CSF1R-IN-22 (Compound C19) is an orally effective CSF-1R selective inhibitor ( IC 50 <6 nM). CSF1R-IN-22 enhances the secretion of CXCL9 from M2 macrophages, increases CD8 + T cell infiltration. CSF1R-IN-22 boosts anti-tumor immune responses of anti-PD-1, and induces apoptosis in tumor cells. CSF1R-IN-22 can effectively reprogram M2-like TAMs (tumor-associated macrophages) to the M1 phenotype and reshape the TME by inducing the recruitment of CD8 + T cells into tumors and reducing the infiltration of immunosuppressive Tregs and MDSCs.