Metabolism and excretion of the dipeptidyl peptidase 4 inhibitor [14C]sitagliptin in humans

Chemoproteomic identification of a DPP4 homolog in Bacteroides thetaiotaomicron

Serine hydrolases have important roles in signaling and human metabolism, yet little is known about their functions in gut commensal bacteria. Using bioinformatics and chemoproteomics, we identify serine hydrolases in the gut commensal Bacteroides thetaiotaomicron that are specific to the Bacteroidetes phylum. Two are predicted homologs of the human dipeptidyl peptidase 4 (hDPP4), a key enzyme that regulates insulin signaling. Our functional studies reveal that BT4193 is a true homolog of hDPP4 that can be inhibited by FDA-approved type 2 diabetes medications targeting hDPP4, while the other is a misannotated proline-specific triaminopeptidase. We demonstrate that BT4193 is important for envelope integrity and that loss of BT4193 reduces B. thetaiotaomicron fitness during in vitro growth within a diverse community. However, neither function is dependent on BT4193 proteolytic activity, suggesting a scaffolding or signaling function for this bacterial protease.

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.

The simultaneous quantification of Sitagliptin and Irbesartan in rat plasma using the validated LC-MS/MS method is applied to a pharmacokinetic study

Irbesartan (IRB), an angiotensin II receptor AT1 blocker, is an antihypertensive agent commonly used with Sitagliptin (STG), a novel antidiabetic agent in diabetes. A finalised and validated LC-MS/MS method was used for the bioanalytical quantification of STG and IRB to be applicable to studies on the P.K drug-drug interactions between STG and IRB. Using a YMC triart C18 column (50 mm × 4.6 mm i.d., 3 µm), both the drugs and the Tolbutamide were separated using a gradient mode with a flow rate of 1 ml/min with run time of 5 min. For analyte detection, an LC-MS/MS system with multiple reaction monitoring (MRM) was used. The technique was validated across a concentration range of 5-1000 ng/ml, with the LLOQ for both analytes being 5 ng/ml. At all QC levels accuracies from spiked samples were > 83% for both drugs and internal standards. The accuracy for STG within-batch and between-batch was found within 98.4-107.2%, and for IRB was found within 92.4-102.5%. The precision for STG within batch and between batches was less than 12.3% CV, and for IRB was less than 10.2% CV at all concentration levels. The pharmacokinetic profiles of STG and IRB were successfully applied on simultaneous oral administration to rats. This method applies to pharmacokinetic multidrug interaction studies.

Development and validation of an HPLC coupled with tandem mass spectrometry method for the determination of HSK7653, a novel super long-acting dipeptidyl peptidase-4 inhibitor, in human plasma and urine and its application to a pharmacokinetic study

HSK7653 is a novel super long-acting dipeptidyl peptidase-4 inhibitor, which is promising for the treatment of type 2 diabetes mellitus with the twice-monthly dosing regimen. In this article, a robust and sensitive HPLC coupled with tandem mass spectrometry method for determining the concentration of HSK7653 in human plasma and urine was developed and validated for the first time. Plasma and urine samples were prepared by protein precipitation. After that, the extracts were analyzed using an LC-20A HPLC system coupled with API 4000 tandem MS equipped with an electrospray ionization source in positive mode. Separation was obtained using an XBridge Phenyl column (2.1 × 50 mm, 3.5 μm) with a gradient elution of acetonitrile and water containing 0.1% formic acid and 5% acetonitrile at room temperature. This bioanalysis method has been fully validated and the results showed good sensitivity and specificity. In brief, the standard curves were linear over the concentration range of 2.00-2000 ng/ml for plasma and 20.0-20,000 ng/ml for urine, respectively. In addition, the precisions of inter- and intra-run of HSK7653 were less than 12.7% and the accuracies were -3.3% to 6.3% for both plasma and urine. Finally, this method was successfully applied to explore the pharmacokinetic characteristics of HSK7653 in Chinese healthy volunteers in a first-in-human study.

Pharmacokinetics, mass balance, and metabolism of [14C]TPN171, a novel PDE5 inhibitor, in humans for the treatment of pulmonary arterial hypertension

TPN171 is a novel phosphodiesterase-5 (PDE5) inhibitor used to treat pulmonary arterial hypertension (PAH) and erectile dysfunction (ED), which currently is undergoing phase II clinical trials in China. In this single-center, single-dose, nonrandomized, and open design study, radiolabeled [¹⁴C]TPN171 was used to investigate the metabolic mechanism, pharmacokinetic characteristics, and clearance pathways of TPN171 in 6 healthy Chinese male volunteers. Each volunteer was administered a single oral suspension of 10 mg (100 μCi) of [¹⁴C]TPN171. We found that TPN171 was absorbed rapidly in humans with a peak time (T_max) of 0.667 h and a half-life (t_1/2) of approximately 9.89 h in plasma. Excretion of radiopharmaceutical-related components was collected 216 h after administration, accounting for 95.21% of the dose (46.61% in urine and 48.60% in feces). TPN171 underwent extensive metabolism in humans. Twenty-two metabolites were detected in human plasma, urine, and feces using a radioactive detector combined with a high-resolution mass spectrometer. According to radiochromatograms, a glucuronide metabolite of O-dealkylated TPN171 exceeded 10% of the total drug-related components in human plasma. However, according to the Food and Drug Administration (FDA) guidelines, no further tests are needed to evaluate the safety of this metabolite because it is a phase II metabolite, but the compound is still worthy of attention. The main metabolic biotransformation of TPN171 was mono-oxidation (hydroxylation and N-oxidation), dehydrogenation, N-dealkylation, O-dealkylation, amide hydrolysis, glucuronidation, and acetylation. Cytochrome P450 3A4 (CYP3A4) mainly catalyzed the formation of metabolites, and CYP2E1 and CYP2D6 were involved in the oxidative metabolism of TPN171 to a lesser extent. According to the incubation data, M1 was mainly metabolized to M1G by UDP-glucuronosyltransferase 1A9 (UGT1A9), followed by UGT1A7 and UGT1A10.

