ACCUMULATIVE BORON 10 MEDICINE FOR BORON NEUTRON CAPTURE THERAPY FOR SELECTIVELY OR LOCALLY TARGETING TUMOR TISSUES IN SHORT TIME

Abstract

The purpose of the present invention is to provide a .sup.10B medicine that can be selectively accumulated in tumor tissues at a low dose in a short time, and can be applied to BNCT. The .sup.10B medicine comprises a compound containing: a peptide capable of selectively binding to tumor vascular endothelial cells; and .sup.10B, wherein the .sup.10B medicine is administered to a subject suffering from cancer at a dose of 300-600 mg per administration, and is accumulated after the administration such that the concentration of .sup.10B in the cancer tissue of the subject becomes 1 ppm or higher.

Claims

1-17. (canceled)

18. A method for treating cancer by BNCT, comprising: administering, by an intravenous injection, an accumulative .sup.10B drug comprising a compound comprising .sup.10B-containing group and a peptide capable of selectively binding to a tumor vascular endothelial cell, the peptide binding directly or via a linker to the .sup.10B-containing group, to a subject affected with cancer in an amount from 300 to 600 mg/administration, and a dosage amount per administration to the subject of 5 to 9 mg per unit body weight (1 kg) of the subject, accumulating the .sup.10B drug in a cancer-affected tissue of the subject after the administration so that a .sup.10B level therein is 1 ppm or more, and performing neutron irradiation within 60 minutes after the administration, wherein the peptide is a peptide capable of selectively binding to annexin 1, wherein the peptide comprises an amino acid sequence of IFLLWQR (amino acids 1 to 7 of SEQ ID NO: 1), an amino acid sequence of IFLLWQRX (amino acids 1 to 8 of SEQ ID NO: 1), an amino acid sequence of IFLLWQRXX (amino acids 1 to 9 of SEQ ID NO: 1), an amino acid sequence of IFLLWQRXXX (amino acids 1 to 10 of SEQ ID NO: 1), an amino acid sequence of IFLLWQRXXXX (amino acids 1 to 11 of SEQ ID NO: 1), or an amino acid sequence of IFLLWQRXXXXX (amino acids 1 to 12 of SEQ ID NO: 1), wherein each X independently represents a polar or charged amino acid, and wherein one or two amino acids of IFLLWQR in each of the amino acid sequences may be substituted.

19. The method according to claim 18, wherein the accumulative .sup.10B drug accumulates so that the .sup.10B level in the cancer-affected tissue of the subject is 20 ppm or more.

20. The method according to claim 18, wherein the .sup.10B level in the cancer-affected tissue is 1 ppm or more during a period from 10 minutes to 30 minutes after the administration of the accumulative .sup.10B drug.

21. The method according to claim 18, wherein the .sup.10B-containing group is an L-p-[10B]boronophenylalanine group, an [18F]fluoro[10B]boronophenylalanine group, or a [10B]borocaptate group.

22. The method according to claim 18, wherein the .sup.10B-containing group is an L-p-[10B]boronophenylalanine group, an [18F]fluoro[10B]boronophenylalanine group, or a [10B]borocaptate group.

23. The method according to claim 18, wherein the peptide and a .sup.10B-containing group are linked to each other via a linker.

24. The method according to claim 23, wherein the .sup.10B-containing group is an L-p-[10B]boronophenylalanine group or an [18F]fluoro[10B]boronophenylalanine group, and wherein the .sup.10B-containing group is linked to the linker via an ester bond or the linker contains an ester bond.

25. The method according to claim 23, wherein the .sup.10B-containing group is a [10B]borocaptate group and wherein the linker contains no ester bond.

26. The method according to claim 23, wherein the linker is a linker represented by the following formula (i) or (ii): ##STR00010## wherein * and ** each represent a bond.

27. The method according to claim 18, wherein the compound is a compound containing a structure represented by the following formula (i-1) or (ii-1): ##STR00011## wherein * and ** each represent a bond at which the peptide capable of selectively binding to a tumor vascular endothelial cell binds.

28. The method according to claim 18, wherein the .sup.10B drug is used to perform neutron irradiation at a dose of 2×10.sup.6/cm.sup.2 s or more.

29. The method according to claim 18, wherein the cancer is at least one cancer selected from the group consisting of bladder cancer, brain cancer, prostate cancer, melanoma, breast cancer and colon cancer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present invention is illustrated by the following drawings:

[0033] FIG. 1 includes drawings illustrating .sup.10B levels (ppm) in organs of tumor-bearing mice measured 5, 10, and 20 minutes after 100 μL (175 μg) of IF7-.sup.10BPA or IF7-.sup.10BSH prepared to be 7 mg/kg was administered through the tail vein;

[0034] FIG. 2 is a drawing illustrating .sup.10B levels (ppm) in organs of tumor-bearing mice, measured 20, 40, and 60 minutes after 100 μL (2,000 μg) of a .sup.10BPA-fructose prepared to be 100 mg/kg was administered through the tail vein;

