Abstract 2614: GlycoConnect™ ADC toolbox expansion with high DAR technology

Abstract Recently topoisomerase 1 inhibitors have gained significant traction as a cytotoxic payload for ADCs based on the clinical success of camptothecin-based ADCs Enhertu® (DXd) and Trodelvy® (SN-38). In contrast to the majority of other approved ADCs, both Enhertu® and Trodelvy® are feature an average of 7-8 payloads per antibody. Obviously, such a high drug-to-antibody ratio (DAR) effectively delivers more drug to the tumor per internalization event, which is key in driving the clinical success. Previously, we have shown that the native glycan of monoclonal antibodies is a privileged site for attachment of cytotoxic payloads1, for the generation of site-specific and stable ADCs with DARs varying from 1-6, while the therapeutic index is further elevated by a highly polar spacer technology (HydraSpace™)2. The success of GlycoConnect™/HydraSpace™ ADCs is further driven by the use of exatecan as a potent and highly cell-permeable payload (SYNtecan E™). Here we show that GlycoConnect™ technology can be readily extended to generate efficacious and safe DAR8 ADCs. We have developed a modular, non-genetic method, involving three simple process steps from any antibody: (a) enzymatic glycan remodeling, (b) strain-promoted azide-alkyne cycloaddition of a bifunctional, branched spacer comprising one strained alkyne and two orthogonal click tags (e.g. tetrazines), and (c) inverse electron-demand Diels-Alder cycloaddition with a branched linker-drug construct based on BCN and a two cytotoxic payloads. The resulting conjugates, with DAR 6 or 8, are rapidly generated with high homogeneity and with good stability. In addition, HIC profiles of the resulting ADCs indicate small relative retention time as an indication of good PK profile. Excellent in vivo tolerability is demonstrated, while efficacy studies in mice xenograft models show that the DAR8 technology clearly out-performs currently marketed ADCs (including Enhertu®). 1 (a) van Geel et al. Chemoenzymatic Conjugation of Toxic Payloads to the Globally Conserved N-Glycan of Native mAbs Provides Homogeneous and Highly Efficacious Antibody−Drug Conjugates. Bioconj. Chem. 2015, 26, 2233-2242. (b) Wijdeven et al. Enzymatic glycan remodeling-metal free click (GlycoConnect™) provides homogenous antibody-drug conjugates with improved stability and therapeutic index without sequence engineering. MAbs 2022, DOI: 10.1080/19420862.2022.2078466. 2 Verkade et al. A Polar Sulfamide Spacer Significantly Enhances the Manufacturability, Stability, and Therapeutic Index of Antibody-Drug Conjugates. Antibodies 2018, 7, 12, doi:10.3390/antib7010012. Citation Format: Lianne Lelieveldt, Elias Post, Marie Nassiet, Veronique Hendriks, Mick Verhagen, Remon van Geel, Sander van Berkel, Floris van Delft. GlycoConnect™ ADC toolbox expansion with high DAR technology [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2614.