Common ABCB1 SNP, C3435T could affect systemic exposure of dapagliflozin in healthy subject

P-glycoprotein (P-gp) is a transporter that plays an excretory role in epithelial cells. It is encoded by ABCB1, and single nucleotide polymorphisms (SNPs) in this gene can affect systemic drug exposure. Dapagliflozin and sitagliptin, used in type 2 diabetes treatment, are P-gp substrates. Here, we aimed to investigate whether ABCB1 polymorphisms affect dapagliflozin and sitagliptin pharmacokinetics (PK) in healthy Korean subjects. The study population consisted of 100 healthy Korean subjects (94 men and 6 women) who participated in four different clinical trials and received dapagliflozin and sitagliptin doses of 10 and 100 mg, respectively. We determined ABCB1 genotypes for the C3435T, C1236T, and G2677T/A SNPs. The relationship between the genotypes and dapagliflozin PKs was examined. Dapagliflozin and sitagliptin PK parameters were not statistically significantly affected by ABCB1 SNP genotypes. However, homozygous 3435TT subjects showed higher dapagliflozin PK parameters than CT and CC subjects. In subjects with the 3435TT and those with 3435CC and 3435CT genotypes, mean C_max, AUC_inf, and AUC_0-1 values of dapagliflozin were 223.06 ng/mL and 194.81 ng /mL (p = 0.2767), 673.58 ng*h/mL and 573.96 ng*h/mL (p = 0.0492), and 128.53 ng*h/mL and 104.61 ng*h/mL (p = 0.2678), respectively. In summary, dapagliflozin and sitagliptin PK parameters were not significantly different between individuals with C1236T and C2677T/A ABCB1 genetic polymorphisms. Dapagliflozin exhibited higher systemic exposure in 3435TT subjects than in CC/CT subjects.

The Metabolism and Excretion of the Dipeptidyl Peptidase 4 Inhibitor [14C] Cetagliptin in Healthy Volunteers

1. The metabolism and excretion of cetagliptin were investigated in healthy male subjects after a single oral dose of 100mg/50μCi [¹⁴C] cetagliptin.2. The mean concentration-time profile of cetagliptin was similar to that of total radioactivity in plasma after oral administration of [¹⁴C] cetagliptin in healthy male subjects. Cetagliptin was rapidly absorbed after oral administration. Unchanged cetagliptin was the most abundant radioactive component in all matrices investigated. Approximately 53.13% of plasma AUC of total radioactivity was accounted for by cetagliptin. Each metabolite plasma AUC was not higher than 2.93% of plasma AUC of total radioactivity. By 336 h after administration, 91.68% of the administered radioactivity was excreted, and the cumulative excretion in the urine and feces was 72.88% and 18.81%, respectively. The primary route of excretion of radioactivity was via the kidneys.3. Four metabolites were detected at trace levels, and it involved hydroxylated (M436-1 and M436-3), N- sulfate (M500), and N-carbamoyl glucuronic acid conjugates (M640B) of cetagliptin. These metabolites were detected also in plasma, urine, and feces at low levels, except that metabolite M640B was not detected in feces. All metabolites were observed with < 10% of parent compound systemic exposure after oral administration.

Biowaiver Monograph for Immediate-Release Solid Oral Dosage Forms: Sitagliptin Phosphate Monohydrate

Sitagliptin is an antihyperglycemic drug used in adults for the treatment of diabetes Type 2. Literature data and in-house experiments were applied in this monograph to assess whether methods based on the Biopharmaceutics Classification System (BCS) could be used to assess the bioequivalence of solid immediate-release (IR) oral dosage forms containing sitagliptin phosphate monohydrate, as an alternative to a pharmacokinetic study in human volunteers. The solubility and permeability characteristics of sitagliptin were reviewed according to the BCS, along with dissolution, therapeutic index, therapeutic applications, pharmacokinetics, pharmacodynamic characteristics, reports of bioequivalence (BE) / bioavailability problems, data on interactions between the drug and excipients and other data germane to the subject. All data reviewed in this monograph unambiguously support classification of sitagliptin as a BCS Class 1 drug. In light of its broad therapeutic index and lack of severe adverse effects, the clinical risks associated with moderately supraoptimal doses were deemed inconsequential, as were the risks associated with moderately suboptimal doses. Taking all evidence into consideration, it was concluded that the BCS-based biowaiver can be implemented for solid IR oral drug products containing sitagliptin phosphate monohydrate, provided (a) the test product is formulated solely with excipients commonly present in solid IR oral drug products approved in ICH or associated countries and used in amounts commonly applied in this type of product, (b) data in support of the BCS-based biowaiver are obtained using the methods recommended by the WHO, FDA, EMA or ICH and (c) the test product and the comparator product (which is the innovator product in this case) meet all in vitro dissolution specifications provided in the WHO, FDA, EMA or ICH guidance.

Development and Validation of a Method for Simultaneous Estimation of Sitagliptin and Ertugliflozin in Rat Plasma by LC-MS method

Background:

The development of sound bioanalytical LC-MS (liquid chromatography-mass spectroscopy) method(s) is of paramount importance during the process of drug discovery, development and culminating in a marketing approval. The use of oral antidiabetic agents has been increased significantly from the last decades and till now no bioanalytical method is available for quantitation of sitagliptin (SG) and ertugliflozin (EG) in biological matrix which can be applied to pharmacokinetic studies using LC-MS/MS.

Objective:

To develop a new, rapid and sensitive LC–MS/MS method for the simultaneous estimation of sitagliptin (SG) and ertugliflozin (EG) in rat plasma by liquid–liquid extraction method (LLE) using deutereated sitagliptin (SGd6) and ertugliflozin (EGd6).

Methods:

Chromatographic separation was carried out on a reverse phase Waters, Xetrra C18 (150mm x 4.6mm, 2μm) column using a mixture of acetonitrile and OPA buffer (50:50v/v) at a flow rate of 1ml/min in isocratic mode. Quantification was achieved using an electrospray ion interface operating in positive mode, under Multiple Reaction Monitoring (MRM) conditions.

Results:

The method showed excellent linearity over the concentration range of 5.00- 75.00pg/mL for sitagliptin and 0.75- 11.35pg/mL ertugliflozin. The intra-batch and inter batch precision (%CV) was ≤ 4.3% and matrix effect (%CV) was 0.02% and 0.12% for sitagliptin at HQC and LQC, respectively. Matrix effect (%CV) was 0.08% and 0.33% for ertugliflozin at HQC and LQC, respectively.

Conclusion:

The simplicity of the method allows for application in laboratories, presents a valuable tool for pharmacokinetic studies. The particular assay has been proficiently put on pharmacokinetic study in rats subjects.

Analytical quality by design in the development of a solvent-modified micellar electrokinetic chromatography method for the determination of sitagliptin and its related compounds

A solvent-modified micellar electrokinetic chromatography method was developed following the Quality by Design approach for the simultaneous determination of sitagliptin (SIT), an oral antihyperglycemic drug, and its main impurities derived from the synthesis process. The separation system was identified in the scouting phase and was made by sodium dodecyl sulphate (SDS) micelles with the addition of n-butanol and methanol. The knowledge space was investigated through an asymmetric screening matrix, taking into consideration eight critical method parameters (CMPs) involving the composition of the background electrolyte in terms of buffer concentration and pH, the concentration of surfactants and organic modifiers, and voltage. The critical method attributes (CMAs) were identified as analysis time and the distance between the tail of the electroosmotic flow system peak and the front edge of impurity I₁ (sitagliptin triazole hydrochloride). A Box-Behnken Design was used in response surface methodology for calculating the quadratic models relating the CMPs to the CMAs. From the models it was possible to compute the method operable design region (MODR) through Monte-Carlo simulations. The MODR was identified in the probability maps as the multidimensional zone where the risk of failure to achieve the desired values for the CMAs was lower than 10 %. The experimental conditions corresponding to the working point, with the MODR interval, were the following: background electrolyte, 14 (10-18) mM borate buffer pH 9.20, 100 mM SDS, 13.6 (11.1-16.0) %v/v n-butanol, 6.7 (4.5-8.8) %v/v methanol; voltage and temperature were set to 28 kV and 22 °C, respectively. The developed CE method was validated in accordance with International Council for Harmonisation guidelines and was applied to the analysis of SIT tablets. The routine analysis for the quality control of the pharmaceutical product could be conducted in about 11 min.

