P-08.05 Dried antibody cocktails are setting the benchmark for fast and robust CAR T cell flow cytometric analysis

<h3>Background</h3> CAR T cell therapy represents without any doubt a major breakthrough in the treatment of hematological malignancies. For the clinical manufacturing of CAR T cells as well as for research and pre-clinical applications, the specific detection of CAR expression along with the characterization of the cellular composition is of utmost importance. In addition, monitoring patients who received CAR T cell therapy is crucial for assessing therapy effectiveness and for making timely adjustments to the treatment plan. Generating comparable results across different treatment centers worldwide is essential to ensure consistent patient care, yet still remains a major challenge. We developed dried antibody cocktails that allow fast and robust flow cytometric cell analysis, including highly specific CAR detection. Thereby, we want to improve the global comparability and efficiency of the CAR T cell manufacturing, and to enable uniform patient monitoring. <h3>Materials and Methods</h3> Our dried antibody cocktails enable comprehensive analysis throughout the entire CAR T cell manufacturing process including analysis of the starting material, in-process and quality controls, as well as subsequent patient immunomonitoring. Due to the ready-to-use format the cell material can directly be added to the tubes containing the dried cocktail, followed by a short incubation period before acquisition on a flow cytometer. This makes the dried antibody cocktails extremely easy to handle, even without extensive training. <h3>Results</h3> We were able to show that staining results using dried antibody cocktails are comparable to the use of liquid antibody mixes. In addition, we demonstrated a tremendous speed-up of the staining procedure for both experienced and unexperienced operators. By reduction of the manual steps, the risk of human errors is minimized, leading to a low operator and day-to-day variability. Furthermore, the dried format allows extended storage at ambient conditions without considerable reduction of staining performance. This reduces assay variability due to inappropriate storage conditions or reagent handling. In addition, our results demonstrated that the dried antibody cocktails show a high lot-to-lot consistency. Thereby, the dried panels facilitate a uniform, reproducible, and robust flow cytometric analysis. Furthermore, we designed panels that deliberately offer free fluorescent channels, thus enabling flexible panel complementation: additional liquid antibodies or CAR detection reagents can easily be included into the staining procedure for a custom-tailored application. <h3>Conclusions</h3> Our dried antibody cocktails represent a significant advancement in making flow cytometric analysis faster and more robust without any forfeit in staining performance compared to liquid reagents. With this we can improve the global standard of analytics for CAR T cell therapy. <b>Borgelt:</b> A. Employment (full or part-time); Significant; Miltenyi Biotec B.V. &amp; Co. KG. <b>Borgelt Missing:</b> A. Employment (full or part-time); Significant; Miltenyi Biotec B.V. &amp; Co. KG. <b>Borgelt Missing Brauchle:</b> A. Employment (full or part-time); Significant; Miltenyi Biotec B.V. &amp; Co. KG. <b>Borgelt Missing Brauchle Kammeyer:</b> A. Employment (full or part-time); Significant; Miltenyi Biotec B.V. &amp; Co. KG. <b>Borgelt Missing Brauchle Kammeyer Wilmes:</b> A. Employment (full or part-time); Significant; Miltenyi Biotec B.V. &amp; Co. KG. <b>Borgelt Missing Brauchle Kammeyer Wilmes Dose:</b> A. Employment (full or part-time); Significant; Miltenyi Biotec B.V. &amp; Co. KG. <b>Borgelt Missing Brauchle Kammeyer Wilmes Dose Richter:</b> A. Employment (full or part-time); Significant; Miltenyi Biotec B.V. &amp; Co. KG. <b>Borgelt Missing Brauchle Kammeyer Wilmes Dose Richter Mues:</b> A. Employment (full or part-time); Significant; Miltenyi Biotec B.V. &amp; Co. KG.