CSF1R inhibitor C19 for glioma immunotherapy enabled by brain-targeting liposomal delivery

Immunotherapy targeting tumor-associated macrophages (TAMs) has emerged as a promising approach for treating glioma, driven by advances in drug discovery and development, including colony-stimulating factor 1 receptor (CSF1R) inhibitors. We previously developed a CSF1R inhibitor, C19, for TAM-targeting immunotherapy, which can reprogram TAMs and remodel the tumor immunosuppressive microenvironment. However, the application of CSF1R inhibitors in brain cancer is limited due to inefficient delivery across the blood-brain barrier (BBB). To address this limitation, we designed a brain-targeted liposomal delivery system (T12-Lipo) modified with the transferrin receptor-binding peptide T12. T12-Lipo can specifically bind to transferrin receptors, which are overexpressed in both the BBB and TAMs, thus enhancing the delivery efficiency of C19 across the BBB and to TAMs. This system promoted TAM repolarization toward an anti-tumor M1-like phenotype and thereby facilitated T-cell-mediated tumor killing. T12-Lipo improved the BBB permeability of C19, exhibiting significant therapeutic efficacy against glioma growth. The brain-targeted liposomal formulation of the CSF1R inhibitor C19 represents a promising and effective approach for glioma immunotherapy. T12 peptide-modified liposomes loaded with CSF1R inhibitor C19 can penetrate the BBB, promote M1 phenotypic differentiation of macrophages, effectively activate T-cell immunity, alleviate the tumor immunosuppressive microenvironment, and improve the therapeutic efficacy against glioma.