Tenofovir alafenamide hemifumarate (GS-7340 hemifumarate) is an investigational oral prodrug of Tenofovir. Tenofovir is a HIV-1 nucleotide reverse transcriptase inhibitor. HIV-1, NRTIs[1]

Tenofovir alafenamide hemifumarate (GS-7340 hemifumarate) antiviral activities are similar across all cell types, ranging from 5 to 7 nM, while the CC50 varies from 4.7 to 42 μM for MT-4 and MT-2 cells, respectively. The antiviral activity of TAF is evaluated against a panel of HIV-1 and HIV-2 isolates, including HIV-1 group M subtypes A to G, as well as group N and O isolates. Overall, for the 29 primary HIV-1 isolates tested in PBMCs, TAF EC50s range from 0.1 to 12 nM, with a mean EC50 of 3.5 nM compared to a mean EC50 of 11.8 nM for AZT, which is used as an internal control. For the HIV-2 isolates, the mean EC50s are 1.8 nM for TAF and 6.4 nM for AZT[2].

Tenofovir alafenamide hemifumarate (GS-7340 hemifumarate) is an amidate prodrug of Tenofovir with good oral bioavailability and increases plasma stability compared to Tenofovir disoproxil fumarate (TDF) [1].

[1]. Birkus G, et al. Intracellular Activation of Tenofovir Alafenamide and the Effect of Viral and Host Protease Inhibitors. Antimicrob Agents Chemother. 2015 Oct 26;60(1):316-22. [2]. Callebaut C, et al. In Vitro Virology Profile of Tenofovir Alafenamide, a Novel Oral Prodrug of Tenofovir with Improved Antiviral Activity Compared to That of Tenofovir Disoproxil Fumarate. Antimicrob Agents Chemother. 2015 Oct;59(10):5909-16.