by multiple low doses of streptozotocin. Diabetes incidence, insulin, glucagon, glucagon-like peptide-1 (GLP-1) serum levels, and inflammatory cytokine levels were quantified in pancreas homogenate after 30 and 90 days of treatment. In addition, frequencies of inflammatory and regulatory T cell subsets were determined in the spleen and in the pancreatic lymph nodes. iDPP-4 decreased blood glucose level while increased GLP-1 and insulin levels. After long-term treatment, treated diabetic mice presented decreased frequency of CD4⁺CD26⁺ T cells and increased percentage of CD4⁺CD25^hiFoxp3⁺ T cells in the spleen. Besides, pancreatic lymph nodes from diabetic mice treated with iDPP-4 presented lower percentage of CD11b⁺ cells and decreased levels of inflammatory cytokines in the pancreas. Treatment of type 1 diabetic mice with iDPP-4 improved metabolic control, decreased inflammatory profile in the pancreatic microenvironment, and increased systemic regulatory T cell frequency. Therefore, we suggest the long-term use of sitagliptin as a feasible and effective therapy for T1D.

Dipeptidyl Peptidase-4 Inhibitors for the Potential Treatment of Brain Disorders; A Mini-Review With Special Focus on Linagliptin and Stroke

Cerebral stroke is a leading cause of death and persistent disability of elderly in the world. Although stroke prevention by targeting several risk factors such as diabetes and hypertension has decreased the stroke incidence, the total number of strokes is increasing due to the population aging and new preventive therapies are needed. Moreover, post-stroke acute pharmacological strategies aimed to reduce stroke-induced brain injury have failed in clinical trials despite being effective in animal models. Finally, approximately 30% of surviving stroke patients do not recover from stroke and remain permanently dependent on supportive care in activities of daily living. Therefore, strategies to improve stroke recovery in the post-acute phase are highly needed. Linagliptin is a dipeptidyl peptidase-4 inhibitor which is clinically approved to reduce hyperglycemia in type 2 diabetes. The regulation of glycemia by dipeptidyl peptidase-4 inhibition is mainly achieved by preventing endogenous glucagon-like peptide-1 (GLP-1) degradation. Interestingly, linagliptin has also shown glycaemia-independent beneficial effects in animal models of stroke, Parkinson's disease and Alzheimer's disease. In some case the preclinical data have been supported with some clinical data. Although potentially very interesting for the development of new strategies against stroke and neurodegenerative disorders, the mode of action of linagliptin in the brain is still largely unknown and seems to occur in a GLP-1R-independent manner. The purpose of this mini-review is to summarize and discuss the recent experimental and clinical work regarding the effects of linagliptin in the central nervous system, with special emphasis on acute neuroprotection, stroke prevention and post-stroke recovery. We also highlight the main questions in this research field that need to be addressed in clinical perspective.

Biological Safety Studies and Simultaneous Determination of Linagliptin and Synthetic Impurities by LC-PDA

A stability-indicating LC method was developed for quantification of linagliptin (LGT) and three synthetic impurities. The method utilizes a Thermo Scientific® RP-8 column (100 mm × 4.6 mm; 5 μm) with the PDA detector for quantitation of impurities. A mixture of 0.1% formic acid with pH 3.5 (A) and acetonitrile (B) was used as the mobile phase at a flow rate of 0.6 mL·min^-1 with gradient elution. The percentage of mobile phase B increases from 30% to 70% over 5 min and decreases from 70% to 30% between 5 and 8 min. The method was validated according to International Council for Harmonization (ICH) guidelines. The LOD values obtained were 0.0171 μg·mL^-1 and 0.015 μg·mL^-1 for LGT and impurities, respectively. The LOQ values were 0.06 μg·mL^-1 for LGT and impurities. In all cases, the correlation coefficients of LGT and impurities were >0.999, showing the linearity of the method. The % recovery of the LGT and added impurity were in the range of 92.92-99.79%. The precision of the method showed values less than 1.47% for LGT and less than 4.63% for impurities. The robustness was also demonstrated by small modifications in the chromatographic conditions. The selectivity was evidenced because the degradation products formed in stress conditions did not interfere in the determination of LGT and impurities. Toxicity prediction studies suggested toxicity potential of the impurities, which was confirmed using biological safety studies in vitro.

