CA2160052A1 - Diagnostic imaging agent - Google Patents
Diagnostic imaging agentInfo
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- CA2160052A1 CA2160052A1 CA002160052A CA2160052A CA2160052A1 CA 2160052 A1 CA2160052 A1 CA 2160052A1 CA 002160052 A CA002160052 A CA 002160052A CA 2160052 A CA2160052 A CA 2160052A CA 2160052 A1 CA2160052 A1 CA 2160052A1
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- 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
- A61K49/08—Nuclear magnetic resonance [NMR] contrast preparations; Magnetic resonance imaging [MRI] contrast preparations characterised by the carrier
- A61K49/085—Nuclear magnetic resonance [NMR] contrast preparations; Magnetic resonance imaging [MRI] contrast preparations characterised by the carrier conjugated systems
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- 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
- A61K49/08—Nuclear magnetic resonance [NMR] contrast preparations; Magnetic resonance imaging [MRI] contrast preparations characterised by the carrier
- A61K49/10—Organic compounds
- A61K49/101—Organic compounds the carrier being a complex-forming compound able to form MRI-active complexes with paramagnetic metals
- A61K49/103—Organic compounds the carrier being a complex-forming compound able to form MRI-active complexes with paramagnetic metals the complex-forming compound being acyclic, e.g. DTPA
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- A61K49/00—Preparations for testing in vivo
- A61K49/06—Nuclear magnetic resonance [NMR] contrast preparations; Magnetic resonance imaging [MRI] contrast preparations
- A61K49/08—Nuclear magnetic resonance [NMR] contrast preparations; Magnetic resonance imaging [MRI] contrast preparations characterised by the carrier
- A61K49/10—Organic compounds
- A61K49/101—Organic compounds the carrier being a complex-forming compound able to form MRI-active complexes with paramagnetic metals
- A61K49/106—Organic compounds the carrier being a complex-forming compound able to form MRI-active complexes with paramagnetic metals the complex-forming compound being cyclic, e.g. DOTA
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- A61K51/04—Organic compounds
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- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y5/00—Nanobiotechnology or nanomedicine, e.g. protein engineering or drug delivery
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Abstract
There is disclosed a diagnostic imaging agent which comprises a compound of (a) a complexing agent having at least one ligand chemically coupled to an aldehyde group of a dialdehyde-cyclodextrin wherein at least one constituent monosaccharide cyclodextrin is oxidation-cleaved, coordinated with (b) at least one metal ion selected from the group consisting of metal ions having the atomic number of 21-29, 31, 32, 37-39, 42-44, 49 and 56-83.
Description
21600~ 2 DIAGNOSTI~ I~GING AGENT
FIELD OF THE INVENTION
The present invention relates to a diagnostic imaging ( hereinaf ter sometimes abbreviated as MRI ) agent, in particular, to a diagnostic imaging agent, useful for nuclear magnetic resonance image diagnosis, ~-ray image diagnosis and radiation image diagnosis, containing a metal complex compound having, as its skeleton, an oxidation-cleaved compound of cyclodextrin such as ~-cyclodextrin, ,~-cyclodextrin, r-cyclodextrin and the like.
BACKGROUND OF THE INVENTION
( Diethylenetriaminepentaacetic acid ) gadolinate (hereinafter abbreviated as "DTPA-Gd" ) [~P-A 58-29718]
which is widely used as~ a nuclear magnetic resonance diagnostic imaging agent IS a representative example of mono-metal complexes and effectiveness thereof as a diagnostic imaging agent l~in the ~rain or spinal cord regions has almost been established. However, since DTPA-Gd is complexed, the rela~ivity is lower than that of Gd itself. Therefore, ther~ Ls a need for compensating for the lowered relaxivity with the increased dosage or the like. In addition, DTPAj~ is rapidly excreted into the urine after administratiQn [Hiroki Yoshikawa et al., Gazoshindan, 6, page8 95g-969 (1986)~, and this is very 21600~2 disadvantageous for imaging of several parts of the body by reflecting them in blood stream (blood vessel distribution, blood stream distribution, distribution volume, permeation and the like in a lesion) with a single in ~ection oi the pharmaceutical.
In order to solve these problems, paramagnetic metal complex compounds obtained by introducing a plurality of paramagnetic metal complexes into a carrier polymer have been developed. However, when a polymeric compound having the molecular weight of not less than several thousands i5 used as a carrier, there arise problems such as unnecessarily longer retention in the blood, retention in a living body, antigenicity and the like. Therefore, the prior paramagnetic complex compounds are not necessarily satisfactory. For that reason, a nuclear magnetic resonance imaging agent obtained by coupling a paramagnetic metal complex to an oligosaccharide and polysaccharide having the relatively low molecular weight have been developed [JP-A 5-25059]. However, there still remain the problems that longer total time for synthesis is required because of purification uFon production of an aldehyde group by oxidation-cleavage of constituent D-glucose, and the complicated procedures such as dialysis, ion exchange and the like are required for removing an excess oxidizing ~gent.
: 21600S2 OBJECTS QF THE I~VENTION
The main ob~ect of the present invention is to provide a diagnostic imaging agent, useful for nuclear magnetic resonance image: diagnosis, X-ray diagnosis and radiation diagno~iS, which can be easily prepared without purification procedures upon preparation of the diagnostic imaging agent }~y oxidation-cleavage reaction of saccharide skeleton, the coupling of a netal complex and the like, and which i9 stable, have go9~ solubility in water and is physiologically acceptabIe.
~his ob~ect as ~well as other ob~ects and advantages of the present L=vention will become apparent to those skilled in the art from the following description with reference to the acc~mpanying drawing f7 SUMMARY OF THE INVENTIQI~
In order to solve the above problems, the present inventors studied hard andl as the result, we found that when cyclodextrins are=oxldation-cleaved for a longer period of ~ime, the peroxi~lation dose not occur, thereafter a metal complex compound ca~ be easily coupled thereto, and a metal complex compound obtained by using such the compound as a starting material is a diagnostic imaging agent useful for nuclear~ma~netic resonance image diagnosis, X-ray diagnSi~ ~nd radiation diagnosis, which is sta}~le, has good 801u~lity in water and is : 2160052 ~,, physiologically acceptable.
That is, the present invention provides a diagnostic imaging agent which compri~3es a compound of (a) a complexing agent having at least one ligand chemically coupled to an aldehyde group of a dialdehyde-cyclodextrin wherein at least one constituent monosaccharide cyclodextrin is oxidation-cleaved, coordinated with (b) at least one metal ion selected from the group consisting of metal ions having the atomic number of 21-29, 31, 32, 37-39, 42-44, 49 and 56-83.
The present invention can provide a useful diagnostic imaging agent comprising a compound wherein a metal ion is coordinated to a complexing agent where a ligand is coupled to a novel and particular compound (dialdehyde-cyclodextrin). The diagnostic imaging agent can be easily prepared without purification procedures upon preparation of the diagnostic imaging agent by oxidation-cleavage reaction of saccharide skeleton, the coupling of a metal complex and the like, and is stable, have good solubility in water and is physiologically acceptable.
Therefore, the diagnostic imaging agent is useful for nuclear magnetic resonance image diagnosis, X-ray diagnosLs and radiation diagnosls.
