Patent Description:
Recently, attention has been drawn to a boron neutron capture therapy (BNCT) as a cancer treatment method utilizing a radioisotope. The boron neutron capture therapy is a treatment method in which a boron compound containing boron-<NUM> isotope (<NUM>B) is delivered to cancer cells and the cancer cells are irradiated with a low energy neutron (for example, epithermal neutrons), and thus the cancer cells are locally destroyed by a nuclear reaction which arises in the cells. In this treatment method, since it is important to cause a boron compound which contains boron <NUM> to be selectively accumulated by cells of cancerous tissue so as to enhance therapeutic effect, it is necessary to develop boron compounds which are selectively and certainly taken by cancer cells.

Boron-containing compounds in which boron atoms or boron atomic groups are introduced into a basic structure have been synthesized as an agent used in BNCT. Examples of an agent used in the actual clinical practice include p-boronophenylalanine (BPA) and mercaptoundecahydrododecaborate (BSH).

p-Boronophenylalanine has very poor solubility at physiological pH.

In order to improve solubility of p-boronophenylalanine in water, a method of producing a fructose complex of p-boronophenylalanine (for example, Patent Document <NUM>), and a method of adding a monosaccharide or a polyol to p-boronophenylalanine in an alkaline solution (such as an aqueous sodium hydroxide solution) and removing an inorganic salt with an ion exchange resin for use (for example, Patent Document <NUM>) have been attempted.

Furthermore, another technique for improving solubility of p-boronophenylalanine has been proposed (Patent Document <NUM>).

However, blood boron concentration at the time of administration required for exerting an effect as boron neutron capture therapy is limited. Therefore, it is necessary to adjust the blood boron concentration within a certain range and to strictly determine administration rate. On the other hand, it is desired to establish a well-balanced prescription that does not cause adverse events during administration while maximizing an effect on a subject.

Therefore, an object of the present invention is to provide an injection solution containing p-boronophenylalanine, which has excellent stability, also assures safety as an intravenous drip infusion, and has a small burden on a subject to be administered.

The present inventors have intensively studied to solve the above problems and, as a result, have found that a preparation with excellent effect on a subject can be prepared while enhancing solubility of p-boronophenylalanine in an injection solution, stability in a wide temperature range, and safety, by controlling a ratio of boron <NUM> of boron atoms in a compound, further, containing a sugar alcohol and an antioxidant, and adjusting pH value and osmotic pressure ratio, and thus the present invention has been completed.

That is, the present invention provides the following injection solutions.

The injection solution of the present invention has excellent stability, also assures safety as an intravenous drip infusion, and has good properties also for administration to humans and animals.

<FIG> is a graph showing a relationship between a time (horizontal axis (hr)) when a composition of Example was dripped to a subject and a blood concentration of <NUM>B (µg/ml).

The unit "mass%" herein is synonymous with "g/<NUM>". "W/v%" is synonymous with "g/<NUM>".

The injection solution of the present invention is an injection solution for boron neutron capture therapy (BNCT), containing p-boronophenylalanine or a pharmaceutically acceptable salt thereof, with a ratio of boron <NUM> of boron atoms in a compound of <NUM> % or more; sorbitol; antioxidant selected from the group consisting an of sodium pyrosulfite, sodium sulfite, and sodium bisulfite; and water, and having a pH of <NUM> to <NUM> and an osmotic pressure ratio of <NUM> to <NUM>, which is to be administered by intravenous drip.

The p-boronophenylalanine used in the present invention has a ratio of boron <NUM> of boron atoms in a compound of <NUM> % or more, preferably <NUM> % or more, more preferably <NUM> % or more, even more preferably <NUM> % or more, and particularly preferably <NUM> % or more.

