The invention relates to metal complex compounds, contrast agents for MRI and in vivo NMR markers for NMR spectroscopy comprising said metal complex compounds and methods for in vivo determination of physiological parameters, e.g. enzyme activity using said metal complex compounds.

Several in vivo methods, both imaging techniques and non-imaging techniques, can be used in the diagnosis of disease. MRI (magnetic resonance imaging) is a frequently used in vivo imaging technique for the diagnosis of diseases. It is based on the interaction between radio waves and body tissue water protons in a magnetic field. In order to improve the image contrast in soft tissue examinations, contrast agents are commonly used in MRI.

Beside employing contrast agent aided MRI as a tool for diagnosis based on morphology and/or anatomy, several attempts have been made to use said technique for the measurement and the quantification of physiological parameters in order to detect abnormal changes of said physiological changes and enable diagnosis, especially early-stage diagnosis, based on said changes.

US 5,707,605 , US 5,980,862 , WO-A-96/38184 and WO-A-99/25389 disclose MRI contrast agents comprising a complex consisting of a paramagnetic metal ion and a chelator, the complex comprising a moiety covalently attached to said chelator which occupies a coordination site of the paramagnetic metal ion. Said moiety is removed upon reaction with an enzyme and the change of relaxivity is determined. A drawback of the disclosed contrast agents is that the change in relaxivity caused by the enzymatic transformation is relatively small. Inherent differences in concentration may overrule the effect of relaxation changes caused by enzymatic transformation.

Moats et al., Angew. Chem. Int. Ed. Engl. 1997, 36, 726-728 describe a MRI contrast agent comprising gadolinium and galactopyranose which is a substrate for the enzyme &bgr;-galactosidase. The enzyme activated cleavage of the galactopyranose moiety and the change of coordination number of gadolinium results only in a small change in relaxivity. When relaxivity changes are of this magnitude, the local concentration of contrast agent in normal tissue and pathological tissue has to be the same (or has to be quantified) to obtain reliable diagnostic results based on differences in enzyme activity.

As ¹⁹F is a nucleus that is detectable by magnetic resonance (NMR) spectroscopy, fluorinated compounds can be used as contrast agents in MRI and as in vivo NMR markers in NMR spectroscopy. ¹⁹F is an NMR-active isotope with spin S which provides about 83% of the NMR sensitivity of protons. One of the main differences between protons and fluorine in the human or non-human animal body is that fluorine exists only in very low concentrations, predominantly immobilized in the bone matrix. Therefore, no signal background interferes during in vivo investigation of ¹⁹F-NMR or ¹⁹F-MRI.

In US 5,536,491 ¹⁹F-MRI contrast media are described comprising a metal complex compound in which a macro-cyclic polyamine ligand containing fluorine atoms is coordinate-bonded to a paramagnetic metal ion. Said contrast media can be chemically modified to impart tissue specificity (e.g. by forming composites with a tissue specific substance having a specific affinity for a particular tissue) or to detect changes in tissue environment, such as pH or oxygen concentration by determination of change of fluorine chemical shift of the contrast medium. As a drawback, the fluorine atom(s) and the paramagnetic metal atom in the compounds disclosed in US 5,536,491 are too far away from each other and the change in fluorine chemical shift upon change in pH is not enhanced by the influence of the paramagnetic metal ion. As a consequence, change in fluorine chemical shift is relatively low and minor pH changes can not be monitored.

In US 5,690,909 , fluorine containing macrocyclic metal complexes that consist of a complexing agent and a paramagnetic metal ion are described. Said complexes can be used as temperature sensors in NMR diagnosis by determining fluorine chemical shift. As the changes in fluorine chemical shift of these complexes are intramolecular in origin and independent of outside influences such as ionic strength, oxygen pressure or pH, said compounds can not be used to detect changes in ionic strength, oxygen pressure or pH.

