FLT1 and neoplasm: Additionally, small-molecule tyrosine kinase inhibitors, such as lenvatinib, improve the tumor microenvironment by targeting VEGFR1–3 and fibroblast growth factor receptor 1 (FGFR1), while regulating colony-stimulating factor 1 receptor (CSF1R) to reduce M2-type macrophage infiltration and suppress regulatory T cells (Tregs) (34).