Date of Award

2017

Degree Type

Dissertation

Degree Name

Doctor of Philosophy in Pharmaceutical Sciences

Department

Biomedical and Pharmaceutical Sciences

First Advisor

Bingfang Yan

Abstract

Sofosbuvir has been widely adopted for Hepatitis C Virus (HCV) infection therapies through its effect as HCV non-structured protein 5B (NS5B) inhibitor, which is essential for HCV particle assembly. Sofosbuvir, as a prodrug, is activated through the hydrolysis by carboxylesterase 1 (CES1) and is reported to have limited interactions with cytochrome P450 enzymes (CYP450) and p-glycoprotein, which results in less clinical drug-drug interactions. However, reports showed fatal or nephrotoxic cases that utilized a co-therapy of Sofosbuvir with an anti-Human Immunodeficiency virus (HIV) agent, tenofovir disoproxil fumarate (TDF). This study was designed to give one explanation for these case reports. Interestingly, although Sofosbuvir is a CES1 substrate, it covalently inhibited CES2, but not CES1, at an IC50 of 0.8uM, which was even more potent than reported inhibition on NS5B of HCV. Such inhibition was also proved to be caused by Sofosbuvir, but not its metabolites.

Tenofovir disoproxil fumarate (TDF) and tenofovir alafenamide fumarate (TAF) are prodrugs for tenofovir (TFV) in the therapies of Hepatitis B Virus (HBV) infections and Human Immunodeficiency Virus (HIV) infections. Both of them need to be monitored for severe hepatomegaly with steatosis. Although TDF was found to have mitochondria-depletion induced lipid metabolism dysfunction, it was not true for TAF. Therefore, we designed this study, trying to discover a possible explanation. Our research found that both TAF and TDF lead to lipid retention in Huh7 cells, with association of the induction of small heterodimer partner (SHP) expressions of both mRNA and protein. Further experiments proved that it was the prodrugs but not TFV that lead to the lipid retention and SHP induction. Moreover, TAF also showed a synergic lipid retention effect with ethanol (EtOH) co-treatment, possibly caused by the CES1-mediated ethyl transesterification pathway.

Available for download on Thursday, November 28, 2019

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