Ozonation of Sitagliptin: Removal Kinetics and Elucidation of Oxidative Transformation Products

Due to the increasing use and high excretion rates, high quantities of the antidiabetic drug sitagliptin (STG) enter wastewater treatment plants (WWTPs). In conventional biological treatment, only a moderate removal was achieved, and thus, STG can be detected in WWTP effluents with concentrations in the higher ng/L range. Ozonation is a widely discussed technique for advanced wastewater treatment. In lab-scale experiments, STG showed pH-dependent removal kinetics with a maximum apparent rate constant of k ∼1 × 10⁴ M^-1 s^-1 at pH ≥ 9. With an apparent rate constant of k_O3 = (1.8 ± 0.7) × 10³ M^-1 s^-1 at pH 8, STG can be considered to be readily degraded by ozonation of WWTP effluents. Ozone attacks the primary amine moiety of STG, leading to nitro-STG (TP 437) (the primary amine moiety is transformed into a nitro group). Furthermore, a diketone (TP 406) was formed, which can be further degraded by ozone. Lab-scale and pilot-scale experiments on ozonation of WWTP effluents confirmed that the ozone attack of STG was incomplete even at high ozone doses of 1.7 and 0.9 mg O₃/mg DOC, respectively. These experiments confirmed that nitro-STG was formed as the main TP in the wastewater matrix. Two other TPs, TP 421c and TP 206b, were also detected, albeit with low intensities.

A Physiologically-Based Quantitative Systems Pharmacology Model of the Incretin Hormones GLP-1 and GIP and the DPP4 Inhibitor Sitagliptin

Incretin hormones glucagon‐like peptide‐1 (GLP‐1) and glucose‐dependent insulinotropic polypeptide (GIP) play a major role in regulation of postprandial glucose and the development of type 2 diabetes mellitus. The incretins are rapidly metabolized, primarily by the enzyme dipeptidyl‐peptidase 4 (DPP4), and the neutral endopeptidase (NEP), although the exact metabolization pathways are unknown. We developed a physiologically‐based (PB) quantitative systems pharmacology model of GLP‐1 and GIP and their metabolites that describes the secretion of the incretins in response to intraduodenal glucose infusions and their degradation by DPP4 and NEP. The model describes the observed data and suggests that NEP significantly contributes to the metabolization of GLP‐1, and the traditional assays for the total GLP‐1 and GIP forms measure yet unknown entities produced by NEP. We further extended the model with a PB pharmacokinetics/pharmacodynamics model of the DPP4 inhibitor sitagliptin that allows predictions of the effects of this medication class on incretin concentrations.

Metabolism and in vitro drug-drug interaction assessment of viloxazine

Viloxazine is currently being developed as a treatment for attention deficit/hyperactivity disorder (ADHD). The aim of these studies is to update the understanding of the rat and human metabolism and the in vitro drug-drug interaction profile of viloxazine to a degree where it meets current regulatory standards for such investigations. In vivo absorption-distribution-metabolism-excretion (ADME) studies demonstrated that in humans 5-hydroxylation followed by glucuronidation is the major metabolic route. This route was also seen as a minor route in rats where the major route is O-deethylation with subsequent sulfation. In humans, the 5-hydoxylation pathway is mediated by CYP2D6. An estimate for the fraction of the metabolism via this pathway suggests a PM/EM difference of <2-fold, making it highly unlikely that this will be an issue of clinical significance. Viloxazine forms a unique N-carbamoyl glucuronide in humans. The chemical reactivity characteristics of this metabolite are similar to stable glucuronide conjugates and dissimilar from acyl glucuronides; therefore, it is regarded as a stable Phase II conjugate. In vitro drug-drug interaction (DDI) testing indicates that viloxazine is not a significant inhibitor or inducer of CYPs and transporters with the exception of CYP1A2.

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.

Is there enough evidence to classify cycloalkyl amine substituents as structural alerts?

Basic amine substituents provide several pharmacokinetic benefits relative to acidic and neutral functional groups, and have been extensively utilized as substituents of choice in drug design. On occasions, basic amines have been associated with off-target pharmacology via interactions with aminergic G-protein coupled receptors, ion-channels, kinases, etc. Structural features associated with the promiscuous nature of basic amines have been well-studied, and can be mitigated in a preclinical drug discovery environment. In addition to the undesirable secondary pharmacology, α-carbon oxidation of certain secondary or tertiary cycloalkyl amines can generate electrophilic iminium and aldehyde metabolites, potentially capable of covalent adduction to proteins or DNA. Consequently, cycloalkyl amines have been viewed as structural alerts (SAs), analogous to functional groups such as anilines, furans, thiophenes, etc., which are oxidized to reactive metabolites that generate immunogenic haptens by covalently binding to host proteins. Detailed survey of the literature, however, suggests that cases where preclinical or clinical toxicity has been explicitly linked to the metabolic activation of a cycloalkyl amine group are extremely rare. Moreover, there is a distinct possibility for the formation of electrophilic iminium/amino-aldehyde metabolites with numerous cycloalkyl amine-containing marketed drugs, since stable ring cleavage products have been characterized as metabolites in human mass balance studies. In the present work, a critical analysis of the evidence for and against the role of iminium ions/aldehydes as mediators of toxicity is discussed with a special emphasis on often time overlooked detoxication pathways of these reactive species to innocuous metabolites.

Effect of resveratrol on dipeptidyl peptidase-4 inhibitors pharmacokinetics: An in vitro and in vivo approach

Diabetes mellitus (DM) is a metabolic disorder with hyperglycemia being its hallmark symptom. The secondary symptom of DM is oxidative stress, which leads to the generation of free radicals. Diabetic nephropathy and neuropathy is the long-term effect of oxidative stress caused in DM, which leads to damage of kidneys and neurons respectively. Resveratrol (RES) is a phytochemical, found to be effective in the treatment of diabetic nephropathy and neuropathy. Due to its antioxidant property, it reduces the oxidative stress caused by DM. Dipeptidyl peptidase-4 (DPP-4) inhibitors are used for the treatment of type 2 DM. In vitro and in vivo data depicted that the metabolism of alogliptin (ALO), saxagliptin (SAX) and sitagliptin (SIT) were decreased in presence of RES while metabolism of teneligliptin (TEN) was not affected in presence of RES. The results show that the alteration of the pharmacokinetics of ALO, SAX and SIT was due to inhibition of CYP P450 by RES. Thus, there was a significant pharmacokinetic interaction between RES-ALO, RES-SAX and RES-SIT. Hence, a dose reduction is required when RES therapy is taken in combination with ALO, SAX and SIT as there is an increase in drug exposure, which might lead to toxicity.

