An injectable aqueous solution, of which the pH is from 6.0 to 8.0, comprising at least: a) amylin, an amylin receptor agonist or an amylin analog b) a co-polyamino acid bearing carboxylate charges and hydrophobic radicals Hy, said co-polyamino acid consisting of glutamic or aspartic units and said hydrophobic radicals Hy having the following formula I:GpRrGpAaGpC)p Iwherein the composition does not comprise a basal insulin of which the isoelectric point pI is from 5.8 to 8.5. It also relates to a composition wherein it moreover comprises a prandial insulin.