The present invention relates to the use of a polyvalent synthetic compound comprising a support on which at least 3 pseudopeptide units are grafted, said compound being of formula (I), in which each X independently represents any amino acid； Y1 and Y2 are selected independently from amino acids having a basic side chain； Z is selected from a proline, optionally substituted at .noteq., - or ..； a natural or non-natural N-alkylamino acid； a dialkylamino acid； a cyclic dialkylamino acid； pipecolic acid or a derivative thereof； n and i independently are 0 or 1； m is an integer between 0 and 3； k is an integer greater than or equal to 3； and .PSI. represents a modified peptide bond which is significantly more resistant to at least one protease than a standard peptide bond, for preparing a medicament intended for treating a disease involving deregulation of cell proliferation and/or of angiogenesis, and preferably acting as a surface nucleolin ligand, or for treating inflammatory diseases.
