The present invention provides new prodrugs which are conjugates of a therapeutic compound and a peptide wherein the conjugate is cleavable by dipeptidyl-peptidases, more preferably by CD26, also known as DPPIV (dipeptidyl aminodipeptidase IV). The present prodrugs have the formula the stereoisomeric forms and salts thereof, wherein n is 1 to 5; Y is proline, alanine, hydroxyproline, dihydroxyproline, thiazolidinecarboxylic acid (thioproline), dehydroproline, pipecolic acid (L-homoproline), azetidinecarboxylic acid, aziridinecarboxylic acid, glycine, serine, valine, leucine, isoleucine and threonine; X is selected from any amino acid in the D- or L-configuration; X and Y in each repeat of [Y-X] are chosen independently from one another and independently from other repeats; Z is a direct bond or a bivalent straight or branched saturated hydrocarbon group having from 1 to 4 carbon atoms; R1 is an aryl, heteroaryl, aryloxy, heteroaryloxy, aryloxyC1-4alkyl, heterocycloalkyloxy, heterocycloalkylC1-4alkyloxy, heteroaryloxyC1-4alkyl, heteroarylC1-4alkyloxy; R2 is arylC1-4alkyl; R3 is C1-10alkyl, C2-6alkenyl or C3-7cycloalkylC1-4alkyl; R4 is hydrogen or C1-4alkyl. The present invention furthermore provides the use of said prodrugs as medicines as well as a method of producing said prodrugs.