JP2019167321A - Formulation for intravenous injection including boron amino acid and boron neutron capture treatment - Google Patents

Abstract

To provide an accumulation method of boron amino acid and a boron neutron capture treatment capable of enhancing BPA accumulation density of boron amino acid to cancer to treatment effective density by boron neutron capture treatment, and improving contrast of boron accumulation quantity between cancer and a peripheral normal tissue by boron amino acid administration, relative to prior arts.SOLUTION: There is provided a method for administering an administration liquid of boron amino acid to a subject for accumulating boron amino acid to cancer, in which, in boron amino acid formed of an L body and a D body, a ratio of the D body is 60% or more.SELECTED DRAWING: None

Description

  The present invention relates to a method for accumulating boron amino acids in cancer and boron neutron capture therapy, and more particularly to a technique for accumulating boron amino acids in human (human) or animal cancer.

  In recent years, it is said that one out of every two people will get cancer, and cancer treatment is an urgent issue. In addition, in various fields including veterinary medicine, interest in cancer treatment by irradiation of animals (especially dogs and cats) is increasing.

  As one of the cancer treatments, there is boron neutron capture therapy (BNCT) which is an example of radiotherapy (Patent Document 1).

Boron neutron capture therapy, after administered to cancer patients was integrated into the cancer cells by easily boron-10 incorporated into cancer cells boron acids containing ^{(10 B)} intravenous injection or infusion or the like, cancer Cancer treatment is performed by irradiating cells with neutron beams. There are two types of boron isotopes, Boron-10 and Boron-11. Boron-11 occupies about 80% of natural boron. It is easy to fission into lithium nuclei and is effective with small doses and small neutron irradiation.

  By irradiating cancer cells into which boron-10 has been incorporated with neutrons, alpha rays and lithium nuclei generated by the nuclear reaction between neutrons and boron-10 selectively destroy only cancer cells. Treat cancer.

  Boron neutron capture therapy is composed of many academic and technical fields, and it can be said that the most important technology is the development of an excellent boron amino acid preparation used for boron neutron capture therapy.

  In boron neutron capture therapy, boron amino acids are required to enhance the therapeutic effect that boron atoms migrate to cancer cells of cancer patients and easily accumulate in cancer cells above the therapeutically effective concentration in boron neutron capture therapy. Is done.

Therefore, it is important that boron amino acid preparations are selectively and reliably taken up by cancer. Incidentally, the therapeutically effective concentration of boron amino acid for cancer is 20 ppm or more, preferably 40 ppm or more as ¹⁰ B concentration.

  So far, various boron amino acid preparations have been developed and evaluated, but the boron amino acid preparation that has been put to practical use in clinical research is the first generation p-boronophenylalanine (hereinafter referred to as BPA) from around 1987. .

  This BPA includes an L-form (left-type) BPA (L-BPA) in which the phenylalanine moiety has the same configuration as that of natural phenylalanine, and an L-form BPA that has an optical isomerism relationship (right-form). Type) BPA (D-BPA) and a racemate (L-form 50%, D-form 50%) in which L-BPA and D-BPA are equally mixed.

  Among the above-mentioned three types of BPA, the amino acid that is a constituent element of the human body is the L-form, and the L-form BPA having affinity for the biological mechanism is most easily taken up into the cell tissue.

FIG. 7 is a comparison of the affinity of L-BPA and D-BPA for the biological mechanism. Relative uptake PSL with respect to time after administration to normal mouse organs (brain, blood, pancreas) (Luminescence) / mm ² is graphed. As can be seen from the graph, L-BPA has higher accumulation in organs than D-BPA.

  On the other hand, as seen in FIG. 7, the accumulation of D-BPA is extremely low compared to the high accumulation of L-BPA in the organ. From this, it is considered that D-BPA does not reach the therapeutically effective concentration described above and is not suitable for boron neutron capture therapy. Conventionally, D-BPA has been excluded from boron neutron capture therapy.

