ICAM‐1‐Expressing Extracellular Vesicles Enable Sequential Delivery Barrier‐Breaking and Microenvironment Modulating for Glioblastoma Stem Cell Inhibition

Abstract Glioma stem‐like cell (GSC) inhibition is a promising strategy for glioblastoma therapy. However, it is hampered by two main obstacles: first, delivery barriers, including the blood–brain barrier (BBB) and deep tumor‐penetrating obstacles, hinder sufficient drug accumulation in GSCs that often reside in hypoxic niches deep in glioblastoma; second, hypoxia and the immunosuppressive tumor microenvironment (TME) limit the therapeutic responses of GSC inhibition strategies. An intercellular cell adhesion molecule 1 (ICAM‐1)‐expressing M1 macrophage‐derived small extracellular vesicles loaded with a complex of bovine serum albumin, MnO 2 , and the small‐molecule inhibitor PTC209 (IsEV‐BMP) is constructed to achieve sequential barrier‐breaking delivery and simultaneous TME modulation to boost GSC inhibition. ICAM‐1 facilitates endothelial transcytosis‐mediated BBB crossing, microglial transcytosis‐mediated deep tumor penetration, and internalization of IsEV‐BMPs in GSCs. Hypoxia alleviation inhibits the binding of hypoxia‐inducible factor 1α (HIF‐1α) to hypoxia‐responsive elements on the gene promoters of cancer stem cell‐related markers and CD47 in GSCs, thereby improving PTC209 sensitivity and immune phagocytosis of GSCs. IsEV‐BMP achieves simultaneous microglial polarity transition and immuno‐microenvironmental modulation during microglial transcytosis‐mediated deep tumor penetration. This study provides a strategy to overcome the sequential delivery barrier for effective glioblastoma treatment.