Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K49/00—Preparations for testing in vivo
  • A61K49/06—Nuclear magnetic resonance [NMR] contrast preparations; Magnetic resonance imaging [MRI] contrast preparations
  • A61K49/18—Nuclear magnetic resonance [NMR] contrast preparations; Magnetic resonance imaging [MRI] contrast preparations characterised by a special physical form, e.g. emulsions, microcapsules, liposomes
  • A61K49/1806—Suspensions, emulsions, colloids, dispersions
  • A61K49/1812—Suspensions, emulsions, colloids, dispersions liposomes, polymersomes, e.g. immunoliposomes
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K49/00—Preparations for testing in vivo
  • A61K49/04—X-ray contrast preparations
  • A61K49/0433—X-ray contrast preparations containing an organic halogenated X-ray contrast-enhancing agent
  • A61K49/0447—Physical forms of mixtures of two different X-ray contrast-enhancing agents, containing at least one X-ray contrast-enhancing agent which is a halogenated organic compound
  • A61K49/0461—Dispersions, colloids, emulsions or suspensions
  • A61K49/0466—Liposomes, lipoprotein vesicles, e.g. HDL or LDL lipoproteins, phospholipidic or polymeric micelles

Definitions

• the present invention discloses the use of radiographic contrast agents for the preparation of diagnostic formulations for the sequential or simultaneous X ray and nuclear magnetic resonance (MRI) diagnostics.
• MRI nuclear magnetic resonance
• X-ray contrast agents used in in vivo diagnostics are usually characterized by high water solubility, low viscosity, low osmotic pressure, high contrast density, low toxicity and good tolerability.
• non-ionic contrast agents comprise Ioexol,
• Iomeprol Iopentol, Iopromide, Ioversol, Ioxilan, Iodixanol and Iopamidol.
• Magnetic Resonance Imaging diagnostic procedures mainly use paramagnetic compounds, preferably chelated complexes of bi- or trivalent paramagnetic metal ions with polyaminopolycarboxylic acids and/or their derivatives or analogues.
• MRI contrast agents comprise: Gd-DTPA, MAGNENIST®; Gd-DOTA, DOTAREM®; Gd-HPD03A PROHA ⁇ CE®; Gd-DTPA-BMA, OM ⁇ ISCA ⁇ ®.
• the contrast agents listed above are designed for a wholly general use. In fact, after intravenous administration, the MRI contrast agent is distributed in the extracellular spaces in different parts of the body prior to being excreted. In this sense they are similar to iodine compounds used in X ray medical diagnosis.
• a recently proposed technique for MRI diagnostic is the magnetization transfer technique (see e.g. J. Chem. Phys. 39 (1 1), 2892-2901, 1963), in which the proton signal of a molecule, present in the medium or added thereto, is suitably irradiated with a radiofrequency signal generated by the apparatus magnetic field, and transferred through magnetization to the water molecules surrounding the compound, i.e. the so-called "bulk water” of the medium.
• US 5 050 609 discloses the use of the saturation transfer technique in magnetic resonance, which consists in the magnetization transfer in the presence of an irradiating field able to saturate the protons involved in the exchange process, which procedure is used in vitro and provides further information from the analyzed samples, e.g. biological tissues, polymeric compounds or samples of solid compounds of geologic interest.
• both J. of Mag. Res., 143, 79-87, 2000 and WO00/66180 disclose the use of some compounds in MRI with saturation transfer techniques of the proton signal.
• the compounds used for this purpose belong to different chemical classes, consisting of sugars (e.g. mannitol, sorbitol, fructose, maltose, lactose and dextran), amino acids (e.g. L-Ala, L-Arg, L-Lys), nucleosides, purine and pyrimidine bases, barbituric acid, imidazole compounds and other heterocyclic compounds.
• X ray diagnostic contrast agents are an extremely versatile and interesting class of compounds widely used in clinics thanks to their effectiveness, low toxicity and safety of use in diagnosis concerning different districts of the human body, such as in urography, angiography, ventriculography and myelography.
• the dose of opacifying agent being injected can reach and even exceed 150 g and the combination of two diagnostic techniques would be cost-saving.
• the object of the present invention is the use of a iodinated contrast agent comprising at least one amido function for the preparation of a diagnostic formulation to obtain in vitro or in vivo images using magnetization transfer MRI techniques.
• Iodinated contrast agents comprising at least one amido function herein means iodinated aromatic compounds having a triiodinated aromatic ring bearing at the remaining positions straight or branched, functionally substituted organic residues or an organic compound comprising at least two triiodinated aromatic residues mutually covalently linked at one of the positions, either directly or through a straight or branched, functionally substituted organic residue, said aromatic ring being further substituted at the remaining positions by straight or branched, functionally substituted organic residues and in which the organic residues and the triiodinated aromatic ring are linked by amido functions.
