Synthesis and Evaluation of AS1411-Lenalidomide-Targeted Degradation Chimera in Antitumor Therapy

Background: High expression of nucleolin (NCL) on the surface of tumor cells is closely associated with disease progression and poor prognosis. The aptamer-PROTAC conjugate (APC) technology provides a novel molecular design strategy for the targeted degradation of NCL. Methods: Based on the principles of PROTAC technology and chemical modification techniques, in this study, a series of AS1411-lenalidomide chimeras featuring different linker structures were designed and synthesized for the specific purpose of targeted degradation of NCL. Four AS1411-PROTACs (C1-C4) were successfully constructed via a click chemistry strategy, and their structures were validated. Results: In vitro experimental results showed that C4 exhibited the most optimal activity, significantly downregulating NCL expression and inhibiting the proliferation of breast cancer cells (MCF-7). Notably, the activity of C4 remained unaltered regardless of the annealing process. Mechanistic studies demonstrated that C4 induced NCL degradation through the ubiquitin-proteasome pathway while also promoting apoptosis and cell cycle arrest. In a nude mouse tumor model, C4 displayed potent antitumor efficacy, with no discernible signs of obvious systemic toxicity. Conclusions: This study provides compelling evidence demonstrating that C4 is a highly promising anticancer compound. It also provides important evidence for the development of novel nucleic acid aptamer-PROTAC conjugate drugs for more clinical applications.