Assessment of remdesivir and its nucleoside metabolite in beagle dogs and healthy humans by liquid chromatography coupled with triple quadrupole mass spectrometry.

The aim of this study was to assess the pharmacokinetics of the existing remdesivir intravenous formulation (100 mg dose) against the newly developed oral formulation (20 mg dose) for remdesivir and its active nucleoside metabolite (GS-441524) in beagle dogs followed by healthy human volunteers. A quantification method for remdesivir and its active nucleoside metabolite (GS-441524) in beagle dog and human plasma has been developed and validated using liquid chromatography coupled to triple quadrupole mass spectrometry detection. The analytical methods for beagle dogs and human differ in the calibration curve range, plasma matrix, processing volume, reconstitution volume and injection volume; however all other parameters were same in both methods. A simple protein precipitation extraction was carried out using acetonitrile containing the internal standard remdesivir D5. Remdesivir and GS-441524 were separated on an Endurus C-18P, 100 × 4.6 mm, 3 µm column and detected using a mass spectrometer with electrospray ionization in positive ion mode. The ion transitions used were m/z 603.1 → m/z 200.0 for remdesivir, m/z 292.0 → m/z 202.2 for GS-441524 and m/z 608.2 → m/z 205.1 for remdesivir D5. The calibration curve results were linear in beagle dog plasma (2.0-2,000.8 ng/ml range for remdesivir and 2.0-1,500.4 ng/ml for GS-441524) and human plasma (30.0-4,503.9 ng/ml range for remdesivir and 2.0-200.4 ng/ml for GS-441524). The recovery was >90% in beagle dog and human plasma. These methods were successfully used to determine the pharmacokinetic parameters of the intravenous injection and subcutaneous tablets dosage forms in beagle dogs and healthy humans.

Sensitive and rapid quantitation of dexamethasone in human plasma using liquid chromatography coupled with triple quadrupole mass spectrometer.

The aim of this paper was to develop, validate, and utilize a sensitive liquid chromatography-tandem mass spectrometry bioanalytical method for bioequivalence/clinical trial studies conducted in human plasma. To accomplish the target, a stable labeled internal standard, that is, dexamethasone D4 was used as an internal standard to track and compensate the parent compound during processing, and extraction from plasma. The method involves a rapid liquid-liquid phase extraction from plasma, followed by reverse phase chromatography, and mass spectrometry detection, with a total run time of 3.5 min. The method was developed and validated from 2 to 600 ng/ml for dexamethasone. The mean recovery for dexamethasone was found to be 81.0%. The validated method enabled the analysis of dexamethasone in samples from clinical pharmacokinetic studies. The peak concentration of dexamethasone ranged between 253 to 281 ng/ml and 319 to 343 ng/ml, respectively, in fasted and fed conditions. The terminal half-life values for dexamethasone ranged between 3.5 to 8.2 h and 3.0 to 7.5 h, respectively.

Highly sensitive method for the determination of JI-101, a multi-kinase inhibitor in human plasma and urine by LC-MS/MS-ESI: method validation and application to a clinical pharmacokinetic study.

A highly sensitive, rapid assay method has been developed and validated for the estimation of JI-101 in human plasma and urine using LC-MS/MS-ESI in the positive-ion mode. The assay procedure involves extraction of JI-101 and alfuzosin (internal standard, IS) from human plasma/urine with a solid-phase extraction process. Chromatographic resolution was achieved on two Zorbax SB-C(18) columns connected in series with a PEEK coupler using an isocratic mobile phase comprising acetonitrile-0.1% formic acid in water (70:30, v/v). The total run time was 2.0 min. The MS/MS ion transitions monitored were 466.20 → 265.10 for JI-101 and 390.40 → 156.10 for IS. The method was subjected to rigorous validation procedures to cover the following: selectivity, sensitivity, matrix effect, recovery, precision, accuracy, stability and dilution effect. In both matrices the lower limit of quantitation was 10.0 ng/mL and the linearity range extended from ~10.0 to 1508 ng/mL in plasma or urine. The intra- and inter-day precisions were in the ranges 1.57-14.5 and 6.02-12.4% in plasma and 0.97-15.7 and 8.66-10.2% in urine. This method has been successfully applied for the characterization of JI-101 pharmacokinetics in cancer patients.