: 2160~2 BRIEF EXPLANATION OF DRAWING
Figure 1 is a MRI showing a transverse view of the cancer-carrying region of a rat after administration of a DA-~-CD-D03MA-Gd solution.
Figure 2 is a MRI showing a transverse view of the cancer-carrying region of a rat after administration of a DA-y-CD-D03MA-Gd solution.
DETAILED DESCRIPTION OF THE INVENTION
Cyclodextrin used in the present invention is a compound obtained by reacting starch with amylase (cyclodextrinase). In the compound, D-glucose molecules are circularly connected via a-1, 4 bonding . When the number of constituent glucose molecules is 6, the compound is called c~-cyclodextrin, when the number of constituent glucose molecules is 7, the compound is called ~-cyclodextrin, and when the number of constituent glucose molecules is 8, the compound is called y-cyclodextrin.
A dialdehyde-compound of cyclodextrin such as ~-cyclodextrin"~-cyclodextrin, y-cyclodextrin and the like is obtained by oxidation-cleavage of a constituent monosaccharide of D-glucose. For example, c~-cyclodextrin is dissolved in water, a small amount of sodium metaperiodate is added thereto in portions under the shielded light while stirring at room temperature, followed by further stirring for 24 hours to obtain dialdehyde-~-: 21~0052 cyclodextrin. As an oxidizing agent, periodic acid (HIO4), potassium periodate (KIO4) and the like are used in addition to sodium metaperiodate ( NaIO4 ) . The reaction is carried out under the conditions of cyclodextrin concentration (1 mmol/1-30 mmol/l), oxidizing agent concentration ( 0 . 02M-0 . 2M), reaction temperature ( 5 C-20 C ), pH ( 3 -5 ), and reaction time ( 1-25 hours ) . These reaction conditions are selected depending upon- the extent of the conversion into dialdehyde by cleavage of constituent monosaccharide cyclodextrin. Usually, it takes about 24 hours to cleave all constituent monosaccharides.
For preparing a diagnostic imaging agent of the present invention, the conversion into dialdehyde is carried out by oxidation-cleavage of saccharides and, thereafter, a bifunctional ligand can be reacted therewith to couple to the saccharide skeleton. Upon this, the saccharide is peroxidized with an oxidizing agent. Upon the coupling reaction of the bifunctional ligand after a step of conversion into dialdehyde, the saccharide is peroxidized by the 1~ ~; n; nq oxidizing agent . These peroxidations disadvantageously lead to the decomposition of the saccharide, which results in decrease in the purity.
For example, it was found that, in the case of oxidation-cleavage of maltopentaose where$n five D-glucose molecules are connected in a linear fashion through o~-1,4 bonding, more than necessary amount of ~odium metaperiodate had already been consumed at 2 hours after the initiation of reaction and therefore, peroxidation had occurred, while in the case of oxidation-cleavage of ~-cyclodextrin, sodium metaperiodate was consumed only at an amount for oxidation-cleaving o~-cyclodextrin even at 48 hours after the initiation of reaction. Llke this, cyclodextrin can be stably converted into dialdehyde by oxidation-cleavage and, even when an excess amount of sodium metaperiodate remains, a next step of labelling ~ metal complex compound can be conducted without decomposition of cyclodextrin.
Therefore, the complicated p~urification procedures become unnecessary during the s~nthesis step and the synthesis procedures can be carried out more simply.
As a complexing~ agent, a linear or cyclic polyaminocarboxylic acid having an activated amino group as a crosslinking chain reactive with an aldehyde group of the above dialdehyde compound o =- cyclodextrin and a bifunctional structure which is capable of trapping a metal ion to form a complex is used. Particularly preferably, a bifunctional complexing agest, having an activated amino group, which is a derivative of DTPA
( diethylenetriaminepentaacetiC acid ), DOTA ( l, 4, 7 ,10-tetraazacyclodocecane-1,4,7,10-tetraacetic acid) or Tl~TA
(l~4~8rll-tetraazacyclo~3~radecane-lr4r8~ll-tetraacetic acid) is used. Particularly, there are : 2~0~2 1- ( p-aminobenzyl ) diethylenetriaminepentaacetic acid [Martin, W.B. et al.: Inorg. Chem., 25, pages 2772-2781 ( 19 8 6 ) ], 2 - ( p-aminobenzyl ) -1, 4, 7, 10 -tetraacetic acid [ U . S .
Patent 4678667], 2-aminobutyl-1,4,7,10-tetraazacyclododecane-l, 4, 7 ,10-tetraacetlc acid [ Parker, D .
et al.: Pure & Appl. Chem., 61, pages 1637-1641 (1989)] and the like.
Dialdehyde-cyclodextrin i8 coupled with the complexing agent according to a known method. As described above, the reaction can be carried out in situ without removing an oxidizing agent used for synthesis of dialdehyde-cyclodextrin. This eliminates the necessity of the complicated purification procedures during the synthesis step, which results in the simpler synthesis procedures. For example, dialdehyde-cyclodextrin is reacted with the complexing agent in an alkaline solution to obtain a compound wherein both of them are coupled through -CH=N-. Alternatively, the complexing agent to which a metal is precomplexed may be used. If necessary, this coupled compound may be reduced to convert -CH=N- into -CH~-NH-. For example, a metal complex compound wherein 1, 4, 7 ,10-tetraazacyclododecane-1-aminoethylcarbamoylmethyl-4,7,10-tris[ (R,S)-methylacetic acid] (hereinafter abbreviated a~ "DO3MA" ) as a bifunctional ligand is coupled to a dialdehyde compound of a~-cyclodextrin (hereinafter abbreviated as " DA-~-CD ) and Gd as a metal ion is 0 216~2 g coordinated therewith can be synthesized according to the f ol lowing procedures:
Sodium metaperiodate is added to an aqueous solution of r~L-cyclodextrin to effect an oxidation-cleave, S DO3MA wherein Gd is coordinated therewith (hereinafter abbreviated as " DO3MA-Gd ) according to the conventional method Ls added thereto, and triethylamine is added thereto as an accelerator to stir. In order to reduce the resulting Schiff base, sodium borohydride is added to the reaction solution to stir, followed by purification by dialysis to obtain DA-c~-CD-DO3MA-Gd. Since the use of cyclodextrin eliminates the necessity of the purification procedures during the reaction, it not only facilitates the synthesis but also improves the yield and, as the result, reduces the cost.
The metal ion used in the present invention is selected from the group consisting of metal ions having the atomic number of 21-29, 31, 32, 37-39, 42-44, 49 and 56-83 depending upon a particular use of image diagnosis. When the diagnostic Lmaging agent of the present invention is used for nuclear magnetic resonance image diagnosis, the metal ion must be paramagnetic and selected from lanthanide ions having the atomic number of 26 and 57-70, and Gd, Dy, Tb, Ho, Er and Fe being preferable. When the diagnostic imaging agent of the present invention is used for X-ray image di~gnosis, the metal ion is selected from the group : 21~0052 conslsting of lanthanide ions having the atomic number of 57-70 and metal ions having the atomic number of 56, 76, 82 and 83. Among them, Bi, Pb and Os ion are preferable.
