Humanized A33 (huA33) is a monoclonal antibody that targets the A33 antigen, a transmembrane glycoprotein expressed in >95% of human colon adenocarcinomas. The absence of the antigen from most non-cancerous tissues has made huA33 a promising candidate for use in imaging applications, particularly PET. We have sought to evaluate 89Zr-labeled huA33 as a PET imaging agent for A33 antigen-expressing colorectal cancer xenografts. To this end, huA33 was modified with the chelator desferrioxamine (DFO) via isothiocyanate linkage, labeled with 89Zr, and purified to yield 89Zr-DFO-huA33 in high radiochemical purity, specific activity (4.5-5.0 mCi/mg), and immunoreactivity (>88 � 4%). Small animal PET imaging and acute biodistribution experiments with nude mice bearing A33 antigen-expressing SW1222 colorectal cancer xenografts revealed high specific uptake of the 89Zr-DFO-huA33 in the xenografts (56.7 � 7.8%ID/g and 70.9 � 10.1%ID/g at 24 and 48 h, respectively) with low levels of uptake in all non-target tissues.

Positron emission tomography imaging of colorectal cancer with <sup>89</sup>Zr-labeled huA33 antibody

243rd National Meeting (2012)

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Positron emission tomography imaging of colorectal cancer with 89Zr-labeled huA33 antibody

Positron emission tomography imaging of colorectal cancer with ⁸⁹Zr-labeled huA33 antibody