In natural boron (boron), boron <NUM> and boron <NUM> are isotopes, and boron <NUM> is present in a ratio of <NUM>% and boron <NUM> in a ratio of <NUM>%. Therefore, prior to production of the injection solution containing p-boronophenylalanine of the present invention, boron having a mass number of <NUM> (boron <NUM>) is concentrated. For this purpose, boron <NUM> and boron <NUM> in a natural boron compound are sorted out, and highly concentrated boron <NUM> is produced. As the boron used in the present invention, boron <NUM> may be concentrated to increase the concentration of boron <NUM>, or a commercially available product may be used. As the commercially available product, for example, <NUM>B concentrated boric acid (manufactured by Stella Chemifa Corporation) can be used as a starting material.

Here, as a method for measuring boron <NUM>, it can be performed using Agilent <NUM> (manufactured by Agilent), by a quadrupole ICP-MS (ICP-QMS) method using a quadrupole mass spectrometer part. ICP-QMS used for measurement is adjusted according to JIS K0133.

L-form is currently used as p-boronophenylalanine, and L-p-boronophenylalanine can be also preferably used in the present invention, but the present invention is not limited thereto. That is, racemic p-boronophenylalanine containing D-form or both D-form and L-form can be used in the present invention.

Here, p-boronophenylalanine is, for example, synthesized by a known method, after obtaining boron with an increased ratio of boron <NUM> or after obtaining boric acid with an increased ratio of boron <NUM> (for example, <NPL>: <NPL>: <CIT>: <CIT>: and <CIT>), and can be used.

Here, the salt is not particularly limited as long as it is pharmacologically acceptable. Examples of the p-boronophenylalanine salt include salts with an organic acid, salts with an inorganic acid, salts with an organic base, and salts with an inorganic base.

Examples of the salts with an organic acid include acetates, trifluoroacetates, fumarates, maleates, lactates, tartrates, citrates, and methanesulfonates. Examples of the salts with an inorganic acid include hydrochlorides, sulfates, nitrates, hydrobromides, and phosphates. Examples of the salts with an organic base include salts with triethanolamine. Examples of the salts with an inorganic base include ammonium salts, sodium salts, potassium salts, calcium salts, and magnesium salts.

In the injection solution of the present invention, a content of p-boronophenylalanine or a salt thereof based on a total amount of the injection solution is appropriately set depending on a balance with other components. The total content of p-boronophenylalanine and/or a salt thereof based on the total amount of the injection solution is not particularly limited, but is preferably <NUM> to <NUM> w/v%, more preferably <NUM> to <NUM> w/v%, and further preferably <NUM> to <NUM> w/v%.

When the content of p-boronophenylalanine in the injection solution of the present invention is within the above ranges, the amount of the injection solution falls within an appropriate liquid amount during clinical application, solution stability is good, and an effect during administration is excellent.

A sugar alcohol used in the present invention is sorbitol.

As sorbitol, D-sorbitol, which is currently approved for use in medicines and whose safety has been confirmed, can be preferably used, but is not limited thereto. That is, in the present invention, L-form or a mixture of L-form and D-form can be also used.

As mannitol (not claimed), D-mannitol, which is currently approved for use in medicines and whose safety has been confirmed, can be preferably used, but is not limited thereto. That is, in the present invention, L-form or a mixture of L-form and D-form can be also used.

The total content of the sugar alcohol used in the injection solution of the present invention depends on blending amounts of other additives, but is preferably <NUM> to <NUM> w/v%, more preferably <NUM> to <NUM> w/v%, and further preferably <NUM> to <NUM> w/v%, based on the total amount of the injection solution.

An amount of sugar alcohol is preferably in a range of <NUM> to <NUM>, more preferably <NUM> to <NUM>, and further preferably <NUM> to <NUM>, in molar ratio, with respect to an amount of p-boronophenylalanine. When the amount of sugar alcohol is within these ranges, precipitation of p-boronophenylalanine can be suppressed and an osmotic pressure ratio can be adjusted appropriately.

An antioxidant used in the present invention is selected from the group consisting of sodium pyrosulfite, sodium sulfite, and sodium bisulfite.

