JPS63170399A - Radioactive medicine and high polymer compound for preparation thereof - Google Patents

Abstract

NEW MATERIAL:A high polymer compound obtained by chemically linking a reactive high polymer having a bifunctional ligand with an asialoglycoprotein receptor-oriented compound. EXAMPLE:Galactose-linked serum albumin-amylose-deferroxamine. USE:A carrier of radioactive metal element. Useful in extirpation of an internal organ such as liver or the like containing an asialoglycoprotein receptor, detection of deseases, etc., capable of readily and strongly forming chelate linkage and obtaining a radioactive medicine having relatively high concentration per unit. PREPARATION:For example, a reactive high polymer compound (e.g. amylose, etc.) having plural numbers of reactive groups is chemically linked with a bifunctional ligand (e.g. deferroxamine, etc.). Then the resultant reactive high polymer having the bifunctional ligand is linked with the asialoglycoprotein receptor-oriented compound (e.g. galactose linked serum albumin, etc.).

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a radiopharmaceutical and a polymer compound for its preparation.

(Prior Art) The asialoglycoprotein receptor is a type of protein called animal lectin that has molecular recognition ability, and is widely found in animal cells, especially hepatocytes.

The asialoglycoprotein receptor isolated from human hepatocytes is composed of a single polypeptide with a molecular weight of approximately 40,000, and is a glycoprotein with a galactose residue at the non-reducing end of the sugar chain (
It is a receptor that recognizes asialoglycoprotein).

Although much remains unknown about the physiological functions of asialoglycoprotein receptors, the receptors present on the surface of hepatocytes bind to glycoproteins in the hepatic bloodstream to form complexes that are taken up into cells. After that, it is transported within the cell and dissociated in lysosomes, so it is believed that it plays a role in the metabolic process of glycoproteins. Therefore, in liver diseases such as chronic hepatitis, cirrhosis, and primary liver cancer, a phenomenon in which the blood concentration of asialoglycoprotein increases is observed, and in experimental liver damage models created by drug administration, the asialoglycoprotein receptor in the liver is It is acknowledged that body mass decreases.

This means that it is possible to diagnose liver disease by evaluating the quantity and quality of asialoglycoprotein receptors in the liver using asialoglycoprotein-like substances, that is, compounds that are directed toward analloglycoprotein receptors. means.

(Problems to be solved by the invention) Nuclear medicine techniques using radioactive isotopes are suitable for the above-mentioned diagnostic methods, but the nuclides conventionally used for experimental labeling are radioactive iodine elements. l is an isotope
-131 and l-125, as well as technetium (Tc-99m), a radioactive metal element. however,
l-131 and l-125 have long physical half-lives (8
(days and 60 days) and undergo enzymatic deiodination reactions in vivo, exposing tissues other than the target organs to radioactive radiation and causing errors in dynamic tests and quantitative evaluations.
It cannot be said to be an appropriate nuclide.

On the other hand, when using technetium-99m, it is effective only for asialoglycoprotein receptor-directed compounds that have a binding site and have a ligand capable of forming a chelate bond with technetium in the molecule. For example, galactose-bound serum albumin (hereinafter abbreviated as NGA (neogalactalbumin)) can bind to technetium via instein, lysine, glutamic acid residues, etc. in the molecule. However, the stability constant of such a state is generally low, and the in vitro and in vitro stability (labeling rate) of the labeled substance is said to be low. Colloidal technetium dioxide (mT c○,) is an impurity generated as a result of destabilization, and this compound is taken up into the reticuloendothelial system of the liver, so when it coexists, the asialoglycoprotein receptor changes. Furthermore, when labeling with technetium, pertechnetate ion (mTco4), which is a stable chemical form, must be reduced and labeled; Tin salt is used. Since stannous salt forms a colloid in a pH range above weak acidity where technetium labeling is possible, by adding a sufficient amount of NGA and binding the stannous salt to it,
It is necessary to suppress the presence of free stannous salts. For this reason, when NGA is directly labeled with technetium-99m, it is difficult to produce a radiopharmaceutical.

(Means for solving the problem) As a result of various studies, the present inventors have developed a polymer in which a reactive polymer having a bifunctional ligand is bonded to an asialoglycoprotein receptor-directed compound. It has been found that the compound is useful as a carrier for a radioactive metal element, and that a radioactive metal element-bound polymer compound in which a radioactive metal element is bound to such a carrier is useful as a radiopharmaceutical that overcomes the above-mentioned drawbacks.

