Chemical. CAS 88321-09-9. Formula C17H30N2O5. MW 342.4. Aloxistatin is a cell permeable irreversible inhibitor of lysosomal and cytosolic cysteine proteases cathepsin B an L, calpain 1/2, papain and has diverse biological activities. It is an ethyl ester form of E-64c that inhibits calpain and the cysteine proteases cathepsins F, K, B, H, and L.