A sterile pharmaceutically acceptable aqueous solution, which solution is provided in a sealed container and comprises: a pharmaceutically acceptable aqueous solvent; viral particles or a physiologically active polypeptide; an excipient selected from a polyethyleneimine; a compound of formula (I) or a physiologically acceptable salt or ester thereof; or a compound of formula (II) or a physiologically acceptable salt or ester thereof; and optionally, one or more sugars.