Here, examples of the salts of sulfurous acid, bisulfite, pyrosulfurous acid, nitrous acid, ascorbic acid, L-cysteine or thioglycolic acid include alkali metal salts such as sodium salts and potassium salts; alkaline earth metal salts such as calcium salts and magnesium salts; and inorganic salts such as aluminum salts and ammonium salts. Furthermore, for example, a salt with an organic base such as trimethylamine, triethylamine, pyridine, picoline, ethanolamine, diethanolamine, triethanolamine,.

dicyclohexylamine or N,N'-dibenzylethylenediamine can also be used. Particularly preferred are the sodium salts, potassium salts, or ammonium salts. Claimed is an antioxidant selected from the group consisting of sodium pyrosulfite, sodium sulfite, and sodium bisulfite.

Particularly preferred as the antioxidant is one or more selected from a group consisting of sodium sulfite, dried sodium sulfite, potassium sulfite, calcium sulfite, sodium bisulfite, potassium bisulfite, ammonium bisulfite, sodium pyrosulfite, and potassium pyrosulfite. Claimed is an antioxidant selected from the group consisting of sodium pyrosulfite, sodium sulfite, and sodium bisulfite.

The total content of the antioxidant used in the injection solution of the present invention depends on the blending amounts of other additives, but is preferably <NUM> to <NUM> w/v%, more preferably <NUM> to <NUM> w/v%, further preferably <NUM> to <NUM> w/v%, even more preferably <NUM> to <NUM> w/v%, and most preferably <NUM> to <NUM> w/v%, based on the total amount of the injection solution.

The injection solution of the present invention further contains water. A water used in the present invention is not particularly limited as long as it is used as a component of an injection in the pharmaceutical field.

A content of water used in the injection solution of the present invention depends on the blending amounts of other additives, but is preferably <NUM> w/v% or more and more preferably <NUM> w/v% or more, and preferably <NUM> w/v% or less and further preferably <NUM> w/v% or less, based on the total amount of the injection solution.

The pH of the injection solution of the present invention is preferably a pH around neutral to weakly alkaline, in consideration of a balance between in vivo administration and stability. More specifically, the pH is in a range of <NUM> to <NUM> and more preferably <NUM> to <NUM>, and particularly from the viewpoint of long-term stability in a low temperature region, preferably in a range of pH exceeding <NUM> and <NUM> or less, and particularly preferably in a vicinity of pH exceeding <NUM> and <NUM> or less. A suitable pH adjusting agent, buffer and the like used in the art may be used to adjust the pH as needed.

An osmotic pressure ratio of the injection solution of the present invention is not particularly limited, but it is preferably within a range of <NUM> to <NUM> in comparison with physiological saline. More preferably, the osmotic pressure ratio is in a range of <NUM> to <NUM>. Within these ranges, it becomes possible to reduce pain, avoid an onset of phlebitis, and shorten administration time in a case of a large amount of intravenous injection.

The injection solution of the present invention may appropriately contain various metal ions that may be contained in vivo, in order to ensure stability in vivo and in vitro. Preferably, sodium ion is contained, and the concentration thereof is not particularly limited, but is particularly preferably from <NUM> mEq/L to <NUM> mEq/L. This numerical range which is close to a Na ion concentration range of a body fluid is preferable so that an electrolyte balance between an intracellular fluid and an extracellular fluid is not significantly disturbed.

The injection solution of the present invention can be appropriately added with a pH adjusting agent such as an inorganic acid such as hydrochloric acid or phosphoric acid or an alkaline component such as sodium hydroxide or potassium hydroxide as needed. Furthermore, it is also preferable to use an organic acid in addition to or in place of the inorganic acid. As the organic acid, citric acid, acetic acid, trifluoroacetic acid, fumaric acid, maleic acid, lactic acid, tartaric acid or methanesulfonic acid is preferably used, and citric acid or lactic acid is further preferably used.

The injection solution of the present invention may be added with a buffer such as a phosphate buffer solution, a tris-hydrochloric acid buffer solution, an acetate buffer solution, a carbonate buffer solution or a citrate buffer solution as needed. These buffers may be useful in stabilizing a preparation and reducing irritation.

