Second mitochondria-derived activator of caspase (SMAC) mimetics are a class of cell death-inducing agents that target the inhibitor of apoptosis (IAP) family members, such as cIAP1, cIAP2, and X-linked inhibitor of apoptosis (XIAP), for proteasomal degradation, and have been evaluated for their anti-cancer efficacy in clinical trials as single agents or in combination with various therapeutics, including TRAIL therapeutics [17]. The gene discussed is XIAP; the disease is cancer.