CTSB and Alzheimer disease: It is noteworthy that other weak cathepsin inhibitors were also found to up-regulate active CatB including i) SD1002, a nonpeptidic PADK analogue previously shown to promote Aβ42 clearance and synaptic integrity in AD mice [39], ii) Cathepsin Inhibitor-1, a broad inhibitor of papain and cathepsins B, G, L, and S, and iii) E64d, a membrane-permeable inhibitor of several cysteine proteases that has been reported to inhibit CatB to reduce Aβ and improve memory in APP mice [42].