In Situ PROTAC Synthesis Enabled by Pathologically Activated Bioorthogonal Catalysis for Precision Cancer Therapy

Proteolysis-targeting chimeras (PROTACs) have transformed therapeutic interventions by hijacking the ubiquitin-proteasome system. However, their broad application is hindered by inadequate cellular permeability and undesired off-tissue effects. Here, we introduce a modular strategy for the in situ synthesis of PROTACs through pathologically activated bioorthogonal catalysis (ABC-PROTAC), enabling targeted protein degradation specifically in cancer cells. This platform integrates biocompatible, glutathione-activated Click-T-Cu(II) complexes with azido- and acetylene-derived, fragmented PROTAC precursors. These components are encapsulated within AS1411 aptamer-conjugated liposomes to enhance cellular uptake and systemic delivery. Once internalized by nucleolin-overexpressing cancer cells, the Click-T-Cu(II) complexes are activated to catalyze the intracellular assembly of functional PROTACs via click chemistry. This delivery paradigm facilitates efficient degradation of oncoproteins both in vitro and in vivo, resulting in robust antitumor activity with favorable biocompatibility and high selectivity. The modularity of the ABC-PROTAC strategy is demonstrated by utilizing diverse warheads, including small molecules and DNA motifs, to degrade BRD4, PARP1, and NF-κB. Together, this strategy establishes a precise method for targeted protein degradation while minimizing the systemic toxicity associated with conventional PROTACs.