WO1995032004A1

WO1995032004A1 - Functionalized bicyclo[2.2.1] heptane and [2.2.2] octane system as preorganized ligands for imaging applications

Info

Publication number: WO1995032004A1
Application number: PCT/US1994/003764
Authority: WO
Inventors: Raghavan Rajagopalan
Original assignee: Mallinckrodt Medical, Inc.
Priority date: 1994-05-20
Filing date: 1994-05-20
Publication date: 1995-11-30
Also published as: AU7014394A

Abstract

The invention relates to magnetic resonance imaging. In particular, the invention relates to compounds of general structure (I), wherein R1 is selected from the group consisting of hydrogen, C1-C8 alkyl, hydroxy, C1-C8 alkoxy, C1-C8 hydroxyalkyl, C1-C8 acyl, C6-C10 aryl, and C6-C10 aryloxy; R2, R3 and R4 may be the same or different and are selected from the group consisting of hydrogen, C1-C8 alkyl, C1-C8 hydroxyalkyl, C1-C8 alkoxyalkyl, -CH2CO2Y and CH2CONR5R6 where R5 and R6 may be the same or different and are selected from the group consisting of hydrogen, C1-C8 alkyl, C1-C8 hydroxyalkyl and C1-C8 alkoxyalkyl; R5 and R6 may form a 5- or 6-membered carbocyclic ring optionally containing singularly or in combination nitrogen, oxygen or sulfur; m, n and p may be the same or different and are selected from an integer from 0 to about 6; X is selected from the group consisting of -CH2-, -O-, -S-, -SO2-, -CH2CH2-, -CH2O-, -CH2S-, -CH2SO2-, CH2NR7 and -N-R7-, where R7 is selected from the group consisting of hydrogen, hydroxy, C1-C8 alkyl, C1-C8 hydroxyalkyl and C1-C8 alkoxyalkyl and compositions comprising the compound.

Description

FUNCTTONΑT.TZED BICYCLO \2 .2.11 HEPTANE AND f2. .21 OOTA F. SYSTEMS AS PREORGANIZED LIGANDS FOR IMAGING APP IC IONS

FTE D OF THE INVENTION

This invention relates to magnetic resonance imaging (MRI) , x-ray imaging, and radiophar aceuticals. More particularly the invention relates to methods and compositions for enhancing MRI, x-ray imaging, and radiopharmaceuticals .

BAO OROTTND OF THE INVENTION

The use of contrast agents in diagnostic medicine is rapidly growing. In X-ray diagnostics, for example, increased contrast of internal organs, such as the kidneys, the urinary tract, the digestive tract, the vascular system of the heart (angiography) , and so forth is obtained by administering a contrast agent which is substantially radiopaque. In conventional proton MRI diagnostics, increased contrast of internal organs and tissues may be obtained by administering compositions containing paramagnetic metal species which increase the relaxivity of surrounding protons. In ultrasound diagnostics, improved contrast is obtained by administering compositions having acoustic impedances different than that of blood and other tissues.

The recently developed technique of MRI encompasses the detection of certain atomic nuclei utilizing magnetic fields and radio-frequency radiation. It is similar in some respects to X-ray computed tomography (CT) in providing a cross-sectional display of the body organ anatomy with excellent resolution of soft tissue detail. As currently used, the images produced constitute a map of the proton density distribution , the relaxation times, or both, in organs and tissues. The technique of MRI is advantageously non-invasive as it avoids the use of ionizing radiation.

While the phenomenon of MRI was discovered in

1945, it is only recently that it has found application as a means of mapping the internal structure of the body as a result of the original suggestion of Lauterbur (Nature. 2_.12_/ 190-191 [1973] ) . The fundamental lack of any known hazard associated with the level of the magnetic and radio-frequency fields that are employed renders it possible to make repeated scans on vulnerable individuals. In addition to standard scan planes (axial, coronal, and sagittal) , oblique scan planes can also be selected.

With an MRI experiment, the nuclei under study in a sample (e.g. protons) are irradiated with the appropriate radio-frequency (RF) energy in a highly uniform magnetic field. These nuclei, as they relax, subsequently emit RF at a sharp resonance frequency. The resonance frequency of the nuclei depends on the applied magnetic field.

According to known principles, nuclei with appropriate spin, when placed in an applied magnetic field (B, expressed generally in units of gauss or Tesla [10⁴ gauss] ) align in the direction of the field. In the case of protons, these nuclei precess at a frequency, f, of 42.6 MHz, at a field strength of 1 Tesla. At this frequency, an RF pulse of radiation will excite the nuclei and can be considered to tip the net magnetization out of the field direction, the extent of this rotation being determined by the pulse duration and energy. After the RF pulse, the nuclei "relax" or return to equilibrium with the magnetic field, emitting radiation at the resonant frequency. The decay of the emitted radiation is characterized by two relaxation times, i.e., T_ , the spin-lattice relaxation time or longitudinal relaxation time, that is, the time taken by the nuclei to return to equilibrium along the direction of the externally applied magnetic field, and T₂, the spin-spin relaxation time associated with the dephasing of the initially coherent precession of individual proton spins. These relaxation times have been established for various fluids, organs and tissues in different species of mammals.

In MRI, scanning planes and slice thicknesses can be selected. This selection permits high quality transverse, coronal and sagittal images to be obtained directly. The absence of any moving parts in MRI equipment promotes high reliability. It is believed that MRI has a greater potential than CT for the selective examination of tissue characteristics in view of the fact that in CT, X-ray attenuation coefficients alone determine image contrast, whereas at least five separate variables (T_lf T₂, proton density, pulse sequence and flow) may contribute to the MRI signal. For example, it has been shown (Damadian, Science. 121, 1151 [1971] ) that the values of the T_x and T₂ relaxation in tissues are generally longer by about a factor of two (2) in excised specimens of neoplastic tissue compared with the host tissue.

By reason of its sensitivity to subtle physico- chemical differences between organs and/or tissues, it is believed that MRI may be capable of differentiating different tissue types and in detecting diseases which induce physicochemical changes that may not be detected by X-ray or CT which are only sensitive to differences in the electron density of tissue.

