Precipitation Of Plasma Proteins Research Articles

Comparison of Protocols to Test Peptide Stability in Blood Plasma and Cell Culture Supernatants.

Due to their high specificity, peptides are promising candidates in drug development, but fast degradation often limits their biological activity. Thus, a short half-life is one of the major challenges in the development of new peptide therapeutics. Moreover, the enzymatic cleavage of peptides can be a reason for misleading results in biological assays. Peptide stability assays typically consist of incubation, precipitation, and detection steps. However, the current methods differ greatly regarding these three steps, thus limiting the compatibility. Here, we systematically evaluate different parameters of peptide stability assays. First, we quantified and compared the analyte loss during the precipitation of plasma proteins. Especially, broadly used precipitation by strong acids was found to be unsuitable, while mixtures of organic solvents preserved more peptides for further analysis. Next, the stability of four fluorescently labeled model peptides was analyzed in blood plasma and two different cell culture supernatants. Strong variation in the degradation dynamics and patterns was found. Finally, we evaluated the role of fluorescent labeling on peptide stability and compared results to peptides with isotopic labels, underlining the individual advantages of both methods. Altogether, the data provide important parameters for analyzing and comparing the peptide stability.

Determination of anamorelin concentration in human plasma using a simple high-performance liquid chromatography-ultraviolet detection method.

Anamorelin, a non-peptide ghrelin analog and growth hormone secretagogue, is a novel oral drug used to treat cancer cachexia. Patients with cancer cachexia frequently use several drugs and anamorelin is a substrate of cytochrome P450 (CYP) 3A4; therefore, drug-drug interactions with CYP3A4 inhibitors and inducers pose a clinical problem. In this study, we aimed to determine the concentration of anamorelin in human plasma using a simple high-performance liquid chromatography-ultraviolet (HPLC-UV)-based method. The analysis involved extracting a 200-μL plasma sample and protein precipitation using solid-phase extraction. Anamorelin was isocratically separated using a mobile phase consisting of 0.5% potassium dihydrogen phosphate (pH 4.5) and acetonitrile (61:39, v/v) on a Capcell Pack C18 MG II column (250 mm × 4.6 mm) at a flow rate of 1.0 mL/min and monitored at a detection wavelength of 220 nm. The calibration curve was linear within a plasma concentration range of 12.5-1,500 ng/mL, with a coefficient of determination of 0.9999. The intra- and inter-day coefficients of variation were 0.37-6.71% and 2.05-4.77%, respectively. The accuracy of the assay and recovery were 85.25-112.94% and > 86.58%, respectively. This proposed HPLC-UV method is simple and can be applied in clinical settings.

HPLC-MS/MS method development and validation for the determination of tetradecapeptide in human plasma

Introduction. The number of peptide drugs being developed and registered has increased in recent years. Therefore, modern analytical approaches and methods are required to determine these substances in biological matrices during pharmacokinetic studies. Peptides are structurally intermediate between small molecules and biopolymers, making it difficult to develop methods for determining them using High Performance Liquid Chromatography with Tandem Mass Spectrometry (HPLC-MS/MS). Peptide derivatization can help achieve optimal chromatographic separation and increase method sensitivity.Aim. To develop and validate a method for the determination of the tetradecapeptide (TDP) threonyl-glutamyl-lysyl-lysyl-arginyl-arginyl-glutamayl-threonyl-valyl-glutamyl-arginyl-glutamyl-lysyl-glutamate in human plasma by HPLC-MS/MS.Materials and methods. The determination of TDP in human plasma was performed by HPLC-MS/MS. Sample preparation included a combination of blood plasma protein precipitation with propionic acid solution in methanol, liquid-liquid extraction with chloroform, and peptide derivatization with propionic anhydride. Internal standard (IS) was threonyl-glutamyl-lysyl-lysyl-arginyl-arginyl-glutamayl-threonyl-leucyl-glutamyl-arginyl-glutamyl-lysyl-glutamate. Chromatographic separation was performed in gradient mode, eluent A was 0.1 % formic acid solution in water, eluent B was 0.1 % formic acid in acetonitrile. Column: Waters XBridge C18, 4.6 × 50 mm, 5 µm. Ionization source was electrospray in positive mode. Multiple reaction monitoring (MRM) transitions for 4-substituted TDP propionate were: 681.30 → 73.95 m/z, 681.30 → 84.00 m/z, 681.30 → 101.90 m/z, 681.30 → 140.10 m/z, and for 4-substituted IS propionate: 686.00 → 74.10 m/z, 686.00 → 84.05 m/z, 686.00 → 102.00 m/z, 686.00 → 140.00 m/z.Results and discussion. Validation of the developed method was carried out in accordance with the requirements of Eurasian Economic Union and the following parameters were determined: selectivity, matrix effect, calibration curve, accuracy and precision, recovery, lower limit of quantification, sample carryover, stability.Conclusion. The method for the determination of TDP in human blood plasma by HPLC-MS/MS was developed and validated. The analytical range was 5.00–1000.00 ng/mL, allowing the method to be used to study TDP pharmacokinetics.

