Improved antibody-PET tracers for in vivo imaging with GlyCLICK^®

Radioactively labelled antibodies are excellent immuno-PET tracers for evaluating in vivo distribution and performance of therapuetic agents. Site-specific conjugation at the antibody Fc glycan site by enzymatic remodeling allows for a uniform label distribution of such PET-tracers, compared to conjugates generated with conventional random labelling strategies.

In an article by Kristensen et al. (2019), the authors evaluated the stability, immunoreactivity and in vivo biodistribution of the radioactively labelled mAb Trastuzumab (Herceptin). Using GlyCLICK, the antibody was enzymatically modified with GlycINATOR (EndoS2) and conjugated with a DIBO-DFO chelator prior to ⁸⁹Zr radioactive labelling. Comparing the GlyCLICK technology with ß-galactosidase remodelled conjugates and two random labelling techniques, the authors obtained valuable data on the overall performance of the various PET-tracers.

Antibodies subjected to site-specific labelling showed significantly increased in vitro stability and immunoreactivity compared to randomly labeled Trastzumab. Furthermore, using in vivo immuno-PET imaging, these conjugates also displayed superior tumor-targeting properties based on the successful detection of HER2-positive tumors in mouse models. These results highlight the advantages of site-specific antibody conjugation.
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• GlyCLICK – Product description and characteristics

Reference:
Kristensen, L. et al., 2019. Site-specifically labeled 89Zr-DFO-trastuzumab improves immuno-reactivity and tumor uptake for immuno-PET in a subcutaneous HER2-positive xenograft mouse model. Theranostics, 9(15). pp.4409-4420.