For this reason, L-form BPA is mainly used in conventional methods for accumulating boron amino acids in cancer and neutron capture therapy (for example, Patent Document 2).
Against this background, improvements have been made mainly in the composition of L-form boron amino acid preparations (for example, Patent Document 2 and Patent Document 3). On the other hand, since the actual state of the properties of D-form boron amino acid was not clear, the development of a control method (pharmacokinetic control method) of pharmacokinetics (absorption, distribution, metabolism, excretion) that paid attention to this has been carried out. There wasn't.

  Here, pharmacokinetic control is specifically explained. It indicates one of improvement of accumulation in cancer, improvement of contrast between cancer and surrounding normal tissue, convection in the body for a certain period of time, and rapid urinary excretion. . These are affected by metabolic stability, solubility in the blood pH region, and the like.

JP 2016-159107 A JP 2008-100953 A JP 2009-051766 A

  However, in the conventional method of accumulating in cancer and boron neutron capture therapy using an L-form boron amino acid preparation, improvement of pharmacokinetics control, in particular, improvement of accumulation in cancer and between cancer and surrounding normal tissues It was still insufficient in terms of improving the contrast of the amount of boron accumulation.

  That is, when L-form BPA is administered to a subject cancer patient, it is taken into normal tissues as well as L-amino acids, which are natural nutrients. The contrast gets worse. Therefore, there is a problem that when neutron rays are irradiated to the surrounding normal tissue, the exposure due to the nuclear reaction of boron that is distributed in a large amount in the irradiated normal tissue is large.

  Against this background, a boron amino acid accumulation method and boron neutron capture that improve the contrast of the amount of boron accumulation between the cancer and surrounding normal tissue by administration of BPA as compared with conventional techniques to minimize the exposure of normal tissue. There is a need for therapy. In this improvement in contrast, it is a major premise that the BPA accumulation concentration for cancer can be increased to the therapeutically effective concentration by boron neutron capture therapy.

  The present invention has been made in view of such circumstances, and can increase the BPA accumulation concentration of boron amino acid against cancer to a therapeutically effective concentration by boron neutron capture therapy, and cancer and its surroundings by administration of boron amino acid. An object of the present invention is to provide a boron amino acid accumulation method and a boron neutron capture therapy that can reduce the contrast of the amount of boron accumulation with a normal tissue as compared with the conventional tissue, and can reduce the exposure of the normal tissue as compared with the conventional tissue.

  In order to achieve the above object, a method of accumulating boron amino acids in cancer according to the present invention is a method of administering a boron amino acid administration solution to a subject and accumulating in cancer, wherein L-form and D-form boron Among amino acids, boron amino acid having a D-form ratio of 60% or more is used.

  In a preferred embodiment of the method for accumulating boron amino acids in cancer of the present invention, the D-form ratio is 100%. The boron amino acid is preferably p-boronophenylalanine.

  In order to achieve the above object, the boron neutron capture therapy according to the present invention includes an accumulation process in which a boron amino acid is administered to a subject and accumulated in cancer, and a neutron beam from a neutron generator is irradiated to the affected area of the subject. In the neutron capture therapy having a neutron irradiation process, a boron amino acid having a D-form ratio of 60% or more of the L-form and D-form boron amino acids is used in the accumulation process. Here, the neutron generator includes a nuclear reactor, an accelerator, and the like.

  A preferred embodiment of the boron neutron capture therapy of the present invention has a D-form ratio of 100%. The boron amino acid is preferably p-boronophenylalanine.

  According to the method for accumulating boron amino acids in cancer according to the present invention, the concentration of BPA accumulated in cancer can be increased to the therapeutically effective concentration by boron neutron capture therapy, and boron in cancer and surrounding normal tissue by BPA administration can be increased. The contrast of the accumulation amount can be remarkably improved as compared with the conventional case.

  Also, according to the boron neutron capture therapy of the present invention, the contrast of the amount of boron accumulated between cancer and surrounding normal tissue by BPA administration can be remarkably improved as compared with the conventional case, so that the exposure of normal tissue is reduced as compared with the conventional case. Can do.

