Exposure to hepatitis E virus (HEV) bears a high risk of developing
chronic infection in immunocompromised patients, including organ transplant recipients and
cancer patients. We aim to identify effective anti-HEV
therapies through screening and repurposing safe-in-human broad-spectrum
antiviral agents. In this study, a safe-in-human broad-spectrum
antiviral drug library comprising of 94 agents was used. Upon screening, we identified
gemcitabine, a widely used anti-
cancer drug, as a potent inhibitor of HEV replication. The
antiviral effect was confirmed in a range of cell culture models with genotype 1 and 3 HEV strains. As a
cytidine analog, exogenous supplementation of
pyrimidine nucleosides effectively reversed the
antiviral activity of
gemcitabine, but the level of
pyrimidine nucleosides per se does not affect HEV replication. Surprisingly, similar to
interferon-alpha (IFNα) treatment,
gemcitabine activates STAT1 phosphorylation. This subsequently triggers activation of
interferon-sensitive response element (ISRE) and transcription of
interferon-stimulated genes (ISGs).
Cytidine or
uridine effectively inhibits
gemcitabine-induced activation of ISRE and ISGs. As expected,
JAK inhibitor 1 blocked IFNα, but not
gemcitabine-induced STAT1 phosphorylation, ISRE/ISG activation, and anti-HEV activity. These effects of
gemcitabine were completely lost in STAT1 knockout cells. In summary,
gemcitabine potently inhibits HEV replication by triggering
interferon-like response through STAT1 phosphorylation but independent of
Janus kinases. This represents a non-canonical
antiviral mechanism, which utilizes the innate defense machinery that is distinct from the classical
interferon response. These results support repurposing
gemcitabine for treating
hepatitis E, especially for HEV-infected
cancer patients, leading to dual anti-
cancer and
antiviral effects.