[0035] FIG. 3 includes drawings showing violin plots of .sup.10B levels (ppm) in organs of cancer-bearing mice 10, 20, and 40 minutes after tail vein administration of IF7-.sup.10BPA prepared to be 7 mg/kg or .sup.10BPA prepared to be 7 or 100 mg/kg (in the case of 100 mg/kg, measurement was performed 60 minutes after the administration);

[0036] FIG. 4 includes drawings showing violin plots of .sup.10B levels (ppm) in organs of cancer-bearing mice measured 5, 10, 20, and 40 minutes after IF7-.sup.10BSH or .sup.10BSH prepared to be 7 mg/kg was administered through the tail vein;

[0037] FIG. 5 includes drawings illustrating results of a hot group irradiated with neutrons 40 minutes after administration of IF7-.sup.10BSH or IF7-.sup.10BPA to cancer-bearing mice and results of a cold group which was not irradiated; and

[0038] FIG. 6 includes drawings illustrating results of a hot group irradiated with neutrons 40 minutes after administration of IF7-.sup.10BPA or .sup.10BPA to cancer-bearing mice and results of a cold group which was not irradiated.

PREFERRED MODE FOR CARRYING OUT THE INVENTION

[0039] Below, embodiments of the present invention are described in detail, but the present invention is not limited to the following embodiments and can be implemented within the scope of the object of the present invention with appropriate modifications. In addition, in this specification, “A to B” means that both limits, A and B, are included, unless otherwise specified.

<<Anticancer Drugs>>

[0040] The accumulative .sup.10B drug of the present invention includes a compound containing .sup.10B and a peptide capable of selectively binding to a tumor vascular endothelial cell. The compound is administered to a cancer-affected subject at an amount of 300 to 600 mg/administration and accumulates after the administration so that a .sup.10B level in a cancer-affected tissue of the subject is at least 1 ppm (preferably at least 20 ppm). The present accumulative .sup.10B drug is suitable for BNCT, because the drug contains the compound containing .sup.10B and a peptide capable of selectively binding to a tumor vascular endothelial cell, so that even when the dosage amount per administration is from 300 and 600 mg, which is lower than the dosage amounts of conventional .sup.10B preparations for BNCT, the accumulative .sup.10B drug of the present invention can accumulate so that the .sup.10B level in the cancer-affected tissue is 1 ppm or more (preferably 20 ppm or more). Additionally, the accumulative .sup.10B drug of the present invention reaches the tumor via tumor vascular endothelial cells when applied to BNCT; therefore, not only the .sup.10B drug taken up by the tumor itself, but also the .sup.10B drug taken up by the tumor blood vessels or cells can destroy the tumor blood vessels; and thereby tumor growth is indirectly inhibited. Accordingly, the accumulative .sup.10B drug of the present invention may require accumulation of .sup.10B in the tumor tissue at a high level (e.g., 20 ppm or more) or may not require such a high level (that is e.g., 1 to 20 ppm is satisfactory).

[0041] The subject is not particularly limited as long as the subject is affected with cancer, and examples include mammals (e.g., humans, swine, cattle, mice, rats, etc.) that are affected with cancer and humans (subjects or patients) who are affected with cancer are preferred.

[0042] A single dosage amount to the subject is preferably 300 to 600 mg, and more preferably 400 to 500 mg from the viewpoint of achieving a killing effect of cancer tissue by BNCT at a low dosage amount in order to suppress side effects. Further, when the accumulative .sup.10B drug is administered at a low dosage amount per unit body weight (1 kg) of 5 to 9 mg, preferably 6 to 8 mg, to the subject in order to suppress side effects, the drug can accumulate so that the .sup.10B level in the cancer-affected tissue is 1 ppm or more (preferably 20 ppm or more).

[0043] As values of .sup.10B levels in cancer-affected tissue, values obtained by measuring under the conditions used in the Examples below by prompt-gamma-ray analysis (PGA method) are employed, unless otherwise specified. As the .sup.10B level in the cancer-affected tissue, from the viewpoint of the killing effect of the cancer tissue by BNCT, 2 ppm or more, 3 ppm or more, 4 ppm or more, or 5 ppm or more are preferable, 6 ppm or more, 7 ppm or more, 8 ppm or more, 9 ppm or more, or 10 ppm or more is more preferable, 11 ppm or more, 12 ppm or more, 13 ppm or more, 14 ppm or more, or 15 ppm or more is still more preferable, 20 ppm or more is even more preferable, 25 ppm or more is particularly preferable, 30 ppm or more is more particularly preferable, 35 ppm or more is especially particularly preferable, and 40 ppm or more is the most preferable. The upper limit of the .sup.10B level in cancer-affected tissue is not particularly limited as long as the effect of the present invention is not impaired, but examples of the level less than 20 ppm include 19 ppm or less, typically 18 ppm or less, and preferably 17 ppm or less. When the .sup.10B level is 20 ppm or more, the .sup.10B level is, for example, 200 ppm or less, typically 150 ppm or less, preferably 100 ppm or less, more preferably 80 ppm or less, most preferably 70 ppm or less, and particularly preferably 60 ppm or less.