When used as a radiation diagnostic imaging agent, the metal ion must be radioactive and radioactive metal ions:
Co, Cu, ~a, Ge, Sr, Y, Tc, In, Sm, Gd, Yb, Re and Ir ion are suitable. The metal ion to be used may be resulted from a metal per se or an inorganic compound containing such the metal (for example, chloride, oxide and the like).
l O The complexing can be carried out according to a conventional method.
In the metal complex compound thus obtained, at least one complexing agent is chemically coupled to a dialdehyde-compound whereln at least one, preferably, two or more constituent saccharides of o-cyclodextrin, ,0-cyclodextrin and ~-cycLodextrin are oxidation-cleaved, and a metal ion is coupled thereto by complexation.
An amount of the diagnostic imaging agent of the present invention to be used is selected depending upon a particular use of image diagnosis. For example, when used as a nuclear magnetic resonance imaging agent, the dose of the metal ion is generally 0 . 005 to 5 mmol/kg, preferably 0 . 01 to 0 . 5 mmol/kg . When used as a X-ray diagnostic imaging agent, the dose of the metal ion is 0 . 01 to 10 mmol/kg, preferably 0.1 to l mmol/kg. When used as a radiation diagnostic agent, the dose is 370-18500 MBq 2~600~2 radioactivity. Usually, the diagnostic imaging agent of the present invention is administered intravenously and, in some cases, may be administered orally or intra-arterially .
At 1 hour after DA-~-CD-DO3MA-Gd which is the diagnostic imaging agent of the present invention was administered to a cancer-carrying rat, the cancer part was clearly imaged and, thus, in vivo imaging effects and retention in the blood were confirmed. In addition, it was also confirmed that Tl relaxivity (intensity of magnetic field: 6.35~, 25C) in water was remarkably increased to 8.6 (mM-S), about two times of that of DTPA-Gd.
Retention in the blood of the diagnostic imaging agent of the present invention is in a clinically effective range (half-life period in blood of 0.5-5 hours).
This is effective for improving the collection efficacy of proton relaxation effect by the imaging agent, for example, in the case of a lower magnetic field intensity MRI
apparatus in which imaging requires longer period of time in comparison with a higher magnetic field intensity MRI
apparatus. In addition, the higher imaging effect per unit dosage is advantageous. For example, since the shortening effect of the relaxation time per molecule is predominantly stronger than that of DTPA-Gd, the present diagnostic imaging agent can be used advantageously as a nuclear magnetic resonance imaging agent. In addition, in the case 21600~2 of diagnosis using a lower magnetic field intensity MRI
apparatus having the lower collecting efficacy of proton relaxation effect, since the present diagnostic imaging agent has the higher imaging efficacy per unit dosage, the detection effect is improved and a time necessary for imaging can be shortened. Furthermore, when the same imaging effect as that of DTPA-Gd in an apparatus having the same magnetic field intensity is required, the present diagnostic imaging agent can be administered in a smaller dose than that of DTPA-Gd and, therefore, becomes more advantageous from the standpoint of safety. To the contrary, at the same dose, the present diagnostic imaging agent provides much more information about a living body than DTPA-Gd, resulting in the improvement in the clinical usefulness. Therefore, the present invention can provide an imaging agent having appropriate retention in the blood and effectively enhanced efficacy, which matches the magnetic field intensity of a MRI spectrometer or imaging conditions .
Further, since the diagnostic imaging agent of the present invention shows appropriate retention in the blood, a blood vessel distribution image (vascularity) can be evaluated. Therefore, since the diagnostic imaging agent of the present invention can image the blood vessel for recently Ll ~rkAhly advanced MR angiography without particular pulse sequence, the agent is also useful as a 216~0~2 transvenous diagnostic imaging agent. Further, since the present diagnostic imaging agent has good solubility in water, the agent as such can be prepared into a solution containing the agent in a high concentration. Accordingly, a solubilizer is not necessarily required upon preparation of the solution. In addition, the present diagnostic imaging agent is a poly-chelates compound and, therefore, can decrease the total molality in the preparation of a solution in comparison with the mono-chelate compound, which results in decrease in the osmotic pressure. These alleviate the load to volume of the circulatory system or body f luid equilibrium upon administration in the living body, which resulting in advantage in the safety.
The diagnostic imaging agent of the present invention is prepared by dissolving in distilled water for injection or a physiologically acceptable aqueous solvent.
If necessary, a pH ad justing agent or a solubilizer may be added therein. Examples of the pH ad~usting agent are NaOH, HCl and the like. Examples of the solubilizer are tri-N-methylglucamine and the like.
The following Examples further illustrate the present invention in detail but are not to be construed to limit the scope thereof.
The abbreviations used in Examples mean as follows:
21fi~S2 DTEN: 1- ( p-aminobenzyl ) diethylenetriaminepentaacetic acid DO3MA: 1, 4, 7 ,10-tetraazacyclododecane-1-aminoethylcarbamoylmethyl-4, 7, 10 -tris [ ( R, S ) -5 methylacetic acid ]
DA~ CD: dialdehyde-~-cyclodextrin DA-y-CD: dialdehyde-y-cyclodextrin The composition was analyzed as follows:
C, H and N were analyzed using elementary analysis, a metal ion was analyzed using induced coupling high fre~uency plasma analysis. The results are represented by wt%. Wt% of oxygen was obtained by subtracting these wt~'s from 100%. The number of coupled metal ions was calculated using a ratio relative to the content of the metal ion which coordinates to all constituent mono saccharide o~ each cyclodextrin.
Example l Oxidation-cleavage of c~-cyclodextrin or maltopentaose .
Comparative experiment of oxidation-cleavage was carried out using ~-cyclodextrin as a cyclodextrin or maltopentaose as a linear polysaccharide.
~-Cyclodextrin (1.20 g; 1.24 mmol) was dissolved in water (10 ml), followed by stirring at room temperature.
Under the shielded light, 0.2N sodium metaperiodate (45 ml) was added thereto in portions, followed by continuous 2160~52 _ 15 --stirring. Separately, maltopentaose (1.10 g; 1.33 mmol) was dissolved in water ( 10ml ) to stir at room temperature.
Under the shielded light, 0.2N sodium metaperiodate (55 ml) was added thereto in portions, followed by continuous stirring. Each 0 . 5 ml aliquot was taken from each reaction solution in course of time, and an amount of consumed periodic acid was determined using Flaury-Lange method [P.F.Flery, J.Lange, J.Pharm., 17, 107, 196 (1933) ] . As the result, in the case of ~-cyclodextrin reaction solution, an amount of consumed periodic acid was increased in course of time after addition of sodium metaperiodate, a necessary amount for cleaving all constituent saccharides was consumed after 24 hours and, thereafter, no increase in the consumed amount was observed. On the other hand, in the case of maltopentaose reaction solution, an amount of consumed periodic acid was similarly increased and a necessary amount for cleaving all constituent saccharLdes was consumed at 2 hours after addition. ~hereafter, the consumed amount however continued to increase, and about l . 4 times periodic acid was consumed at 24 hours after addition in comparison with at 2 hours after addition.
Thus, in the latter case, it was confirmed that peroxidation reaction by excess periodic acid proceeded.
The results of experiment are shown in Table 1.
