Amphiphilic Affibody-PROTAC conjugate Self-Assembled nanoagents for targeted cancer therapy

Proteolysis-targeting chimeras (PROTACs) are an emerging class of promising therapeutic molecules that can target specific disease-related proteins and then degrade them by the cellular ubiquitin–proteasome system. However, the excessive hydrophobicity and potential off-target effects of PROTACs severely limit their applications in clinics. In this work, we constructed a targeting nano-delivery system to improve the biological availability of PROTACs. A hydrophilic affibody ZEGFR:1907 (an affinity protein of epidermal growth factor receptor, EGFR) was selected to couple with a hydrophobic drug PROTAC MS28 (a cyclin D1 degrader) through a bio-responsive linker containing disulfide bond to produce an amphiphilic ZEGFR:1907-MS28 conjugate. It was able to self-assemble into a nanoagent (ZEGFR:1907-MS28 ADCN) in PBS for targeted cancer therapy. Benefiting from the extraordinary targeting performance of ZEGFR:1907, ZEGFR:1907-MS28 ADCN can be effectively accumulated in tumor sites through the EGFR-mediated endocytosis. After internalization in vitro, ZEGFR:1907-MS28 ADCN released PROTAC MS28 via the cleavage of disulfide bonds at the high level of glutathione to selectively degrade cyclin D1 and then induced apoptosis of cancer cells. After tail-vein injection in vivo, ZEGFR:1907-MS28 ADCN also exhibited significant tumor selectivity, favorable biological safety, excellent cyclin D1 degradation and good antitumor activity in EGFR-positive epidermal carcinoma tumor models. In summary, this affibody mediated nano-delivery system would provide a versatile platform for the application of PROTACs in targeted cancer therapy.