A new validated high‐performance liquid chromatography method for the determination of regorafenib in rat plasma: Application for pharmacokinetic study

AbstractThis study reports a rapid and sensitive reversed‐phase high‐performance liquid chromatography method with ultraviolet detection for the determination of regorafenib (REG) in rat plasma. For the extraction of REG from plasma and the precipitation of plasma proteins, a rapid one‐step precipitation method was performed with methanol. The separation was performed in a methanol‐water mixture (80:20, v:v) mobile phase system with a C18 column and monitored at a wavelength of 258 nm. Nilotinib was used as an internal standard. The linear dynamic range of REG was determined between 5 and 500 ng/mL in standard solution and plasma. The limit of detection of REG from the standard solution was found to be 1.23 ng/mL and the limit of quantitation was 3.73 ng/mL. The limit of detection of REG from plasma was found to be 1.55 ng/mL and the limit of quantitation was 4.70 ng/mL. Regorafenib was administered at 5 mg/kg to 10 healthy male Sprague Dawley rats, and pharmacokinetic results were evaluated. It exhibited a high recovery of 93.82% in plasma. Due to ease of sample preparation, high susceptibility, specificity, and certainty, the described method can be used successfully in the quantification of REG in in‐vivo plasma and in routine analyses in clinical laboratories.

A validated LC-MS/MS method for determination of Molnupiravir and Favipiravir in human plasma; Assessment of the remarkable potential synergistic effect against SARS-CoV-2 Infection: Application to a pharmacokinetic study in healthy Egyptian volunteers

Several clinical trials were carried out to find the route for an efficient therapy against SARS-CoV-2 infection. Mono- and dual therapy of various antivirals were investigated and found to have a clinical benefit in infected patients. Some of these antivirals are Molnupiravir (MOL) and Favipiravir (FAV), both drugs were evaluated for combined antiviral activity in some recent clinical trials. In this study, an efficient, simple, and rapid LC-MS/MS method for simultaneous determination of N-hydroxycytidine (NHC), MOL active metabolite, and FAV in human plasma of healthy volunteers was developed. Plasma protein precipitation was performed using acetonitrile. Compounds’ separation was achieved using Agilent Zorbax Eclipse plus C18, 4.6 × 150 mm, 3.5 µm and an isocratic elution of a mobile phase composed of methanol − 0.2 % acetic acid (10:90, v/v) at a flow rate of 0.5 mL/min using pyrazinamide as an internal standard (IS). Drugs were quantified using API 6500 + Qtrap mass spectrometer employing a selective ion mode combining a positive and negative ESI interface. The bioanalytical method was validated in accordance with the US-FDA bioanalytical guidance. The calibration range for both NHC and FAV was 10.0–––10000.0 ng/mL computed via weighted linear regression approach (1/x2). The proposed method could be applied to support the upcoming clinical studies for therapeutic drug monitoring of patients undergoing dual combination therapy as the latter combination proved more efficacious and powerful tool for the complete treatment of SARS-CoV-2 cases. Finally, the suggested bioanalytical method was efficiently utilized in human pharmacokinetic study of NHC and FAV, after simultaneous co-administration, in healthy volunteers.