However, there is still a need for contrast agents that can enable diagnosis in an early stage with good reliability. Useful markers for early stage diagnosis in vivo are physiological parameters such as enzyme activity, pH or the presence / concentration of free radicals. Abnormal enzyme activity of specific enzymes is often observed in cancer or cancer-related diseases, cardiovascular diseases, diseases of the central nervous system and in inflammations and infections. Enzyme activity is usually increased in the diseased area compared to other areas, but may also be decreased in the diseased area. In tumours increased enzyme activity may usually be assumed to result from overexpression of specific genes. Abnormal pH values are associated to several severe diseases. The pH value is usually reduced during cancer diseases, cardiovascular diseases like for example stroke, osteoporosis, inflammation and certain autoimmune diseases. Free radicals are known to be generated in ischemia upon reperfusion. They propagate complications because of oxidative tissue damage, as described by H. J. Freisleben, Clinical Hemorheology and Microcirculation, (2000) 23 (2-4) 219-24 . Determination of abnormal physiological parameters and identification of tissue or cells showing abnormal physiological parameters using non-invasive MRI would therefore be a favorable method in early stage diagnosis.

We have now surprisingly found that certain metal complex compounds comprising a paramagnetic metal ion and a chelate, wherein said chelate comprises at least one fluorine atom, can be used to monitor and determine physiological parameters by determining the change in fluorine chemical shift which occurs upon influence of said physiological parameters on the metal complex compounds. It has been found that when the fluorine atom is within certain proximity of the paramagnetic metal atom, physiologic parameters like enzyme activity effect a change in the chemical shift of said fluorine atom. The metal complex compounds can be used as MRI contrast agents or NMR markers for monitoring or detecting physiological parameters, especially abnormal physiological parameters in vivo.

The present invention provides metal complex compounds comprising a paramagnetic chelate comprising a paramagnetic metal ion M and a chelating agent, said chelating agent is a chelating agent according to formula (I) which comprises at least one fluorine atom and a molecular moiety X, wherein the coordination distance between X and M changes upon influence of certain enzymatic activity and thereby changing the chemical shift of the at least one fluorine atom.

The term "paramagnetic chelate" as used herein refers to a metal complex containing a paramagnetic metal ion and at least one chelating agent.

The term "chelating agent" as used herein refers to chemical compounds that bind to metal atoms, rendering them less likely to bind to other compounds, particularly biological compounds and/or rendering them less toxic.

The metal complex compounds according to the invention comprise preferably a paramagnetic metal ion M selected from the group consisting of divalent and trivalent ions of an element of atomic number 21 to 29, 42, 44 and 57 to 83. Particularly preferred paramagnetic metal ions are La³⁺, Pr³⁺, Tm³⁺, Dy³⁺ Eu³⁺ and Mn²⁺. Especially particularly preferred paramagnetic metal ions M are La³⁺, Pr³⁺, T_m ³⁺, Dy³⁺ Eu³⁺.

The chelating agent present in the metal complex compounds according to the invention is a chelating agent of formula (I). The chelating agent can be an acyclic, cyclic or macrocyclic chelating agent. Compounds which could be used as chelating agents for the present invention are described in Watson, A.D., Rocklage, S. M. and Carvlin, M. J.: Contrast agents in Stark, D. D. and Bradley, W. G. (Eds.): Magnetic resonance imaging. Volume One. Mosby Year Book. St. Louis (1992) 372-437.

The chelating agent is a chelating agent according to formula (I) wherein

R¹

represents hydrogen or C₁-C₁₅-alkyl which may optionally be substituted with one or more hydroxy groups,

A and B

are the same or different and represent CHR¹R², wherein

R¹ is of the definition as described above and

R² represents hydrogen, C₁-C₂₀-alkyl, C₆-C₂₀-aryl, C₆-C₂₀-aralkyl, said residues may optionally be substituted with one or more hydroxy groups, or

A and B form together a bridge (CH₂)_m,

Z

represents NH₂, NHR², OH, O^- or OR³, wherein R³ is a base equivalent or a metal ion equivalent,

X

represents a molecular moiety whose coordination distance to the paramagnetic metal ion chelated by the chelating agent of formula (I) changes upon influence of enzymatic activity, being selected from the group of:

• alkyl-O-PO₃ ^2- or aryl-O-PO₃ ^2- which are substrates for phosphatases,
• alkyl-(NH)-(Glu)n which is a substrate for aminopeptidase A,
• 4-alkyl-(C₆R¹R²R³R⁴)NH-aminoacid-NH₂ wherein R¹-R⁴ are hydrogen or F, Cl or NO2, which is a substrate for aminopeptidase
• 4-alkyl-(C₆H₄)-CO-aminoacid-CO₂H which is a substrate for carboxypeptidase,
• 4-alkyl-(C₆H₄)-CH₂-NH₃ ⁺ which is a substrate for monoamine oxidase, and
• 1-alkyl-&bgr;-O-glucoronic acid which is a substrate for &bgr;-glucoronidase,