~ 216~2 Table 1 Oxidation-cleavage by sodium metaperiodate Amount of consumed Theoretical periodic acid (mmol ) amount consumed Reaction 15min, 30min, lhr, 2hr, 3hr, 24hr,48hr time A - 1.29 3.00 3.71 5.18 7.44 7.44 7.44 B 4.65 5.32 5.98 6.65 7.30 9.31 - 6.65 A: a-cyclodextrin B: maltopentaose Example 2 Synthesis of DA-a-CD-DTEN-Gd a-Cyclodextrin (1.2 g; 1.24 mmol) was dissolved in water ( 9 ml ) to stir at room temper~ture . Under the shielded light, 0.2N sodium metaperiadate (44 ml) was added thereto in portions to stir for 24 hours. Then, DTEN (2.9 g; 5.9 mmol) was added thereto, followed by addition of triethylamine (0.18 ml). After stirred for 24 hours, sodium borohydride (2.8 g) was added thereto to stir ior 24 hours. The reaction solution was ad~usted to pH 2 with hydrochloric acid and an aqueous sodium hydroxide solution was added to ad~ust the solution to neutral. GdCl~-6H~O
(2.4 g; 6.5 mmol) was added to react while stirring at room temperature, and the white precipitates were removed by concentration, followed 3:~y dialysis (fraction molecular weight: 1000) to obtain DA-a-CD-DTEN-Gd (0.74 g).
Elementary analysis: C 38.0 wt%; H 7.2 wt%; N 9.0 wt%.
Gd content: 13.9 wt%, Coupled number of Gd: 4.3 ExamPle 3 Synthesis of DA-a-CD-DO3MA-Gd 2~60~52 c~-Cyclodextrin (2.70 g; 2.78 mmol) was dissolved in water ( 20 ml ) to stir at room temperature. Under the shielded light, 0.2N sodium metaperiodate (100 ml) was added thereto in portions to stir for 24 hours. Then, DO3MA-Gd (8.68 g; 13.5 mmol) was added thereto, followed by addition of triethylamine ( 0 . 40 ml ) . After stirred for 24 hours, sodium borohydride (6.38 g) was added thereto to stir for 24 hours. The reaction solution was ad~usted to pH 2 with hydrochloric acid, an aqueous sodium hydroxide solution was added to adjust the solution to neutral, and white precipitates were removed by concentration, followed by dialysis (fraction molecular weight: 1000) to obtain DA-~-CD-DO3MA-Gd ( 1 . 9 7 g ) .
Elementary analysis: C 38.2 wt%; H 7.3 wt%; N 9.3 wt%
Gd content: 14.8 wt96, Coupled number of Gd: 4.5 Example 4 Synthesis of DA-y-CD-DO3MA-Gd Substantially the same manner as that in Example 3 except that ~-cyclodextrin was used instead of ~-cyclodextrin afforded DA-~y-CD-DO3MA-Gd (1.68 g).
Élementary analysis: C 38.0 wt%; H 7.3 wt%; N 9.8 wt%
Gd content: 15.5 wt%, Gd binding number: 6.2 ExamPle 5 Synthesis of DA-!3-CD-DO3MA-Bi !3-Cyclodextrin (0.20 g; 0.18 mmol) was dissolved in water ( 2 ml ) to stir at room temperature . Under the . 21~00~2 shielded light, 0.2N sodium metaperiodate (8 ml) was added thereto in portions to stir for 24 hours. Then, Do3MA-Bi (1.04 g; 1.5 mmoI) was added thereto, followed by addition of triethylamine (0.04 ml). After stirred for 24 hours, sodium borohydride (0.6 g) was added thereto to stir for 24 hours . The reaction solution was ad justed to pH 2 with hydrochloric acid, an aqueous sodium hydroxide solution was added to adjust the solution to neutral, and the white precipitates were removed by concentration, followed by dialysis (fraction molecular weight: 1000) to obtain DA-~3-CD-DO3MA-Bi (0.48 g) .
Bi content: 17.7 wt~, Coupled number of Bi: 4.3 Example 6 Relaxivity (in vitro) of DA-~-CD-DO3MA-Gd and DA-y-CD-DO3MA-Gd DA-~-CD-DO3MA-Gd or DA-~-CD-DO3MA-Gd was dissolved in distilled water in terms of Gd concentration:
5, 2.5, 1.25 and 0.625 mM, respectively. Relaxation time of each compound at 37C (Tl and T2; msec) was determined using NMR (0.5T and 1.5T). Tl relaxivity and T2 relaxivity (Rl and R2, (mM-S)~I, respectively) were calculated from relaxation time values. The results are shown in Table 2.
The values are per one Gd molecule. DA-~-CD-D03MA-Gd and DA-~y-CD-DO3MA-Gd have good relaxation effect in vitro, which is predominantly higher than that of DTPA-Gd ( also shown in Table 2 ), of a mono-chelate complex, measured 60~2 according to the same method . Thus, the ef ficacy of the compound in the present invention was confirmed.
Table 2 Relaxivity (in vitro) of DA-~-CD-DO3MA-Gd and DA-y-CD-DO3MA-Gd Compound Rl (mM-S ) R2 (mM-S ) lODA-~-CD-DO3MA-Gd 8 . 6 10 . 8 DA-y-CD-DO3MA-Gd 8 . 4 10 . 8 15DTPA-Gd 3 . 7 4 . 5 Example 7 Preparation of a 0 . 5 M solution of DA-o;-CD-DO3MA-Gd or DA-y-CD-DO3MA-Gd DA-c~-CD-DO3MA-Gd (1.0 g) was weighed and water for in~ection was added thereto at an appropriate amount to obtain a 0.5M (Gd concentration) solution of DA-~-CD-DO3MA-Gd .
DA-y-CD-DO3MA-Gd ( 1. 0 g ) was weighed and water for in~ection was added thereto at an appropriate amount to obtain a 0.5M (Gd concentration) solution of DA-y-CD-DO3MA-Gd. Both compounds could be prepared into a solution having the higher neccesary concentration without the u~e of a solubilizer.
ExamPle 8 Imaging effect (in vivo) in a cancer-carrying rat after intravenous administration of DA-~-CD-DO3MA-Gd or DA-y -CD-DO3MA-Gd 21600~2 . ~
_ 20 --A solution of DA-a-CD-DO3MA-Gd or DA-~-CD-DO3MA-Gd was administered to male WKA rats ( 284-287 g, transplanted with rat hepatic cells cancer kDE~-8 ) anesthetized with ravonal, via a cannula fixed to tail vein (0.2 mmol (Gd)/kg). The rats were fixed prone in the magnetic field of a MRI apparatus and each cancer-carrying region was imaged.
The apparatus (Omega CSI manufactured by Bruker) had a magnetic field intensity of 2 . 0T and, as an imaging coil, a rat Body coil was used. Imaging was carried out according to spin echo method of rl weighed (I~R/TE: 600/12 msec) under the condition of 2 mm in slice thickness, a resolution of 256 x 128.
The results are shown in Figures 1 and 2.
