Self-Assembled Molecular Glue Prodrug System for Enhanced Synergistic Tumor Therapy by Combining CDK12 Protein Degradation and Immunotherapy

Molecular glue degraders have recently emerged as a promising strategy for targeting proteins previously considered undruggable. Among these, CR8 has demonstrated potent anticancer efficacy <i>in vitro</i> by effectively degrading cyclin-dependent kinase 12 and cyclin K. However, its clinical application is restricted by nonspecific toxicity to normal cells and tissues. To address this limitation, we developed a prodrug of CR8, termed pCR8, which selectively releases CR8 at tumor sites through boronate oxidation mediated by elevated H₂O₂ levels in the tumor microenvironment. Moreover, the amphiphilic prodrug can self-assemble to form nanoparticles. <i>In vitro</i> experiments showed that pCR8 exhibits lower cytotoxicity and responds effectively to H₂O₂, resulting in the release of CR8, which inhibits 4T1 cells and effectively degrades cell cycle-related proteins. Additionally, the therapeutic efficacy of pCR8 was corroborated in 4T1 tumor-bearing mice through tail vein injection, revealing its tumor-suppressive activity associated with CD8⁺ T cell activation and a synergistic effect when combined with immune checkpoint inhibitors, while also showing improved safety compared with CR8. Our findings suggest that pCR8 not only offers a promising strategy for reducing the side effects of CR8 but also introduces an effective combination therapy approach for the treatment of triple-negative breast cancer.