Bioequivalence of Ertugliflozin/Sitagliptin Fixed-Dose Combination Tablets and Coadministration of Respective Strengths of Individual Components

A fixed-dose combination (FDC) tablet of ertugliflozin, a selective inhibitor of sodium-glucose cotransporter 2, and sitagliptin, a dipeptidyl peptidase-4 inhibitor, was developed for the treatment of patients with type 2 diabetes mellitus. Four studies were conducted under fasted conditions to demonstrate bioequivalence of ertugliflozin/sitagliptin FDC tablets and individual components at respective strengths when coadministered in healthy subjects. All studies had open-label, randomized, 2-period, 2-sequence, single-dose crossover designs. In each study 18 or 19 subjects were enrolled and received an ertugliflozin/sitagliptin FDC tablet (5 mg/50 mg, 5 mg/100 mg, 15 mg/50 mg, or 15 mg/100 mg) and corresponding strengths of ertugliflozin and sitagliptin coadministered as individual components. For both ertugliflozin and sitagliptin, the 90%CIs for the ratio (FDC:coadministration) of geometric means for area under the plasma concentration-time profile from time 0 extrapolated to infinite time, and maximum observed plasma concentration, were within acceptance criteria for bioequivalence (80% to 125%). All adverse events were mild in intensity. The 4 studies demonstrated that each strength of FDC tablet is bioequivalent to the respective dose of coadministered individual components. This indicates that the known efficacy and tolerability of ertugliflozin and sitagliptin when coadministered can be translated to the use of a FDC formulation.

Antidiabetic agents in patients with hepatic impairment

Chronic liver disease (CLD) often coexists with type 2 diabetes mellitus, making diabetes management a challenge to the clinician. It is well known that liver is the major site of drug metabolism, and, therefore, its impairment affects hepatic metabolism of many antidiabetic agents. Furthermore, patients with CLD have serious comorbidities such as impaired renal function, hypoalbuminemia, lactic acidosis, hypoglycemia and malnutrition, making their treatment even more difficult. On the other hand, most of the antidiabetic agents, with the exception of insulin, need dosage titration due to alterations to their pharmacokinetics in patients with CLD. For well-established antidiabetic treatments, like metformin and sulfonylureas there are studies regarding their dosage chance in these patients. However, despite the growing problem of management of diabetes in patients with CLD the existing literature data, especially on newer antidiabetic agents, are limited and, furthermore, no direct guidelines exist. Therefore, in the present review article we try to summarize the existing literature data regarding management of diabetes in patients with CLD.

A HILIC-MS/MS assay for the quantification of metformin and sitagliptin in human plasma and urine: A tool for studying drug transporter perturbation

This article describes the development and validation of a HILIC-MS/MS method for the simultaneous quantification of metformin and sitagliptin from human plasma and urine. The presented method uses quick sample preparation and fast chromatography allowing for high sample throughput. The quantification is performed using multi-reaction monitoring and ESI positive mode with stable isotope labelled internal standards for both metformin and sitagliptin. Excellent linearity in the selected calibrations ranges, low inter-day variability (CV% <6.7%), and high accuracy (95.5-104.1%) were obtained. Adequate retention was attained for both analytes by hydrophilic interaction liquid chromatography using a plain silica column in combination with a mobile phase composed of ammonium formate, acetonitrile, formic acid and water in gradient separation mode.

Assessment of the Drug Interaction Potential of Ertugliflozin With Sitagliptin, Metformin, Glimepiride, or Simvastatin in Healthy Subjects

Ertugliflozin, a sodium-glucose cotransporter 2 inhibitor for the treatment of adults with type 2 diabetes mellitus, is expected to be coadministered with sitagliptin, metformin, glimepiride, and/or simvastatin. Four separate open-label, randomized, single-dose, crossover studies were conducted in healthy adults to assess the potential pharmacokinetic interactions between ertugliflozin 15 mg and sitagliptin 100 mg (n = 12), metformin 1000 mg (n = 18), glimepiride 1 mg (n = 18), or simvastatin 40 mg (n = 18). Noncompartmental pharmacokinetic parameters derived from plasma concentration-time data were analyzed using mixed-effects models to assess interactions. Coadministration of sitagliptin, metformin, glimepiride, or simvastatin with ertugliflozin had no effect on area under the plasma concentration-time profile from time 0 to infinity (AUCinf ) or maximum observed plasma concentration (Cmax ) of ertugliflozin (per standard bioequivalence boundaries, 80% to 125%). Similarly, ertugliflozin did not have any impact on AUCinf or Cmax of sitagliptin, metformin, or glimepiride. AUCinf for simvastatin (24%) and simvastatin acid (30%) increased slightly after coadministration with ertugliflozin and was not considered clinically relevant. All treatments were well tolerated. The lack of clinically meaningful pharmacokinetic interactions demonstrates that ertugliflozin can be coadministered safely with sitagliptin, metformin, glimepiride, or simvastatin without any need for dose adjustment.

Current Progress in Pharmacogenetics of Second-Line Antidiabetic Medications: Towards Precision Medicine for Type 2 Diabetes

Precision medicine is a scientific and medical practice for personalized therapy based on patients’ individual genetic, environmental, and lifestyle characteristics. Pharmacogenetics and pharmacogenomics are also rapidly developing and expanding as a key element of precision medicine, in which the association between individual genetic variabilities and drug disposition and therapeutic responses are investigated. Type 2 diabetes (T2D) is a chronic metabolic disorder characterized by hyperglycemia mainly associated with insulin resistance, with the risk of clinically important cardiovascular, neurological, and renal complications. The latest consensus report from the American Diabetes Association and European Association for the Study of Diabetes (ADA-EASD) on the management of T2D recommends preferential use of glucagon-like peptide-1 (GLP-1) receptor agonists, sodium-glucose cotransporter-2 (SGLT2) inhibitors, and some dipeptidyl peptidase-4 (DPP-4) inhibitors after initial metformin monotherapy for diabetic patients with established atherosclerotic cardiovascular or chronic kidney disease, and with risk of hypoglycemia or body weight-related problems. In this review article, we summarized current progress on pharmacogenetics of newer second-line antidiabetic medications in clinical practices and discussed their therapeutic implications for precision medicine in T2D management. Several biomarkers associated with drug responses have been identified from extensive clinical pharmacogenetic studies, and functional variations in these genes have been shown to significantly affect drug-related glycemic control, adverse reactions, and risk of diabetic complications. More comprehensive pharmacogenetic research in various clinical settings will clarify the therapeutic implications of these genes, which may be useful tools for precision medicine in the treatment and prevention of T2D and its complications.