FIELD OF THE INVENTION
The present invention relates to a diagnostic imaging ( hereinaf ter sometimes abbreviated as MRI ) agent, in particular, to a diagnostic imaging agent, useful for nuclear magnetic resonance image diagnosis, ~-ray image diagnosis and radiation image diagnosis, containing a metal complex compound having, as its skeleton, an oxidation-cleaved compound of cyclodextrin such as ~-cyclodextrin, ,~-cyclodextrin, r-cyclodextrin and the like.
BACKGROUND OF THE INVENTION
( Diethylenetriaminepentaacetic acid ) gadolinate (hereinafter abbreviated as "DTPA-Gd" ) [~P-A 58-29718]
which is widely used as~ a nuclear magnetic resonance diagnostic imaging agent IS a representative example of mono-metal complexes and effectiveness thereof as a diagnostic imaging agent l~in the ~rain or spinal cord regions has almost been established. However, since DTPA-Gd is complexed, the rela~ivity is lower than that of Gd itself. Therefore, ther~ Ls a need for compensating for the lowered relaxivity with the increased dosage or the like. In addition, DTPAj~ is rapidly excreted into the urine after administratiQn [Hiroki Yoshikawa et al., Gazoshindan, 6, page8 95g-969 (1986)~, and this is very 21600~2 disadvantageous for imaging of several parts of the body by reflecting them in blood stream (blood vessel distribution, blood stream distribution, distribution volume, permeation and the like in a lesion) with a single in ~ection oi the pharmaceutical.
In order to solve these problems, paramagnetic metal complex compounds obtained by introducing a plurality of paramagnetic metal complexes into a carrier polymer have been developed. However, when a polymeric compound having the molecular weight of not less than several thousands i5 used as a carrier, there arise problems such as unnecessarily longer retention in the blood, retention in a living body, antigenicity and the like. Therefore, the prior paramagnetic complex compounds are not necessarily satisfactory. For that reason, a nuclear magnetic resonance imaging agent obtained by coupling a paramagnetic metal complex to an oligosaccharide and polysaccharide having the relatively low molecular weight have been developed [JP-A 5-25059]. However, there still remain the problems that longer total time for synthesis is required because of purification uFon production of an aldehyde group by oxidation-cleavage of constituent D-glucose, and the complicated procedures such as dialysis, ion exchange and the like are required for removing an excess oxidizing ~gent.
: 21600S2 OBJECTS QF THE I~VENTION
The main ob~ect of the present invention is to provide a diagnostic imaging agent, useful for nuclear magnetic resonance image: diagnosis, X-ray diagnosis and radiation diagno~iS, which can be easily prepared without purification procedures upon preparation of the diagnostic imaging agent }~y oxidation-cleavage reaction of saccharide skeleton, the coupling of a netal complex and the like, and which i9 stable, have go9~ solubility in water and is physiologically acceptabIe.
~his ob~ect as ~well as other ob~ects and advantages of the present L=vention will become apparent to those skilled in the art from the following description with reference to the acc~mpanying drawing f7 SUMMARY OF THE INVENTIQI~
In order to solve the above problems, the present inventors studied hard andl as the result, we found that when cyclodextrins are=oxldation-cleaved for a longer period of ~ime, the peroxi~lation dose not occur, thereafter a metal complex compound ca~ be easily coupled thereto, and a metal complex compound obtained by using such the compound as a starting material is a diagnostic imaging agent useful for nuclear~ma~netic resonance image diagnosis, X-ray diagnSi~ ~nd radiation diagnosis, which is sta}~le, has good 801u~lity in water and is : 2160052 ~,, physiologically acceptable.
That is, the present invention provides a diagnostic imaging agent which compri~3es a compound of (a) a complexing agent having at least one ligand chemically coupled to an aldehyde group of a dialdehyde-cyclodextrin wherein at least one constituent monosaccharide cyclodextrin is oxidation-cleaved, coordinated with (b) at least one metal ion selected from the group consisting of metal ions having the atomic number of 21-29, 31, 32, 37-39, 42-44, 49 and 56-83.
The present invention can provide a useful diagnostic imaging agent comprising a compound wherein a metal ion is coordinated to a complexing agent where a ligand is coupled to a novel and particular compound (dialdehyde-cyclodextrin). The diagnostic imaging agent can be easily prepared without purification procedures upon preparation of the diagnostic imaging agent by oxidation-cleavage reaction of saccharide skeleton, the coupling of a metal complex and the like, and is stable, have good solubility in water and is physiologically acceptable.
Therefore, the diagnostic imaging agent is useful for nuclear magnetic resonance image diagnosis, X-ray diagnosLs and radiation diagnosls.
: 2160~2 BRIEF EXPLANATION OF DRAWING
Figure 1 is a MRI showing a transverse view of the cancer-carrying region of a rat after administration of a DA-~-CD-D03MA-Gd solution.
Figure 2 is a MRI showing a transverse view of the cancer-carrying region of a rat after administration of a DA-y-CD-D03MA-Gd solution.
DETAILED DESCRIPTION OF THE INVENTION
Cyclodextrin used in the present invention is a compound obtained by reacting starch with amylase (cyclodextrinase). In the compound, D-glucose molecules are circularly connected via a-1, 4 bonding . When the number of constituent glucose molecules is 6, the compound is called c~-cyclodextrin, when the number of constituent glucose molecules is 7, the compound is called ~-cyclodextrin, and when the number of constituent glucose molecules is 8, the compound is called y-cyclodextrin.
A dialdehyde-compound of cyclodextrin such as ~-cyclodextrin"~-cyclodextrin, y-cyclodextrin and the like is obtained by oxidation-cleavage of a constituent monosaccharide of D-glucose. For example, c~-cyclodextrin is dissolved in water, a small amount of sodium metaperiodate is added thereto in portions under the shielded light while stirring at room temperature, followed by further stirring for 24 hours to obtain dialdehyde-~-: 21~0052 cyclodextrin. As an oxidizing agent, periodic acid (HIO4), potassium periodate (KIO4) and the like are used in addition to sodium metaperiodate ( NaIO4 ) . The reaction is carried out under the conditions of cyclodextrin concentration (1 mmol/1-30 mmol/l), oxidizing agent concentration ( 0 . 02M-0 . 2M), reaction temperature ( 5 C-20 C ), pH ( 3 -5 ), and reaction time ( 1-25 hours ) . These reaction conditions are selected depending upon- the extent of the conversion into dialdehyde by cleavage of constituent monosaccharide cyclodextrin. Usually, it takes about 24 hours to cleave all constituent monosaccharides.
For preparing a diagnostic imaging agent of the present invention, the conversion into dialdehyde is carried out by oxidation-cleavage of saccharides and, thereafter, a bifunctional ligand can be reacted therewith to couple to the saccharide skeleton. Upon this, the saccharide is peroxidized with an oxidizing agent. Upon the coupling reaction of the bifunctional ligand after a step of conversion into dialdehyde, the saccharide is peroxidized by the 1~ ~; n; nq oxidizing agent . These peroxidations disadvantageously lead to the decomposition of the saccharide, which results in decrease in the purity.
