Inhibitor of apoptosis are a group of proteins that mainly act on the intrinsic pathway that block programmed cell death, which can oftentimes lead to cancer or other effects for the cell if mutated or improperly regulated. Many of these inhibitors act to block caspases, a family of cysteine proteases that play an integral role in apoptosis. Some of these inhibitors include the Bcl-2 family, viral inhibitor crmA, and IAP's.

IAP inhibitors are more effective for CD133+ stem-like medulloblastoma cells ¹⁾.