CASP9 and cancer: Targeting the BIR2 and BIR3 domains of XIAP and other IAPs, there are several SMAC mimetics in clinical trials, including AT406 [56], TL32711 (birinapant) [57], LCL161 [58], AEG40826, CUDC427, and others [17] to release active CASP3 and CASP9 to kill cancers.