RP-832c is a synthetic analog of a host defense peptide (HDP) that targets the mannose receptor CD206 on M2-polarized macrophages with a Kd of 3.5 μM. Upon binding to CD206, RP-832c induces significant conformational changes in the receptor, activating signaling pathways that lead to rapid apoptosis of CD206-positive M2 macrophages and their repolarization to the M1 phenotype. Treatment with RP-832c significantly reduces CD206 gene expression in M2 macrophages and temporarily increases the expression of the M1 macrophage marker TNF-α. RP-832c is applicable for research on T-cell lymphomas (CTCL) and idiopathic pulmonary fibrosis (IPF).