Simple HPLC-UV Method for Therapeutic Drug Monitoring of 12 Antiepileptic Drugs and Their Main Metabolites in Human Plasma

The objective of the present report was to develop and validate a simple, selective, and reproducible high-performance liquid chromatography method with UV detection suitable for routine therapeutic drug monitoring of the most commonly used antiepileptic drugs and some of their metabolites. Simple precipitation of plasma proteins with acetonitrile was used for sample preparation. 10,11-dihydrocarbamazepine was used as an internal standard. Chromatographic separation of the analytes was achieved by gradient elution on a Phenyl–Hexyl column at 40 °C, using methanol and potassium phosphate buffer (25 mM; pH 5.1) as a mobile phase. The method was validated according to the FDA guidelines for bioanalytical method validation. It showed to be selective, accurate, precise, and linear over the concentration ranges of 1–50 mg/L for phenobarbital, phenytoin, levetiracetam, rufinamide, zonisamide, and lacosamide; 0.5–50 mg/L for lamotrigine, primidone, carbamazepine and 10-monohydroxycarbazepine; 0.2–10 mg/L for carbamazepine metabolites: 10,11-trans-dihydroxy-10,11-dihydrocarbamazepine and carbamazepine-10,11-epoxide; 0.1–10 mg/L for oxcarbazepine; 2–100 mg/L for felbamate and 3–150 mg/L for ethosuximide. The suitability of the validated method for routine therapeutic drug monitoring was confirmed by quantification of the analytes in plasma samples from patients with epilepsy on combination antiepileptic therapy.

Development, validation and clinical implementation of a UPLC-MS/MS bioanalytical method for simultaneous quantification of cabotegravir and rilpivirine E-isomer in human plasma

A reversed phase ultra-high performance liquid chromatography method was developed for the simultaneous quantification of cabotegravir (CAB) and the E-isomer of rilpivirine (RPV) in human EDTA plasma, also considering RPV E-isomer instability. Because of the instability of RPV (and CAB) in all light conditions, the (RPV Z-isomer/total RPV)-isomer ratio of RPV was determined for each stock, calibration curve standard, quality control sample and patient sample. [2H3]-CAB and [13C6]-RPV were used as internal standard. Sample preparation involved protein precipitation of plasma using methanol. An HSS T3 column with a guard column (set at 40 °C) was used for analyte separation. The mobile phase components were 65 % 0.1 % formic acid in water (A) and 35 % 0.1 % formic acid in acetonitrile (B) and the flow rate was 0.5 mL/min. Detection was performed with tandem mass spectrometry (MS/MS) in a total runtime of 3.0 min. The assay was validated over the concentration range of 0.0500 – 10.0 mg/L for CAB and 0.00300 – 3.00 mg/L for RPV. The average within-day and between-day accuracies for the assay in plasma were 101 % and 101 % for CAB and 97.6 % and 98.5 % voor RPV, respectively. Within-day and between-day precision in coefficients of variations (CV) were 5.0 %. Extraction recovery was 99 % and 102 % for CAB and its internal standard and 95 % and 97 % for RPV and its internal standard. As our aim was that the (Z-isomer RPV/total RPV) response ratio in patient samples had to be less than 10 % to give reliable results, the (Z-isomer RPV/total RPV) response ratio in stocks, calibration curve standards and internal quality control samples were also taken into account being maximal 0.9 % and 2.3 % respectively. This assay has been successfully used in our Therapeutic Drug Monitoring (TDM) service for people living with HIV on long-acting injectable therapy with CAB/RPV and will also be used in future pharmacokinetic studies.

Dispersive solid phase extraction of risperidone from plasma samples using graphene oxide aerogels and determination with liquid chromatography.

