HGS-1029

Inhibitor of Apoptosis (IAP) proteins block programmed cell death and are expressed at high levels in various human cancers, thus making them attractive targets for cancer drug development. Second mitochondrial activator of caspases (Smac) mimetics are small-molecule inhibitors that mimic Smac, an endogenous antagonist of IAP proteins. Preclinical studies have shown that Smac mimetics can directly trigger cancer cell death or, even more importantly, sensitize tumor cells for various cytotoxic therapies, including conventional chemotherapy, radiotherapy, or novel agents. Currently, several Smac mimetics are under evaluation in early clinical trials as monotherapy or in rational combinations (i.e., GDC-0917/CUDC-427, LCL161, AT-406/Debio1143, HGS1029, and TL32711/birinapant). This review discusses the promise as well as some challenges at the translational interface of exploiting Smac mimetics as cancer therapeutics. Clin Cancer Res; 21(22); 5030–6. ©2015 AACR.See all articles in this CCR Focus section, “Cell Death and Cancer Therapy.”

Inhibitor of apoptosis (IAP) proteins play a critical role in the control of survival and cell death by regulating key signaling events such as caspase activation and NF-κB signaling. Because aberrantly high expression of IAP proteins represents a frequent oncogenic event in human cancers, therapeutic targeting of IAP proteins is considered as a promising approach. Several small-molecule pharmacologic inhibitors of IAP proteins that mimic the binding domain of the endogenous IAP antagonist second mitochondrial activator of caspases (Smac) to IAP proteins have been developed over the past few years. IAP antagonists have been shown in various preclinical cancer models to either directly initiate cell death or, alternatively, to prime cancer cells for cytotoxic therapies by lowering the threshold for cell death induction. IAP antagonists (i.e., GDC-0917/CUDC-427, LCL161, AT-406, HGS1029, and TL32711) are currently under evaluation in early clinical trials alone or in combination regimens. Thus, the concept to therapeutically target IAP proteins in human cancer has in principle been successfully transferred into a clinical setting and warrants further evaluation as a treatment approach. Clin Cancer Res; 20(2); 289–95. ©2013 AACR.