Design, synthesis, and biological activity of a potent Smac mimetic that sensitizes cancer cells to apoptosis by antagonizing IAPs

ACS Chem Biol. 2006 Sep 19;1(8):525-33. doi: 10.1021/cb600276q.


Designed second mitochondrial activator of caspases (Smac) mimetics based on an accessible [7,5]-bicyclic scaffold bind to and antagonize protein interactions involving the inhibitor of apoptosis (IAP) proteins, X-chromosome-linked IAP (XIAP), melanoma IAP (ML-IAP), and c-IAPs 1 and 2 (cIAP1 and cIAP2). The design rationale is based on a combination of phage-panning data, peptide binding studies, and a survey of potential isosteres. The synthesis of two scaffolds is described. These compounds bind the XIAP-baculoviral IAP repeat 3 (BIR3), cIAP1-BIR3, cIAP2-BIR3, and ML-IAP-BIR domains with submicromolar affinities. The most potent Smac mimetic binds the cIAP1-BIR3 and ML-IAP-BIR domains with a K i of 50 nM. The X-ray crystal structure of this compound bound to an ML-IAP/XIAP chimeric BIR domain protein is compared with that of a complex with a phage-derived tetrapeptide, AVPW. The structures show that these compounds bind to the Smac-binding site on ML-IAP with identical hydrogen-bonding patterns and similar hydrophobic interactions. Consistent with the structural data, coimmunoprecipitation experiments demonstrate that the compounds can effectively block Smac interactions with ML-IAP. The compounds are further demonstrated to activate caspase-3 and -7, to reduce cell viability in assays using MDA-MB-231 breast cancer cells and A2058 melanoma cells, and to enhance doxorubicin-induced apoptosis in MDA-MB-231 cells.

MeSH terms

  • Apoptosis / drug effects*
  • Binding Sites
  • Biomimetic Materials / chemical synthesis
  • Biomimetic Materials / chemistry
  • Biomimetic Materials / pharmacology*
  • Caspases / metabolism
  • Cell Line
  • Crystallography, X-Ray
  • Drug Design*
  • Enzyme Activation / drug effects
  • Humans
  • Inhibitor of Apoptosis Proteins / antagonists & inhibitors*
  • Inhibitor of Apoptosis Proteins / metabolism
  • Intracellular Signaling Peptides and Proteins / chemistry*
  • Intracellular Signaling Peptides and Proteins / metabolism
  • Models, Molecular
  • Neoplasms / genetics
  • Neoplasms / metabolism*
  • Neoplasms / pathology*
  • Protein Binding
  • Protein Structure, Tertiary


  • Inhibitor of Apoptosis Proteins
  • Intracellular Signaling Peptides and Proteins
  • Caspases

Associated data

  • PDB/2I3H
  • PDB/2I3I