A graphene oxide-based aerogel was synthesized and applied to the extraction and the determinations with the HPLC-ultra violet detector. After the characterization of the produced graphene-aerogel, it was utilized as a dispersive solid-phase extraction sorbent for risperidone extraction from plasma samples. Aerogels are materials with a large surface area-to-mass ratio and plenty of core with functional groups which can easily attach to the analytes to extract them to the second phase. The suggested method determined risperidone in plasma samples in the wide dynamic range from 20 ng/mL to 3 μg/mL. The limits of detection and quantification of the developed method were calculated as 2.4 ng/mL and 8.2 ng/mL, respectively. As a novel feature, the developed method has no need to precipitate plasma proteins, improving the analytical performance of the analysis. Also, for the first time, the produced materials were utilized for the extraction of RIS from the plasma samples. The obtained results revealed that the developed approach could be employed as an accurate method for the quantification of risperidone in real plasma samples. This article is protected by copyright. All rights reserved.

Method Development and Validation for the Simultaneous Quantitation of Pentoxifylline, Its Pharmacologically Active Metabolites, and Donepezil Using LC-MS/MS in Rat Plasma: Its Application to a Pharmacokinetic Study

This study developed a simple, rapid, reproducible, and analytical method using liquid chromatography and electrospray ionization (ESI) with tandem mass spectrometry (LC-MS/MS) to simultaneously quantify pentoxifylline (PTX), its pharmacological active metabolites, lisofylline (PTX-M1) and 1-(3-carboxypropyl)-3,7-dimethylxanthine (PTX-M5), and donepezil (DNP) in rat plasma, using PTX-d6 and DNP-d7 as the internal standards. The LC-MS/MS procedure was performed at the ESI interface, operating in positive ionization and multiple reaction monitoring (MRM) modes; the monitoring of transitions comprised m/z 279.3 > 181.1 for PTX, m/z 281.1 > 263.1 > 160.90 for PTX-M1, m/z 267.1 > 249.0 > 220.9 for PTX-M5, m/z 380.3 > 90.9 for DNP, m/z 285.3 > 187.1 for PTX-d6 (IS1), and m/z 387.3 > 98.3 for DNP-d7 (IS2). After plasma protein precipitation (PP) with methanol, chromatographic separation was performed with an Imtakt Cadenza® CD-C18 (100 × 3 mm, 3 µm) column, using an isocratic mobile phase consisting of 0.1% formic acid in water and methanol (20:80, v/v) at a flow rate of 0.2 mL/min. The retention times of DNP, PTX-M5, PTX, and PTX-M1 were 2.24, 2.50, 2.68, and 2.72 min, respectively, with a total run time of 5 min. This method was validated over a linear concentration range of 5–8000, 10–5000, 20–15,000, and 2–500 ng mL−1 for PTX, PTX-M1, PTX-M5, and DNP, respectively, with a high correlation coefficient (r2 ≥ 0.99). The established method was fully validated in terms of selectivity, the lower limit of quantitation, precision, accuracy, recovery, matrix effect, stability, and dilution integrity according to the regulatory guidelines from the U.S. Food and Drug Administration and the Korea Ministry of Food and Drug Safety. The validated method was successfully applied to a pharmacokinetic study on the concurrent administration of DNP and PTX in rats.

Quantitation of 10 antibiotics in plasma: Sulfosalicylic acid combined with 2D-LC-MS/MS is a robust assay for beta-lactam therapeutic drug monitoring

