The present invention is related to neurotensin receptor antagonists of formula (I): wherein R 1 is selected from the group consisting of hydrogen, methyl and cyclopropylmethyl； AA-COOH is an amino acid selected from the group consisting of 2-amino-2-adamantane carboxylic acid, cyclohexylglycine and 9-amino-bicyclo[3.3.1]nonane-9-carboxylic acid； R 2 is selected from the group consisting of (C 1 -C 6 )alkyl, (C 3 -C 8 )cycloalkyl, (C 3 -C 8 )cycloalkylmethyl, halogen, nitro and trifluoromethyl； ALK is (C 2 -C 5 )alkylidene； R 3 , R 4 and R 5 are each and independently selected from the group consisting of hydrogen and (C 1 -C 4 )alkyl under the proviso that one of R 3 , R 4 and R 5 is of the following formula (II) wherein ALK' is (C 2 -C 5 )alkylidene； R 6 is selected from the group consisting of hydrogen and (C 1 -C 4 )alkyl； and R 7 is selected from the group comprising H, Acceptor, -[Acceptor-Effector], -[Linker-Acceptor], and -[Linker-Acceptor-Effector], wherein Acceptor is a moiety which mediates linking of an Effector to the N atom of formula (II) or which mediates linking of the Effector to the Linker, Effector is selected from the group comprising a diagnostically active agent and a therapeutically active agent, Linker is a moiety which links the Acceptor to the N atom of formula (II), -[Acceptor-Effector] is a moiety where the Effector is complexed or covalently bound to the Acceptor, -[Linker-Acceptor] is a moiety where the Linker is conjugated to the Acceptor, and -[Linker-Acceptor-Effector] is a moiety where the Linker is conjugated to the Acceptor, whereby the Effector is complexed or covalently bound to the Acceptor； or a pharmacologically acceptable salt, solvate or hydrate thereof.
