AG-7404 is a potent protease inhibitor with anti-poliovirus activity. AG-7404 was active against all virus with EC50 values ranging from 0.080 to 0.674 uM. AG-7404 was fully active against V-073-resistant variants with EC50 values ranging from 0.218 to 0.819 uM, compared to values ranging from 0.202 to 0.407 uM for the V-073-susceptible parental strains.