Pharmacokinetics and metabolism of [14C]anagliptin, a novel dipeptidyl peptidase-4 inhibitor, in humans

Analytical and Bioanalytical Methods for the Determination of Dipeptidyl Peptidase-4 Inhibitors in Various Matrices: A Comprehensive Review

BACKGROUND

DPP-4 inhibitors, or gliptins, are new oral antidiabetic drugs for type 2 diabetes. They help to regulate insulin and glucagon. These drugs have the advantage of a lower risk of hypoglycemia compared to some other diabetes medications and are typically prescribed when metformin and sulphonylureas have become less effective.

OBJECTIVE

This review analyses a range of analytical and bioanalytical methods for DPP-4 inhibitors, that use spectroscopic techniques, chromatographic, and hyphenated techniques for analysis. So far, no review comprising all DPP-4 inhibitors has been presented. The primary objective of this review is to present the analysts with various analytical and bioanalytical methods for the quantification and estimation of DPP-4 inhibitors in different matrices.

METHODS

To improve understanding, a review was carried out by creating a database of pre-existing research from digital sources such as ScienceDirect, and PubMed. The methodology is shown in the flowchart of the literature selection process.

CONCLUSION

The comprehensive assessment of methods for analysing DPP-4 inhibitors can be a valuable resource for researchers and healthcare practitioners. Hitherto, no review encompassing all DPP-4 inhibitors has been presented. Therefore, gaps in the data available on a particular subject, need to be required to collect data on a particular construct. The review suggests that chromatographic techniques were majorly used for analysis wherein solvents like acetonitrile, methanol, and buffer solutions were used as mobile phases that can deteriorate HPLC columns and equipment. So, scientists could investigate new methods for the assessment of DPP-4 inhibitors using more eco-friendly solvents.

Sensitive quantification of fibroblast activation protein and high-throughput screening for inhibition by FDA-approved compounds

Fibroblast activation protein (FAP) has been extensively studied as a cancer biomarker for decades. Recently, small-molecule FAP inhibitors have been widely adopted as a targeting moiety of experimental theranostic radiotracers. Here we present a fast qPCR-based analytical method allowing FAP inhibition screening in a high-throughput regime. To identify clinically relevant compounds that might interfere with FAP-targeted approaches, we focused on a library of FDA-approved drugs. Using the DNA-linked Inhibitor Antibody Assay (DIANA), we tested a library of 2667 compounds within just a few hours and identified numerous FDA-approved drugs as novel FAP inhibitors. Among these, prodrugs of cephalosporin antibiotics and reverse transcriptase inhibitors, along with one elastase inhibitor, were the most potent FAP inhibitors in our dataset. In addition, by employing FAP DIANA in the quantification mode, we were able to determine FAP concentrations in human plasma samples. Together, our work expands the repertoire of FAP inhibitors, analyzes the potential interference of co-administered drugs with FAP-targeting strategies, and presents a sensitive and low-consumption ELISA alternative for FAP quantification with a detection limit of 50 pg/ml.

Financial Benefits of Renal Dose-Adjusted Dipeptidyl Peptidase-4 Inhibitors for Patients with Type 2 Diabetes and Chronic Kidney Disease

BACKGRUOUND

Dipeptidyl peptidase-4 (DPP4) inhibitors are frequently prescribed for patients with type 2 diabetes; however, their cost can pose a significant barrier for those with impaired kidney function. This study aimed to estimate the economic benefits of substituting non-renal dose-adjusted (NRDA) DPP4 inhibitors with renal dose-adjusted (RDA) DPP4 inhibitors in patients with both impaired kidney function and type 2 diabetes.

METHODS

This retrospective cohort study was conducted from January 1, 2012 to December 31, 2018, using data obtained from common data models of five medical centers in Korea. Model 1 applied the prescription pattern of participants with preserved kidney function to those with impaired kidney function. In contrast, model 2 replaced all NRDA DPP4 inhibitors with RDA DPP4 inhibitors, adjusting the doses of RDA DPP4 inhibitors based on individual kidney function. The primary outcome was the cost difference between the two models.

RESULTS

In total, 67,964,996 prescription records were analyzed. NRDA DPP4 inhibitors were more frequently prescribed to patients with impaired kidney function than in those with preserved kidney function (25.7%, 51.3%, 64.3%, and 71.6% in patients with estimated glomerular filtration rates [eGFRs] of ≥60, <60, <45, and <30 mL/min/1.73 m2, respectively). When model 1 was applied, the cost savings per year were 7.6% for eGFR <60 mL/min/1.73 m2 and 30.4% for eGFR <30 mL/min/1.73 m2. According to model 2, 15.4% to 51.2% per year could be saved depending on kidney impairment severity.

