Tenofovir alafenamide for COVID-19

The persistent evolution of SARS-CoV-2 necessitates novel antiviral strategies. This study evaluated the anti-HIV prodrugs tenofovir disoproxil fumarate (TDF) and tenofovir alafenamide (TAF) for repurposing against SARS-CoV-2, assessing key pharmacological indices (CC50, EC50, cytostatic effect, and therapeutic window). In vitro screening in Vero E6 cells measured cytotoxicity (via CCK-8/MTT assays) and antiviral activity against Kazakh B.1 and Wuhan strains. TDF (50 µg/mL) reduced high viral loads (MOI 2) by ~2 log10 (100% inhibition), with minimal cytotoxicity (≥75% viability). TAF achieved near-complete suppression (100% inhibition) at 50 µg/mL, exhibiting dose-dependent inhibition (68–100%) at lower viral loads (MOI 0.01). Both prodrugs showed enhanced antiviral activity with prolonged exposure (96 h). Synergy assessments demonstrated favourable combination indices (CI < 1). Electron microscopy confirmed virion integrity post-treatment. These findings highlight TDF and TAF as promising candidates against SARS-CoV-2, with particular potential for targeting lymphoid reservoirs—sites implicated in persistent viral reservoirs that may contribute to long COVID pathogenesis. Further clinical validation is warranted.

AbstractTo attain promising pharmacotherapies, researchers have applied drug repurposing (DR) techniques to discover the candidate medicines to combat the coronavirus disease 2019 (COVID-19) outbreak. Although many DR approaches have been introduced for treating different diseases, only structure-based DR (SBDR) methods can be employed as the first therapeutic option against the COVID-19 pandemic because they rely on the rudimentary information about the diseases such as the sequence of the severe acute respiratory syndrome coronavirus 2 genome. Hence, to try out new treatments for the disease, the first attempts have been made based on the SBDR methods which seem to be among the proper choices for discovering the potential medications against the emerging and re-emerging infectious diseases. Given the importance of SBDR approaches, in the present review, well-known SBDR methods are summarized, and their merits are investigated. Then, the databases and software applications, utilized for repurposing the drugs against COVID-19, are introduced. Besides, the identified drugs are categorized based on their targets. Finally, a comparison is made between the SBDR approaches and other DR methods, and some possible future directions are proposed.