Discovery of a Macrocyclic Influenza Cap-Dependent Endonuclease Inhibitor.

Influenza viruses (IFVs) have caused several pandemics and have claimed numerous lives since their first record in the early 20th century. While the outbreak of COVID-19 seemed to expel influenza from the sight of people for a short period of time, it is not surprising that it will recirculate around the globe after the coronavirus has mutated into a less fatal variant. Baloxavir marboxil ( 1 ), the prodrug of baloxavir ( 2 ) and a cap-dependent endonuclease (CEN) inhibitor, were approved by the FDA for the first treatment in almost 20 years. Despite their high antiviral potency, drug-resistant variants have been observed in clinical trials. Herein, we report a novel CEN inhibitor 8 with a delicately designed macrocyclic scaffold that exhibits a significantly smaller shift of inhibitory activity toward baloxavir-resistant variants.