Cyclo(-RGDfK) is a cyclic peptides and a highly effective and selective Integrin αvβ3 inhibitor with an IC50 value of 0.94 nM. It specifically binds to the αvβ3 integrin on the cell surface, blocking integrin-mediated cell adhesion, migration and signal transduction processes, thereby inhibiting tumor angiogenesis and the invasion and metastasis of tumor cells.