Major Metabolites In Human Plasma Research Articles

Cross-species drug metabolism and impact of metabolic stability testing under anaerobic condition on predicting pharmacokinetics of keto-enol containing compound in humans

After oral administration of [14C]-S-1360 in rats and dogs, [14C]-S-1360 was absorbed rapidly and the bioavailability was 93.7% in rats and 75.1% in dogs. Based on the results in animals, good systemic exposure would be expected in humans. In contrast to the expectation, the exposure was low in healthy volunteers compared to the exposure expected. In addition, human mass balance study using [14C]-S1360 revealed that a large amount of metabolites existed in human plasma. The major metabolites in human plasma were reduced metabolite (HP1) and S-1360 N-glucuronide, and they respectively accounted for approximately 30% of total AUC. Unchanged S-1360 accounted for only 14% of total AUC. The results showed that a significant difference between humans and animals were observed in metabolism of S-1360. Although S-1360 was stable in human hepatocytes under aerobic condition (approximately 84% remaining at 1 h), S-1360 was labile under anaerobic condition (approximately 55% remaining at 1 h). The present study revealed that the reductive metabolism pathways are the key metabolic pathway of S-1360, especially the metabolic stability test under anaerobic condition is important to predict pharmacokinetics of keto-enol containing compound, such as S-1360.

Simultaneous determination of UDCA and its major metabolites in human plasma with surrogate matrix by a rapid and specific LC-MS/MS method

A rapid, convenient, and specific liquid chromatography-tandem mass spectrometry method was developed and validated for the simultaneous quantification of ursodeoxycholic acid (UDCA), and its major metabolites, glycoursodeoxycholic acid (GUDCA) and tauroursodeoxycholic acid (TUDCA) in human plasma. Methanol was chosen as surrogate matrix for preparation the calibrators to establish calibration curves. Isotope internal standard was used for each analyte. After plasma samples were deproteinized with methanol, the post-treatment samples were analyzed on a ZORBAX SB-C18 column (2.1 × 50 mm, 1.8 μm) with 2 mM ammonium acetate and acetonitrile as mobile phase at a flow rate of 0.5 mL/min. Detection was performed on a triple quadrupole mass spectrometer operating in multiple reaction monitoring (MRM) employing negative ESI interface using API5500 triple quadrupole tandem mass spectrometer system, with the transitions set at m/z 391.4 → m/z 391.4, m/z 448.3 → m/z 73.9, m/z 498.4 → m/z 80.1, m/z 395.3 → m/z 395.3, m/z 453.3 → m/z 74.0, and m/z 503.2 → m/z 79.9 for UDCA, GUDCA, TUDCA, UDCA-d4, GUDCA-d5, and TUDCA-d5, respectively. The calibration curve ranges were 5.00–2500 ng/mL for UDCA and GUDCA and 0.500–250 ng/mL for TUDCA. The intra- and inter-day precision was within 7.00% in terms of relative standard deviation (RSD%) and the accuracy within 11.75% in terms of relative error. The selectivity, sensitivity, extraction recovery, matrix effect, dilution reliability, and stability were within the acceptable range. The method was successfully applied to a pharmacokinetic study in 12 healthy Chinese volunteers after oral administration of 250 mg UDCA.

Simultaneous quantification of 3′,4′-dimethoxy flavonol-3-O-glucoside and its major metabolite in human plasma by LC-MS/MS and its application to a clinical pharmacokinetic study

