Franck Amblard, Mahesh Kasthuri, Julia C. LeCher, Sijia Tao, Ramyani De, Rana Abdelnabi, Ingrid Marko, Longhu Zhou, Chengwei Li, Junxing Shi, Shu Ling Goh, Jessica Downs-Bowen, Leda Bassit, Selwyn J. Hurwitz, Keivan Zandi, Tamara R. McBrayer, Birgit Weynand, Kenneth A. Johnson, Johan Neyts, Raymond F. Schinazi
The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and COVID-19 epidemic is relatively under control due to the rapid development and deployment of vaccines and a few drugs. However, challenges persist, as new variants and issues with vaccine durability may compromise their effectiveness. Here, we report the discovery and evaluation of 1′-cyanocytidine (CNC), a nontoxic, next-generation nucleoside analog that displays submicromolar inhibition of SARS-CoV-2 replication in various cell and 3D HAE-ALI primary culture systems. Intracellularly, CNC is metabolized to its active 5′-triphosphate form (CNC-TP), targeting the viral RNA–dependent RNA polymerase. Pre–steady-state kinetic analysis revealed CNC-TP is a reversible, competitive inhibitor. The 5′-isobutyryl ester prodrug of CNC (CN iBu C), which rapidly converts to CNC in mouse and hamster plasma, substantially reduced viral RNA levels and lung infectious virus titers in a Syrian hamster model after intraperitoneal and oral dosing. With favorable pharmacokinetics, bioavailability, and safety profiles, CNC and CN iBu C represent promising candidates for SARS-CoV-2 therapy.