Abstract 4405: Real-time, label-free assessment of HER2-targeted antibody-drug conjugate therapies

Abstract Antibody-drug conjugates (ADCs) are made of monoclonal antibodies covalently linked to small molecule drugs that, together, can improve both components’ anti-tumor effects. Several ADCs are targeted towards human epidermal growth factor receptor 2 (HER2), a cell surface receptor that is overexpressed in many cancers. Its increased expression in tumor cells makes HER2 an attractive target for cytotoxic therapies, allowing for the specific killing of cancer cells while minimizing off-target effects. Here, we developed an in vitro assay to measure the cytotoxic capacity of ADCs that use the HER2-targeted monoclonal antibody trastuzumab. This assay was performed in a real-time, label-free manner using the Maestro Z platform. The Maestro Z measures electrical impedance via electrodes embedded in the surface of the well to monitor cell growth and proliferation. To assess the cytotoxic effects of one HER2-targeted ADC, trastuzumab-deruxtecan (DS-8201a, branded as ENHERTU®), 5,000 HER2-positive SKOV3 cells were plated in CytoView Z plates and monitored for 24 hours before being dosed with increasing amounts of DS-8201a. SKOV3 cells were killed in a dose-dependent manner, and higher doses of DS-8201a led to larger decreases in SKOV3 impedance, indicative of greater SKOV3 death. SKOV3 cytolysis at the highest dose reached 90.9% at ∼ 5 days post dose, and the EC50 value was calculated to be 30.7 µg/mL. We also tested the effects of DS-8201a against other cell types with varying degrees of HER2 expression, including A549 (low HER2 expression) and MDA-MB-231 (no HER2 expression) cells. As expected, impedance data showed that DS-8201a had enhanced cytotoxic effects on the high HER2-expressing SKOV3 cells compared to the other two cell types with lower HER2 expression. Finally, we compared the cytotoxic effects of DS-8201a to another trastuzumab-based ADC, trastuzumab-emtasine (T-DM1, branded as Kadcyla®) on the Maestro Z. Taken together, these results show that the cytotoxic capacity of ADC therapies toward HER2 positive cell types can be screened using the Maestro Z. The assay presented here can be used to further develop ADC therapies aimed at HER2-positive cancers as well as ADCs toward other cancer-specific targets. Citation Format: Danny Flanigan, BEN STREETER, STACIE CHVATAL, DANIEL MILLARD. Real-time, label-free assessment of HER2-targeted antibody-drug conjugate therapies abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 4405.