Tenofovir Disoproxil fumarate is a nucleotide reverse transcriptase inhibitor used to treat HIV and chronic Hepatitis B.In Vitro: Tenofovir shows cytotoxic effects on cell viability in HK-2 cells, with IC50 values of 9.21 and 2.77 μM at 48 and 72 h in MTT assay, respectively. Tenofovir diminishes ATP levels in HK-2 cells. Tenofovir (3.0 to 28.8 μM) increases oxidative stress and protein carbonylation in HK-2 cells. Furthermore, Tenofovir induces apoptosis in HK-2 cells, and that apoptosis is induced via mitochondrial damage. Tenofovir and M48U1 formulated in 0.25% HEC each inhibits the replication of both R5-tropic HIV-1BaL and X4-tropic HIV-1IIIb in activated PBMCs, and inhibits several laboratory strains and patient-derived HIV-1 isolates. The combined formulation of M48U1 and tenofovir in 0.25% HEC exhibits synergistic antiretroviral activity against infection with R5-tropic HIV-1BaL, and is not toxic to PBMCs[2].In Vivo: Tenofovir Disoproxil fumarate (20, 50, 140, or 300?mg/kg) administered to BLT mice, shows dose dependent activity during vaginal HIV challenge in BLT humanized mice. Tenofovir Disoproxil fumarate (50, 140, 300?mg/kg) significantly reduces HIV transmission in BLT mice. Tenofovir Disoproxil fumarate (0.5, 1.5, or 5.0 mg/kg/day, p.o.) induces a dose-dependent decline in serum viremia in woodchucks chronically infected with WHV. Tenofovir Disoproxil fumarate administration is safe and effective in the woodchuck model of chronic HBV infection.