Abstract A108: Specific and traceless payload release from HER2-ADC containing LBG-linker prodrug by the action of lysosomal β-glucuronidase

Many antibody-drug conjugates (ADCs) have actively been evaluated in clinical trials since Mylotarg was approved in 2001, but only 4 more have been approved by the FDA. The main reason for the poor results is yet to overcome worse risk-benefit than the expected from ADC approach. Controlled payload release specifically at cancer cells would significantly reduce systemic toxicity. Herein, we report that LBG000-linker can be selectively cleaved from ADC to release free toxins in a traceless manner by β-glucuronidase. Lysosomal β-glucuronidase is overexpressed in many cancer cell lines, and its enzymatic activity is much higher in acidic condition than neutral pH. As a model reaction, an LBG-linker-MMAE conjugate, LCB14-0302, was incubated with a β-glucuronidase in vitro resulting clean release of free MMAE while other lysosomal enzymes such as cathepsin B or heparanase did not generate the free toxin. We also confirmed that there was no free MMAE found when β-glucuronidase inhibitor, β-D-glucuronic acid, was treated. Also, lysosomal extract incubation with LCB14-0302 clearly demonstrated the traceless toxin release by β-glucuronidase regardless of other enzymatic disturbance. Therefore, these results strongly suggest that LBG-linker is highly stable and specific to β-glucuronidase among hundreds of enzymes in the lysosome. Citation Format: Dong Yeon Shin, Taeik Jang, Ho Young Song, Sung Min Kim, Yun-Hee Park, Chang Sik Park, Hwanhee Oh, Juyuel Baek, Jeiwook Chae, Chang-Sun Lee. Specific and traceless payload release from HER2-ADC containing LBG-linker prodrug by the action of lysosomal β-glucuronidase [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr A108. doi:10.1158/1535-7163.TARG-19-A108