Radioactive metal element-bonded polymer compounds have multiple bifunctional ligands that can form strong chelate bonds with radioactive metal elements, and are stable both in vitro and in vivo. Therefore, it is possible to provide highly enhanced radiopharmaceuticals.

The gist of the present invention is: a polymer compound (A) formed by chemically bonding a reactive polymer (1) having a bifunctional ligand and an asialoglycoprotein receptor-directed compound (2); A radioactive metal element-bound polymer compound (, A) formed by chelating a radioactive metal element (3) to
B), a composition for preparing a radiopharmaceutical (C) containing the polymer compound (A), and a radiopharmaceutical (D) containing the radioactive metal element-bonded polymer compound (B).

The above-mentioned polymer compound (A) and radioactive metal element-bound polymer compound (B) are new substances that have not been described in any literature, and they can visualize organs containing asialoglycoprotein receptors and change the quantity and quality of asialoglycoprotein receptors. The present invention can provide a radiopharmaceutical suitable for nuclear medicine applications such as detection of diseases causing asialoglycoprotein receptors and dynamic examination of asialoglycoprotein receptors.

(Function) The reactive polymer (1) having a bifunctional ligand has a bifunctional ligand that forms a strong chelate bond with the radioactive metal element (3), and Anoaloglycoprotein receptor-directed compound (2) under relatively mild conditions
) are used which have a reactive group capable of forming a chemical bond with. The reactive polymer (1) having such a bifunctional ligand is difunctionalized to the polymer compound (1a) having a plurality of reactive groups so that at least one of the reactive groups remains. It can be obtained by chemically bonding the functional ligand compound (1b).

Examples of the polymer compound (la) having a plurality of reactive groups include pentosan, hexosane, polyglycosamine,
Polysaccharide derivatives such as polyuronic acids, glycosaminoglycans, heterohexosamines, more specifically amylose, amylopectin,
Dextran, cellulose, inulin, pectic acid, pullulan derivatives, etc. may be used. In addition, polyacrolein derivatives, polysaccharide derivatives, polyamine derivatives (especially polylysine polyimine derivatives), etc. can be used similarly. Note that these may be used alone, or may be a mixture or a dehydrated condensate.

Specific examples of the bifunctional locator compound (lb) include the following compounds. That is, diethylenetriaminepentaacetic acid cyclic acid anhydride represented by the formula %, ethylenediaminetetraacetic acid succinimide ester represented by the formula %, formula % (wherein R4 and R7 are hydrogen, CI''- 3-aminomethylene-2,4-pentanedione-bis(thiosemicarbazone) derivative, represented by the formula % (wherein R1 and R7 are hydrogen or C, respectively) -C3
Alkyl and n represent an integer of 0 to 3. ) 1−
(p-aminoalkyl)phenylpropane-1゜2-dione-bis(thiosemicarbazone) derivative, deferoxamine, formula % (wherein R, -Rs represent hydrogen or C+ -C3 alkyl) Examples include the 2-propionaldehyde-bis(thiosemicarbazone) derivatives shown below. In addition, even if it itself does not have a functional group capable of bonding with the polymer compound (la) having multiple reactive groups, it can easily bind to functional groups such as amino groups, carboxyl groups, aldehyde groups, and thiol groups. If the compound has a group or structure capable of introducing a group, it can be used as a bifunctional ligand compound (Ib) as long as it has the property of capturing a metal element with a radical of q=. For example, dimercaptoacedelethylenediamine (Pritzberg et al.: J, N
Nucl, Med, 23.917 (1982)) and bisaminoethanethiol (Fritz-berg et al.: J. Nucl, Med, 25.916 (1982)).
Ne5t ligands represented by Cyclan (84)),
Keiri*g et al.: J. Nucl. Med, 23
．． 917 (1982)), N4 ligands represented by
, N'-bis(2-hydroquinethyl)ethylenenoamine (Wagner Jr. et al.: Proceed-i
ngs of the international
Symposium on Technetium i
n Chemistry and Nucl, ear
Medi-cine, Padova, Ita
ly, p. 161 (19g2))
Examples include ligands.

