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Molecular Dynamics Guided Design of Tocoflexol: A New Radioprotectant Tocotrienol with Enhanced Bioavailability

Authors

  • Cesar M. Compadre,

    Corresponding author
    1. Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR, USA
    • Correspondence to: Cesar M. Compadre, Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.

      E-mail: cmcompadre@uams.edu

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  • Awantika Singh,

    1. Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR, USA
    2. UAMS/UALR Joint Bioinformatics Graduate Program, University of Arkansas for Medical Sciences, Little Rock, AR, USA
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  • Shraddha Thakkar,

    1. UAMS/UALR Joint Bioinformatics Graduate Program, University of Arkansas for Medical Sciences, Little Rock, AR, USA
    2. Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR, USA
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  • Guangrong Zheng,

    1. Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR, USA
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  • Philip J. Breen,

    1. Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR, USA
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  • Sanchita Ghosh,

    1. Armed Forces Radiobiology Research Institute, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
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  • Mahmoud Kiaei,

    1. Department of Neurobiology and Developmental Sciences, University of Arkansas for Medical Sciences, Little Rock, AR, USA
    2. Center for Translational Neuroscience, University of Arkansas for Medical Sciences, Little Rock, AR, USA
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  • Marjan Boerma,

    1. Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR, USA
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  • Kottayil I. Varughese,

    1. Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR, USA
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  • Martin Hauer-Jensen

    1. Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR, USA
    2. Surgical Service, Central Arkansas Veterans Healthcare System, Little Rock, AR, USA
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Abstract

Preclinical Research

There is a pressing need to develop safe and effective radioprotector/radiomitigator agents for use in accidental or terrorist-initiated radiological emergencies. Naturally occurring vitamin E family constituents, termed tocols, that include the tocotrienols, are known to have radiation-protection properties. These agents, which work through multiple mechanisms, are promising radioprotectant agents having minimal toxicity. Although α-tocopherol (AT) is the most commonly studied form of vitamin E, the tocotrienols are more potent than AT in providing radioprotection and radiomitigation. Unfortunately, despite their very significant radioprotectant activity, tocotrienols have very short plasma half-lives and require dosing at very high levels to achieve necessary therapeutic benefits. Thus, it would be highly desirable to develop new vitamin E analogues with improved pharmacokinetic properties, specifically increased elimination half-life and increased area under the plasma level versus time curve. The short elimination half-life of the tocotrienols is related to their low affinity for the α-tocopherol transfer protein (ATTP), the protein responsible for maintaining the plasma level of the tocols. Tocotrienols have less affinity for ATTP than does AT, and thus have a longer residence time in the liver, putting them at higher risk for metabolism and biliary excretion. We hypothesized that the low-binding affinity of tocotrienols to ATTP is due to the relatively more rigid tail structure of the tocotrienols in comparison with that of the tocopherols. Therefore, compounds with a more flexible tail would have better binding to ATTP and consequently would have longer elimination half-life and, consequently, an increased exposure to drug, as measured by area under the plasma drug level versus time curve (AUC). This represents an enhanced residence of drug in the systemic circulation. Based on this hypothesis, we developed a new class of vitamin E analogues, the tocoflexols, which maintain the superior bioactivity of the tocotrienols with the potential to achieve the longer half-life and larger AUC of the tocopherols.

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