APG350 induces superior clustering of TRAIL receptors and shows therapeutic antitumor efficacy independent of cross-linking via Fcγ receptors

Mol Cancer Ther. 2013 Dec;12(12):2735-47. doi: 10.1158/1535-7163.MCT-13-0323. Epub 2013 Oct 7.


Cancer cells can be specifically driven into apoptosis by activating Death-receptor-4 (DR4; TRAIL-R1) and/or Death-receptor-5 (DR5; TRAIL-R2). Albeit showing promising preclinical efficacy, first-generation protein therapeutics addressing this pathway, especially agonistic anti-DR4/DR5-monoclonal antibodies, have not been clinically successful to date. Due to their bivalent binding mode, effective apoptosis induction by agonistic TRAIL-R antibodies is achieved only upon additional events leading to antibody-multimer formation. The binding of these multimers to their target subsequently leads to effective receptor-clustering on cancer cells. The research results presented here report on a new class of TRAIL-receptor agonists overcoming this intrinsic limitation observed for antibodies in general. The main feature of these agonists is a TRAIL-mimic consisting of three TRAIL-protomer subsequences combined in one polypeptide chain, termed the single-chain TRAIL-receptor-binding domain (scTRAIL-RBD). In the active compounds, two scTRAIL-RBDs with three receptor binding sites each are brought molecularly in close proximity resulting in a fusion protein with a hexavalent binding mode. In the case of APG350-the prototype of this engineering concept-this is achieved by fusing the Fc-part of a human immunoglobulin G1 (IgG1)-mutein C-terminally to the scTRAIL-RBD polypeptide, thereby creating six receptor binding sites per drug molecule. In vitro, APG350 is a potent inducer of apoptosis on human tumor cell lines and primary tumor cells. In vivo, treatment of mice bearing Colo205-xenograft tumors with APG350 showed a dose-dependent antitumor efficacy. By dedicated muteins, we confirmed that the observed in vivo efficacy of the hexavalent scTRAIL-RBD fusion proteins is-in contrast to agonistic antibodies-independent of FcγR-based cross-linking events.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Monoclonal / pharmacology
  • Antibodies, Monoclonal, Humanized
  • Antineoplastic Agents / administration & dosage
  • Antineoplastic Agents / chemistry
  • Antineoplastic Agents / pharmacology*
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Disease Models, Animal
  • Dose-Response Relationship, Drug
  • Female
  • Humans
  • Mice
  • Models, Biological
  • Peptide Fragments / administration & dosage
  • Peptide Fragments / chemistry
  • Peptide Fragments / pharmacology*
  • Receptors, IgG / metabolism*
  • Receptors, TNF-Related Apoptosis-Inducing Ligand / agonists
  • Receptors, TNF-Related Apoptosis-Inducing Ligand / antagonists & inhibitors
  • Receptors, TNF-Related Apoptosis-Inducing Ligand / metabolism*
  • Recombinant Fusion Proteins / administration & dosage
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / pharmacology*
  • Xenograft Model Antitumor Assays


  • APG350
  • Antibodies, Monoclonal
  • Antibodies, Monoclonal, Humanized
  • Antineoplastic Agents
  • Peptide Fragments
  • Receptors, IgG
  • Receptors, TNF-Related Apoptosis-Inducing Ligand
  • Recombinant Fusion Proteins
  • drozitumab