Lysosome-Targeting Chimera Using Mannose-6-Phosphate Glycans Derived from Glyco-Engineered Yeast

Lysosome-targeting chimeras (LYTACs) harness the cell's lysosomal degradation machinery to break down extracellular and membrane proteins. Previous methods used a synthetic glycopeptide containing multiple serine-O-mannose-6-phosphate (poly-M6Pn), which presented challenges such as synthetic complexity and potential immunogenicity associated with poly-M6Pn. This study introduced a LYTAC formulation, LYTAC^gyM6pG, which uses glyco-engineered yeast-derived mannose-6-phosphate glycans (gyM6pGs) for lysosomal transport, overcoming synthetic complexities and immunogenic risks. The gyM6pGs used in LYTAC^gyM6pG are human-compatible (identical to the structures found in humans) and are efficiently produced through yeast fermentation, followed by the preparation of cell wall glycans and their <i>in vitro</i> modifications. We employed copper-free click chemistry (azide and dibenzocyclooctyne reactions) for the robust conjugation of gyM6pGs to a nanobody targeting the immune checkpoint protein PD-L1, thereby streamlining the assembly of LYTAC^gyM6pG. We demonstrated that LYTAC^gyM6pG effectively degraded endogenous and recombinant PD-L1 proteins on the cell surface by directing them to the lysosome via the cation-independent mannose-6-phosphate receptor pathway. Furthermore, LYTAC^gyM6pG significantly enhanced T cell-mediated cytotoxicity against cancer cells, surpassing the efficacy of nanobodies alone. The successful application of gyM6pGs in the development of LYTAC^gyM6pG highlights the potential for a more viable and scalable therapeutic production of LYTACs, paving the way for broader therapeutic applications, including cancer treatment.