The present invention relates to hydroxyalkyl starch (HAS) conjugates and to a method for preparing the hydroxyalkyl starch (HAS) conjugates, the hydroxyalkyl starch (HAS) conjugates comprising a hydroxyalkyl starch derivative and a cytotoxic agent, said conjugate having a structure according the following formula HAS(-M)n wherein M is a residue of a cytotoxic agent, the cytotoxic agent comprising a carbonyl group, HAS is a residue of the hydroxyalkyl starch derivative comprising at least one functional group X, n is greater than or equal to 1, and wherein the cytotoxic agent is linked via the carbonyl function present in the cytotoxic agent to the functional group X comprised in the hydroxyalkyl starch derivative, wherein the linkage via the carbonyl function is a cleavable linkage, which is capable of being cleaved in vivo so as to release the cytotoxic agent.
