Birinapant, a smac-mimetic with improved tolerability for the treatment of solid tumors and hematological malignancies

J Med Chem. 2014 May 8;57(9):3666-77. doi: 10.1021/jm500176w. Epub 2014 Apr 15.


Birinapant (1) is a second-generation bivalent antagonist of IAP proteins that is currently undergoing clinical development for the treatment of cancer. Using a range of assays that evaluated cIAP1 stability and oligomeric state, we demonstrated that 1 stabilized the cIAP1-BUCR (BIR3-UBA-CARD-RING) dimer and promoted autoubiquitylation of cIAP1 in vitro. Smac-mimetic 1-induced loss of cIAPs correlated with inhibition of TNF-mediated NF-κB activation, caspase activation, and tumor cell killing. Many first-generation Smac-mimetics such as compound A (2) were poorly tolerated. Notably, animals that lack functional cIAP1, cIAP2, and XIAP are not viable, and 2 mimicked features of triple IAP knockout cells in vitro. The improved tolerability of 1 was associated with (i) decreased potency against cIAP2 and affinity for XIAP BIR3 and (ii) decreased ability to inhibit XIAP-dependent signaling pathways. The P2' position of 1 was critical to this differential activity, and this improved tolerability has allowed 1 to proceed into clinical studies.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antineoplastic Agents / pharmacology*
  • Antineoplastic Agents / therapeutic use
  • Apoptosis Regulatory Proteins
  • Carrier Proteins / chemistry*
  • Dipeptides / pharmacology*
  • Dipeptides / therapeutic use
  • Drug Discovery
  • Hematologic Neoplasms / drug therapy*
  • Indoles / pharmacology*
  • Indoles / therapeutic use
  • Mice
  • Mitochondrial Proteins / chemistry*
  • Models, Molecular
  • Molecular Mimicry*
  • Neoplasms, Experimental / drug therapy*


  • Antineoplastic Agents
  • Apoptosis Regulatory Proteins
  • Carrier Proteins
  • Diablo protein, mouse
  • Dipeptides
  • Indoles
  • Mitochondrial Proteins
  • birinapant

Associated data

  • PDB/4KMN
  • PDB/4KMP