Z-IETD-FMK is widely used in biochemical and cellular research as a selective inhibitor of caspase-8, a key enzyme involved in apoptosis (programmed cell death). Its primary application is in studying the extrinsic apoptosis pathway, where caspase-8 plays a critical role. Researchers use this compound to block caspase-8 activity, allowing them to investigate its function and the downstream effects in various cell death processes. It is particularly useful in understanding the mechanisms of apoptosis in cancer cells, immune responses, and neurodegenerative diseases. Additionally, Z-IETD-FMK helps in distinguishing between caspase-dependent and caspase-independent cell death pathways, providing insights into therapeutic targets for diseases involving dysregulated apoptosis.