Discovery of Potent and Efficacious Influenza PB2 Inhibitors

In pursuit of potent, efficacious influenza inhibitors with novel mechanisms, we replaced the 7-azaindole core of the PB2 inhibitor pimodivir (VX-787/JNJ872) with a 7-fluoro-substituted indazole to mitigate CYP3A- and aldehyde oxidase-mediated metabolism by lowering lipophilicity and blocking the metabolic soft spot. We further introduced a cyclopropyl-fused ring onto the bridged bicyclo[2.2.2]-octane to retain potency while reducing glucuronidation. This design converged in compound <b>3</b>, where the indazole scaffold and fused cyclopropyl ring acted synergistically to improve the potency and pharmacokinetic properties. In a lethal influenza mouse challenge model, compound <b>3</b> achieved approximately a 7-fold reduction in the effective dose compared with pimodivir. It also showed significantly improved activity against selected influenza A strains versus pimodivir, highlighting its potential as a differentiated PB2 inhibitor.