Structure-based design and molecular profiling of Smac-mimetics selective for cellular IAPs

Area of Science:

• Biochemistry
• Molecular Biology
• Drug Discovery

Background:

• Inhibitor of Apoptosis Proteins (IAPs) are overexpressed in cancer and promote cell survival.
• Smac-mimetics (SMs) are developed to inhibit IAPs, showing promise in clinical trials.
• Different IAPs have distinct roles, necessitating targeted approaches.

Purpose of the Study:

• Design and characterize BIR3-selective Smac-mimetics targeting cIAP1.
• Focus SMs' antitumor activity on cIAPs degradation.
• Elucidate mechanisms and reduce adverse effects of pan-IAPs inhibitors.

Main Methods:

• BIR3-driven design of cIAP1-selective SMs.
• Crystal structure determination of cIAP1-BIR3 and XIAP-BIR3 complexes with SMs.
• Molecular displacement assays (fluorescence polarization) to measure binding affinity.
• In vitro cell-based assays to assess apoptosis induction and cIAP1 degradation.

Main Results:

• Developed SMs (SM130, SM114) with 23- and 32-fold higher affinity for cIAP1-BIR3 than XIAP-BIR3.
• Selective SMs induced apoptosis in cancer cells via caspases-independent cIAP1 degradation.
• Crystal structures revealed binding interactions within the BIR3 domains.

Conclusions:

• cIAP1-selective SMs offer a novel strategy for cancer therapy.
• Targeted degradation of cIAPs provides a focused antitumor mechanism.
• This approach may reduce side effects associated with non-selective IAP inhibitors.