An inhibitor of caspase-6 (IC50 = 16.2 nM); selective for caspase-6 over caspase-7 (IC50 = 162.1 nM) but can also inhibit caspase-3 (IC50 = 13.6 nM); inhibits ricin-induced caspase-6-, but not caspase-3-, like activity in U937 cells at 100 μM; inhibits caspase-6-like activity in Norway spruce cell extracts at 2 μM, as well as in staurosporine-treated SKNAS neuroblastoma cells (IC50 = 0.49 μM)