JPH08208525A - Contrast medium for image diagnosis - Google Patents

Abstract

PURPOSE: To prepare a contrast medium for image diagnosis having an oligosaccharide as a skeleton which is readily produced without induction of undesired side-reactions and is properly soluble in water with high stability and permissible physiologically, thus is useful in diagnoses with nuclear magnetic resonance, X-rays, radioactive rays and so on. CONSTITUTION: This contrast medium comprises a compound which is prepared by allowing at least one bifunctional ligand to bond to the amino group of an amino-oligosaccharide whose reductive chain terminal is reduced and whose molecular weight is 500-2,000 or to the aldehyde group of an oligo-dialdehyde- saccharide whose at least one constituting monosaccharide is cleft by oxidation and whose reductive terminal is reduced and has molecular weight of 500-2,000, then by coordinating at least one kind ion of metallic elements selected from those of atomic numbers of 21-29, 31, 32, 37-39, 42-44, 49 and 56-83 thereto.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a contrast agent for image diagnosis,
In particular, the present invention relates to a contrast agent for diagnostic imaging useful for nuclear magnetic resonance diagnostic imaging, X-ray diagnostic imaging or radiographic diagnostic imaging, which contains a metal complex compound having an oligosaccharide as a skeleton in which the reducing end of a sugar chain is subjected to reduction treatment.

[0002]

2. Description of the Related Art Diethylenetriaminepentaacetic acid-Gd (hereinafter abbreviated as DTPA-Gd), which is widely used as a contrast agent for nuclear magnetic resonance diagnosis [JP-A-58-29718], is a representative example of a mononuclear complex group. Therefore, its effectiveness is almost established as a diagnostic agent in the brain and spinal cord regions. However, the degree of relaxation indicating the image display scale is lower than that of Gd itself because it is complexed. Therefore,
The decreased degree of relaxation requires treatment such as supplementation with an increase in the dose. In addition, this drug is excreted in the urine immediately after administration [Hiroki Yoshikawa et al .: Image diagnosis, 6, 95
9-969 (1986)], a single dose reflects on several parts of the body in the blood flow (vascularization of lesions, blood flow distribution, distribution volume, invasiveness, etc.) and is imaged. The distribution characteristics are also extremely disadvantageous.

In order to solve these problems, a bifunctional ligand is chemically bonded to an amino oligosaccharide, and a metal ion is coordinate-bonded through the bifunctional ligand to provide a contrast agent for diagnostic imaging. [JP-A-5-97712] or D-
At least one bifunctional ligand is chemically bonded to a dialdehyde sugar in which a plurality of glucoses are linked and at least one of the constituent monosaccharides is oxidatively cleaved, and a metal ion is mediated by the bifunctional ligand. A contrast agent for image diagnosis in which the above are coordinate-bonded has been developed [JP-A-5-25059]. However, sugar raw materials, which are important constituents of these compounds, have an intramolecular or intermolecular bond in an aqueous solution if left unreacted or reacted for a long time when the reducing end of the sugar chain is untreated, It was found to undergo peroxidation by oxidants.

[0004]

In view of the above situation, the present invention can be easily produced in the production of an imaging diagnostic contrast agent having an oligosaccharide as a skeleton without inducing unnecessary side reactions, Moreover, it is an object of the present invention to provide a contrast agent for image diagnosis which is stable, has good solubility in water, and is useful in physiologically acceptable nuclear magnetic resonance diagnosis, X-ray diagnosis, radiological diagnosis and the like.