CONCLUSION

Adjusting the doses of RDA DPP4 inhibitors based on individual kidney function could alleviate the economic burden associated with medical expenses.

Role of anagliptin, a dipeptidyl peptidase-4 inhibitor, in managing type 2 diabetes: A systematic review and meta-analysis

BACKGROUND

No comprehensive meta-analysis has examined and consolidated the effectiveness and safety of anagliptin in treating type 2 diabetes mellitus (T2D). To bridge this knowledge gap, we undertook this meta-analysis.

METHODS

Randomized controlled trials involving patients with T2D receiving anagliptin were sought after through electronic databases. The control arm consisted of either an active comparator (active control group [ACG]) or a placebo (passive control group [PCG]). The primary outcome was glycated hemoglobin (HbA1c), with secondary outcomes including fasting plasma glucose (FPG) and lipid profiles and adverse events.

RESULTS

From the 226 articles first examined, 10 randomized controlled trials with 970 participants were analyzed. Reductions in HbA1c (mean difference [MD]: -0.03%, 95% confidence interval [CI]: -0.14 to 0.14, P = .51, I2 = 9%) and FPG (MD: 0.03 mmol/L, 95% CI: -0.30 to 0.35, P = .87, I2 = 42%) were similar in the anagliptin group and ACG. Anagliptin reduced FPG better than placebo (MD: -1.25 mmol/L, 95% CI: -1.87 to -0.64, P < .0001, I2 = 0%). Sufficient data were unavailable to analyze the HbA1c lowering with anagliptin versus placebo. Among the lipid parameters, changes in total cholesterol, high-density lipoprotein cholesterol, apolipoprotein B48, and apolipoprotein B100 were identical between the anagliptin and control groups (PCG and ACG). Anagliptin was better than ACG at lowering low-density lipoprotein cholesterol but not as good at lowering triglyceride. Adverse events were infrequent and similar in the anagliptin and control groups (PCG and ACG).

CONCLUSION

Anagliptin positively affects glucose control and is safe for managing T2D. Its low-density lipoprotein cholesterol-lowering effect warrants further investigation.

In vivo and in vitro metabolite profiling of nirmatrelvir using LC-Q-ToF-MS/MS along with the in silico approaches for prediction of metabolites and their toxicity

Nirmatrelvir (NRV), a 3C-like protease or Mpro inhibitor of SARS-CoV-2, is used for the treatment of COVID-19 in adult and paediatric patients. The present study was accomplished to investigate the comprehensive metabolic fate of NRV using in vitro and in vivo models. The in vitro models used for the study were microsomes (human liver microsomes, rat liver microsomes, mouse liver microsomes) and S9 fractions (human liver S9 fractions and rat liver S9 fractions) with the appropriate cofactors, whereas Sprague-Dawley rats were used as the in vivo models. Nirmatrelvir was administered orally to Sprague-Dawley rats, which was followed by the collection of urine, faeces and blood at pre-determined time intervals. Protein precipitation was used as the sample preparation method for all the samples. The samples were then analysed by liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (LC-Q-ToF-MS/MS) using an Acquity BEH C18 column with 0.1% formic acid and acetonitrile as the mobile phase. Four metabolites were found to be novel, which were formed via amide hydrolysis, oxidation and hydroxylation. Furthermore, an in silico analysis was performed using Meteor Nexus software to predict the probable metabolic changes of NRV. The toxicity and mutagenicity of NRV and its metabolites were also determined using DEREK Nexus and SARAH Nexus.

The Structure-property Relationships of Clinically Approved Protease Inhibitors

BACKGROUND

Proteases play important roles in the regulation of many physiological processes, and protease inhibitors have become one of the important drug classes. Especially because the development of protease inhibitors often starts from a substrate- based peptidomimetic strategy, many of the initial lead compounds suffer from pharmacokinetic liabilities.

OBJECTIVE

To reduce drug attrition rates, drug metabolism and pharmacokinetics studies are fully integrated into modern drug discovery research, and the structure-property relationship illustrates how the modification of the chemical structure influences the pharmacokinetic and toxicological properties of drug compounds. Understanding the structure- property relationships of clinically approved protease inhibitor drugs and their analogues could provide useful information on the lead-to-candidate optimization strategies.

METHODS

About 70 inhibitors against human or pathogenic viral proteases have been approved until the end of 2021. In this review, 17 inhibitors are chosen for the structure- property relationship analysis because detailed pharmacological and/or physicochemical data have been disclosed in the medicinal chemistry literature for these inhibitors and their close analogues.

RESULTS

The compiled data are analyzed primarily focusing on the pharmacokinetic or toxicological deficiencies found in lead compounds and the structural modification strategies used to generate candidate compounds.

