Giant heterometallic polyoxometalate (POM) clusters with precise atom structures, flexibly adjustable and abundant active sites are promising for constructing functional nanodrugs. However, current POM drugs are almost vacant in orthotopic brain tumor therapy due to the inability to effectively penetrate the blood-brain barrier (BBB) and low drug activity. Here, we designed the largest (3.0 nm × 6.0 nm) transition-metal-lanthanide co-encapsulated POM cluster {[Ce