Y

represents a fluorine atom or a hydrocarbon group comprising at least one fluorine atom,

D

represents a saturated or unsaturated straight or branched-chain hydrocarbon group containing 1 to 4 carbon atoms or a phenyl group,

m

represents an integer from 2 to 3 and

Preferred chelating agents according to formula (I) are derivatives of polyaminocarboxylates. Particularly preferred chelating agents according to formula (I) are the following compounds, wherein one of the carboxy groups COOH is substituted by the group X-D-Y according to formula (I):

Especially particularly preferred chelating agents according to formula (I) are DTPA, DOTA and D03A, wherein one of the carboxy groups COOH is substituted by a group X-D-Y according to formula (I).

Further, the chelating agents comprise at least one fluorine atom and a molecular moiety X, wherein the coordination distance between X and M changes upon influence of a certain enzymatic activity and thereby changing the chemical shift of the at least one fluorine atom. According to NMR theory, the distance d affects the shift according to the following formula: $$\mathrm{\&Dgr;}\mathrm{\&dgr;}=K\frac{3\mathrm{cos\vartheta }-1}{d^3}$$

where ϑ is the angle X-M-F where F is the at least one fluorine atom affected by M. The change in shift induced by the paramagnetic metal ion M is dependent on the distance between M and F in the third power.

The metal complex compounds according to the invention comprise preferably a chelating agent of formula (I) that comprises more than one fluorine atom, the fluorine atoms preferably showing fluorine chemical shifts that are essentially the same. Essentially the same means that the chemical shift values of all fluorine atoms are distributed within a sufficiently narrow range, preferably within a range of 50 ppm or less, particularly preferably within the range of 30 ppm or less, so that the signals from all the fluorine atoms are effectively sampled in MRI or NMR measurements.

In a preferred embodiment, the metal complex compounds according to the invention comprise a chelating agent of formula (I) that comprises at least one straight chain or branched chain alkyl group, aryl group or aralkyl group substituted by one or more fluorine atoms, preferably by more than one fluorine atoms. Preferably, the chelating agent of formula (I) comprises at least one fluorine atom or a perfluoroalkyl or perfluoroaryl group in which all hydrogen atoms are substituted by fluorine. The number of carbon atoms in these alkyl, aryl, aralkyl, perfluoroalkyl and perfluoroaryl groups is preferably 1 to 10. The above-mentioned groups may in addition contain one or more functional groups such as hydroxyl groups, amine groups, carbonyl groups or amide groups, or one or more heteroatoms such as N, O or S. Particularly preferably the chelating agent comprises at least one fluorine atom or at least one group selected from the group consisting of trifluoromethyl, perfluoroethyl, 2,2,2-trifluoroethyl, perfluoropropyl, perfluoroisopropyl, bis(trifluoromethyl)methyl, tris(trifluoromethyl)methyl, 2,2,3,3,3-pentafluoropropyl, perfluorobutyl, trifluoromethylphenyl, 1,3-di(trifluoromethyl)phenyl, trifluoromethylbenzyl, 1,3-di(trifluoromethyl)benzyl, tris(trifluoromethyl)methlphenyl, tris(trifluoromethyl)-methylbenzyl, fluorophenyl, difluorophenyl, pentafluorophenyl and pentafluorobenzyl. Especially particularly preferred, the chelating agent of formula (I) comprises at least one fluorine atom or a group selected from the group consisting of trifluoromethyl, tris(trifluoromethyl)methyl and pentafluorophenyl.

In another preferred embodiment, the chelating agent of formula (I) comprises at least one fluorine atom which changes fluorine chemical shift upon influence of a certain enzymatic activity and at least one fluorine atom which does not change fluorine chemical shift upon influence of said certain enzymatic activity. The latter fluorine atom(s) serve(s) as an internal standard.

The metal complex compounds according to the invention further comprise molecular moiety X and the coordination distance between the molecular moiety X and the paramagnetic metal ion M changes upon influence of a physiological parameter.