In order to produce the polymer compound (A), the reactive polymer (1) having a bifunctional ligand and the analloglycoprotein receptor-directed compound (2) are directly reacted by a conventional method. They may be bound together or bound through a suitable crosslinking agent, and purified by conventional means such as dialysis, salting out, gel filtration, ion exchange chromatography, and electrophoresis. Asialoglycoprotein receptor-directed compound (2) 1
The number of molecules of the reactive polymer (1) having a bifunctional ligand to be bound per molecule is not limited as long as the asialoglycoprotein receptor-directed compound (2) does not lose its physiological activity, but usually , 10 molecules or less are desirable.

Asialoglycoprotein receptor-directed compound (2) referred to here
means a compound that has binding affinity for an asialoglycoprotein receptor in vivo, and specific examples include asialoglycoproteins (such as NGA, asialoorosomucoid, asialofetuin, asialocelluloblasmin, asialohaptoglobin). ), galactose-bound polylysine, galactose-bound polycrocosamine, and the like.

The polymer compound (A) is useful as a carrier for preparing radiopharmaceuticals. That is, the polymer compound (A)
A reactive polymer (1) having a bifunctional ligand that forms a strong chelate bond with a radioactive metal element (3) is introduced into the reactive polymer (1). Since the difunctional ligand is present, it is possible to capture a plurality of radioactive metal elements (3), thereby making it possible to obtain a stable radiopharmaceutical with extremely high specific radioactivity. Also, conventionally,
Compounds directed to asialoglycoprotein receptors, which could not be labeled with radioactive metal elements, can now be stably labeled.

Although the polymer compound (A) used as a carrier for radiopharmaceutical preparation may be stored in the form of a solution, it is usually converted into a powder state by freeze-drying, low-temperature vacuum distillation, etc., and then stored. It is dissolved in sterile water, physiological saline, buffer solution, etc. Polymer compounds in powder form or after dissolution (
A) may include a pharmaceutically acceptable solubilizing agent (
(e.g. organic solvents), pt-tg moderators (e.g. acids, bases,
buffers), stabilizers (e.g. ascorbic acid), preservatives (
For example, a reducing agent or an oxidizing agent for adjusting the valence state of the radioactive metal element (3) may be added.

The above-mentioned radioactive metal element (3) is a metal element that has radioactivity, has physical properties and chemical properties suitable for nuclear medicine techniques, and is 2 in the polymer compound (A).
Those that can be easily captured by functionalized ligand structures are used. Specific examples include gallium-67, gallium-68, thallium-2011 indium-1111 technetium-99m, zinc-62, copper-62, and the like.

These are usually used in the form of salts, particularly water-soluble salts, and are labeled by contacting them with the polymer compound (A) in an aqueous medium. However, if the radioactive metal element (3) is in a valence state that allows it to form a stable chelate complex (e.g. gallium-67, indium-111), there is no need for other reagents to be present in the reaction system; When it is necessary to change the valence state to form a stable chelate complex (eg, technetium-99m), a reducing or oxidizing agent must be present in the reaction system.

Examples of reducing agents include divalent stannous salts (eg, tin halides, tin sulfate, tin nitrate, tin acetate, tin citrate). Specific examples of oxidizing agents include hydrogen peroxide.

For example, technetium-99 as a radioactive metal element (3)
When using technetium-99m, the polymeric compound (A) is treated with technetium-99m in the form of pertechnetate ion in the presence of stannous as a reducing agent in an aqueous medium. Be able to adjust (B). In the above preparation, there are no particular restrictions on the order in which the reagents are mixed, but it is generally preferable to avoid mixing the stannous salt and pertechnedate ion in the aqueous medium first.

In order for the thus obtained radioactive metal element-bonded polymer compound (B) to be useful as a radiopharmaceutical, it must have sufficient radioactivity and radioactivity concentration for nuclear medicine applications. For example, when technetium-99m is used as the radioactive metal element (3), 0.0.
It is desirable to have a radioactivity concentration of 0.1-50xCi per 5-5, OmQ. Further, although such a radioactive metal element-bonded polymer compound (B) may be administered immediately after preparation, it is desirable that it has sufficient stability to withstand storage for an appropriate period of time after preparation. Furthermore,
The radioactive metal element-bonded polymer compound (B) may contain pH moderators (e.g. acids, alkalis, buffers), stabilizers (e.g. ascorbic acid), isotropic agents (e.g. sodium chloride), etc. as necessary. It's okay.

(Example) EXAMPLES The present invention will be explained in more detail with reference to Examples below.

