title: Characterization of HIV-1 Resistance to Tenofovir Alafenamide In Vitro.
abstract: Tenofovir alafenamide (TAF) is an investigational prodrug of the HIV-1 nucleotide reverse transcriptase (RT) inhibitor (NtRTI) tenofovir (TFV), with improved potency and drug delivery properties over the current prodrug, tenofovir disoproxil fumarate (TDF). TAF is currently in phase 3 clinical studies for the treatment of HIV-1 infection, in combination with other antiretroviral agents. Phase 1 and 2 studies have shown that TAF was associated with increased peripheral blood mononuclear cell (PBMC) drug loading and increased suppression of HIV-1 replication compared to treatment with TDF. In this study, selection of in vitro resistance to both TAF and the parent compound, TFV, led to the emergence of HIV-1 with the K65R amino acid substitution in RT with 6.5-fold-reduced susceptibility to TAF. Although TAF is more potent than TFV in vitro, the antiviral susceptibilities to TAF and TFV of a large panel of nucleoside/nucleotide RT inhibitor (NRTI)-resistant mutants were highly correlated (R(2) = 0.97), indicating that the two compounds have virtually the same resistance profile when assessed as fold change from the wild type. TAF showed full antiviral activity in PBMCs against primary HIV-1 isolates with protease inhibitor, nonnucleoside RT inhibitor (NNRTI), or integrase strand transfer inhibitor resistance but reduced activity against isolates with extensive NRTI resistance amino acid substitutions. However, the increased cell loading of TFV with TAF versus TDF observed in vivo suggests that TAF may retain activity against TDF-resistant mutant viruses.
authors.affiliation: Clinical Virology, Gilead Sciences, Inc., Foster City, California, USA Nicolas.Margot@gilead.com.
authors.forename: Nicolas A
authors.initials: NA
authors.lastname: Margot
authors.affiliation: Clinical Virology, Gilead Sciences, Inc., Foster City, California, USA.
authors.forename: Audun
authors.initials: A
authors.lastname: Johnson
authors.affiliation: Clinical Virology, Gilead Sciences, Inc., Foster City, California, USA.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Miller
authors.affiliation: Clinical Virology, Gilead Sciences, Inc., Foster City, California, USA.
authors.forename: Christian
authors.initials: C
authors.lastname: Callebaut
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D000409:Alanine; D019943:Amino Acid Substitution; D019380:Anti-HIV Agents / Q000378:metabolism / Q000494:pharmacology*; D001711:Biotransformation; D002460:Cell Line; D002999:Clone Cells; D024882:Drug Resistance, Viral / Q000235:genetics*; D004355:Drug Stability; D054303:HIV Reverse Transcriptase / Q000037:antagonists & inhibitors / Q000378:metabolism; D015497:HIV-1 / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D006801:Humans; D020128:Inhibitory Concentration 50; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000473:pathology / Q000821:virology; D008214:Lymphocytes / Q000187:drug effects / Q000473:pathology / Q000821:virology; D008826:Microbial Sensitivity Tests; D009154:Mutation; D061251:Primary Cell Culture; D011355:Prodrugs / Q000378:metabolism / Q000494:pharmacology*; D000068698:Tenofovir / Q000378:metabolism / Q000494:pharmacology* / Q000031:analogs & derivatives; D014779:Virus Replication / Q000187:drug effects
chemical_list: D019380:Anti-HIV Agents; D011355:Prodrugs; D000068698:Tenofovir; C514824:reverse transcriptase, Human immunodeficiency virus 1; D054303:HIV Reverse Transcriptase; C442442:tenofovir alafenamide; D000225:Adenine; D000409:Alanine