Hyperlipidemia is a disease characterized by abnormal blood lipid levels and is the leading risk factor for cardiovascular disease. 3′,4′-Dimethoxy flavonol-3-O-glucoside (abbreviated DF3G) is a new lipid-lowering drug created as a flavonoid structural analog. The principal metabolite of DF3G in human plasma is the aglycone glucuronide conjugate M2. The purpose of this study is to use liquid chromatography-tandem mass spectrometry to develop and validate a quantitative analysis method for DF3G and its metabolite M2 in human plasma, and to use the method to investigate the pharmacokinetics of DF3G and M2 in a clinical trial. This method employed DF3G-d6 as the internal standard, and plasma samples were processed by protein precipitation. Isocratic separation could accurately differentiate DF3G, M2, and DF3G-d6 from endogenous components in the matrix or other components in the samples, and endogenous components in the matrix had little impact on ionization efficiency. Positive electrospray ionization with multiple reaction monitoring (MRM) transitions of m/z 461.2 → 299.0 for DF3G, m/z 475.1 → 299.1 for M2 and m/z 467.1 → 305.1 for DF3G-d6 was used for quantification. The DF3G and M2 linear range for plasma were in the range of 4.00/4.00 ng/mL to 4000/4000 ng/mL. Both the analytes and the internal standard were stable regardless of whether they were in solution or plasma samples. The accuracy of the average concentration of the quality control samples was within 15% of the theoretical value, and the RSD was less than 15%. The method is rapid, accurate, straightforward, and precise. It is appropriate for the determination of DF3G and M2 concentrations in human plasma and has been successfully applied to determine the pharmacokinetic analysis in phase I clinical trials.

Development and validation of an LC-MS/MS method for the quantification of mescaline and major metabolites in human plasma

Mescaline is a psychedelic phenethylamine found in different species of cacti. Currently, mescaline’s acute subjective effects and pharmacokinetics are investigated in several modern clinical studies. Therefore, we developed a bioanalytical method for the rapid quantification of mescaline and its metabolites in human plasma. Mescaline and its metabolites 3,4,5-trimethoxyphenylacetic acid (TMPAA), N-acetyl mescaline (NAM), and 3,5-dimethoxy-4-hydroxyphenethylamine (4-desmethyl mescaline) were simultaneously analyzed by ultra-high performance liquid chromatography tandem mass spectrometry (LC-MS/MS). Optimal chromatographic separation was achieved with an Acquity Premier HSS T3 C18 column. The analytes were detected in positive ionization mode using scheduled multiple reaction monitoring. A single step extraction method was implemented to enable fast and automatable plasma sample preparation. An intra-assay accuracy between 84.9% and 106% and a precision of ≤ 7.33% was observed in three validation runs. Plasma was extracted by simple protein precipitation, resulting in a complete recovery (≥ 98.3%) and minor matrix effects (≤ 7.58%). No interference with endogenous matrix components could be detected in human plasma samples (n = 7). Importantly, method sensitivity sufficed for assessing pharmacokinetic parameters of mescaline in clinical study samples with lower limits of quantification of 12.5, 12.5, and 1.25 ng/mL for mescaline, TMPAA, and NAM, respectively. Nonetheless, 4-desmethyl mescaline could not be selectively quantified in pharmacokinetic samples due to interference with another mescaline metabolite. Overall, we developed and validated a reliable and very easy-to-use method for forensic applications as well as investigating the clinical pharmacokinetics of mescaline.

Simultaneous determination and pharmacokinetics study of valsartan, sacubitril and its major metabolite in human plasma, urine and peritoneal dialysis fluid in patients with end-stage renal disease by UPLC–MS/MS