Therapeutic drug monitoring (TDM) of antibiotics is particularly important in populations with high pharmacokinetic variabilities, such as critically ill patients, leading to unpredictable plasma concentrations and clinical outcomes. Here, we i) describe an original method for the simultaneous quantification of ten antibiotics (cefepime, ceftazidime, ampicillin, piperacillin/tazobactam, cefotaxime, amoxicillin, cloxacillin, oxacillin, linezolid) using 5-sulfosalicylic acid dihydrate (SSA) solution for protein precipitation together with 2D-LC-MS/MS, and ii) evaluate its impact in a one-year retrospective study. The method involved simple dilution with an aqueous mix of deuterated internal standards and plasma protein precipitation with SSA. Twenty microliters of the supernatant was injected into a C8 SPE online cartridge (30 × 2.1 mm) without any evaporation step and back-flushed onto a C18 UHPLC (100 × 2.1 mm) analytical column. Mass spectrometry detection (Xevo TQD) was performed in positive electrospray, in scheduled MRM mode. Overall analytical runtime was 7 min. Due to analytical constraints and the physicochemical properties of the antibiotics, protein precipitation using organic solvents could not be applied. As an alternative, SSA used with 2D-LC offered various advantages: i) lack of dilution resulting in better assay sensitivity, and ii) good chromatography of hydrophilic compounds. Ten microliters of 30% SSA in water eliminated>90% of plasma proteins, including the most abundant high molecular weight proteins at 55 and 72 kDa. The assay was successfully validated according to FDA and EMA guidelines for all the antibiotics, and the coefficients of variation of the quality control (QC) run during sample analysis over one year were below 10%, whatever the QC levels or the antibiotics. The use of 2D-LC combined with SSA precipitation allowed development of a robust, sensitive and rapid quantification assay. Feedback to clinicians was reduced to 24 h, thus allowing rapid dosage adjustment. During one year, 3,304 determinations were performed in our laboratory: 41% were not in the therapeutic range, 58% of which were sub-therapeutic, underlining the importance of early TDM of antibiotics to limit therapeutic failures and the emergence of bacterial resistance.

Simultaneous pharmacokinetic assessment of phytopharmaceuticals in fenugreek extract using LC-MS/MS in Sprague-Dawley rats.

Fenugreek seeds are used in numerous marketed herbal formulations with therapeutic benefits. Some of its bioactive components such as 4-hydroxyisoleucine, trigonelline, raffinose, and pinitol are reported to possess potential therapeutic activities, such as antibacterial, antidiabetic, stomach stimulant, and anti-invasive, against hyperandrogenism and other allied diseases, including polycystic ovary syndrome. A fully validated, selective, and sensitive bioanalytical method for the simultaneous rapid quantification of the aforementioned bioactive components has been developed using hyphenated liquid chromatography electrospray tandem mass spectrometry. The analytes were separated within 5min using gradient elution in a C18 column at a flow rate of 0.5ml/min. Plasma protein precipitation technique was employed to isolate the analytes from the samples. Oral pharmacokinetic profile of the four bioactive components in Sprague-Dawley rats was further evaluated using noncompartmental analysis using Phoenix WinNonlin software.

Development of a High-Performance Liquid Chromatography-Tandem Mass Spectrometry (HPLC-MS/MS) Method to Determine the Presence of Rivastigmine in Human Plasma in Clinical Studies of Comparative Pharmacokinetics

The basis for conducting bioequivalence studies is the determination of the bioavailability of the active substance of the drug at its place of action by establishing the concentration of the drug in biological fluids using sensitive analytical techniques. The bioanalytical technique used should provide reliable results which would lead to satisfactory level of interpretation. To investigate the bioequivalence of rivastigmine preparations, an 8 times more sensitive method (compared to the data in the available literature) for the quantitative determination of rivastigmine in human blood plasma by HPLC-MS/MS was developed. Rivastigmine is extracted from plasma by precipitation of plasma proteins with acetonitrile. Chromatographic separation of rivastigmine and the internal standard was carried out on a YMC Triart C18. 50×2.0 mm (1.9 µm) column in a gradient elution mode with a flow rate of 0.5 ml/min. A 0.1% solution of ammonium hydroxide and acetonitrile were used as mobile phases. The lower limit of the quantitative determination of the method was 25 pg/ml.