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.

Effects of Sitagliptin on Pancreatic Beta-Cells in Type 2 Diabetes With Sulfonylurea Treatment: A Prospective Randomized Study

Background

This prospective randomized, multicenter, open-label, comparative study was performed to analyze the effects of sitagliptin on glycemic control and maintenance of beta-cell function in patients with poorly controlled type 2 diabetes treated with low-dose glimepiride.

Methods

Forty-one patients with type 2 diabetes mellitus treated with low-dose glimepiride (≤ 2 mg/day) were prospectively enrolled in this study (age: 20 - 75 years; hemoglobin A1c (HbA1c): 7.4- 9.4%). The patients were randomized into two groups: the glimepiride (G) group, in which glimepiride dose was increased gradually to 6 mg/day, and the sitagliptin (S) group, in which sitagliptin was added at a dose of 50 mg/day.

Results

HbA1c level was significantly decreased after 24 weeks, but not 12 weeks, in the G group, while a significant decrease was seen after 12 weeks in the S group. Although there were no significant differences in HbA1c level at 24 weeks between the two groups (P = 0.057). The overall trend of changes in HbA1c level suggested that the glucose-lowering effects were superior in the S group. Furthermore, a significant change in fasting glucose was seen in the S group, but not in the G group. Glycemic control target was achieved in 36.7% and 16.7% patients in the S group and the G group, respectively. The proinsulin/insulin (P/I) ratio was significantly increased in the G group, whereas it tended to decrease in the S group. After 24 weeks of treatment, no significant difference was observed in the P/I ratio between the two groups, whereas a significant difference was noted in the ΔP/I (amount of change). Albuminuria tended to increase in the G group compared with the S group.

Conclusion

The results of the present study suggested that sitagliptin effectively lowered hyperglycemia and that it may have a protective effect on pancreatic beta-cells when combined with a low dose of glimepiride. Therefore, sitagliptin may represent a useful combination therapy with low-dose sulfonylurea, not only for achieving glycemic control but also for protection of pancreatic beta-cells.

The role of mass spectrometry in studies of glycation processes and diabetes management

In the last decade, mass spectrometry has been widely employed in the study of diabetes. This was mainly due to the development of new, highly sensitive, and specific methods representing powerful tools to go deep into the biochemical and pathogenetic processes typical of the disease. The aim of this review is to give a panorama of the scientifically valid results obtained in this contest. The recent studies on glycation processes, in particular those devoted to the mechanism of production and to the reactivity of advanced glycation end products (AGEs, AGE peptides, glyoxal, methylglyoxal, dicarbonyl compounds) allowed to obtain a different view on short and long term complications of diabetes. These results have been employed in the research of effective markers and mass spectrometry represented a precious tool allowing the monitoring of diabetic nephropathy, cardiovascular complications, and gestational diabetes. The same approaches have been employed to monitor the non-insulinic diabetes pharmacological treatments, as well as in the discovery and characterization of antidiabetic agents from natural products. © 2018 Wiley Periodicals, Inc. Mass Spec Rev 38:112-146, 2019.

Eugenia jambolana extract reduces the systemic exposure of Sitagliptin and improves conditions associated with diabetes: A pharmacokinetic and a pharmacodynamic herb-drug interaction study

Eugenia jambolana (EJ) is an Indian traditional herb widely used for the treatment of diabetes mellitus. This herb is globally marketed as single or multi herb formulations. Many diabetes patients consume EJ extract oral hypoglycemic drugs together. This calls for a need to assess risks versus benefit of this co-administration.

In present investigation, pharmacodynamic and pharmacokinetic interactions of aqueous extract of EJ seeds at the dose of 400 mg/kg are studied with 10 mg/kg of oral hypoglycaemic drug sitagliptin (SITA) by co-administrating them for 28 days in streptozotocin (STZ) induced diabetic rats. The pharmacokinetic parameters of SITA were determined using HPLC-ESI-MS/MS and it was found that the combination treatment reduces the systemic exposure of SITA by showing 38.70% reduction in concentration maximum (Cmax) and 22.40% reduction in area under curve (AUC). Despite low levels of SITA, the combination demonstrated a significant reduction in blood glucose level when compared with individual drug and individual extract administered groups during pharmacodynamic study. In addition, the liver function, the kidney function and the lipid parameters were found to be significantly improved and beneficial effects were found with respect to food intake and water intake and urine output in case of combination treatment groups when compared with individual treatment groups. Histopathological examination of pancreatic tissue suggests its significant recovery of having normal acinus with better cell protection in combination treatment. In conclusion, the combination treatment demonstrated reduced systemic exposure of SITA without compromising on its antihyperglycemic activity and improvement in conditions associated with diabetes.

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.

A high-performance liquid chromatography-tandem mass spectrometry method for simultaneous determination of imigliptin, its five metabolites and alogliptin in human plasma and urine and its application to a multiple-dose pharmacokinetic study

Imigliptin is a novel DPP-4 inhibitor, designed to treat type 2 diabetes mellitus (T2DM). A selective and sensitive method was developed using high performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) to simultaneously quantify imigliptin, its five metabolites, and alogliptin in human plasma and urine. Solid-phase extraction (SPE) and direct dilution were used to extract imigliptin, its five metabolites, alogliptin from plasma and urine, respectively. The extracts were injected onto a SymmetryShield RP₈ column with a gradient elution of methanol and water containing 10 mM ammonium formate (pH = 7). Ionization of all analytes was performed using an electrospray ionization (ESI) source in positive mode and detection was carried out with multiple reaction monitoring (MRM) mode. The results revealed that the method had excellent selectivity and linearity. Inter- and intra-batch precisions of all analytes were less than 15% and the accuracies were within 85%-115% for both plasma and urine. The sensitivity, matrix effect, extraction recovery, linearity, and stabilities were validated for all analytes in human plasma and urine. In conclusion, the validation results showed that this method was robust, specific, and sensitive and it can successfully applied to a pharmacokinetic study of Chinese T2DM subjects after oral dose of imigliptin and alogliptin.