Sacubitril/valsartan was indicated for the treatment of heart failure and hypertension in patients with end-stage renal disease on peritoneal dialysis therapy. Herein, a rapid, sensitive and robust method based on ultra-liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) was developed and validated for the determination of the concentrations of valsartan, sacubitril and its major metabolite LBQ657 in plasma, urine and peritoneal dialysis fluid. Samples were extracted from various biological fluids using protein precipitation. Extracts were subjected to UPLC–MS/MS with electrospray ionization in positive-ion mode. The developed method was fully validated over a concentration range of 8.00–8000 ng/mL for valsartan, 2.00–2000 ng/mL for sacubitril and 30.0–30,000 ng/mL for LBQ657 in plasma, 2.00–1000 ng/mL for valsartan, 1.00–500 ng/mL for sacubitril and 20.0–10000 ng/mL for LBQ657 in urine, and 0.200–100 ng/mL for valsartan, 0.0400–20.0 ng/mL for sacubitril and 2.00–1000 ng/mL for LBQ657 in peritoneal dialysis fluid. The intra- and inter-day precisions for all analytes in various matrices were less than 12.3%, and the intra- and inter-day accuracies results were all between 88.0% and 109.2%. All analytes were stable for at least 8 h at room temperature (25°C), five freeze–thaw cycles, and 37 days at −40°C and −80°C in plasma, urine and peritoneal dialysis fluid. In conclusion, this developed method is reliable, sensitive and specific for determining the concentrations of valsartan, sacubitril and LBQ657 in plasma, urine and peritoneal dialysis fluid. The assay was available to pilot the pharmacokinetics study of sacubitril/valsartan in patients with end-stage renal disease on peritoneal dialysis, and it could provide evidence that peritoneal dialysis had an effect on the clearance of sacubitril/valsartan.

LC–MS/MS assay of fluoropezil and its two major metabolites in human plasma: an application to pharmacokinetic studies

Background: LC-MS/MS methods were developed for pharmacokinetic analysis and verified to measure fluoropezil, a new AchE inhibitor for Alzheimer's disease treatment, and its two primary metabolites (N-debenzyl fluoride fluoropezil [M1] and N-oxidized fluoropezil [M11]) in human plasma. Methods & results: Analytes were extracted from 50μl plasma using protein precipitation and separated by HPLC using a bridged ethyl hybrid column and gradient elution procedure. Analytical detection was performed with a triple quadrupole mass spectrometer and electrospray ionization source in multiple reaction monitoring mode. The LC-MS/MS method was fully validated. The quantification linear ranges were 0.100-50.0ng/ml (fluoropezil), 0.0500-25.0ng/ml (M1) and 0.0500-25.0ng/ml (M11). Conclusion: A sensitive, reliable LC-MS/MS method was established and used successfully to explore the pharmacokinetics of fluoropezil.

Development and validation of UHPLC-MS/MS method for simultaneous quantification of escitalopram and its major metabolites in human plasma and its application in depressed patients

Escitalopram, one of the Selective Serotonin Reuptake Inhibitors (SSRIs), has been widely used in the patients with major depression. In this study, a simple, sensitive and rapid method was established and validated for simultaneous quantification of Escitalopram (S-CT), desmethyl escitalopram (S-DCT), didemethyl escitalopram (S-DDCT) and escitalopram N-Oxide (S-NOCT) in human plasma by ultra-high performance liquid chromatography-tandem with mass spectrometry (UHPLC-MS/MS). Analytes were extracted from plasma by utilizing protein precipitation and then separated on a Hypersil GOLD C18 column (50 mm × 2.1 mm, 1.9 µm). The mobile phase was water: acetonitrile (70:30, v/v) with 0.25% formic acid at a flow-rate of 0.3 mL/min, within a 5 min run time. The mass analysis used positive electro-spray ionization (ESI) in selection reaction monitoring (SRM). The calibration ranges of the analytes were: S-CT: 2.0–200.0 ng/mL, S-DCT: 1.0–100.0 ng/mL, S-DDCT: 0.5–50.0 ng/mL, S-NOCT: 0.2–20.0 ng/mL. The method has been fully validated for selectivity, linearity, accuracy, precision, matrix effect, recovery, stability and carry over and all the results met the admissible limits according to the the US Food and Drug Administration guidelines. Mean plasma concentration (ng/mL) of S-CT, S-DCT, S-DDCT and S-NOCT in 93 depressed patients were 51.10 ± 45.73, 10.32 ± 15.25, 1.53 ± 1.79 and 0.87 ± 0.94, respectively. it is the first time that a UHPLC-MS/MS method for simultaneous quantification of S-CT and its 3 metabolites in human plasma was established and validated.