Further, the composition of the present invention can contain other components usually used in the technical field of the present invention as needed, unless contrary to the object of the present invention. Examples of such a component include additives usually used in a liquid, particularly an aqueous composition, for example, preservatives such as benzalkonium chloride, potassium sorbate and chlorohexidine hydrochloride, stabilizer such as edetic acid Na, thickening agents such as hydroxyethylcellulose and hydroxypropylmethylcellulose, isotonizing agents such as sodium chloride, potassium chloride, glycerin, sucrose and glucose, surfactants such as polysorbate <NUM> and polyoxyethylene hydrogenated castor oil, isotonic agents such as sodium chloride, potassium chloride and glycerin, and pH adjusting agents such as sodium hydroxide.

When the injection solution of the present invention is used as a medicine, it may be in a form of an injection for intravenous injection using a solution. In particular, it may be an intravenous drip injection solution.

The injection solution is produced by dissolving, suspending or emulsifying a certain amount of an active ingredient in an aqueous solvent (for example, distilled water for injection, physiological saline, Ringer's solution, etc.), an oily solvent (for example, vegetable oil such as olive oil, sesame oil, cottonseed oil or corn oil, propylene glycol, etc.) or the like, together with a dispersant (for example, polysorbate <NUM>, polyoxyethylene hydrogenated castor oil <NUM>, polyethylene glycol, carboxymethyl cellulose, sodium alginate, etc.), a preservative (for example, methylparaben, propylparaben, benzyl alcohol, chlorobutanol, phenol, etc.), an isotonizing agent (for example, sodium chloride, glycerin, D-mannitol, glucose, etc.) or the like. At this time, additives such as a solubilizing agent (for example, sodium salicylate, sodium acetate, etc.), a stabilizer (for example, human serum albumin, etc.) and a soothing agent (for example, benzyl alcohol, etc.) may be used as desired. Further, an antioxidant, a colorant or the like and other additives may be added as needed.

In addition, a "pharmaceutically acceptable carrier" can also be used. Examples of such substances include solvents, solubilizing agents, suspending agents, isotonizing agents, surfactants, soothing agents and the like in liquid preparations. In addition, preparation additives such as preservatives (antiseptics) and colorants can be used according to a conventional method.

Preferable examples of the "solvent" include alcohols, propylene glycol, macrogol, and the like.

Examples of the solubilizing agent include polyethylene glycol, propylene glycol, benzyl benzoate, trisaminomethane, cholesterol, triethanolamine, sodium carbonate, sodium citrate, and the like.

Preferable examples of the "suspending agent" include hydrophilic polymers such as polyvinyl alcohol, polyvinylpyrrolidone, sodium carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, hydroxyethylcellulose and hydroxypropylcellulose, and the like.

Preferable examples of the "isotonizing agent" include glucose, sodium chloride, glycerin, and the like.

Examples of the "surfactant" include sodium lauryl sulfate, lauryl aminopropionic acid, lecithin, benzalkonium chloride, benzethonium chloride, glyceryl monostearate, and the like.

Preferable examples of the "soothing agent" include benzyl alcohol and the like.

Preferable examples of the "preservative" include paraoxybenzoic acid esters, chlorobutanol, benzyl alcohol, phenethyl alcohol, dehydroacetic acid, sorbic acid, and the like.

A method for producing the injection solution of the present invention is not particularly limited, but as an example, the injection solution can be prepared by mixing a pH adjusting agent such as sodium hydroxide, water and p-boronophenylalanine, and then adding a sugar alcohol. Here, in preparation, the order may be important for more efficient production. Particularly preferably, a mixed solution of water and a pH adjusting agent of an alkaline component such as sodium hydroxide is first prepared, and then p-boronophenylalanine is added and stirred. Thereafter, a sugar alcohol is added and dissolved so that an injection solution can be prepared. By following such a protocol, each component can be efficiently dissolved in a short time, and an excellent injection solution can be efficiently prepared.

