Pharmacologically active peptide conjugates having a reduced tendency towards enzymatic hydrolysis

A pharmacologically active peptide conjugate having a reduced tendency towards enzymatic cleavage comprising X and Z,

• wherein X is a pharmacologically active peptide sequence selected from the group consisting of adrenocorticotropic hormone (ACTH), melanotan II, melanocyte stimulating hormone (MSH), and alpha-MSH, and
• wherein Z is a peptide sequence of 4-15 amino acid units covalently bound to X via a peptide bond to the C-terminal carbonyl function of X and/or to the N-terminal nitrogen atom of X, and wherein Z consists of residues selected from Glu, Lys, and Met, and
• wherein the ratio between the half-life of said peptide conjugate and the half-life of the corresponding pharmacologically active peptide sequence X, when treated with carboxypeptidase A or leucine aminopeptidase in about 50 mM phosphate buffer solution at about pH 7.4 at about 37° C. or in serum or plasma is at least about 2, or wherein said peptide conjugate has a half-life in human or mice serum or plasma at 37° C. of at least about 10 minutes.