Procaspase-activating compound 1 (PAC-1) directly activates procaspase-3 to caspase-3, a transformation that allows induction of apoptosis even in cells that have defective apoptotic machinery. In cancer cells, PAC-1 had an IC₅₀ value of 3 nM for induction of cell death, whereas in cells from adjacent normal tissue had IC₅₀ values of 3.2-8.5 µM.