As noted above, two of the principal imaging parameters are the relaxation times, T_x and T₂. For protons (or other appropriate nuclei) , these relaxation times are influenced by the environment of the nuclei,

(e.g. , viscosity, temperature, and the like) . These two relaxation phenomena are essentially mechanisms whereby the initially imparted radio-frequency energy is dissipated to the surrounding environment . The rate of this energy loss or relaxation can be influenced by certain other nuclei which are paramagnetic . Chemical compounds incorporating these paramagnetic nuclei may substantially alter the T_ and T₂ values for nearby protons. The extent of the paramagnetic effect of a given chemical compound is a function of the environment.

In general, paramagnetic species such as ions of elements with atomic numbers of 21 to 29, 42 to 44 and 58 to 70 have been found effective as MRI image contrasting agents. Examples of suitable ions include chromium(III) , manganese (II) , manganese (III) , iron(II) , iron (III) , cobalt (II) , nickel (II) , copper (II) , praseodymium (III) , neodymium(III) , samarium (III) , and ytterbium (III) . Because of their very strong magnetic moments, gadolinium (III) , terbium (III) , dysprosium (III) , holmiu (III) and erbium (III) are preferred. Gadoliniu (III) ions have been particularly preferred as MRI contrasting agents.

Typically, paramagnetic ions have been administered in the form of complexes with organic complexing agents. Such complexes provide the paramagnetic ions in a soluble, non-toxic form, and facilitate their rapid clearence from the body following the imaging procedure. Gries et al . , U.S. Patent

4,647,447, disclose complexes of various paramagnetic ions with conventional aminocarboxylic acid complexing agents. A preferred complex disclosed by Gries et al . is • the complex of gadolinium(III) with diethylenetriamine- pentaacetic acid ("DTPA") .

Paramagnetic ions, such as gadolinium(III) , have been found to form strong complexes with DTPA, ethylenediamine-tetraacetic acid ("EDTA") , and with tetraazacyclododecane-N,N' ,N" ,N" ' -tetraacetic acid ("DOTA") .

These complexes do not dissociate substantially in physiological aqueous fluids. The gadolinium complex of DTPA has a net charge of -2, whereas the gadolinium complex of EDTA or DOTA has a net charge of -1, and both are generally administered as soluble salts. Typical salts are sodium and N-methylglucamine. The administration of salts is attended by certain disadvantages. These salts can raise the in vivo ion concentration and cause localized disturbances in osmolality, which in turn, can lead to edema and other undesirable reactions.

Efforts have been made to design new ionic and neutral paramagnetic metal complexes which avoid or minimize the above mentioned disadvantages. In general, this goal can be achieved by converting one or more of the free carboxylic acid groups of the complexing agent to neutral, non-ionizable groups. For example, S.C. Quay, in U.S. Patents 4,687,658 and 4,687,659, discloses alkylester and alkylamide derivatives, respectively, of DTPA complexes. Similarly, published Dean et al . , U.S. Patent Number 4,826,673 discloses mono- and polyhydroxyalkylamide derivatives of DTPA and their use as complexing agents for paramagnetic ions. It can also be achieved by covalent attachment of organic cations to the complexing agent in such a manner that the sum of positive and negative charges in the resulting metal complex is zero.

The nature of additional substituents in the complexing agent can have a significant impact on tissue specificity. Hydrophilic complexes tend to concentrate in the interstitial fluids, whereas lipophilic complexes tend to associate with cells. Thus, differences in hydrophilicity can lead to different applications of the compounds. See, for example, Weinmann et al. , AJR. 142, 679 (Mar. 1984) and Brasch, et al . , AJR. 142. 625 (Mar. 1984) .

Finally, toxicity of paramagnetic metal complexes is greatly affected by the nature of the complexing agents. In vivo release of free metal ions from the complex is a major cause of toxicity. Four principal factors are important in the design of chelates for making paramagnetic metal complexes that are highly stable in vivo and less toxic. The first three factors are thermodynamic in nature whereas the fourth involves chelate kinetics. The first factor is the thermodynamic stability constant of the metal-ligand. The thermodynamic stability constant indicates the affinity that the totally unprotonated ligand has for a metal. The second factor is the conditional stability constant which takes into account the pH and is important when considering stability under physiological pH. The selectivity of the ligand for the paramagnetic metal over other endoenous metal ions such as zinc, iron, magnesium and calcium is the third factor. In addition to the three thermodynamic considerations, complexes with structural features that make in vivo transmetallation reactions much slower than their clearance rates would be ■predicted to have low toxicities. Therefore, in vivo reaction kinetics are a major factor in the design of stable complexes. See, for example, Cacheris et al. ,

Magnet c Resonance Imaging. 8:467 (1990) and Oksendal, et

A need continues to exist for new and structurally diverse compounds for use as imaging agents There is a further need to develop highly stable complexes with good relaxivity and osmolar characteristics.

SUMMARY OF THE INVENTION

The present invention provides new and structurally diverse compositions comprising compounds of the general formula:

wherein R_x is selected from the group consisting of hydrogen, alkoxy, Ci-Cg hydroxyalkyl,

acyl, C₆-C₁₀ aryl, and C₆-C₁₀ aryloxy; R₂, R₃ and R₄ may be the same or different and are selected from the group consisting of hydrogen,

alkyl,

alkoxyalkyl, -CH₂C0₂H and CH₂CONR₅R₆ where R₅ and R₆ may be the same or different and are selected from the group consisting of hydrogen,

alkyl,

alkoxyalkyl, R₅ and R₆ may form a 5 or 6 membered carbocyclic ring optionally containing singularly or in combination nitrogen, oxygen or sulfur; m, n and p may be the same or different and are selected from an integer from zero to about six; X is selected from the group consisting of -CH₂-, -0-, -S-, - S0₂-, -CH₂CH₂-, -CH₂0-, -CH₂S-, -CH₂S0₂-, CH₂NR₇ and -N-R₇-, where R₇ is selected from the group consisting of hydrogen, hydroxyl, C_-C_B alkyl,

C₈ alkoxyalkyl and compositions comprising the compound.