Development of a SPE-LC-MS Method for the Quantitation of Palbociclib and Abemaciclib in Human Plasma

Palbociclib and abemaciclib are two cyclin-dependent kinases 4 and 6 used for breast cancer treatment. Levels of these medicines present a significant interindividual variability, so monitoring those concentrations might be necessary in therapy. Most of the methods presented so far in the literature use simple protein precipitation of plasma proteins as sample preparation method followed by direct injection of the supernatant into the LC instrument, preceded or not by a simple filtration step. Within that approach, the probability of injecting proteins in the chromatographic system is increased. With the purpose of obtaining a cleaner extract of the drugs, we developed and validated a simple and accurate LC-MS method for determining palbociclib and abemaciclib in human plasma. Solid phase extraction (SPE) using Oasis PRiME HLB® cartridges was used for plasma sample preparation. The method provided clean extracts with a recovery extraction higher than 85% for both compounds. Separation was achieved by high-performance liquid chromatography (HPLC), using a C18 (4.6 × 50 mm) column, with a gradient elution of ammonium acetate/acetic acid-acetonitrile as the mobile phase. Detection was performed by mass spectrometry (MS) in single ion recording (SIR) mode. Intra-day and inter-day precision data for both analytes were 3.8-7.2% and 3.6-7.4%, respectively. Calibration curves were both linear between 2 and 400 ng/mL with a correlation coefficient higher than 0.998. The LC-MS method can be used to quantify the drugs in human plasma in routine analysis. The method proved to be useful in determining real plasma levels in patients involved in cancer therapy. Drug concentrations were determined in a 10 min run-time, including re-equilibration of the column.

LC-MS/MS-based metabolite quantitation of the antiviral prodrug baloxavir marboxil, a new therapy for acute uncomplicated influenza, in human plasma: Application to a human pharmacokinetic study

Baloxavir marboxil (BXM) is a novel orally administrated prodrug for the treatment of acute uncomplicated influenza. In the present study, a bioanalytical LC-MS/MS method was developed and validated for the quantification of baloxavir acid (BXA), the active form of baloxavir marboxil in plasma of healthy volunteers using dolutegravir as an internal standard (IS) following plasma protein precipitation with acetonitrile. BXA and the internal standard were chromatographically separated using Waters Xterra® MS C8 column (5 µm, 4.6 × 50 mm) and a mobile phase comprised of 10.0 mM ammonium formate pH 3.5 and acetonitrile (80:20, v/v) delivered at a flow rate of 0.6 mL/min. The transitions of m/z 484.00 → 247.0 and 420.30 → 277.1 for BXA and IS, respectively in multiple reaction monitoring (MRM) mode in a positive ESI interface were used for quantitation through triple-quad mass spectrometry, API 4000. The method linearity was proven across the concentration range of 0.5–200.0 ng/mL, adjusted, and validated completely in accordance with the bioanalytical guidelines of the United States-FDA. Finally, the present method was effectively applied for the pharmacokinetic study of BXA in healthy human volunteers with accepted reproducibility and ruggedness.

A new HPLC methodology for the analysis of metronidazole and dexibuprofen: Application to pharmacokinetic study and comparative greenness assessment

For the simultaneous analysis of metronidazole and dexibuprofen in real human plasma samples, a new HPLC method with a 6-minute analysis time was developed. Furthermore, the method was used to investigate their pharmacokinetics and bioavailability. The internal standard was chosen to be guaifenesin (IS). Following acetonitrile precipitation of plasma proteins, the drugs were chromatographically separated using a Zorbax Eclipse® C 18 column with acetonitrile: water (pH 4 with aqueous phosphoric acid) gradient mixture. Metronidazole and dexibuprofen calibration curves were found to be linear over the ranges of 0.5–20 and 1–30 µg/mL, respectively, with good correlation coefficients. The analysis of quality control samples revealed outstanding accuracy and precision. Drug stability was also examined throughout storage and processing, and all coefficients of variation were under 8.23 %. After this optimized method was successfully applied to plasma samples and the pharmacokinetic parameters of each of the targeted medicines were examined separately and compared to their parameters when they were administered concurrently. The outcomes supported each drug's significant impact on the pharmacokinetic characteristics of the other. Using five metrics, including the Analytical Eco-scale, Analytical GREEnness Calculator (AGREE), RGB-12, Hexagon, and AGREE-prep, the environmental impact of the suggested approach and some reported methods utilized for the determination of either medicines in biological matrix were evaluated. The promising results demonstrated lower environmental and health risks associated with sample preparation and analysis.

