Development of novel lysosome-targeting chimera for HER2 receptor degradation

Abstract

Targeted therapies aim to disrupt specific molecules crucial for cell growth, but many proteins are challenging to target ("undruggable"). Targeted protein degradation (TPD), exemplified by proteolysis-targeting chimeras (PROTACs), has emerged to address these challenges but is limited to cytoplasmic proteins. Lysosome-targeting chimeras (LYTACs) offer a solution by directing extracellular and membrane proteins to lysosomes for degradation. This study introduces Albumin-mediated lysosomal targeting chimeras (AlbuTAC), utilizing human serum albumin (HSA) for targeted degradation. Human epidermal growth factor receptor 2 (HER2), overexpressed in 15-20% of breast cancers, was selected as the model target. The 4D5 single-chain variable fragment (scFv) from Trastuzumab was chosen for HER2 binding. Employing the inverse electron-demand Diels-Alder (IEDDA) reaction, HSA was conjugated to 4D5scFv. Our results demonstrate successful expression and purification of 4D5scFv and its conjugation to HSA. We confirmed efficient cellular uptake of HSA in SKBR3 cells. AlbuTAC retained a high binding affinity to HER2 and induced significant HER2 degradation in HER2-positive SKBR3 cells. AlbuTAC effectively promoted endocytosis and lysosomal degradation of HER2, highlighting its potential as a novel cancer therapy. In conclusion, AlbuTAC represents a promising LYTAC platform for targeted protein degradation, advancing cancer treatment by targeting extracellular and membrane proteins overexpressed in tumor cells.