Also provided are compositions comprising complexes of the compounds with metal ions of the general formula

wherein R_x is selected from the group consisting of hydrogen, C-_.-C₈ alkyl, hydroxy, C^Cg alkoxy, C-_.-C,, hydroxyalkyl,

acyl, C₆-C₁₀ aryl, and C₆-C₁₀ aryloxy; R₂ R₃ and R₄ may be the same or different and are selected from the group consisting of hydrogen, C^Cg alkyl, Ci-C₈ hydroxyalkyl,

alkoxyalkyl, -CH₂C0₂Y and CH₂CONR₅R₆ where R₅ and R₆ may be the same or different and are selected from the group consisting of hydrogen, Ci-Cg alkyl,

hydroxyalkyl and Ci-Cg alkoxyalkyl; R₅ and R₆ may form a 5 or 6 me bered carbocyclic ring optionally containing singularly or in combination nitrogen, oxygen or sulfur; m, n and p may be the same or different and are selected from an integer from zero to about six; X is selected from the group consisting of -CH₂-, -0-, -S-, -

S0₂-, -CH₂CH₂-, -CH₂0-, -CH-.S-, -CH₂S0₂-, CH₂NR₇ and -N-R,-, where R₇ is selected from the group consisting of hydrogen, hydroxyl, C_x-C₈ alkyl, C._.-C_β hydroxyalkyl and C_ - C₈ alkoxyalkyl; and Y is a metal ion equivalent and/or a physiologically acceptable cation of an inorganic or organic base.

Compositions comprising the above formulas wherein Y is a radioactive metal ion, a paramagnetic ion, or a metal ion capable of absorbing x-rays are also provided for use as radiopharmaceuticals, magnetic resonance imaging, and x-ray contrast agents, respectively.

Diagnostic compositions comprising the compounds of the invention are also provided. Methods of performing diagnostic procedures with compositions of the invention are also disclosed. The methods comprise administering to a patient an effective amount of the compositions of the invention and subjecting the patient to an imaging procedure.

DETAILED DESCRIPTION The compositions of the invention are suitable for use with a variety of modalities including x-rays, magnetic resonance imaging and radiopharmaceuticals.

The functionality of the R groups of the compositions of the invention afford the additional capability of derivatization to biomolecules and synthetic polymers. Biomolecule refers to all natural and synthetic molecules that play a role in biological systems. Biomolecules include hormones, amino acids, peptides, peptidomimetics, proteins, deoxyribonucleic acid (DNA) ribonucleic acid (RNA) , lipids, albumins, polyclonal antibodies, receptor molecules, receptor binding molecules, monoclonal antibodies and aptamers. Specific examples of biomolecules include insulins, prostaglandins, growth factors, liposomes and nucleic acid probes. Examples of synthetic polymers include polylysine, aborols, dendrimers, and cyclodextrins. The advantages of using biomolecules include enhanced tissue targeting through specificity and delivery. Coupling of the chelating moieties to biomolecules can be accomplished by several known methods (e.g., Krejcarek and Tucker Rπo hem. Riophys. Res. Comm. 30, 581 (1977) ;

Hnatowich, et al. Science. 220, 613 (1983). For example, a reactive moiety present in one of the R groups is coupled with a second reactive group located on the biomolecule. Typically, a nucleophilic group is reacted with an electrophilic group to form a covalent bond between the biomolecule and the chelate. Examples of nucleophilic groups include amines, anilines, alcohols, phenols, thiols and hydrazines. Electrophilic group examples include halides, disulfides, epoxides, maleimides, acid chlorides, anhydrides, mixed anhydrides, activated esters, imidates, isocyanates and isothiocyanates. And finally, the compositions of the invention should provide the additional advantage of being kinetically inert .

Examples of suitable alkyl groups for use with the invention include methyl, ethyl, propyl, isopropyl, butyl, cyclohexyl, heptyl and octyl . Suitable alkoxy groups include methoxy, ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy and octoxy. Hydroxyalkyl groups suitable for use with the invention include both mono and poly hydroxyalkyls such as hydroxyethyl, 2-hydroxypropyl, 2,3- dihydroxypropyl, 2,3,4-1rihydroxybutyl, tris (hydroxymethyl)methyl and 2-hydroxy-1-hydroxymethyl- ethyl. Suitable alkoxyalkyl groups include methoxymethyl, 2, 3-dimethoxypropyl, tris (methoxymethyl)methyl, and 2-methoxy-1-methoxymethyl- ethyl .

Examples of preferred compounds of the invention include N,N,N' ,N' ,N' ^■ ,N' ' -Hexa (carboxymethyl) -2,3- aminomethyl-5-amino-6-hydroxy-bicyclo [2.2.2] octane, N,N,N' ,N' ,N' ' ,N' ' -Hexa (carboxymethyl) -2,3-aminomethyl-5- amino-6-hydroxy-7-oxabicyclo [2.2.1] heptane, N,N-,N' '- Tris (carboxymethyl) -N,N^* ,N^* ' -tris [2- [ (2- methoxyethyl) amino] -2-oxoethyl-2, 3-aminomethyl-5-amino-6- hydroxy-bicyclo[2.2.2]octane, N,N' ,N' ' - Tris (carboxymethyl) -N,N' ,N' ' -tris (2-hydroxyethyl) -2,3- aminomethyl-5-amino-6-hydroxy-bicyclo[2.2.2]octane, N- (2- Hydroxyethyl) -N' ,N' ' ,N' ' ' -tris (carboxymethyl) -2,3- aminomethyl-5-amino-6-hydroxy-7-azabicyclo [2.2.1] heptane, N,N,N' ,N' ,N",N"-Hexa(carboxymethyl) -2, 3-aminomethyl-5- amino-6-hydroxy-7-azabicyclo [2.2.1] heptane, N,N' ,N"-Tris (carboxymethyl) -N,N' ,N"-tris [2- [ (2- methoxyethyl) amino] -2-oxoethyl] -2, 3-aminomethyl-5-amino-

6-hydroxy-7-oxabicyclo [2.2.1] heptane, N,N' ,N"-Tris (carboxymethyl) -N,N' ,N"-tris [2- [ (2- methoxyethyl) amino] -2-oxoethyl] -2,3-aminomethyl-5-amino- 6-hydroxy-7-azabicyclo [2.2.1]heptane, N,N' ,N"-Tris (carboxymethyl) -N,N' ,N"-tris (2-hydroxyethyl) -

2,3-aminomethyl-5-amino-6-hydroxy-7- oxabicyclo [2.2.1]heptane,

N,N' ,N"-Tris (carboxymethyl) -N,N' ,N"-tris (2-hydroxyethyl) - 2, 3-aminomethyl-5-amino-6-hydroxy-7- azabicyclo [2.2.1] heptane,

N,N' ,N"-Tris (carboxymethyl) -2,3-aminomethyl-5-amino-6- hydroxy-7-oxabicyclo [2.2.1] heptane, and N,N' ,N"-Tris (carboxymethyl) -2, 3-aminomethyl-5-amino-6- hydroxy-bicyclo [2.2.2] octane. These compounds are generally referred to as ligands.

