CHELATING AGENTS

Abstract: There are provided chelating agents of formula (I) (wherein n is 0 or 1 and at least one R<1> group comprises a group NR<11>R<14> where one of R<11> and R<14> comprises a cyclic lipophilic group) and metal chelates and salts thereof. The chelates with paramagnetic or heavy metal ions are particularly suited for use as hepatobiliary contrast agents.

Description: CHE ATING AGENTS The present invention relates to chelating agents, more particularly aminopolycarboxylic acid chelants, and metal chelates thereof and the use of such chelating agents and chelates in diagnostic imaging, radiotherapy or heavy metal detoxification, and in particular as hepatobiliary contrast agents. Medical uses of chelating agents are well established, for example as stabilizers for pharmaceutical preparations, as antidotes for poisonous heavy metal species and as agents for the administration, in chelate form, of metal ions for radiotherapy or diagnostic imaging, e.g. X-ray, magnetic resonance imaging (MRI) , ultrasound or scintigraphy. Aminopolycarboxylic acids and derivatives thereof (hereinafter referred to as APCAs) are well known as particularly effective chelants and are described in a wide range of publications, for example in US-A-2407645 (Bersworth) , EP-A-71564 (Schering) , EP-A-130934 (Schering) , EP-A-165728 (Nycomed) , US-A-4647447 (Schering) , US-A-4826673 (Mallinckrodt) , US-A-4639365 (Sherry) , EP-A-263059 (Schering) , EP-A-230893 (Bracco) , EP-A-325762 (Bracco) , O-A-86/06605 (Lauffer) , US-A- 4746507 (Salutar) , EP-A-290047 (Salutar) , WO-A-90/01024 (Mallinckrodt) , US-A-4687659 (Salutar) and EP-A-299795 (Nycomed) and in the documents cited in these patent publications. Thus, for example, EP-A-71564 describes paramagnetic metal chelates, for which the chelating agent is nitrilotriacetic acid (NTA) , f \ N,N,N* ,N'-ethylenedι.amι.netetraacetιc aci.d (EDTA) , * N-hydroxyethyl-N,N" ,N'-ethylenedia inetriacetic acid (HEDTA), N,N,N' ,N",N"-diethylenetriaminepentaacetic acid (DTPA) and N-hydroxyethylimino-diacetic acid, as being suitable as contrast agents for MRI, contrast being achieved by the effect of the magnetic field of the paramagnetic species (e.g. Gd(III)) with the chelating agents serving to reduce the toxicity and to assist administration of the paramagnetic species. Amongst the particular metal chelates disclosed by EP-A-71564 was the dimeglumine salt of GdDTPA, the use of which as an MRI contrast agent has recently received much attention. To improve stability, water solubility and selectivity, relative to the APCA chelating agents described in EP-A-71564, Schering in EP-A-130934 proposed the partial substitution for the N-attached carboxyalkyl groups of alkyl, alkoxyalkyl, alkoxycarbonylalkyl or alkylaminocarbonylalkyl groups, where any amide nitrogens may themselves carry polyhydroxy-alkyl groups. For reduced toxicity, Salutar Inc, in for example US-A-4687659, has proposed the use as MRI contrast agents of chelates of paramagnetic metal ions and bisa ides of DTPA, in particular DTPA-bismethylamide. In the same patent, Salutar suggested that for imaging of the liver chelates of DTPA-bis(higher alkyl-amides) might be used. In this field of hepatobiliary MRI contrast agents Nycomed, in EP-A-165728, have also proposed the use of paramagnetic chelates of certain anilide group- containing iminodiacetic acids and Lauffer in O-A- 86/06605 has suggested the use of paramagnetic chelates of various benzene ring containing chelants, e.g. ethylene-bis-(2-hydroxyphenyl glycine) (EHPG) , bis(2- hydroxybenzyl)-ethylenedia ine diacetic acid (HBED) , benzo- and dibenzo-DTPA and triaza and tetraaza macrocycles which carry a fused benzene ring. Still further APCA chelants for use in preparing MRI contrast agents have been proposed by Bracco in EP- A-230893 and EP-A-325762. These for the most part carry aryl or aralkyl substituents on the alkylene part of one or more of the nitrogen-attached carboxyalkyl complex- forming moieties. Among the chelates covered is GdBOPTA, in which the chelant BOPTA has a DTPA structure with one N 3 carboxymethyl replaced by a 2-benzyloxy-l- carboxy-ethyl group. GdBOPTA has been described by Vittadini et al in CMR '89, MR19 as a liver-specific MRI contrast agent. Schering in EP-A-263059 have proposed a further range of DTPA and EDTA amide chelants for use in preparing MRI contrast agents. While commenting on the high lipophilicity of the DTPA-bisamides proposed by Salutar in WO-A-86/02841 (equivalent to US-A-4687659 discussed above) , Schering have exemplified such compounds as GdDTPA-bispentylamide, GdDTPA-bisbutylamide and GdDTPA-phenylamide as well as chelates of further DTPA-alkylamides in which the alkyl moieties are substituted by hydrophilic groupings such as hydroxyl and alkoxy groups. There is however a general and continuing need for APCA chelants which form metal chelates of reduced toxicity, improved stability, improved water solubility or improved biodistribution (e.g. enhanced tissue or organ specificity) . We now propose certain improved chelating agents, in particular amide derivatives of APCAs. Viewed from one aspect therefore the invention provides chelants of formula I (I) CH 2 COOH (wherein n is 0 or 1; one group R is a group NR 1 R where R 11 is a hydroxyl or alkoxy group or a group -L-Cy or -O-L-Cy, and R u is a hydrogen atom, an alkyl group or a group -L-Cy, and the other group R 1 is a hydroxyl group or a group NR R 14 ; L is a bond or a straight-chain or branched saturated or unsaturated alkylene group optionally interrupted by a carbocyclic or heterocyclic saturated or unsaturated group and optionally attached to the Cy group by a peptide or carbonyl link and optionally substituted by further Cy groups or by aminocarbonyl, acyl or acylamino groups; and