Simultaneous determination of paclitaxel and lansoprazole in rat plasma by LC-MS/MS method and its application to a preclinical pharmacokinetic study of investigational PTX-LAN-PLGA nanoformulation.

In spite of having a remarkable anti tumor activity against a wide variety of cancers, the clinical effectiveness of the major chemotherapeutic drug paclitaxel is often limited by the issues of drug resistance that hampers the therapeutic effectiveness of the drug. The combination of proton pump inhibitor with paclitaxel is an effective approach to overcome therapeutic resistance caused by the acidic microenvironment (Warburg effect) in tumor. In the present study a new simple, precise and selective liquid chromatography tandem mass spectrometry method was developed for quantification of paclitaxel and lansoprazole using esomeprazole as an internal standard and applied for the pharmacokinetic study of investigational paclitaxel - lansoprazole loaded PLGA nanoparticles. The developed method quantifies both the drugs simultaneously irrespective of their dissimilar stability concerns. The detection was exercised with multiple reaction-monitoring mode in positive ionization that yielded highly intense response of parent-product (m/z) transition pair 854.4 → 286.1, 370.1 → 251.9 and 346 → 198 for paclitaxel, lansoprazole and Esomeprazole respectively. The chromatographic separation was achieved using phenomenex Kinetex 5 µ C18 100A 50 × 3.0 mm column and a gradient mobile phase combination of ammonium acetate in deionized water (pH 6.8, 2 mM, w/v) and acetonitrile spiked with formic acid (1:1000, v/v ). This method showed good linearity over a concentration range of 10-320 ng/mL and 100-3200 ng/mL with correlation coefficient (R2) 0.98 and 0.94 for paclitaxel and lansoprazole respectively. Using liquid liquid extraction process both the drugs were extracted from rat plasma. The intra- and inter-day precision and accuracy values were within the variability limits and both the analytes were found to be stable throughout the freeze-thaw, auto-sampler, bench top and long term stability studies. The liquid chromatography tandem mass spectrometry method was successfully validated in accordance with United States Food and Drug administration guidelines and the results were within the acceptable limits. The liquid chromatography tandem mass spectrometry method was successfully utilized for the pharmacokinetic investigation of experimental paclitaxel - lansoprazole loaded PLGA nanoparticles in rat plasma.

High affinity radiopharmaceuticals based upon lansoprazole for PET imaging of aggregated tau in Alzheimer's disease and progressive supranuclear palsy: synthesis, preclinical evaluation, and lead selection.

Abnormally aggregated tau is the hallmark pathology of tauopathy neurodegenerative disorders and is a target for development of both diagnostic tools and therapeutic strategies across the tauopathy disease spectrum. Development of carbon-11- or fluorine-18-labeled radiotracers with appropriate affinity and specificity for tau would allow noninvasive quantification of tau burden using positron emission tomography (PET) imaging. We have synthesized [(18)F]lansoprazole, [(11)C]N-methyl lansoprazole, and [(18)F]N-methyl lansoprazole and identified them as high affinity radiotracers for tau with low to subnanomolar binding affinities. Herein, we report radiosyntheses and extensive preclinical evaluation with the aim of selecting a lead radiotracer for translation into human PET imaging trials. We demonstrate that [(18)F]N-methyl lansoprazole, on account of the favorable half-life of fluorine-18 and its rapid brain entry in nonhuman primates, favorable kinetics, low white matter binding, and selectivity for binding to tau over amyloid, is the lead compound for progression into clinical trials.

Reaction of proton pump inhibitors with model peptides results in novel products.

The proposed mechanism for proton pump inhibitors (PPIs) is that PPIs are activated at low pH to the sulfenamide form, which reacts with the sulfhydryl group of cysteine(s) at the active site of the proton pump, to produce reducible disulfide-bonded PPI-proton pump conjugates. However, this mechanism cannot explain the observations that some PPI-protein conjugates are irreducible. This study was designed to investigate the chemistry of the irreducible conjugates by mass spectrometry, using three PPIs and 17 cysteine-containing peptides. While some peptides favored the formation of reducible PPI-peptide adduct, the other peptides mainly produced irreducible adducts. Characterization of the irreducible adduct revealed that the irreducible bonding required the participation of both a sulfhydryl group and a nearby primary amino group. High resolution mass spectrometry suggested a molecular structure of the irreducible adduct. These results suggested a reaction mechanism in which the PPI pyridone form reacted with an amino group and a sulfhydryl group to form an irreducible adduct. The irreducible adduct becomes the dominant product over time because of the irreversible nature of the pyridone-mediated reaction. These findings may explain the irreducible inhibition of H/K-ATPase by PPIs and their relatively slow biological turnover in vivo. [Supplementary materials: available only at http://dx.doi.org/10.1254/jphs.13058FP].