Explanatory drawing explaining the synthesis method of L-BPA and D-BPA of ¹⁴ C label Autoradiogram (image photo) showing the contrast of the amount of boron accumulation between cancer and surrounding normal tissue by BPA administration Table showing test results of BPA accumulation relative ratio test Table showing test results of BPA treatment effective concentration test The graph which shows the test result of the integration test of L-BPA and D-BPA Table for examining the ratio of D-forms in boron amino acid preparations based on the graph of FIG. Graph examining the accumulation of L-BPA and D-BPA in normal mouse organs

  Hereinafter, preferred embodiments of a method for accumulating boron amino acids in cancer and boron neutron capture therapy according to the present invention will be described in detail with reference to the accompanying drawings.

[Configuration of the present invention]
The method for accumulating boron amino acids in cancer according to the present invention is a method in which a boron amino acid is administered to a subject and accumulated in cancer. The main invention is to use a boron amino acid preferably having a D-form ratio of 100%.

  Further, the boron neutron capture therapy according to the present invention is a neutron having an accumulation process for administering a boron amino acid to a subject and accumulating it in cancer, and a neutron irradiation process for irradiating an affected area with a neutron beam from a neutron generator. In the capture therapy, in the accumulation process, among the L-form and D-form boron amino acids, a boron amino acid having a D-form ratio of 60% or more (preferably a D-form ratio of 100%) is mainly used.

[Background of the present invention]
The inventor has heretofore established that cell accumulation is extremely lower than that of L-form p-boronophenylalanine (hereinafter referred to as L-BPA) and is not suitable for boron neutron capture therapy. As a result of reviewing the p-boronophenylalanine (p-phenylalanine: hereinafter referred to as D-BPA), the following knowledge was obtained.

  (1) D-BPA is a D-form different from the L-amino acid structure, which is a constituent of the human body, and therefore has a low physiological accumulation in normal tissues and disappears quickly from the blood. Will gradually accumulate. Thereby, the accumulation relative ratio (cancer / normal tissue) of D-BPA in cancer and normal tissue can be remarkably increased. Here, the cancer includes tumors (cancer, sarcoma), malignant melanoma, and the like.

(2) When viewed at a therapeutically effective concentration in neutron capture therapy ( ¹⁰ B concentration of 20 ppm or more, preferably 40 ppm or more), D-BPA is substantially equivalent to L-BPA when administration duration exceeds 20 minutes. The therapeutically effective concentration for cancer is reached.

  (3) Due to the characteristics of D-BPA in (1) and (2) above, the contrast of the amount of boron accumulation between cancer and surrounding normal tissue in images and videos can be significantly improved. Thereby, in boron neutron capture therapy, since cancer and surrounding normal tissue can be clearly distinguished, the exposure of normal tissue can be significantly reduced as compared with the conventional case.

  In the present embodiment, an example of BPA that is mainly used as a boron amino acid will be described below. However, it is considered that the present invention can also be applied to a boron amino acid having an amino acid structure other than BPA.

  Next, the tests that led to the above findings and the results thereof will be described below.

(A) Contrast test
^When radioactivity of ¹⁴ C-D-BPA and ¹⁴ C-L-BPA having a ¹⁴ C-labeled substance is administered to a mouse having cancer, the contrast of the amount of boron accumulation between the cancer and the surrounding normal tissue is autoradiogram. Contrast by (image photograph).

(B) Accumulation relative ratio test
^When D-BPA without ¹⁴ C-labeled substance and ¹⁴ C-L-BPA were respectively administered to mice with cancer, the amount of boron in the cancer and normal tissue was determined by high frequency inductively coupled plasma emission spectrometry ( ICP method), and the accumulation relative ratio of BPA (cancer / normal tissue) between cancer and normal tissue was examined.

(C) Effective concentration test for cancer treatment
^When D-BPA and L-BPA without ¹⁴ C-labeled substance were each administered to mice with cancer, the amount of boron in the cancer was analyzed by high frequency inductively coupled plasma emission spectrometry (ICP method). . Then, the administration time was compared with the accumulation concentration in cancer, and it was examined whether D-BPA was accumulated to the therapeutic effective concentration for cancer by boron neutron capture therapy in the same manner as L-BPA. In addition, the BPA concentration in the brain where the cancer is present and the BPA concentration in the blood carrying the BPA to the cancer were examined.

