K777 is a potent, orally active and irreversible cysteine protease inhibitor. K777 is also a potent CYP3A4 inhibitor with an IC50 of 60 nM and a selective CCR4 antagonist featuring the potent chemotaxis inhibition. K777 irreversibly inhibits Cruzain, the major cysteine protease of Trypansoma cruzi, and cathepsins B and L. K777 is a broad-spectrum antiviral by targeting cathepsin-mediated cell entry. K777 inhibits SARS-CoV and EBOV pseudovirus entry with IC50 values of 0.68 nM and 0.87 nM, respectively.
