Targeted Degradation of eEF2K by a Structure‐Guided PROTAC Strategy for the Treatment of Triple‐Negative Breast Cancer

ABSTRACT Proteolysis‐targeting chimera (PROTAC) have emerged as a promising class of anticancer agents. Eukaryotic elongation factor 2 kinase (eEF2K), a stress‐responsive regulator of translational elongation, has emerged as a pivotal therapeutic target in triple‐negative breast cancer (TNBC) due to its critical role in sustaining cancer cell survival under nutrient stress. Building on our previous work identifying eEF2K as an oncogenic kinase, this study developed an eEF2K‐targeting PROTAC that exhibited potent antitumor activity against TNBC. Through a structure‐guided design, we identified a key allosteric pocket of eEF2K and linked its inhibitor 2S to a CRBN ligand to generate A6, a PROTAC that promotes eEF2K degradation via a conformationally optimized interface, achieving >90% target depletion while preserving the total levels of its substrate eEF2. A6 exhibited anti‐proliferative effects across TNBC cell lines by degrading eEF2K. In Vivo and in TNBC organoid models, A6 treatment significantly suppressed tumor growth, with favorable tolerability. To further enhance tumor‐specific delivery, we engineered A6@ZIF‐8, a pH‐sensitive nanocarrier that promotes drug accumulation at tumor sites compared to free A6, leading to improved therapeutic outcomes. Collectively, our data indicate that targeted degradation of eEF2K via PROTAC technology constitutes a novel and therapeutically relevant intervention strategy for TNBC.