In Vivo Pretargeted Imaging of HER2 and TAG-72 Expression Using the HaloTag Enzyme.

A novel pretargeted SPECT imaging strategy based on the HaloTag enzyme has been evaluated for the first time in a living system. To determine the efficacy of this approach, two clinically relevant cancer biomarkers, HER2 and TAG-72, were selected to represent models of internalizing and noninternalizing antigens, respectively. In MDA-MB-231/H2N (HER2-expressing) and LS174T (TAG-72-expressing) xenograft tumors in mice, pretargeting experiments were performed in which HaloTag-conjugated derivatives of the antibodies trastuzumab (anti-HER2) or CC49 (anti-TAG-72) were utilized as primary agents, and the small molecule HaloTag ligands 111In-HTL-1, -2, and -3 were evaluated as secondary agents. While this approach was not sufficiently sensitive to detect the internalizing HER2 antigen, pretargeting experiments involving the most optimal secondary agent, 111In-HTL-3, were successful in detecting the noninternalizing antigen TAG-72 and provided high-contrast SPECT images at 4 and 24 h postinjection.

Citation

James C Knight, Michael Mosley, H Tetsuo Uyeda, Mei Cong, Frank Fan, Stephen Faulkner, Bart Cornelissen. In Vivo Pretargeted Imaging of HER2 and TAG-72 Expression Using the HaloTag Enzyme. Molecular pharmaceutics. 2017 Jul 03;14(7):2307-2313

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PMID: 28505463

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