Effect of Mild and Moderate Hepatic Impairment (Defined by Child-Pugh Classification and National Cancer Institute Organ Dysfunction Working Group Criteria) on Pexidartinib Pharmacokinetics.

Pexidartinib is a novel oral small‐molecule tyrosine kinase inhibitor targeting the colony‐stimulating factor 1 receptor. Pexidartinib undergoes extensive hepatic metabolism via multiple cytochrome P450 and uridine 5'‐diphospho‐glucuronosyl transferase enzymes, with ZAAD‐1006a as the only major metabolite in human plasma. As pexidartinib is extensively metabolized, hepatic impairment (HI) could lead to increased exposure to pexidartinib. The objective of the two phase 1, open‐label studies was to determine the pharmacokinetics of pexidartinib after a single 200‐mg dose in subjects with mild and moderate HI, based on Child–Pugh classification (PL3397‐A‐U123: 8 mild HI and 8 moderate HI vs 16 matched healthy controls) and National Cancer Institute Organ Dysfunction Working Group (NCI‐ODWG) criteria (PL3397‐A‐U129: 8 moderate HI versus 8 matched healthy controls [NCT04223635]). Based on Child–Pugh classification, exposure to pexidartinib (maximum observed concentration [Cmax], area under the plasma concentration–time curve up to the last measurable concentration [AUClast], and extrapolated to infinity [AUCinf]) was similar in subjects with mild and moderate HI and in respective matched healthy controls, whereas ZAAD‐1006a exposure (AUC) was approximately 27% to 28% and 41% to 48% higher in mild and moderate HI, respectively. According to NCI‐ODWG criteria, total pexidartinib exposure was 42% to 46% higher in subjects with moderate HI, compared with healthy controls, and total ZAAD‐1006a exposure was 70% to 79% higher for subjects with moderate HI, compared with matched healthy controls with normal hepatic function. These findings were used to develop appropriate dose recommendations in patients with hepatic impairment.

Development and Validation of UHPLC-MS/MS Method for Simultaneous Quantification of Escitalporam and its Major Metabolites in Human Plasma and its Application in Depressed Patients

Development and Validation of UHPLC-MS/MS Method for Simultaneous Quantification of Escitalporam and its Major Metabolites in Human Plasma and its Application in Depressed Patients

CYP2C8-Mediated Formation of a Human Disproportionate Metabolite of the Selective NaV1.7 Inhibitor DS-1971a, a Mixed Cytochrome P450 and Aldehyde Oxidase Substrate.

Predicting human disproportionate metabolites is difficult, especially when drugs undergo species-specific metabolism mediated by cytochrome P450s (P450s) and/or non-P450 enzymes. This study assessed human metabolites of DS-1971a, a potent Nav1.7-selective blocker, by performing human mass balance studies and characterizing DS-1971a metabolites, in accordance with the Metabolites in Safety Testing guidance. In addition, we investigated the mechanism by which the major human disproportionate metabolite (M1) was formed. After oral administration of radiolabeled DS-1971a, the major metabolites in human plasma were P450-mediated monoxidized metabolites M1 and M2 with area under the curve ratios of 27% and 10% of total drug-related exposure, respectively; the minor metabolites were dioxidized metabolites produced by aldehyde oxidase and P450s. By comparing exposure levels of M1 and M2 between humans and safety assessment animals, M1 but not M2 was found to be a human disproportionate metabolite, requiring further characterization under the Metabolites in Safety Testing guidance. Incubation studies with human liver microsomes indicated that CYP2C8 was responsible for the formation of M1. Docking simulation indicated that, in the formation of M1 and M2, there would be hydrogen bonding and/or electrostatic interactions between the pyrimidine and sulfonamide moieties of DS-1971a and amino acid residues Ser100, Ile102, Ile106, Thr107, and Asn217 in CYP2C8, and that the cyclohexane ring of DS-1971a would be located near the heme iron of CYP2C8. These results clearly indicate that M1 is the predominant metabolite in humans and a human disproportionate metabolite due to species-specific differences in metabolism. SIGNIFICANCE STATEMENT: This report is the first to show a human disproportionate metabolite generated by CYP2C8-mediated primary metabolism. We clearly demonstrate that DS-1971a, a mixed aldehyde oxidase and cytochrome P450 substrate, was predominantly metabolized by CYP2C8 to form M1, a human disproportionate metabolite. Species differences in the formation of M1 highlight the regio- and stereoselective metabolism by CYP2C8, and the proposed interaction between DS-1971a and CYP2C8 provides new knowledge of CYP2C8-mediated metabolism of cyclohexane-containing substrates.

