Application of clinical stage GlycoConnect® technology to bispecific antibodies yields improved bispecific ADCs in comparison to randomly conjugated bsADCs

Several bispecific antibodies (bsAbs), with the ability to bind selectively and in a concerted fashion to two tumor associated antigens (TAAs) or in the form of a biparatopic antibody, have meanwhile been approved for cancer therapy. Another increasingly successful modality for anti-cancer therapy are antibody-drug conjugates (ADCs). Although typically based on random conjugation to cysteine or lysine residues, we have shown that the native glycan of monoclonal antibodies is a privileged site for attachment of cytotoxic payloads 1 , while the therapeutic index is further enhanced by a highly polar spacer technology (HydraSpace®) 2 . Complemented by a broad choice of payloads with various modes-of-action (toxSYN® platform), these technologies have jointly been applied in multiple clinical ADC programs with the most advanced now in phase 3. As multiple different bsAb formats have been introduced and are currently in clinical trials 3 we wanted to understand how GlycoConnect® conjugation technology would work in context of different bsAb formats to create site-specific ADCs with defined DAR. To this end, GlycoConnect® bispecific ADCs (bsADCs) were generated with high yield and purity and the successful application of the GlycoConnect® technology was demonstrated for several different bsAb formats. In addition, we will show the advantages of GlycoConnect® conjugation in generating bsADCs compared to random cysteine conjugation. GlycoConnect® bsADCs are more homogeneous than randomly conjugated bsADCs, have improved stability and provide for compelling antitumor activity in in vivo cancer xenograft models. 1 (a) van Geel et al . Bioconj. Chem. 2015, 26 , 2233-2242. (b) Wijdeven et al. MAbs 2022, DOI: 10.1080/19420862.2022.2078466. 2 Verkade et al . Antibodies 2018, 7 , 12, doi:10.3390/antib7010012. 3 Herrera et al. Trends in Cancer 2024, 10, 10, doi.org/10.1016/j.trecan.2024.07.002.