[Protocol]
(Culture of cancer cells)
As a method for culturing cancer (cancer cells) used in the test, cell culture solution DMEM containing 10% fetal bovine serum and L-glutamine (3.5 mM) in 12 75 cm ² (t75) flasks, respectively. 20 mL of Dulbecco's Modified Eagle's Medium (Sigma-Aldrich)] was added. Then, as a cancer, mouse glioma GL261 cell line is seeded at 8.0 × 10 ⁵ cells in each flask containing the cell culture solution, and cultured at a temperature of 37 ° C., a pH of 7.4, and a CO ₂ concentration of 5%. The cells were cultured for 4 days in the lower incubator.

(Creation of cancer-bearing mice)
After the above culture, mouse glioma GL261 cells (1.02 × 10 ⁷ cells / mouse) suspended in 0.15 mL of a phosphate buffer solution were subcutaneously transplanted to 5-6 week old KSN-slc male mice. Thus, a tumor-bearing mouse for use in the test was obtained. And it tested when the cancer diameter of a cancer-bearing mouse became about 0.5-1.0 cm. Feeding and water for breeding cancer-bearing mice were performed in a normal SPF environment.

[Contrast test]
(Test method)
<Synthesis of ¹⁴ C-L-BPA and ¹⁴ CD-BPA>
FIG. 1 shows a synthetic route of ¹⁴ C-L-BPA and ¹⁴ CD-BPA. In FIG. 1, [ ¹⁴ C] L-phenylalanine (1) is used as a starting material, and the target ¹⁴ C-L-BPA or ¹⁴ CD- It shows that BPA is synthesized.

  In the following description of the synthesis route, when the numbers 2, 3, 4, and 5 are described together with the compound name, the number is parenthesized as in the compound name (2).

In the present embodiment, ¹⁴ C-L-BPA and ¹⁴ C-D-BPA were synthesized according to the synthesis methods described in the following documents, with some protecting groups being changed.
Literature… Malan, C .; Morin, CJOrg.Chem., 1998,63,801

As a preparation, the ^{[14 C]} was synthesized by Strecker method from KCN ^{[14 C]} DL-phenylalanine, optically resolved using tartaric acid, in FIG. 1 is the starting material for the synthesis of BPA L-form [ ¹⁴ C] L-phenylalanine (1) was obtained.

Next, as shown in FIG. 1, the obtained [ ¹⁴ C] L-phenylalanine (1) was iodinated to synthesize [ ¹⁴ C] 4-iodo-L-phenylalanine (2). The carboxyl group and amino group were each protected to obtain compound (3), and then converted to boronic acid ester (4) by coupling with pinacol borane. Moreover, the boronic acid (5) was obtained by deprotecting the converted boronic ester (4).

Finally, the carboxyl group and amino group were deprotected under acidic conditions to prepare the desired [ ¹⁴ C] L-BPA.

[ ¹⁴ C] D-BPA was synthesized by the same synthesis method as described above by using one of [ ¹⁴ C] D-phenylalanine optically resolved as a starting material.

<Preparation of ¹⁴ C-BPA administration solution>
^{For each of 14} C-L-BPA and ¹⁴ C-D-BPA, the physiological concentration was set to 185 kBq / 100 μL using physiological saline, and two types of ¹⁴ C, L-BPA and D-BPA, were used. -A BPA administration solution was prepared.

<Administration of ¹⁴ C-BPA administration liquid and acquisition of autoradiogram>
Of the plurality of tumor-bearing mice, one group of tumor-bearing mice is administered ¹⁴ C-L-BPA administration solution at 100 μL / mouse from the tail vein, and the other group of tumor-bearing mice is ¹⁴ C-D. -100 μL / mouse of BPA administration solution was administered from the tail vein.

  Immediately 30 minutes after the administration, each tumor-bearing mouse was euthanized by excessive aspiration of sevoflurane, and then the organ was removed, and the removed organ was measured by an autoradiograph.

  Autoradiography, also called radiography or autoradiography, is a method of creating autoradiograms (images) from beta-ray particles and gamma rays emitted from radioactive materials distributed in cellular tissues. It is. In biology, it is used as a method for confirming that a radioactive substance stays in a specific tissue.

