The present invention, among others, relates to a compound having a structure according to formula (I) or a pharmaceutically acceptable salt thereof, wherein Xaa1 are the iodo-substituted or methyl-substituted amino acids D- and L-Tyr, iodo-substituted or methyl- substituted D- and L-homotyrosine, iodo-substituted or methyl-substituted D- and L-Phe, iodo-substituted or methyl-substituted D- and L-p-OH-phenylglycine, and iodo-substituted or methyl-substituted D- or L-Trp, Xaa2 to Xaa4 are independently of each other, an optionally N-alkylated natural or unnatural amino acid, R is H or methyl, L is a linker moiety, Ar is a spacer comprising an aromatic moiety, and D comprises, preferably is i) a combination of an organic complexation agent and a radioactive or a detectable label； or ii) a radioactive or a detectable label, an organic complexation agent or an active substance, said active substance particularly being selected from cytotoxic agents, lipids, sugars, sugar conjugates, sugar derivatives, proteins and combinations thereof.
