Screening a Small Compound Array Identifies Methotrexate, Raltitrexed, Homoharringtonine and Idarubicin as Compounds with Anti-Orthopoxvirus Efficacy

Valerie Cadet, Philadelphia College of Osteopathic Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA USA
Frank Michel, College of Veterinary Medicine, University of Georgia, Athens, GA USA
Xiudan Gao, College of Veterinary Medicine, University of Georgia, Athens, GA USA
Robert J. Hogan, College of Veterinary Medicine, University of Georgia, Athens, GA USA ,

Description

BACKGROUND: Poxvirus zoonoses have been well documented in recent years. Cowpox infected cats, rodents and cattle, in close contact with humans, have been reported to transmit the virus through open wounds, large respiratory droplets and fomites. The emerging infectious pathogen monkeypox has been noted to undergo serial human transmission. Vaccinia virus has been shown time and again to be transmissible through direct physical and indirect contact from recent vaccinees to unvaccinated individuals. Typically, disease course is mild and self-limiting; however severe generalized infections have been described in patients with atopy or immunosuppression. With the waning of specific immunity in the general population combined with the severity of complications occurring post orthopoxvirus infections in the immunocompromised, the need for continued research and development of therapies has been underscored.

METHODS: To address the deficiency of FDA-approved poxvirus treatments, a small molecule library was screened for the purpose of illuminating compounds which inhibit poxvirus multiplication. Two independent screens of n=446 compounds were carried out in Vero E6 cells using cowpox as the representative poxvirus. Compounds identified in the primary screen were rescreened in a dose-dependent manner and four hits identified. Subsequent validation in type II pneumocytes was carried out and methotrexate chosen for in vivo analysis to assess protection against an intranasal cowpox infection in BALB/c mice.

RESULTS: We have identified four compounds, each currently in use as chemotherapeutics and/ or immunosuppressives, which protect against viral multiplication in vitro at concentrations as low as 0.04 micromolar: methotrexate, idarubicin, homoharringtonine and raltitrexed. Methotrexate proved effective at prolonging mice survival as well as limiting viral multiplication in the lungs.

CONCLUSIONS: These results identify methotrexate as a compound with anti-poxvirus capability from which derivatives can be studied for potential administration to protect against human orthopoxvirus infections. They also highlight several other potential compounds which can be further explored for in vivo protective efficacy in future studies.

 
May 7th, 1:00 PM

Screening a Small Compound Array Identifies Methotrexate, Raltitrexed, Homoharringtonine and Idarubicin as Compounds with Anti-Orthopoxvirus Efficacy

Georgia Campus

BACKGROUND: Poxvirus zoonoses have been well documented in recent years. Cowpox infected cats, rodents and cattle, in close contact with humans, have been reported to transmit the virus through open wounds, large respiratory droplets and fomites. The emerging infectious pathogen monkeypox has been noted to undergo serial human transmission. Vaccinia virus has been shown time and again to be transmissible through direct physical and indirect contact from recent vaccinees to unvaccinated individuals. Typically, disease course is mild and self-limiting; however severe generalized infections have been described in patients with atopy or immunosuppression. With the waning of specific immunity in the general population combined with the severity of complications occurring post orthopoxvirus infections in the immunocompromised, the need for continued research and development of therapies has been underscored.

METHODS: To address the deficiency of FDA-approved poxvirus treatments, a small molecule library was screened for the purpose of illuminating compounds which inhibit poxvirus multiplication. Two independent screens of n=446 compounds were carried out in Vero E6 cells using cowpox as the representative poxvirus. Compounds identified in the primary screen were rescreened in a dose-dependent manner and four hits identified. Subsequent validation in type II pneumocytes was carried out and methotrexate chosen for in vivo analysis to assess protection against an intranasal cowpox infection in BALB/c mice.

RESULTS: We have identified four compounds, each currently in use as chemotherapeutics and/ or immunosuppressives, which protect against viral multiplication in vitro at concentrations as low as 0.04 micromolar: methotrexate, idarubicin, homoharringtonine and raltitrexed. Methotrexate proved effective at prolonging mice survival as well as limiting viral multiplication in the lungs.

CONCLUSIONS: These results identify methotrexate as a compound with anti-poxvirus capability from which derivatives can be studied for potential administration to protect against human orthopoxvirus infections. They also highlight several other potential compounds which can be further explored for in vivo protective efficacy in future studies.