A potent, cell-permeable, and selective inhibitor of calpain and cathepsin B (Ki values are 10 and 25 nM respectively). MDL 28170 does not inhibit trypsin-like serine proteases. Rapidly penetrates the blood-brain barrier following systemic administration and displays neuroprotective effects in vivo. Modulates the formation of Aβ formation by inhibiting the formation of intermediate Aβ46 and protecting Aβ from degradation.