LC-MS/MS determination of dutasteride and its major metabolites in human plasma

Dutasteride is a specific and selective inhibitor of both 5α-reductase isoforms used mainly in benign prostatic hyperplasia and lower urinary tract symptoms. Although the drug is extensively metabolized in humans, data on the concentrations of its main metabolites are lacking. There is also a lack of data on dutasteride stability in frozen plasma samples. Our method was used to determine dutasteride and its active metabolites: 4′-hydroxydutasteride, 6β-hydroxydutasteride, and 1,2-dihydrodutasteride in plasma after a single administration of 0.5 mg of dutasteride. We also assessed the long-term stability (two years in the freezer) of dutasteride in clinical samples. The developed method covered the range of 0.1–3.5 ng/mL for dutasteride and 0.08–1.2 ng/mL for 1,2-dihydrodutasteride, 4′-hydroxydutasteride, 6β-hydroxydutasteride. It was proved to be reliable as it met all validation criteria required by the European Medicine Agency for bioanalytical methods. 4′-hydroxydutasteride and 1,2-dihydrodutasteride concentrations in plasma were higher than 6β-hydroxydutasteride. Dutasteride was stable in the freezer for up to 2 years in clinical samples. Thus within 1014 days of storage (below − 65 °C), samples can be reanalyzed without the risk of unreliable results.

Simultaneous determination of forsythin and its major metabolites in human plasma via liquid chromatography-tandem mass spectrometry

Forsythiae suspensa is widely used in China as a traditional Chinese medicine. Forsythin is extracted from Forsythiae Fructus and has undergone phase II clinical trials as an antipyretic drug in China. The main metabolites of forsythin in human plasma are aglycone sulfate (KD-2-SO3H) and aglycone glucuronide (KD-2-Glc). In the present study, a sensitive and rapid liquid chromatography-tandem mass spectrometry (LC–MS/MS) method was developed and fully validated for the simultaneous analysis of forsythin, KD-2-Glc, and KD-2-SO3H, in human plasma. After precipitating proteins with methanol, these three analytes were separated on a Gemini-C18 column along with teniposide as an internal standard. Mass spectrometry detection, under multiple reaction monitoring, was then carried out in negative mode using the Triple Quad™ 6500+ LC–MS/MS system coupled with an electrospray ionization (ESI) ion source. The transitions of m/z 371.1→356.1 for forsythin, m/z 547.2→356.0 for KD-2-Glc and m/z 451.2→356.2 for KD-2-SO3H were chosen to effectively maintain the balance between selectivity and sensitivity. The developed method was linear over the following concentrations in human plasma samples: 1.00−1000 ng/mL for forsythin, 2.50−2500 ng/mL for KD-2-Glc, and 5.00−5000 ng/mL for KD-2-SO3H. Assays were validated and satisfied the acceptance criteria recommended by the CFDA guidance. Furthermore, this LC–MS/MS method was successfully implemented in a Phase I, first-in-human, dose-escalation pharmacokinetic study among Chinese healthy participants after single oral administration of forsythin tablets.

Validated LC-MS/MS method for the simultaneous determination of enalapril maleate, nitrendipine, hydrochlorothiazide, and their major metabolites in human plasma.