(Test results)
(A) of FIG. 2 is an autoradiogram obtained by measuring an organ when a ¹⁴ C-L-BPA administration solution is administered to a tumor-bearing mouse. Moreover, (B) is an autoradiogram which measured about the organ when a ^14C -D-BPA administration liquid is administered to a cancer-bearing mouse.

  In FIGS. 2A and 2B, the part indicated by the arrow is the part of the cancer (tumor) transplanted to the tumor-bearing mouse.

As can be seen from the comparison of the image photographs of (A) and (B) in FIG. 2, the ¹⁴ C-D-BPA administration solution was compared with the case where the ¹⁴ C-L-BPA administration solution was administered to the tumor-bearing mice. When administered to cancer-bearing mice, the contrast of the amount of boron accumulation between the cancer and the surrounding normal tissue was remarkably higher (remarkably improved).

  From this, it can be seen that L-BPA has the property of being accumulated in both cancer and normal tissues, while D-BPA has the property of being highly selectively accumulated in cancer.

  Next, an accumulation relative ratio test and a therapeutically effective concentration test will be described.

[Aggregation relative ratio test and therapeutic effective concentration test]
L-BPA (cold compound) and D-BPA (cold compound) boron amino acid dosing solutions are administered to cancer-bearing mice, and they accumulate in cancer (cancer) and brain parenchyma (normal tissue). The relationship between the relative ratio and the BPA concentration in each organ (cancer, brain, blood) and the administration duration (hereinafter referred to as “administration time”) was examined.

Here, the cold compound refers to a compound having no ¹⁴ C label. The post-administration time described later refers to the time from the end of administration, and is distinguished from the administration duration (administration time).

The relative ratio of BPA accumulation to cancer and brain parenchyma (normal tissue) is indicated by the ratio of the concentration of BPA accumulation to cancer when the concentration of BPA accumulation to brain parenchyma is 1. Moreover, the therapeutically effective concentration for cancer was set to 20 ppm or more as the ¹⁰ B concentration as described above.

(Test method)
<Preparation of boron amino acid preparation>
A boron amino acid preparation was prepared by adding sugar to L-BPA (cold compound) or D-BPA (cold compound). In the present embodiment, D-form fructose is used as the sugar. Conventionally, D-form fructose is known to be able to increase the solubility of boron amino acid preparations in water.

For the cold compounds L-BPA and D-BPA, the following commercially available drugs from Merck were used.
・ L-BPA… 4-Borono-L-phenylalanine (Catalog No. 17755-250MG)
・ D-BPA… 4-Borono-D-phenylalanine (Cat. No. 68047-250MG)

  The final component concentrations of this boron amino acid preparation administered to cancer-bearing mice were adjusted to 5.41 W / V% sugar and 2.51 W / V% BPA for both L-BPA and D-BPA.

<Administration of administration liquid>
Each of the BPA administration solutions obtained as described above was continuously administered from the tail vein of cancer-bearing mice for 10 minutes, 20 minutes, and 30 minutes at an administration rate of 20 μL / min (min).

<Boron analysis>
Immediately after administration, each tumor-bearing mouse was euthanized by excessive aspiration of sevoflurane, and then the organ was removed. Boron analysis is performed on the removed organs by high frequency inductively coupled plasma optical emission spectrometry (ICP method), the relative accumulation ratio between cancer (tumor) and brain parenchyma (normal tissue), and each organ (cancer (tumor) ), Brain, blood) BPA concentration and administration duration were examined.

  The brain parenchyma may be a parenchyma of at least one site selected from the group consisting of the hippocampus and lateral / occipital cerebral cortex, forebrain cerebral cortex, and thalamus.

(Results of accumulation relative ratio test)
In the accumulation relative ratio test, the accumulation relative ratio (simply indicated as the relative ratio in FIG. 3) at 30 minutes (min), 60 minutes, and 120 minutes after administration was examined.

