The present invention relates to cytostatics which have a tumour-specific action as a result of linkage to α
v
β
3
integrin antagonists via preferred linking units. The preferred linking units guarantee serum stability of the conjugate of cytostatic and α
v
β
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.