In a preferred embodiment, the molecular moiety X has a certain affinity to the paramagnetic metal ion M resulting in a certain coordination distance between X and M. The coordination distance is such that the chemical shift of the at least one fluorine atom is influenced. Upon influence of a certain enzymatic activity, the affinity of X to M is reduced, the coordination distance between X and M changes, thus the chemical shift of the at least one fluorine atom changes too. For example, the molecular moiety X having a certain affinity to the paramagnetic metal M might be a negatively charged X group (X^-).

The metal complex compounds according to the invention preferably comprise paramagnetic chelates containing a paramagnetic metal ion selected from the group consisting of La³⁺, Pr³⁺, Tm³⁺, Dy³⁺ Eu³⁺ and Mn²⁺ and a chelating agent selected from the group consisting of DTPA, DOTA, EDTA, DTPA-BMA, TTHA, DTPA, D03A and TETA, wherein one of the carboxy groups COOH is substituted by a group X-D-Y according to formula (I). Particularly preferred paramagnetic chelates are those containing a paramagnetic metal ions selected from the group consisting of La³⁺, Pr³⁺, Tm³⁺, Dy³⁺ Eu³⁺ and a chelating agent selected from the group consisting of DTPA, DOTA and D03A, wherein one of the carboxy groups COOH is substituted by a group X-D-Y according to formula (I).

The change in fluorine chemical shift that occurs upon influence of a certain enzymatic activity according to the invention is preferably at least 1 ppm, particularly preferably at least 2 ppm and especially particularly preferably at least 3 ppm. The change in fluorine chemical shift can be upfield or downfield (positive or negative). Changes in fluorine chemical shift can for example be calculated on shift data according to Berger et al. (Eds.), NMR Spectroscopy of the non-metallic elements, John Wiley & Sons, Chichester 1997, Chapter 6, p. 398-699 .

Another aspect of the invention are contrast agents or in vivo NMR markers comprising metal complex compounds according to the invention.

Yet another aspect of the invention is the use of metal complex compounds according to the invention as contrast agents or in vivo NMR markers.

Yet another aspect of the invention is the use of metal complex compounds according to the invention for the manufacture of contrast agents or in vivo NMR markers.

Yet another aspect of the invention is the use of metal complex compounds, contrast agents or in vivo NMR markers according to the invention for the monitoring or detection of physiological parameters, preferably for the monitoring or detection of abnormal physiological parameters.

Yet another aspect of the invention is use of metal complex compounds, contrast agents or in vivo NMR markers according to the invention for the diagnosis of diseases in the human or non-human animal body.

Yet another aspect of the invention is use of metal complex compounds, contrast agents or in vivo NMR markers according to the invention for detection of areas of disease in the human or non-human animal body.

Yet another aspect of the invention is the use of metal complex compounds according to the invention for the manufacture of a contrast agent or in vivo NMR marker for the in vivo detection of abnormal physiological parameters in the human or non-human animal body by determination of change in fluorine chemical shift upon influence of said physiological parameters on said metal complex compounds using ¹⁹F-MRI or ¹⁹F-NMR spectroscopy.

Metal complex compounds according to the invention wherein the coordination distance between X and M changes upon influence of certain enzyme activity comprise a molecular moiety X that is an enzyme substrate which reacts with a certain specific enzymes and thereby changes the coordination distance between the molecular moiety X and the paramagnetic metal ion M.

In a particularly preferred embodiment the metal complex compound according to the invention comprises alkyl-O-PO₃ ^2- or aryl-O-PO₃ ^2- which are substrates for phosphatases. The reaction of said substrate with phosphatases results in hydrolytic cleavage to alkyl-OH or aryl-OH and PO₄ ^2-. Preferably, the metal complex compound according to the invention comprises the following enzyme substrates for phosphatases:

Metal complex compounds comprising alkyl-O-PO₃ ^2- or aryl-O-PO₃ ^2- or contrast agents / in vivo NMR markers comprising said metal complex compounds are particularly preferred for detection of abnormal activity of phosphatases for the diagnosis of cancer or cancer related diseases, preferably for the diagnosis of prostate carcinoma, for the diagnosis of bone diseases, for the diagnosis of some liver diseases and for the diagnosis of thrombocytopenia.

In a further particularly preferred embodiment the metal complex compound according to the invention comprises alkyl-(NH)-(Glu)_n which is a substrate for aminopeptidase A. The reaction of said substrate with aminopeptidase A results in hydrolytic cleavage to alkyl-NH₃ ⁺ and n Glu.

