Utility of Cu for immuno-PET; In vivo measurement of radiation dose for radioimmunotherapy

Iida, Yasuhiko*; Hanaoka, Hirofumi*; Katabuchi, Tatsuya*; Watanabe, Satoshi; Ishioka, Noriko; Matsuhashi, Shimpei; Oriuchi, Noboru*; Higuchi, Tetsuya*; Miyakubo, Mitsuyuki*; Endo, Keigo*

Radioimmunotherapy (RIT) becomes one of the most promising treatments for cancer therapy. Recently, RIT becomes available for clinical use and shows high efficacy, but it has some adverse effects for radiation to normal tissues and its therapeutic window is limited. So, assessment of radiation dose deliver to both tumor and normal tissues is very important for RIT. PET is superior in quantitative measurement and it can estimate radiation dose directly. Although representative positron emitter has short half-life, which is not good for labeling of antibody, Cu has appropriate property, T = 12.7 hr, and it may have a great potential for immuno-PET. In this study, we prepared a radioimmunoconjugate, NuB2, anti-CD20 monoclonal antibody (mAb), labeled with Cu, and evaluated potential for in vivo quantitative measurement of radiation dose for RIT. NuB2 was labeled with Cu. For in vivo studies, SCID mice bearing CD20 tumor were used. After administration, biodistribution and PET imaging were performed. For the results of biodistribution, Cu-NuB2 was highly accumulated to CD20 tumor, and PET images could show the same results. From these date, the use of Cu immuno-PET has potential for accurately measurement of radiation dose for RIT.