The proteolytic activity of caspase-3 can be inhibited by X-linked inhibitor of apoptosis (XIAP) and a novel class of drugs called second mitochondria-derived activator of caspase (SMAC)-mimetics directly bind and antagonize XIAP, sensitizing CLL cells to TRAIL [51, 52]. The gene discussed is XIAP; the disease is B-cell chronic lymphocytic leukemia.