For example, it was found that, in the case of oxidation-cleavage of maltopentaose where$n five D-glucose molecules are connected in a linear fashion through o~-1,4 bonding, more than necessary amount of ~odium metaperiodate had already been consumed at 2 hours after the initiation of reaction and therefore, peroxidation had occurred, while in the case of oxidation-cleavage of ~-cyclodextrin, sodium metaperiodate was consumed only at an amount for oxidation-cleaving o~-cyclodextrin even at 48 hours after the initiation of reaction. Llke this, cyclodextrin can be stably converted into dialdehyde by oxidation-cleavage and, even when an excess amount of sodium metaperiodate remains, a next step of labelling ~ metal complex compound can be conducted without decomposition of cyclodextrin.
Therefore, the complicated p~urification procedures become unnecessary during the s~nthesis step and the synthesis procedures can be carried out more simply.
As a complexing~ agent, a linear or cyclic polyaminocarboxylic acid having an activated amino group as a crosslinking chain reactive with an aldehyde group of the above dialdehyde compound o =- cyclodextrin and a bifunctional structure which is capable of trapping a metal ion to form a complex is used. Particularly preferably, a bifunctional complexing agest, having an activated amino group, which is a derivative of DTPA
( diethylenetriaminepentaacetiC acid ), DOTA ( l, 4, 7 ,10-tetraazacyclodocecane-1,4,7,10-tetraacetic acid) or Tl~TA
(l~4~8rll-tetraazacyclo~3~radecane-lr4r8~ll-tetraacetic acid) is used. Particularly, there are : 2~0~2 1- ( p-aminobenzyl ) diethylenetriaminepentaacetic acid [Martin, W.B. et al.: Inorg. Chem., 25, pages 2772-2781 ( 19 8 6 ) ], 2 - ( p-aminobenzyl ) -1, 4, 7, 10 -tetraacetic acid [ U . S .
Patent 4678667], 2-aminobutyl-1,4,7,10-tetraazacyclododecane-l, 4, 7 ,10-tetraacetlc acid [ Parker, D .
et al.: Pure & Appl. Chem., 61, pages 1637-1641 (1989)] and the like.
Dialdehyde-cyclodextrin i8 coupled with the complexing agent according to a known method. As described above, the reaction can be carried out in situ without removing an oxidizing agent used for synthesis of dialdehyde-cyclodextrin. This eliminates the necessity of the complicated purification procedures during the synthesis step, which results in the simpler synthesis procedures. For example, dialdehyde-cyclodextrin is reacted with the complexing agent in an alkaline solution to obtain a compound wherein both of them are coupled through -CH=N-. Alternatively, the complexing agent to which a metal is precomplexed may be used. If necessary, this coupled compound may be reduced to convert -CH=N- into -CH~-NH-. For example, a metal complex compound wherein 1, 4, 7 ,10-tetraazacyclododecane-1-aminoethylcarbamoylmethyl-4,7,10-tris[ (R,S)-methylacetic acid] (hereinafter abbreviated a~ "DO3MA" ) as a bifunctional ligand is coupled to a dialdehyde compound of a~-cyclodextrin (hereinafter abbreviated as " DA-~-CD ) and Gd as a metal ion is 0 216~2 g coordinated therewith can be synthesized according to the f ol lowing procedures:
Sodium metaperiodate is added to an aqueous solution of r~L-cyclodextrin to effect an oxidation-cleave, S DO3MA wherein Gd is coordinated therewith (hereinafter abbreviated as " DO3MA-Gd ) according to the conventional method Ls added thereto, and triethylamine is added thereto as an accelerator to stir. In order to reduce the resulting Schiff base, sodium borohydride is added to the reaction solution to stir, followed by purification by dialysis to obtain DA-c~-CD-DO3MA-Gd. Since the use of cyclodextrin eliminates the necessity of the purification procedures during the reaction, it not only facilitates the synthesis but also improves the yield and, as the result, reduces the cost.
The metal ion used in the present invention is selected from the group consisting of metal ions having the atomic number of 21-29, 31, 32, 37-39, 42-44, 49 and 56-83 depending upon a particular use of image diagnosis. When the diagnostic Lmaging agent of the present invention is used for nuclear magnetic resonance image diagnosis, the metal ion must be paramagnetic and selected from lanthanide ions having the atomic number of 26 and 57-70, and Gd, Dy, Tb, Ho, Er and Fe being preferable. When the diagnostic imaging agent of the present invention is used for X-ray image di~gnosis, the metal ion is selected from the group : 21~0052 conslsting of lanthanide ions having the atomic number of 57-70 and metal ions having the atomic number of 56, 76, 82 and 83. Among them, Bi, Pb and Os ion are preferable.
When used as a radiation diagnostic imaging agent, the metal ion must be radioactive and radioactive metal ions:
Co, Cu, ~a, Ge, Sr, Y, Tc, In, Sm, Gd, Yb, Re and Ir ion are suitable. The metal ion to be used may be resulted from a metal per se or an inorganic compound containing such the metal (for example, chloride, oxide and the like).
l O The complexing can be carried out according to a conventional method.
In the metal complex compound thus obtained, at least one complexing agent is chemically coupled to a dialdehyde-compound whereln at least one, preferably, two or more constituent saccharides of o-cyclodextrin, ,0-cyclodextrin and ~-cycLodextrin are oxidation-cleaved, and a metal ion is coupled thereto by complexation.
An amount of the diagnostic imaging agent of the present invention to be used is selected depending upon a particular use of image diagnosis. For example, when used as a nuclear magnetic resonance imaging agent, the dose of the metal ion is generally 0 . 005 to 5 mmol/kg, preferably 0 . 01 to 0 . 5 mmol/kg . When used as a X-ray diagnostic imaging agent, the dose of the metal ion is 0 . 01 to 10 mmol/kg, preferably 0.1 to l mmol/kg. When used as a radiation diagnostic agent, the dose is 370-18500 MBq 2~600~2 radioactivity. Usually, the diagnostic imaging agent of the present invention is administered intravenously and, in some cases, may be administered orally or intra-arterially .
At 1 hour after DA-~-CD-DO3MA-Gd which is the diagnostic imaging agent of the present invention was administered to a cancer-carrying rat, the cancer part was clearly imaged and, thus, in vivo imaging effects and retention in the blood were confirmed. In addition, it was also confirmed that Tl relaxivity (intensity of magnetic field: 6.35~, 25C) in water was remarkably increased to 8.6 (mM-S), about two times of that of DTPA-Gd.
Retention in the blood of the diagnostic imaging agent of the present invention is in a clinically effective range (half-life period in blood of 0.5-5 hours).
This is effective for improving the collection efficacy of proton relaxation effect by the imaging agent, for example, in the case of a lower magnetic field intensity MRI
apparatus in which imaging requires longer period of time in comparison with a higher magnetic field intensity MRI
apparatus. In addition, the higher imaging effect per unit dosage is advantageous. For example, since the shortening effect of the relaxation time per molecule is predominantly stronger than that of DTPA-Gd, the present diagnostic imaging agent can be used advantageously as a nuclear magnetic resonance imaging agent. In addition, in the case 21600~2 of diagnosis using a lower magnetic field intensity MRI
apparatus having the lower collecting efficacy of proton relaxation effect, since the present diagnostic imaging agent has the higher imaging efficacy per unit dosage, the detection effect is improved and a time necessary for imaging can be shortened. Furthermore, when the same imaging effect as that of DTPA-Gd in an apparatus having the same magnetic field intensity is required, the present diagnostic imaging agent can be administered in a smaller dose than that of DTPA-Gd and, therefore, becomes more advantageous from the standpoint of safety. To the contrary, at the same dose, the present diagnostic imaging agent provides much more information about a living body than DTPA-Gd, resulting in the improvement in the clinical usefulness. Therefore, the present invention can provide an imaging agent having appropriate retention in the blood and effectively enhanced efficacy, which matches the magnetic field intensity of a MRI spectrometer or imaging conditions .