Amounts of water, p-boronophenylalanine, sugar alcohol and pH adjusting agent at this time are in accordance with the amounts described in the injection solution for boron neutron capture therapy.

As a use of the injection solution of the present invention, utilization as an intravenous drip infusion is preferable, and an intravenous drip infusion to be used for boron neutron capture therapy is particularly preferable. Neutron capture therapy is a method of treating by a strong particle beam (alpha ray, 7Li particle) generated by a nuclear reaction between boron <NUM> taken into tumor cells and neutrons, and the injection solution of the present invention can be used in this method with particular advantage.

Prior to irradiation, the injection solution of the present invention can be previously administered to a subject or an animal, adjusted so as to collect boron <NUM> in the tumor, and then irradiated with epithermal neutron rays. Alternatively, prior to irradiation, the injection solution of the present invention can be also previously administered to a subject or an animal, adjusted so as to collect boron <NUM> in the tumor, and then irradiated with epithermal neutron rays while further continuing administration. A dose of the injection solution of the present invention is not particularly limited, but can be controlled to achieve a preferable intracellular boron concentration. Such a dose is set according to a type or progression of a tumor to be applied, age or weight of the subject and the like, but when the injection solution of the present invention is used for intravenous administration, it is administered by an intravenous drip infusion at a rate of <NUM> to <NUM> per hour for <NUM> to <NUM> hours, and preferably for <NUM> to <NUM> hours. It is particularly preferable that the administration start timing be continuously from before the start of neutron irradiation to during the irradiation.

For example, without limitation, it is also effective that, to patients with brain tumors or patients with head and neck cancer, the injection solution of the present invention is adjusted so that a p-boronophenylalanine concentration is preferably <NUM> to <NUM>/kg/hour, and more preferably <NUM>/kg/hour, and administered for preferably <NUM> to <NUM> hours, and more preferably <NUM> hours, then deceleratingly administered so that the p-boronophenylalanine concentration is preferably <NUM> to <NUM>/kg/hour, and more preferably <NUM>/kg/hour, and irradiated with epithermal neutron rays while performing such decelerating administration for a maximum of <NUM> to <NUM> hours, and preferably for a maximum of <NUM> hour. When the injection solution of the present invention is used, preparation before use is not necessary, and it is also possible to perform a series of administration from a start of administration to an end of decelerating administration with one injection solution.

Concerning p-boronophenylalanine by administration, a concentration of boron <NUM> in tumor tissues is <NUM> ppm (<NUM><NUM> boron <NUM> atoms per cell) or more and <NUM> ppm or less, and preferably about <NUM> ppm or more and <NUM> ppm or less. In practice, it is also possible to measure the blood concentration and predict the amount in these tumor tissues or cells.

It is preferable to control so that a nuclear reaction of epithermal neutrons efficiently occurs in the tumor cells, and alpha rays and 7Li particles generated by the nuclear reaction can kill only the tumor cells. A dose is calculated based on a blood boron concentration and a neutron fluence irradiated to the tissue, and the dose is multiplied by relative biological effectiveness (RBE) of p-boronophenylalanine so that an X-ray equivalent dose can be calculated.

For example, without limitation, for patients with brain tumors, a skin dose is set to preferably <NUM> to <NUM> Gy-Eq, and more preferably about <NUM> Gy-Eq, and irradiation can be performed for about <NUM> minutes per time at maximum. Alternatively, without limitation, for patients with head and neck cancer, a mucosal dose is set to preferably <NUM> to <NUM> Gy-Eq, and more preferably about <NUM> Gy-Eq, and irradiation can be about <NUM> minutes per time at maximum.

An antitumor agent of the present invention is highly safe for living bodies and can exhibit a high antitumor effect.

