Abstract 2664: An anti-Jagged-1/-2 Probody demonstrates inhibition of Jagged-dependent Notch signaling and is activated in multiple types of tumors
Authors: Vasiljeva Olga , Menendez Elizabeth , Sagert Jason , West James W. , Richardson Jennifer , Desnoyers Luc , Liu Shouchun , Ford Judi , Plou Krishna , Lowman Henry 
Published: May 2015

Abstract
Probodies represent a unique class of antibody therapeutics that specifically target therapeutic activity to diseased tissues, such as cancer. A Probody is a fully recombinant protein that contains a masking peptide that blocks the antibody's antigen-binding site and is linked to the light chain of the antibody by a protease-cleavable peptide substrate. Probodies are designed to be inactive in circulation and in healthy tissues but activated within the tumor microenvironment. The Probody™ approach is designed to widen the therapeutic index of antibodies to promising therapeutic targets that may be limited by significant toxicity. One such promising set of targets are components of the Notch pathway, which is involved in both oncogenic and healthy tissue signaling.
We have developed a fully human IgG1 monoclonal antibody that binds and inhibits the activity of both human and mouse Jagged-1 and Jagged-2, two key ligands in the Notch signaling pathway. A Probody produced from this antibody induced dose-dependent inhibition of Notch signaling, resulting in anti-tumor activity in in vivo tumor models without significant toxicity.
To further explore the clinical relevance of the anti-Jagged Probody for the treatment of cancer, we evaluated (i) the heterogeneity of Jagged expression in multiple tumor types, (ii) the activation of the Jagged Probody in tumor biopsies, and (iii) the blockade of Notch signaling using an intracellular pharmacodynamic biomarker. Patient tumor tissues were screened for Jagged-1/-2 IHC across lung, pancreatic and breast cancer_ indications where activation of the Notch pathway is implicated. Overall, more than 75% of patient tumors demonstrated moderate to high Jagged-1/-2 expression. We also developed and validated a technique termed IHZ™ analysis that enables the measurement of proteolytic Probody activation and binding to Jagged ligands ex vivo in human tumor sections. We evaluated 120 patients across the three tumor types and observed ∼99% of samples that were positive for antibody binding were also positive by IHZ analysis, signifying sufficient proteolytic activity to activate the Probody. Finally, we evaluated the accumulation of the Notch Intracellular Domain (NICD), a biomarker of Notch signaling, in the nucleus of tumor cells in animals treated with antibody. Notably, our data showed that Notch signaling blockade as indicated by a decrease in the accumulation of NICD correlated with dose-response in in vivo models. Taken together, our data suggest that the anti-Jagged-1/-2 Probody may have wide therapeutic utility as a tumor-specific inhibitor of Jagged-dependent Notch signaling in oncology.
Citation Format: Olga Vasiljeva, Elizabeth Menendez, Jason Sagert, James W. West, Jennifer Richardson, Luc Desnoyers, Shouchun Liu, Judi Ford, Krishna Plou, Henry Lowman. An anti-Jagged-1/-2 Probody demonstrates inhibition of Jagged-dependent Notch signaling and is activated in multiple types of tumors. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2664. doi:10.1158/1538-7445.AM2014-2664