Complexes of the novel ligands or compounds of the invention with one or more central metal ions or metal ion equivalents such as paramagnetic metals praseodymium(III) , neodymium(III) , samarium(III) , ytterbium(III) terbium(III) , dysprosium(III) , holmium(III) , erbium(III) , iron(I), iron(III) , manganese (II) , manganese (III) , gadolinium(III) , chromium(III) , cobalt(II) and nickel(II) are useful for enhancing magnetic resonance images. While such metal ions are themselves paramagnetic in nature and capable of altering the magnetic resonance signal characteristics of body tissues, organs or fluids, they may exhibit significant toxicity when administered in the form of ionic salts. However, novel complexes of the invention are relatively or substantially nontoxic and therefore useful for enhancing magnetic resonance images by favorably altering relaxation times T_ and T₂ and affording improved contrast between normal and diseased tissues or organs.

The preferred complexes of the invention are those formed from the above ligands and iron(II) , iron (III) , manganese (II) , manganese (III) and gadolinium(III) as the central metal ion or ions. Depending upon the particular ligand employed and the particular central metal ion used, the complexes formed may be neutral, ionic, cationic, or zwitterionic in nature, or they may be negatively charged. The neutral complexes are generally preferred and generally appear to exhibit relatively lower toxicity as compared to ionic or negatively charged complexes. The negatively charged complexes formed by the ligands and central metal ions enumerated above may be further complexed with one or more cations of an inorganic or organic base which are physiologically tolerated. Examples of cations for further complexing include sodium, potassium, calcium, and salts of N- methylglucamine, and diethanolamine .

Examples of preferred compounds of the invention and one or more central metal ions (i.e., complexes) include N, N,N,N' ,N' ,N' ' ,N' ' -Hexa (carboxymethyl) -2, 3-aminomethyl- 5-amino-6-hydroxy-bieyelo [2.2.2] octane, gadolinium complex, trisodium salt, N,N' ,N' ' -Tris (carboxymethyl) - N,N' ,N' ^■ -tris [ (2-methoxyethyl) amino] -2-oxoethyl] -2,3- aminomethyl-5-amino-6-hydroxy-bicyclo [2.2.2] octane, gadolinium complex, N,N',N" -Tris (carboxymethyl) - N,N' ,N' ' -tris (2-hydroxyethyl) -2, 3-aminomethyl-5-amino-6- hydroxy-bicyclo [2.2.2] octane dysprosium complex, N,N,N' ,N' ,N" ,N"-Hexa (carboxymethyl) -2, 3-aminomethyl-5- amino-6-hydroxy-7-oxabicyclo [2.2.1] heptane, gadolinium complex, trimeglumine salt,

N,N,N' ,N' ,N",N"-Hexa (carboxymethyl-2, 3-aminomethyl-5- amino-6-hydroxy-7-azabicyclo [2.2.1] heptane, iron complex, trilithium salt,

N,N' ,N"-Tris (carboxymethyl) -N,N' ,N"-tris[2- [(2- methoxymethyl) amino] -2-oxoethyl] -2, 3-aminomethyl-5-amino- 6-hydroxy-7-oxabicyclo [2.2.1] heptane, gadolinium complex, N,N' ,N"-Tris (carboxymethyl) -N,N' ,N"-tris [2- [ (2- methoxyethyl) amino] -2-oxoethyl] -2,3-aminomethyl-5-amino-

6-hydroxy-7-azabicyclo [2.2.1] heptane, dysprosium complex, N,N' ,N"-Tris (carboxymethyl) -N,N' ,N"-tris (2-hydroxyethyl) - 2,3-aminomethyl-5-amino-6-hydroxy-7- oxabicyclo [2.2.1] heptane, gadolinium complex, N,N' ,N"-Tris (carboxymethyl) -N,N' ,N"-tris (2-hydroxyethyl) -

2, 3-aminomethyll-5-amino-6-hydroxy-7- azabicyclo [2.2.1]heptane, holmium complex, N,N' ,N"-Tris (carboxymethyl-2, 3-aminomethyl-5-amino-6- hydroxy-7-oxabicyclo [2.2.1] heptane, gadolium complex, and N,N' ,N"-Tris (carboxymethyl) -2, 3-aminomethyl-5-amino-6- hydroxy-bicyclo [2.2.2] octane, gadolinium complex.

In addition to their utility in magnetic resonance imaging procedures, the compositions of the invention can also be employed for delivery of either radiopharmaceuticals or heavy metals for x-ray contrast into the body. For use in diagnostic and therapeutic radiopharmaceuticals the complexed metal ion must be radioactive. Radioisotopes of the elements technetium, rhenium, indium, gallium, copper, yttrium, samarium and holmium are suitable. For use as X-ray contrast applications the complexed metal ion must be able to absorb adequate amounts of the X-rays. These metal ions are generally refered to as radioopaque. Suitable elements for use as the radioopaque metal ion include lead, bismuth, gadolinium, dysprosium and praseodymium.