[0005]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present inventors have conducted diligent studies, and as a result, by reducing the reducing end of the oligosaccharide of the starting oligosaccharide,
The above-mentioned side reaction can be avoided, and the metal complex compound produced by using the compound as a raw material is stable, has good solubility in water, and has a physiologically acceptable nuclear magnetic resonance diagnosis,
It has been found that it is a contrast agent for image diagnosis useful for X-ray diagnosis or radiological diagnosis. That is, in the present invention, the reducing end of the sugar chain is subjected to reduction treatment, and the amino group of the amino oligosaccharide having a molecular weight of 500 to 2000 or at least one of the constituent monosaccharides is oxidatively cleaved and the reducing end of the sugar chain is subjected to reduction treatment. Further, at least one or more bifunctional ligands are chemically bonded to the aldehyde group of the oligodialdehyde sugar having a molecular weight of 500 to 2000, and the bifunctional ligands have atomic numbers 21 to 29, 31, 32, 37-39, 42-44,
A contrast agent for image diagnosis, comprising a compound in which at least one metal element ion selected from the group of 49 or 56 to 83 is coordinated.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The reduction treatment of the reducing end of the oligosaccharide sugar chain is carried out by a known method such as a method using sodium borohydride or catalytic reduction with hydrogen. For example, it can be obtained by dissolving chitosan trimer in water, adding sodium borohydride, stirring the mixture at room temperature under reduced pressure, and then adding hydrochloric acid to acidify the mixture. The disappearance of the reducing end means that the Brix method [Blix, G. : Acta Chem. Scan
d. , 2, 467, 1948]. A commercially available product such as maltotetriitol that has been previously reduced may be used. As oligosaccharides, amino oligosaccharides, or maltotriose, maltotetraose, maltopentaose, maltohexaose, maltoheptaose, isomaltotriose, isomalttetraose, isomaltopenose, isomalthexaose, iso Maltoheptaose, cellotriose, cellotetraose, cellopentaose, cellohexaose, laminaritriose, laminaritetraose, laminaripentaose, laminarihexaose, laminariheptaose, erulose, panose, or raffinose Dialdehyde sugar is mentioned.

Preferred amino oligosaccharides are chitosan oligosaccharides and galactosamino oligosaccharides 3, 4, 5,
Examples include 6, 7, 8, 9 or 10 sugars, and particularly preferable are 3, 4, 5 or 6 sugars of chitosan oligosaccharide and galactosamino oligosaccharide.

The bifunctional ligand binds to the amino group at the 2-position when the sugar to be reduced is an amino oligosaccharide and to the aldehyde group when the sugar to be reduced is an oligodialdehyde sugar. A chain or cyclic polyaminopolycarboxylic acid having a crosslinkable chain portion that can be used is used. Preferably,
As the coordination partial structure, diethylenetriaminepentaacetic acid (hereinafter abbreviated as DTPA), 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (hereinafter abbreviated as DOTA), or 1,4 , 8,11-Tetraazacyclotetradecane-1,4,8,11-tetraacetic acid (hereinafter abbreviated as TETA), or a derivative thereof, which is a bifunctional ligand. As the reactive group of the bridging chain portion of the bifunctional ligand capable of binding to the amino group at the 2-position, active halogen, alkoxy ester, succinimidi ester, isothiocyanate, acid anhydride and the like are preferable. Specifically, 1- (p-isothiocyanatebenzyl)-
DTPA [Martin, W. B. Et al: Inorg. C
hem. 25, 2772-2781 (1986
Year)], anhydrous DTPA, 2- (p-isothiocyanatebenzyl) -DOTA [USP4678667] and the like. Further, the bifunctional ligand to be bonded to the aldehyde group preferably has an active amino group. Specifically, 1- (p-aminobenzyl) -DT
PA [Martin, W. B. Et al: Inorg. Che
m. , 25, 2772-2781 (1986)],
2- (p-aminobenzyl) -DOTA [USP467
No. 8667], 2-aminobutyl-DOTA [P
arker, D.A. Et al., Pure & Appl. Chem.
61, 1637-1641 (1989)], 1,
Examples include 4,7,10-tetraazacyclododecane-1-aminoethylcarbamoylmethyl-4,7,10-tris [(R, S) -methylacetic acid].