• contrast agents for use according to the invention comprise the compounds of general formula (I) and (II), (III) and (IN) reported below, the corresponding isomers and stereoisomers, in particular the exo, endo regioisomers; the corresponding enantiomeric, racemic and meso forms as well as the salts thereof with physiologically compatible bases or acids.
• the method of the invention is based on the use of iodinated contrast agents having mobile protons able to exchange with bulk water, i.e. the surrounding water molecules present in the medium and in the biological tissues.
• the used procedure consists in the use of the contrast medium in vivo or in vitro and in performing the radiological and/or MRI diagnostic analysis at different times and depending on the used technique, starting from one or the other diagnostic procedure.
• the resulting MRI images are suitably acquired before, during and/or after irradiation in the radiofrequency field of the proton that exchanges with the water of the medium.
• the result from the experimentation allows to compare images obtained with X rays and with MRI.
• the sequence of the radiological and MRI techniques which are considered complementary, can be reversed, depending on the body site concerned and the diagnostic analysis. In fact, it may be convenient to carry out first MRI on the body angiographic district, then a radiological urographic investigation.
• a further object of the present invention is the use of the disclosed MRI diagnostic technique alone, using the above defined iodinated compounds as contrast agents.
• the advantages deriving from the use of this class of compounds are that they have known, low in vivo and in vitro toxicity, which makes them easy to use at different dosages, depending on the product used and on the concerned body site.
• Other advantageous aspects of these compounds are their high water solubility and chemical stability, and well-established pharmacokinetic (see e.g. RoFo Suppl. 128, 220-223 (1989); Invest. Radio. ,18, 368-374, 1983; Invest. Radio., 26, S156-S158, 1991) in terms of transport rate in circulation or in other body cavities, retention time in the organs being under examinated, excretion and clearance.
• a first preferred group of iodinated contrast agents comprising amido functions are the compounds of formula (I)
• A, D, E which can be the same or different, are groups of formula -CON(R)R l 5 -COOH, -CONH 2 or -N(R)-COR 2 or CH 2 N(R) -COR 2 ;
• R is H or R,, with the proviso that the substituent R is H in at least one group of the compound
• R is a straight or branched (C C 6 ) alkyl residue, optionally substituted with 1-5 hydroxy and/or alkoxy and/or hydroxy-alkoxy groups, or with a NH-CO-Rj or -CO-N(R)R ! group, or R, ⁇ is a carbohydrate residue;
• R 2 is a straight or branched (Cj-C 6 ) alkyl residue, optionally substituted with 1-5 hydroxy and/or alkoxy and/or hydroxyalkoxy groups and optionally interrupted by an oxo group.
• a second preferred group of iodinated contrast agents comprising amido functions includes compounds of formula (II)
• A, D and E are as defined above;
• B and B' which can be the same or different, are selected from -CO-N(R)-, -N(R)-CO- or -N(COR 3 )- groups, in which R is H or a residue of a straight or branched (C C 6 ) alkyl group, optionally substituted with 1-5 hydroxy and or alkoxy and/or hydroxyalkoxy groups; R 3 is a ( -C 3 ) alkyl residue, optionally substituted with 1-2 hydroxy or alkoxy or hydroxyalkoxy groups; X is a covalent bond or a straight or branched (C r C 8 ) alkylene chain, optionally substituted with 1-6 hydroxy and/or -CO-NHR groups, and optionally interrupted by -0-, -S-, -N-, -N(R)-CO groups; in case both groups B and X are absent, the two aromatic compounds are directly linked with a covalent bond with the proviso that the substituent R is H in at least
• Preferred compounds of general formula (I) are the compounds of general formula (III) in which:
• R 4 , R 5 which can be the same or different, are H or a straight or branched (C r C 3 ) alkyl group, which can optionally be substituted with 1-2 hydroxy and/or alkoxy and/or hydroxyalkoxy groups;
• R 6 is a straight or branched (C C 4 ) alkyl group containing one or more hydroxy, alkoxy or acyloxy groups.
• a further preferred group of iodinated contrast agents comprising amido functions comprises compounds of formula (IN):
• A' is a OH or - ⁇ HR 1 group
• R] is a straight or branched (C C 6 ) alkyl group, optionally substituted with 1-5 hydroxy and/or alkoxy and/or hydroxyalkoxy groups, or by a -NH-CO-R ! or -CO-NHR, group, or R, is a carbohydrate residue;
• B" and B"' which can be the same or different, are H or R l 5 as defined above;
• R 7 and R 8 which can be the same or different, are H, an acyl -COR, group, an alkyl group, a mono or polyhydroxyalkyl group or a carbohydrate residue; with the proviso that at least one of the groups B", B"', R 7 or R 8 is H.
