Inhibitor of apoptosis protein (IAP) (IAP)

Inhibitor of apoptosis proteins (IAPs) are a family of evolutionarily conserved proteins that serve as key endogenous regulators of programmed cell death and various signaling pathways (UniProt P98170, Q13490). The family includes members such as X-linked inhibitor of apoptosis protein (XIAP), cellular IAP 1 (cIAP1), and cellular IAP 2 (cIAP2), which are characterized by the presence of Baculoviral IAP Repeat (BIR) domains. XIAP is the only family member that directly inhibits caspases, specifically caspase-3, -7, and -9, while cIAP1 and cIAP2 primarily regulate signal transduction, particularly the NF-kappaB pathway, through their E3 ubiquitin ligase activity (PMID: 28211506). In many cancers, IAPs are overexpressed, contributing to tumor cell survival, resistance to chemotherapy, and evasion of immune surveillance. Therapeutic strategies targeting IAPs often utilize Smac mimetics, small molecules that mimic the endogenous IAP antagonist Smac/DIABLO (PMID: 24591105). These drugs, such as Xevinapant, promote the degradation of cIAPs and neutralize XIAP, thereby sensitizing tumor cells to apoptosis-inducing stimuli like TNF-alpha or TRAIL (NCT02022098). Clinical development of these agents has focused on combination therapies to overcome resistance in solid tumors and hematological malignancies. Notable safety considerations include the potential for cytokine release syndrome due to systemic TNF-alpha induction.

Other names

Baculoviral IAP repeat-containing proteinBIRCX-linked inhibitor of apoptosis protein (XIAP)Cellular inhibitor of apoptosis protein 1 (cIAP1)Cellular inhibitor of apoptosis protein 2 (cIAP2)BIRC4BIRC2BIRC3Survivin (BIRC5)Livin (BIRC7)

IAP antagonists (Smac mimetics) bind to BIR domains, inducing autoubiquitination and degradation of cIAP1/2 and preventing XIAP from inhibiting caspases 3, 7, and 9 (PMID: 24591105).