The reduction-treated oligosaccharide and the bifunctional ligand are bound by a known method. For example, by reacting a dialdehyde-modified sugar obtained by oxidative cleavage of a reduced oligosaccharide and a bifunctional ligand having an active amino group as a reactive group at room temperature in an alkaline solution. The target product is obtained. In this case, the reaction can be carried out in situ without considering the side reaction due to the oxidizing agent used for preparing the reduced oligosaccharide into the dialdehyde-modified sugar, which not only facilitates the reaction. Also, the complicated purification operation during the synthesis is not necessary, and the synthesis operation becomes simpler. If necessary, by reducing the conjugate may be converted -CH = N-to -CH ₂ -NH-. The bifunctional ligand may be prepared by complexing a metal in advance.

The metal element ion of the present invention has an atomic number of 21.
~ 29, 31, 32, 37-39, 42-44, 49 and 56-83 metals are selected according to the diagnostic imaging application. When the diagnostic contrast agent of the present invention is used for nuclear magnetic resonance diagnosis, the metal element ion must be paramagnetic and is selected from the group consisting of ions of the lanthanoid elements with atomic numbers 26 and 57-70. Preferably G
d, Dy, Tb, Ho, Er or Fe. When used for X-ray diagnosis, the metal element ion has an atomic number of 5
Ion and atomic number 5 of lanthanide series element of 7-70
It is selected from the group consisting of ions of the elements 6, 76, 82 and 83, with Bi, Pb or Os being preferred. Further, when used as a radiological image diagnostic agent, the metal element ion must be radioactive, and Co, Cu, G
Radioactive metal element ions of a, Ge, Sr, Y, Tc, In, Sm, Yb, Re or Ir are suitable. The metal element ion used may be the metal itself or an inorganic compound thereof (eg, chloride, oxide, etc.). Complexation is performed by a conventional method.

In the obtained metal complex compound, at least one bifunctional ligand is chemically bonded to the oligosaccharide subjected to the reduction treatment, and the metal element ion is coordinately bonded.

The amount of the contrast agent for image diagnosis of the present invention to be used is selected according to the purpose of image diagnosis. For example, for use as a contrast agent for nuclear magnetic resonance, the amount of metal element ions is generally 0.001 to 10 mmol / kg, preferably 0.05 to 0.5 mmol / kg. For use as a contrast agent for X-ray diagnosis, the amount of metal element ions is 0.01 to 20 mmol / kg, preferably 0.1 to 10 mmol / kg. Furthermore, in order to use it as a radiological diagnostic agent, 370 to 1
A radioactivity dose of 8500 MBq is administered. It is usually administered intravenously, but in some cases it may be administered orally or intraarterially.

In the contrast agent for diagnostic imaging of the present invention, the retention in blood is considered to be clinically effective as a blood half-life of 0.5 to 5.
In time range. This is effective for the purpose of increasing the collection efficiency of the proton relaxation effect of the contrast agent in a low magnetic field nuclear magnetic resonance apparatus which requires a longer time for imaging than in a high magnetic field nuclear magnetic resonance apparatus, for example. Further, the high relaxation effect per unit amount of metal also has an advantageous effect. For example, in a diagnosis by a low magnetic field nuclear magnetic resonance apparatus having a low proton relaxation effect collection efficiency, the relaxation effect per unit amount of metal is high, so the detection efficiency is improved and the imaging time can be shortened. Furthermore, D
Since the shortening time of the relaxation time per molecule is longer than that of TPA-Gd, DTPA-G in an apparatus with the same magnetic field strength
When it is desired to obtain the same contrasting effect as that of d, the contrast agent for image diagnosis of the present invention requires a lower dose than DTPA-Gd, which is advantageous in terms of safety. On the contrary, if the dose is the same, the contrast agent for image diagnosis of the present invention provides more biological information, and clinical usefulness is improved. Therefore, according to the present invention, a contrast agent having a retentivity in blood and an effective contrast effect suitable for the magnetic field strength of the nuclear magnetic resonance apparatus or imaging conditions is provided.

Further, since the contrast agent for image diagnosis of the present invention exhibits an appropriate retention property in blood, it is possible to evaluate a blood vessel distribution image (vascularity). Therefore, the contrast agent for image diagnosis of the present invention can image blood vessels without using a special pulse sequence for MR angiography, which has made remarkable progress in recent years, and thus is also useful as a contrast agent for image diagnosis for intravenous administration. is there.