Hypertension is a major risk factor for atherosclerosis and ischemic heart disease. Most hypertensive patients need a combination of antihypertensive agents to achieve therapeutic goals. A rapid, sensitive, and selective liquid chromatography-tandem mass spectrometric method was developed and validated for simultaneous determination of enalapril maleate (ENA) and its major metabolite enalaprilat (ENAT), nitrendipine (NIT) and its major metabolite dehydronitrendipine (DNIT), and hydrochlorothiazide (HCT) in human plasma using felodipine as an internal standard (IS). The drugs were extracted from plasma using one-step protein precipitation. Chromatographic separation was performed on a Symmetry C18 column, with water and acetonitrile (10:90, v/v) as mobile phase. The detection was carried out using multiple reaction monitoring mode and coupled with electrospray ionization source. Multiple reaction monitoring transitions were m/z 377.1 → 234.1 for ENA, m/z 349.2 → 206.1 for ENAT, m/z 361.2 → 315.1 for NIT, m/z 359 → 331 for DNIT, m/z 295.9 → 205.1 for HCT, and m/z 384.1 → 338 for felodipine (IS). The method was linear over concentration ranges of 1-200, 20-500, 5-200, 2-100, and 5-200 ng/mL for ENA, ENAT, NIT, DNIT, and HCT, respectively, with r2 ≥ 0.99. Method validation was performed according to U.S. Food and Drug Administration guidelines. The validated method showed good sensitivity and selectivity and could be applied for therapeutic drug monitoring and bioequivalence studies.

LC-MS/MS simultaneous quantification of apomorphine and its major metabolites in human plasma: Application to clinical comparative bioavailability evaluation for the apomorphine sublingual film and a subcutaneous product

A liquid chromatography-tandem mass spectrometry (LC–MS/MS) method has been developed and validated for the simultaneous quantification of apomorphine and its metabolites apomorphine sulfate and norapomorphine in human plasma for supporting clinical development of a novel apomorphine sublingual thin film (APL) for the treatment of Parkinson’s disease. Analytes and internal standards (IS) were extracted from human plasma by Oasis HLB SPE cartridge, followed by a reversed phase LC–MS/MS analysis using multiple reaction monitoring (MRM) in positive mode (m/z 268 → 237 for apomorphine, 348 → 237 for apomorphine sulfate, and 348 → 237 for norapomorphine). Stable isotope-labeled compounds were used as IS for respective analytes. The validated curve ranges were 0.02–20 ng/mL, 10–1000 ng/mL, and 0.5–20 ng/mL for apomorphine, apomorphine sulfate and norapomorphine, respectively. Extraction recoveries were found to be 73.4 % (apomorphine), 81.1 % (apomorphine sulfate), and 58.6 % (norapomorphine). Established long-term plasma frozen storage stabilities were 504 days at -20 °C and276 days at −60 °C, respectively. The method has been successfully used for analyzing pharmacokinetics (PK) samples collected from a comparative bioavailability study of APL and the marketed apomorphine subcutaneous (s.c.) product Apo-go®. The results demonstrated that the 15-mg APL film administrated via sublingual produced comparable PK characteristics of apomorphine when compared to the commercial product Apo-go (2-mg) via s.c. administration, hence establishing the dose regimen for this sublingual formulation. It was also noticed that the sublingual 15-mg APL film produced a significantly higher apomorphine sulfate metabolite level than the 2-mg s.c. Apo-go, and both treatments yielded a negligible level of norapomorphine metabolite in humans.