Cy is a cyclic lipophilic group, eg a carbocyclic or heterocyclic saturated or unsaturated group itself optionally carrying one or more fused carbocyclic or heterocyclic saturated or unsaturated rings and optionally substituted by halogen atoms (eg iodine, chlorine or bromine) , alkyl, alkylamino, dialkylamino, carbamoyl, N-alkylcarbamoyl, acetamido, N- alkylacetamido and carbocyclic or heterocyclic saturated or unsaturated groups; with the provisos that in any NR 11 R 14 group one of R 11 and R 14 group comprises a L-Cy group and that where n is 1 at least one R 1 is other than phenylamine, benzylamine or methoxybenzylamine) and metal chelates and salts thereof. Unless specified otherwise, all alkyl or alkylene moieties in the compounds of the invention preferably contain up to 10, particularly preferably up to 6, carbon atoms. The lipophilic Cy groups and the other cyclic rings in the compounds of formula I are particularly preferably mono or polycyclic groups containing 5 to 7 ring members in each ring, the rings if heterocyclic containing up to 3, preferably 1 or 2, non-adjacent ring heteroatoms selected from O, N and S. Preferred such rings include benzene, pyridine, pyrimidine, pyrazine, 1,3-oxazine, 1,4-oxazine, 1,3- thiazine, 1,4-thiazine, pyrrole, imidazole, 1,3-oxazole, 1,3-thiazole, furan, thiophene, piperidine, piperazine, morpholine, perhydro-l,4-thiazine and pyrrolidine. Thus particular examples of lipophilic Cy groups include groups of formula la to Ie ( l α ) and other condensed acyclic rings (where R 3 to R 8 is each independently a bond or a hydrogen or halogen atom or an alkyl, alkylaπtino, dialkylamino, carbamoyl, N-alkylcarbamoyl, acetamido or N-alkylacetamido group or two adjacent groups from R 3 to R 8 together form a C 2 . 5 alkylene or azaalkylene bridge, the point of attachment to L being a carbon of said bridge or one of said groups R 3 to R 8 ; X is nitrogen or CH and Y is CH or nitrogen; X 1 is CH 2 , NH, oxygen, sulphur or a bond; X" is nitrogen, oxygen or sulphur and Y" is CH or nitrogen; and R 9 is a bond or hydrogen, alkyl or aralkyl, eg benzyl; such rings preferably not having ring heteroatoms at adjacent ring positions) . The linker moiety L is conveniently a branched or linear alkylene chain, eg such that LCy is of formula -(CHR 10 ) k -(CO) a -(NR 10 ) b -(CO) C -R 10 where k is 0-10, especially 1 to 8, more especially 1 to 6; a, b and c are 0 or 1, the sum of a and c being 0 or 1; each R 10 is a hydrogen atom, an alkyl group, an optionally esterified carboxyl group or a group Cy, at least one and preferably only one being a group Cy, and one or more CHR 10 moieties may optionally be replaced by a 5-7 membered saturated homo or heterocyclic ring. The carboxyl groups in the compounds of formula I may, for example, be in the form of carboxylate salt groups, for example groups of formula -COOMt (where Mt is a monovalent cation or a fraction of a polyvalent cation, for example an ammonium or substituted ammonium ion or a metal ion, for example an alkali metal or + alkaline earth metal ion) . Particularly preferably, Mt is a cation deriving from an organic base, for example meglumine. It is also particularly preferred that the number of the ion-forming carboxyl groups in the compounds of formula I be chosen to equal the valency of the metal species to be chelated by the compound of formula I. Thus, for example, where Gd(III) is to be chelated, the chelating agent of formula I preferably contains three ion-forming -COOH or -COOMt groups. In this way, the metal chelate will be formed as a neutral species, a form preferred since the osmotic pressures in concentrated solutions of such compounds are low and since their toxicities relative to their ionic analogues are significantly reduced. Preferably the compounds of the invention contain two -L-Cy groups and particularly preferred compounds according to the invention include the chelants of formula II HOOCCH 2 NCH 2 CH 2 [NCH 2 CH 2 ] NCH 2 COOH R 13 NR 15 CO ICH 2 C /H 2 COOH CH 2 CONR 15 R 13 < « > (where n is 0 or 1 , R 15 is hydrogen or methyl and R 13 is a group selected from benzyl, 2-phenyl-ethyl, 1-phenyl-ethyl, pyrid-4-yl, pyrid-3-yl, pyrid-2-yl, 3- morpholino-propyl, N-benzyl-piperidin-4-yl and indanyl groups and iodinated such groups) , and the metal chelates and salts thereof. The chelant compounds of the invention may be prepared by amidation, eg analogously to EP-A-130934 (Schering) and US-A-4687659 (Salutar) of EDTA or DTPA or an activated or protected derivative thereof (eg an acid anhydride or bisanhydride) with an amine compound of formula III HNR 1 'R K ' (III) (where R 11 ' and R 14 ' are groups R 11 and R 14 as hereinbefore defined or protected such groups) , followed where necessary by deprotection. As protecting groups, conventional protecting groups may be used, for example groups such as are described by T.W. Greene in "Protective Groups in Organic Synthesis", John Wiley & Sons, 1981. Alternatively the compounds may be prepared in two or more stages, in the first reacting DTPA, EDTA or a derivative thereof to introduce one or two NR 11 " R 14 " groups (where one of R 11 " and R 14 " is a group R 11 ' or R 14 ' and the other is a Cy-free analogues of R 11 ' or R 14 ') and in a second stage to introduce the Cy groups, eg by a peptide condensation reaction. The amidation reactions are preferably performed in the liquid phase. Thus for example a solution of the amine in a solvent such as water, dipolar aprotic solvents, such as acetonitrile, N-methylpyrrolidone, N- methylmorpholine, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran and the like or mixtures thereof is prepared. The anhydride is added in portions or optionally dissolved in a dipolar aprotic anhydrous solvent such as