The role of pro- and anti-inflammatory macrophages in disease depends on the specific disease and the balance between the two types of macrophages. Imbalances can lead to the development or progression of diseases, and targeting macrophage function may be a potential therapeutic approach for certain diseases. For example, by altering the phenotype and function of TAMM2, it is possible to shift the immune response from an anti-inflammatory to a proinflammatory state, which may help reduce tumor progression. Here, the inventors demonstrate the ability of Gilteritinib to reprogram primary human macrophages. Gilteritinib is a targeted therapy used in the treatment of acute myeloid leukemia (AML) with a specific genetic mutation called FLT3-internal tandem duplication (FLT3-ITD) or a tyrosine kinase domain (TKD) mutation. Accordingly, the present invention relates to a FLT3 inhibitor for use in the polarization of macrophages.