Rational Design for Nitroreductase (NTR)-Responsive Proteolysis Targeting Chimeras (PROTACs) Selectively Targeting Tumor Tissues.

The catalytic properties of proteolysis targeting chimeras (PROTACs) may lead to uncontrolled off-tissue target degradation that causes potential toxicity, limiting their clinical applications. The precise control of this technology in a tissue-selective manner can minimize the potential toxicity. Hypoxia is a hallmark of most solid tumors, accompanied by elevated levels of nitroreductase (NTR). Based on this character, we presented a type of NTR-responsive PROTACs to selectively degrade proteins of interest (POI) in tumor tissues. Compound 17-1 was the first NTR-responsive PROTAC synthesized by incorporating the caging group on the Von Hippel-Lindau (VHL) E3 ubiquitin ligase ligand. It could be activated by NTR to release the active PROTAC 17 to efficiently degrade the EGFR protein and subsequently exert antitumor efficacy. Thus, a general strategy for the precise control of PROTAC to induce POI degradation in tumor tissues by NTR was established, which provided a generalizable platform for the development of NTR-controlled PROTACs to achieve selective degradation.