acetonitrile, N- ethylpyrrolidone, N-methylmorpholine, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran and the like or mixtures thereof. The reaction mixture is stirred under a nitrogen atmosphere for a period ranging between 0.5 hour and 3 days, preferably between 1 hour and 24 hours. The reaction temperatures generally range between about 0°C and 100°C, temperatures of about 20°C to 80°C being preferred. For solvents with a low boiling point (100"C or less) the reaction mixture can eventually be evaporated to dryness. For the solvents with higher boiling points, further solvents such as for example diethylether may be added and/or cooling may be used to precipitate the product. Thus for example the bisamide chelants may be prepared by amidation as follows: a) the amine of formula III is dissolved in a dry polar aprotic solvent, e.g. acetonitrile or chloroform, in a ratio of about 1:10 w:v amine:solvent. The bisanhydride of DTPA (or EDTA) (0.5 equivalents to the amine) is added as dry powder in portions, with thorough stirring, and the reaction is allowed to proceed overnight. In the case of less reactive amines such as for example 2-aminopyridine, extensive refluxing may be necessary. In most cases the product precipitates from the reaction mixture and can be collected by filtration. Otherwise the product can be precipitated by addition of diethyl ether and/or by cooling. In the case of the bis-amides with non-heterocyclic side groups, the product may be purified as follows: the precipitate from a) is dissolved in deionized water, and if necessary the pH is adjusted to 8-10 using dilute NaOH. The pH is then adjusted to 3-3.5 with dilute HC1, and the precipitate is collected by filtration. Chelants of formula I may be used as the basis for bifunctional chelants or for polychelant compounds, that is compounds containing several independent chelant groups, by substituting for a hydrogen atom or hydroxyl group a bond or linkage to a macromolecule or polymer, e.g. a tissue specific biomolecule or a backbone polymer such as polylysine or polyethyleneimine which may carry several chelant groups and may itself be attached to a macromolecule to produce a bifunctional-polychelant. Such macromelecular derivatives of the compounds of formula I and the salts and metal chelates thereof form a further aspect of the present invention. The linkage of a compound of formula I to a macromolecule or backbone polymer may be effected by any of the conventional methods such as the carbodiimide method, the mixed anhydride procedure of Krejcarek et al. (see Biochemical and Biophysical Research Communications 77.: 581 (1977)), the cyclic anhydride method of Hnatowich et al. (see Science 220: 613 (1983) and elsewhere) , the backbone conjugation techniques of Meares et al. (see Anal. Biochem. 142: 68 (1984) and elsewhere) and Schering (see EP-A-331616 for example) and by the use of linker molecules as described for example by Nycomed in WO-A-89/06979. Formation of salts and chelates of the chelants of the invention may again be performed in a conventional manner. The chelating agents of the present invention are particularly suitable for use in detoxification or in the formation of metal chelates, chelates which may be used for example in or as contrast agents for in vivo or in vitro magnetic resonance (MR) , X-ray or ultrasound diagnostics (e.g. MR imaging and MR spectroscopy) , or scintigraphy or in or as therapeutic agents for radiotherapy, and such metal chelates form a particularly important embodiment of the present invention. Salts or chelate complexes of the compounds of the invention containing heavy metal ions are particularly useful in diagnostic imaging or therapy. Especially preferred are salts or complexes with metals of atomic numbers 20-32, 42-44, 49 and 57 to 83, particularly Gd, Dy and Yb. For use as an MR-diagnostics contrast agent, the chelated metal ion is particularly suitably a paramagnetic ion, the metal conveniently being a transition metal or a lanthanide, preferably having an atomic number of 21-29, 42, 44 or 57-71. Metal chelates in which the metal species is Eu, Gd, Dy, Ho, Cr, Mn or Fe are especially preferred and Gd , Mn and Dy are particularly preferred. For such use, the paramagnetic metal species is conveniently non-radioactive as radioactivity is a characteristic which is neither required nor desirable for MR-diagnostics contrast agents. For use as X-ray or ultrasound contrast agents, the chelated metal species is preferably a heavy metal species, for example a non-radioactive metal with an atomic number greater than 37, preferably greater than 50, e.g. Dy 3+. For use in scmtigraphy and radiotherapy, the chelated metal species must of course be radioactive and any conventional complexable radioactive metal isotope, such as 99mTc or 111In for example, may be used. For radiography, the chelating agent may be in the form of a metal chelate with for example Cu, Sm or 90 Y. For use in detoxification of heavy metals, the chelating agent must be in salt form with a physiologically acceptable counterion, e.g. sodium, calcium, ammonium, zinc or meglumine, e.g. as the sodium salt of the chelate of the compound of formula I with zinc or calcium. Where the metal chelate carries an overall charge, such as is the case with the prior art Gd DTPA, it will conveniently 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. In this regard, meglumine salts are particularly preferred. Viewed from a further aspect, the present invention provides a diagnostic or therapeutic agent comprising a metal chelate, whereof the chelating entity is the residue of a compound of formula I or salt thereof, together with at least one pharmaceutical or veterinary carrier or excipient, or adapted for formulation therewith or for inclusion in a pharmaceutical formulation