Celldex Presents Data on CDX-1127, Says Elicits Potent Activation of Cells, Says Complement to Ongoing Clinical Development

Celldex Therapeutics, Inc.

today reported the results of an in vitro study analyzing the activation of human T cells with CDX-1127. CDX-1127 is a monoclonal antibody that binds CD27 and is designed to activate patients' immune cells against their cancer. The study further explored aspects related to both the potency and safety profile of CDX-1127. Results were consistent with earlier work, confirming the mechanism of action for CDX-1127 and providing additional support for continued clinical development of the candidate. The data were presented in a poster (#1239) entitled "Characterization of the Response of Human T cells to an Agonist Human Anti-CD27 mAb" at the American Association of Cancer Research (AACR) Annual Meeting in Washington DC by Tibor Keler, PhD, Senior Vice President and Chief Scientific Officer of Celldex Therapeutics. "The results of this study confirm that CDX-1127 elicits potent activation of T cells by inducing their proliferation and release of important immune modulating cytokines," said Dr. Keler. "Most importantly, we have shown that the activation is highly regulated, which limits any safety concerns related to non-specific stimulation of the immune system that similar candidates in this class have faced. This finding is supported by the good safety profile seen to date in our ongoing multi-dose Phase 1 human clinical trial. We believe CDX-1127 is an exciting entrant to the field of immunotherapy and look forward to presenting clinical data from planned solid tumor and hematologic expansion cohorts from our Phase 1 study by year-end." Study results: This study investigated the mechanistic requirements for T cell activation by CDX-1127 and the resulting characteristics of the activated T cells. Using purified T cells from healthy subjects, the results of this study demonstrated that concomitant signaling through the T Cell Receptor for antigen is required for CDX-1127 drug activity. Therefore, widespread activation of T cells (since the vast majority are not receiving T Cell Receptor signaling) will not be activated by CDX-1127. Importantly, when T cells are activated through T cell receptor stimulation and CDX-1127, they undergo multiple cell divisions, secrete cytokines with a dominant a proinflammatory signature (IFNγ, IL-2 and TNFα), and express activation markers consistent with an activated phenotype. Gene expression microarray analysis revealed modulation of intracellular signaling, protein kinases, growth and cytokine-chemokine pathways. These in vitro characterizations will be used to guide the biomarker analysis of subjects in the CDX-1127 Phase 1 trial to assess in vivo T cell activation. A copy of this poster is available for viewing in the Scientific Publications section of the Celldex website under the header "Human Monoclonal Antibody Programs: CD27."