title: High resistance barrier to tenofovir alafenamide is driven by higher loading of tenofovir diphosphate into target cells compared to tenofovir disoproxil fumarate.
abstract: Tenofovir alafenamide (TAF) is a new oral prodrug of tenofovir (TFV) recently approved for the treatment of HIV-1 as part of the single-tablet regimen containing elvitegravir, cobicistat, emtricitabine, and TAF. Clinical dosing with TAF vs. tenofovir disoproxil fumarate (TDF) has shown improved bone and kidney safety, and has been associated with an increased concentration of the anti-HIV active moiety tenofovir diphosphate (TFV-DP) in the PBMCs of treated patients and a reduction of TFV systemic exposure. We have studied the potential benefit of this increased concentration of TFV-DP observed clinically in an in vitro model system. Using a newly developed virus breakthrough assay with TAF exposure set at physiological concentrations, we show that HIV-1 clinical isolates harboring TFV resistance mutations such as K65R, 3 or 4 thymidine-analog mutations (TAMs), Q151M/K65R, or T69 insertion complex could be inhibited by TAF, but not by TFV when used at clinically relevant concentrations for TDF. These data suggest that the inhibitory quotient (IQ) of TAF is projected to be higher than the IQ of TDF, and that TAF has the potential to inhibit viruses containing TDF resistance in the clinic.
authors.affiliation: Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA, 94404, USA. Electronic address: nicolas.margot@gilead.com.
authors.forename: Nicolas A
authors.initials: NA
authors.lastname: Margot
authors.affiliation: Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA, 94404, USA.
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA, 94404, USA.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Miller
authors.affiliation: Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA, 94404, USA.
authors.forename: Christian
authors.initials: C
authors.lastname: Callebaut
mesh_terms: D019380:Anti-HIV Agents / Q000737:chemistry / Q000494:pharmacology*; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D024882:Drug Resistance, Viral; D015658:HIV Infections / Q000821:virology*; D015497:HIV-1 / Q000187:drug effects* / Q000235:genetics; D006801:Humans; D008826:Microbial Sensitivity Tests; D009154:Mutation; D012367:RNA, Viral; D011995:Recombination, Genetic; D018894:Reverse Transcriptase Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D000068698:Tenofovir / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology*; D019562:Viral Load
chemical_list: D019380:Anti-HIV Agents; D012367:RNA, Viral; D018894:Reverse Transcriptase Inhibitors; D000068698:Tenofovir
keywords: HIV-1; Resistance; Tenofovir alafenamide; Tenofovir diphosphate; Tenofovir disoproxil fumarate