Since the contrast agent for diagnostic imaging of the present invention has good water solubility, it can prepare a high-concentration solution by itself. Therefore, it is not always necessary to use a solubilizer when preparing a solution. Further, since it is a polynuclear complex compound, it is possible to reduce the total number of moles of the prepared solution as compared with the mononuclear complex compound, which leads to a decrease in osmotic pressure. These reduce the load on the volume of the circulatory system or the equilibrium of body fluid during in vivo administration, which is advantageous in terms of safety.

The contrast agent for diagnostic imaging of the present invention is prepared by dissolving it in distilled water for injection or a physiologically administrable aqueous solvent. You may add a pH adjuster or a solubilizer as needed. Examples of the pH adjusting agent include sodium hydroxide and hydrochloric acid, and examples of the solubilizing agent include N-methylglucamine.

[0017]

The present invention will be described in more detail below with reference to examples, but the technical scope of the present invention is not limited thereto. The abbreviations have the following meanings. DTPA: diethylenetriaminepentaacetic acid DO3MA: 1,4,7,10-tetraazacyclododecane-1-aminoethylcarbamoylmethyl-4,
7,10-Tris [(R, S) -methylacetic acid] R-CHI3: A product obtained by reducing the reducing end of chitosan trimer R-CHI5: A product obtained by reducing the reducing end of chitosan pentamer R-GLU4: Maltothe Try Tor

Example 1 Synthesis of R-CHI3-DTPA-Gd Chitosan trimer (10 g; 16.3 mmol) is dissolved in distilled water (300 ml) and the pH is adjusted to 8 with 1M sodium hydroxide. Sodium borohydride (1.9 g; 51.3 mmol) was added thereto, and the mixture was stirred under reduced pressure for 3.5 hours. The pH was adjusted to about 2 with 2M hydrochloric acid, and desalting was performed by electrodialysis to obtain a product (9 g).
The amino group by the ninhydrin method, the sugar skeleton by the sulfuric acid coloring method and the reducing end treatment by the Brix method were confirmed to confirm that the product was R-CHI3. R-
CHI3 (1.0 g; 1.63 mmol) was added to distilled water (1
It was dissolved in 10 ml of sodium hydroxide (5 ml).
ml), then anhydrous DTPA (7.16 g; 20.0 mm)
ol) was added rapidly and the mixture was stirred for 3 hours. Next, gadolinium chloride hexahydrate (7.45 g; 20.0 mmol) was added and an appropriate amount of 1M sodium hydroxide was added to adjust pH to 7, followed by stirring for 30 minutes. After 120 hours of electrodialysis to remove excess DTPA, the mixture was concentrated to dryness and white crystals (4
50 mg) was obtained. The Gd content was 15.8 wt%.

(Example 2) Synthesis of R-CHI5-DTPA-Gd In the same manner as in the synthesis method of R-CHI3 described in Example 1, R-CHI5-DTPA-Gd was synthesized.
-CHI5-DTPA-Gd was synthesized. R-CHI5
(100 g; 99.4 mmol) in distilled water (1500 m
l) dissolved in 10M sodium hydroxide (600m
l), then anhydrous DTPA (700 g; 1981 mmo
1) was quickly added and the mixture was stirred for 3 hours. Next, gadolinium chloride hexahydrate (884 g; 2377 mmol) was added to adjust the pH to 7, and the mixture was stirred for 30 minutes. Excess DT
After performing electrodialysis for 400 hours to remove PA-Gd, it was concentrated to dryness to obtain a white crystal (200 g). The Gd content was 19.5 wt%.