CONCLUSION

The structure-property relationships hereby summarized how the overall druglike properties could be successfully improved by modifying the structure of protease inhibitors. These specific examples are expected to serve as useful references and guidance for developing new protease inhibitor drugs in the future.

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.

Metabolism and Chemical Degradation of New Antidiabetic Drugs (Part II): A Review of Analytical Approaches for Analysis of Gliptins

This paper is part II of the review on metabolism and chemical degradation of new antidiabetic drugs from glutides, gliflozins and gliptins. It is well known that metabolism data can be helpful for deriving safe levels of degradation impurities and their qualifying as far as toxicological aspects are concerned. As a result, it could link the quality of respective pharmaceutical products to clinical practice and patients. Some overlapping pathways of transformations of these important drugs of different chemical structures and different mechanisms of action were discussed. At the same time, the paper summarized interesting analytical tools for conducting modern drug metabolism as well as drug degradation experiments. The methods described here include liquid chromatography (LC) and liquid chromatography coupled with mass spectrometry (LC-MS or LC-MS/MS), which are widely used for detection and quantitative measurements of the drugs, their metabolites and degradants, as well as radiometric methods that are suitable for pharmacokinetic experiments. Special attention was paid to dedicated types of packing in chromatographic columns, as well as to special solutions in the LC-MS procedures. The present part addresses the analytical approaches elaborated for examining the metabolism and degradation pathways of gliptins that are dipeptidyl peptidase 4 (DPP-4) inhibitors.

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.

Therapeutic Effects of Switching to Anagliptin from Other DPP-4 Inhibitors in T2DM Patients with Inadequate Glycemic Control: A Non-interventional, Single-Arm, Open-Label, Multicenter Observational Study

INTRODUCTION

The effects of switching DPP-4 inhibitors in type 2 diabetes mellitus (T2DM) patients are being widely studied. However, information of which factors affect the therapeutic response is limited. We evaluated the difference in HbA1c lowering effect by comorbidity and other variables after switching to anagliptin in patients with T2DM inadequately controlled by other DPP-4 inhibitors.

METHODS

In a multicenter, open-label, single-arm, prospective observational study, patients with T2DM, HbA1c ≥ 7.0% who have taken DPP-4 inhibitors other than anagliptin, either alone or in combination (DPP-4 inhibitors + metformin/sulfonylurea (SU)/thiazolidinedione (TZD)/insulin), for at least 8 weeks were enrolled. After the switch to anagliptin, HbA1c and available clinical characteristics were determined.

RESULTS

The change in HbA1c levels from baseline to week 12 and 24 was - 0.40% and - 0.42% in all patients. However, comparing the subgroups without and with comorbidities, the change in HbA1c levels at weeks 12 and 24 was - 0.68% and - 0.89% vs. - 0.27% and 0.22%, respectively. In addition, the proportion of patients achieving HbA1c < 7% from baseline to week 12 and 24 was increased to 70% and 70% vs. 20% and 24%, respectively. Duration of T2DM and different subtype classes of DPP-4 inhibitor did not significantly contribute to the change in HbA1c.

CONCLUSION

In patients with T2DM poorly controlled by other DPP-4 inhibitors, HbA1c levels were significantly decreased after switching to anagliptin. Given that the change in HbA1c was greater in patients without comorbidities than in patients with comorbidities, switching to anagliptin before adding other oral hypoglycemic agents (OHAs) may be an option in patients without comorbidities.

Role and mechanism(s) of incretin-dependent therapies for treating diabetes mellitus

Diabetes mellitus (DM) is a worldwide ailment which leads to chronic complications like cardiac disorders, renal perturbations, limb amputation and blindness. Type one diabetes (T1DM), Type two diabetes (T2DM), Another types of diabetes, such as genetic errors in function of β-cell and action of insulin, cystic fibrosis, chemical-instigated diabetes or following tissue transplantation), and pregnancy DM (GDM). In response to nutritional ingestion, the gut may release a pancreatic stimulant that affects carbohydrate metabolism. The duodenum produces a 'chemical excitant' that stimulates pancreatic output, and researchers have sought to cure diabetes using gut extract injections, coining the word 'incretin' to describe the phenomena. Incretins include GIP and GLP-1. The 'enteroinsular axis' is the link between pancreas and intestine. Nutrient, neuronal and hormonal impulses from intestine to cells secreting insulin were thought to be part of this axis. In addition, the hormonal component, incretin, must meet two requirements: (1) it secreted by foods, mainly carbohydrates, and (2) it must induce an insulinotropic effect which is glucose-dependent. In this review, we clarify the ability of using incretin-dependent treatments for treating DM.