Further, since the diagnostic imaging agent of the present invention shows appropriate retention in the blood, a blood vessel distribution image (vascularity) can be evaluated. Therefore, since the diagnostic imaging agent of the present invention can image the blood vessel for recently Ll ~rkAhly advanced MR angiography without particular pulse sequence, the agent is also useful as a 216~0~2 transvenous diagnostic imaging agent. Further, since the present diagnostic imaging agent has good solubility in water, the agent as such can be prepared into a solution containing the agent in a high concentration. Accordingly, a solubilizer is not necessarily required upon preparation of the solution. In addition, the present diagnostic imaging agent is a poly-chelates compound and, therefore, can decrease the total molality in the preparation of a solution in comparison with the mono-chelate compound, which results in decrease in the osmotic pressure. These alleviate the load to volume of the circulatory system or body f luid equilibrium upon administration in the living body, which resulting in advantage in the safety.
The diagnostic imaging agent of the present invention is prepared by dissolving in distilled water for injection or a physiologically acceptable aqueous solvent.
If necessary, a pH ad justing agent or a solubilizer may be added therein. Examples of the pH ad~usting agent are NaOH, HCl and the like. Examples of the solubilizer are tri-N-methylglucamine and the like.
The following Examples further illustrate the present invention in detail but are not to be construed to limit the scope thereof.
The abbreviations used in Examples mean as follows:
21fi~S2 DTEN: 1- ( p-aminobenzyl ) diethylenetriaminepentaacetic acid DO3MA: 1, 4, 7 ,10-tetraazacyclododecane-1-aminoethylcarbamoylmethyl-4, 7, 10 -tris [ ( R, S ) -5 methylacetic acid ]
DA~ CD: dialdehyde-~-cyclodextrin DA-y-CD: dialdehyde-y-cyclodextrin The composition was analyzed as follows:
C, H and N were analyzed using elementary analysis, a metal ion was analyzed using induced coupling high fre~uency plasma analysis. The results are represented by wt%. Wt% of oxygen was obtained by subtracting these wt~'s from 100%. The number of coupled metal ions was calculated using a ratio relative to the content of the metal ion which coordinates to all constituent mono saccharide o~ each cyclodextrin.
Example l Oxidation-cleavage of c~-cyclodextrin or maltopentaose .
Comparative experiment of oxidation-cleavage was carried out using ~-cyclodextrin as a cyclodextrin or maltopentaose as a linear polysaccharide.
~-Cyclodextrin (1.20 g; 1.24 mmol) was dissolved in water (10 ml), followed by stirring at room temperature.
Under the shielded light, 0.2N sodium metaperiodate (45 ml) was added thereto in portions, followed by continuous 2160~52 _ 15 --stirring. Separately, maltopentaose (1.10 g; 1.33 mmol) was dissolved in water ( 10ml ) to stir at room temperature.
Under the shielded light, 0.2N sodium metaperiodate (55 ml) was added thereto in portions, followed by continuous stirring. Each 0 . 5 ml aliquot was taken from each reaction solution in course of time, and an amount of consumed periodic acid was determined using Flaury-Lange method [P.F.Flery, J.Lange, J.Pharm., 17, 107, 196 (1933) ] . As the result, in the case of ~-cyclodextrin reaction solution, an amount of consumed periodic acid was increased in course of time after addition of sodium metaperiodate, a necessary amount for cleaving all constituent saccharides was consumed after 24 hours and, thereafter, no increase in the consumed amount was observed. On the other hand, in the case of maltopentaose reaction solution, an amount of consumed periodic acid was similarly increased and a necessary amount for cleaving all constituent saccharLdes was consumed at 2 hours after addition. ~hereafter, the consumed amount however continued to increase, and about l . 4 times periodic acid was consumed at 24 hours after addition in comparison with at 2 hours after addition.
Thus, in the latter case, it was confirmed that peroxidation reaction by excess periodic acid proceeded.
The results of experiment are shown in Table 1.
~ 216~2 Table 1 Oxidation-cleavage by sodium metaperiodate Amount of consumed Theoretical periodic acid (mmol ) amount consumed Reaction 15min, 30min, lhr, 2hr, 3hr, 24hr,48hr time A - 1.29 3.00 3.71 5.18 7.44 7.44 7.44 B 4.65 5.32 5.98 6.65 7.30 9.31 - 6.65 A: a-cyclodextrin B: maltopentaose Example 2 Synthesis of DA-a-CD-DTEN-Gd a-Cyclodextrin (1.2 g; 1.24 mmol) was dissolved in water ( 9 ml ) to stir at room temper~ture . Under the shielded light, 0.2N sodium metaperiadate (44 ml) was added thereto in portions to stir for 24 hours. Then, DTEN (2.9 g; 5.9 mmol) was added thereto, followed by addition of triethylamine (0.18 ml). After stirred for 24 hours, sodium borohydride (2.8 g) was added thereto to stir ior 24 hours. The reaction solution was ad~usted to pH 2 with hydrochloric acid and an aqueous sodium hydroxide solution was added to ad~ust the solution to neutral. GdCl~-6H~O
(2.4 g; 6.5 mmol) was added to react while stirring at room temperature, and the white precipitates were removed by concentration, followed 3:~y dialysis (fraction molecular weight: 1000) to obtain DA-a-CD-DTEN-Gd (0.74 g).
Elementary analysis: C 38.0 wt%; H 7.2 wt%; N 9.0 wt%.
Gd content: 13.9 wt%, Coupled number of Gd: 4.3 ExamPle 3 Synthesis of DA-a-CD-DO3MA-Gd 2~60~52 c~-Cyclodextrin (2.70 g; 2.78 mmol) was dissolved in water ( 20 ml ) to stir at room temperature. Under the shielded light, 0.2N sodium metaperiodate (100 ml) was added thereto in portions to stir for 24 hours. Then, DO3MA-Gd (8.68 g; 13.5 mmol) was added thereto, followed by addition of triethylamine ( 0 . 40 ml ) . After stirred for 24 hours, sodium borohydride (6.38 g) was added thereto to stir for 24 hours. The reaction solution was ad~usted to pH 2 with hydrochloric acid, an aqueous sodium hydroxide solution was added to adjust the solution to neutral, and white precipitates were removed by concentration, followed by dialysis (fraction molecular weight: 1000) to obtain DA-~-CD-DO3MA-Gd ( 1 . 9 7 g ) .
Elementary analysis: C 38.2 wt%; H 7.3 wt%; N 9.3 wt%
Gd content: 14.8 wt96, Coupled number of Gd: 4.5 Example 4 Synthesis of DA-y-CD-DO3MA-Gd Substantially the same manner as that in Example 3 except that ~-cyclodextrin was used instead of ~-cyclodextrin afforded DA-~y-CD-DO3MA-Gd (1.68 g).