Example 3 Synthesis of R-GLU4-DO3MA-Bi DO3MA (3.0 g; 5.7 mmol) was added to distilled water (1
50 ml) and bismuth chloride (1.8 g; 5.7)
mmol) was added and the pH was brought to 7 with 1 M sodium hydroxide. After heating and stirring at 60 ° C for 24 hours,
It was filtered and concentrated to dryness. A compound DO3MA-Bi (5.1 g) in which bismuth chelate with DO3MA was obtained. R-GLU, which is a commercially available product whose reducing end is subjected to reduction treatment
4 (0.5 g; 0.75 mmol) in distilled water (15 m
l) dissolved in 0.2M sodium metaperiodate (25
(ml) was added little by little and then stirred for 1 hour. Next DO3
MA-Bi (1.8 g; 2.4 mmol) and triethylamine (0.25 g; 2.4 mmol) were added, and 2 was added at room temperature.
Stir for 4 hours. Sodium borohydride (0.1 g;
2.4 mmol) was added and the mixture was stirred for 4 hours and then filtered to remove the precipitate. Next, in order to remove excess sodium borohydride, 1M hydrochloric acid was added little by little, and the pH was lowered to 5, followed by filtering to remove the precipitate, and adding 1M sodium hydroxide to p.
H was set to 7. For purification, dialysis (dialysis membrane with molecular weight cutoff of 500) was performed for 40 hours, concentrated to dryness and white crystals (170 m
g) was obtained. The Bi content was 14.1 wt%.

(Example 4) Measurement of relaxation degree of R-CHI3-DTPA-Gd (in.
Vitro experiment) R-CHI3-DTPA-Gd and D as a comparison target
The relaxation degree of TPA-Gd was measured. The measured concentrations were Gd concentrations of 4, 2, 1 and 0.5 mM. The relationship with the water protons exposed to this compound was determined by NMR (0.5T and 1.5T) to give 37
The relaxation time at T (T1 and T2; msec) was measured, and the relaxation degree (R1 and R2; (mM · S) ^{−1 respectively} ) was calculated based on this value. The results are shown in Table 1. R-CHI3-DTPA-Gd has a good relaxation effect in vitro, and the result is clearly higher than that of the mononuclear complex DTPA-Gd measured by the same method, and its effectiveness is revealed. It was

[0022]

[Table 1]

Example 5 Measurement of Relaxation of R-CHI5-DTPA-Gd (In.
Vitro experiment) R-CHI5-DTPA-Gd and D as a comparison
The relaxation degree of TPA-Gd was measured. The measured concentrations were Gd concentrations of 4, 2, 1 and 0.5 mM. The relationship with the water protons exposed to this compound was measured by NMR (0.5T) as the relaxation time (T1 and T2; msec) at 37 ° C., and the relaxation degree (R1 and R2; (MM ・
S) ^-1 ) was calculated. Table 2 shows the results. R-CHI5
-DTPA-Gd had a good relaxation effect in vitro, and the result was clearly higher than that of the mononuclear complex DTPA-Gd measured by the same method, and the effectiveness was revealed.

[0024]

[Table 2]

(Example 6) Investigation of stability of R-CHI3 The amino group which is a functional group of R-CHI3 is a base in the reaction when the cross-linking chain portion of the bifunctional ligand is, for example, an acid halogen. It is necessary to add a sex catalyst. R-CH in the presence of the present catalyst using potassium carbonate as a basic catalyst
The stability of I3 and chitasan trimer (CHI3) not treated with the reducing end was examined. R-CHI3 and CHI3 (1 g) were each dissolved in a 0.5 M potassium carbonate aqueous solution. Stir at room temperature and perform thin layer chromatography (stationary phase; silica gel 60, mobile phase; chloroform: methanol: ammonia water = 2: 2: 1, detection method;
The stability was examined by the ninhydrin method). Immediately after stirring, R-CHI3 had Rf = 0.08, CHI.
3 was developed to Rf = 0.17. After 12 hours of stirring, R
-CHI3 was developed to Rf = 0.08 similarly to immediately after stirring, but in CHI3, the spot of Rf = 0.17 disappeared, and color was newly recognized at the origin. From this result, it was confirmed that R-CHI3 was stable in a reaction requiring a long time under a basic catalyst.

