Peptide-based compounds

A pharmaceutical composition comprising an effective amount of a compound of formula (I) or a pharmaceutically acceptable salt thereof, together with one or more pharmaceutically acceptable adjuvants, excipients or diluents:

• wherein:
• G represents glycine
• D represents aspartic acid
• R1 represents —(CH2)n— or —(CH2)n—C6H4— wherein
• n represents a positive integer 1 to 10
• h represents a positive integer 1 or 2
• X1 represents an amino acid residue wherein said amino acid possesses a functional side-chain such as an acid or amine,
• X2 and X4 represent independently an amino acid residue capable of forming a disulfide bond,
• X3 represents arginine, N-methylarginine or an arginine mimetic,
• X5 represents a hydrophobic amino acid or derivatives thereof, and
• X6 represents a thiol-containing amino acid residue, and
• X7 is absent or represents a biomodifier moiety,
• Z1 comprises a chelating agent and/or a radionuclide reporter moiety and
• W1 is absent or represents a spacer moiety.