Possibility of pharmacokinetic drug interaction between a DPP-4 inhibitor and a SGLT2 inhibitor

Type 2 diabetes mellitus is a multifactorial condition characterized by high level of sugar in the blood. To control hyperglycemia, combination therapy is recommended if monotherapy fails to achieve glycemic control. The combination of a dipeptidyl peptidase-4 (DPP-4) inhibitor and a sodium-glucose cotransporter type 2 (SGLT2) inhibitor is a promising option of the combination therapies in terms of safety as well as efficacy. Despite of the value of combination therapy of these two agents, the pharmacokinetic drug interactions between these two classes of agents have been evaluated in a few drugs. Thus, we reviewed the potential pharmacokinetic drug interaction based on the in vitro metabolism- and transporter-mediated drug interaction information as well as drug interaction studies in human, between a DPP-4 inhibitor and a SGLT2 inhibitor which are marketed in South Korea.

Drug interactions of dipeptidyl peptidase 4 inhibitors involving CYP enzymes and P-gp efflux pump

Dipeptidyl peptidase 4 (DPP4) inhibitors are oral antidiabetic drugs approved to manage type 2 diabetes mellitus. Saxagliptin is a substrate of CYP3A4/5 enzymes while other DPP4 inhibitors such as sitagliptin, linagliptin, gemigliptin and teneligliptin are weak substrates of CYP3A4. DPP4 inhibitors have also been identified as substrates of P-gp. Hence, the drugs inhibiting or inducing CYP3A4/5 enzymes and/or P-gp can alter the pharmacokinetics of DPP4 inhibitors. This review is aimed to identify the drugs interacting with DPP4 inhibitors. The plasma concentrations of saxagliptin have been reported to be increased significantly by the concomitant administration of ketoconazole or diltiazem while no significant interactions between various DPP4 inhibitors and drugs like warfarin, digoxin or cyclosporine have been identified.

Hydrolytic Metabolism of Cyanopyrrolidine DPP-4 Inhibitors Mediated by Dipeptidyl Peptidases

Nitrile group biotransformation is an unusual or minor metabolic pathway for most nitrile-containing drugs. However, for some cyanopyrrolidine dipeptidyl peptidase 4 (DPP-4) inhibitors (vildagliptin, anagliptin, and besigliptin, but not saxagliptin), the conversion of nitrile group into carboxylic acid is their major metabolic pathway in vivo. DPP-4 was reported to be partly involved in the metabolism. In our pilot study, it was also observed that saxagliptin, a DPP-4 specific inhibitor, decreased the plasma exposures of besigliptin carboxylic acid in rats by only 20%. Therefore, it is speculated that some other enzymes may participate in nitrile group hydrolysis. After incubating gliptins with the cytosol, microsomes, and mitochondria of liver and kidney, carboxylic acid metabolites could all be formed. In recombinant DPP family such as DPP-4, DPP-2, DPP-8, DPP-9, and fibroblast activation protein-α, more hydrolytic metabolites were found. Among them, DPP-2 had the highest hydrolytic capacity besides DPP-4, and the DPP-4 inhibitor saxagliptin and DPP-2 inhibitor AX8819 can both inhibit the hydrolysis of gliptins. Western blot results showed that DPP-2 and DPP-4 existed in the aforementioned subcellular organelles at varying amounts. In rats, AX8819 decreased the plasma exposures of besigliptin carboxylic acid by 40%. The amide intermediates of gliptins were detected in vivo and in vitro. When the amide derivatives of gliptins were incubated with DPP-4, they were completely hydrolyzed at a rate far more than that from the parent drug, including saxagliptin-amide. Therefore, it was proposed that gliptins, except saxagliptin, were initially hydrolyzed to their amides by DPPs, which was the rate-limiting step in generating the carboxylic end product.

Pharmacology of dipeptidyl peptidase-4 inhibitors and its use in the management of metabolic syndrome: a comprehensive review on drug repositioning

OBJECTIVES

Despite advances in our understanding of metabolic syndrome (MetS) and the treatment of each of its components separately, currently there is no single therapy approved to manage it as a single condition. Since multi-drug treatment increases drug interactions, decreases patient compliance and increases health costs, it is important to introduce single therapies that improve all of the MetS components.

EVIDENCE ACQUISITION

We conducted a PubMed, Scopus, Google Scholar, Web of Science, US FDA, utdo.ir and clinicaltrial.gov search, gathered the most relevant preclinical and clinical studies that have been published since 2010, and discussed the beneficial effects of dipeptidyl peptidase (DPP)-4 inhibitors to prevent and treat different constituent of the MetS as a single therapy. Furthermore, the pharmacology of DPP-4 inhibitors, focusing on pharmacodynamics, pharmacokinetics, drug interactions and their side effects are also reviewed.

