Antiviral effect of Favipiravir against Chandipura virus in vitro and in vivo

Abstract Chandipura virus (CHPV) is an emerging encephalitic virus with outbreak potential in a pediatric population. It causes acute encephalitis, with clinical symptoms leading to death within 48–72 h and an alarmingly high case fatality rate up to 55%–78%. Despite the high mortality rate in children, no vaccines or antivirals are currently available; thus, repurposing licensed drugs seems to be one of the attractive therapeutic approaches. Among the various options available, Favipiravir emerged as a promising candidate, and its unique characteristics and clinical efficacy have garnered significant attention and demonstrated considerable potential in the fight against viral diseases. In the current study, we have evaluated the antiviral effect of Favipiravir against CHPV by Plaque reduction assay and viral growth kinetics assay in Vero cells and in vivo effect of drug treatment against lethal viral challenge was analysed in 10‐day‐old CD1 mice. A dose‐dependent reduction in CHPV plaque size and number was observed in Vero cells treated with Favipiravir, with an EC 50 of 92.26 μM. Complete inhibition of CHPV replication was observed at 320 μM drug concentration and 50% cytotoxicity (CC 50 ) at 4774 μM, indicating a high selectivity index 51.24. In vivo, studies in mice showed 100% survival with 300 mg/kg/day of Favipiravir given orally till seventh‐day postinfection. The study provides evidence of the antiviral activity of Favipiravir against CHPV infection, and further clinical evaluation may alleviate the associated mortality.