Peptide-based compounds

1. 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

R 1 represents —(CH 2 ) n — or —(CH 2 ) n —C 6 H 4 — wherein

n represents a positive integer 1 to 10

h represents a positive integer 1 or 2

X 1 represents an amino acid residue wherein said amino acid possesses a functional side-chain such as an acid or amine,

X 2 and X 4 represent independently an amino acid residue capable of forming a disulfide bond,

X 3 represents arginine, N-methylarginine or an arginine mimetic,

X 5 represents a hydrophobic amino acid or derivatives thereof, and

X 6 represents a thiol-containing amino acid residue, and

X 7 is absent or represents a biomodifier moiety,

Z 1 comprises a chelating agent and/or a radionuclide reporter moiety and

W 1 is absent or represents a spacer moiety.

2. The composition of claim 1 , wherein any of the amino acid residues are independently in the D or L conformation.

3. The composition of claim 1 , wherein R 1 represents —(CH 2 )—.

4. The composition of claim 1 , wherein X 1 represents aspartic acid, glutamic acid, lysine, homolysine or a diaminoalkylic acid or derivatives thereof.

5. The composition of claim 1 , wherein X 2 , X 4 and X 6 independently represent a cysteine or homocysteine residue.

6. The composition of claim 1 , wherein X 3 represents an arginine residue.

7. The composition of claim 1 , wherein X 5 represents a tyrosine, a phenylalanine, a 3-iodo-tyrosine or a naphthylalanine residue.

8. The composition of claim 1 , wherein X 7 is absent or comprises 1-10 units of a monodisperse PEG building block.

9. The composition of claim 1 , wherein X 7 is absent or comprises 1-10 units of Formula II

10. The composition of claim 1 , wherein X 7 represent 1-10 amino acid residues.

11. The composition of claim 1 , wherein X 7 represent glycine, lysine, aspartic acid or serine residues.

12. The composition of claim 1 , where Z 1 comprises a chelating agent of Formula III

where:

each R 1 , R 2 , R 3 and R 4 is independently an R group;

each R group is independently H or C 1-10 alkyl, C 3-10 alkylaryl, C 2-10 alkoxyalkyl, C 1-10 hydroxyalkyl, C 1-10 alkylamine, C 1-10 fluoroalkyl, or 2 or more R groups, together with the atoms to which they are attached form a carbocyclic, heterocyclic, saturated or unsaturated ring.

13. The composition of claim 1 , where Z 1 comprises a chelating agent of formula:

14. The composition of claim 1 , wherein Z 1 comprises a radionuclide reporter moiety, wherein when said radionuclide is a radiometal, said radiometal is chelated by the chelating agent of Z 1 .

15. The composition of claim 14 , wherein the reporter moiety comprises 90 Y, 99m Tc, 111 In, 47 Sc, 67 Ga, 51 Cr, 177m Sn, 67 Cu, 167 Tm, 97 Ru, 188 Re, 177 Lu, 199 Au, 203 Pb, 141 Ce or 18 F.

16. The composition of claim 15 , wherein the radionuclide reporter moiety is 99m Tc.

17. The composition of claim 1 , where W 1 is glutaric or succinic acid.

18. The composition of claim 1 , wherein the compound of Formula (I) is defined by the following formulae:

19. A method of generating images of a human or animal body involving administering a contrast agent to said body, and generating an image of at least a part of said body to which said contrast agent has distributed, wherein said contrast agent comprises the composition of claim 14 .

20. The method of claim 19 , which is carried out to monitor the effect of treatment of a human or animal body with a drug to combat a condition associated with cancer, wherein said administration and image generation are optionally but preferably being effected repeatedly, e.g. before, during and after treatment with said drug.