Prior to administration of the injection solution of the present invention, Positron Emission Tomography (PET) can be also used to measure accumulation of p-boronophenylalanine. For example, it is also possible to estimate accumulation of boron compounds by administering, in addition to p-boronophenylalanine, a radioactive compound obtained by labeling p-boronophenylalanine with radionuclide <NUM>F (<NUM>F-fluoro-borono-phenylalanine: FBPA), and imaging whole body distribution of the radioactive compound by PET examination. Without limitation, it is particularly preferable to administer to a subject with a boron concentration ratio of cancer tissue/normal tissue of <NUM> or more and preferably <NUM> or more in such PET examination.

Thus, the injection solution of the present invention is particularly preferably used for neutron capture therapy. A target disease is not limited, but solid cancer is preferable, and cancer originating from epithelial cells (epithelial tumor) can be particularly preferable. Typically, the target disease can be skin cancer including melanoma or the like, lung cancer, breast cancer, stomach cancer, colon cancer, uterine cancer, ovarian cancer, or head and neck cancer (oral cancer, laryngeal cancer, pharyngeal cancer, tongue cancer, etc.). Alternatively, even a sarcoma originating from non-epithelial cells can be targeted. Typically, a target sarcoma can be osteosarcoma, chondrosarcoma, rhabdomyosarcoma, leiomyosarcoma, fibrosarcoma, liposarcoma, and angiosarcoma. In addition to these, brain tumors such as glioma, primary central nervous system malignant lymphoma, meningioma, pituitary adenoma, schwannoma and craniopharyngioma can be target diseases for treatment. Not only initial and single cancer, but also cancer that has spread to individual organs, metastatic cancer, and intractable cancer can be targeted.

The present invention provides the following each embodiment of injection solutions.

Hereinafter, the present invention will be described in more detail with reference to Examples, but these do not limit the scope of the present invention.

Prior to production of an injection solution containing p-boronophenylalanine (BPA; L-form was used here), <NUM>B concentrated boric acid, in which the content of <NUM>B is <NUM> % (manufactured by Stella Chemifa Corporation) obtained by concentrating boron with a mass number of <NUM> (boron <NUM>) was used. Using the highly concentrated boron <NUM> thus obtained, p-boronophenylalanine was produced by a conventional method.

An aqueous solution containing <NUM> w/v% to <NUM> w/v% BPA and D-sorbitol, sodium bisulfite or sodium pyrosulfite was prepared as follows. That is, first, <NUM> to <NUM> of BPA was suspended in a solution prepared by dissolving <NUM> to <NUM> of sodium hydroxide in <NUM> of water. <NUM> to <NUM> of D-sorbitol was added thereto, and the mixture was stirred to dissolve the D-sorbitol. <NUM> of sodium bisulfite or sodium pyrosulfite was added to the mixture and dissolved, and <NUM> (at pH <NUM>) or an appropriate amount of <NUM> mol/l hydrochloric acid was added to adjust pH, and water was added to make a total amount of <NUM>. Then, the resulting solution was filtered with a <NUM> filter. A composition, osmotic pressure ratio, and pH of each aqueous solution are as shown in Tables <NUM> and <NUM>.

Aqueous solutions shown in Table <NUM> were prepared in the same manner as the aqueous BPA sorbitol solution, using mannitol instead of sorbitol. A composition, osmotic pressure ratio, and pH of each aqueous solution are as shown in Table <NUM>.

Aqueous solutions shown in Table <NUM> were prepared in the same manner as the aqueous BPA sorbitol solution, allowing to coexist mannitol in addition to sorbitol. A composition, osmotic pressure ratio, and pH of each aqueous solution are as shown in Table <NUM>.

L-BPA and fructose were added to water to similarly prepare an aqueous L-BPA-fructose solution.

Stability evaluation was carried out mainly using the following models and conditions as standard conditions for medicine severe stability test based on ICH guidelines.

First, as stability test <NUM>, a storage test at <NUM> was performed. In this storage test, the aqueous solutions were placed in storage device: LH21-<NUM> (manufactured by NAGANO SCIENCE CO. ), at <NUM> ± <NUM>, <NUM> ± <NUM>% RH, in a dark place, for <NUM> weeks and <NUM> weeks, each solution was sampled, and BPA concentration, Tyr concentration, Phe concentration, and Ac-BPA concentration (high-performance liquid chromatograph Nexera X2 series, manufactured by Shimadzu Corporation) were measured and compared with those at the start of the test.

