Contrast agents

1. A composition of matter of formula I

V-L-R   (I)

where V is a non-peptidic organic group having binding affinity for an angiotensin II receptor site, V being the residue of a compound of formula II

wherein R 1 and R 2 are carboxyl groups or C 1-6 alkyl groups optionally substituted by oxa, oxo, phenyl, amino, carboxyl or hydroxy groups or R 1 may additionally represent an axo group, and

R 3 and R 4 are methyl biphenyl carboxyl or methyl biphenyl tetrazole groups or C 1-6 alkyl groups optionally substituted by oxa, oxo, phenyl, amino, carboxyl or hydroxyl groups,

R 4 being present only when R 1 is oxo, and

with one of the groups R 1 , R 2 , R 3 and R 4 representing an alkyl group substituted by oxa, oxo phenyl, amino, carboxyl or hydroxyl groups, L is linker moiety or a bond, and R is a moiety detectable in in vivo imagining of a human or animal body.

2. A composition of matter as claimed in claim 1 selected from the croup consisting of:

i) a Gd chelate of a conjugate of DTPA and 4′-[3-(3-aminopropyl)-5-butyl-1H-1,2,4-triazol-1-yl)methyl][1,1′-biphenyl]-2-carboxylic acid;

ii) a Tc chelate of a DTPA conjugate of 4′-[3-(3-aminopropyl)-5-butyl-1H-1,2,4-triazol-1yl)methyl][1,1′-biphenyl]-2-carboxyl acid;

iii) 131 I-labelled 4′-[3,5-dibutyl-1H-1,2,4-triazole-1-yl)methyl][1,1′-biphenyl]-2-carboxylic acid; and

iv) a vesicle carrying a succinic acid conjugate of 4′-[3-(3-aminopropyl)-5-butyl-1H-1,2,4-trizol-1-yl)methyl][1,1′-biphenyl]-2-carboxylic acid.

3. A pharmaceutical composition comprising a composition of matter of formula I as defined in claim 1 together with at least one pharmaceutically effective carrier or excipient.

4. A method of generating an image of an animate human or non-human animal subject involving administering a contrast agent to said subject and generating an image of at least part of said subject to which said contrast agent has distributed, characterized in that contrast agent is a composition of matter of formula I as defined in claim 1 .

5. A method as claimed in claimed 4 wherein said image is a nuclear imaging image.

6. A method as claimed 5 wherein said image is an ultrasound image.

7. A method of monitoring the effect of treatment of a human or non-human animal subject with a drug to combat or provoke effects associated with angiotensin II, said method involving administering to said subject a composition of matter of formula I as defined claim 1 and detecting the uptake of said agent by angiotensin II receptors.

8. A method as defined in claim 7 wherein said administration and detection is effected repeatedly.

9. A process for the preparation of a composition of a matter of formula I as defined in claim 1 , said process comprising conjugation (i) an organic compound having binding affinity for an angiotensin II receptor to (ii) reporter compound detectable in a diagnostic imaging procedure or a chelant compound and if necessary metallating chelant groups in the resultant conjugate with a metal ion detectable in a diagnostic imaging procedure.

10. A composition of matter as claimed in claim 1 wherein R 1 is oxo and one of R 3 and R 4 representing a biphenyl containing group.