In a research article published in PLOS ONE, scientists at ACEA Biosciences - a biotechnology company focused on the development of high performance cell analysis instruments, investigate the efficacy of a real-time in vitro potency assay for evaluating various immunotherapy treatments against both solid and liquid tumor cells. The study was presented at the 2018 American Association for Cancer Research (AACR) Annual Meeting in Chicago.
Immunotherapy, a powerful approach in which a patient’s immune system is prompted to attack cancerous cells, continues to show tremendous therapeutic potential. Despite substantial investment and research efforts into this area, challenges with developing effective treatments persist due to the complexity of the immune microenvironment. New methods are therefore being developed to address issues with predictability, long term efficacy, and variable patient responses to treatments.
In this study, the scientists develop a non-invasive assay using the xCELLigence platform to monitor cancer cell behavior as NK cells, CAR-T cells, Bi-specific T Cell Engagers (BiTEs) or immune checkpoint inhibitors are added. Designed to mimic physiologically relevant conditions, the xCELLigence platform continuously monitors target cell number, size, and viability while the cells remain undisturbed in the incubator. Besides research applications, the robustness and reproducibility of this assay make it well suited for quality control assessment of immunotherapies during batch manufacturing, or ex vitro clinical testing of a patient’s engineered immune cells prior to using them for treatment.
The novel real-time assay has significant advantages over traditional endpoint assays, which typically require labeling or engineering of the cells, are labor intensive to set up, and capture a single data point per sample. The chromium 51 release assay, long considered the gold standard for evaluating immune cell-mediated killing, requires the use of radioactive material and cannot accommodate time points longer than ~8 hours due to the high spontaneous leakage of isotope from the target cells. In contrast, the high sensitivity, continuous data acquisition, and flexible assay window (minutes to days) of the xCELLigence assay enable a much more comprehensive analysis of serial killing by the immune cells.
To standardize the analysis of therapeutic efficacy, the researchers developed an immunotherapy-specific software suite which enables the calculation of quantitative parameters such as KT50 (the amount of time it takes to kill 50% of the target tumor cells) and tumor cell % cytolysis over time. They further validated the real-time assay using parallel image-based analyses and flow cytometry, demonstrating that “the xCELLigence platform [is] well suited for potency assays, providing quantitative assessment with high reproducibility and a greatly simplified work flow.”
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