A concise review of the bioanalytical methods for the quantitation of sitagliptin, an important dipeptidyl peptidase-4 (DPP4) inhibitor, utilized for the characterization of the drug

In vitro study and pharmacokinetic evaluation of sitagliptin phosphate enantiomers in rat plasma

Background: A chiral HPLC technique was developed to determine sitagliptin phosphate enantiomers in rat plasma in compliance with US FDA regulations. Methods & results: The technique used a Phenomenex column with a mobile phase consisting of a 60:35:5 (v/v/v) blend of pH4, 10-mM ammonium acetate buffer, methanol and 0.1% formic acid in Millipore water. The precision for both (R) and (S) sitagliptin phosphate varied between 0.246 and 1.246%, while the accuracy was 99.6-100.1%. A glucose uptake assay was used to assess enantiomers in 3T3-L1 cell lines through flow cytometry. Conclusion: Investigation of the pharmacokinetic impacts of sitagliptin phosphate racemic enantiomers in rat plasma revealed notable contrasts in R and S enantiomers in female albino Wistar rats, suggesting enantioselectivity for sitagliptin phosphate.

Complete resonance assignment of a pharmaceutical drug at natural isotopic abundance from DNP-Enhanced solid-state NMR

Solid-state dynamic nuclear polarization enhanced magic angle spinning (DNP-MAS) NMR measurements coupled with density functional theory (DFT) calculations enable the full resonance assignment of a complex pharmaceutical drug molecule without the need for isotopic enrichment. DNP dramatically enhances the NMR signals, thereby making possible previously intractable two-dimensional correlation NMR spectra at natural abundance. Using inputs from DFT calculations, herein we describe a significant improvement to the structure elucidation process for complex organic molecules. Further, we demonstrate that a series of two-dimensional correlation experiments, including ¹⁵N-¹³C TEDOR, ¹³C-¹³C INADEQUATE/SARCOSY, ¹⁹F-¹³C HETCOR, and ¹H-¹³C HETCOR, can be obtained at natural isotopic abundance within reasonable experiment times, thus enabling a complete resonance assignment of sitagliptin, a pharmaceutical used for the treatment of type 2 diabetes.

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.

Enhanced Extraction Technique of Omarigliptin from Human Plasma-Applied to Biological Samples from Healthy Human Volunteers

Enhancing drug extraction from human plasma is a challenging approach that critically affects pharmacokinetic and any further clinical studies based on the drug C_min and C_max values. It also has a serious impact on the sensitivity and the lower limit of quantification (LLOQ) value of the bio-analytical methods. An advanced liquid chromatography tandem mass spectrometry (LC-MS/MS) bio-analytical method of omarigliptin (25-1000 nM) was established in human plasma using one-step liquid-liquid extraction. Alogliptin was used as an internal standard (IS) to attain good recovery and reproducibility while reducing the effects of the matrix. Enhanced plasma extraction of omarigliptin was successfully achieved with tertiary butyl methyl ether-diethyl ether (TBME-DEE) mixture as the extracting solvent, while using acetonitrile as the diluent solvent for the IS to effectively decrease the formed emulsion. Multiple Reaction Monitoring (MRM) of the transition pairs of m/z 399.2 to 153.0 for omarigliptin and m/z 340.2 to 116.0 for alogliptin was employed in positive Electro Spray Ionization (ESI) mode. Human plasma samples were collected after 1.5 h (t_max) of Marizev^® (12.5 mg) tablets administration to healthy human volunteers showing average concentration of 292.18 nM. Validation results were all satisfactory including successful stability studies with bias below 12%. The proposed study will be valuable for ethnicity comparison studies that will be commenced on omarigliptin in Egypt by the authors in prospective study, following the FDA recommends, to evaluate possible sub-group dissimilarities that include pharmacokinetic parameters.

Optimization and validation of a fluorogenic dipeptidyl peptidase 4 enzymatic assay in human plasma

