The present invention describes a new group of bioconjugates which can be obtained by means of indirect synthesis, via a molecular spacer, between hyaluronic acid and/or its derivatives and drugs with an antitumoral activity belonging to different groups, their preparation process and use in the oncological field. The new derivatives, in relation to the type of bond and Substitution degree, have different physico-chemical properties which improve their tolerability and efficiency and allow a more accurate modulation of the dosage, exploiting an active targeting mechanism.