Example 7 Imaging Effect of R-CHI5-DTPA-Gd on Tumor-Bearing Rats R-CHI5- was applied to Labonar anesthetized female WKA rats (200 g, rat hepatocellular carcinoma kDH-8 was transplanted). DT
PA-Gd solution (0.5M as Gd) was administered by a cannula fixed in the tail vein (0.2 mmol as Gd)
/ Kg) and a nuclear magnetic resonance apparatus (Ome manufactured by Bruker)
Ga-CSI) was fixed in a prone position, and a tumor-bearing site was imaged with a magnetic field intensity of 2 T and an imaging coil for a rat body. The imaging condition is a spin echo method with a slice thickness of 2 mm,
T1 emphasis of resolution 256 × 128 (TR = 600 mse
c, TE = 12 msec). The result is shown in FIG. From this result, R-CHI5-DTPA-G
It was confirmed that d well images the tumor-bearing site of female WKA rats.

[0027]

INDUSTRIAL APPLICABILITY According to the present invention, a nuclear magnetic resonance diagnostic which can be easily produced without inducing unnecessary side reactions during production, is stable, has good solubility in water, and is physiologically acceptable. It has become possible to provide a contrast agent for image diagnosis, which is useful for X-ray diagnosis or radiological diagnosis.

[Brief description of drawings]

FIG. 1 is a photograph (morphological form) showing a tomographic slice of a tumor-bearing site in a rat administered with an R-CHI5-DTPA-Gd solution.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C08B 37/00 Z (72) Inventor Shigemi Seri 1 3 North Kitasue, Sodegaura-shi, Chiba Japan Mediphysics Central Research Institute Co., Ltd.

Claims (9)

[Claims] 1. A molecular weight of 5 in which the reducing end of a sugar chain is subjected to reduction treatment.
At least one of the amino group of the amino oligosaccharide of 0 to 2000 or the aldehyde group of the oligodialdehyde sugar having a molecular weight of 500 to 2000 in which at least one of the constituent monosaccharides is oxidatively cleaved and the reducing end of the sugar chain is subjected to reduction treatment, 1
One or more bifunctional ligands are chemically bonded, and atomic numbers 21 to 29, 31, 32, 37 to
39, 42-44, 49 or 56-83. A contrast agent for diagnostic imaging, comprising a compound in which at least one kind of metal element ion selected from the group is coordinated. 2. The contrast agent for image diagnosis according to claim 1, wherein the aminooligosaccharide to be reduced is chitosan oligosaccharide or galactosamino oligosaccharide. 3. The chitosan oligosaccharide or galactosamino oligosaccharide is a trisaccharide, a tetrasaccharide, a pentasaccharide or a hexasaccharide.
The described contrast agent for diagnostic imaging. 4. The contrast agent for image diagnosis according to claim 1, wherein the oligodialdehyde-modified saccharide is an oxidatively cleaved product of maltooligosaccharide, isomaltooligosaccharide, laminarioligosaccharide, and gentiooligosaccharide having D-glucose as a constituent monosaccharide. 5. The contrast agent for diagnostic imaging according to claim 1, wherein the bifunctional ligand is a linear or cyclic polyaminopolycarboxylic acid. 6. The polyaminopolycarboxylic acid is diethylenetriaminepentaacetic acid, 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid, or 1,4,8,11-tetraazacyclo. Tetradecane
The contrast agent for diagnostic imaging according to claim 5, which is 1,4,8,11-tetraacetic acid or a derivative thereof. 7. Metal element ions are Gd, Dy, Tb, H
o, Er or Fe.
Or the contrast agent for image diagnosis according to any one of 6 above. 8. The metal element ion is Bi, Pb or Os.
The contrast agent for image diagnosis according to any one of claims 1, 2, 3, 4, 5 or 6. 9. The metal element ion is Co, Cu, Ga or G.
e, Sr, Y, Tc, In, Sm, Yb, Re or I
The contrast agent for diagnostic imaging according to any one of claims 1, 2, 3, 4, 5 or 6, which is a radioisotope of r.