During the development of a specific dipeptidyl peptidase 4 (DPP4) inhibitor to treat type 2 diabetes, a fluorogenic kinetic analysis for DPP4 enzymatic activity using Gly-Pro-Aminomethylcoumarin (AMC) as a substrate was optimized and validated for recombinant DPP4 and human plasma samples. The sensitivity, calibration curve, detection range, accuracy, precision, recovery efficiency, Km constant, short/long-term stability, and stability after freezing-thawing cycles were analyzed. DPP4 enzymatic activity (mU/min) was measured as the initial velocity (Vo) of the enzymatic reaction over time. The sensitivity of the Vo value was 14,488 mU/min for recombinant DPP4 and 17,995 mU/min for human plasma samples. The dynamic ranges of the calibration curve were linear and reliable between 1.11 × 10⁴-1.86 × 10⁶ mU/min of the mean Vo value and in the DPP4 concentration range of 23.4-3,000 ng/mL. The assay's accuracy and precision met acceptance criteria for all samples. Plasma DPP4 was stable under various storage temperatures, even after three freeze-thaw cycles. Our optimized, validated bioanalytic method for measuring DPP4 activity in plasma samples was successfully employed to evaluate the effect of evogliptin (DA-1229) tartrate, which irreversibly and dose-dependently inhibits DPP4 enzymatic activity, without the dilution effect of human plasma samples and irrespective of the co-treated metformin.

Quantitative Conductometric Determination of Sitagliptin, Linagliptin, Vildagliptin and Alogliptin by Applying the Concept of Drug-Metal Ion Interaction

Cost of analysis and length of analytical procedure are among the most concerning factors in drug analysis. As conductometric analysis has been considered to be relatively inexpensive analytical technique offering fast analysis of drugs, in this study our aim was to develop a rapid and cost-effective method for quantitative determination of sitagliptin, linagliptin, vildagliptin and alogliptin in bulk and dosage forms. The test drugs were allowed to complex with metal ion (Cu2+) in the titration cell, which resulted in the change of conductance of the solution. The corrected conductance was calculated and graph was plotted between corrected conductance and the volume of the analyte solution added. The point of maximum change in the corrected conductance was considered as end point of the titration. The method was found to be linear in the concentration range of 1.0 – 1.4 mM for all analytes with good correlation coefficient (R2 ˃ 0.999). The %RSD of the corrected conductance values were in the range of 0.046-1.837, while the recovery of analytes were within 100 ± 2%, indicating that the method was precise and accurate. The specificity of the method was demonstrated by no interference from blank and placebo. The method was successfully applied for quantitative analysis of all the drugs in the dosage forms. The current method has a major advantage that it provided easy, fast and economical analysis of sitagliptin, linagliptin, vildagliptin and alogliptin in bulk drugs and formulations using conductivity meter. KEYWORDS:

A Rapid and Sensitive Method for the Pharmacokinetic Study of Janumet (Sitagliptin and Metformin) Tablets by LC-MS/MS Coupled with Ion-Pair Solid Phase Extraction

Background:

As first-line treatments for diabetes, sitagliptin and metformin have been widely prescribed as a combination to enhance the therapeutic effect.

Objective:

To establish a methodology to simultaneously monitor the two drugs in vivo by a reversedphase Liquid Chromatography-Tandem Mass Spectrometric (LC-MS/MS) method.

Methods:

The two drugs were extracted from 50 μl human plasma by ion-pair solid phase extraction. The separation of the plasma samples was implemented on an Agilent Zorbax SB-CN column (150×4.6 mm, 5.0 µm). The mobile phase was the mixture (80:20, v/v) of methanol and 5.0 mM ammonium formate in water (pH 4.5). An ion trap spectrometer equipped with an electrospray ionization source was utilized to detect the elution in positive mode. Quantification of the analytes was achieved by Multiple Reaction Monitoring (MRM) using the transitions of m/z 408.3→235.1 for sitagliptin and m/z 130.1→ 60.2 for metformin.

Results:

Sitagliptin and metformin demonstrated good linearity among the range of 1.00-1000 ng/mL and 5.00-4000 ng/mL. The intra-day and inter-day investigations displayed precisions of ≤ 3.6% and an accuracy range of -7.5% to 6.0% for the two drugs. The mean recovery of the two drugs was 96.0% and 98.5%. Under mandatory storage conditions, both the drugs gave an acceptable stability. The throughput of the assay was found to be more than 100 plasma samples per day ascribed to the run time of 3.0 min for each sample.

Conclusion:

The developed method was successfully applied to a pharmacokinetic study for a fixeddose tablet formulation containing 50 mg sitagliptin and 500 mg metformin in 12 healthy volunteers.