Automated HPLC-MS/MS assay for the simultaneous determination of ten plasma antibiotic concentrations

Therapeutic drug monitoring (TDM) of antibiotics (ATB) in patients with serious bacterial infections allows optimization of the efficacy of the treatment while reducing the risk of toxicity. Notably, early measurement of plasma beta-lactam concentration has been shown to be associated with reduced mortality in intensive care patients. In this context, a rapid, robust, and accurate assay method is essential for daily TDM.A fully automated procedure for quantification of the plasma concentrations of ten ATB was developed. The ATB were divided into two calibration pools, with Pool 1: aztreonam, ceftobiprole, cefoxitin, avibactam, tazobactam and Pool 2: metronidazole, ceftriaxone, daptomycin, ceftolozane, moxifloxacin. Sample preparation consisting of acetonitrile plasma protein precipitation and H20 dilution was applied to all analytes. This procedure was carried out by an automated sample preparation system directly coupled to a liquid chromatography-tandem mass spectrometry (LC-MS/MS) system. Since the instrument extracts sample n while sample n-1 is in the LC-MS/MS system, the delay between obtaining the results for two samples corresponds to the analytical run time, which is less than 7 min.The method was validated according to the Food and Drug Administration guidelines. The method was sensitive (lower limit of quantification 0.1–1 mg/L, depending on the ATB), accurate (intra/inter-assay bias −14.8 to 14.2 %) and precise (intra/inter-assay CVs 1.27 to 16.3 %). Application of the TDM assay was illustrated by the report of an intensive care patient treated with the ceftazidime/aztreonam/avibactam combination. Four assays were performed in 8 days with results returned within 24 h to quickly manage the dose regimen in this patient.An automated, simple, rapid, robust LC-MS/MS analysis was developed and validated for the simultaneous quantification of plasma concentrations of 10 ATB and was applied with success to perform TDM. This method provides a shorter turnaround time than classic sample batch-based analytical methods.

Development and validation of an LC-MS/MS method for the assessment of Isoxazole, a bioactive analogue of curcumin in rat plasma: Application to a pharmacokinetic study

A novel Isoxazole (ISO) analog of curcumin is synthesized from curcumin and described as having a better pharmacological activity than curcumin, such as anti-cancer, anti-malarial, anti-mycobacterial, and many more. The present research aims to develop a bio-analytical method with a simple, rapid, selective, sensitive, accurate, and precise quantification of ISO by liquid chromatography coupled with tandem mass spectroscopy (LC-MS/MS) in rat plasma matrix. The simple plasma protein precipitation method was used for ISO extraction. The ISO was eluted in isocratic mode on a Water symmetry C18 column (75 × 4.6 mm2, 3.5 μm) at a 600 µL/min flow rate with a 0.1 % formic acid in water and methanol (20:80) as mobile phase. The MS/MS was used as a monitoring tool for the fragmentation of ISO as m/z = 366.1 → 145.1 and m/z = 237.1 → 194.07 for carbamazepine (CBZ; internal standard). The ISO showed good co-relation as (r2 = 0.999) linear and covered a wide range with a lower limit of quantification of 1.0 ng/mL. Finally, the developed method was successfully utilized for oral and intravenous pharmacokinetics of ISO in rats plasma. The absolute bioavailability of ISO was found at about 17.6 % after oral administration.

Quantitation of navtemadlin in human plasma and brain tissue by liquid chromatography-tandem mass spectrometry.