In a further particularly preferred embodiment the metal complex compound according to the invention comprises 4-alkyl-(C₆R¹ R² R³ R⁴)NH-amino acid-NH₂, which is a substrate for aminopeptidase, wherein R¹-R⁴ are hydrogen or electronegative groups such as F, Cl, or NO₂, said electronegative groups being present in sufficient numbers to ensure that the amino group is minimally protonated at physiological pH. The reaction of said enzyme substrate with aminopeptideas results in hydrolytic cleavage to 4-alkyl-(C₆R¹ R² R³ R⁴)NH₂ and amino acid. The change in charge will depend on the charge of the amino acid residue (e.g., Lys or Arg would result in the loss of two positive charges).

Metal complex compounds comprising alkyl-(NH)-(Glu)_n which is a substrate for aminopeptidase A or 4-alkyl-(C₆R¹ R² R³ R⁴)NH-amino acid-NH₂, which is a substrate for aminopeptidase or contrast agents / in vivo NMR markers comprising said metal complex compounds are particularly preferred for detection of abnormal activity of said enzymes for the diagnosis of central nervous system diseases.

In a further particularly preferred embodiment the metal complex compound according to the invention comprises 4-alkyl-(C₆H₄)-CO-amino acid-CO₂H which is a substrate for carboxypeptidase. The reaction of said enzyme substrate with carboxypeptidase results in hydrolytic cleavage to 4-alkyl-(C₆H₄)-CO₂ ^- and amino acid.

Metal complex compounds comprising 4-alkyl-(C₆H₄)-CO-amino acid-CO₂H or contrast agents / in vivo NMR markers comprising said metal complex compounds are particularly preferred for detection of abnormal activity of carboxypeptidases for the diagnosis of cardiovascular diseases.

In a further particularly preferred the metal complex compound according to the invention comprises 4-alkyl-C₆H₄-CH₂-NH₃ ⁺ which is a substrate for monoamine oxidase. The reaction of said enzyme substrate with monoamine oxidase requires the presence of water and oxygen and results in hydrolytic cleavage to 4-alkyl-C₆H₄-CHO, H₂O₂ and NH₄ ⁺.

Metal complex compounds comprising 4-alkyl-C₆H₄-CH₂-NH₃ ⁺ or contrast agents / in vivo NMR markers comprising said metal complex compounds are particularly preferred for detection of abnormal activity of monoamine oxidase for the diagnosis of central nervous system diseases.

In a further particularly preferred embodiment the metal complex compound according to the invention comprises 1-alkyl-&bgr;-O-glucuronic acid which is a substrate for &bgr;-glucuronidase. The reaction of said enzyme substrate with &bgr;-glucuronidase results in hydrolytic cleavage to alkyl-OH and glucuronic acid.

Analogous reactions may be devised for other enzymes such as e.g. galacturonidase or iduronidase.

Metal complex compounds comprising 1-alkyl-&bgr;-O-glucuronic acid or contrast agents / in vivo NMR markers comprising said metal complex compounds are particularly preferred for detection of abnormal activity of &bgr;-glucuronidase for the diagnosis of diabetes mellitus, renal diseases, pancreatic cancer and liver diseases.

Besides hydrolytic cleavage there are many chemical modifications that may occur upon reaction of the metal complex compound according to the invention comprising an enzyme substrate with a specific enzyme. The following chemical modifications are included:

• Hydrolytic cleavage
  • Peptidases (carboxypeptidases, aminopeptidases)
  • Glycosidases: glucuronidases, glucosidases, galactosidases, galacturonidases, mannosidases, sialidases, lactase
• Reactions involved in signalling pathways:
  • Hydrolysis of phosphate esters in protein: protein phosphatases
  • Deamination of neurotransmitters: monoamine oxidase

Inherited defects in enzyme molecules are by far the largest category of heritable diseases. As expected, the kind and severity of disease varies greatly. In some populations, one individual in a hundred may be affected by a specific heritable enzyme deficiency. In the diagnosis of defects in enzyme molecules it is often important to localize the areas a specific enzyme is not expressed. This could be done by the methods according to the invention. A patient may for example show neurological symptoms, but the primary affected organ could be the liver. Many of the enzymes given in the following list have been studied in detail, see Scriver et al in "The metabolic basis of inherited disease", 6th Edn., McGraw-Hill, New York 1989 . Artificial substrates for these enzymes are available and metal complex compounds comprising said artificial substrates or contrast agents / in vivo NMR markers comprising said metal complex compounds can be used to detect said enzymes for the diagnosis of inherited defects.