RESULTS

DPP-4 inhibitors or gliptins are a new class of oral anti-diabetic drugs that seem safe drugs with no severe side effects, commonly GI disturbance, infection and inflammatory bowel disease. They increase mass and function of pancreatic β-cells, and insulin sensitivity in liver, muscle and adipose tissue. It has been noted that gliptin therapy decreases dyslipidemia. DPP-4 inhibitors increase fatty oxidation, and cholesterol efflux, and decrease hepatic triglyceride synthase and de novo lipogenesis. They delay gastric emptying time and lead to satiety. Besides, gliptin therapy has anti-inflammatory and anti-atherogenic impacts, and improves endothelial function and reduces vascular stiffness.

CONCLUSION

The gathered data prove the efficacy of DPP-4 inhibitors in managing MetS in some levels beyond anti-diabetic effects. This review could be a lead for designing new DPP-4 inhibitors with greatest effects on MetS in future. Introducing drugs with polypharmacologic effects could increase the patient's compliance and decrease the health cost that there is not in multi-drug therapy. Graphical abstract ᅟ.

Identification of a novel metabolite of vildagliptin in humans: Cysteine targets the nitrile moiety to form a thiazoline ring

The dipeptidyl peptidase-4 (DPP-4) inhibitor vildagliptin (VG) is used to treat type 2 diabetes. In rare cases, VG-induced liver injury has been reported. One case report suggested that immune responses were involved in the hepatotoxicity. However, the underlying mechanisms of VG-induced hepatotoxicity are uncertain. In the present study, we investigated whether VG has the potential to covalently bind to macromolecules in cells, a process that could initiate immune-mediated hepatotoxicity. For comparison, M20.7, a major metabolite of VG, and other DPP-4 inhibitors were also evaluated. We found that VG and anagliptin (ANG), which both contain a cyanopyrrolidine moiety, rapidly reacted in non-enzymatic manners on co-incubation with l-cysteine. Both VG and ANG had half-lives of 20-30 min. In contrast, incubation with GSH, rather than l-cysteine, failed to decrease the concentrations of VG or ANG. M20.7, sitagliptin, linagliptin, and alogliptin, having no cyanopyrrolidine moiety, were stable on incubation with l-cysteine or GSH. Structural analysis of the VG- and ANG-cysteine adducts, designated M407 and M487, respectively, revealed that the nitrile moieties of VG and ANG were irreversibly converted to a thiazoline acid. In conclusion, we found that VG and ANG have the potential to covalently bind to a thiol residue of l-cysteine in proteins. Such binding may lead to unpredictable immune responses in humans. l-Cysteine, rather than GSH, would likely be useful to detect the potential for covalent binding that could initiate immune-mediated hepatotoxicity.

LC/QTOF/MS/MS characterization, molecular docking and in silico toxicity prediction studies on degradation products of anagliptin

Pharmaceutical drugs are potential molecules with specific biological activity. However, long-term use of these chemical molecules can affect the human physiological system because of their increased levels in the human body. Therefore, identification and structure elucidation of impurities or degradation products should be taken into consideration in order to assure drug safety. The present study assessed the degradation behaviour of dipeptidyl peptidase-4 (DPP-4) inhibitor anagliptin under different stress conditions as per ICH guidelines Q1A (R2) followed by elucidation of the structure of degradation products. All the stress samples were analysed by using UPLC/PDA. The superior separation of drug from its degradation products was attained with time programmed gradient elution on BEH C18 (100 mm × 2.1 mm, 1.7 μm) column using 10 mM ammonium formate (aqueous) and acetonitrile (organic) as the mobile phase components. All the degradation products of anagliptin were characterized using LC/QTOF/MS/MS. In addition, the activity and toxicity of degradation products were determined through molecular docking and in silico toxicity prediction studies, respectively. The developed UPLC/PDA method was validated as per ICH guidelines in terms of specificity, accuracy, precision, linearity and robustness.