  As can be seen from FIG. 3, at any time after administration, the accumulation relative ratio (cancer (tumor) / brain parenchyma) of the boron amino acid preparation of D-BPA is higher than that of L-BPA. It was 20 times, far exceeding the 10 times that has been regarded as the goal of the treatment, and could be significantly increased. This is consistent with the result shown in the contrast test image.

  This shows that L-BPA tends to accumulate in both cancer and normal tissue, whereas D-BPA is less likely to accumulate in normal tissue, whereas it is more likely to accumulate in cancer than expected.

(Results of therapeutically effective concentration test)
(A) of FIG. 4 is a case where the administration liquid of the boron amino acid formulation of L-BPA is administered, (B) is a case of administering the administration liquid of the boron amino acid formulation of D-BPA.

  In the therapeutically effective concentration test, the boron concentration of multiple samples (see the number of samples in the table) of each organ at the administration time of 10 minutes (min), 20 minutes, and 30 minutes is measured and displayed as the average value and spread width. did.

As can be seen from the comparison between FIG. 4A and FIG. 4B, the boron amino acid preparation of D-BPA has a slightly lower concentration of boron accumulated in the cancer (tumor) than the boron amino acid preparation of L-BPA. However, the therapeutically effective concentration of 20 ppm (as ¹⁰ B) is substantially reached at 20 minutes after administration, and the therapeutically effective concentration can be reliably reached at 30 minutes after administration.

  From this, it was found that the boron amino acid preparation of D-BPA, which was considered not to reach a therapeutically effective concentration and was not suitable for boron neutron capture therapy, can sufficiently reach a therapeutically effective concentration. It was.

  In addition, regarding the brain having cancer (tumor) and the blood carrying BPA, the increase in the accumulated concentration at the administration time of 10 minutes, 20 minutes, and 30 minutes shows that both the brain and the blood have D-BPA at any administration time. This boron amino acid preparation is smaller than the L-BPA boron amino acid preparation. This is because the boron amino acid preparation of D-BPA is more likely to be excreted from normal tissues such as brain and blood than the boron amino acid preparation of L-BPA, and the accumulation of boron in the normal tissue can be reduced. I understand.

  From this, the L-form boron amino acid exhibits high accumulation in normal tissues other than cancer, while the D-form boron amino acid exhibits extremely selective accumulation against cancer.

  From the test results of the contrast test, the integrated relative ratio test and the therapeutically effective concentration test, D-BPA has a therapeutically effective concentration almost equal to that of L-BPA and is suitable for boron neutron capture therapy using L-BPA. In comparison, it was found that the contrast of the amount of boron accumulation between cancer and normal tissue can be significantly improved.

  Therefore, in boron neutron capture therapy, in order to maximize the contrast of the amount of boron accumulation between cancer and surrounding normal tissue, it is ideal that the boron amino acid is 100% in D form. However, producing a 100% D-BPA boron amino acid leads to an increase in the production cost of the boron amino acid preparation.

  Therefore, the present inventor examined the uptake time (same as the time after administration) and the uptake rate into cells when equal amounts of L-BPA and D-BPA were administered to cancer cells, and the uptake time. The preferred ratio of D-form and L-form in the boron amino acid preparation in consideration of the above was investigated.

(D) ¹⁴ C-L-BPA and ¹⁴ C-D-BPA uptake into cancer cells
^{When 14} C-labeled L-BPA and D-BPA are administered to cancer cells in equal amounts, the uptake into cells (the ease of uptake) is related to the uptake rate and uptake time. I examined it.

(Test method)
The DMEM of the cell culture medium used in the above cancer cell culture was removed from the dish. And it incubated for 10 minutes on 37 degreeC and the conditions of 2 mL of phosphate buffer solutions (PBS) containing Ca ^<2+ > of pH7.4.

Next, the phosphate buffer was removed from the dish, and 0 minutes in the presence of 2 mL of phosphate buffer containing ¹⁴ C-L-BPA or ¹⁴ CD-BPA with a radioactivity of 18.5 kBq, Incubated for 5 minutes, 10 minutes, 15 minutes, 30 minutes, 45 minutes, 60 minutes, 90 minutes, 120 minutes. That is, the uptake time was set to 0 minutes, 5 minutes, 10 minutes, 15 minutes, 30 minutes, 45 minutes, 60 minutes, 90 minutes, and 120 minutes.