Examples of preferred compounds for radiopharmaceuticals are N,N,N' ,N" ,N"- Hexa (carboxymethyl) -2, 3-aminomethyl-5-amino-6-hydroxy- bicyclo [2.2.2] octane, technetium complex, sodium salt, N,N' ,N"-Tris (carboxymethyl) -N,N' ,N"-tris [2- [ (2- methoxyethyl) amino] -2-oxoethyl] -2 , 3-aminomethyl-5-amino- 6-hydroxy-bicyclo [2.2.2] octane, yttrium complex, N,N' ,N"-Tris (carboxymethyl) -N,N' ,N"-tris (2-hydroxyethyl) -

2, 3-aminomethyl-5-amino-6-hydroxy-bicyclo [2.2.2] octane, indium complex,

N,N,N' ,N* ,N" ,N"-Hexa (carboxymethyl) -2, 3-aminomethyl-5- amino-6-hydroxy-7-oxabicyclo [2.2.1] heptane, rhenium complex, meglumine salt, and

N,N' ,N"-Tris (carboxymethyl) -N,N' ,N"-tris [2- [(2- methoxyethyl) amino] -2-oxoethyl] -2, 3-aminomethyl-5-amino- 6-hydroxy-7-oxabicyclo [2.2.1] heptane, gallium complex.

Examples of preferred compounds for x-ray contrast agents are N,N,N' ,N' ,N" ,N"-Hexa (carboxymethyl) -2, 3- aminomethyl-5-amino-6-hydroxy-bicyclo [2.2.2] octane, lead complex, disodium salt, N,N,N' ,N' ,N",N"-Hexa (carboxymethyl) -2, 3-aminomethyl-5- amino-6-hydroxy-7-oxabicyclo [2.2.1] heptane, bismuth complex, meglumine salt,

N,N' ,N"-Tris (carboxymethyl) -N,N' ,N"-tris[2- [ (2- methoxyethyl) amino-2-oxoethyl] -2, 3-aminomethyl-5-amino-6- hydroxy-7-azabicyclo [2.2.1] heptane, dysprosium complex, and

N,N' ,N"-Tris (carboxymethyl) -N,N' ,N"-tris (2-hydroxyethyl- 2,3-aminomethyl-5-amino-6-hydroxy-7- oxabicyclo [2.2. l]heptane, gadolinium complex.

The compositions of the invention can be formulated into diagnostic compositions for enteral or parenteral administration. These compositions contain an effective amount of the paramagnetic ion complex along with conventional pharmaceutical carriers and excipients appropriate for the type of administration contemplated.

For example, parenteral formulations advantageously contain a sterile aqueous solution or suspension of from about 0.05 to about 1.0M of a paramagnetic ion complex according to this invention. Parenteral compositions may be injected directly or mixed with a large volume parenteral composition for systemic administration. Preferred parenteral formulations have a concentration of paramagnetic ion complex of about 0.1M to about 0.5M. Such solutions also may contain pharmaceutically acceptable buffers and, optionally, electrolytes such as sodium chloride. The compositions may advantageously contain a slight excess (e.g., from about 0.01 to about 15.0 mole % excess) of a complexing agent or its complex with a physiologically acceptable, non-toxic cation. Such physiologically acceptable, non-toxic cations include calcium ions, magnesium ions, copper ions, zinc ions, salts of n-methylglucamine and diethanolamine, and the like. Generally, calcium ions are preferred.

Formulations for enteral administration may vary widely, as is well-known in the art. In general, such formulations are liquids which include an effective amount of the paramagnetic ion complex in aqueous solution or suspension. Such enteral compositions may optionally include buffers, surfactants, thixotropic agents, and the like. Compositions for oral administration may also contain flavoring agents and other ingredients for enhancing their organoleptic qualities. The diagnostic compositions are administered in doses effective to achieve the desired enhancement of the NMR image. Such doses may vary widely, depending upon the particular paramagnetic ion complex employed, the organs or tissues which are the subject of the imaging procedure, the NMR imaging procedure, the NMR imaging equipment being used, and the like. In general, • parenteral dosages will range from about 0.001 to about 1.0 MMol of paramagnetic ion complex per kg of patient body weight. Preferred parenteral dosages range from about 0.01 to about 0.5MMol of paramagnetic ion complex per kg of patient body weight. Enteral dosages generally range from about 0.5 to about 100 MMol, preferably from about 1.0 to about 10 MMol, preferably from about 1.0 to about 20.0 MMol of paramagnetic ion complex per kg of patient body weight .

The diagnostic compositions of the invention are used in the conventional manner. The compositions may be administered to a patient, typically a warm-blooded animal, either systemically or locally to the organ or tissue to be imaged, and the patient then subjected to the NMR imaging procedure . Protocols for imaging and instrument procedures are found in texts such as Stark, D.D.; Bradley, W.G. Magnetic Resonance Imaging; Mosby Year Book: St. Louis, MO, 1992.

The following examples illustrate the specific embodiments of the invention described in this document. As would be apparant to skilled artisans, various changes and modifications are possible and are contemplated within the scope of the invention described. EXAMPLES

Example 1

Synthesis of N,N,N' ,N^* ,N' ' ,N' ' -Hexa(Carboxymethyl) -2,3- a^*mi^*r^*ιomet-hyl-5-a-^ -octane

A solution of endo-bicyclo [2.2.2] -oct-5-ene-2 , 3- dicarboxylic anhydride (50.0g, 281 mmol) in 200 mL of dry THF is added dropwise to a stirred, ice-cold solution of lithium aluminum hydride in THF (927 mL of a 1.0M solution, 927 mmol) . After the addition is complete the solution is refluxed for three hours. The solution is refluxed for three hours. The solution is cooled in an ice bath and the excess reagent destroyed by the slow addition of 38 mL of water, followed by 38 mL of 15% sodium hydroxide and lOOmL of water. The granular precipitate is removed by filtration and washed with fresh THF. The filtrate is evaporated. The residue is taken up into methylene chloride, washed with water and brine, dried over magnesium sulfate, filtered and evaporated. The product, bicyclo [2.2.2] -oct-5-ene-2, 3- methanol, is purified by recrystallization.

Methanesulfonyl chloride (22.9g, 15.5 mL, 200 mmol) is slowly added to an ice-cold solution of bicyclo [2.2.2] - oct-5-ene-2,3-methanol (33.6g, 200 mmol) and triethylamine (27.8 mL, 200 mmol) in 300 mL of methylene chloride. The solution is stirred at room temperature for three hours. The solvent is evaporated. The residue is taken up into ether, washed with dilute hydrochloric acid, dilute sodium bicarbonate, water and brine, dried over magnesium sulfate, filtered and evaporated. The product, 2 , 3-bis (methanesulfonylmethyl) -bicyclo [2.2.2] - oct-5-ene, is purified by recrystallization.

