Oral administration of cyclopentane neuraminidase inhibitors protects ferrets against influenza virus infection

Abstract

Several cyclopentane inhibitors of influenza virus neuraminidase that have inhibitory activities in tissue culture similar to those of zanamivir and oseltamivir have recently been described. These new inhibitors have been examined for efficacy against a virulent H3N2 influenza virus when administered orally to infected ferrets. Preliminary studies indicated that oral administration of BCX-1923, BCX-1827, or BCX-1812 (RWJ-270201) at a dose of 5 or 25 mg/kg of body weight was active in ferrets in reducing respiratory and constitutional signs and symptoms, but these antivirals affected virus titers in the upper and lower respiratory tracts only marginally. Of the three compounds, BCX-1812 seemed to be the most efficacious and was examined further at higher doses of 30 and 100 mg/kg. These doses significantly reduced peak virus titers in nasal washes and total virus shedding as measured by areas under the curve. Virus titers in lung homogenates were also reduced compared to those in controls, but the difference was not statistically significant. As was observed with BCX-1812 at lower doses, the nasal inflammatory cellular response, fever, and nasal signs were reduced while ferret activity was not, with activity remaining similar to uninfected animals.

FIG. 1.

Chemical structures of various neuraminidase inhibitors.

FIG. 2.

Effect of oral administration of compounds on nasal virus titers, nasal inflammatory cell counts, and fever of ferrets infected with influenza virus A (H3N2) virus. Nasal virus titers (A), total numbers of inflammatory cells in nasal washes (B), and changes in temperature relative to baseline temperatures (C) were monitored in ferrets at the indicated times after infection. Ferrets were left untreated (▪) or were treated twice daily with oral 5-mg/kg doses of GS4104 (⧫) or BCX-1827 (▴) for 3 days beginning 2 h prior to infection with influenza virus clone 7a. Values are means ± standard errors of the means (error bars) for three to four animals.

FIG. 3.

Effect of oral administration of compounds on total virus titers in lung. (A) Ferrets were treated orally with 5-mg/kg doses of GS4014 (bar 1) or BCX-1827 (bar 2) or were untreated (bar 3). (B) Ferrets were treated orally with 25-mg/kg doses of BCX-1827 (bar 1), BCX-1823 (bar 2), or BCX-1812 (bar 3) or were untreated (bar 4). (C) Ferrets were treated orally with BCX-1812 at 10 mg/kg (bar 1), BCX-1812 at 30 mg/kg (bar 2), or BCX-1812 at 100 mg/kg (bar 3) or were untreated (bar 4). All treated animals were given compound for 3 days beginning 2 h prior to infection with influenza virus clone 7a. Values are means + standard errors of the means (error bars) for three to four animals.

FIG. 4.

Effect of oral administration of compounds on nasal virus titers, nasal inflammatory cell counts, and fever of ferrets infected with influenza virus A (H3N2). Nasal virus titers (A), total numbers of inflammatory cells in nasal washes (B), and changes in temperature relative to baseline temperatures (C) were monitored in ferrets at the indicated times after infection. Ferrets were left untreated (▪) or were treated twice daily with 25-mg/kg oral doses of BCX-1827 (⧫), BCX-1823 (▴), or BCX-1812 (•) for 3 days beginning 2 h prior to infection with influenza virus clone 7a. Values are means ± standard errors of the means (error bars) for three to four animals.

FIG. 5.

Effect of oral administration of compounds on nasal virus titers, nasal inflammatory cell counts, and fever of ferrets infected with influenza virus A (H3N2). Nasal virus titers (A), total numbers of inflammatory cells in nasal washes (B), and changes in temperature relative to baseline temperatures (C) were monitored in ferrets at the indicated times after infection. Ferrets were left untreated (▪) or were treated twice daily with oral doses of BCX-1812 at 10 mg/kg (⧫), 30 mg/kg (▴), or 100 mg/kg (•) for 3 days beginning 2 h prior to infection with influenza virus clone 7a. Values are means ± standard errors of the means (error bars) for three to four animals.

FIG. 6.

Profiles of mean (n = 3) concentration of BCX-1812 plasma in male ferrets following single oral and i.v. administration of BCX-1812 (10 mg/kg).