Crosstalk between the Akt/mTORC1 and NF-κB signaling pathways promotes hypoxia-induced pulmonary hypertension by increasing DPP4 expression in PASMCs

Abnormal wound healing by pulmonary artery smooth muscle cells (PASMCs) promotes vascular remodeling in hypoxia-induced pulmonary hypertension (HPH). Increasing evidence shows that both the mammalian target of rapamycin complex 1 (mTORC1) and nuclear factor-kappa B (NF-κB) are involved in the development of HPH. In this study, we explored the crosstalk between mTORC1 and NF-κB in PASMCs cultured under hypoxic condition and in a rat model of hypoxia-induced pulmonary hypertension (HPH). We showed that hypoxia promoted wound healing of PASMCs, which was dose-dependently blocked by the mTORC1 inhibitor rapamycin (5-20 nM). In PASMCs, hypoxia activated mTORC1, which in turn promoted the phosphorylation of NF-κB. Molecular docking revealed that mTOR interacted with IκB kinases (IKKs) and that was validated by immunoprecipitation. In vitro kinase assays and mass spectrometry demonstrated that mTOR phosphorylated IKKα and IKKβ separately. Inhibition of mTORC1 decreased the level of phosphorylated IKKα/β, thus reducing the phosphorylation and transcriptional activity of NF-κB. Bioinformatics study revealed that dipeptidyl peptidase-4 (DPP4) was a target gene of NF-κB; DPP4 inhibitor, sitagliptin (10-500 μM) effectively inhibited the abnormal wound healing of PASMCs under hypoxic condition. In the rat model of HPH, we showed that NF-κB activation (at 3 weeks) was preceded by mTOR signaling activation (after 1 or 2 weeks) in lungs, and administration of sitagliptin (1-5 mg/kg every day, ig) produced preventive effects against the development of HPH. In conclusion, hypoxia activates the crosstalk between mTORC1 and NF-κB, and increased DPP4 expression in PASMCs that leads to vascular remodeling. Sitagliptin, a DPP4 inhibitor, exerts preventive effect against HPH.

Chitosan oligosaccharide improves the therapeutic efficacy of sitagliptin for the therapy of Chinese elderly patients with type 2 diabetes mellitus

Sitagliptin improves glycemic control in type 2 diabetes mellitus (T2DM) patients but its side effects are undesirable. Chitosan oligosaccharide (COS) is expected to improve the therapeutic result as a natural product. A total of 200 elderly T2DM patients were evenly assigned into four groups: sitagliptin group (SG), receiving sitagliptin 100 mg/day; COS group (CG), receiving COS 100 mg/day; combination therapy of sitagliptin and COS group (SCG), receiving both sitagliptin and COS 100 mg/day; and placebo group (PG), receiving placebo 100 mg/day. After 42-week therapy, biochemical indices and clinical parameters for the alterations from start points were analyzed. The related molecular mechanism was tested by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot at cell level. Lower risk of hypoglycemia was found in the SCG group when compared with SG and other groups (P<0.05). More patients from the SCG group than other groups attained hemoglobin A1c (HbA1c) reduction >2.5% (P<0.05). Weight reduction of 1.2±0.9, 2.6±0.8, 4.7±1.3, and 0.9±0.6 kg was observed in the patients from SG, CG, SCG, and PG groups, respectively (P<0.05). The combined treatment of COS and sitagliptin presented better therapeutic results by improving insulin sensitivity, lipid profile, adiponectin levels, and glucagon-like peptide 1 and reducing side effects, insulin resistance, HbA1c, body mass index, resistin, tumor necrosis factor (TNF)-α, and C-reactive protein (CRP) (P<0.05). qRT-PCR and Western blot analysis also showed that COS treatment reduced the levels of resistin, TNF-α, and CRP, and increased the level of adiponectin. The combination of COS and sitagliptin provided better glycemic control with fewer side effects and with more weight reduction in the elderly participants with T2DM.

Sitagliptin down-regulates retinol-binding protein 4 and reduces insulin resistance in gestational diabetes mellitus: a randomized and double-blind trial

Gestational diabetes mellitus (GDM) is a condition that affects increasing number of pregnant women worldwide. Sitagliptin was reported to alleviate symptoms of type 2 diabetes mellitus by reducing serum levels of retinol-binding protein 4 (RBP-4). We investigated the effectiveness of sitagliptin on insulin sensitivity parameters in GDM patients. Pregnant GDM women in the 2nd trimester were recruited for this study. Participants were then assigned randomly to sitagliptin treatment group or placebo treatment group, and administered sitagliptin or placebo daily for 16 weeks. Glucose and insulin profiles, as well as serum RBP-4 level, were measured at both baseline and end of the study. After 16 weeks of treatment, participants in the STL group exhibited significantly improved levels of fasting plasma glucose and serum insulin, homeostasis model of assessment of β cell function (HOMA-β) and insulin resistance (HOMA-IR), compared with those in the placebo group. Serum levels of RBP-4 were also markedly decreased in the sitagliptin treatment group, and more importantly it was positively correlated with improved insulin resistance parameters. Our study supports a potentially promising role of sitagliptin in improving insulin resistance by decreasing RBP-4 in GDM-affected women.