• a particularly preferred example of the compounds of formula (IN) is Metrizamide (see scheme 2 and US 3 701 771 , US 4 021 481), a water- soluble, non-ionic contrast agent having moderate toxicity and usually present as isomeric mixture.
• a further preferred compound is diatrizoic acid (compound of formula IN), Renografin® (see scheme 2 and e.g. Radiology 140: 507-51 1 , 1981 ; Biochimica et Biophysica Acta. 756, 106-1 10, 1983, Elsevier Biomedical Press and US 4 192 859, US 4 567 034 and US 4 735 795) which is particularly suitable for the use according to the present invention.
• Particularly preferred compounds for use according to the present invention comprise: lopamidol, lofratol, Iopromide, Metrizamide, logulamide, loglunide, lobitridol, lodamide, Sodium diatrizoate and other diatrizoic acid salts, and possible combinations thereof.
• contrast agents for use according to the present invention are described in the following patents, herein incorporated by reference: US 4 3 64 921 , US 4 284 620, US 3 701 771, US 4 001 323, US 4 001 323, US 4 250 113, US 4 396 598, US 4 192 859, US 5 663 413, US 4 239 747, US 4 014 986, EP108 638, WO9208691 , WO9515307, EP 33 426, US 4 567 034, US 4 735 795, US 5 869 024, US 5 527 926, EP 431 838, EP 437 144.
• aqueous compositions of liposomes consisting of lipid molecules mono-, bi- or multi- layers as carriers for the compounds used as contrast agents is particularly preferred.
• US 4 192 859 discloses the preparation of liposomes made of lecithin and sterols, containing 20 to 60% by weight of contrast agent for use in imaging of organs, and in particular of endothelial reticule, cardiovascular system and also for lymphographies.
• Compounds that can be used for this purpose comprise, for example, the following contrast agents: lopamidol, metrizamide, diatrizoic acid, sodium diatrizoate, meglumine diatrizoate, acetrizoic acid and the soluble salts thereof, diprotizoic acid, lodamide, lodipamide sodium salt, lodipamide meglumine salt, iodohippuric acid and the soluble salts thereof, iodometamic acid, iodopyracetiodo-2-pyridone-N-acetic acid, 3,5-diiodo-4-pyridone-N-acetic acid (Iodopiracet) and its diethyl ammonium salt, iothalamic acid, metrizoic acid and the salts thereof, ipanoic, iocetamic, iophenoxic acids and the soluble salts thereof, sodium tyropanoate, sodium hypodate and other similar
• liposomes containing opacifying contrast agents are disclosed in the following patents, herein incorporated by reference: US 4 192 859, FR-A-2561 101, US 4 567 034, GB-A-134869, GB-A-2135268, GB-A-2135647, GB-A-2156345, GB-A-2157283, EP-A-179660, US 4 192 859, US 4 744 989, US 4 830 858, US 5 393 530, US 5 702 722, US 5 895 661 , US 5 980 937, US 5 312 615, US 5 445 810, US 5 626 832.
• Advantageous characteristics of the iodinated compounds described above are high water solubility, safety of use in vivo, pharmacological inertia, high chemical stability, low viscosity, low osmolarity and effective magnetization transfer in the presence of the radiofrequency signal applied at the absorption frequency of mobile protons.
• said compounds have moderate in vivo toxicity and can be used at high dosages in diagnostic contrastographic applications.
• Scheme 5 shows some data (Merck Index 12 th ed.) concerning toxicity of lopamidol, Iopromide, Metrizamide and Sodium Diatrizoate.
• Scheme 5 lopamidol
• mice rats, rabbits, dogs (g/kg): 44.5; 28.2; 19.6; 34.7 Iopromide 4948.
• LD50 in mice rats (g iodine/kg body weight): 16.5; 11.4 i.v.
• mice 15 g/kg (Torsten); 18.6 g/kg (Salvenson); 11.5 g/kg (Sovak); 17.3 g/kg (Aspelin). Sodium diatrizoate 2975.
• LD50 i.v. in rats 14.7 g/kg (Langecker).
• the compounds of the invention can be used in various radiographic and/or MRI procedures, including those concerning intravascular imaging such as myelography, urography, angiography (e.g. cerebral and peripheral angiography), cardiography (e.g. coronary arteriography and/or aortography), arthrography, for example of animal or human organs such as heart, breast, brain, knee, liver and central nervous system.
• intravascular imaging such as myelography, urography, angiography (e.g. cerebral and peripheral angiography), cardiography (e.g. coronary arteriography and/or aortography), arthrography, for example of animal or human organs such as heart, breast, brain, knee, liver and central nervous system.
• An interesting application of the MRI technique of the present invention is the use in angiographic diagnostics of blood vessels in organ perfusion imaging.