Here, measurement conditions by HPLC are as follows.

Compositions of Examples and results of stability evaluation <NUM> are shown in Tables <NUM> and <NUM>. BPA residual amounts in the tables indicate residual amounts of BPA after <NUM> weeks from storage when the amount of BPA used for production in stability test <NUM> was <NUM>%. Although not shown in the tables, an amount of initial tyrosine was evaluated as an index showing a state of initial BPA decomposition due to coexistence of components other than BPA in the composition.

As shown in Table <NUM>, the compositions of all the Examples showed good stability. In cases where the BPA concentration was set to <NUM> w/v%, and the sorbitol concentration was increased to <NUM> w/v% or <NUM> w/v%, even when the type and concentration of the antioxidant were verified under the same conditions, compositions showing good stability were similarly obtained.

In the storage test of the compositions of Table <NUM> as well, it was found that p-boronophenylalanine was retained in the aqueous solutions of the Examples at <NUM>% or more even after <NUM> weeks or more. In the retention property observation, no change in components were observed even from change in color and appearance. In Examples <NUM> to <NUM>, an initial increase in tyrosine content was observed. On the other hand, a fructose preparation remarkably decomposes and changes in color and the BPA concentration is greatly reduced, whereas the injection solutions of the Examples containing sorbitol or mannitol show little change in concentration and are stable.

By comprehensively determining the results of solubility and the storage test, it was found that the injection solutions containing sorbitol or mannitol of the Examples have excellent stability at a pH of <NUM> to <NUM>, and <NUM> storage, and also excellent homogeneity of the solution.

An aqueous solution containing <NUM> w/v% BPA, D-sorbitol and sodium bisulfite was prepared as follows. That is, first, <NUM> of sodium hydroxide was added to <NUM> of water, and the mixture was stirred. <NUM> of L-BPA was suspended therein. <NUM> of D-sorbitol was added thereto, and the mixture was stirred at room temperature for <NUM> minutes to completely dissolve the D-sorbitol. <NUM> of sodium bisulfite was added thereto, and an appropriate amount of <NUM> mol/l hydrochloric acid or <NUM> mol/l citric acid was added thereto at room temperature to adjust pH, and water was added to make a total amount of <NUM>.

The thus prepared aqueous BPA sorbitol solution was subjected to stability test <NUM>. In this test, the aqueous BPA sorbitol solution was subjected to a storage test at <NUM>. In this storage test, the sample was allowed to stand at <NUM> ± <NUM>/ambH/dark place, and the presence or absence of cloudiness and the time until cloudiness occurred were measured. The results are shown in Table <NUM>.

As a result, it was found that, in Example <NUM> in which hydrochloric acid was used as a regulator at a pH of <NUM>, cloudiness might occur after storage.

Next, an aqueous solution containing <NUM> w/v% BPA, D-sorbitol, and sodium bisulfite was prepared as follows. That is, first, <NUM> of sodium hydroxide was added to <NUM> of water, and the mixture was stirred. <NUM> of L-BPA was suspended therein. <NUM> of D-sorbitol was added thereto, and the mixture was stirred at room temperature for <NUM> minutes to completely dissolve the D-sorbitol. <NUM> of sodium bisulfite was added thereto, and an appropriate amount of <NUM> mol/l hydrochloric acid was added thereto at room temperature to adjust pH, and water was added to make a total amount of <NUM>.

As a result, when hydrochloric acid was used, cloudiness might occur when stored at <NUM>, especially in a low pH region. On the other hand, precipitation could be suppressed by adding citric acid instead of hydrochloric acid. In an intravenous injection, the presence (precipitation) of insoluble fine particles poses a problem, but the precipitation can be suppressed even during storage at low temperatures, so that a stable and excellent preparation can be prepared.

