Publications by authors named "Scott Fountain"

12 Publications

  • Page 1 of 1

A quantitative LC-MS/MS approach for monitoring 2'-fluoro-2'-deoxy-D-glucose uptake in tumor tissue.

Bioanalysis 2021 Mar 16;13(6):481-491. Epub 2021 Mar 16.

Biomedicine Design, Pfizer Worldwide Research and Development, San Diego, CA 92121, USA.

Develop a quantitative LC-MS/MS method for FDG, FDG-monophosphate, glucose and glucose-monophosphate in mouse tumor models to assist in validating the use of [F]FDG-positron emission tomography (PET) imaging for anticancer therapies in a clinical setting. Analytes were isolated from tumors by protein precipitation and detected on a Sciex API-5500 mass spectrometer. Improved assay robustness and selectivity were achieved through chromatographic separation of FDG-monophosphate from glucose-monophosphate, selection of a unique ion transition and incorporation of stable isotope labeled internal standards. In a mouse JIMT-1 tumor model, FDG-monophosphate levels measured by LC-MS/MS correlated with [F]FDG-PET imaging results. LC-MS/MS analysis of FDG-monophosphate accumulation in tumors is a cost-effective tool to gauge the translational potential of [F]FDG-PET imaging as a noninvasive biomarker in clinical studies.
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http://dx.doi.org/10.4155/bio-2020-0326DOI Listing
March 2021

11th GCC Closed Forum: cumulative stability; matrix stability; immunogenicity assays; laboratory manuals; biosimilars; chiral methods; hybrid LBA/LCMS assays; fit-for-purpose validation; China Food and Drug Administration bioanalytical method validation.

Bioanalysis 2018 Apr 27;10(7):433-444. Epub 2018 Apr 27.

Worldwide Clinical Trials, Austin, TX, USA.

The 11th Global CRO Council Closed Forum was held in Universal City, CA, USA on 3 April 2017. Representatives from international CRO members offering bioanalytical services were in attendance in order to discuss scientific and regulatory issues specific to bioanalysis. The second CRO-Pharma Scientific Interchange Meeting was held on 7 April 2017, which included Pharma representatives' sharing perspectives on the topics discussed earlier in the week with the CRO members. The issues discussed at the meetings included cumulative stability evaluations, matrix stability evaluations, the 2016 US FDA Immunogenicity Guidance and recent and unexpected FDA Form 483s on immunogenicity assays, the bioanalytical laboratory's role in writing PK sample collection instructions, biosimilars, CRO perspectives on the use of chiral versus achiral methods, hybrid LBA/LCMS assays, applications of fit-for-purpose validation and, at the Global CRO Council Closed Forum only, the status and trend of current regulated bioanalytical practice in China under CFDA's new BMV policy. Conclusions from discussions of these topics at both meetings are included in this report.
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http://dx.doi.org/10.4155/bio-2018-0014DOI Listing
April 2018

The 'blended' bioanalytical laboratory: the marriage of antibody- and instrument-based methods and expertise.

Authors:
Scott T Fountain

Bioanalysis 2014 Mar;6(6):717-9

Pfizer Worldwide R&D, 10646 Science Center Drive, San Diego, CA 92121, USA.

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http://dx.doi.org/10.4155/bio.14.23DOI Listing
March 2014

Tissue bioanalysis of biotherapeutics and drug targets to support PK/PD.

Bioanalysis 2012 Nov;4(21):2589-604

Pharmacokinetics Dynamics & Metabolism, Pfizer Inc., 1 Burtt Road, Andover, MA 01810, USA.

Contemporary drug discovery leverages quantitative modeling and simulation with increasing emphasis, both to gain deeper knowledge of drug targets and mechanisms as well as improve predictions between preclinical models and clinical applications, such as first-in-human dose projections. Proliferation of novel biotherapeutic modalities increases the need for applied PK/PD modeling as a quantitative tool to advance new therapies. Of particular relevance is the understanding of exposure, target binding and associated pharmacology at the target site of interest. Bioanalytical methods are key to informing PK/PD models and require assessment of both PK and PD end points. Where targets are sequestered in tissues (noncirculating), the ability to quantitatively measure drug or biomarker in tissue compartments becomes particularly important. This perspective provides an overview of contemporary applications of quantitative bioanalysis in tissue compartments as applied to PK and PD assessments associated with novel biotherapeutics. Case studies and key references are provided.
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http://dx.doi.org/10.4155/bio.12.234DOI Listing
November 2012

How current understanding of clearance mechanisms and pharmacodynamics of therapeutic proteins can be applied for evaluation of their drug-drug interaction potential.

