Chemical-pharmaceutical conjugates of hyaluronic acid and / or its derivatives obtained through an indirect bond between the polysaccharide and a drug with an antitumor action, through a molecular spacer that forms an ester bond with the carboxylic group of HA and / or its derivative, with the proviso that said spacer is not a hydrazide or a polypeptide, the drug being selected from antimetabolites, the degree of substitution in the carboxyl of hyaluronic acid and / or one of its derivatives varying between 1 and 20%； said hyaluronic acid derivatives being selected from - HA salified with organic and / or inorganic bases having a molecular weight of 50-730 KDa or a high molecular weight of 750-1230 KDa； - HA esters with aliphatic, araliphatic, cycloaliphatic, aromatic, cyclic and heterocyclic series alcohols, with an esterification percentage that varies depending on the type and length of the alcohol used, from 1 to 75%； - HA amides with aliphatic, araliphatic, cycloaliphatic, aromatic, cyclic and heterocyclic series amines, with an amidation percentage ranging from 1 to 10%； - O-sulfated derivatives of HA up to the 4th degree of sulphation； - internal esters of HA with a percentage of internal esterification ranging from 0.5 to 10% and preferably 5%； - HA deacetylates derived from the deacetylation of the N-acetyl-glucosamine fraction with a percentage of deacetylation preferably varying from 0.1 to 30%； - percarboxylated derivatives of HA obtained from the oxidation of the primary hydroxyl of the N-acetylglucosamine fraction with a degree of percarboxylation ranging from 0.1 to 100%.Conjugados químico-farmacéuticos de ácido hialurónico y/o sus derivados obtenidos a través de un enlazamiento indirecto entre el polisacárido y un fármaco con una acción antitumoral, a través de un espaciador molecular que forma un enlace éster con el grupo carboxílico de HA y/o su derivado, con la condición de que dicho espaciador no es una hidrazida o un polipéptido, siendo el fárma