Using the same aqueous solution as in Example <NUM> as an injection solution except for adjusting to <NUM> w/v% of sodium bisulfite and an osmotic pressure ratio of <NUM>, neutron capture therapy was performed to subjects with <NUM> cases of head and neck cancer that were ineffective in standard treatment. Prior to administration of the injection solution, Positron Emission Tomography (PET) was used to measure accumulation of p-boronophenylalanine. The radioactive compound labeled obtained by labeling p-boronophenylalanine with radionuclide <NUM>F (18F-fluoro-borono-phenylalanine: FBPA) was administered, and the accumulation of boron compounds was estimated by imaging whole body distribution by PET examination. The injection solution was administered to subjects having a boron concentration ratio of cancer tissue/normal tissue of <NUM> or more by such PET examination.

Prior to irradiation, the injection solution was administered to the subjects in advance. In order that boron <NUM> will collect in tumors, the injection solution for intravenous administration was adjusted so as to have a BPA concentration of <NUM>/kg/hour for each patient and administered for <NUM> hours, then deceleratingly administered so as to be <NUM>/kg/hour dose, and epithermal neutron rays were irradiated during the decelerating administration.

Concerning p-boronophenylalanine by administration, it could be confirmed that the blood concentration of boron <NUM> was about <NUM> ppm (<NUM><NUM> boron <NUM> atoms per cell) or more and <NUM> ppm or less. Thus, the blood concentration was measured, and the amount in these tumor tissues or cells was predicted.

For each head and neck cancer patient, a mucosal dose was set to about <NUM> Gy-Eq, and irradiation was performed for about <NUM> minutes per time at maximum. A graph showing a relationship between a time (horizontal axis (hr)) when the injection solution used in this test was dripped to a subject and a blood concentration of <NUM>B (µg/ml) is shown (<FIG>). Concerning p-boronophenylalanine by administration, the blood concentration of boron <NUM> was confirmed to be <NUM> ppm or more and <NUM> ppm or less, and with regard to particularly effective subjects, it was shown that the values were in this range at a time zone of <NUM> hours or more and more than <NUM> hours after the start of administration (<FIG>).

As a result, first of all, no adverse event during administration of the injection solution was observed in any of the subjects. That is, none of the subjects developed shock symptoms at the time of administration. In addition, phlebitis was not observed after administration. After neutron irradiation, in <NUM> cases, an effect of tumor reduction could be obtained for <NUM> days. A <NUM>-day response rate was <NUM>%.

Using the same aqueous solution as in Example <NUM> as an injection solution except for adjusting to <NUM>% of sodium bisulfite and an osmotic pressure ratio of <NUM>, neutron capture therapy was performed to subjects with brain tumors that were ineffective in standard treatment. Prior to administration of the injection solution, Positron Emission Tomography (PET) was used to measure accumulation of p-boronophenylalanine. The radioactive compound labeled obtained by labeling p-boronophenylalanine with radionuclide <NUM>F (18F-fluoro-borono-phenylalanine: FBPA) was administered, and the accumulation of boron compounds was estimated by imaging whole body distribution by PET examination. The injection solution was administered to subjects having a boron concentration ratio of cancer tissue/normal tissue of <NUM> or more by such PET examination.

For each brain tumor patient, a skin dose was set to about <NUM> Gy-Eq, and irradiation was performed for about <NUM> minutes per time at maximum.

Claim 1:
An injection solution for boron neutron capture therapy, the injection solution comprising:
p-boronophenylalanine or a pharmaceutically acceptable salt thereof, with a ratio of boron <NUM> of boron atoms in a compound of <NUM> % or more;
sorbitol;
an antioxidant selected from the group consisting of sodium pyrosulfite, sodium sulfite, and sodium bisulfite; and
water,
the injection solution having a pH of <NUM> to <NUM> and an osmotic pressure ratio of <NUM> to <NUM>,
the injection solution being to be administered by intravenous drip injection.