Renal Drug Transporters and Drug Interactions

Transporters in proximal renal tubules contribute to the disposition of numerous drugs. Furthermore, the molecular mechanisms of tubular secretion have been progressively elucidated during the past decades. Organic anions tend to be secreted by the transport proteins OAT1, OAT3 and OATP4C1 on the basolateral side of tubular cells, and multidrug resistance protein (MRP) 2, MRP4, OATP1A2 and breast cancer resistance protein (BCRP) on the apical side. Organic cations are secreted by organic cation transporter (OCT) 2 on the basolateral side, and multidrug and toxic compound extrusion (MATE) proteins MATE1, MATE2/2-K, P-glycoprotein, organic cation and carnitine transporter (OCTN) 1 and OCTN2 on the apical side. Significant drug-drug interactions (DDIs) may affect any of these transporters, altering the clearance and, consequently, the efficacy and/or toxicity of substrate drugs. Interactions at the level of basolateral transporters typically decrease the clearance of the victim drug, causing higher systemic exposure. Interactions at the apical level can also lower drug clearance, but may be associated with higher renal toxicity, due to intracellular accumulation. Whereas the importance of glomerular filtration in drug disposition is largely appreciated among clinicians, DDIs involving renal transporters are less well recognized. This review summarizes current knowledge on the roles, quantitative importance and clinical relevance of these transporters in drug therapy. It proposes an approach based on substrate-inhibitor associations for predicting potential tubular-based DDIs and preventing their adverse consequences. We provide a comprehensive list of known drug interactions with renally-expressed transporters. While many of these interactions have limited clinical consequences, some involving high-risk drugs (e.g. methotrexate) definitely deserve the attention of prescribers.

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.

Comparative review of dipeptidyl peptidase-4 inhibitors and sulphonylureas

Type 2 diabetes (T2DM) is a progressive disease, and pharmacotherapy with a single agent does not generally provide durable glycaemic control over the long term. Sulphonylurea (SU) drugs have a history stretching back over 60 years, and have traditionally been the mainstay choice as second-line agents to be added to metformin once glycaemic control with metformin monotherapy deteriorates; however, they are associated with undesirable side effects, including increased hypoglycaemia risk and weight gain. Dipeptidyl peptidase (DPP)-4 inhibitors are, by comparison, more recent, with the first compound being launched in 2006, but the class now globally encompasses at least 11 different compounds. DPP-4 inhibitors improve glycaemic control with similar efficacy to SUs, but do not usually provoke hypoglycaemia or weight gain, are relatively free from adverse side effects, and have recently been shown not to increase cardiovascular risk in large prospective safety trials. Because of these factors, DPP-4 inhibitors have become an established therapy for T2DM and are increasingly being positioned earlier in treatment algorithms. The present article reviews these two classes of oral antidiabetic drugs (DPP-4 inhibitors and SUs), highlighting differences and similarities between members of the same class, as well as discussing the potential advantages and disadvantages of the two drug classes. While both classes have their merits, the choice of which to use depends on the characteristics of each individual patient; however, for the majority of patients, DPP-4 inhibitors are now the preferred choice.

Antidiabetic treatment with gliptins: focus on cardiovascular effects and outcomes

The traditional oral pharmacological therapy for type 2 diabetes mellitus (T2DM) has been based on the prescription of metformin, a biguanide, as first line antihyperglycemic agent world over. It has been demonstrated that after 3 years of treatment, approximately 50 % of diabetic patients could achieve acceptable glucose levels with monotherapy; but by 9 years this had declined to only 25 %. Therefore, the implementation of a combined pharmacological therapy acting via different pathways becomes necessary, and its combination with a compound of the sulfonylurea group was along decades the most frequently employed prescription in routine clinical practice. Meglitinides, glitazones and alpha-glucosidase inhibitors were subsequently developed, but the five mentioned groups of oral antihyperglycemic agents are associated with variable degrees of undesirable or even severe cardiovascular events. The gliptins—also called dipeptidyl peptidase 4 (DPP4) inhibitors—are an additional group of antidiabetic compounds with increasing clinical use. We review the status of the gliptins with emphasis on their capabilities to positively or negatively affect the cardiovascular system, and their potential involvement in major adverse cardiovascular events (MACE). Alogliptin, anagliptin, linagliptin, saxagliptin, sitagliptin, teneligliptin and vildagliptin are the compounds currently in clinical use. Regardless differences in chemical structure and metabolic pathways, gliptins as a group exert favorable changes in experimental models. These changes, as an almost general rule, include improved endothelial function, reduction of inflammatory markers, oxidative stress ischemia/reperfusion injury and atherogenesis. In addition, increased adiponectin levels and modest decreases in lipidemia and blood pressure were reported. In clinical settings, several trials—notably the longer one, employing sitagliptin, with a mean follow-up period of 3 years—did not show an increased risk for ischemic events. Anyway, it should be emphasized that the encouraging results from basic science were not yet translated into clinical evidence, probably due the multiple and pleiotropic enzymatic effects of DPP4 inhibition. Moreover, when employing saxagliptin, while the drug was not associated with an augmented risk for ischemic events, it should be pinpointed that the rate of hospitalization for heart failure was significantly increased. Gliptins as a group constitute a widely accepted therapy for the management of T2DM, usually as a second-line medication. Nonetheless, for the time being, a definite relationship between gliptins treatment and improved cardiovascular outcomes remains uncertain and needs yet to be proven.

