Lysosome Targeting Chimeras (LYTACs) That Engage a Liver-Specific Asialoglycoprotein Receptor for Targeted Protein Degradation
Selective protein degradation platforms have afforded new development opportunities for therapeutics and tools for biological inquiry. The first lysosome targeting chimeras (LYTACs) targeted extracellular and membrane proteins for degradation by bridging a target protein to an endogenous lysosome targeting receptor, the cation-independent mannose-6-phosphate receptor (CI-M6PR). Here we developed LYTACs that engage the asialoglycoprotein receptor (ASGPR), a liver-specific lysosomal targeting receptor, to degrade membrane proteins in a tissue-specific manner. We conjugated antibody-based binders targeting cell-surface proteins to a tri-GalNAc motif that engages ASGPR. The resulting LYTACs directed lysosome trafficking of the bound targets and subsequent degradation. Degradation mediated by an EGFR-targeted GalNAc-LYTAC resulted in significant functional effects on the downstream kinase signaling of EGFR compared to canonical inhibition with a monoclonal antibody. Furthermore, we demonstrated that a small target binder, a 3.4 kDa peptide, can be linked to a single tri-GalNAc ligand to degrade integrins and significantly reduce cell proliferation. Site-specific chemical conjugation of one or two tri-GalNAc ligands to antibody scaffolds improved the pharmacokinetic profile of GalNAc-LYTACs in vivo compared to non-specific chemical conjugation. GalNAc-LYTACs represent an exciting new paradigm for cell-type restricted degradation of proteins.