ABSTRACT: Almost 38 million individuals worldwide are infected with the human immunodeficiency virus (HIV)
causative agent of acquired immunodeficiency disease (AIDS), 1.2 million of them being Americans. With no
vaccine and no cure available, HIV/AIDS patients must take anti-HIV drugs throughout the rest of their lives. Thus,
the long-term use of highly active antiretroviral therapy (HAART)drugs that revolutionized HIV/AIDS
AIDS patients can also live as long as non-infected people, has been
accompanied by serious mitochondrial toxicities, with fatal consequences that led to discontinuation of many of the
early effective nucleoside reverse transcriptase (RT) inhibitor (NRTIs) backbone components, like ddC and d4T. The
development of the nucleotide RT inhibitors (NtRTIs) particularly tenofovir (TFV), has been innovative in the HIV RT
inhibitors field, to the extent that it has gained widespread use worldwide and is incorporated into almost all first-line
HIV/AIDS therapeutic combination regimens, as well as used for pre-exposure prophylactics (PrEP). TFV is
marketed as two prodrugs tenofovir disoproxil fumarate (TDF) and tenofovir alafenamide (TAF). However, long-term
use of the TDF prodrug causes kidney toxicity stemming from the active parent TFV. TFV-associated kidney toxicity
is said to have constituted the single
referrals for specialist renal services
when TFD was first introduced. Moreover, this renal decline was irreversible in about 30 % of patients even after
cessation of TFV therapy. Although, TAF, which was introduced more recently is more potent and less toxic than
TDF, case studies show it has kidney toxicity potential which may manifest upon long-term use. Moreover, it causes
troubling weight gain that could exacerbate metabolic syndrome. These problems mean that TAF cannot always
replace TDF. The mechanisms of TFV toxicity are not well understood, but damage to renal proximal tubular
mitochondrial has been strongly implicated. The goal of this research is to gain better understanding and develop
effective approaches to addressing TFV kidney toxicity. The specific aims are: 1) to confirm that human
mitochondrial membranes express functional organic anion transporters 1 and 3 (hOAT1 and hOAT3), and show
their ability to import TFV into mitochondria, and, 2) to develop and investigate the protective ability of
mitochondrially targeted hOAT1 and 3 inhibitor prodrugs against TFV toxicity. We have demonstrated the
expression of the TFV transporters hOAT1 and hOAT3 in the mitochondrial membranes of human renal proximal
tubule epithelial cells, supporting our hypothesis that TFV enters mitochondria through hOAT1 and 3 to cause
mitochondrial toxicity. For aim 2, we have synthesized an initial hOAT1, and 3 inhibitor prodrug and shown that it is
protective against TFV mitochondrial toxicity. A comprehensive multidisciplinary approach involving medicinal
chemistry, biochemistry, functional genomics, and pharmacology will be applied, using human kidney proximal
tubule cells. Our initially synthesized targeted prodrug reverses TFV-induced mitochondrial toxicity. The success of
this project will give new insights into TFV-induced toxicity and provide biological probes and/or potential drug leads.