Targeting Chikungunya Virus Replication by Benzoannulene Inhibitors

Abstract

A benzo[6]annulene, 4-(<i>tert</i>-butyl)-<i>N</i>-(3-methoxy-5,6,7,8-tetrahydronaphthalen-2-yl) benzamide (<b>1a</b>), was identified as an inhibitor against Chikungunya virus (CHIKV) with antiviral activity EC₉₀ = 1.45 μM and viral titer reduction (VTR) of 2.5 log at 10 μM with no observed cytotoxicity (CC₅₀ = 169 μM) in normal human dermal fibroblast cells. Chemistry efforts to improve potency, efficacy, and drug-like properties of <b>1a</b> resulted in a novel lead compound <b>8q</b>, which possessed excellent cellular antiviral activity (EC₉₀ = 270 nM and VTR of 4.5 log at 10 μM) and improved liver microsomal stability. CHIKV resistance to an analog of <b>1a</b>, compound <b>1c</b>, tracked to a mutation in the nsP3 macrodomain. Further mechanism of action studies showed compounds working through inhibition of human dihydroorotate dehydrogenase in addition to CHIKV nsP3 macrodomain. Moderate efficacy was observed in an <i>in vivo</i> CHIKV challenge mouse model for compound <b>8q</b> as viral replication was rescued from the pyrimidine salvage pathway.