In vivo imaging of protease activity by Probody therapeutic activation

Biochimie. 2016 Mar;122:62-7. doi: 10.1016/j.biochi.2015.11.003. Epub 2015 Nov 4.


Probody™ therapeutics are recombinant, proteolytically-activated antibody prodrugs, engineered to remain inert until activated locally by tumor-associated proteases. Probody therapeutics exploit the fundamental dysregulation of extracellular protease activity that exists in tumors relative to healthy tissue. Leveraging the ability of a Probody therapeutic to bind its target at the site of disease after proteolytic cleavage, we developed a novel method for profiling protease activity in living animals. Using NIR optical imaging, we demonstrated that a non-labeled anti-EGFR Probody therapeutic can become activated and compete for binding to tumor cells in vivo with a labeled anti-EGFR monoclonal antibody. Furthermore, by inhibiting matriptase activity in vivo with a blocking-matriptase antibody, we show that the ability of the Probody therapeutic to bind EGFR in vivo was dependent on protease activity. These results demonstrate that in vivo imaging of Probody therapeutic activation can be used for screening and characterization of protease activity in living animals, and provide a method that avoids some of the limitations of prior methods. This approach can improve our understanding of the activity of proteases in disease models and help to develop efficient strategies for cancer diagnosis and treatment.

Keywords: In vivo imaging; Monoclonal antibody; Protease activity; Tumor targeting.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Antibodies, Monoclonal / chemistry
  • Antibodies, Monoclonal / metabolism
  • Antibodies, Monoclonal / pharmacology*
  • Antineoplastic Agents / chemistry
  • Antineoplastic Agents / metabolism
  • Antineoplastic Agents / pharmacology
  • Binding, Competitive
  • Cell Line, Tumor
  • Cetuximab / chemistry
  • Cetuximab / metabolism
  • Cetuximab / pharmacology
  • Diagnostic Imaging / methods
  • ErbB Receptors / metabolism
  • Female
  • Fluorescent Dyes / chemistry
  • Humans
  • Lung Neoplasms / drug therapy*
  • Lung Neoplasms / metabolism
  • Mice, Nude
  • Peptide Hydrolases / metabolism
  • Prodrugs / chemistry
  • Prodrugs / metabolism
  • Prodrugs / pharmacology*
  • Protein Binding
  • Reproducibility of Results
  • Succinimides / chemistry
  • Time Factors
  • Xenograft Model Antitumor Assays / methods*


  • Alexa Fluor 750
  • Antibodies, Monoclonal
  • Antineoplastic Agents
  • Fluorescent Dyes
  • Prodrugs
  • Succinimides
  • ErbB Receptors
  • Peptide Hydrolases
  • Cetuximab