Enzymes that are known to be defective in various inherited diseases:

• Disorders of lysosomal enzymes
  
  &agr;-L-iduronidase
  
  Iduronate sulfatase
  
  Heparan-N-sulfatase
  
  &agr;-N-acetylglucosaminidase
  
  Acetyl-CoA-&agr;-glucosaminide acetyltransferase
  
  Acetylglucosamine 6-sulfatase
  
  Galactose 6-sulfatase
  
  &bgr;-Galactosidase
  
  N-Acetylgalactosamine 4-sulfatase
  
  &bgr;-Glucuronidase
  
  UDP:N-Acetylglucosamine:lysosomal enzyme N-acetylglucosaminyl-1-phosphotransferase
  
  &agr;-Mannosidase
  
  &agr;-Neuraminidase
  
  Aspartylglucosaminidase
  
  &agr;-L-Fucosidase
  
  Acid lipase
  
  Acid ceramidase
  
  Sphingomyelinase
  
  Glucocerebrosidase
  
  Galactosylceramidase
  
  Steroid sulfatase
  
  Arylsulfatase
  
  &agr;-Galactosidase
  
  &agr;-N-Acetylgalactosaminidase
  
  Acid &bgr;-galactosidase
  
  &bgr;-Hexosaminidase
• Disorders of connective tissues
  
  Lysyl hydroxylase
  
  Collagenase
  
  Alkaline phosphatase
  
  Carbonic anhydrase

The metal complex compound or the contrast agent / in vivo NMR marker comprising said metal complex compound according to the invention comprising an enzyme substrate can comprise as an enzyme substrate synthetic organic compounds, naturally occurring compounds or semi-synthetic compounds. The metal complex compound or the contrast agent / in vivo NMR marker comprising said metal complex compound comprise for instance peptides, peptido-mimetics, fatty acids, proteins, carbohydrates or biological precursors thereof, which may contain one or more of the following functional groups: alcohols, phenols, esters including esters with other acids than carboxylic acids, amides, amines, mercapto-groups, aromatic rings and heterocyclic ring systems. The overall structure of the enzyme substrate can be cyclic or linear.

Metal complex compounds according to the invention wherein the coordination distance between X and M changes upon influence of enzyme activity can be used as contrast agents or in vivo NMR markers or can be used for the manufacture of contrast agents or in vivo NMR markers. Such contrast agents / in vivo NMR markers can preferably be used for in vivo detection of enzyme activity, preferably for the detection of abnormal enzyme activity, said detection of abnormal enzyme activity being preferably used for the diagnosis of diseases in the human or non-human animal body or for detecting areas of disease in the human or non-human animal body.

In a further preferred embodiment the metal complex compounds according to the invention further comprise a targeting vector.

A targeting vector according to the present invention is a molecular moiety that enables targeting of the metal complex compounds to a specific site in the human or non-human animal body, preferably located in the area of disease. Said specific sites are, for example, receptors, cells and cell compartments. Preferably, the targeting vector enables targeting of the metal complex compounds according to the invention to a specific receptor, preferably to a tumour specific receptor. In a particularly preferred embodiment, the targeting vector is a molecular moiety showing affinity for a tumour specific receptor.

A metal complex compound according to the invention further comprising a targeting vector or a contrast agent / in vivo NMR marker comprising said metal complex compound should show enhanced residence time at the area of disease.

The metal complex compound according to the invention or the contrast agent / in vivo NMR marker comprising said metal complex compound can be a water-soluble or water-insoluble molecule, e.g. a compound with limited solubility in water so that the compound has to be administered as a powder or a suspension in the methods according to the invention. The molecular weight of the metal complex compound or the contrast agent / in vivo NMR marker comprising said metal complex compound varies and can be low (50-2000) or high (above 2000).

When the metal complex compound according to the invention carries an overall charge, it may be used in the form of a salt with a physiologically acceptable counterion, for example an ammonium, substituted ammonium, alkali metal or alkaline earth metal cation or an anion deriving from an inorganic or organic acid.