Metabolites characterization of a novel DPP-4 inhibitor, imigliptin in humans and rats using ultra-high performance liquid chromatography coupled with synapt high-resolution mass spectrometry

Imigliptin has been reported as a novel dipeptidyl-peptidase-IV (DPP-4) inhibitor to treat type 2 Diabetes Mellitus (T2DM), and is currently being tested in clinical trials. In the first human clinical study, imigliptin was well tolerated and proved to be a potent DPP-4 inhibitor. Considering its potential therapeutic benefits and promising future, it is of great importance to study the metabolite profiles in the early stage of drug development. In the present study, a robust and reliable analytical method based on the ultra-high performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UHPLC/Q-TOF MS) method combined with MassLynx software was established to investigate the characterization of metabolites of imigliptin in human and rat plasma, urine and feces after oral administration. As a result, a total of 9 metabolites were identified in humans, including 6, 9 and 8 metabolites in human plasma, urine, and feces, respectively. A total of 11 metabolites were identified in rats, including 7, 10 and 8 metabolites in rat plasma, urine, and feces, respectively. In addition, 6 of the metabolites detected in humans and rats were phase I metabolites, including demethylation, carboxylation, hydroxylation and dehydrogenation metabolites, and 5 of the metabolites were phase II metabolites, including acetylation and glucuronidation. There was no human metabolite detected compared to those in rats. The major metabolites detected in human plasma (M1 and M2) were products resulting from acetylation, and hydroxylation followed by dehydrogenation. M1 was the major metabolite in rat plasma. M2 and the parent drug were the major drug-related substances in human urine. The parent drug was the major drug-related substances in rat urine. M2, M5 (hydroxylation product) and M6 (2 × hydroxylation and acetylation product) were the predominant metabolites in human feces. M2 and M5 were the major metabolites in rat feces. In addition, renal clearance was the major route of excretion for imigliptin.

Evaluation of pharmacokinetic and pharmacodynamic parameters following single dose of sitagliptin in healthy Indian males

PURPOSE

Sitagliptin, a dipeptidyl peptidase (DPP)-IV inhibitor approved for the treatment of type 2 diabetes, is reported to be more efficacious in Indian patients than non-Indian patient population. The objective of the study was to evaluate pharmacokinetic and pharmacodynamic (PK/PD) parameters of single-dose sitagliptin 100 mg (Januvia) in healthy Indian male participants.

METHOD

In a randomised, single-dose, open-label, three-treatment, three-period, three-sequence, crossover bioavailability study, 18 healthy male participants received single-dose of sitagliptin under fasted and fed conditions. PK parameters (C_max, T_max, AUC_0-∞ and t_1/2) were determined using Phoenix WinNonlin software. PD parameters [DPP-IV inhibition, active glucagon-like peptide-1 (GLP-1) and insulin] were determined using established methods.

RESULTS

PK parameters expressed in mean (SD) were C_max 491.7 (135.9) ng/mL; AUC_0-∞ 4256.1 (509.9) ng· hr/mL, T_max 2.9 (1.0) hr and t_1/2 10.4 (3.0) hr. The weighted average (WA) plasma DPP-4 inhibition over 24 h was 89.6% and WA of plasma active GLP-1 over 2 h after standardised meal (geometric mean ratio) was 11.1 (9.9) pM/L which is two- to- four fold higher compared to that reported in other populations. The mean average (SD) AUC of plasma insulin over 2 h of standardised meal was 47.9 (24.9) μIU/mL.

CONCLUSION

Although, there are differences in pharmacokinetic parameters, no clinically meaningful differences were observed with respect to DPP-IV inhibition between Indian and non-Indian population.

Physiologically Based Pharmacokinetic Modeling in Lead Optimization. 1. Evaluation and Adaptation of GastroPlus To Predict Bioavailability of Medchem Series

When medicinal chemists need to improve bioavailability (%F) within a chemical series during lead optimization, they synthesize new series members with systematically modified properties mainly by following experience and general rules of thumb. More quantitative models that predict %F of proposed compounds from chemical structure alone have proven elusive. Global empirical %F quantitative structure-property (QSPR) models perform poorly, and projects have too little data to train local %F QSPR models. Mechanistic oral absorption and physiologically based pharmacokinetic (PBPK) models simulate the dissolution, absorption, systemic distribution, and clearance of a drug in preclinical species and humans. Attempts to build global PBPK models based purely on calculated inputs have not achieved the <2-fold average error needed to guide lead optimization. In this work, local GastroPlus PBPK models are instead customized for individual medchem series. The key innovation was building a local QSPR for a numerically fitted effective intrinsic clearance (CL_loc). All inputs are subsequently computed from structure alone, so the models can be applied in advance of synthesis. Training CL_loc on the first 15-18 rat %F measurements gave adequate predictions, with clear improvements up to about 30 measurements, and incremental improvements beyond that.

Short article: A randomized-controlled study of sitagliptin for treating diabetes mellitus complicated by nonalcoholic fatty liver disease

BACKGROUND

This study aimed to evaluate the efficacy and safety of sitagliptin for treating Chinese patients with type 2 diabetes mellitus (T2DM) with nonalcoholic fatty liver disease (NAFLD).

METHODS

In total, 72 Chinese T2DM patients with NAFLD were divided randomly into two groups of 36 patients each group. All 72 patients were assigned to receive either sitagliptin or diet and exercise for 52 weeks between January 2013 and December 2015. The outcomes' measurements included serum levels of hemoglobin A1c, fasting plasma glucose, aspartate aminotransferase, and alanine aminotransferase.

RESULTS

Seventy patients completed the study. Sitagliptin showed greater efficacy than the diet and exercise in decreasing the hemoglobin A1c and fasting plasma glucose levels at weeks 13, 26, 39, and 52. In addition, no significant changes in the average aspartate aminotransferase and alanine aminotransferase levels were found during the 52-week follow-up in both the sitagliptin and the control groups.

CONCLUSION

The results of this study indicate that sitagliptin is an effective and safe treatment for patients with T2DM and NAFLD.

Non-insulin anti-diabetic drugs: An update on pharmacological interactions

Nowadays, the goal in the management of type 2 diabetes mellitus (T2DM) remains personalized control of glucose. Since less than 50% of patients with T2DM achieve glycemic treatment goal and most of them take medications for comorbidities associated to T2DM, drug interactions, namely pharmacokinetic and pharmacodynamic interactions, may enhance or reduce the effect of compounds involved in hyperglycemia. Hence, clinicians should be aware of the severe complications in T2DM patients in case of a concomitant use of these medications. It is within this context that this review aims to evaluate the effect of a second drug on the pharmacokinetic of these compounds which may lead, along with several pharmacodynamic interactions, to severe clinical complications, i.e., hypoglycemia. Available drugs already approved in Europe, USA and Japan have been included.

Role of Cytochrome P450 2C8 in Drug Metabolism and Interactions

During the last 10-15 years, cytochrome P450 (CYP) 2C8 has emerged as an important drug-metabolizing enzyme. CYP2C8 is highly expressed in human liver and is known to metabolize more than 100 drugs. CYP2C8 substrate drugs include amodiaquine, cerivastatin, dasabuvir, enzalutamide, imatinib, loperamide, montelukast, paclitaxel, pioglitazone, repaglinide, and rosiglitazone, and the number is increasing. Similarly, many drugs have been identified as CYP2C8 inhibitors or inducers. In vivo, already a small dose of gemfibrozil, i.e., 10% of its therapeutic dose, is a strong, irreversible inhibitor of CYP2C8. Interestingly, recent findings indicate that the acyl-β-glucuronides of gemfibrozil and clopidogrel cause metabolism-dependent inactivation of CYP2C8, leading to a strong potential for drug interactions. Also several other glucuronide metabolites interact with CYP2C8 as substrates or inhibitors, suggesting that an interplay between CYP2C8 and glucuronides is common. Lack of fully selective and safe probe substrates, inhibitors, and inducers challenges execution and interpretation of drug-drug interaction studies in humans. Apart from drug-drug interactions, some CYP2C8 genetic variants are associated with altered CYP2C8 activity and exhibit significant interethnic frequency differences. Herein, we review the current knowledge on substrates, inhibitors, inducers, and pharmacogenetics of CYP2C8, as well as its role in clinically relevant drug interactions. In addition, implications for selection of CYP2C8 marker and perpetrator drugs to investigate CYP2C8-mediated drug metabolism and interactions in preclinical and clinical studies are discussed.

