1. APG350 induces superior clustering of TRAIL receptors and shows therapeutic antitumor efficacy independent of cross-linking via Fcγ receptors.
- Author
-
Gieffers C, Kluge M, Merz C, Sykora J, Thiemann M, Schaal R, Fischer C, Branschädel M, Abhari BA, Hohenberger P, Fulda S, Fricke H, and Hill O
- Subjects
- Animals, Antibodies, Monoclonal pharmacology, Antibodies, Monoclonal, Humanized, Antineoplastic Agents administration & dosage, Antineoplastic Agents chemistry, 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, Receptors, TNF-Related Apoptosis-Inducing Ligand agonists, Receptors, TNF-Related Apoptosis-Inducing Ligand antagonists & inhibitors, Recombinant Fusion Proteins administration & dosage, Recombinant Fusion Proteins chemistry, Xenograft Model Antitumor Assays, Antineoplastic Agents pharmacology, Peptide Fragments pharmacology, Receptors, IgG metabolism, Receptors, TNF-Related Apoptosis-Inducing Ligand metabolism, Recombinant Fusion Proteins pharmacology
- Abstract
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., (©2013 AACR.)
- Published
- 2013
- Full Text
- View/download PDF