The metal complex compound according to the invention or the contrast agent / in vivo NMR marker comprising said metal complex compound used for diagnosis is preferably formulated in conventional pharmaceutical or veterinary parenteral administration form, e.g. suspensions, dispersions, etc., for example in an aqueous vehicle such as water for injections.

The metal complex compound or the contrast agent / in vivo NMR marker comprising said metal complex compound according to the invention may further contain pharmaceutically acceptable diluents and excipients and formulation aids, for example stabilizers, antioxidants, osmolality adjusting agents, buffers or pH-adjusting agents.

The most preferred formulation for the metal complex compounds or the contrast agents / in vivo NMR markers comprising said metal complex compounds used for diagnosis of diseases in the human or non-human animal body is a sterile solution of suspension for intravascular administration or for direct injection into area of interest. Where said metal complex compounds or contrast agents / in vivo NMR markers comprising said metal complex compounds are formulated in a ready-to-use form for parenteral administration, the carrier medium is preferably isotonic or somewhat hypertonic.

The dosage of the metal complex compounds or contrast agents comprising said metal complex compounds used in the diagnosis of diseases in the human or non-human animal body will depend upon the clinical indication, the contrast generating species and the means by which contrast enhancement occurs.

While the metal complex compounds according to the invention or contrast agents /in vivo NMR markers comprising said metal complex compounds according to the invention are particularly suitable for the diagnosis of diseases in the human or non-human animal body involving parenteral administration, e.g. into the vasculature or directly into an organ or muscle tissue, intravenous administration being especially preferred, administration via a non-parenteral route is also applicable, e.g. transdermal, nasal, sub-lingual administration or administration into an external body cavity, e.g. the gastro-intestine tract, the bladder, the uterus or the vagina. The present invention is deemed to extend to cover such administration.

In another aspect the methods according to the invention can be used for follow up therapy. If therapeutic treatment of a disease results in change of a physiological parameter i.e. in an increase / a decrease of one or more specific enzymes, the success of said therapeutic treatment can easily be followed up by the methods according to the invention.

In yet another aspect the methods according to the invention can be used for the selection of drug therapy. If it was for example stated that an increased / decreased enzyme activity is responsible for a certain disease said abnormal enzyme activity could be selected as a target for drug therapy. Preferably, the methods according to the invention are first used for the selection of drug therapy and subsequently for follow up therapy with the selected drug.

In yet another aspect the methods according to the invention can be used for the dosing of drugs in drug therapy. If therapeutic treatment of a disease targets for example one or more specific enzymes, the activity of said enzyme(s) should be increased / decreased by said drug therapy the methods according to the invention can be used to determine if the drug therapy is carried out using a proper dose of said drug.

In a preferred embodiment, the methods of the invention are in a first step used for the diagnosis of disease and the selection of drug therapy and in a second step for the dosing of drugs in drug therapy as well as for follow up said drug therapy.

0.5 g (0.84 mmol) of 1,4,7-tri(carboxymethyl-tert-butylester)-1,4,7,10-tetraazacyclododecan (D03A-TBE) was added to a jacketed vessel containing 7 ml of THF (tetrahydrofurane). The THF was preheated using a circulating bath to 40°C. 0.162 ml (2.52 mmol) of epifluorohydrin was added followed by the slow addition of 0.129 ml (0.093 mmol) of triethylamine over a five minute period. The reaction mixture was closed and stirred using a magnetic stirrer overnight at 40°C. A further 0.047 ml (0.34 mmol) of triethylamine was added after approximately 17 hours. The reaction was then left to stir for 3 days at 40°C.

2 ml of the reaction mixture (0.24 mmol of material) was concentrated in vacuum (20 mmHg/30°C) to remove solvent and excess triethylamine. Removal of the protecting groups was done by addition of 5ml of TFA (trifluoroacetic acid) to the concentrated raw product, this was followed by stirring overnight. The mixture was again concentrated under vacuum (20mm Hg/30°C). The raw product was dissolved in 2 ml H₂O, the pH adjusted to about 10 using 25% NH₃(aq). The mixture was then loaded onto a negative ion exchanger (Biorad AG 1-X8, 200-400 mesh, acetate form). After washing with 500 ml H₂O, the product was eluted using 150 ml 3M formic acid. Sequential washing and concentrating with 5 ml H₂O (7x) yielded 0.2g of a clear oil. MS (ES+): 423.2 (100, [M+H]⁺

MS data showed the expected molecular ion for this compound. NMR data also supported the given structure.

