Certepetide is a cyclic peptide that enhances delivery of coadministered anticancer drugs and modulates the tumor microenvironment. It binds αvβ3/5-integrins on tumor endothelium, undergoes proteolytic cleavage, and the resulting fragment binds neuropilin-1, triggering active tumor-specific drug transport. It also depletes immunosuppressive T cells, enhances cytotoxic T cells, and inhibits metastasis.