Tight-binding, reversible, highly selective inhibitor of acid proteases (aspartyl peptidases), like pepsin, gastricsin, cathepsin E and D, renin, chymosin, bacterial aspartic proteinases and HIV proteases. Does not inhibit thiol proteases, neutral proteases or serine proteases. Widely used as a research tool in studies of protease mechanisms and biological functions. Solubilized gamma-secretase and retroviral protease inhibitor. Shows antibacterial, antifungal and antiparasitic activity. Suppresses p53-dependent apoptosis in lymphoid cells as well as TNFalpha-induced apoptosis in U937 cells. Inhibits degradation of autophagic cargo inside autophagolysosomes.