Abstract: The present invention relates to cytostatics which have a tumor-specific action as a result of linkage to ?v?3 integrin antagonists via preferred linking units which can be selectively cleaved by elastase, i.e. by an enzyme which can especially be found in tumor tissue. The preferred linking units provide sufficient stability of the conjugate of cytostatic and ?v?3 integrin antagonist in biological fluids and, at the same time, the desired intracellular action within tumor cells as a result of its specific enzymatic or hydrolytic cleavability with release of the cytostatic.