Development of a flow cytometry method to measure antidrug antibodies against CAR T cells

Chimeric antigen receptor (CAR) T cell therapies are based on the genetic modification of the T cell receptor of a patient's own T cells. The resulting CAR T cells cytotoxic response is redirected against a specific tumor antigen. This innovative immunotherapy has been used successfully to treat blood malignancies, and it is also being developed as treatment for solid tumors. CAR T cells can lead to immune related adverse outcomes associated with an unwanted immune response in the host, ranging from acute events to those sustained with time, such as antidrug antibody (ADA) development, which can impact the efficacy and persistence of the CAR T cells once administered to the patient. The development of ADAs as response to a drug treatment is not exclusive to CAR T cells, and evidence of their production has been long acknowledged. While traditional types of analysis aim to measure the presence of ADAs by immunoassay methods, with the therapeutic agent being cells, the use of a flow cytometry approach has become the obvious choice for detection and quantification of ADAs against CAR T cells products, as well as any other cell therapies. Here, we present the results of the development of a flow cytometry method to measure ADAs using CAR T cells with an assay to detect the binding of an ADA-like molecule to the CAR T cells in a dose-dependent manner. This method allowed for quantification of ADAs and determination of the assay values needed for potential ADA measurement in clinical samples.