Effect of small-molecule-binding affinity on tumor uptake in vivo: a systematic study using a pretargeted bispecific antibody.

Small-molecule ligands specific for tumor-associated surface receptors have wide applications in cancer diagnosis and therapy. Achieving high-affinity binding to the desired target is important for improving detection limits and for increasing therapeutic efficacy. However, the affinity required for maximal binding and retention remains unknown. Here, we present a systematic study of the effect of small-molecule affinity on tumor uptake in vivo with affinities spanning a range of three orders of magnitude. A pretargeted bispecific antibody with different binding affinities to different DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid)-based small molecules is used as a receptor proxy. In this particular system targeting carcinoembryonic antigen, a small-molecule-binding affinity of 400 pmol/L was sufficient to achieve maximal tumor targeting, and an improvement in affinity to 10 pmol/L showed no significant improvement in tumor uptake at 24 hours postinjection. We derive a simple mathematical model of tumor targeting using measurable parameters that correlates well with experimental observations. We use relations derived from the model to develop design criteria for the future development of small-molecule agents for targeted cancer therapeutics.
AuthorsKelly Davis Orcutt, John J Rhoden, Benjamin Ruiz-Yi, John V Frangioni, K Dane Wittrup
JournalMolecular cancer therapeutics (Mol Cancer Ther) Vol. 11 Issue 6 Pg. 1365-72 (Jun 2012) ISSN: 1538-8514 [Electronic] United States
PMID22491799 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)
Copyright©2012 AACR
Chemical References
  • Antibodies, Bispecific
  • Carcinoembryonic Antigen
  • Chelating Agents
  • Coordination Complexes
  • Haptens
  • Heterocyclic Compounds, 1-Ring
  • Indium Radioisotopes
  • Radioisotopes
  • Radiopharmaceuticals
  • Lutetium
  • 1,4,7,10-tetraazacyclododecane- 1,4,7,10-tetraacetic acid
  • Animals
  • Antibodies, Bispecific (chemistry, metabolism)
  • Carcinoembryonic Antigen (metabolism)
  • Cells, Cultured
  • Chelating Agents (pharmacokinetics)
  • Coordination Complexes (pharmacokinetics)
  • Haptens
  • Heterocyclic Compounds, 1-Ring (pharmacokinetics)
  • Humans
  • Indium Radioisotopes
  • Lutetium
  • Mice
  • Mice, Nude
  • Models, Biological
  • Neoplasm Transplantation
  • Neoplasms, Experimental (metabolism, pathology, radiotherapy)
  • Radioimmunotherapy
  • Radioisotopes
  • Radiopharmaceuticals (pharmacokinetics)
  • Tissue Distribution
  • Transplantation, Heterologous

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