A mixture of 2,3-bis (methanesulfonylmethyl) - bicyclo [2.2.2] -oct-5-ene (48.6g, 150 mmol) and 3- chloroperoxybenzoic acid (51.8g of 50%, 150 mmol) in 500 mL of methylene chloride is stirred at room temperature for 24 hours. The solution is washed with 0.5M sodium hydroxide solution, water and brine, dried over magnesium sulfate, filtered and evaporated. The product 2,3- bis (methanesulfonylmethyl) -bicyclo [2.2.2] -5,6- epoxyoctane, is purified by recrystallization.

A mixture of 2, 3-bis (methanesulfonylmethyl) - bicyclo [2.2.2] -5, 6-epoxyoctane (42.5g, 125 mmol) and sodium azide (40.6g, 625 mmol) is stirred together in 300 mL of diethylene glycol at 135 C for 24 hours. The mixture is poured into 1000 mL of water. This solution is extracted with ether. The combined ether layers are washed with water and brine, dried over magnesium sulfate, filtered and evaporated. The residual oil, 2,3- azidomethyl-5-azido-6-hydroxy-bicyclo [2.2.2] -octane, is reduced in the next step without further purification.

The crude 2,3-azidomethyl-5-azido-hydroxy-bicyclo [2.2.2] - octane (27.7 g, 100 mmol) is diluted with 500 mL of methanol in a 2000 mL Parr bottle. Catalyst, 10% Pd/C (5g) , is added and the mateial is hydrogenated at 30 psi until all three azide group are reduced as indicated by IR. The catalyst is removed by filtration. Hydrogen chloride gas is bubbled through the filtrate to precipitate-2, 3-aminomethyl-5-amino-6-hydroxy- bicyclo [2.2.2] -octane as its trihydrochloride salt. The product is isolated by filtration.

The pH of a solution of bromoacetic acid (41.7g, 300 mmol) and 2, 3-aminomethyl-5-amino-6-hydroxy- bicyclo [2.2.2] -octane, trihydrochloride (15.4g, 50 mmol) in 150 mL of water is maintained at 10 by the addition of the required amount of sodium hydroxide (30g, 750 mmol) dissolved in 100 mL of water over a 24 hour period. The pH is adjusted to 7 and the solvent evaporated. The glassy residue is purified by C18 chromatography to afford N,N,N' ,N' ,N' ' ,N' ' -hexa (carboxymethyl) -2,3- aminomethyl-5-amino-6-hydroxy-biclyclo [2.2.2] -octane.

Example 2

Synthesis of Trisodium N,N,N^* ,N" ,N^* ' ,N» • - Hexa(carboxymethyl) -2,3-aminctmet±yl-5-amiιιo-6-hy roxy- bicyclo[2.2.2] -octanato (6-) gadolinate

N,N,N' ,N' ,N' ' ,N' ' -hexa (carboxymethyl) -2, 3-aminomethyl-5- amino-6-hydroxy-bicyclo [2.2.2] -octane (13.7g, 25 mmol) is dissolved in 100 mL of water. The pH is adjusted to 4 by the addition of 5% sodium bicarbonate solution.

Gadolinium oxide (9.1g, 25 mmol) is added and the milky suspension is heated at 70OC for 24 hours. The solution is filtered and evaporated. The residue is purified by C18 chromatography to afford trisodium N,N,N' ,N' ,N' ' ,N' '- hexa (carboxymethyl) -2, 3-aminomethyl-5-amino-6-hydroxy- bicyclo [2.2.2] -octanato (6-) gadolinate.

Although the invention has been described with respect to specific modifications, the details thereof are not to be construed as limitations, for it will be apparent that various equivalents, changes and modifications may be resorted to without departing from the spirit and scope thereof, and it is understood that such equivalent embodiments are to be included therein.

Claims

L_L__WL_

What is claimed is:

1. A compound of the general formula;

wherein R_x is selected from the group consisting of hydrogen,

hydroxyalkyl,

acyl, C₆-C₁₀ aryl, and C₆-C₁₀ aryloxy; R₂, R₃ and R₄ may be the same or different and are selected from the group consisting of hydrogen, Ci-Cg alkyl, Ci-C₈ hydroxyalkyl, Cι-C_β alkoxyalkyl, -CH₂C0₂H and CH₂CONR₅R₆ where R₅ and R₆ may be the same or different and are selected from the group consisting of hydrogen, C_j-Cg alkyl, Ci-Cg hydroxyalkyl and Ci-Cg alkoxyalkyl, R₅ and R₆ may form a 5 or 6 membered carbocyclic ring optionally containing singularly or in combination nitrogen, oxygen or sulfur; m, n and p may be the same or different and are selected from an integer from zero to about six; X is selected from the group consisting of -CH₂-, -0-, -S-, - S0₂-, -CH₂CH₂-, -CH₂0-, -CH₂S-, -CH₂S0₂-, CH₂NR₇ and -N-R₇-, where R₇ is selected from the group consisting of hydrogen, hydroxyl, Ci-C₈ alkyl, C--C₈ hydroxyalkyl and C₁- C₈ alkoxyalkyl and compositions comprising the compound.

2. The compound of Claim 1 wherein X is -CH₂CH₂ , R₁ is hydroxy, R₂ is hydroxyethyl, R₃ is hydroxyethyl, R₄ is hydroxyethyl, m is 0, n is 1, and p is 1.

3. The compound of Claim 1 wherein X is -NR₇, wherein R₇ is hydroxyethyl, R is hydroxy, R₂ is H, R₃ is H, R₄ is

H, m is 0, n is 1, and p is 1.

4 . The compound of Claim 1 wherein X is -0- , R_x is hydroxy, R₂ is -CH₂C0₂H, R₃ is -CH₂C0₂H, R₄ is CH₂C0₂H, m is 0 , n is 1 , and p is 1 .

5. The compound of Claim 1 wherein X is -CH₂CH₂, R_ is hydroxy, R₂, R₃, and R₄ are -CH₂CONR₅R₆, wherein R₅ is H and R₆ is methoxyethyl, m is 0, n is 1, and p is 1.