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.

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.

Clinical pharmacology of dipeptidyl peptidase 4 inhibitors indicated for the treatment of type 2 diabetes mellitus

Dipeptidyl peptidase-4 (DPP-4) inhibitors are a class of oral antidiabetic drugs that improve glycaemic control without causing weight gain or increasing hypoglycaemic risk in patients with type 2 diabetes mellitus (T2DM). The eight available DPP-4 inhibitors, including alogliptin, anagliptin, gemigliptin, linagliptin, saxagliptin, sitagliptin, teneligliptin, and vildagliptin, are small molecules used orally with identical mechanism of action and similar safety profiles in patients with T2DM. DPP-4 inhibitors may be used as monotherapy or in double or triple combination with other oral glucose-lowering agents such as metformin, thiazolidinediones, or sulfonylureas. Although DPP-4 inhibitors have the same mode of action, they differ by some important pharmacokinetic and pharmacodynamic properties that may be clinically relevant in some patients. The main differences between the eight gliptins include: potency, target selectivity, oral bioavailability, elimination half-life, binding to plasma proteins, metabolic pathways, formation of active metabolite(s), main excretion routes, dosage adjustment for renal and liver insufficiency, and potential drug-drug interactions. The off-target inhibition of selective DPP-4 inhibitors is responsible for multiorgan toxicities such as immune dysfunction, impaired healing, and skin reactions. As a drug class, the DPP-4 inhibitors have become accepted in clinical practice due to their excellent tolerability profile, with a low risk of hypoglycaemia, a neutral effect on body weight, and once-daily dosing. It is unknown if DPP-4 inhibitors can prevent disease progression. More clinical studies are needed to validate the optimal regimens of DPP-4 inhibitors for the management of T2DM when their potential toxicities are closely monitored.

An ultra high performance liquid chromatography-tandem mass spectrometry method for the quantification of linagliptin in human plasma

First report of a quality linagliptin assay in human plasma using UHPLC-ESI-MS/MS.

Incretins and selective renal sodium-glucose co-transporter 2 inhibitors in hypertension and coronary heart disease

Hyperglycemia is associated with an increased risk of cardiovascular disease, and the consequences of intensive therapy may depend on the mechanism of the anti-diabetic agent(s) used to achieve a tight control. In animal models, stable analogues of glucagon-like peptide-1 (GLP-1) were able to reduce body weight and blood pressure and also had favorable effects on ischemia following coronary reperfusion. In a similar way, dipeptidyl peptidase IV (DPP-IV) showed to have favorable effects in animal models of ischemia/reperfusion. This could be due to the fact that DPP-IV inhibitors were able to prevent the breakdown of GLP-1 and glucose-dependent insulinotropic polypeptide, but they also decreased the degradation of several vasoactive peptides. Preclinical data for GLP-1, its derivatives and inhibitors of the DPP-IV enzyme degradation suggests that these agents may be able to, besides controlling glycaemia, induce cardio-protective and vasodilator effects. Notwithstanding the many favorable cardiovascular effects of GLP-1/incretins reported in different studies, many questions remain unanswered due the limited number of studies in human beings that aim to examine the effects of GLP-1 on cardiovascular endpoints. For this reason, long-term trials searching for positive cardiovascular effects are now in process, such as the CAROLINA and CARMELINA trials, which are supported by small pilot studies performed in humans (and many more animal studies) with incretin-based therapies. On the other hand, selective renal sodium-glucose co-transporter 2 inhibitors were also evaluated in the prevention of cardiovascular outcomes in type 2 diabetes. However, it is quite early to draw conclusions, since data on cardiovascular outcomes and cardiovascular death are limited and long-term studies are still ongoing. In this review, we will analyze the mechanisms underlying the cardiovascular effects of incretins and, at the same time, we will present a critical position about the real value of these compounds in the cardiovascular system and its protection.

