Measuring potency of bispecific effector/target-linking antibodies for inducing cytotoxicity of tumor cells using an impedance-based assay platform (P2094)

• Published in: The Journal of immunology (1950) Vol. 190; no. 1_Supplement; pp. 132 - 132.37
• Main Authors: Young, Judy, Montgomery, Harley, Sun, Laura, Junttila, Teemu, Mai, Elaine
• Format: Journal Article
• Language: English
• Published: 01-05-2013
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.190.Supp.132.37

Cancer patients mount weak tumor-specific T-cell responses due to immune escape mechanisms of tumors. Although cytotoxic T-cells are potent killers, activation requires antigen processing, specific recognition, and co-stimulation. Bispecific antibody-derived proteins that bind both CD3 and tumor antigens can bypass these requirements by directly linking cytotoxic T cells to tumor cells and have been shown clinically to enhance T cell-mediated tumor cell killing. Our goal was to assess the relative potency of anti-CD3/anti-tumor antigen full-length IgG1 bispecific antibodies. Assays based on electrical impedance are well suited for tumor cell killing assays because the adherent target cells generate an impedance signal, while the non-adherent effector cells do not. Human tumor cells were plated with CD8+ T cells and bispecific antibodies, and cytotoxicity was recorded in real time at intervals during culture. Tumor cell killing was found to be dependent on the bispecific antibody concentration, with EC50 values of 27-40 pM. In addition, killing was dependent on the number of CD8 T cells added, with an optimal effector:target cell ratio of 4:1. Compared to a well established but labor-intensive FACS-based assay performed in parallel, the results of the impedance assay agreed closely. Moreover, impedance-based cell killing assays have the advantages of real-time, label-free readings as well as simple assay development and performance.