Design of dendritic macromolecules containing folate or methotrexate residues

Polyether dendritic compounds bearing folate residues on their surface were prepared as model drug carriers with potential tumor cell specificity. Starting from ester-terminated polyether dendrimers, hydrazide groups were easily introduced to the surface of the dendrimers by reaction with hydrazine. Folate residues were then conjugated to the hydrazide chain ends of the dendrimers by direct condensation with folic acid in the presence of a condensing agent or by reaction with an active ester derivative of folic acid. Essentially complete functionalization of the terminal hydrazide groups was achieved for both the first and the second generation dendrimers with four and eight hydrazide groups. For the G-2 dendrimer with 16 hydrazide groups, an average number of only 12.6 folate residues were attached to each dendrimer. The conjugates are soluble in aqueous medium above pH 7.4. In addition, a similar conjugation of the antitumor drug methotrexate to the dendrimer was also investigated. Once optimized, these molecules may form the basis for a novel family of multivalent drug carriers.