Caspase-9 is a cysteine protease that acts as an initiator in apoptosis and has been linked to mitochondrial cell death. Caspase-9 is activated by cytokine signaling of cell stress and is the first step in activation of caspase-3 and 7. Caspase-9 inhibitors are sought for their ability to affect downstream caspase processes. They have been shown to have neuroprotective effects and may be beneficial as anticancer agents. Both peptide and small molecule inhibitors exist for caspase-9. The fluoromethyl ketone (FMK) peptide Z-LEHD-FMK is a common irreversible inhibitor of caspase-9 with several other peptide and small molecule inhibitors currently available.