1 Experimental Retrovirology Section, HIV and AIDS Malignancy Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD
2 Department of Virology & Liver Unit, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan
3 Research Institute & Center for Clinical Sciences, National Center for Global Health and Medicine, Tokyo, Japan
4 Department of Pharmaceutical Sciences, Nihon Pharmaceutical University, Saitama, Japan
5 Molecular Microbiology & Immunology, Biochemistry, School of Medicine and Bond Life Sciences Center, University of Missouri, Columbia, MO
6 Biostatistics and Data Management Section, National Cancer Institute, National Institutes of Health, Bethesda, MD
7 Departments of Hematology, Rheumatology, and Clinical Immunology & Infectious Disease, Kumamoto University Graduate School of Medical Sciences, Kumamoto, Japan
8 Department of Medical Technology, Kumamoto Health Science University, Kumamoto, Japan
9 Department of Experimental Pathology & Tumor Biology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
† Equally contributed in the present study.
*Address reprint requests to: Kenji Maeda, M.D., Ph.D., Center for Clinical Sciences, National Center for Global Health and Medicine, 1-21-1 Toyama, Shinjuku, Tokyo 162-8655, Japan. E-mail: [email protected]; fax: +81-3-3207-1038.
Potential conflicts of interest: S.K. and H.M. are among the coinventors on a patent for 4′-ethynyl-2-fluoro-2′-deoxyadenosine; all the rights, title, and interest to the patent have been assigned to Yamasa Corporation, Chiba, Japan. Dr. Tanaka is on the speakers’ bureau for and received grants from Bristol-Myers Squibb. He received grants from Chugai and MSD.
This work was supported, in part, by the Intramural Research Program of Center for Cancer Research, National Cancer Institute, National Institutes of Health (H.M.), in part by a Health and Labor Sciences Research Grant (Practical Research on Hepatitis [Research on the innovative development and the practical application of new drugs for hepatitis B [H.M., Ya.T., K.H.]), and in part by a Grant from International Research Center Aiming at the Control of AIDS, Kumamoto University (H.M.). S.G.S. was supported by R01AI112417 and R01AI076119.
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 inline image), whereas ETV failed to reduce inline image DNA even at 1 μM. Once-daily peroral administration of CAdA reduced inline image viremia (P = 0.0005) in human-liver-chimeric/ inline image–infected mice, whereas ETV completely failed to reduce inline image 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. Conclusion: 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. (Hepatology 2015)