Abstract 1873: GlycoConnect™ ADCs based on topoisomerase 1 inhibitor exatecan (SYNtecan E™) show excellent in vivo efficacy and tolerability

Abstract

Abstract Camptothecins form a powerful class of chemotherapy drugs (e.g. irinotecan, topotecan, belotecan), based on their ability to inhibit topoisomerase I. Some camptothecins, such as DXd and SN-38, have also proven powerful payloads for antibody-drug conjugates (ADCs), as exemplified by the recent market approval of Enhertu® and Trodelvy®, respectively. We have reported earlier that the native glycan of monoclonal antibodies is a priviliged conjugation site for ADCs (GlycoConnect™)1, while the highly polar spacer technology (HydraSpace™)2 enables the conjugation of any cytotoxic payload, providing ADCs with significantly expanded therapeutic index (TI) versus mainstream ADC technologies. We here show that exatecan (DX-8951f), a clinically validated and potent campothecin, is readily combined with HydraSpace™ technology to provide linker-payload (SYNtecan E™). Homogeneous and stable GlycoConnect™ADCs were generated from trastuzumab and SYNtecan E™ and compared head-to-head with DXd or SN-38payload, as well as deruxtecan, the linker-payload applied in Enhertu®. Complete tumor regression was observed in a mouse xenograft study (BT-474) after a single dose, while safety studies in mouse corroborated the high tolerability of SYNtecan E™ ADCs. Taken together, these studies demonstrate the potential of SYNtecan E™ for application in stable and site-specific ADCs with excellent therapeutic index. 1 van Geel et al. Chemoenzymatic Conjugation of Toxic Payloads to the Globally Conserved N-Glycan of NativemAbs Provides Homogeneous and Highly Efficacious Antibody−Drug Conjugates. Bioconj. Chem. 2015, 26, 2233-2242. 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: Floris van Delft. GlycoConnect™ ADCs based on topoisomerase 1 inhibitor exatecan (SYNtecan E™) show excellent in vivo efficacy and tolerability [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1873.