for human or veterinary use. Viewed from another aspect, the present invention provides a detoxification agent comprising a chelating agent according to the invention in the form of salt with a physiologically acceptable counterion, together with at least one pharmaceutical or veterinary carrier or excipient, or adapted for formulation therewith or for inclusion in a pharmaceutical formulation for human or veterinary use. The diagnostic and therapeutic agents of the present invention may be formulated with conventional pharmaceutical or veterinary formulation aids, for example stabilizers, antioxidants, osmolality adjusting agents, buffers, pH adjusting agents, etc. and may be in a form suitable for parenteral or enteral administration, for example injection or infusion or administration directly into a body cavity having an external escape duct, for example the gastrointestinal tract, the bladder or the uterus. Thus the agent of the present invention may be in a conventional pharmaceutical administration form such as a tablet, capsule, powder, solution, suspension, dispersion, syrup, suppository, etc; however, solutions, suspensions and dispersions in physiologically acceptable carrier media, for example water for injections, will generally be preferred. The compounds according to the invention may therefore be formulated for administration using physiologically acceptable carriers or excipients in a manner fully within the skill of the art. For example, the compounds, optionally with the addition of pharmaceutically acceptable excipients, may be suspended or dissolved in an aqueous medium, with the resulting solution or suspension then being sterilized. Suitable additives include, for example, physiologically biocompatible buffers (as for example, tromethamine hydrochloride) , additions (e.g., 0.01 to 10 mole percent) of chelants (such as, for example, DTPA, a DTPA-bisamide or non-complexed chelants of formula I) or calcium chelate complexes (as for example calcium DTPA, CaNaDTPA-bisamide, calcium salts or chelates of chelants of formula I), or, optionally, additions (e.g., 1 to 50 mole percent) of calcium of sodium salts (for example, calcium chloride, calcium ascorbate, calcium gluconate or calcium lactate combined with metal chelate complexes of chelants formula I and the like) . If the compounds are to be formulated in suspension form, e.g., in water or physiological saline for oral administration, a small amount of soluble chelate may be mixed with one or more of the inactive ingredients traditionally present in oral solutions and/or surfactants and/or aromatics for flavouring. For MRI and for X-ray imaging of some portions of the body the most preferred mode for administering metal chelates as contrast agents is parenteral, e.g., intravenous administration. Parenterally ad inistrable forms, e.g., intravenous solutions, should be sterile and free from physiologically unacceptable agents, and should have low osmolality to minimize irritation of other adverse effects upon administration, and thus the contrast medium should preferably be isotonic or slightly hypertonic. Suitable vehicles include aqueous vehicles customarily used for administering parenteral solutions such as Sodium Chloride Injection, Ringer's Injection, Dextrose Injection, Dextrose and Sodium Chloride Injection, Lactated Ringer's Injection and other solutions such as are described in Remington's Pharmaceutical Sciences, 15th ed. , Easton: Mack Publishing Co., pp. 1405-1412 and 1461-1487 (1975) and The National Formulary XIV, 14th ed. Washington: American Pharmaceutical Association (1975) . The solutions can contain preservatives, antimicrobial agents, buffers and antioxidants conventionally used for parenteral solutions, excipients and other additives which are compatible with the chelates and which will not interfere with the manufacture, storage or use of products. Where the diagnostic or therapeutic agent comprises a chelate or salt of a toxic metal species, e.g. a heavy metal ion, it may be desirable to include within the formulation a slight excess of the chelating agent, e.g. as discussed by Schering in DE-A-3640708, or more preferably a slight excess of the calcium salt of such a chelating agent. For MR-diagnostic examination, the diagnostic agent of the present invention, if in solution, suspension or dispersion form, will generally contain the metal chelate at concentration in the range 1 micromole to 1.5 mole per litre, preferably 0.1 to 700mM. The diagnostic agent may however be supplied in a more concentrated form for dilution prior to administration. The diagnostic agent of the invention may conveniently be admi .ni.stered i.n amounts of from 10-3 to 3 mol of the metal species per kilogram of body weight, e.g. about 1 mmol Gd/kg bodyweight. For X-ray examination, the dose of the contrast agent should generally be higher and for scintigraphic examination the dose should generally be lower than for MR examination. For radiotherapy and detoxification, conventional dosages may be used. Viewed from a further aspect, the present invention provides a method of generating enhanced images of the human or non-human animal body, especially the liver, which method comprises administering to said body a diagnostic agent according to the present invention and generating an X-ray, MR-diagnostics, ultrasound or scintigraphic image of at least a part thereof. Viewed from a further aspect, the present invention provides a method of radiotherapy practised on the human or non-human animal body, which method comprises administering to said body a chelate of a radioactive metal species with a chelating agent according to the invention. Viewed from a further aspect, the present invention provides a method of heavy metal detoxification practised on the