Drug Metab Dispos 2011 Oct 18;39(10):1779-83. Epub 2011 Jul 18.

Pfizer Worldwide Research and Development, San Diego, CA 92121, USA.

Increasing use of therapeutic proteins (TPs) in polypharmacy settings calls for more in-depth understanding of the biological interactions that can lead to increased toxicity or loss of pharmacological effect. Factors such as patient population, medications that are likely to be coadministered in that population, clearance mechanisms of a TP, and concomitant drugs have to be taken into account to determine the potential for drug-drug interactions (DDIs). The most well documented TP DDI mechanism involves cytokine-mediated changes in drug-metabolizing enzymes. Because of the limitations of the current preclinical models for addressing this type of DDI, clinical evaluation is currently the most reliable approach. Other DDI mechanisms need to be addressed on a case-by-case basis. These include altered clearance of TPs resulting from the changes in the target protein levels by the concomitant medication, displacement of TPs from binding proteins, modulation of Fcγ receptor expression, and others. The purpose of this review is to introduce the approach used by Pfizer scientists for evaluation of the DDI potential of novel TP products during drug discovery and development.
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http://dx.doi.org/10.1124/dmd.111.040808DOI Listing
October 2011

The validation of a simple LC/MS/MS method for determining the level of mevalonic acid in human plasma.

Biomed Chromatogr 2011 Mar;25(3):323-9

Department of Pharmacokinetics, Dynamics, and Metabolism, Pfizer Inc., La Jolla, CA, USA.

A simple plasma extraction method coupled with liquid chromatography-tandem mass spectrometry (LC/MS/MS) detection was developed and validated for the analysis of endogenous mevalonic acid (MVA), a biomarker indicative of the rate of cholesterol biosynthesis, in human plasma samples. The analyte was extracted from the plasma matrix using a straightforward liquid-liquid sample preparation procedure. The extract supernatants were evaporated, reconstituted in aqueous solvent and injected into the LC/MS/MS system without further processing. The chromatographic separation was achieved on a reverse-phase high-performance liquid chromatography column. The accuracy and precision of the method was determined over the concentration range 0.25-25 ng/mL MVA from human plasma extracts in three validation batch runs. Inter-assay precision (%CV) and accuracy (%RE) of the quality control samples were ≤7.00% (at lower limit quality control) and ≤6.10%, respectively. The sensitivity and throughput of this assay was significantly improved relative to previously published methods, resulting in smaller sample requirements and shorter analysis time. Assay results from a clinical study following the oral administration of an exploratory statin demonstrate that this procedure could potentially be used in the investigation of therapies associated with hypercholesterolemia.
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http://dx.doi.org/10.1002/bmc.1449DOI Listing
March 2011

Diethylation labeling combined with UPLC/MS/MS for simultaneous determination of a panel of monoamine neurotransmitters in rat prefrontal cortex microdialysates.

Anal Chem 2008 Dec;80(23):9195-203

Pfizer Global Research & Development, Groton Laboratories, Pfizer Inc., Groton, Connecticut 06340, USA.

