Blood-brain barrier (BBB) precisely regulates substance influx and efflux to maintain brain homeostasis and function. Effective CNS targeted therapy necessitates precise cellular targeting and efficient drug delivery across the BBB, which current treatments often fail to achieve. Herein, we report a streamlined one-step macrocyclization strategy for the synthesis of phenothiazine-based macrocycles with enhanced BBB permeability. The macrocyclization process fosters synergistic supramolecular interactions within the macrocyclic cavity, thereby improving BBB permeability and enhancing cellular uptake. As a proof-of-concept, these macrocycles exhibited enhanced anti-glioblastoma (GBM) activity that not only surpassed their small-molecule counterparts but also outperformed a wide range of existing chemotherapeutics and nanomaterials. From a supramolecular perspective, the chemically driven one-step conversion of phenothiazine units into supramolecular macrocycles provides a promising framework for reengineering conventional small-molecule drugs into advanced next-generation therapeutic agents with enhanced BBB permeability and pharmacological properties.