Development and validation of a LC-MS/MS method for simultaneous determination of TQ-A3326 and its major metabolites in human plasma, urine and feces: application to pharmacokinetic assay

TQ-A3326 has been developed as a new drug by modifying the structure of daclatasvir with deuterium. The pharmacokinetics (PK) of TQ-A3326 in human remains unclear. The aim of the present study was to establish a LC-MS/MS method to investigate preliminarily the PK characteristics of TQ-A3326 and its major metabolites in healthy Chinese volunteers. All volunteers were administrated TQ-A3326 (60 mg). Plasma, feces and urine samples were extracted through protein precipitation. A rapid and sensitive LC-MS/MS method was successfully developed and applied to assess the PK properties of TQ-A3326. The AUC0-t and Cmax were 39516.3 ± 10778.5, 1034.6 ± 452.9 and 71.0 ± 49.5 ng·h·mL−1, and 1411.2 ± 325.4, 52.9 ± 16.4 and 1.8 ± 0.5 ng·mL−1, respectively, for TQ-A3326, M2-D and M4-D. Feces were the predominant route of elimination of TQ-A3326. M2-D was an abundant metabolite in feces and urine, representing 23.72% and 0.24% of the dose, respectively. The measurements of TQ-A3326 and its active metabolites would help to better understand the predominant route of elimination of the prototype drug, and provide meaningful information for further investigation of the bioactive mechanism of TQ-A3326 and its clinical applications.

Simple LC-MS/MS method using core-shell ODS microparticles for the simultaneous quantitation of edoxaban and its major metabolites in human plasma

Edoxaban is mainly enzymatically converted to a 4-carboxylic acid form (4CA-EDX) and an N-desmethyl form (ND-EDX) in humans. This study aimed to establish a simple liquid chromatography-tandem mass spectrometry method using core-shell octadecyl silica (ODS) microparticles for the simultaneous quantitation of edoxaban and its two major metabolites in human plasma. Analytes extracted from plasma specimens by a one-step deproteinization were separated using a 2.6-µm core-shell ODS microparticulate column and linear acetonitrile-ammonium acetate gradient elution at a flow rate of 0.25 mL/min with a run time of 7 min. The mass spectrometer was operated in the positive ion multiple reaction monitoring mode. Plasma samples collected from 20 patients with atrial fibrillation were analyzed by the present method. The chromatograms of drug-free human plasma had no interfering peaks. The calibration curves of edoxaban, 4CA-EDX, and ND-EDX were linear over the concentration ranges of 1.25–160, 0.47–60, and 0.12–15 ng/mL, respectively. Their pretreatment recoveries and matrix factors were 88.7–109.0% and 87.0–101.6%, respectively. The intra- and inter-day accuracy and imprecision values were 85.9–112.8% and within 13.3%, respectively. The plasma concentrations of edoxaban, 4CA-EDX, and ND-EDX in the patients had ranges of 17.8–102, 1.67–25.7, and 0.685–5.34 ng/mL, respectively. All the analytes were measurable within their calibration curves. In conclusion, this validated method for the simultaneous determination of edoxaban and its major metabolites was successfully applied to plasma specimens obtained from patients with atrial fibrillation.

Qualitative and quantitative determination of anaprazole and its major metabolites in human plasma

Anaprazole is a novel proton pump inhibitor under development for the treatment of gastric and duodenal ulcers. In the present study, an ultra-performance liquid chromatography-ultraviolet detector/quadrupole time-of-flight mass spectrometry method was developed for the metabolic profiling of human plasma after an oral administration of 40 mg anaprazole. The principal metabolic pathways were identified as sulfoxide reduction to thioether (M8-1), dehydrogenation (M21-1), sulfoxide oxidation to sulfone (M16-3), and sulfoxide reduction with O-demethylation to form carboxylic acid (M7-1). Anaprazole, M8-1, M16-3, M21-1, and M7-1 were selected and further quantified in human plasma by using a rapid and sensitive liquid chromatography–tandem mass spectrometry method. Anaprazole and its four metabolites were extracted from 50 of μL plasma by acetonitrile protein precipitation. Chromatographic retention and separation were achieved on an Kinetex XB-C18 column (50 mm × 4.6 mm i.d., 5 μm) under gradient elution using 5 mM ammonium acetate with 0.005 % ammonium hydroxide and methanol with 0.005 % ammonium hydroxide as the mobile phase. Positive electrospray ionization was performed using multiple reaction monitoring with transitions of m/z 402.2→242.2, 386.2→226.2, 400.2→242.2, 418.2→282.2, and 386.2→161.2 for anaprazole, M8-1, M21-1, M16-3, and M7-1, respectively. This method was linear in the range of 5.00–3000 ng/mL for anaprazole and 1.00–600 ng/mL for the four metabolites. The lower limit of quantitation was established at 5.00 ng/mL for anaprazole and 1.00 ng/mL for the metabolites. The quantitative method was used to evaluate the pharmacokinetics of anaprazole in phase I clinical trials.

