Combined X-ray Reflectivity and Infrared Study of the Effect of Hydrogen Bonding of the OH Group on the Relaxation Behavior in Ultrathin Polyvinylphenol Films on SiO2.

Utilizing X-ray reflectivity and infrared reflection absorption spectroscopy (IR-RAS), we have investigated the thermal expansion and contraction of ultrathin polyvinylphenol (PVPh) films supported on a silicon (100) substrate capped with an amorphous SiO2 layer. Despite being known to form strong interactions with the SiO2 surface, the thin PVPh films showed a reduction in the glass-transition point Tg, similar to the behavior of polystyrene thin films deposited on SiO2. We explored the relationship between thermal expansivity and film thickness using well-annealed films and found that it decreases with film thickness in the range below twice the radius of gyration of a polymer chain (2Rg) in the glassy state. Thickness expansion in the glassy state and contraction in thickness at temperatures higher than Tg bulk (melt state) showed the presence of two competing relaxation processes. The reported negative thermal expansion in PVPh thin films, which was discovered to be one of the inherent properties, may have been caused by the fast relaxations that take place at the free polymer surface. IR-RAS was utilized to investigate the effect of thickness on hydrogen bonding in PVPh, and it was confirmed that with decreasing thickness, hydrogen bonding becomes weak, and the number of free OH groups increases. Therefore, thinner PVPh samples exhibit lower Tgs as an effect of easier molecular motions.

Development of an LC-MS/MS-based method for quantitation of osimertinib in human plasma and cerebrospinal fluid.

Aim: The transitivity of osimertinib to cerebrospinal fluid (CSF) is of clinical concern. A quantitative LC-MS/MS method for the determination of osimertinib in human plasma and CSF was developed to evaluate its transitivity. Results: The calibration range was 40-1000 nM in plasma and 0.8-100 nM in CSF. Accuracy and precision were within 15%. Osimertinib in the CSF but not in plasma strongly adsorbed onto the storage container. The mean adsorbed loss of osimertinib was 45.5% in CSF. Nonspecific binding in CSF was decreased by protein addition (mean loss = 5.8%). Conclusion: A robust validated method was developed for the quantification of osimertinib in human plasma and CSF.

An LC-MS/MS Method for Absolute Quantification of Nivolumab in Human Plasma: Application to Clinical Therapeutic Drug Monitoring.

BACKGROUND: Nivolumab is a fully humanized IgG4 monoclonal antibody that targets the programmed death-1 (PD-1) receptor, disrupting PD-1-mediated signaling and restoring antitumor immunity. The objective of this study was to develop a nivolumab quantification method using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and to evaluate its application in clinical therapeutic drug monitoring. METHODS: Nivolumab was purified from human plasma using rProtein A resin and then digested with trypsin. The ASGITFSNSGMHWVR peptide (multiple reaction monitoring transition: m/z 550.6→661.4) was detected as a surrogate peptide of nivolumab by triple quadrupole mass spectrometry. Plasma samples (126) were collected from 14 patients with non-small cell lung cancer who were undergoing clinical dosing regimen with nivolumab. The pharmacokinetic data were analyzed using Phoenix NLME software (Version 7.0, Certara, St. Louis, MO) based on a previously reported population pharmacokinetics (PPK) model of nivolumab. RESULTS: Nivolumab was selectively detected in human plasma and the linear range was 5-200 mcg/mL (R = 0.99). The accuracy and intraday and interday imprecision were within ±15% of the quality control values of 5 (lower limit of quantification), 10 (low), 80 (medium), and 160 (high) mcg/mL. The nivolumab concentrations measured using LC-MS/MS were consistent with those of previously reported PPK models, and the pharmacokinetic parameters could be adequately predicted from a single trough concentration using a Bayesian approach. CONCLUSIONS: An absolute quantification method for nivolumab using LC-MS/MS was successfully developed and validated. Combined with PPK analysis, this method should be useful for the therapeutic drug monitoring of nivolumab in clinical practice.

Development and validation of a method for gefitinib quantification in dried blood spots using liquid chromatography-tandem mass spectrometry: Application to finger-prick clinical blood samples of patients with non-small cell lung cancer.

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the quantification of gefitinib in dried blood spots (DBSs). Gefitinib was extracted with methanol from DBS of 3 mm in diameter and detected using a triple quadrupole mass spectrometer. The method was validated by evaluating its precision, accuracy, selectivity, carryover, matrix effect, recovery, and stability. For clinical validation, paired finger-prick DBS and plasma concentrations were compared for 10 patients with non-small cell lung cancer (NSCLC) taking gefitinib. The calibration linear range was 37.5-2400 ng/mL (coefficient of determination [R2] = 0.99), encompassing the therapeutic concentrations of gefitinib. The accuracy and precision were within 15% of the quality control (QC) concentrations of 80, 200, and 2000 ng/mL. The lower limit of quantification was determined to be 40 ng/mL. Gefitinib was stable in DBSs for up to 5 months at room temperature and -20 °C, and at 40 °C for 24 h. A good correlation was observed between the gefitinib levels measured by the DBS method and plasma concentrations (R2 = 0.99). This method provides a simple, fast, and accurate approach to the quantitative analysis of gefitinib in finger-prick DBSs. The method would be useful for minimally invasive evaluation of the clinical gefitinib blood concentration.