Élementary analysis: C 38.0 wt%; H 7.3 wt%; N 9.8 wt%
Gd content: 15.5 wt%, Gd binding number: 6.2 ExamPle 5 Synthesis of DA-!3-CD-DO3MA-Bi !3-Cyclodextrin (0.20 g; 0.18 mmol) was dissolved in water ( 2 ml ) to stir at room temperature . Under the . 21~00~2 shielded light, 0.2N sodium metaperiodate (8 ml) was added thereto in portions to stir for 24 hours. Then, Do3MA-Bi (1.04 g; 1.5 mmoI) was added thereto, followed by addition of triethylamine (0.04 ml). After stirred for 24 hours, sodium borohydride (0.6 g) was added thereto to stir for 24 hours . The reaction solution was ad justed to pH 2 with hydrochloric acid, an aqueous sodium hydroxide solution was added to adjust the solution to neutral, and the white precipitates were removed by concentration, followed by dialysis (fraction molecular weight: 1000) to obtain DA-~3-CD-DO3MA-Bi (0.48 g) .
Bi content: 17.7 wt~, Coupled number of Bi: 4.3 Example 6 Relaxivity (in vitro) of DA-~-CD-DO3MA-Gd and DA-y-CD-DO3MA-Gd DA-~-CD-DO3MA-Gd or DA-~-CD-DO3MA-Gd was dissolved in distilled water in terms of Gd concentration:
5, 2.5, 1.25 and 0.625 mM, respectively. Relaxation time of each compound at 37C (Tl and T2; msec) was determined using NMR (0.5T and 1.5T). Tl relaxivity and T2 relaxivity (Rl and R2, (mM-S)~I, respectively) were calculated from relaxation time values. The results are shown in Table 2.
The values are per one Gd molecule. DA-~-CD-D03MA-Gd and DA-~y-CD-DO3MA-Gd have good relaxation effect in vitro, which is predominantly higher than that of DTPA-Gd ( also shown in Table 2 ), of a mono-chelate complex, measured 60~2 according to the same method . Thus, the ef ficacy of the compound in the present invention was confirmed.
Table 2 Relaxivity (in vitro) of DA-~-CD-DO3MA-Gd and DA-y-CD-DO3MA-Gd Compound Rl (mM-S ) R2 (mM-S ) lODA-~-CD-DO3MA-Gd 8 . 6 10 . 8 DA-y-CD-DO3MA-Gd 8 . 4 10 . 8 15DTPA-Gd 3 . 7 4 . 5 Example 7 Preparation of a 0 . 5 M solution of DA-o;-CD-DO3MA-Gd or DA-y-CD-DO3MA-Gd DA-c~-CD-DO3MA-Gd (1.0 g) was weighed and water for in~ection was added thereto at an appropriate amount to obtain a 0.5M (Gd concentration) solution of DA-~-CD-DO3MA-Gd .
DA-y-CD-DO3MA-Gd ( 1. 0 g ) was weighed and water for in~ection was added thereto at an appropriate amount to obtain a 0.5M (Gd concentration) solution of DA-y-CD-DO3MA-Gd. Both compounds could be prepared into a solution having the higher neccesary concentration without the u~e of a solubilizer.
ExamPle 8 Imaging effect (in vivo) in a cancer-carrying rat after intravenous administration of DA-~-CD-DO3MA-Gd or DA-y -CD-DO3MA-Gd 21600~2 . ~
_ 20 --A solution of DA-a-CD-DO3MA-Gd or DA-~-CD-DO3MA-Gd was administered to male WKA rats ( 284-287 g, transplanted with rat hepatic cells cancer kDE~-8 ) anesthetized with ravonal, via a cannula fixed to tail vein (0.2 mmol (Gd)/kg). The rats were fixed prone in the magnetic field of a MRI apparatus and each cancer-carrying region was imaged.
The apparatus (Omega CSI manufactured by Bruker) had a magnetic field intensity of 2 . 0T and, as an imaging coil, a rat Body coil was used. Imaging was carried out according to spin echo method of rl weighed (I~R/TE: 600/12 msec) under the condition of 2 mm in slice thickness, a resolution of 256 x 128.
The results are shown in Figures 1 and 2.
Claims (8)
1. A diagnostic imaging agent which comprises a compound of (a) a complexing agent having at least one ligand chemically coupled to an aldehyde group of a dialdehyde-cyclodextrin wherein at least one constituent monosaccharide cyclodextrin is oxidation-cleaved, coordinated with (b) at least one metal ion selected from the group consisting of metal ions having the atomic number of 21-29, 31, 32, 37-39, 42-44, 49 and 56-83.
2. A diagnostic imaging agent according to claim 1, wherein at least one ligand is an diethylenetriaminepentaacetic acid derivative.
3. A diagnostic imaging agent according to claim l, wherein at least one ligand is an 1,4,7,10-tetraazacyclododecane-l,4,7,11-tetraacetic acid derivative.
4. A diagnostic imaging agent according to claim 1, wherein at least one ligand is an 1,4,8,11-tetraazacyclotetradecane-l,4,8,11-tetraacetic acid derivative.
5. A diagnostic imaging agent according to claim 2, wherein the diethylenetriaminepentaacetic acid derivative is 1-(p-aminobenzyl)diethylenetriaminepentaacetic acid.
6. A diagnostic imaging agent according to claim 3, wherein the 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid derivative is 1, 4, 7 ,10-tetraazacyclododecane-l-aminoethylcarbamoylmethyl-4, 7 ,10-tris [ ( R, S ) -methylacetic acid ] .
7. A diagnostic imaging agent according to any one of claims 1, 2, 3, 4, 5 or 6, wherein the metal ion is Gd, Dy, Tb, Ho, Er or l?e ion.
8. A diagnostic imaging agent according to any one of claims 1, 2, 3, 4, 5 or 6, wherein the metal ion is Bi, Pb, Tb or Os ion.
'~. A diagnostic imaging agent according to any one of claims 1, 2, 3, 4, 5 or 6, wherein the metal ion is Co, Cu, Ga, Ge, Sr, Y, Tc, In, Sm, Gd, Yb, Re or Ir ion.
.
'~. A diagnostic imaging agent according to any one of claims 1, 2, 3, 4, 5 or 6, wherein the metal ion is Co, Cu, Ga, Ge, Sr, Y, Tc, In, Sm, Gd, Yb, Re or Ir ion.
.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002160052A CA2160052A1 (en) | 1995-10-06 | 1995-10-06 | Diagnostic imaging agent |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002160052A CA2160052A1 (en) | 1995-10-06 | 1995-10-06 | Diagnostic imaging agent |
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| Publication Number | Publication Date |
|---|---|
| CA2160052A1 true CA2160052A1 (en) | 1997-04-07 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002160052A Abandoned CA2160052A1 (en) | 1995-10-06 | 1995-10-06 | Diagnostic imaging agent |
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| Country | Link |
|---|---|
| CA (1) | CA2160052A1 (en) |
-
1995
- 1995-10-06 CA CA002160052A patent/CA2160052A1/en not_active Abandoned
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| Date | Code | Title | Description |
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| FZDE | Discontinued |
Effective date: 20011009 |