Simultaneous determination of deuterated vortioxetine and its major metabolite in human plasma by UPLC-MS/MS and application to a pharmacokinetic study in healthy volunteers

JJH201501, a deuterated modification for multi-target antidepressant vortioxetine, is currently in phase I clinical trial. This study aimed to establish a sensitive and rapid UPLC-MS/MS method that was capable of simultaneously detecting JJH201501 and its major metabolite JJH201501-01 quantitatively in human plasma. The pretreatment was achieved by protein precipitation using 4-fold(v:v) acetonitrile with 5 ng/mL fluoxetine as internal standard precipitant. For method validation, the method was investigated in terms of the selectivity, inter- and intra-run precision and accuracy, carryover, matrix effect, extraction recovery and stability. The total running time was 3 min, and the retention time of JJH201501 and JJH201501-01 was 1.17 min and 1.05 min, respectively. The linear concentration range for JJH201501 and JJH201501-01 was 0.2 to 50 ng/mL and 0.4 to 100 ng/mL, respectively. The results showed that this method was in line with the guidelines for bioanalytical method proposed by FDA. In addition, the method was successfully applied to a plasma pharmacokinetic study of JJH201501 tablets in healthy volunteers which was part of the phase I trial.

Simultaneous determination of novel ketolide antibiotic nafithromycin and its major metabolite in human plasma using liquid chromatography tandem mass spectrometry.

Aim: A sensitive method to quantify nafithromycin and its N-desmethyl metabolite in human plasma was necessary for Phase I pharmacokinetic studies. Methodology: A precise and accurate LC-MS/MS bioanalytical method has been developed and validated for the simultaneous quantification of nafithromycin (NFT, WCK 4873) and N-desmethyl metabolite (M1, WCK 4978) in human plasma. Clarithromycin was used as an internal standard. Protein precipitation technique was used as sample preparation approach. The calibration curve was linear (r ≥0.99) over the concentration range of 10-5000ng/ml for NFT and M1. Method was validated as per US FDA guideline. Conclusion: The proposed method was successfully applied for determination of plasma levels of the NFT and M1 during Phase I clinical studies.

Quantification of microdosed oral yohimbine and its major metabolite in human plasma in the picogram range.

Aim: Pharmacokinetics after oral microdosing of the anticipated CYP2D6 substrate yohimbine and its metabolite 11-OH-yohimbine is potentially useful for drug-drug interaction trials and profiling of CYP2D6 enzyme activity. Materials & methods: We developed an ultrasensitive ultra performance liquid chromatography coupled to tandem mass spectrometry assay for quantification of yohimbine and its main metabolite 11-OH-yohimbine in plasma with a linear calibration range of 5-2500 pg/ml and validated it according to US FDA's and EMA's guidelines. Sample preparation was performed using fast liquid-liquid extraction. The assay was applied for the determination of concentrations of yohimbine and 11-OH-yohimbine in plasma after oral administration of 50 μg yohimbine to two subjects. Conclusion: Ultrasensitive quantification of yohimbine and its metabolite enables the determination of their concentrations in plasma after microdosing which would be applicable to use in CYP2D6 phenotyping.