<p>It is aimed at developing a method and a system for achieving drug delivery control by using a physiologically active peptide. It has been found out that an unexpected sustained release effect is achieved by adding an amino acid such as glycine to a physiologically active peptide and thus a sustained release system with the use of the amino acid addition has been established. It has been further found out that a composition containing a plural number of modified peptides of the above type has an extremely remarkable sustained release effect. Thus, it is intended to provide a peptide comprising a physiologically active peptide together with at least one amino acid not originating in this physiologically active peptide; and a composition containing at least two types of physiologically active peptide amino acid sequences wherein at least one of them contains at least one amino acid not originating in this physiologically active peptide.</p>
