EIDD-1931 (NHC) is an active metabolite of EIDD-2801, a promising COVID-19 inhibitor. EIDD-1931 (NHC) has broad spectrum antiviral activity against SARS-CoV-2, MERS-CoV, SARS-CoV, and related zoonotic group 2b or 2c Bat-CoVs with average IC50 of 0.15 μM, as well as increased potency against a coronavirus bearing resistance mutations to the nucleoside analog inhibitor remdesivir.