Lysosomal Trafficking and Degradation of Extracellular Proteins via Multivalent Small Molecule Ligand Display on Dextran Scaffolds.

Targeted protein degradation (TPD) marks a shift in drug development from conventional inhibition to the complete removal of pathological proteins. Traditional TPD technologies target intracellular proteins of interest (POIs) for degradation but are ineffective against extracellular cell surface and soluble proteins, a significant portion of the human proteome. Recent advances involve the formation of ternary complexes between a POI and a cell surface lysosomal trafficking receptor, directing POIs to lysosomes for degradation. We report on DEXtran TRAfficking Chimeras (DEXTRACs) comprising multiple copies of synthetic small molecule ligands for a model POI and the cation-independent mannose-6-phosphate receptor (CI-M6PR) lysosomal trafficking receptor. These ligands are arranged along the dextran backbones. We demonstrate that DEXTRACs leverage multivalency with their efficacy dependent on the dextran chain length and ligand density to form high-avidity ternary complexes. Our in vitro studies confirmed that DEXTRACs traffic the target POI to lysosomes and facilitate its degradation.