Abstract 123: Evaluating cellular cytotoxicity and potency of antibody-drug conjugates within 3-dimensional tumor models

3-dimensional tumor spheroids provide biochemical conditions that closely resemble the tumor microenvironment in an intact organism. Noninvasive approaches such as fluorescence microscopy and high content analysis are highly advantageous as they allow for the study of these 3-dimensional systems. Here we investigate the penetration and potency of natural killer cells, cytotoxic T cells, and antibody‐drug conjugates in three‐dimensional models of breast and lung cancer. Unstimulated T cells produced minimal cytotoxicity, similar to untreated spheroids. Activated T cells penetrated and produced significant cytotoxicity throughout cancer spheroids. SKBR3 breast cancer cells form a compact, viable spheroid. Addition of NK cells leads to moderate cytotoxicity, while addition of NK cells and trastuzumab results in substantial cytotoxicity and degradation of spheroid structure. Trastuzumab labeled with iFL pHrodo Red becomes brightly fluorescent following specific endosomal internalization into breast cancer cells, but minimal toxicity is observed. Trastuzumab conjugated with both iFL pHrodo Red and MMAE internalizes into cells and results in cell killing. Fluorescence microscopy combined with novel cell and antibody labeling methods permits investigation of the penetration and potency of natural killer cells, cytotoxic T cells, and antibody‐drug conjugates in three‐dimensional solid tumor models. Citation Format: Bhaskar S. Mandavilli, Chris Langsdorf, Aimei Chen, Yi-Zhen Hu, Marcy Wickett, Scott T. Clark. Evaluating cellular cytotoxicity and potency of antibody-drug conjugates within 3-dimensional tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 123.