title: In vivo imaging of protease activity by Probody therapeutic activation.
abstract: 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.
authors.affiliation: CytomX Therapeutics, Inc., 343 Oyster Point Blvd, South San Francisco, CA 94080, USA.
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Wong
authors.affiliation: CytomX Therapeutics, Inc., 343 Oyster Point Blvd, South San Francisco, CA 94080, USA.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Menendez
authors.affiliation: Department of Pharmaceutical Chemistry, University of California, 600 16th Street, San Francisco, CA 94158, USA.
authors.forename: Charles S
authors.initials: CS
authors.lastname: Craik
authors.affiliation: CytomX Therapeutics, Inc., 343 Oyster Point Blvd, South San Francisco, CA 94080, USA.
authors.forename: W Michael
authors.initials: WM
authors.lastname: Kavanaugh
authors.affiliation: CytomX Therapeutics, Inc., 343 Oyster Point Blvd, South San Francisco, CA 94080, USA. Electronic address: olga@cytomx.com.
authors.forename: Olga
authors.initials: O
authors.lastname: Vasiljeva
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D001667:Binding, Competitive; D045744:Cell Line, Tumor; D000068818:Cetuximab / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D003952:Diagnostic Imaging / Q000379:methods; D066246:ErbB Receptors / Q000378:metabolism; D005260:Female; D005456:Fluorescent Dyes / Q000737:chemistry; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D008819:Mice, Nude; D010447:Peptide Hydrolases / Q000378:metabolism; D011355:Prodrugs / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D011485:Protein Binding; D015203:Reproducibility of Results; D013388:Succinimides / Q000737:chemistry; D013997:Time Factors; D023041:Xenograft Model Antitumor Assays / Q000379:methods*
chemical_list: C502599:Alexa Fluor 750; D000911:Antibodies, Monoclonal; D000970:Antineoplastic Agents; D005456:Fluorescent Dyes; D011355:Prodrugs; D013388:Succinimides; D066246:ErbB Receptors; D010447:Peptide Hydrolases; D000068818:Cetuximab
keywords: In vivo imaging; Monoclonal antibody; Protease activity; Tumor targeting