DPP-4 Inhibitor Linagliptin Attenuates Aβ-induced Cytotoxicity through Activation of AMPK in Neuronal Cells

AIM

It is now clear that insulin signaling has important roles in regulation of neuronal functions in the brain. Dysregulation of brain insulin signaling has been linked to neurodegenerative disease, particularly Alzheimer's disease (AD). In this regard, there is evidence that improvement of neuronal insulin signaling has neuroprotective activity against amyloid β (Aβ)-induced neurotoxicity for patients with AD. Linagliptin is an inhibitor of dipeptidylpeptidase-4 (DPP-4), which improves impaired insulin secretion and insulin downstream signaling in the in peripheral tissues. However, whether the protective effects of linagliptin involved in Aβ-mediated neurotoxicity have not yet been investigated.

METHODS

In the present study, we evaluated the mechanisms by which linagliptin protects against Aβ-induced impaired insulin signaling and cytotoxicity in cultured SK-N-MC human neuronal cells.

RESULTS

Our results showed that Aβ impairs insulin signaling and causes cell death. However, linagliptin significantly protected against Aβ-induced cytotoxicity, and prevented the activation of glycogen synthase kinase 3β (GSK3β) and tau hyperphosphorylation by restoring insulin downstream signaling. Furthermore, linagliptin alleviated Aβ-induced mitochondrial dysfunction and intracellular ROS generation, which may be due to the activation of 5' AMP-activated protein kinase (AMPK)-Sirt1 signaling. This upregulation of Sirt1 expression was also observed in diabetic patients with AD coadministration of linagliptin.

CONCLUSIONS

Taken together, our findings suggest linagliptin can restore the impaired insulin signaling caused by Aβ in neuronal cells, suggesting DPP-4 inhibitors may have therapeutic potential for reducing Aβ-induced impairment of insulin signaling and neurotoxicity in AD pathogenesis.

The Place of Dipeptidyl Peptidase-4 Inhibitors in Type 2 Diabetes Therapeutics: A "Me Too" or "the Special One" Antidiabetic Class?

Incretin-based therapies, the most recent therapeutic options for type 2 diabetes mellitus (T2DM) management, can modify various elements of the disease, including hypersecretion of glucagon, abnormal gastric emptying, postprandial hyperglycaemia, and, possibly, pancreatic β cell dysfunction. Dipeptidyl peptidase-4 (DPP-4) inhibitors (gliptins) increase glucagon-like peptide-1 (GLP-1) availability and correct the "incretin defect" seen in T2DM patients. Clinical studies have shown good glycaemic control with minimal risk of hypoglycaemia or any other adverse effects, despite the reports of pancreatitis, whose association remains to be proved. Recent studies have been focusing on the putative ability of DPP-4 inhibitors to preserve pancreas function, in particular due to the inhibition of apoptotic pathways and stimulation of β cell proliferation. In addition, other cytoprotective effects on other organs/tissues that are involved in serious T2DM complications, including the heart, kidney, and retina, have been increasingly reported. This review outlines the therapeutic potential of DPP-4 inhibitors for the treatment of T2DM, focusing on their main features, clinical applications, and risks, and discusses the major challenges for the future, in particular the possibility of becoming the preferred therapy for T2DM due to their ability to modify the natural history of the disease and ameliorate nephropathy, retinopathy, and cardiovascular complications.

Design, Synthesis and Biological Evaluation of Imidazo[1,2-a]pyridine Derivatives as Novel DPP-4 Inhibitors

A new series of DPP-4 inhibitors with imidazo[1,2-a]pyridine scaffold were designed by exploiting scaffold hopping strategy and docking study. Based on docking binding model, structural modifications of 2-benzene ring and pyridine moieties of compound 5a led to the identification of compound 5d with 2, 4-dichlorophenyl group at the 2-position as a potent (IC50  = 0.13 μm), selective (DPP-8/DPP-4 = 215 and DPP-9/DPP-4 = 192) and in vivo efficacious DPP-4 inhibitor. Further, molecular docking revealed that compound 5d could retain key binding features of DPP-4 with the pyridine moiety of imidazo[1,2-a]pyridine ring providing an additional π-π interaction with Phe357 of DPP-4. Compound 5d might be a promising lead for further development of novel DPP-4 inhibitor treating T2DM.