The primary challenge associated with the development of an LC/MS/MS-based assay for simultaneous determination of biogenic monoamine neurotransmitters such as norepinephrine (NE), dopamine (DA), serotonin (5-HT), and normetanephrine (NM) in rat brain microdialysates is to improve detection sensitivity. In this work, a UPLC/ MS/MS-based method combined with a diethyl labeling technique was developed for simultaneous determination of a panel of monoamines in rat prefrontal cortex microdialysates. The chromatographic run time is 3.5 min/ sample. The limits of detection of the UPLC/MS/MS-based method for NE, DA, 5-HT/ and NM, with/without diethyl labeling of monoamines, are 0.005/0.4 (30/2367 pM), 0.005/0.1 (33/653 pM), 0.005/0.2 (28/1136 pM), and 0.002/0.2 ng/mL (11/1092 pM), respectively. Diethyl labeling of amino groups of monoamines affords 20-100 times increased detection sensitivity of corresponding native monoamines during the UPLC/MS/MS analysis. This could result from the following: (1) improved fragmentation patterns; (2) increased hydrophobicity and concomitantly increased ionization efficiency in ESI MS and MS/MS analysis; (3) reduced matrix interference. This labeling reaction employs a commercially available reagent, acetaldehyde-d4, to label the amine groups on the monoamines via reductive amination. It is also simple, fast (approximately 25-min reaction time), specific, and quantitative under mild reaction conditions. Data are also presented from the application of this assay to monitor the drug-induced changes of monoamine concentrations in rat prefrontal cortex microdialysate samples followed by administration of SKF 81297, a selective D1 dopamine receptor agonist known to elevate the extracellular level of the neurotransmitters DA and NE in the central nervous system.
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http://dx.doi.org/10.1021/ac801339zDOI Listing
December 2008

Clinical validation of an immunoaffinity LC-MS/MS assay for the quantification of a collagen type II neoepitope peptide: A biomarker of matrix metalloproteinase activity and osteoarthritis in human urine.

Anal Biochem 2007 Oct 6;369(1):41-53. Epub 2007 May 6.

Pfizer Global Research and Development, Michigan Laboratories, Ann Arbor, MI 48105, USA.

The degradation of type II collagen has been associated with the pathology of osteoarthritis (OA). Matrix metalloproteinases (MMPs) are enzymes that are responsible for catalyzing the degradation of collagen and, therefore, are pursued as potential targets for the treatment of OA. Collagen-derived peptides identified as a reflection of in vivo MMP activity have been investigated as target biomarkers of MMP activity as well as potential biomarkers of OA disease state and/or progression. An immunoaffinity liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay developed for the quantification of the most abundant urinary type II collagen neoepitope (uTIINE) peptide, a 45-mer with 5 HO-proline residues resulting from MMP-13-catalyzed degradation, was validated for clinical use. Validation experiments were designed with attention to specific challenges related to quantification of endogenous analytes. The validated method is sensitive, selective, accurate (<15% relative error) and precise (<15% coefficient of variation) over a linear range of 0.156-7.50 ng/ml. Sample stability and inter- and intrasubject variability were evaluated in the urine of normal and OA populations. The method was applied to analyze human urine samples from clinical studies investigating the utility of uTIINE as a potential biomarker for OA.
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http://dx.doi.org/10.1016/j.ab.2007.05.002DOI Listing
October 2007

Fit-for-purpose method development and validation for successful biomarker measurement.

Pharm Res 2006 Feb 12;23(2):312-28. Epub 2006 Jan 12.

Formerly MDS Pharma Services, Lincoln, Nebraska, USA.

Despite major advances in modern drug discovery and development, the number of new drug approvals has not kept pace with the increased cost of their development. Increasingly, innovative uses of biomarkers are employed in an attempt to speed new drugs to market. Still, widespread adoption of biomarkers is impeded by limited experience interpreting biomarker data and an unclear regulatory climate. Key differences preclude the direct application of existing validation paradigms for drug analysis to biomarker research. Following the AAPS 2003 Biomarker Workshop (J. W. Lee, R. S. Weiner, J. M. Sailstad, et al. Method validation and measurement of biomarkers in nonclinical and clinical samples in drug development. A conference report. Pharm Res 22:499-511, 2005), these and other critical issues were addressed. A practical, iterative, "fit-for-purpose" approach to biomarker method development and validation is proposed, keeping in mind the intended use of the data and the attendant regulatory requirements associated with that use. Sample analysis within this context of fit-for-purpose method development and validation are well suited for successful biomarker implementation, allowing increased use of biomarkers in drug development.
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http://dx.doi.org/10.1007/s11095-005-9045-3DOI Listing
February 2006

A validated LC/MS/MS method for the quantification of pyrrole-2,3,5-tricarboxylic acid (PTCA), a eumelanin specific biomarker, in human skin punch biopsies.

