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bioRxiv · 10.64898/2026.09.23.753936

Size-dependent effect of site-specific polyethylene glycol modification of trastuzumab on the antibody functions

Tsutsui, Y.·Ohno, H.·Akiba, H.
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Abstract

Polymer modification of antibodies has attracted attention for enhancing antibody functionality. Modification with polyethylene glycol (PEG) or biopolymers such as antibody-oligonucleotide conjugates has been investigated. Although direct effects at the modification site have been understood, distal effects of modifications on intrinsic antibody functions such as antigen-binding and Fc receptor-binding activities remain poorly characterized. In this study, we prepared site-specifically PEGylated trastuzumab to evaluate the effects of the modification site and the size of PEG chains on antibody functions. Reporter gene assays revealed a significant reduction in antibody-dependent cell cytotoxicity (ADCC) activity in a site- and size-dependent manner. Both the reduction in interaction with the antigen and Fc{gamma}RIIIa were observed in a size-dependent manner. Interestingly, the effect of the modification site was only observed for ADCC activity, which suggests that the higher-order structure of the modified antibody plays a critical role in effector function. These results provide molecular design guidelines for the polymer modification of antibodies.

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Tsutsui, Y., Ohno, H., Akiba, H.. 2026-09-24. Size-dependent effect of site-specific polyethylene glycol modification of trastuzumab on the antibody functions. https://doi.org/10.64898/2026.09.23.753936

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