Pharmacogenetic studies update in type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a silent progressive polygenic metabolic disorder resulting from ineffective insulin cascading in the body. World-wide, about 415 million people are suffering from T2DM with a projected rise to 642 million in 2040. T2DM is treated with several classes of oral antidiabetic drugs (OADs) viz. biguanides, sulfonylureas, thiazolidinediones, meglitinides, etc. Treatment strategies for T2DM are to minimize long-term micro and macro vascular complications by achieving an optimized glycemic control. Genetic variations in the human genome not only disclose the risk of T2DM development but also predict the personalized response to drug therapy. Inter-individual variability in response to OADs is due to polymorphisms in genes encoding drug receptors, transporters, and metabolizing enzymes for example, genetic variants in solute carrier transporters (SLC22A1, SLC22A2, SLC22A3, SLC47A1 and SLC47A2) are actively involved in glycemic/HbA1c management of metformin. In addition, CYP gene encoding Cytochrome P450 enzymes also play a crucial role with respect to metabolism of drugs. Pharmacogenetic studies provide insights on the relationship between individual genetic variants and variable therapeutic outcomes of various OADs. Clinical utility of pharmacogenetic study is to predict the therapeutic dose of various OADs on individual basis. Pharmacogenetics therefore, is a step towards personalized medicine which will greatly improve the efficacy of diabetes treatment.

Pharmacological Actions of Glucagon-Like Peptide-1, Gastric Inhibitory Polypeptide, and Glucagon

Glucagon family of peptide hormones is a group of structurally related brain-gut peptides that exert their pleiotropic actions through interactions with unique members of class B1 G protein-coupled receptors (GPCRs). They are key regulators of hormonal homeostasis and are important drug targets for metabolic disorders such as type-2 diabetes mellitus (T2DM), obesity, and dysregulations of the nervous systems such as migraine, anxiety, depression, neurodegeneration, psychiatric disorders, and cardiovascular diseases. The current review aims to provide a detailed overview of the current understanding of the pharmacological actions and therapeutic advances of three members within this family including glucagon-like peptide-1 (GLP-1), gastric inhibitory polypeptide (GIP), and glucagon.

Influence of the rs738409 polymorphism in patatin-like phospholipase 3 on the treatment efficacy of non-alcoholic fatty liver disease with type 2 diabetes mellitus

AIM

A genome-wide association study revealed that the single nucleotide polymorphism (SNP) rs738409 in the patatin-like phospholipase 3 gene (PNPLA3) was strongly associated with non-alcoholic fatty liver disease (NAFLD). Recent pilot studies investigated the effects of dipeptidyl peptidase-4 inhibitors on liver function and glucose metabolism in NAFLD with type 2 diabetes mellitus (DM). We herein evaluated the efficacy of alogliptin in NAFLD patients with type 2 DM as well as the relationship between genotypes at rs738409 in PNPLA3 and treatment efficacy.

METHODS

Forty-one biopsy-proven NAFLD patients with type 2 DM treated with 25 mg/day alogliptin were retrospectively enrolled. SNP rs738409 in PNPLA3 was present in all patients. Clinical data were measured before and after the treatment.

RESULTS

Average hemoglobin A1c (HbA1c) levels mostly remained unchanged. Moreover, significant changes were not noted in the levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) during the follow-up period. A positive correlation was observed between improvements in HbA1c (ΔHbA1c) levels and changes in AST (ΔAST) and ALT (ΔALT) levels (r = 0.325 and 0.439, respectively). Patients with the risk allele (G-allele) showed more positive correlation between ΔHbA1c and changes in transaminase. Furthermore, improvements in the levels of total cholesterol, triglycerides and hyaluronic acid were significantly greater in G-allele patients in the weight loss group.

CONCLUSION

The treatment of NAFLD with type 2 DM with alogliptin contributed to the amelioration of NAFLD. Our results suggested that differences in the PNPLA3 risk allele affected the therapeutic effects of this treatment.

In Vitro Metabolic Pathways of the New Anti-Diabetic Drug Evogliptin in Human Liver Preparations

Evogliptin ((R)-4-((R)-3-amino-4-(2,4,5-trifluorophenyl)butanoyl)-3-(tert-butoxymethyl)-piperazin-2-one), is a new dipeptidyl peptidase IV inhibitor used for the treatment of type II diabetes mellitus. The in vitro metabolic pathways of evogliptin were identified in human hepatocytes, liver microsomes, and liver S9 fractions using liquid chromatography-Orbitrap mass spectrometry (LC-HRMS). Five metabolites of evogliptin-4-oxoevogliptin (M1), 4(S)-hydroxyevogliptin (M2), 4(R)-hydroxyevogliptin (M3), 4(S)-hydroxyevogliptin glucuronide (M4), and evogliptin N-sulfate (M5)—were identified in human liver preparations by comparison with authentic standards. We characterized the cytochrome P450 (CYP) enzymes responsible for evogliptin hydroxylation to 4(S)-hydroxyevogliptin (M2) and 4(R)-hydroxyevogliptin (M3) and the UGT enzymes responsible for glucuronidation of 4(S)-hydroxyevogliptin (M2) to 4(S)-hydroxy-evogliptin glucuronide (M4). CYP3A4/5 played the major role in the hydroxylation of evogliptin to 4(S)-hydroxyevogliptin (M2) and 4(R)-hydroxyevogliptin (M3). Glucuronidation of 4(S)-hydroxy-evogliptin (M2) to 4(S)-hydroxyevogliptin glucuronide (M4) was catalyzed by the enzymes UGT2B4 and UGT2B7. These results suggest that the interindividual variability in the metabolism of evogliptin in humans is a result of the genetic polymorphism of the CYP and UGT enzymes responsible for evogliptin metabolism.

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.

Comparison of vildagliptin and sitagliptin in patients with type 2 diabetes and severe renal impairment: a randomised clinical trial

AIMS/HYPOTHESIS

There are limited data comparing dipeptidyl peptidase-4 (DPP-4) inhibitors directly. We compared the safety and efficacy of vildagliptin and sitagliptin in patients with type 2 diabetes and severe renal impairment (RI).

