title: An orally bioavailable antipoxvirus compound (ST-246) inhibits extracellular virus formation and protects mice from lethal orthopoxvirus Challenge.
abstract: ST-246 is a low-molecular-weight compound (molecular weight = 376), that is potent (concentration that inhibited virus replication by 50% = 0.010 microM), selective (concentration of compound that inhibited cell viability by 50% = >40 microM), and active against multiple orthopoxviruses, including vaccinia, monkeypox, camelpox, cowpox, ectromelia (mousepox), and variola viruses. Cowpox virus variants selected in cell culture for resistance to ST-246 were found to have a single amino acid change in the V061 gene. Reengineering this change back into the wild-type cowpox virus genome conferred resistance to ST-246, suggesting that V061 is the target of ST-246 antiviral activity. The cowpox virus V061 gene is homologous to vaccinia virus F13L, which encodes a major envelope protein (p37) required for production of extracellular virus. In cell culture, ST-246 inhibited plaque formation and virus-induced cytopathic effects. In single-cycle growth assays, ST-246 reduced extracellular virus formation by 10 fold relative to untreated controls, while having little effect on the production of intracellular virus. In vivo oral administration of ST-246 protected BALB/c mice from lethal infection, following intranasal inoculation with 10x 50% lethal dose (LD(50)) of vaccinia virus strain IHD-J. ST-246-treated mice that survived infection acquired protective immunity and were resistant to subsequent challenge with a lethal dose (10x LD(50)) of vaccinia virus. Orally administered ST-246 also protected A/NCr mice from lethal infection, following intranasal inoculation with 40,000x LD(50) of ectromelia virus. Infectious virus titers at day 8 postinfection in liver, spleen, and lung from ST-246-treated animals were below the limits of detection (<10 PFU/ml). In contrast, mean virus titers in liver, spleen, and lung tissues from placebo-treated mice were 6.2 x 10(7), 5.2 x 10(7), and 1.8 x 10(5) PFU/ml, respectively. Finally, oral administration of ST-246 inhibited vaccinia virus-induced tail lesions in Naval Medical Research Institute mice inoculated via the tail vein. Taken together, these results validate F13L as an antiviral target and demonstrate that an inhibitor of extracellular virus formation can protect mice from orthopoxvirus-induced disease.
authors.affiliation: ViroPharma, Inc., Exton, Pennsylvania, USA.
authors.forename: Guang
authors.initials: G
authors.lastname: Yang
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Pevear
authors.forename: Marc H
authors.initials: MH
authors.lastname: Davies
authors.forename: Marc S
authors.initials: MS
authors.lastname: Collett
authors.forename: Tom
authors.initials: T
authors.lastname: Bailey
authors.forename: Susan
authors.initials: S
authors.lastname: Rippen
authors.forename: Linda
authors.initials: L
authors.lastname: Barone
authors.forename: Chris
authors.initials: C
authors.lastname: Burns
authors.forename: Gerry
authors.initials: G
authors.lastname: Rhodes
authors.forename: Sanjeev
authors.initials: S
authors.lastname: Tohan
authors.forename: John W
authors.initials: JW
authors.lastname: Huggins
authors.forename: Robert O
authors.initials: RO
authors.lastname: Baker
authors.forename: R L Mark
authors.initials: RL
authors.lastname: Buller
authors.forename: Erin
authors.initials: E
authors.lastname: Touchette
authors.forename: Kem
authors.initials: K
authors.lastname: Waller
authors.forename: Jill
authors.initials: J
authors.lastname: Schriewer
authors.forename: Johan
authors.initials: J
authors.lastname: Neyts
authors.forename: Erik
authors.initials: E
authors.lastname: DeClercq
authors.forename: Kevin
authors.initials: K
authors.lastname: Jones
authors.forename: Dennis
authors.initials: D
authors.lastname: Hruby
authors.forename: Robert
authors.initials: R
authors.lastname: Jordan
mesh_terms: D000284:Administration, Oral; D000595:Amino Acid Sequence; D000818:Animals; D000998:Antiviral Agents / Q000009:adverse effects / Q000737:chemistry / Q000494:pharmacology*; D001549:Benzamides / Q000009:adverse effects / Q000737:chemistry / Q000494:pharmacology*; D003588:Cytopathogenic Effect, Viral / Q000187:drug effects; D004353:Drug Evaluation, Preclinical; D004481:Ectromelia virus / Q000302:isolation & purification; D004482:Ectromelia, Infectious / Q000517:prevention & control; D005260:Female; D007211:Indoles / Q000009:adverse effects / Q000737:chemistry / Q000494:pharmacology*; D054833:Isoindoles; D008099:Liver / Q000821:virology; D008168:Lung / Q000821:virology; D008565:Membrane Proteins / Q000187:drug effects / Q000235:genetics; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D008970:Molecular Weight; D018155:Orthopoxvirus / Q000187:drug effects* / Q000302:isolation & purification / Q000502:physiology; D011213:Poxviridae Infections / Q000517:prevention & control* / Q000821:virology; D016415:Sequence Alignment; D013154:Spleen / Q000821:virology; D014615:Vaccinia / Q000517:prevention & control; D014759:Viral Envelope Proteins / Q000187:drug effects / Q000235:genetics; D010948:Viral Plaque Assay; D019065:Virus Assembly / Q000187:drug effects; D010797:Phthalimides
chemical_list: D000998:Antiviral Agents; D001549:Benzamides; D007211:Indoles; D054833:Isoindoles; D008565:Membrane Proteins; D014759:Viral Envelope Proteins; C084759:p37 protein, Vaccinia virus; C505045:tecovirimat; D010797:Phthalimides