Fragment-Based Drug Discovery Targeting Inhibitor of Apoptosis Proteins: Discovery of a Non-Alanine Lead Series with Dual Activity Against cIAP1 and XIAP

J Med Chem. 2015 Aug 27;58(16):6574-88. doi: 10.1021/acs.jmedchem.5b00706. Epub 2015 Aug 7.


Inhibitor of apoptosis proteins (IAPs) are important regulators of apoptosis and pro-survival signaling pathways whose deregulation is often associated with tumor genesis and tumor growth. IAPs have been proposed as targets for anticancer therapy, and a number of peptidomimetic IAP antagonists have entered clinical trials. Using our fragment-based screening approach, we identified nonpeptidic fragments binding with millimolar affinities to both cellular inhibitor of apoptosis protein 1 (cIAP1) and X-linked inhibitor of apoptosis protein (XIAP). Structure-based hit optimization together with an analysis of protein-ligand electrostatic potential complementarity allowed us to significantly increase binding affinity of the starting hits. Subsequent optimization gave a potent nonalanine IAP antagonist structurally distinct from all IAP antagonists previously reported. The lead compound had activity in cell-based assays and in a mouse xenograft efficacy model and represents a highly promising start point for further optimization.

MeSH terms

  • Animals
  • Antineoplastic Agents / chemical synthesis
  • Antineoplastic Agents / pharmacokinetics
  • Antineoplastic Agents / pharmacology*
  • Cell Proliferation / drug effects
  • Computational Biology
  • Drug Design
  • Drug Discovery
  • High-Throughput Screening Assays
  • Humans
  • Inhibitor of Apoptosis Proteins / antagonists & inhibitors*
  • Inhibitor of Apoptosis Proteins / drug effects*
  • Mice
  • Mice, Inbred BALB C
  • Models, Molecular
  • Peptide Fragments / chemical synthesis
  • Peptide Fragments / pharmacokinetics
  • Peptide Fragments / pharmacology*
  • Piperazines / chemical synthesis
  • Piperazines / pharmacology
  • X-Linked Inhibitor of Apoptosis Protein / antagonists & inhibitors*
  • Xenograft Model Antitumor Assays


  • Antineoplastic Agents
  • Inhibitor of Apoptosis Proteins
  • Peptide Fragments
  • Piperazines
  • X-Linked Inhibitor of Apoptosis Protein

Associated data

  • PDB/5C0K
  • PDB/5C0L
  • PDB/5C3H
  • PDB/5C3K
  • PDB/5C7A
  • PDB/5C7B
  • PDB/5C7C
  • PDB/5C7D
  • PDB/5C83
  • PDB/5C84