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Sidwell RW, Barnard DL. Respiratory syncytial virus infections: Recent prospects for control. Antiviral Res 2006; 71:379-90. [PMID: 16806515 DOI: 10.1016/j.antiviral.2006.05.014] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2006] [Revised: 05/18/2006] [Accepted: 05/22/2006] [Indexed: 10/24/2022]
Abstract
Respiratory syncytial virus (RSV) infections remain a significant public health problem throughout the world, although recently developed and clinically approved anti-RSV antibodies administered prophylactically to at-risk populations appear to have significantly affected the disease development. Much effort has been expended to develop effective anti-RSV therapies, using both in vitro assay systems and mouse, cotton rat, and primate models, with several products now in various stages of clinical study. Several products are also being considered for the treatment of clinical symptoms of RSV. In this review, updates on the status of the approved anti-RSV antibodies, ribavirin, and recent results of studies with potential new anti-RSV compounds are summarized and discussed.
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Affiliation(s)
- Robert W Sidwell
- Institute for Antiviral Research, Utah State University, 5600 Old Main Hill, Logan, UT 84322-5600, United States.
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52
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Yeung KS, Yamanaka GA, Meanwell NA. Severe acute respiratory syndrome coronavirus entry into host cells: Opportunities for therapeutic intervention. Med Res Rev 2006; 26:414-33. [PMID: 16521129 PMCID: PMC7168515 DOI: 10.1002/med.20055] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
A novel human coronavirus (CoV) has been identified as the etiological agent that caused the severe acute respiratory syndrome (SARS) outbreak in 2003. The spike (S) protein of this virus is a type I surface glycoprotein that mediates binding of the virus to the host receptor and the subsequent fusion between the viral and host membranes. Because of its critical role in viral entry, the S protein is an important target for the development of anti-SARS CoV therapeutics and prophylactics. This article reviews the structure and function of the SARS CoV S protein in the context of its role in virus entry. Topics that are discussed include: the interaction between the S1 domain of the SARS spike protein and the cellular receptor, angiotensin converting enzyme 2 (ACE2), and the structural features of the ectodomain of ACE2; the antigenic determinants presented by the S protein and the nature of neutralizing monoclonal antibodies that are elicited in vivo; the structure of the 4,3-hydrophobic heptad repeats HR1 and HR2 of the S2 domain and their interaction to form a six-helical bundle during the final stages of fusion. Opportunities for the design and development of anti-SARS agents based on the inhibition of receptor binding, the therapeutic uses of S-directed monoclonal antibodies and inhibitors of HR1-HR2 complex formation are presented.
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Affiliation(s)
- Kap-Sun Yeung
- Department of Chemistry, The Bristol-Myers Squibb Pharmaceutical Research Institute, 5 Research Parkway, P.O. Box 5100, Wallingford, Connecticut 06492, USA.
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53
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Filling the hole: evidence of a small molecule binding to the fusion core pocket in human respiratory syncytial virus. Expert Opin Investig Drugs 2006; 14:195-7. [PMID: 15757395 DOI: 10.1517/13543784.14.2.195] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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54
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Abstract
Respiratory syncytial virus (RSV) continues as an emerging infectious disease not only among infants and children, but also for the immune-suppressed, hospitalised and the elderly. To date, ribavirin (Virazole, ICN Pharmaceuticals, Inc.) remains the only therapeutic agent approved for the treatment of RSV. However, its clinical benefits are small and occur only in a fraction of RSV-infected patients. The prophylactic administration of palivizumab (Synagis, MedImmune, Inc.) is problematic and costly and, therefore, only recommended for use in high-risk infants. Clearly, the need for an effective and safe drug remains high. This review discusses several different antisense approaches and compares them with traditional strategies, such as RSV-targeting antibodies and antivirals, as well as developments in vaccine research.
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Affiliation(s)
- Hagen Cramer
- Ridgeway Biosystems, Inc., 9500 Euclid Avenue, ND-50, Cleveland, OH 44195, USA.