Sitagliptin: a review of its use in patients with type 2 diabetes mellitus

Sitagliptin (Januvia(®), Xelevia™, Glactiv(®), Tesavel(®)) is an orally administered, potent and highly selective inhibitor of dipeptidyl peptidase-4 (DPP-4) and was the first agent of its class to be approved for use in the management of adults with type 2 diabetes. Numerous randomized placebo- or active comparator-controlled trials have demonstrated the efficacy of sitagliptin in terms of improving glycaemic control in patients with type 2 diabetes, including its use as monotherapy, initial combination therapy (usually with fixed-dose combinations of sitagliptin/metformin), or add-on therapy to metformin or to other antihyperglycaemic drugs, with or without metformin. The primary endpoint of the clinical trials was the reduction from baseline in glycosylated haemoglobin (HbA1c), although sitagliptin also showed beneficial effects for other endpoints, such as the proportion of patients who achieved target HbA1c, and reductions from baseline in fasting plasma glucose (FPG) levels and 2-h postprandial glucose (PPG) levels. Sitagliptin was generally well tolerated in clinical trials, had a low risk of hypoglycaemia (although this depends on background therapy) and had a neutral effect on body weight. Despite concerns regarding a possible increased risk of rare pancreatic adverse events (e.g. pancreatitis) with glucagon-like peptide-1 (GLP-1)-based therapies, such as GLP-1 receptor agonists and DPP-4 inhibitors, no causal association has been found; regulators in Europe recently conducted a review of available data, concluding that there is little evidence that these drugs could cause pancreatic inflammation or pancreatic cancer. A similar review is planned in the USA and postmarketing surveillance will continue. Thus, oral sitagliptin is an effective and generally well tolerated treatment option for the management of patients with type 2 diabetes.

DPP-4 inhibitors: focus on safety

INTRODUCTION

Dipeptidyl peptidase inhibitors (DPP-4-i) are highly selective inhibitors of the enzyme DPP-4. They act by increasing levels of incretin hormones, which have potent effects on insulin and glucagon release, gastric emptying, and satiety. Our goal is to review the safety issues related to DPP-4-i.

AREAS COVERED

This review is based upon a PubMed search of the literature using keywords alogliptin, linagliptin, saxagliptin, sitagliptin and vildagliptin, DPP-4-i, glucagon-like polypeptide-1 agonists, as well as extensive personal clinical trial experience with each of these agents. The current DPP-4-i have very different chemical structures. Saxagliptin has significant cytochrome P450 metabolism and carries a risk of drug interactions. Linagliptin has primarily entero-hepatic excretion, a benefit in renally impaired patients. A concern arose related to congestive heart failure in the SAVOR TIMI trial of saxagliptin. Several major cardiac studies are underway, with two concluded. Despite lingering uncertainty related to pancreatitis and pancreatic cancer, large randomized trials have not shown an increased risk with DPP-4-i treatment. Cutaneous adverse effects occur with a low frequency with some of these agents.

EXPERT OPINION

DPP-4-i are an additional choice in the group of anti-hyperglycemics. Their principal advantage is a low incidence of hypoglycemia, making these agents desirable in patients such as the elderly and those with cardiac disease. Several large trials have hinted at less cardiac risk with DPP-4-i than with sulfonylureas. The CAROLINA Trial comparing linagliptin and glimepiride may provide a conclusive answer to this question.

The pharmacokinetic considerations and adverse effects of DPP-4 inhibitors [corrected]

INTRODUCTION

Dipeptidyl-peptidase-4 (DPP-4) inhibitors are a class of anti-hyperglycemic agents with proven efficacy in patients with type 2 diabetes mellitus (T2DM).

AREAS COVERED

This review considers the pharmacokinetic profile, adverse effects and drug interactions of DPP-4 inhibitors. DPP-4 inhibitors have certain differences in their structure, metabolism, route of elimination and selectivity for DPP-4 over structurally related enzymes, such as DPP-8/DPP-9. They have a low potential for drug interactions, with the exception of saxagliptin that is largely metabolized by cytochrome CYP3A4/A5. Reports of pancreatitis and pancreatic cancer have raised concerns regarding the safety of DPP-4 inhibitors and are under investigation. Post-marketing surveillance has revealed less common adverse effects, especially a number of skin- and immune-related adverse effects. These issues are covered in the present review.

EXPERT OPINION

DPP-4 inhibitors are useful and efficient drugs. DPP-4 inhibitors have similar mechanism of action and similar efficacy. However, DPP-4 inhibitors have certain differences in their pharmacokinetic properties that may be associated with different clinical effects and adverse event profiles. Although clinical trials indicated a favorable safety profile, post-marketing reports revealed certain safety aspects that need further investigation. Certainly, more research is needed to clarify if the differences among DPP-4 inhibitors could lead to a different clinical and safety profile.