Navtemadlin is an orally bioavailable small molecule that blocks the protein-protein interaction between murine double minute 2 protein (MDM2) and the tumor suppressor protein p53, leading to p53-mediated cell cycle arrest and apoptosis. It is being evaluated in clinical trials for a variety of malignancies, both as a single agent and in combination regimens. A sensitive, robust LC-tandem mass spectrometry (LC-MS/MS) method was developed to quantitate navtemadlin in plasma, and this method was also validated using brain tissue homogenate. Sample preparation involved protein precipitation of plasma or brain tissue homogenate using acetonitrile. Navtemadlin, navtemadlin glucuronide, and the internal standard, D6 -navtemadlin, were separated from microsomal incubation extracts using gradient elution and a ZORBAX XDB C18 column. Analytes were detected using a SCIEX 5500 triple quadrupole mass spectrometer in positive electrospray ionization mode. The assay range of 1-1000 ng/mL was shown to be accurate (96.1-102.0% and 95.7-104%) and precise (coefficient of variation ≤ 10.6% and ≤ 6.6%) in plasma and brain tissue homogenate, respectively. An 8000 ng/mL navtemadlin sample diluted 1:10 (v/v) with plasma was also accurately quantitated. Navtemadlin has been stable in frozen plasma at -70°C for at least 20 months. This validated LC-MS/MS method was applied to determine navtemadlin concentrations in plasma and brain tissue samples from two separate patients receiving 120 mg/day navtemadlin on protocol ABTC1604.

A Sensitive LC-MS/MS Method for the Simultaneous Determination of Two Thia-Analogous Indirubin N-Glycosides and Indirubin-3'-Monoxime in Plasma and Cell Culture Medium.

Indirubin was identified as an active component of Danggui Longhui Wan, an herbal mixture used in traditional Chinese medicine, and showed anticancer activity in clinical trials in patients with chronic leukemia. Investigations on the mechanisms of antitumor action of indirubins have mainly focused on the indirubin derivative indirubin-3′-monoxime (I3M). Meanwhile, antiproliferative and cytotoxic properties on cancer cells have also been demonstrated for several synthetic indirubin N-glycosides. In the present study, we demonstrate cytotoxic activity of the thia-analogous indirubin N-glycosides KD87 (3-[3′-oxo-benzo[b]thiophen-2′-(Z)-ylidene]-1-(β-d-glucopyranosyl)-oxindole) and KD85 (3-[3′-oxo-benzo[b]thiophen-2′-(Z)-ylidene]-1-(β-d-mannopyranosyl)-oxindole) against melanoma and squamous cell carcinoma cells as well as lung cancer and glioblastoma cells. The advanced state of preclinical studies on the effects of indirubins conducted to date underscores the need for pharmacokinetic data from cellular, animal, and human studies for which reliable quantification is required. Therefore, a sensitive liquid chromatography-tandem mass spectrometric (LC-MS/MS) method was developed and validated for the simultaneous measurement of KD87, KD85, and I3M in plasma and cell culture medium. Experimental conditions for sample preparation were optimized for human plasma protein precipitation and liquid-liquid extraction from plasma and cell culture medium. The methods were successfully validated in accordance with the U.S. Food and Drug Administration Bioanalytical Method Validation and evaluated for selectivity, sensitivity, matrix effect, recovery, carryover, calibration curve linearity, accuracy, precision, and stability. The applicability of the methods was demonstrated by the determination of KD87 in mouse plasma after prior intraperitoneal administration to mice.

Plasma protein precipitation and comparative analysis of Sickle Cell Disease (SCD) samples using SDS-PAGE

Sickle cell disease (SCD) is an inherited autosomal recessive hereditary disorder caused by a mutation in the beta-globin gene leading to the production of abnormal haemoglobin-S which causes normal blood cells to ‘sickle’ by facilitating the polymerization of deoxygenated sickle haemoglobin. The condition imparts acute chest syndrome, vasoocclusive crisis, chronic haemolysis, pulmonary hypertension, edema and splenic sequestration in SCD individuals. Blood plasma from six patients diagnosed with SCD was collected, proteins were precipitated by acetone/TCA method and quantified through standard procedures. The quantified proteins were subjected to electrophoresis for the separation of proteins to observe the differences across protein band pattern in each sample.