Example 1 Production of a composition containing NGA-Amylose (DFO) conjugate Deferoxamine (hereinafter abbreviated as DFO) was placed at 15 sites at 0.
03M phosphate buffer (pI (7,0) dissolved in 1 mQ,
Add 3.2 μQ of triethylamine to this and
Stir for a minute. To this, add 1 mQ of dialdehyde amylose (25rxfl/ml) dissolved in water,
Stirred at room temperature for 30 minutes. This solution will be referred to as Solution A.

Separately, cyanomethyl-thiogalactose 19 was placed in a nano-type flask, 25 u of dry methanol (!) was added, and the mixture was heated to 50°C.
Dissolve with. Sodium methoxide 27g was added to this, and after reacting at room temperature for 48 hours, methanol was evaporated under reduced pressure. Next, 0.2M containing 1g of human serum albumin
Add borate buffer 2011Q and react overnight at 4°C to obtain NGA/8 solution. This solution will be referred to as Solution B. Add 2 rtt (l) of solution A to solution B 2, stir at room temperature for about 6 hours to react, add sodium hydroxide borate t, sm9, and reduce while stirring at room temperature for about 1 hour.Reaction liquid is 1M
Dialysis was performed against a sodium chloride solution, followed by column chromatography using Sephacryl S-200 (column diameter 2.2 cm, length 50 cm) using 0.03 M phosphate buffer (pH 7.0) as an eluent. NGA-A
Purify mylose (DFO).

All of the above-mentioned operations were performed aseptically, and all the instruments used were either pyrogen-burned by heat treatment at 180° C. for 4 hours, or washed with distilled water for injection and then sterilized in an autoclave. The buffer solution was prepared using distilled water for injection and sterilized by filtration sterilization using a membrane filter. The column was washed with sodium hypochlorite solution and then equilibrated with O, 1M sodium chloride solution.

The purified NGA-Amylose (DFO) obtained here is
The mixture was diluted with 0.03M phosphate buffer to give a concentration of 1 g/1ttQ, and 1 mQ each was dispensed into sterile vials while being filtered through a membrane filter to obtain the desired composition.

DFO and Amylosegl of the above conjugate were analyzed by electrophoresis. That is, gallium citrate (87Ga) injection solution 1 was added to a part of the reaction solution after the completion of the reduction reaction.
iCi was added and labeled, and this was used as a sample.

NGA-Amylo analyzed by electrophoresis
se(DFO)-”Ga, Amylose(DF
From the values of O)-''Ga and D P 0-67Ga, the number of DFO molecules per NGAI molecule in the conjugate obtained in this example was calculated to be 11.5 g, and the number of Amylose molecules to be 0.07.

Example 2 Preparation and properties of NGA-Amylose (DFO)-Ga injection 2mC1 of gallium citrate (e?Ga) injection was added to a vial containing the composition obtained in Example 1, and NG
A-Amylose(DFO)-"Ga injection solution was obtained. The above operations were performed aseptically. The labeling rate of the labeled substance obtained here was calculated by electrophoresis.
No radioactivity peaks other than those of the labeled substance were observed, indicating that it was a highly pure radiopharmaceutical.

(Effects of the Invention) In the present invention, an asialoglycoprotein receptor-directed compound is catalyzed by a polymer compound having a plurality of reactive groups.
Functional ligands have been introduced.

In other words, each molecule of an asialoglycoprotein receptor-directed compound contains a large number of bifunctional ligands that can easily and firmly form a chelate bond with a radioactive metal element. When contacted with a radiopharmaceutical, a radiopharmaceutical with a relatively high concentration of radioactivity per unit amount is obtained. Therefore, it is possible to make a reliable diagnosis with a relatively small dose.

Claims (1)

[Scope of Claims] A polymer compound (A) formed by chemically bonding a reactive polymer (1) having a mono- or difunctional ligand and an asialoglycoprotein receptor-directed compound (2). 2. Chelate a radioactive metal element (3) to a polymer compound (A) formed by chemically bonding a reactive polymer (1) having a bifunctional ligand and an asialoglycoprotein receptor-directed compound (2). A radioactive metal element-bonded polymer compound (B). 3. A composition for preparing a radiopharmaceutical containing a polymer compound (A) formed by chemically bonding a reactive polymer (1) having a difunctional ligand and an asialoglycoprotein receptor-directed compound (2) ( C). 4. Chelate a radioactive metal element (3) to a polymer compound (A) formed by chemically bonding a reactive polymer (1) having a difunctional ligand and an asialoglycoprotein receptor-directed compound (2) A radiopharmaceutical (D) containing a radioactive metal element-bound polymer compound (B).