Dipeptidyl peptidase IV and its inhibitors: therapeutics for type 2 diabetes and what else?

The proline-specific dipeptidyl aminopeptidase IV (DPP IV, DPP-4, CD26), widely expressed in mammalians, releases X-Pro/Ala dipeptides from the N-terminus of peptides. DPP IV is responsible of the degradation of the incretin peptide hormones regulating blood glucose levels. Several families of DPP IV inhibitors have been synthesized and evaluated. Their positive effects on the degradation of the incretins and the control of blood glucose levels have been demonstrated in biological models and in clinical trials. Presently, several DPP IV inhibitors, the "gliptins", are approved for type 2 diabetes or are under clinical evaluation. However, the gliptins may also be of therapeutic interest for other diseases beyond the inhibition of incretin degradation. In this Perspective, the biological functions and potential substrates of DPP IV enzymes are reviewed and the characteristics of the DPP IV inhibitors are discussed in view of type 2 diabetes and further therapeutic interest.

Linagliptin: farmacology, efficacy and safety in type 2 diabetes treatment

Type 2 diabetes mellitus (T2DM) has a high prevalence and incidence around the world. The complex pathophysiology mechanism is among the barriers for diabetes treatment. Type 2 diabetes patients have dysfunction in incretin hormones (as glucagon-like peptide-1 or GLP-1, and glucose-dependent insulinotropic polypeptide or GIP). By inhibiting the dipeptidyl peptidase-4 (DPP-4) enzyme, it is possible to slow the inactivation of GLP-1 and GIP, promoting blood glucose level reduction in a glucose-dependent manner. Linagliptin is a highly specific and potent inhibitor of DPP-4 that is currently indicated for the treatment of type 2 diabetes. Clinical studies with linagliptin demonstrated efficacy in reducing glycated hemoglobin (HbA1c) levels in type 2 diabetes patients, while maintaining a placebo-like safety and tolerability profile. Linagliptin has an interesting pharmacokinetic profile in terms of its predominantly non-renal elimination and the main implication of this characteristic is that no dose adjustment is necessary in patients with renal disease. Also, no dose adjustment is required in patients with hepatic insufficiency, as well in elderly or obese patients. This article will review the pharmacokinetic profile, efficacy data and safety aspects of linagliptin in type 2 diabetes patients.

Linagliptin/Metformin fixed-dose combination treatment: a dual attack to type 2 diabetes pathophysiology

Combination therapies are a widely accepted approach to type 2 diabetes treatment, considering that monotherapies fail to provide adequate glycemic control in the majority of cases. The combination of oral antidiabetic agents into a single tablet would significantly simplify the therapeutic regimen and maximize patients' adherence to treatment. Recently, a fixed-dose, single-tablet, combined formulation of linagliptin (a dipeptidyl peptidase-4 inhibitor) and metformin has been approved for use in type 2 diabetic patients, and is indicated as an adjunct to diet and exercise for those patients who remain inadequately controlled despite maximal tolerated doses of metformin, metformin and sulfonylurea, or linagliptin and metformin monotherapies. The combination tablet is administered twice daily and can be used either alone or combined with sulfonylureas. Clinical trials suggest that this fixed-dose combination provides significantly superior glycemic control compared to linagliptin and metformin monotherapy, in terms of improving key parameters of glucose homeostasis such as glycosylated hemoglobin, fasting and postprandial glucose levels. It also exhibits an excellent tolerability profile, without promoting weight gain and hypoglycemic episodes. The compounds of this formulation do not display clinically relevant pharmacokinetic interactions with each other, and exert synergistic (complementary) pharmacodynamic effects, including an enhanced incretin effect, suppressed hepatic glucose production, and improved peripheral insulin sensitivity. As a result, a linagliptin/metformin fixed-dose combination offers the potential to address multiple defects of type 2 diabetes pathophysiology (pancreatic islet dysfunction, insulin resistance, increased hepatic glucose output), and most importantly, in the context of a safe, efficacious, flexible, and convenient therapeutic regimen.