STAT3 and brain neoplasm: Single-cell RNA sequencing analysis of PBMCs demonstrated increased CD4+ and CD8+ T cells, proinflammatory TNFA signaling, differentiation activity in myeloid cells, and downregulation of Tregs after WP1066 treatment, consistent with systemically inhibited STAT3 activity.CONCLUSIONWP1066 is safe, has minimal toxicity, and induces antitumor immune responses in pediatric brain tumor patients.