Metabolic basis for lipid abnormality with anti-HIV tenofovir prodrugs

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Human immunodeficiency virus (HIV) continues to be a major global health issue. Remarkably, AIDS-related death (acquired immunodeficiency syndrome) has decreased in recent years. Alarmingly, chronic liver diseases have become major causes of mortality among HIV patients, largely due to hepatotoxicity of anti-HIV drugs, widespread alcohol abuse and coinfection of hepatitis viruses such as hepatitis B virus (HBV). Tenofovir disoproxil and tenofovir alafenamide are major anti-HIV medicines and also used to treat HBV infection. Both tenofovir drugs are ester prodrugs and hydrolytically activated, primarily by carboxylesterases (CES), an enzyme system with large individual variability due to expression and/or genetic polymorphism. Tenofovir prodrugs are generally well tolerated, but have been associated with renal/bone toxicity and steatosis. Our Preliminary Study has shown that tenofovir prodrugs increased lipid retention and tenofovir alafenamide underwent transesterification by carboxylesterase-1 in the presence of ethanol. The central hypo- thesis of the project is that carboxylesterases determine therapeutic activation and steatotic potential of tenofovir prodrugs through hydrolysis, transesterification and inhibition. The Specific Aims are: (1) to signify catalytic actions of carboxylesterases for activation and safety, and (2) to investigate the steatotic potential of tenofovir prodrugs. A large number of human samples (>300) will be assayed for the hydrolysis of tenofovir prodrugs in the presence and absence of ethanol or a commonly coadministered drug to ascertain the interplay of hydrolytic activation over transesterification and inhibition. The role of carboxylesterases in the interplay will be confirmed in cells selectively knocked out or overexpressing a carboxylesterase. To specify the steatotic potential of tenofovir prodrugs and their steatotic interaction with ethanol, hepatically xenografted mice with these lines will be dosed with tenofovir alafenamide and fed with ethanol-containing diet, and the steatosis will be monitored. In addition, transcriptome of tenofovir prodrugs will be determined as a function of hydrolysis to shed light on how tenofovir prodrugs (not their hydrolytic metabolite) are engaged in steatotic development. The focus on the carboxylesterase system, related to anti-HIV/HBV therapy, is conceptually innovative and clinically significant. Overall, the scientific premise is strong, the clinical relevance is high, and many studies (e.g., steatosis-favoring transcriptome) will have lasting and broad impact. Finally, this laboratory has a long standing interest in carboxylesterases. Decades of work position us well to progress this project.