All spectra were acquired in 5 mm tubes using a Varian Unity Inova 500 spectrometer (11 Tesla) with a 1H{broad-band} indirect detection, pulsed field gradient probe. Preliminary experiments were done in both D₂O and CD₃OD solvents at various temperatures to establish an optimum time-scale window with respect to the molecule's dynamics but the results on which the structure determination was made and the derived NMR data were all obtained in CD₃OD at 50°C. TMS was used as internal reference for the ¹H and ¹³C spectra and C₆F₆ as internal reference for the ¹⁹F spectra. Apart from ¹H and ¹⁹F directly detected spectra, ¹H-¹H-GCOSY and ¹H{¹³C}-GHSQC and GHMBC 2D spectra were acquired.

¹H-NMR: (500MHz);&dgr; (CD3OD,50IC) 4.46 (d of ABX systems), 4.35 (d of multiplets), 4.13 (AB quartet, J ca.17 Hz), 3.66 (AB quartet, J 18.5 Hz), 3.46-3.57 (broad multiplet), 3.39 (AB quartet, J ca.20 Hz), 3.04-3.28 (broad multiplet).

¹⁹F-NMR: (470MHz);&dgr; (CD30D,50°C) -231.2 ppm (t J 47.7 Hz of d J 19.6 Hz).

The europium complex of this ligand was made by dissolving 75 mg ligand (1,4,7-tri(carboxymethyl)-10-(3-fluoro-2-hydroxypropanoyl)-1,4,7,10-tetraazacyclododecan) in 1 ml H₂O, followed by adding 36mg of EuCl₃ and heating at 50°C for 5 minutes. MS (ES+): 573,1 (34, [M]). MS data of the mixture showed the characteristic isotopic pattern for the europium complex.

2.0 g (3,358 mmol) of 1,4,7-tri(carboxymethyl-tert-butylester)-1,4,7,10-tetraazacyclododecan (D03A-TBE) was added to a jacketed vessel containing 28 ml of THF (tetrahydrofurane). The THF was preheated using a circulating bath at 30°C. 1.23 g (10.07 mmol) of epifluorohydrin was added followed by the slow addition of 0.702 ml (5.04 mmol) of triethylamine over a ten minute period. The reaction mixture was closed tightly and stirred at 30°C, using a magnetic stirrer. The temperature was increased after about 14 hours to 40°C where it stayed for 9 hours before it was lowered to 20°C. The reaction mixture was then stirred for an additional 24 hours at 20°C. The reaction mixture was concentrated in vacuum (20 mmHg/30°C) to remove solvent and excess of triethylamine. 2 g of a clear oil were obtained. MS (ES+): 627,3 ([M+H]⁺). MS and NMR both indicated formation of the expected product.

All spectra were acquired in 5mm tubes using a Varian Unity Inova 500 spectrometer (11 Tesla) with a 1H{broad-band} indirect detection, pulsed field gradient probe and - for directly detected ¹³C - a broad-band{¹H} probe. Preliminary experiments were done in both CDCl₃ and DMSO-d6 solvents at various temperatures to establish an optimum time-scale window with respect to the molecule's dynamics but the results on which the structure determination was made and the derived NMR data were all obtained in CDCl₃ at 45°C. TMS was used as internal reference for the ¹H and ¹³C spectra and C₆F₆ as internal reference for the ¹⁹F spectrum. Apart from ¹H, ¹⁹F and ¹³C directly detected spectra, ¹H-¹H GCOSY , ¹H{¹³C} GHSQC 2D spectra and ¹³C{¹H} DEPT were acquired.

¹H-NMR: (500MHz);&dgr; (CDCl₃,45°C) 4.48-4.78 (broad), 3.43 (AB quartet 17.6 Hz), 3.36-3.53 (broad), 3.33 (s), 3.07-3.26 (broad), 2.80-3.06 (broad multiplets)

¹⁹F-NMR: (470MHz);&dgr; (CDCl₃,45°C) -79.4 (d J 7 Hz).