An aqueous system comprising a protein and two or more stabilising agents, characterised in that (i) the two or more stabilising agents have ionisable groups capable of exchanging protons with the protein and with the ionised products of water dissociation； (ii) wherein a first stabilising agent has first ionisable groups that are positively charged when protonated and uncharged when deprotonated, and a second stabilising agent has second ionisable groups that are uncharged when protonated and negatively charged when deprotonated, wherein the first and second ionisable groups have pKa values respectively 1 to 5 units higher and 1 to 5 units lower than the pH of the composition, and wherein the first stabilising agent is an amine other than an amino acid； and (iii) the pH of the composition is within a range of protein stability that is at least 50% of the maximum stability of the protein with respect to pH.