DPP4 in Diabetes

Dipeptidyl-peptidase 4 (DPP4) is a glycoprotein of 110 kDa, which is ubiquitously expressed on the surface of a variety of cells. This exopeptidase selectively cleaves N-terminal dipeptides from a variety of substrates, including cytokines, growth factors, neuropeptides, and the incretin hormones. Expression of DPP4 is substantially dysregulated in a variety of disease states including inflammation, cancer, obesity, and diabetes. Since the incretin hormones, glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide (GIP), are major regulators of post-prandial insulin secretion, inhibition of DPP4 by the gliptin family of drugs has gained considerable interest for the therapy of type 2 diabetic patients. In this review, we summarize the current knowledge on the DPP4–incretin axis and evaluate most recent findings on DPP4 inhibitors. Furthermore, DPP4 as a type II transmembrane protein is also known to be cleaved from the cell membrane involving different metalloproteases in a cell-type-specific manner. Circulating, soluble DPP4 has been identified as a new adipokine, which exerts both para- and endocrine effects. Recently, a novel receptor for soluble DPP4 has been identified, and data are accumulating that the adipokine-related effects of DPP4 may play an important role in the pathogenesis of cardiovascular disease. Importantly, circulating DPP4 is augmented in obese and type 2 diabetic subjects, and it may represent a molecular link between obesity and vascular dysfunction. A critical evaluation of the impact of circulating DPP4 is presented, and the potential role of DPP4 inhibition at this level is also discussed.

Anagliptin, a potent dipeptidyl peptidase IV inhibitor: its single-crystal structure and enzyme interactions

The single-crystal structure of anagliptin, N-[2-({2-[(2S)-2-cyanopyrrolidin-1-yl]-2-oxoethyl}amino)-2-methylpropyl]-2-methylpyrazolo[1,5-a]pyrimidine-6-carboxamide, was determined. Two independent molecules were held together by intermolecular hydrogen bonds, and the absolute configuration of the 2-cyanopyrrolidine ring delivered from l-prolinamide was confirmed to be S. The interactions of anagliptin with DPP-4 were clarified by the co-crystal structure solved at 2.85 Å resolution. Based on the structure determined by X-ray crystallography, the potency and selectivity of anagliptin were discussed, and an SAR study using anagliptin derivatives was performed.

Anagliptin and sitagliptin as add-ons to metformin for patients with type 2 diabetes: a 24-week, multicentre, randomized, double-blind, active-controlled, phase III clinical trial with a 28-week extension

We conducted a 24-week, multicentre, double-blind, randomized study with a 28-week extension to compare the efficacy and safety of anagliptin and sitagliptin as an add-on to metformin in patients with type 2 diabetes. Patients inadequately controlled on metformin were randomized to either anagliptin (100 mg twice daily, n = 92) or sitagliptin (100 mg once daily, n = 88). The primary endpoint was the change in glycated haemoglobin (HbA1c) from baseline to week 24. The mean changes in HbA1c were -0.85 ± 0.70% (p < 0.0001) for anagliptin and -0.83 ± 0.61% (p < 0.0001) for sitagliptin, with a mean difference of -0.02% (95% confidence interval of difference, -0.22 to 0.18%). In both groups, the fasting proinsulin : insulin ratio significantly decreased from baseline, with improved insulin secretion. Safety profiles were similar in each group. In conclusion, the non-inferiority of the efficacy of anagliptin to sitagliptin as an add-on therapy was established with regard to efficacy and safety.

Dipeptidyl peptidase-4 greatly contributes to the hydrolysis of vildagliptin in human liver

The major metabolic pathway of vildagliptin in mice, rats, dogs, and humans is hydrolysis at the cyano group to produce a carboxylic acid metabolite M20.7 (LAY151), whereas the major metabolic enzyme of vildagliptin has not been identified. In the present study, we determined the contribution rate of dipeptidyl peptidase-4 (DPP-4) to the hydrolysis of vildagliptin in the liver. We performed hydrolysis assay of the cyano group of vildagliptin using mouse, rat, and human liver samples. Additionally, DPP-4 activities in each liver sample were assessed by DPP-4 activity assay using the synthetic substrate H-glycyl-prolyl-7-amino-4-methylcoumarin (Gly-Pro-AMC). M20.7 formation rates in liver microsomes were higher than those in liver cytosol. M20.7 formation rate was significantly positively correlated with the DPP-4 activity using Gly-Pro-AMC in liver samples (r = 0.917, P < 0.01). The formation of M20.7 in mouse, rat, and human liver S9 fraction was inhibited by sitagliptin, a selective DPP-4 inhibitor. These findings indicate that DPP-4 is greatly involved in vildagliptin hydrolysis in the liver. Additionally, we established stable single expression systems of human DPP-4 and its R623Q mutant, which is the nonsynonymous single-nucleotide polymorphism of human DPP-4, in human embryonic kidney 293 (HEK293) cells to investigate the effect of R623Q mutant on vildagliptin-hydrolyzing activity. M20.7 formation rate in HEK293 cells expressing human DPP-4 was significantly higher than that in control HEK293 cells. Interestingly, R623Q mutation resulted in a decrease of the vildagliptin-hydrolyzing activity. Our findings might be useful for the prediction of interindividual variability in vildagliptin pharmacokinetics.