  Thereafter, the phosphate buffer containing radioactivity is removed from the dish (petri dish) after each uptake time, the cell surface is washed twice with 4 ° C. phosphate buffer, and 2 mL of 1N NaOH is added. 24 hours later, the cells were lysed to obtain a measurement sample.

As a result, for each of ¹⁴ C-L-BPA and ¹⁴ C-D-BPA having the same radioactivity of 18.5 kBq, nine measurement samples were obtained, each having 9 different uptake times.

  And about 18 measurement samples, the radiation dose of 200 microliters of measurement samples was measured with the liquid scintillation counter.

That is, ¹⁴ C-L-BPA and ¹⁴ C-D-BPA having the same radioactivity of 18.5 kBq are brought into contact with cultured cells, respectively, and the time course of radioactivity is observed, so that L and D cancers are obtained. The relationship between the uptake rate into cells and the uptake time was examined.

(Test results)
FIG. 5 is a graph showing the uptake rate with respect to the uptake time, with the uptake rate of ¹⁴ C-BPA in the cells with respect to the uptake time (same as the time after administration) on the horizontal axis. . In the graph of FIG. 5, the rhombus (♦) plot is ¹⁴ C-L-BPA and the square (■) plot is ¹⁴ C-D-BPA. The uptake rate on the vertical axis shows the uptake amount in each uptake time as a percentage (%) when the total dose of ¹⁴ C-BPA is 100. The uptake time is shown in minutes.

FIG. 6 shows specific numerical values of the uptake rate of ¹⁴ C-L-BPA or ¹⁴ C-D-BPA at each uptake time.

As shown in FIG. 5, the transition of the uptake rate of ¹⁴ CD-BPA into cancer cells increased to the vicinity of the maximum value at the uptake time of 5 minutes and maintained the maximum value until the uptake time of 15 minutes. Later, it gradually decreases. On the other hand, the transition of the uptake rate of ¹⁴ CD-BPA into cancer cells continues to rise gradually until the uptake time of 120 minutes.

As can be seen from the graph of FIG. 5, ¹⁴ C-D-BPA has a high uptake rate into cancer cells, but ¹⁴ C-D-BPA once taken into cancer cells is cancer cells over time. It turns out that there is a nature that flows out. On the other hand, ¹⁴ C-D-BPA has a slow uptake rate into cancer cells, but ¹⁴ C-D-BPA once taken into the cancer cells can flow out of the cancer cells even after a lapse of time. It can be seen that it has the property of accumulating in cancer cells.

As can be seen from the table in FIG. 6, the uptake rate of ¹⁴ C-L-BPA at a 5 min uptake time is 15.933%, whereas the uptake rate of ¹⁴ C-D-BPA is 1. 555%. That is, with an uptake time of 5 minutes, ¹⁴ C-L-BPA is taken up by cancer cells at an accumulation rate ratio (L / D) of 10.246 times that of ¹⁴ C-D-BPA. In other words, with an uptake time of 5 minutes, ¹⁴ C-D-BPA has an accumulation rate of 1 / 10.246 of ¹⁴ C-L-BPA and has a small cancer cell accumulation effect.

Thus, when viewed in uptake rate of capture time 5 ^{min, 14} C-D-BPA to obtain a ¹⁴ C-L-BPA equal or cancer cell in an integrated ^{effect, 14} C-D-BPA Requires a concentration greater than 10.246 times that of ¹⁴ C-L-BPA. That is, in order to obtain a boron amino acid preparation having an effect of accumulating in cancer cells that is equal to or higher than that of conventional L-BPA alone boron amino acid preparation with an uptake time of 5 minutes, D-form of L-form and D-form BPA It can be seen that the ratio should be greater than 0.9111 (91.11%).