A compound of the general formula:

wherein Ri is selected from the group consisting of hydrogen, C_ι-C₈ alkyl , hydroxy, Cι-C₈ alkoxy, C-_.-C,, hydroxyalkyl , Ci-Cg acyl , C₆-C_ι0 aryl , and C₆-C_ι0 aryloxy; R₂, R₃ and R₄ may be the same or different and are selected from the group consisting of hydrogen, C^C_g alkyl,

alkoxyalkyl, -CH₂C0₂H and CH₂CONR₅R₆ where R₅ and R₆ may be the same or different and are selected from the group consisting of hydrogen, Ci-C_e alkyl,

hydroxyalkyl and Ci-C₈ alkoxyalkyl, R₅ and R₆ may form a 5 or 6 membered carbocyclic ring optionally containing singularly or in combination nitrogen, oxygen or sulfur; m, n and p may be the same or different and are selected from an integer from zero to about six; X is selected from the group consisting of -CH₂-, -0-, -S-, - S0₂-, -CH₂CH₂-, -CH₂0-, -CH₂S-, -CH₂S0₂-, CH₂NR₇ and -N-R₇-, where R₇ is selected from the group consisting of hydrogen, hydroxyl, Ci-C₈ alkyl, Ci-C₈ hydroxyalkyl and Ci~ C₈ alkoxyalkyl, Y is a metal ion, metal ion equivalent, or physiologically acceptable cation of an inorganic or organic base, provided that at least one Y is a metal ion or metal ion equivalent, and compositions comprising the compounds.

7. The compound of Claim 6 wherein at least one Y is a radioactive metal ion.

8. The compound of Claim 6 wherein at least one Y is a metal ion that absorbs x-rays.

9. The compound of Claim 6 wherein at least one Y is a paramagnetic metal ion.

10. The compound of Claim 7 wherein X is -CH₂CH₂, R_x is hydroxy, R₂, R₃, and R₄ are -CH₂C0₂Y, m is 0, n is 1, P is

I, and at least one Y is technetium.

II. The compound of Claim 7 wherein X is -CH₂CH₂, R₁ is hydroxy, R₂, R₃, and R₄ are -CH₂CONR₅R₆, wherein R₅ is H and R₆ is ethoxyethyl, m is 0, n is 1, p is 1, and at least one Y is yttrium.

12. The compound of Claim 7 wherein X is O, R_λ is hydroxy, R₂, R₃, and R₄ are -CH₂C0₂Y, m is 0, n is 1, p is

1, and at least one Y is rhenium.

13. The compound of Claim 7 wherein X is -CH₂CH₂, R_x is hydroxy, R₂, R₃, and R₄ are -CH₂CH₂OH, m is 0, n is 1, p is l, and at least one Y is indium.

14. The compound of Claim 8 wherein X is -CH₂CH₂, R_x is hydroxy, R₂, R₃, and R₄ are -CH₂C0₂Y, m is 0, n is 1, and at least one Y is lead.

15. The compound of Claim 8 wherein X is -0-, R_x is hydroxy, R₂, R₃, and R₄ are -CH₂CONR₅R₆, wherein R₅ is H and R₆ is -CH₂CH₂OCH₃, m is 0, n is 1, p is 1, and at least one Y is bismuth.

16. The compound of Claim 8 wherein X is NR₇, wherein R₇ is -CH₂CH₂OH, Ri is hydroxy, R₂, R₃, and R₄ are -CH₂C0₂Y, m is 0 , n is 1, p is 1, and at least one Y is gadolinium.

17. The compound of Claim 8 wherein X is -CH₂CH₂, Ri is hydroxy, R₂, R₃, and R₄ are -CH₂CH₂OH, m is 0, n is 1, p is 1 and at least one Y is dysprosium.

18. The compound of Claim 9 wherein X is -CH₂CH₂, R₁ is hydroxy, R₂, R₃, and R₄ are -CH₃, m is 0, n is 1, p is 1, and at least one Y is gadolinium.

19. The compound of Claim 9 wherein X is -CH₂CH₂, Ri is hydroxy, R₂, R₃, and R₄ are -CH₂CONR₅R₆, wherein R₅ is H and R₆ is methoxyethyl, m is 0, n is 1, p is 1, and at least one Y is gadolinium.

20. The compound of Claim 9 wherein X is -CH₂CH₂, R_x is hydroxy, R₂, R₃, and R₄ are -CH₂CH₂OH, m is 0, n is 1, p is

1, and at least one Y is dysprosium.

21. The compound of Claim 9 wherein X is NH, R. is hydroxy, R₂, R₃, and R₄ are -CH₂C0₂Y, m is 0, n is 1, p is 1, and at least one Y is iron.

22. A method for delivering radiopharmaceuticals to a patient which comprises administering a compound of the general formula:

wherein R is selected from the group consisting of hydrogen, C- -C₈ alkyl , hydroxy, Ci-C₈ alkoxy, Cι-C₈ hydroxyalkyl , Cι-C₈ acyl , C₆-C₁₀ aryl , and C₆-Cι₀ aryloxy; R₂ , R₃ and R₄ may be the same or different and are selected from the group consisting of hydrogen, Ci-C₈ alkyl , Cι-C₈ hydroxyalkyl , Ci-C₈ alkoxyalkyl , -CH₂C0₂H and CH₂CONR₅R₆ where R₅ and R₆ may be the same or different and are selected from the group consisting of hydrogen, Ci-C₈ alkyl , C_ι-C₈ hydroxyalkyl and C_ι-C₈ alkoxyalkyl , R₅ and R₆ may form a 5 or 6 membered carbocyclic ring optionally containing singularly or in combination nitrogen, oxygen or sulfur; m, n and p may be the same or different and are selected from an integer from zero to about six; X is selected from the group consisting of -CH₂-, -0-, -S-, - S0₂-, -CH₂CH₂-, -CH₂0-, -CH₂S-, -CH₂S0₂-, CH₂NR₇ and -N-R₇-, where R₇ is selected from the group consisting of hydrogen, hydroxyl, Ci-C₈ alkyl, C^-Cg hydroxyalkyl and C₁- Cg alkoxyalkyl, Y is a radioactive metal ion, or equivalent, or physiologically acceptable cation of an inorganic or organic base, provided that at least one Y is a radioactive metal ion or equivalent, and compositions comprising the compounds.