human or non-human animal body, which method comprises administering to said body a chelating agent according to the invention in the form of a salt with a physiologically acceptable counterion. Viewed from a yet further aspect, the present invention also provides the use of the compounds, especially the metal chelates, according to the invention for the manufacture of diagnostic or therapeutic agents for use in methods of image generation, detoxification or radiotherapy practised on the human or non-human animal body. Viewed from a still further aspect, the present invention provides a process for the preparation of the metal chelates of the invention which process comprises admixing in a solvent a compound of formula I or a salt (e.g. the sodium salt) or chelate thereof together with an at least sparingly soluble compound of said metal, for example a chloride, oxide or carbonate. Viewed from a yet still further aspect, the present invention provides a process for the preparation of the diagnostic or therapeutic agent of the present invention, which comprises admixing a metal chelate according to the invention, or a physiologically acceptable salt thereof, together with at least one pharmaceutical or veterinary carrier or excipient. Viewed from a yet still further aspect, the present invention provides a process for the preparation of the detoxification agent of the invention, which comprises admixing a chelating agent according to the invention in the form of a salt with a physiologically acceptable counterion together with at least one pharmaceutical or veterinary carrier or excipient. The disclosures of all of the documents mentioned herein are incorporated by reference. The present invention will now be illustrated further by the following non-limiting Examples. All ratios and percentages given herein are by weight and all temperatures are in degrees Celsius unless otherwise indicated. Example 1 3,6,9,12-Tetraaza-6.9-bis(carboxymethyl)-4.11-dioxo- 2,13-diphenyltetradecane EDTA-bis(anhydride) 1.0 g (3.9 mmol) was gradually added to a stirred solution of 1-phenylethylamine 0.9 g (7.8 mmol) in dried acetonitrile (40 ml) at ambient temperature and under a nitrogen atmosphere. The solution was heated to reflux temperature (85°C) and refluxed for 20 hours. The mixture was then cooled, and the precipitate which had formed was isolated by filtration and dried. Yield 1.5g (77.1%) . The crude solid was dissolved in 20 ml water to which was added IN NaOH to bring the pH to 10. After adjusting the pH with HC1 (2N) to 3.5, the precipitate formed was filtered off and dried, and the title compound was isolated. Yield 1.06g (54.6%) Melting point: 187-190°C. Example 2 3,6.9,12,15-Pentaaza-6.9.12-tris(carboxymethyl)-4,14- dioxo-l,17-diphenylheptadecane DTPA-bis(anhydride) 1.0 g (2.8 mmol) was gradually added to a stirred solution of 2-phenylethylamine 0.68 g (5.6 mmol) in dried chloroform (85 ml) at ambient temperature. The stirred solution was left for 16 hours at ambient temperature. The precipitate which formed was isolated by filtration and dried. The crude product was then purified by reprecipitation as described in Example 1. Yield: 0.89 g (53 %) Melting point: 95-98°C. Example 3 2,5,8,11.14-Pentaaza-5,8,11-tris(carboxy ethyl)-3,13- dioxo-1,15-bis(pyrid-2-yl)pentadecane DTPA-bis(anhydride) 1.0 g (2.8 mmol) was gradually added to a stirred solution of 2-aminomethylpyridine 0.61 g (5.6 mmol) in dried chloroform at ambient temperature. The stirred solution was left for 42 hours at ambient temperature. The precipitate formed was isolated by filtration and dried. Yield: 74.5% Melting point: 107-110°C. Example 4 1.4.7,10.13-Pentaaza-4,7,10-triscarboxymethyl-2,12- dioxo-1,13-bis(N-benzyl-piperidin-4-yl)tridecane DTPA-bis(anhydride) 1.0 g (2.8 mmol) was gradually added to a stirred solution of 4-amino-l-benzylpiperidine 1.07 g (5.6 mmol) in dried chloroform (85 ml) at ambient temperature. The solution was then heated to reflux temperature. The solution was refluxed with stirring overnight under a nitrogen atmosphere. The solution was then evaporated until 25-30 ml remained. Subsequently ether (120ml) was added, and the precipitate was filtered off and dried. Yield: 93.2g Example 5 1,4,7,10,13-Pentaaza-4,7,10-tris(carboxymethyl)-2,12- dioxo-1,13-bis(indan-2-yl)tridecane DTPA-bis(anhydride) 0.88 g (2.48 mmol) was gradually added to a stirred solution of 2-aminoindane 0.66 g (4.955 mmol) in dried acetonitrile (40 ml) at ambient temperature. The solution was heated to reflux temperature (85°C) and refluxed under a nitrogen atmosphere for 4 hours. The reaction mixture was subsequently cooled, and the solution was decanted. The crude solid thereby obtained was dissolved in water with IN NaOH added to bring the pH to 13. After adjusting the pH with HCl (IN) to 3.5, the precipitate formed was filtered off and dried. Yield: 47.2% Example 6 1,4,7,lQ-Tetraaza-4,7-bis(carboxymethyl)-2,9-dioxo-l.10- bis(indan-2-yl)decane EDTA-bis(anhydride) 0.38 g (1.46 mmol) was gradually added to a stirred solution of 2-aminoindane 0.39 g (2.93 mmol) in dried chloroform (30 ml) at ambient temperature. After 24 hours the precipitate formed was isolated by filteration and dried. The crude product was then purified by reprecipitation as described in Example 1. Yield: 0.43 g (56.4%) Melting point: 199.5-202°C Example 7 2,5,8,ll-Tetraaza-5,8-bis(carboxymethyl)-3,10-dioxo- 1,12-diphenyldodecane EDTA-bis(anhydride) 1.0 g (3.9 mmol) was gradually added to a stirred solution of benzylamine 0.83 g (3.9 mmol) in dried chloroform (85 ml) at ambient temperature. The solution was heated to reflux temperature (70°C) and refluxed under a nitrogen atmosphere for 19 hours. The reaction mixture was subsequently cooled, and the precipitate formed was filtered off and dried. Yield: 1.69 g (92.09%) Melting point: 139-141°C Example 8 1,4,7,10-Tetraaza-4,7-bis(carboxymethyl)-2,9-dioxo-l,10- bis(pyrid-2-yl)decane lg (3,9 mmol) EDTA-bis(anhydride) was gradually under stirring to acetonitrile (33 ml) heated to boiling. The mixture was refluxed for 1/2 h and 0.73g (1.1 mmol) 2- aminopyridine dissolved in 7 ml acetonitrile was gradually added. The reaction mixture was refluxed under nitrogen atmosphere for 40 hours, subsequently cooled to ambient temperature and the precipitate formed was filtered off and dried . Yield: 92 . 