A cell-permeable inhibitor of calpain 1 (Ki = 120 nM) and calpain 2 (Ki = 230 nM). Also potently inhibits cathepsin B (Ki = 100 nM), and cathepsin L (Ki = 0.6 nM). Shown to induce caspase-dependent apoptosis in human acute lymphoblastic leukemia and non-Hodgkin’s Lymphoma cells.