A randomized, placebo-controlled, double-blind, phase 3 trial to evaluate the efficacy and safety of anagliptin in drug-naïve patients with type 2 diabetes

The aim of this study was to evaluate the efficacy and safety of anagliptin in drug-naïve patients with type 2 diabetes in a double-blind randomized placebo-controlled study. A total of 109 patients were randomized to 100 mg (n=37) or 200 mg (n=33) anagliptin twice daily or placebo (n=39). The primary objective was to alter HbA1c levels from baseline at a 24-week endpoint. The overall baseline mean age and body mass index were 56.20 ± 9.77 years and 25.01 ± 2.97 kg/m(2), respectively, and the HbA1c level was of 7.14 ± 0.69 %. Anagliptin at 100 mg and 200 mg produced significant reductions in HbA1c (-0.50 ± 0.45 % and -0.51 ± 0.55%, respectively), and the placebo treatment resulted in an increase in HbA1c by 0.23 ± 0.62 %. Both doses of anagliptin produced significant decreases in fasting plasma glucose (-0.53 ± 1.25 mmol/L and -0.72 ± 1.25 mmol/L, respectively) and the proinsulin/insulin ratio (-0.04 ± 0.15 and -0.07 ± 0.18, respectively) compared with placebo. No meaningful body weight changes from baseline were observed in three groups. Plasma dipeptidyl peptidase (DPP)-4 activity was significantly inhibited after 24 weeks of anagliptin treatment, and >75% and >90% inhibitions were observed during the meal tolerance tests with 100 mg and 200 mg anagliptin, respectively. The incidences of adverse or serious adverse events were similar among the three study groups. Twice-daily anagliptin therapy effectively inhibited DPP-4 activity and improved glycemic control and was well-tolerated in patients with type 2 diabetes.

GLP-1(28-36)amide, the Glucagon-like peptide-1 metabolite: friend, foe, or pharmacological folly?

The glucagon-like peptide-1 (GLP-1) axis has emerged as a major therapeutic target for the treatment of type 2 diabetes. GLP-1 mediates its key insulinotropic effects via a G-protein coupled receptor expressed on β-cells and other pancreatic cell types. The insulinotropic activity of GLP-1 is terminated via enzymatic cleavage by dipeptidyl peptidase-4. Until recently, GLP-1-derived metabolites were generally considered metabolically inactive; however, accumulating evidence indicates some have biological activity that may contribute to the pleiotropic effects of GLP-1 independent of the GLP-1 receptor. Recent reports describing the putative effects of one such metabolite, the GLP-1-derived nonapeptide GLP-1(28-36) amide, are the focus of this review. Administration of the nonapeptide elevates cyclic adenosine monophosphate (cAMP) and activates protein kinase A, β-catenin, and cAMP response-element binding protein in pancreatic β-cells and hepatocytes. In stressed cells, the nonapeptide targets the mitochondria and, via poorly defined mechanisms, helps to maintain mitochondrial membrane potential and cellular adenosine triphosphate levels and to reduce cytotoxicity and apoptosis. In mouse models of diet-induced obesity, treatment with the nonapeptide reduces weight gain and ameliorates associated pathophysiology, including hyperglycemia, hyperinsulinemia, and hepatic steatosis. Nonapeptide administration in a streptozotocin-induced model of type 1 diabetes also improves glucose disposal concomitant with elevated insulin levels and increased β-cell mass and proliferation. Collectively, these results suggest some of the beneficial effects of GLP-1 receptor analogs may be mediated by the nonapeptide. However, the concentrations required to elicit some of these effects are in the micromolar range, leading to reservations about potentially related therapeutic benefits. Moreover, although controversial, concerns have been raised about the potential for incretin-based therapies to promote pancreatitis and pancreatic and thyroid cancers. The effects ascribed to the nonapeptide make it a potential contributor to such outcomes, raising additional questions about its therapeutic suitability. Notwithstanding, the nonapeptide, like other GLP-1 metabolites, appears to be biologically active. Increasing understanding of such noncanonical GLP-1 activities should help to improve future incretin-based therapeutics.

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.