A novel method for early monitoring of chimeric antigen receptor T cells

Chimeric antigen receptor T cells immunotherapy is one of the most subversive technologies for cancer treatment. A typical example is the Emily's story, a 7-year-old girl with acute lymphoblastic leukemia, who was the first child in the world received CAR T cell therapy in 2012, and has survived for 7 years. However, responses to this therapy are various. So, early screening patient is very urgent. Recently, ⁸⁹Zr-oxine has been mostly used for cell labelling in preclinical study. With PET imaging, the biodistribution of CAR T cells injected can be clearly shown. But the main obstacle is high and long-term radiation exposure to cells and other normal organs such as lung, liver and spleen. So far, no clinical CAR T cell studies of ⁸⁹Zr directly labelled have been reported. In this study, we want to develop a new method using short half-life nuclides ⁶⁸Ga for early and safe tracking CAR T cells. First, ⁶⁸Ga-oxine/⁸⁹Zr-oxine complex was generated at room temperature. Secondly, ⁶⁸Ga-oxine/⁸⁹Zr-oxine solution and CAR T cells were incubated in PBS to prepare labelled CAR T cell, the cell viability and stability were detected after labelled completely. Thirdly, the biodistribution of ⁶⁸Ga/⁸⁹Zr labelled CAR T cells were dynamically monitored with micro PET in NOG mice. ⁶⁸Ga/⁸⁹Zr-oxine can be achieved at 37 ° C and pH 5-6 for 15 min. The radiochemical purity was >90% by TLC. ⁶⁸Ga/⁸⁹Zr-oxine labelled with CART cells at room temperature for 15 min with about 20% yield. Specific activity below 370 KBq/106 cells, no effect on cell viability (>90%). Micro PET imaging showed that after intravenous administration of ⁶⁸Ga or ⁸⁹Zr-oxine labelled CAR T cells, the radioactivity was initially concentrated in the lung, subsequently distribution in the liver and spleen. During the 6 h dynamic monitoring, the radio uptake of lung and spleen were basically the same between ⁶⁸Ga-oxine and 89Zr-oxine labelled CAR T cells. CAR T cells can be labelled with ⁶⁸Ga-oxine and ⁸⁹Zr-oxine, with high viability after labelling (>90%). Within 6 h monitoring, the same biological behaviors were observed between ⁶⁸Ga and ⁸⁹Zr labelled CAR T cells in NOG mice. In conclusion, ⁶⁸Ga-oxine labelled CAR T cell is promising for early diagnosis and safe screening patients with CAR T cell therapy. (author)