The present invention relates to cytostatics which have a tumour-specific action as a result of linkage to .alpha..sub.v.beta..sub.3 integrin antagonists via preferred linking units. The preferred linking units guarantee serum stability of the conjugate of cytostatic and .alpha..sub.v.beta..sub.3 integrin antagonist and at the same time the desired intracellular action in tumour cells as a result of their enzymatic or hydrolytic cleavability with release of the cytostatic.