However, as can be seen from FIG. 5, ¹⁴ C-D-BPA once accumulated in cancer cells is unlikely to flow out of cancer cells unlike ¹⁴ C-L-BPA. Since the rate increases, it is possible to compensate for the slow capture speed with the capture time. In this case, in the boron neutron capture therapy, taking into account the administration time of the administration solution of the boron amino acid preparation to the subject and the neutron emission time after administration, it is difficult to practically consider the uptake time of 120 minutes or more. Therefore, when the ratio of D-form at the capture time of 120 minutes, preferably 60 minutes, is calculated, they are 59.55% (capture time of 120 minutes) and 68.5% (capture time of 60 minutes).

  In other words, it has the same or better cancer cell accumulation effect than the L-BPA boron amino acid preparation conventionally used for boron neutron capture therapy, and the contrast of the amount of boron accumulation between cancer and normal tissue has been improved. In order to obtain a practical boron amino acid preparation, it can be said that it is preferable to have a D-form ratio of 59.55% (uptake time 120 minutes) or more and a clear numerical value of 60% or more.

  Incidentally, in the case of a racemate (L-form 50%, D-form 50%), it is considered that an effective cancer cell accumulation effect cannot be obtained within the above-described practical uptake time of 120 minutes.

[Summary of effects of the present invention]
(I) By using the boron amino acid accumulation method and boron neutron capture therapy according to the present invention, boron accumulation in normal tissues can be reduced, and the contrast of the amount of boron accumulation between cancer and normal tissues has been conventional. Becomes significantly clearer than. Thereby, it becomes possible to irradiate only about cancer with the neutron beam by a boron neutron capture therapy, Therefore The exposure to the normal structure | tissue by a neutron beam can be made remarkably small.

  (II) Since the accumulation of boron in normal tissues can be reduced, the dose of BPA can be reduced accordingly, and the cost of the BPA drug can be reduced.

  (III) D-BPA is less likely to be metabolized than L-BPA, and the distribution in the body is very simple and pharmacokinetics can be easily grasped compared to L-BPA, in which many types of metabolites are produced by metabolism. Thereby, D-BPA is easier to predict the therapeutic effect than L-BPA.

For application to animals other than mice and humans (humans), for example, the distribution in the body is imaged by positron emission tomography using ¹¹ C-labeled D-BPA or ¹⁸ F-labeled D-BPA, and boron. It may be diagnosed in advance whether a preparation using 10 can be accumulated in cancer in an individual to which the preparation is to be applied.

As shown in FIG. 5, the transition of the uptake rate of ¹⁴ C- L- BPA into cancer cells increased to the vicinity of the maximum value at the uptake time of 5 minutes and maintained the maximum value until the uptake time of 15 minutes. Later, it gradually decreases. On the other hand, the transition of the uptake rate of ¹⁴ CD-BPA into cancer cells continues to rise gradually until the uptake time of 120 minutes.

As can be seen from the graph of FIG. 5, ¹⁴ C- L- BPA has a high uptake rate into cancer cells, but ¹⁴ C- L- BPA once taken into cancer cells is cancer cells over time. It turns out that there is a nature that flows out. On the other hand, ¹⁴ C-D-BPA has a slow uptake rate into cancer cells, but ¹⁴ C-D-BPA once taken into the cancer cells can flow out of the cancer cells even after a lapse of time. It can be seen that it has the property of accumulating in cancer cells.

Claims (6)

In a method of administering a boron amino acid administration solution to a subject and accumulating it in cancer,
A method for accumulating boron amino acids in cancer, wherein a boron amino acid having a D-form ratio of 60% or more of L-form and D-form boron amino acids is used.   2. The method for accumulating boron amino acids in cancer according to claim 1, wherein the ratio of the D form is 100%.   The method according to claim 1 or 2, wherein the boron amino acid is p-boronophenylalanine. An accumulation process in which a subject is administered a boron amino acid administration solution and accumulates in cancer;
In a neutron capture therapy having a neutron irradiation process of irradiating the affected part of the subject with a neutron beam from a neutron generator or a reactor,
Boron neutron capture therapy using a boron amino acid having a D-form ratio of 60% or more of L-form and D-form boron amino acids in the accumulation process.   The boron neutron capture therapy according to claim 4, wherein the ratio of the D form is 100%.   The boron neutron capture therapy according to claim 4 or 5, wherein the boron amino acid is p-boronophenylalanine.