8% Melting point : 215-217 C . Example 9 1,4.7,10,13-Pentaaza-4.7.10-tris(carboxymethyl)-2,12- dioxo-1,13-bis(N-benzylpiperidin-4-yl)tridecane DTPA-bis(anhydride) 1.0 g (2.8 mmol) was gradually added to a stirred solution of 4-amino-l-benzylpiperidine 1.07 g (5.6 mmol) in dried chloroform (100 ml) at ambient temperature. The stirred solution was left at ambient temperature for 66 hours. Then about 50% of the chloroform was evaporated off. Ether (50 ml) was then added, and the precipitate formed was filtered off and dried. Yield: 92.8% Example 10 1,4,7,10-Tetraaza-4,7-bis(carboxymethyl)-2,9-dioxo-l,10- bis(N-benzylpiperidin-4-yl)decane DTPA-bis(anhydride) 1.0 g (3.9 mmol) was gradually added to a stirred solution of 4-amino-l-benzylpiperidine 1.48 g (7.8 mmol) in dried chloroform (85 ml) at ambient temperature. The stirred solution was left for 18 hours at ambient temperature. The solution was evaporated until 25-30 ml remained. Subsequently ether (2 x 100 ml) was added. The precipitate formed was isolated by filtration and dried. Yield: 91.9% Melting point: 105-111°C. Example 11 3,6.9,12-Tetraaza-6,9-bis(carboxymethyl)-4,11-dioxo- 1.14-diphenyltetradecane EDTA-bis(anhydride) 1.0 g (3.9 mmol) was gradually added to a stirred solution of 2-phenylethylamine 0.9 g (7.8 mmol) in dried acetonitrile (40 ml) at ambient temperature under a nitrogen atmosphere. The solution was heated to reflux temperature (85°C) and refluxed for 17 hours. The reaction mixture was subsequently cooled, and the precipitate formed was isolated by filtration and dried. Yield: 1.7 g (87.8%) Example 12 4,7,10,13.16-Pentaaza-7,10,13-tris(carboxymethyl)-5,15- dioxo-1,19-bis(morpholino)nonadecane DTPA-bis(anhydride) 1.0 g (2.8 mmol) was gradually added to a stirred solution of N-(3-aminopropyl)morpholine 0.81 g (5.6 mmol) in dried chloroform (85 ml) at ambient temperature. The solution was stirred for 27 hours and then refluxed under a nitrogen atmosphere for 69 hours. The solution was evaporated until 25-30 ml remained. Subsequently ether (120ml) was added. The precipitate formed was isolated by filtration and dried. Yield: 93.9% Example 13 2,5,8,11.14-Pentaaza-5,8,11-tris(carboxymethyl)-3,15- dioxo-1,15-bis(pyrid-3-yl) entadecane DTPA-bis(anhydride) 1.0 g (2.8 mmol) was gradually added to a stirred solution of 3-aminomethylpyridine 0.61 g (5.6 mmol) in dried acetonitrile (40 ml) at ambient temperature. The solution was stirred for 84 hours. The precipitate formed was isolated by filtration and dried. Yield: 87.6% Example 14 2,5,8,ll-Tetraaza-5,8-bis(carboxymethyl)-3,lO-dioxo- 1,12- bis(pyrid-3-yl)dodecane EDTA-bis(anhydride) 1.0 g (3.9 mmol) was gradually added to a stirred solution of 3-aminomethylpyridine 0.84 g (7.8 mmol) in dried chloroform (85 ml) at ambient temperature. The precipitate formed was isolated by filtration and dried. Yield: 97.8% Melting point: 212-216°C Example 15 2,5,8,ll-Tetraaza-5,8-bis(carboxymethyl)-3,10-dioxo- 1,12- bis(pyrid-2-yl)dodecane EDTA-bis(anhydride) 1.0 g (3.9 mmol) was gradually added to a stirred solution of 2-aminomethylpyridine 0.84 g (7.8 mmol) in dried chloroform (120 ml) at ambient temperature. The stirred solution was left for 16 hours at ambient temperature. The solution was evaporated until 25-30 ml remained. Subsequently ether (50 ml) was added. The precipitate formed was isolated by filteration and dried. Yield: 98.4% Melting point: 73-81"C. - 22 - Example 16 3,6,9,12-Tetraaza-2 , 13-bis(benzyloxycarbonyl)-6,9- bis(carboxymethyl) -4,11-dioxo-l,14-diphenyltetradecane EDTA-bis(anhydride) (0.4 g, 1.56 mmol) was added in portions to a solution of H-Phe-OBzl-HCl (0.91 g, 3.12 mmol) and triethylamine (0.32 g, 3.12 mmol) in chloroform (50 ml) . The reaction mixture was stirred at ambient temperature for 20 hours before the white precipitated product was collected by filtration and dried under vacuum at 50°C. Yield: 0.83 g (69%) , Melting point: 174-178°C Elemental analysis: calculated: C 65.78 H 6.05, N 7.30 found: C 65.53, H 6.15, N 7.14 1 H NMR (DMSO) : δ 8.32 (d, J 8.06 Hz, 2H) , 7.5-7.08 (m, 20H) , 5.10 (S, 4H) , 4.70-4.50 (m, 2H) , 3.50-2.41 (m, 16H) . Example 17 3 ,6,9,12 ,15-Pentaaza-2 ,16-bis(benzyloxycarbonyl) -6,9,12- tris(carboxymethyl)-4,14-dioxo-l, 17-diphenylheptadecane DTPA-bis(anhydride) (0.56 g, 1.56 mmol) was added in portions to a solution of H-Phe-OBzl-HCl (0.91 g, 3.12 mmol) and triethylamine (0.32 g, 3.12 mmol) in chloroform (50 ml) . The reaction mixture was refluxed under N 2 for 24 hours before the white precipitated product was .collected by filtration and dried under vacuum at 50°C. Yield: 1.1 g (81%) , Melting point: 120-126°C 1 H NMR (DMSO): δ 8.45 (d, J 7.78 Hz, 2H) , 7.50-7.05 (m, 20H) , 5.10 (s, 4H) , 4.70-4.50 (m, 2H) , 3.70-2.60 (m, 22H) . Example 18 3,6,9.12-Tetraaza-2,13-dicarboxy-6,9-bis(carboxymethyl)- 4,11-dioxo-l,14-diphenyltetradecane LiOH (0.34 g, 14.3 mmol) was added to a suspension of EDTA-bis(benzylphenylalanyl)amide (1.1 g, 1.43 mmol) in a mixture of methanol/water (3:1, 44 ml). After 2 hours the TLC showed that the hydrolysis was completed. Methanol was removed under reduced pressure and the reaction mixture acidified to pH 3.5 with 2N HCl. The product was collected by filtration and dried under vacuum at 50"C. Yield: 0.89 g, Melting point: 115-120°C 'H NMR (DMSO): δ 8.22 (d, J 7.4 Hz, 2H) , 7.50-7.08 (m, 1 OH), 4.61-4.35 (m, 2H) , 3.40-2.40 (m, 16H) . Example 19 3.6,9.12,15-Pentaaza-2,16-dicarboxy-6,9,12- tris(carboxymethyl)-4.14-dioxo-l,17-diphenylheptadecane LiOH (0.30 g, 12.7 mmol) was added to a suspension of DTPA-bis(benzylphenylalanyl)amide (1.1 g, 1.27 mmol) in a mixture of methanol/water (3:1, 44 ml). After 2 hours the TLC showed that the hydrolysis was completed. The solvent was removed under reduced pressure and the residue dried under vacuum at 50°C to give 1.04 g of crude product. 