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55
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Yu KL, Wang XA, Civiello RL, Trehan AK, Pearce BC, Yin Z, Combrink KD, Gulgeze HB, Zhang Y, Kadow KF, Cianci CW, Clarke J, Genovesi EV, Medina I, Lamb L, Wyde PR, Krystal M, Meanwell NA. Respiratory syncytial virus fusion inhibitors. Part 3: Water-soluble benzimidazol-2-one derivatives with antiviral activity in vivo. Bioorg Med Chem Lett 2005; 16:1115-22. [PMID: 16368233 DOI: 10.1016/j.bmcl.2005.11.109] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2005] [Revised: 11/24/2005] [Accepted: 11/28/2005] [Indexed: 10/25/2022]
Abstract
The introduction of acidic and basic functionality into the side chains of respiratory syncytial virus (RSV) fusion inhibitors was examined in an effort to identify compounds suitable for evaluation in vivo in the cotton rat model of RSV infection following administration as a small particle aerosol. The acidic compounds 2r, 2u, 2v, 2w, 2z, and 2aj demonstrated potent antiviral activity in cell culture and exhibited efficacy in the cotton rat comparable to ribavirin. In a BALB/c mouse model, the oxadiazolone 2aj reduced virus titers following subcutaneous dosing, whilst the ester 2az and amide 2aab exhibited efficacy following oral administration. These results established the potential of this class of RSV fusion inhibitors to interfere with infection in vivo following topical or systemic administration.
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Affiliation(s)
- Kuo-Long Yu
- Department of Chemistry, The Bristol-Myers Squibb Pharmaceutical Research Institute, 5, Research Parkway, Wallingford, CT 06492, USA
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56
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Smee DF, Wandersee MK, Bailey KW, Hostetler KY, Holy A, Sidwell RW. Characterization and treatment of cidofovir-resistant vaccinia (WR strain) virus infections in cell culture and in mice. Antivir Chem Chemother 2005; 16:203-11. [PMID: 16004083 DOI: 10.1177/095632020501600306] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The wild-type (WT) vaccinia (WR strain) virus is highly virulent to mice by intranasal inoculation, yet death can be prevented by cidofovir treatment. A cidofovir-resistant (CDV-R) mutant of the virus was developed by 15 Vero cell culture passages in order to determine cross-resistance to other inhibitors, growth characteristics, virulence in infected mice, and suitability of the animal model for studying antiviral therapies. Comparisons were made to the original WT virus and to a WT virus passaged 15 times in culture (WTp15 virus). Cidofovir inhibited WT, WTp15, and CDV-R viruses by 50% at 61, 56 and 790 microM, respectively, in plaque reduction assays, with similar inhibition seen in virus yield studies. Cross-resistance occurred with compounds related to cidofovir, but not with unrelated nucleosides. The resistant virus produced 300-fold fewer infectious particles (PFU) than WT and WTp15 viruses in mouse C1271 cells, yet replicated similarly in Vero (monkey) cells. The CDV-R virus was completely attenuated for virulence at 10(7) PFU per mouse in normal BALB/c mice and in severe combined immunodeficient (SCID) mice. The WTp15 virus was 100-fold less virulent than WT virus in BALB/c mice. Thus, the lack of virulence of the resistant virus in the animal model is explained partly by its reduced ability to replicate in mouse cells and by attenuation occurring as a result of extensive cell culturing (inferred from what occurred with the WTp15 virus). Lung and snout virus titre reduction parameters were used to assess antiviral activity of compounds in BALB/c mice infected intranasally with the CDV-R virus. Cidofovir, HDP-cidofovir and arabinofuranosyladenine treatments reduced lung virus titres <fourfold, and snout virus titres > or = eight-fold. The animal model appears to have limited utility in drug efficacy testing.
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Affiliation(s)
- Donald F Smee
- Institute for Antiviral Research, Department of Animal, Dairy and Veterinary Sciences, Utah State University, Logan, UT, USA.
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57
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Bolken TC, Laquerre S, Zhang Y, Bailey TR, Pevear DC, Kickner SS, Sperzel LE, Jones KF, Warren TK, Amanda Lund S, Kirkwood-Watts DL, King DS, Shurtleff AC, Guttieri MC, Deng Y, Bleam M, Hruby DE. Identification and characterization of potent small molecule inhibitor of hemorrhagic fever New World arenaviruses. Antiviral Res 2005; 69:86-97. [PMID: 16343651 PMCID: PMC7114356 DOI: 10.1016/j.antiviral.2005.10.008] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2005] [Revised: 10/27/2005] [Accepted: 10/27/2005] [Indexed: 11/18/2022]
Abstract
Category A arenaviruses as defined by the National Institute of Allergy and Infectious Diseases (NIAID) are human pathogens that could be weaponized by bioterrorists. Many of these deadly viruses require biosafety level-4 (BSL-4) containment for all laboratory work, which limits traditional laboratory high-throughput screening (HTS) for identification of small molecule inhibitors. For those reasons, a related BSL-2 New World arenavirus, Tacaribe virus, 67-78% identical to Junín virus at the amino acid level, was used in a HTS campaign where approximately 400,000 small molecule compounds were screened in a Tacaribe virus-induced cytopathic effect (CPE) assay. Compounds identified in this screen showed antiviral activity and specificity against not only Tacaribe virus, but also the Category A New World arenaviruses (Junín, Machupo, and Guanarito). Drug resistant variants were isolated, suggesting that these compounds act through inhibition of a viral protein, the viral glycoprotein (GP2), and not through cellular toxicity mechanisms. A lead compound, ST-294, has been chosen for drug development. This potent and selective compound, with good bioavailability, demonstrated protective anti-viral efficacy in a Tacaribe mouse challenge model. This series of compounds represent a new class of inhibitors that may warrant further development for potential inclusion in a strategic stockpile.
