title: 4'-modified nucleoside analogs: potent inhibitors active against entecavir-resistant hepatitis B virus.
abstract: Certain nucleoside/nucleotide reverse transcriptase (RT) inhibitors (NRTIs) are effective against human immunodeficiency virus type 1 (HIV-1) and hepatitis B virus (HBV). However, both viruses often acquire NRTI resistance, making it crucial to develop more-potent agents that offer profound viral suppression. Here, we report that 4'-C-cyano-2-amino-2'-deoxyadenosine (CAdA) is a novel, highly potent inhibitor of both HBV (half maximal inhibitory concentration [IC50 ] = 0.4 nM) and HIV-1 (IC50  = 0.4 nM). In contrast, the approved anti-HBV NRTI, entecavir (ETV), potently inhibits HBV (IC50  = 0.7 nM), but is much less active against HIV-1 (IC50  = 1,000 nM). Similarly, the highly potent HIV-1 inhibitor, 4'-ethynyl-2-fluoro-2'-deoxyadenosine (EFdA; IC50  = 0.3 nM) is less active against HBV (IC50  = 160 nM). Southern analysis using Huh-7 cells transfected with HBV-containing plasmids demonstrated that CAdA was potent against both wild-type (IC50  = 7.2 nM) and ETV-resistant HBV (IC50  = 69.6 nM for HBVETV-RL180M/S202G/M204V), whereas ETV failed to reduce HBVETV-RL180M/S202G/M204V DNA even at 1 μM. Once-daily peroral administration of CAdA reduced HBVETV-RL180M/S202G/M204V viremia (P = 0.0005) in human-liver-chimeric/ HBVETV-RL180M/S202G/M204V-infected mice, whereas ETV completely failed to reduce HBVETV-RL180M/S202G/M204V viremia. None of the mice had significant drug-related body-weight or serum human-albumin concentration changes. Molecular modeling suggests that a shallower HBV-RT hydrophobic pocket at the polymerase active site can better accommodate the slightly shorter 4'-cyano of CAdA-triphosphate (TP), but not the longer 4'-ethynyl of EFdA-TP. In contrast, the deeper HIV-1-RT pocket can efficiently accommodate the 4'-substitutions of both NRTIs. The ETV-TP's cyclopentyl ring can bind more efficiently at the shallow HBV-RT binding pocket.
  
  
  CONCLUSIONS
  These data provide insights on the structural and functional associations of HBV- and HIV-1-RTs and show that CAdA may offer new therapeutic options for HBV patients.
authors.affiliation: Experimental Retrovirology Section, HIV and AIDS Malignancy Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Takamatsu
authors.affiliation: Department of Virology & Liver Unit, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
authors.forename: Yasuhito
authors.initials: Y
authors.lastname: Tanaka
authors.affiliation: Research Institute & Center for Clinical Sciences, National Center for Global Health and Medicine, Tokyo, Japan.|Department of Pharmaceutical Sciences, Nihon Pharmaceutical University, Saitama, Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Kohgo
authors.affiliation: Department of Virology & Liver Unit, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
authors.forename: Shuko
authors.initials: S
authors.lastname: Murakami
authors.affiliation: Molecular Microbiology & Immunology, Biochemistry, School of Medicine and Bond Life Sciences Center, University of Missouri, Columbia, MO.
authors.forename: Kamalendra
authors.initials: K
authors.lastname: Singh
authors.affiliation: Experimental Retrovirology Section, HIV and AIDS Malignancy Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD.
authors.forename: Debananda
authors.initials: D
authors.lastname: Das
authors.affiliation: Biostatistics and Data Management Section, National Cancer Institute, National Institutes of Health, Bethesda, MD.
authors.forename: David J
authors.initials: DJ
authors.lastname: Venzon
authors.affiliation: Departments of Hematology, Rheumatology, and Clinical Immunology & Infectious Disease, Kumamoto University Graduate School of Medical Sciences, Kumamoto, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Amano
authors.affiliation: Research Institute & Center for Clinical Sciences, National Center for Global Health and Medicine, Tokyo, Japan.|Departments of Hematology, Rheumatology, and Clinical Immunology & Infectious Disease, Kumamoto University Graduate School of Medical Sciences, Kumamoto, Japan.
authors.forename: Nobuyo
authors.initials: N
authors.lastname: Higashi-Kuwata
authors.affiliation: Experimental Retrovirology Section, HIV and AIDS Malignancy Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD.|Departments of Hematology, Rheumatology, and Clinical Immunology & Infectious Disease, Kumamoto University Graduate School of Medical Sciences, Kumamoto, Japan.|Department of Medical Technology, Kumamoto Health Science University, Kumamoto, Japan.
authors.forename: Manabu
authors.initials: M
authors.lastname: Aoki
authors.affiliation: Experimental Retrovirology Section, HIV and AIDS Malignancy Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD.
authors.forename: Nicole S
authors.initials: NS
authors.lastname: Delino
authors.affiliation: Department of Virology & Liver Unit, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
authors.forename: Sanae
authors.initials: S
authors.lastname: Hayashi
authors.affiliation: Department of Experimental Pathology & Tumor Biology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Takahashi
authors.affiliation: Research Institute & Center for Clinical Sciences, National Center for Global Health and Medicine, Tokyo, Japan.
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Sukenaga
authors.affiliation: Department of Pharmaceutical Sciences, Nihon Pharmaceutical University, Saitama, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Haraguchi
authors.affiliation: Molecular Microbiology & Immunology, Biochemistry, School of Medicine and Bond Life Sciences Center, University of Missouri, Columbia, MO.
authors.forename: Stefan G
authors.initials: SG
authors.lastname: Sarafianos
authors.affiliation: Experimental Retrovirology Section, HIV and AIDS Malignancy Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD.|Research Institute & Center for Clinical Sciences, National Center for Global Health and Medicine, Tokyo, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Maeda
authors.affiliation: Experimental Retrovirology Section, HIV and AIDS Malignancy Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD.|Research Institute & Center for Clinical Sciences, National Center for Global Health and Medicine, Tokyo, Japan.|Departments of Hematology, Rheumatology, and Clinical Immunology & Infectious Disease, Kumamoto University Graduate School of Medical Sciences, Kumamoto, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Mitsuya
mesh_terms: D000818:Animals; D003839:Deoxyadenosines / Q000494:pharmacology*; D024882:Drug Resistance, Viral; D006147:Guanine / Q000031:analogs & derivatives / Q000494:pharmacology; D015497:HIV-1 / Q000187:drug effects; D006515:Hepatitis B virus / Q000187:drug effects*; D051379:Mice
chemical_list: C000604238:4'-C-cyano-2-amino-2'-deoxyadenosine; D003839:Deoxyadenosines; C413685:entecavir; D006147:Guanine