Sheddase Targeting Chimeras (SHEDTACs) catalyze membrane target proteolysis

Extracellular targeted protein degradation (eTPD) has expanded access to the "undruggable" proteome but is constrained by aspects of receptor-mediated endocytosis and intracellular trafficking. This study describes Sheddase-Targeting Chimeras (SHEDTACs), bispecific antibodies that commandeer endogenous membrane metalloproteases (sheddases) to catalyze direct proteolysis of cell surface targets in cis. SHEDTACs bypass internalization requirements through enforced proximity between sheddases and substrates, enabling rapid proteolysis directly at the cell surface. Induced proximity between the immune checkpoint LAG3 and metalloprotease ADAM10 afforded nearly quantitative receptor depletion from primary human T cells. LAG3 shedding was rapid and unaffected by pharmacologic perturbation of proteasomal or lysosomal pathways, consistent with cell surface proteolysis. In a luminescent T cell reporter co-culture, SHEDTACs catalyzed LAG3 removal and enhanced T cell receptor signaling beyond conventional blocking antibodies, addressing resistance mechanisms in cancer immunotherapy. Notably, SHEDTACs depleted the non-canonical sheddase substrate, PD-1, demonstrating this approach can be expanded beyond natural protease-target pairs. SHEDTACs establish a mechanistically orthogonal eTPD platform that exploits cell surface proteolysis, offering programmable control over the cell surface proteome with broad therapeutic implications.