Abstract 1373: Primary or iPSC-derived cell-based cytotoxicity assays to assess potential safety risks of engineered T cell therapies in vitro
Authors: Holt Sanne L. , Vermond Sophie , Hazenoot Monique , McLaughlin Rene , Guadagnoli Marco , Vlaming Marijn 
Published: July 2021

Abstract
Engineered T cell therapies, such as Chimeric Antigen Receptor (CAR) and T Cell Receptor (TCR) T cells, but also bi-specific antibody therapies, play a major role in the field of immuno-oncology and offer great promise in becoming a new wave of highly specific therapies against solid tumors. Solid tumors generally lack the expression of tumor specific target antigens, posing a significant safety challenge. Selected solid tumor target antigens are often expressed at low levels in healthy tissues throughout the human body, risking the activation of the engineered T cells against these tissues. This can potentially result in life-threatening side effects, as such, assessing the safety of engineered T cell therapies is a critical step during early development and before filing for Investigational New Drug (IND) status. We have generated an in vitro safety profile for CAR-T cells targeting the ‘Human Epidermal growth factor Receptor 2' (HER2). The gene encoding this receptor is found to be amplified and/or overexpressed in 20-30% of invasive breast carcinomas and ovarian cancers. To determine which tissues are most at risk for unwanted reactivity by the CAR-T cells, in silico analysis for expression of the HER2 gene was performed. Subsequently, HER2 protein expression in various tissues was validated by staining cells with a HER2 antibody and determining the percentage of positive cells by flow cytometry. Primary tissues and iPSC-derived cell with high and low HER2 protein expression were selected, characterized and utilized for in vitro co-culture assays to evaluate on-target off-tumor and/or off-target cytotoxicity of the HER2 targeting CAR-T cells. Readouts for the in vitro cytotoxicity assays included measuring target cell viability by flow cytometry and/or HCA and T cell activation by cytokine release. Our study generated high quality data that provided insight into the safety of the HER2 targeting CAR-T cells. Moreover, we were able to demonstrate the value of using iPSC-derived cells in de-risking selected tissues against unwanted reactivity of engineered T cell therapies. Our strategy to generate a safety profile for T cell therapies and bi-specific antibodies is robust can be applied during both early stage development and late stage testing of the therapeutic product. Engineered T cell therapies have the capacity to fill tremendous unmet medical needs and are moving into the clinic at a high rate. This expedited timetable, although good news for patients with late stage disease, results in less time to conduct the rigorous safety tests required before FDA approval. The use of primary tissues and iPSC derived cells to test the safety of these therapies in vitro has been and will be essential in getting these novel drugs on the market.
Citation Format: Sanne L. Holt, Sophie Vermond, Monique Hazenoot, Rene McLaughlin, Marco Guadagnoli, Marijn Vlaming. Primary or iPSC-derived cell-based cytotoxicity assays to assess potential safety risks of engineered T cell therapies in vitro [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1373.