Abstract LB-106: Overcoming limitations of current Antibody-Drug Conjugates (ADCs) by a novel linker technology

Abstract

Abstract We introduce a novel and versatile ADC-linker technology that is based on site-specific enzymatic payload conjugation to ‘off-the-shelf’ antibodies, i.e., without the need to reduce or engineer the antibody. The functionalization takes place site-specifically and stoichiometrically (drug-to-antibody ratio, DAR = 2.0) at the Fc-part of antibodies. The resulting ADCs show favorable biophysical properties such as high solubility and stability using different payloads. Additionally, initial ELISA findings show that our modification does not interfere with Fc-gamma receptor and FcRn binding. Importantly, our ADCs showed superior efficacy in different tumor animal models as compared to control Thiomab™ ADCs. Using native trastuzumab (non-engineered) as the targeting antibody and amanitin as payload, we generated within 36 hours highly homogeneous and pure ADCs with a well-defined DAR of 2.0 as confirmed by LC-MS. In in-vitro assays our ADCs demonstrated potent cytotoxicity in all tested cell-lines (SKBR-3, BT-474, JIMT-1, and NCI-N87) as compared to the control Thiomab™ ADCs, most strikingly for the JIMT-1 cell-line: EC50 of 0.15nM vs 2.5nM. In the mouse JIMT-1 tumor model, our anti-HER2 ADC was highly potent and resulted in complete tumor remission in all mice (10/10 mice) at a single dose of 2mg/kg. In contrast, the control Thiomab™-functionalized ADC showed tumor regrowth in 4 out of 10 animals, starting on day 50. The same high potency was observed for the NCI-N87 xenograft model at a dose of 3mg/kg in which tumor growth inhibition was significantly delayed versus the reference ADC (8/10 vs 4/10 animals alive on day 110). These encouraging results obtained so far indicate that our linker technology a) allows for fast (< 36 hours) and straightforward manufacturing of ADCs using different payloads without protein engineering efforts, b) results in ADCs with favorable biophysical properties and a clear defined drug-to-antibody ratio, and c) enables the generation of highly potent and stable, thus safer, next-generation ADCs. Citation Format: Philipp Rene Spycher, Julia Carina Frei, Jöri Elias Wehrmüller, Isabella Attinger-toller, Dragan Grabulovski, Torsten Hechler, Michael Kulke, Andreas Pahl, Martin Behe, Roger Schibli. Overcoming limitations of current Antibody-Drug Conjugates (ADCs) by a novel linker technology [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-106.