• Magnetization transfer is affected by some parameters, such as intensity of the applied magnetic field, intensity of the radiofrequency field, chemical group involved in the prototropic exchange with water, pH, temperature of the medium, and water and "exogen" compound contents in the concerned tissue.
• intensity of the radiofrequency field used for the saturation corresponds to an higher decrease of the bulk water signal.
• pH and temperature affect the proton exchange rate; in particular, an increase in temperature always induces an increase in the exchange rate, while pH catalyzes the exchange as it deviates from neutrality.
• pH 7 the exchange rate of the mobile protons is minimum and it increases when the solution is acidified (pH ⁇ 7) or alkalinized (pH>7).
• the value of the applied magnetic field is very important in that, for a given system, high B 0 values allows for higher exchange rates before incurring in a too large resonance broadening of exchangeable protons, which would make its efficient saturation with the irradiating field no longer possible.
• the magnetization transfer technique can be carried out coupled with different kind of sequences, such as those known as “gradient or field echo” and “spin echo and fast spin echo".
• sequences currently used in imaging are “gradient or field echo” rather than “fast spin echo”.
• the iodinated contrast agents are used at concentrations which vary depending on the compound used and the particular diagnostic use. As a rule, the examination of a specific district of the human body determines the amount and the corresponding concentration used.
• the pharmaceutical formulation of the contrast agent which is usually an aqueous solution, contains for example 15 g of compound per 100 mL of solution, corresponding to a iodine amount ranging from 50 to 500 mg per mL.
• solutions containing lower amounts of the contrast agent can also be used.
• the amount of solution used in the investigations carried out according to the invention is usually comparable to that used in radiological analysis and varies depending on the concerned body site: for example, 5 to 15 mL in myelography, 3 to 5 mL in radiculography and 1 to 2 mL in ventriculography.
• the solution or suspension containing the contrast agent can optionally be administered directly through the enteral route.
• solutions or suspensions containing 1 to 100 mmoles of contrast agent, suspended in 1-2 1 of physiologically compatible solution can be used.
• a further object of the present invention is an X ray and/or MRI procedure comprising the administration of a pharmaceutical composition containing a suitable amount of a compound or a mixture of compounds as defined above, in particular of general formula (I), (II), (III) and (IN), for the imaging and the recording of the image of an organ of the individual under observation.
• the compounds of formula (I), (II), (III) and (IN) can be administered through the oral or enteral route.
• they are preferably formulated as sterile aqueous solutions or suspensions, with pH ranging from 6.0 to 8.5.
• Said aqueous solutions or suspensions can be administered in concentrations ranging from 0.02 to 500 mM.
• these formulations can be lyophilized and supplied as such, to be reconstituted just before the use.
• these agents can be formulated as a solution or suspension containing suitable additives in order to, for example, control viscosity, such as stabilizers, agents for controlling dissolution, anticoagulants, excipients used in the preparation of formulations and water soluble, physiologically compatible mineral salts.
• Example 1 illustrates the invention in greater detail.
• the exchange rate between amido protons and water is affected by the pH of the solution.
• the transfer effect is maximum at pH 7.5. This effect decreases as pH becomes both more acid and more basic.
• pH is below 6, or above 9, no effects are observed. In fact, outside this pH range from 6 to 9, the exchange is too fast for the purposes of the invention.
• Table 1 - R2 values ( 1/T2) of water protons in a 50 mM lopamidol solution as a function of pH at 2.1 and 9.34 T. Measurements were carried out with a JEOL EX-400 spectrometer at 25°C using the CPMG sequence for the determination of T2.
• a 200 Mm lopamidol solution at pH 6.29 was investigated at 2. IT magnetic field intensity and at a temperature of 39°C (JEOL EX-90 spectrometer).
• a 40% residual signal value is measured when the irradiating field has an attenuation of 400 dB, which decreases to 15% when the attenuation is 300 dB.
• the sample is a plastic cylinder containing distilled water and a coaxial cone filled with the lopamidol aqueous solution at pH 7.4.
• Measurements were carried out at a temperature of about 21°C using a spin echo sequence coupled with the saturation transfer technique.
• MTC power level 9 ⁇ T n° of MTC pulses 380 with 104 ⁇ s pulse length (pulse shape gauss).
• the top left image was recorded applying the presaturation impulse at the amido protons resonance frequency (i.e. at 1280 Hz from water), the top right image was recorded applying the presaturation impulse at the frequency opposite to that of amido protons relative to bulk water (-1280 Hz), the bottom left image was obtained from the difference between the two first images, whereas the bottom right image was obtained without using the magnetization transfer technique.
• Example 4 The procedures of Example 4 were followed, but using a 10 mM lopamidol aqueous solution.

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