A composition in the form of an injectable aqueous solution, wherein the pH is comprised from 6.0 to 8.0, includes at least:a) amylin, an amylin receptor agonist or an amylin analog; andb) a co-polyamino acid bearing carboxylate charges and hydrophobic radicals Hy, wherein the composition does not comprise a basal insulin wherein the isoelectric point pI is comprised from 5.8 to 8.5. The composition may further include a prandial insulin.