METHODS

This study was a parallel-arm, randomised, multicentre, double-blind, 24 week study conducted in 87 centres across Brazil and the USA. Patients with type 2 diabetes, either drug naive or treated with any glucose-lowering agents, who had inadequate glycaemic control (HbA1c 6.5-10.0% [48-86 mmol/mol]) and an estimated GFR <30 ml min(-1) [1.73 m](-2) were randomised (via interactive voice response technology) to vildagliptin 50 mg once daily or sitagliptin 25 mg once daily. These doses are recommended in this patient population and considered maximally effective. Participants, investigators and the sponsor were blinded to group assignment. Efficacy endpoints included change in HbA1c and fasting plasma glucose (FPG) at all visits and the primary safety endpoint was assessment of treatment-emergent adverse events.

RESULTS

In total, 148 patients were randomised, 83 to vildagliptin and 65 to sitagliptin. All patients were analysed. After 24 weeks, the adjusted mean change in HbA1c was -0.54% (5.9 mmol/mol) from a baseline of 7.52% (59 mmol/mol) with vildagliptin and -0.56% (6.1 mmol/mol) from a baseline of 7.80% (62 mmol/mol) with sitagliptin (p = 0.874). FPG decreased by 0.47 ± 0.37 mmol/l with vildagliptin and increased by 0.16 ± 0.43 mmol/l with sitagliptin (p = 0.185). Both treatments were well tolerated with overall similar safety profiles.

CONCLUSIONS/INTERPRETATION

At their recommended doses for severe RI, vildagliptin (50 mg once daily) compared with sitagliptin (25 mg once daily) demonstrated similar efficacy and both drugs were well tolerated. This study provides further support for the use of DPP-4 inhibitors in patients with severe RI.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00616811 (completed)

FUNDING

This study was planned and conducted by Novartis.

Diabetes therapies in hemodialysis patients: Dipeptidase-4 inhibitors

Although several previous studies have been published on the effects of dipeptidase-4 (DPP-4) inhibitors in diabetic hemodialysis (HD) patients, the findings have yet to be reviewed comprehensively. Eyesight failure caused by diabetic retinopathy and aging-related dementia make multiple daily insulin injections difficult for HD patients. Therefore, we reviewed the effects of DPP-4 inhibitors with a focus on oral antidiabetic drugs as a new treatment strategy in HD patients with diabetes. The following 7 DPP-4 inhibitors are available worldwide: sitagliptin, vildagliptin, alogliptin, linagliptin, teneligliptin, anagliptin, and saxagliptin. All of these are administered once daily with dose adjustments in HD patients. Four types of oral antidiabetic drugs can be administered for combination oral therapy with DPP-4 inhibitors, including sulfonylureas, meglitinide, thiazolidinediones, and alpha-glucosidase inhibitor. Nine studies examined the antidiabetic effects in HD patients. Treatments decreased hemoglobin A1c and glycated albumin levels by 0.3% to 1.3% and 1.7% to 4.9%, respectively. The efficacy of DPP-4 inhibitor treatment is high among HD patients, and no patients exhibited significant severe adverse effects such as hypoglycemia and liver dysfunction. DPP-4 inhibitors are key drugs in new treatment strategies for HD patients with diabetes and with limited choices for diabetes treatment.

Pharmacokinetics in patients with chronic liver disease and hepatic safety of incretin-based therapies for the management of type 2 diabetes mellitus

Patients with type 2 diabetes mellitus have an increased risk of chronic liver disease (CLD) such as non-alcoholic fatty liver disease and steatohepatitis, and about one-third of cirrhotic patients have diabetes. However, the use of several antidiabetic agents, such as metformin and sulphonylureas, may be a concern in case of hepatic impairment (HI). New glucose-lowering agents targeting the incretin system are increasingly used for the management of type 2 diabetes. Incretin-based therapies comprise oral inhibitors of dipeptidyl peptidase-4 (DPP-4) (gliptins) or injectable glucagon-like peptide-1 (GLP-1) receptor agonists. This narrative review summarises the available data regarding the use of both incretin-based therapies in patients with HI. In contrast to old glucose-lowering agents, they were evaluated in specifically designed acute pharmacokinetic studies in patients with various degrees of HI and their hepatic safety was carefully analysed in large clinical trials. Only mild changes in pharmacokinetic characteristics of DPP-4 inhibitors were observed in patients with different degrees of HI, presumably without major clinical relevance. GLP-1 receptor agonists have a renal excretion rather than liver metabolism. Specific pharmacokinetic data in patients with HI are only available for liraglutide. No significant changes in liver enzymes were reported with DPP-4 inhibitors or GLP-1 receptor agonists, alone or in combination with various other glucose-lowering agents, in clinical trials up to 2 years in length. On the contrary, preliminary data suggested that incretin-based therapies may be beneficial in patients with CLD, more particularly in the presence of non-alcoholic fatty liver disease. Nevertheless, caution should be recommended, especially in patients with advanced cirrhosis, because of a lack of clinical experience with incretin-based therapies in these vulnerable patients.

Quantitative Rationalization of Gemfibrozil Drug Interactions: Consideration of Transporters-Enzyme Interplay and the Role of Circulating Metabolite Gemfibrozil 1-O-β-Glucuronide

Gemfibrozil has been suggested as a sensitive cytochrome P450 2C8 (CYP2C8) inhibitor for clinical investigation by the U.S. Food and Drug Administration and the European Medicines Agency. However, gemfibrozil drug-drug interactions (DDIs) are complex; its major circulating metabolite, gemfibrozil 1-O-β-glucuronide (Gem-Glu), exhibits time-dependent inhibition of CYP2C8, and both parent and metabolite also behave as moderate inhibitors of organic anion transporting polypeptide 1B1 (OATP1B1) in vitro. Additionally, parent and metabolite also inhibit renal transport mediated by OAT3. Here, in vitro inhibition data for gemfibrozil and Gem-Glu were used to assess their impact on the pharmacokinetics of several victim drugs (including rosiglitazone, pioglitazone, cerivastatin, and repaglinide) by employing both static mechanistic and dynamic physiologically based pharmacokinetic (PBPK) models. Of the 48 cases evaluated using the static models, about 75% and 98% of the DDIs were predicted within 1.5- and 2-fold of the observed values, respectively, when incorporating the interaction potential of both gemfibrozil and its 1-O-β-glucuronide. Moreover, the PBPK model was able to recover the plasma profiles of rosiglitazone, pioglitazone, cerivastatin, and repaglinide under control and gemfibrozil treatment conditions. Analyses suggest that Gem-Glu is the major contributor to the DDIs, and its exposure needed to bring about complete inactivation of CYP2C8 is only a fraction of that achieved in the clinic after a therapeutic gemfibrozil dose. Overall, the complex interactions of gemfibrozil can be quantitatively rationalized, and the learnings from this analysis can be applied in support of future predictions of gemfibrozil DDIs.