1 H NMR (DMSO): δ 8.49 (d, J 1.6 Hz, 2H) , 7.40-7.00 (m, 1 OH), 4.43-4.20 (m, 2H) , 3.61-2.55 (m, 22H) . Example 20 3,6,9,12-Tetraaza-6,9-bis(carboxymethyl)-4,11-dioxo- 1,14-bis(pyrid-2-yl)tetradecane A solution of 2-(2-aminoethyl)pyridine (0.95 g, 7.8 mmol) and EDTA-bis(anhydride) (1.0 g, 3.9 mmol) in 85 ml chloroform was stirred for 4 days at ambient temperature. Most of the chloroform was evaporated. The rest (20-30 ml) was dissolved in 100 ml diethylether to crystallize. The solid product was collected and dried under reduced pressure to yield 88% product. Melting point: 60-64°C Elemental analysis: Calculated: C 56.05 H 6.25 Found: C 55.88 H 6.25 1 H NMR (200 MHz DMS0-d6) δ ppm: 2.66 (s, 4H, t, 4H, J = 7.1 Hz), 3.20 (s, 4H) , 3.33 (s, 4H) , 3.4-4.6 (m, 4H) , 7.1-7.3 (m, 4H), 7.6-7.8 (m, 2H) , 8.10 (t, 2H, 5.7 Hz), 8.50 (d, 2H, J = 4.7 Hz) . Example 21 3,6,9,12,15-Pentaaza-6,9,12-tris(carboxymethyl)-4,14- dioxo-1,17-bis( yrid- -y1)heptadecane 2-(2-Aminoethyl)pyridine (0.68 g, 5.6 mmol) and DTPA- bis(anhydride) (1.0 g, 2.8 mmol) were dissolved in 85 ml chloroform. The mixture was stirred for 22 hours at ambient temperature. The solid product was separated from the solution by filtration before being dried in vacuum to give 56% product. Melting point: 110-118°C Elemental analysis: Calculated: C 53.36 H 6.18 Found: C 57.58 H 6.46 1 H NMR (200 MHz DMSO-d6) δ ppm: 2.8-3.8 (m, 30H) , 7.1-7.4 (m, 4H) , 7 . 6-7 . 8 (m, 2H) , 8 . 1-8 . 3 (m, 2H) , 8 . 49 (d, 2H, 4 . 8 Hz ) . Example 22 3.6,9,12-Tetraaza-2.13-dicarboxy-6.9-bis(carboxymethyl)- 4,ll-dioxo-l,14-bis(indol-3-yl)tetradecane Triethylamine (0.39 g, 3.9 mmol), tryptophanmethylester (HCl) and EDTA-bis(anhydride) (0.5 g, 1.95 mmol) were dissolved in 70 ml chloroform. The suspension was stirred for 21 hours at ambient temperature. The solid product was collected by filtration and dried in vacuum to give 83% yield. Melting point: 84-91°C Elemental analysis: Calculated: C 53.30 H 4.46 Found: C 58.94 H 5.83 1 H NMR (200 MHz DMSO-d6) <5 ppm: 2.26 (3, 4H) , 3.0-3.4 (m, 14H) , 3.60 (s, 6H) , 4.5-4.7 (m, 2H) , 6.95-7.15 (m, 4H) , 7.19 (d, 2H, J = 1.8 Hz), 7.37 (d, 2H, J •= 7.5 Hz) , 7.52 (d, 2H, 7.7 HZ), 8.27 (d, 2H, J = 7.7 Hz) ' . Example 23 3,6.9.12-Pentaaza-2,16-dicarboxy-6,9.12- tris(carboxymethyl)-4,14-dioxo-l,17-bis(indol-3- y1)heptadecane Triethylamine (0.57 g, 5.6 mmol), tryptophanmethylester (HCl) (1.43 g, 5.6 mmol) and DTPA-bis(anhydride) (1.000 g, 2.8 mmol) were dissolved in 100 ml chloroform. The mixture was refluxed in a nitrogen atmosphere for 3 days. Most of the chloroform was removed (20-30 ml left) . 100 ml diethylether was added to the concentrated solution. The crystalline product was collected by filtration, dissolved in basic aqueous solution and recrystallized with 0.5 M HCl. The identity of the product as the title compound was verified by 1 H and 13 C NMR. Example 24 3,6.9,12-Tetraaza-2,13-bis(methyloxycarbonyl)-6,9- bis(carboxymethyl)-4,11-dioxo-l,14-bisfindol-3- yl)tetradecane Lithium hydroxide (14.4 mg, 0.61 mmol) was dissolved in a 4.5 ml mixture of MeOH/H 2 0(3:l) . 3,6,9,12-Tetraaza- 2,13,-bis(methyloxycarbonyl)-6,9-bis(carboxymethyl)- 4,ll-dioxo-l,14-bis(indol-3-yl)tetradecane (60.0 mg, 8.7 x 10 "2 mmol) was added and the solution was stirred for 8 hours. Methanol was removed, 2 ml water was added and the pH was adjusted to 3.5 (0.5 M HCl). The solid product was collected and dried in vacuo for 12 hours. The identity of the product as the title compound was verified by -Η. NMR. Example 25 3,6,9,12,15-Pentaaza-2,16-bis(methyloxycarbonyl)-6,9,12- tris(carboxymethyl)-4,14-dioxo-l,17-bis(indol-3- yl)heptadecane Lithium hydroxide (0.32 g, 13.4 mmol) was dissolved in a mixture of MeOH/H 2 0(3:1) . 3,6,9,12,15-Pentaaza-2,16,- bis(methyloxycarbonyl)-6,9,12-tris(carboxymethyl)-4,14- dioxo-1,17-bis(indol-3-yl)heptadecane (1.33 g, 1.67 mmol) was added and the solution was stirred for 6 hours at ambient temperature. Methanol was evaporated and 10 ml water was added to the residual. The pH was adjusted to 3.5 with 0.5 M HCl. The solid product was collected by filtration and dried to give 18% product. Melting point: 158-160°C Elemental analysis: Calculated: C 55.86 H 5.80 Found: C 56.45 H 5.67 1 H NMR (200 MHz, DMSO-d6) δ ppm: 2.5-3.6 (m, 22H) , 4.4- 4.7 (m, 2H) , 6.9-7.2 (m, 4H) , 7.22 (s, 2H) , 7.36 (d, 2H, J = 7.5 Hz), 7.56 (d, 2H, J - 7.4 Hz), 8.27 (d, 2H, J = 8.1 Hz) . Example 26 General procedure for complexation with Gadolinium (20 mM solution) GdCl 3 (1 mmol) in 4 ml water was dropwise added to a solution of a chelant of formula I (where n is 1) (1 mmol) in 30 ml water, while the pH was kept at 5-6 by adding 1 N NaOH. After addition the mixture was stirred for 1/2 hour and diluted with water to 50 ml. Example 27 General procedure for complexation with Manganese (50 mM solution) MnCl 2 (1.25 mmol) in 3 ml water was dropwise added to a solution of a chelant of formula I (where n is 0) (1.25 mmol) in 15 ml water, while the pH was kept at 5-6 by adding IN NaOH. After addition the mixture was stirred for 1/2 hour and diluted with water to 25 ml. - 28 - Example 28 Relaxivitv of Gd and Mn chelates in water and Autonorm measured at 37"C, 20 MHz on an IBM PC/20 Series NMR Analyzer (Minispec) .