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Affiliation(s)
- Tove C Bolken
- SIGA Technologies Inc., 4575 SW Research Way, Corvallis, OR 97333, USA
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Cianci C, Meanwell N, Krystal M. Antiviral activity and molecular mechanism of an orally active respiratory syncytial virus fusion inhibitor. J Antimicrob Chemother 2005; 55:289-92. [PMID: 15681582 DOI: 10.1093/jac/dkh558] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BMS-433771 is an orally bioavailable respiratory syncytial virus (RSV) inhibitor, functioning through inhibition of viral F protein-induced membrane fusion. The compound is active against both A and B groups of RSV, with an average EC(50) of 20 nM. BMS-433771 is also efficacious against RSV infection in two rodent models when dosed orally prior to infection. The compound possesses good pharmacokinetic properties, while maintaining a favourable toxicity profile. Consequently, BMS-433771 is well suited for further clinical evaluation in humans. Direct affinity labelling studies indicate that the compound binds in a hydrophobic cavity within the trimeric N-terminal heptad repeat. During the fusion process, this heptad repeat associates with a C-terminal heptad repeat to form a six helical coiled-coil bundle (or trimer-of-hairpins), and BMS-433771 presumably interferes with the functional association of these heptad repeats. The fusion protein of many other class 1 fusion viruses, such as HIV and influenza, form similar hairpin structures as a prelude to membrane fusion. The identification of BMS-433771 provides a proof of concept for small molecule inhibitors that target the formation of the six helical coiled-coil structure, which could be a prototype for the development of similar antivirals against other class 1 fusion viruses.
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Affiliation(s)
- Christopher Cianci
- Department of Virology, Bristol-Myers Squibb Pharmaceutical Research Institute, 5 Research Parkway, Wallingford, CT 06492, USA
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Cianci C, Langley DR, Dischino DD, Sun Y, Yu KL, Stanley A, Roach J, Li Z, Dalterio R, Colonno R, Meanwell NA, Krystal M. Targeting a binding pocket within the trimer-of-hairpins: small-molecule inhibition of viral fusion. Proc Natl Acad Sci U S A 2004; 101:15046-51. [PMID: 15469910 PMCID: PMC523459 DOI: 10.1073/pnas.0406696101] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2004] [Indexed: 11/18/2022] Open
Abstract
Trimeric class I virus fusion proteins undergo a series of conformational rearrangements that leads to the association of C- and N-terminal heptad repeat domains in a "trimer-of-hairpins" structure, facilitating the apposition of viral and cellular membranes during fusion. This final fusion hairpin structure is sustained by protein-protein interactions, associations thought initially to be refractory to small-molecule inhibition because of the large surface area involved. By using a photoaffinity analog of a potent respiratory syncytial virus fusion inhibitor, we directly probed the interaction of the inhibitor with its fusion protein target. Studies have shown that these inhibitors bind within a hydrophobic cavity formed on the surface of the N-terminal heptad-repeat trimer. In the fusogenic state, this pocket is occupied by key amino acid residues from the C-terminal heptad repeat that stabilize the trimer-of-hairpins structure. The results indicate that a low-molecular-weight fusion inhibitor can interfere with the formation or consolidation of key structures within the hairpin moiety that are essential for membrane fusion. Because analogous cavities are present in many class I viruses, including HIV, these results demonstrate the feasibility of this approach as a strategy for drug discovery.
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Affiliation(s)
- Christopher Cianci
- Bristol-Myers Squibb Pharmaceutical Research Institute, Wallingford, CT 06492, USA
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