23. The method of Claim 22 wherein X is -CH₂CH₂, R is hydroxy, R₂, R₃, and R₄ are -CH₂C0₂Y, m is 0, n is 1, p is

1, and at least one Y is technetium.

24. The method of Claim 22 wherein X is -CH₂CH₂, R_x is hydroxy, R₂, R₃, and R₄ are -CH₂CONR₅R₆, wherein R₅ is H and R₆ is methoxyethyl, m is 0, n is 1, p is 1, and at least one Y is yttrium.

25. The method of Claim 22 wherein X is 0, R₁ is hydroxy, R₂, R₃, and R₄ are -CH₂C0₂Y, m is 0, n is 1, p is l, and at least one Y is yttrium.

26. The method of Claim 22 wherein X is -CH₂CH₂, R_x is hydroxy, R₂, R₃, and R₄ are -CH₂CH₂OH, m is 0, n is 1, p is 1, and at least one Y is indium.

27. A method for x-ray imaging which comprises administering to a patient a compound of the general formula:

wherein Ri is selected from the group consisting of hydrogen,

hydroxyalkyl, C_ι-C₈ acyl, C₆-C_ι0 aryl, and C₆-C₁₀ aryloxy;

R₂, R₃ and R₄ may be the same or different and are selected from the group consisting of hydrogen, C_ι-C₈ alkyl, C^Cg hydroxyalkyl, Cι-C₈ alkoxyalkyl, -CH₂C0₂H and CH₂CONR₅R₆ where R₅ and R₆ may be the same or different and are selected from the group consisting of hydrogen, Cι-C₈ alkyl, Ci-Cg hydroxyalkyl and Ci-C₈ alkoxyalkyl, R₅ and R₆ may form a 5 or 6 membered carbocyclic ring optionally containing singularly or in combination nitrogen, oxygen or sulfur; m, n and p may be the same or different and are selected from an integer from zero to about six; X is selected from the group consisting of -CH₂-, -0-, -S-, - S0₂-, -CH₂CH₂-, -CH.0-, -CH₂S-, -CH₂S0₂-, CH₂NR₇ and -N-R₇-, where R₇ is selected from the group consisting of hydrogen, hydroxyl, Cι-C₈ alkyl, C_x-C₈ hydroxyalkyl and C-_.- C₈ is alkoxyalkyl; Y is a metal ion that absorbs x-rays and or a physiologically acceptable cation of an inorganic or organic base, provided that at least one Y is a metal that absorbs x-rays, and the compositions comprising the compounds.

28. The method of Claim 27 wherein X is -CH₂CH₂, Ri is hydroxy, R₂, R₃, and R₄ is -CH₂C0₂Y, m is 0, n is 1, and at least one Y is lead.

29. The method of Claim 27 wherein X is -0-, Ri is hydroxy, R₂, R₃, and R₄ are -CH₂CONR₅R₆, wherein R₅ is H and R₆ is -CH₂CH₂OCH₃, m is 0, n is 1, p is 1, and at least one Y is bismuth.

•«

5 30. The method of Claim 27 wherein X is -0-, Ri is hydroxy, R₂, R₃, and R₄ are -CH₂CONR₅R₆, wherein R₅ is H and R₆ is -CH₂CH₂OCH₃, m is 0, n is 1, p is 1, and at least one Y is bismuth.

10 31. The method of Claim 27 wherein X is -CH₂CH₂, Ri is hydroxy, R₂, R₃, and R₄ are -CH₂CH₂OH, m is 0, n is 1, p is 1 and at least one Y is dysprosium.

32. A method for magnetic resonance imaging which 15 comprises administering to a patient a compound of the general formula:

30 wherein Ri is selected from the group consisting of hydrogen, C_ι-C₈ alkyl , hydroxy, C_ι-C₈ alkoxy, Ci-C_B hydroxyalkyl , C_ι-C₈ acyl , C₆-C_ι0 aryl , and C₆-C₁₀ aryloxy; R₂, R₃ and R₄ may be the same or different and are 35 selected from the group consisting of hydrogen, C_ι-C₈ alkyl, C^C_g hydroxyalkyl, C_ι-C₈ alkoxyalkyl, -CH₂C0₂H and CH₂CONR₅R₆ where R₅ and R₆ may be the same or different and are selected from the group consisting of hydrogen, C_ι-C₈ alkyl, Ci-C₈ hydroxyalkyl and C_ι-C₈ alkoxyalkyl, R₅ and R₆ may form a 5 or 6 membered carbocyclic ring optionally containing singularly or in combination nitrogen, oxygen or sulfur; m, n and p may be the same or different and are selected from an integer from zero to about six; X is selected from the group consisting of -CH₂-, -0-, -S-, - S0₂-, -CH₂CH₂-, -CH₂0-, -CH-.S-, -CH₂S0₂-, CH₂NR₇ and -N-R₇-, where R₇ is selected from the group consisting of hydrogen, hydroxyl, C_ι-C_B alkyl, C^-Cg hydroxyalkyl and Ci- Cg alkoxyalkyl, Y is a paramagnetic ion and/or a physiologically acceptable cation of an inorganic or organic base, provided that at least one Y is a paramagnetic metal ion, and compositions comprising the compound.

33. The method of Claim 32 wherein X is -CH₂CH₂, R_x is hydroxy, R₂, R₃, and R₄ are -CH₃, m is 0, n is 1, p is 1, and at least one Y is gadolinium.

34. The method of Claim 32 wherein X is -CH₂CH₂, R_: is hydroxy, R₂, R₃, and R₄ are -CH₂CONR₅R₆, wherein R₅ is H and R₆ is methoxyethyl, m is 0, n is 1, p is 1, and at least one Y is gadolinium.

35. The method of Claim 32 wherein X is -CH₂CH₂, R_x is hydroxy, R₂, R₃, and R₄ are -CH₂CH₂OH, m is 0, n is 1, p is 1, and at least one Y is dysprosium.

36. The method of Claim 32 wherein X is NH, R₁ is hydroxy, R₂, R₃, and R₄ are -CH₂C0₂Y, m is 0, n is 1, p is 1, and at least one Y is iron.