BACKGROUND & AIMS: Hepatitis E virus (HEV) constitutes a substantial public health burden with ∼20 million human infections annually, including 3.3 million symptomatic cases. Appropriate treatment options for, in particular, HEV-infected immunocompromised patients and pregnant women are lacking, underscoring the urgent need for potent and safe antiviral drugs. METHODS: HEV subgenomic replicon systems were used to screen a small library of preselected nucleoside analogues, originally developed in a hepatitis C virus (HCV) antiviral program. Antiviral activity of the selected hit on HEV infection was evaluated in a variety of cell culture systems, and the efficacy of the compound was assessed in the athymic nude rat HEV infection model. RESULTS: Compound JNJ-9117 exerts pangenotype antiviral activity against HEV in different cell types as well as in primary human hepatocytes. A high level of conservation is observed between 3 crucial motifs in the catalytic domain of the HCV and HEV polymerases. This suggests a mechanism of action that is identical to that of the molecule against HCV, whereby the 5'-triphosphate of JNJ-9117 acts as a chain terminator during viral RNA synthesis. JNJ-9117 has a favorable pharmacokinetic and safety profile in rats and results in a pronounced antiviral effect in a chronic rat HEV infection model, both in a prophylactic and therapeutic setting. The combination of JNJ-9117 and ribavirin (each at an intentionally selected suboptimal/inactive dose) was highly effective in infected rats in lowering the viral RNA load in liver and feces to (almost) undetectable levels. CONCLUSIONS: JNJ-9117 has a profile that holds promise for the treatment of life-threatening HEV infections in humans. Phase I studies with JNJ-9117 have been initiated in healthy human volunteers.