Claims: Claims 1. A compound of formula I HOOC CH 2 CH 2 COOH NCH 2 CH 2 [NCH 2 CH 2 ] _N (I) R 1 OCCH 2 I CH 2 COR 1 CH 2 COOH (wherein n is 0 or 1; one group R 1 is a group NR 1 R 14 where R 11 is a hydroxyl or alkoxy group or a group -L-Cy or -O-L-Cy, and R 14 is a hydrogen atom, an alkyl group or a group -L-Cy, and the other group R 1 is a hydroxyl group or a group NR 11 R 14 ; L is a bond or a straight-chain or branched saturated or unsaturated alkylene group optionally interrupted by a carbocyclic or heterocyclic saturated or unsaturated group and optionally attached to the Cy group by a peptide or carbonyl link and optionally substituted by further Cy groups or by aminocarbonyl, acyl or acylamino groups; and Cy is a cyclic lipophilic group; with the provisos that in any NR 11 R 14 group one of R 11 and R 14 comprises a L-Cy group and that where n is 1 at least one R 1 group is other than phenylamine, benzylamine, or methoxybenzylamine) and metal chelates and salts thereof. 2. A compound as claimed in claim 1 containing at least one Cy group which is a carbocyclic or heterocyclic saturated or unsaturated group itself optionally carrying one or more fused carbocyclic or heterocyclic saturated or unsaturated rings and optionally substituted by halogen atoms, alkyl, alkylamino, dialkylamino, carbamoyl, N-alkylcarbamoyl, acetamido, N-alkylacetamido or carbocyclic or heterocyclic saturated or unsaturated groups. 3. A compound as claimed in either of claims 1 and 2 containing at least one Cy group selected from optionally substituted benzene, pyridine, pyrimidine, pyrazine, 1,3-oxazine, 1,4-oxazine, 1,3-thiazine, 1,4- thiazine, pyrrole, imidazole, 1,3-oxazole, 1,3-thiazole, furan, thiophene, piperidine, piperazine, orpholine, perhydro-l,4-thiazine and pyrrolidine rings. 4. A compound as claimed in any one of claims 1 to 3 containing at least one Cy group selected from groups of formula la to Ie (lo) (where R 3 to R 8 is each independently a bond or a hydrogen or halogen atom or an alkyl, alkylamino, dialkylamino, carbamoyl, N-alkylcarbamoyl, acetamido or N-alkylacetamido group or two adjacent groups from R 3 to R 8 together form a C 2 . 5 alkylene or azaalkylene bridge, the point of attachment to L being a carbon of said bridge or one of said groups R 3 to R 8 ; X is nitrogen or CH and Y is CH or nitrogen; X' is CH 2 , NH, oxygen, sulphur or a bond; X" is nitrogen, oxygen or sulphur and Y" is CH or nitrogen; and R 9 is a bond or hydrogen, alkyl or aralkyl) . 5. A compound as claimed in any one of claims 1 to 4 containing at least one group LCy of formula -(CHR 10 ) k -(CO) a -(NR 10 ) b -(CO) C -R 10 where k is 0-10; a, b and c are 0 or 1, the sum of a and c being 0 or 1; each R 10 is a hydrogen atom, an alkyl group, an optionally esterified carboxyl group or a group Cy, at least one being a group Cy, and one or more CHR 10 moieties may optionally be replaced by a 5-7 membered saturated homo or heterocyclic ring. 6. A compound as claimed in any one of claims 1 to 5 wherein at least one group R 1 is a group NR 11 R 14 wherein R 11 is a group -L-Cy and R 14 is a hydrogen atom or an alkyl group. 7. A compound as claimed in any one of claims 1 to 6 being a compound of formula II HOOCCH 2 NCH 2 CH 2 [NCH 2 CH 2 ] n NCH 2 COOH (ID R 13 NR 15 COCH 2 CH 2 COOH CH 2 CONR 15 R 13 (where n is 0 or 1, R 5 is hydrogen or methyl and R 13 is a group selected from benzyl, 2-phenyl-ethyl, 1-phenyl-ethyl, pyrid-4-yl, pyrid-3-yl, pyrid-2-yl, 3- morpholino-propyl, N-benzyl-piperidin-4-yl and indanyl groups and iodinated such groups) or a metal chelate or salt thereof. 8. A compound as claimed in any one of claims 1 to 7 being a metal chelate of a compound of formula I, said metal being a paramagnetic ion of an element of atomic number 21-29, 42, 44 or 57-71. 9. A compound as claimed in claim 8 being a chelate of Gd, Mn or Dy. 10. A therapeutic or diagnostic composition comprising a compound of formula I or metal chelate thereof as defined in any one of claims 1 to 9 or a physiologically tolerable salt thereof together with at least one pharmaceutical or veterinary carrier or excipient. 11. A process for the preparation of compound, as claimed in claim 1 said process comprising reacting EDTA or DTPA or an activated or protected derivative thereof with an amine of formula III HNR 11 'R 14 ' (III) where R 11 ' and R 14 ' are groups R and R 14 as defined in claim 1 or protected such groups, followed where desired by deprotection, metallation or salt formation. 12. A method of generating enhanced images of the human or non-human animal body, which method comprises administering to said body a metal chelate of a compound of formula I as defined in claim 1 or a physiologically tolerable salt thereof and generating an X-ray, MR-diagnostics, ultrasound or scintigraphic image of at least a part thereof. 13. A method of radiotherapy practised on the human or non-human animal body, which method comprises administering to said body a chelate of a radioactive metal species with a chelating agent of formula I as defined in claim 1 or a physiologically tolerable salt thereof. 14. A method of heavy metal detoxification practised on the human or non-human animal body, which method comprises administering to said body a chelating agent which is a salt of a compound of formula I as defined in claim 1 with a physiologically acceptable counterion. 15. The use of compounds as claimed in claim 1 for the manufacture of diagnostic or therapeutic agents for use in methods of image generation, detoxification or radiotherapy practised on the human or non-human animal body.

Inventors: DUGSTAD HARALD, KLAVENESS JO, RONGVED PAAL, STRANDE PER, DUGSTAD, HARALD, KLAVENESS, JO, RONGVED, PAAL, STRANDE, PER
Applicants: COCKBAIN JULIAN R M, NYCOMED AS, COCKBAIN, JULIAN, RODERICK, MICHAELSON
Application year: 1991
Main classification: A61K31
IPC codes: A61K31, A61K49, A61P39, C07C229, C07C237, C07D209, C07D211, C07D213, C07D295