J Chromatogr B Analyt Technol Biomed Life Sci 2005 Nov 31;826(1-2):31-40. Epub 2005 Aug 31.

Biomarker Implementation Group, Department of Pharmacokinetics, Dynamics & Metabolism, Pfizer Global Research and Development, 2800 Plymouth Road, Ann Arbor, MI 48105, USA.

A novel skin tissue extraction method coupled with liquid chromatography-tandem mass spectrometry (LC/MS/MS) detection was developed and validated for the analysis of endogenous pyrrole-2,3,5-tricarboxylic acid (PTCA), a eumelanin specific biomarker, in human skin punch biopsies. The analyte is extracted from the matrix (2 mm skin punch biopsies) using a simple oxidative degradation procedure. The extract supernatants are evaporated, reconstituted in mobile phase solvent, and injected into the LC/MS/MS system without further derivatization. The chromatographic separation is achieved on a reverse phase high performance liquid chromatography (HPLC) column. The accuracy and precision of the method was determined over the concentration range of 1-1000 ng/mL PTCA from human skin extracts in three validation batch runs. Inter-assay precision (%CV) and accuracy (%R.E.) of the quality control samples were
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http://dx.doi.org/10.1016/j.jchromb.2005.08.002DOI Listing
November 2005

Development and validation of an LC/MS/MS procedure for the quantification of endogenous myo-inositol concentrations in rat brain tissue homogenates.

Anal Chem 2004 Aug;76(16):4901-8

myo-Inositol is being investigated as a biomarker to monitor disease states involving the central nervous system. We have developed and validated a quantitative method to study endogenous myo-inositol metabolism in rat brain tissue. Tissue samples were homogenized, and their myo-inositol content was determined using spiked calibration curves and mass spectrometry. The assay was validated on an LC/MS/MS platform, and specificity was evaluated using accurate mass measurements. A novel chiral LC/MS/MS method was also developed to resolve myo-inositol from other endogenous inositol epimers and confirm the selectivity of the quantitative procedure. The validated method is selective, convenient, precise (<15% RSD), accurate (<15% RE), and sensitive over a linear range of 0.100-100 microg/mL. This method could potentially be used as an instrument for monitoring pathological conditions related to psychotherapeutics, as well as a tool for screening curative pharmaceuticals for efficacy.
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http://dx.doi.org/10.1021/ac049746wDOI Listing
August 2004

Investigation of EDTA anticoagulant in plasma to improve the throughput of liquid chromatography/tandem mass spectrometric assays.

Rapid Commun Mass Spectrom 2003 ;17(10):1065-70

Department of Pharmacokinetics Dynamics and Metabolism, Pfizer Global R&D, Ann Arbor Laboratories, 2800 Plymouth Road, Ann Arbor, MI 48105, USA.

In this study, EDTA and heparin are compared as anticoagulants with respect to their efficiency in preventing clot formation in plasma samples that were subsequently analyzed by liquid chromatography/tandem mass spectrometry (LC/MS/MS). A pilot in vivo pharmacokinetic study for the drug chlorpheniramine was conducted in which both EDTA and heparin plasma samples were collected simultaneously. All conditions except the anticoagulant were held constant during the pharmacokinetic study. Bioanalytical results were compared from samples transferred by manual pipette and by an automated liquid handler workstation. The concentration of chlorpheniramine in samples was determined by LC/MS/MS. Results from the analysis of variances (ANOVA) of log-transformed plasma chlorpheniramine concentrations were used to calculate 90% confidence intervals for the ratio least-squares mean values for anticoagulants and for transfer methods. Analytical concentrations of the drug chlorpheniramine were equivalent in heparin- and EDTA-containing plasma. Results suggest that the failure rate for transfer of EDTA plasma (50 micro L by automated workstation or manually) is less than that for heparinized plasma. As a consequence of these results, the vast majority of plasma samples in our laboratories are now collected in EDTA, which allows for use of automated sample transfer resulting in a three-fold timesaving over manual transfer using a single-channel pipette. The ability to use automation has resulted in improved efficiency and cost savings.
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http://dx.doi.org/10.1002/rcm.1023DOI Listing
May 2003