[0044] Here, “accumulative” means that the .sup.10B drug selectively heads for or locally exists in cancer-affected tissue rather than another tissue or normal tissue in the subject. For example, it can be mentioned that the .sup.10B drug selectively and locally exists in cancer-affected tissue rather than in another tissue or normal tissue. The .sup.10B drug locally exists in cancer-affected tissue at a .sup.10B level of preferably 1.2 times or more, more preferably 1.5 times or more, still more preferably 2 times or more, even more preferably 3 times or more, and most preferably 4 times or more, relative to the .sup.10B level in the other tissue or normal tissue. Although the upper limit is not particularly limited, examples thereof include 50 times or less, and typically 30 times or less.

[0045] From the viewpoint that the above-mentioned compound rapidly accumulates in cancer-affected tissue and BNCT can be rapidly applied, the administration preferably results in the .sup.10B level in the cancer-affected tissue being 1 ppm or more (preferably 20 ppm or more), during a period from 5 minutes to 60 minutes (preferably 10 minutes to 50 minutes, more preferably 10 minutes to 40 minutes, more preferably 15 minutes to 30 minutes, particularly preferably 15 minutes to 25 minutes, and most preferably 15 minutes to 20 minutes) after the above-mentioned administration.

[0046] Administration method may be any of parenteral administration, inhalation administration, oral administration, and direct administration (DDD=Direct Drug Delivery). However, from the viewpoint that the compound can rapidly accumulate in cancer-affected tissue and can be quickly applied in BNCT, parenteral administration is preferable. Injection administration such as subcutaneous injection, intraperitoneal injection, intramuscular injection, etc., intravenous drip infusion, or direct administration to the affected part by endoscope or catheter is more preferable. Intravenous injection administration is the most preferable.

[0047] For the parenteral administration, forms of killing cancer tissue by the .sup.10B drug of the present invention include aqueous or non-aqueous sterile solutions, suspensions, emulsions, and the like. Examples of non-aqueous solvents which may be included include propylene glycol, polyethylene glycol, vegetable oils (e.g., olive oil), injectable organic esters (e.g., ethyl oleate), and the like. Aqueous carriers which may be included include water, alcoholic/aqueous solutions, emulsions or suspensions (including saline, and buffering media). Parenteral vehicles include sodium chloride solutions, Ringer's dextrose, dextrose and sodium chloride, lactated Ringer, or fixed oils. Intravenous vehicles include fluids and nutritional supplements, electrolyte supplements (e.g., those based on Ringer's dextrose), and the like. Preservatives and other additives may also be present, such as, for example, antimicrobial substances, antioxidants, chelating agents, and inert gases, and the like. For oral administration, the form of the .sup.10B drug of the present invention include powder or granules, suspensions or solutions in water or non-aqueous media, capsules, sachets, or tablets, and the .sup.10B drug of the present invention may include thickeners, flavors, diluents, emulsifiers, dispersing aids or binders.

<Compound Containing .SUP.10.B and Peptide Capable of Selectively Binding to Tumor Vascular Endothelial Cell>

[0048] In the compound, it is preferable that an amino acid residue (preferably a side chain of the amino acid residue) at any position in the peptide capable of selectively binding to a tumor vascular endothelial cell binds to .sup.10B directly or via a linker. As the bond, any bond may be used, such as a covalent bond, an ionic bond, a coordination bond, or a bond due to an intermolecular force, but a covalent bond is preferred because of stability of the bond.

(.SUP.10.B)

[0049] The compound preferably contains a .sup.10B-containing group. It is more preferable that an amino acid residue at any position of the peptide capable of selectively binding to a tumor vascular endothelial cell (preferably a side chain of the amino acid residue) binds directly or via a linker to the .sup.10B-containing group. The .sup.10B-containing group may be .sup.10B itself, and examples thereof include a [10B]boronophenylalanine group represented by formula (a) below, a [10B]borocaptate group represented by formula (b) below, etc. From the viewpoint of imaging distribution of the anticancer drug of the present invention in the body by positron emission tomography (PET), the .sup.10B-containing group may be an [18F]fluoro[10B]boronophenylalanine group (represented by, for example, formula (c) below), which is radiolabeled with .sup.18F.

##STR00003##

in which * represents a bond.

[0050] With respect to the embodiment in which a .sup.10B-containing group and an amino acid residue at any position in the peptide capable of selectively binding to a tumor vascular endothelial cell are directly bound to each other, the following (1) to (5) can be exemplified but the embodiment of the present invention is not limited thereto. The [10B]boronophenylalanine group represented by the formula (a) or the [18F]fluoro[10B]boronophenylalanine group represented by the formula (c) binds to the peptide through:

(1) an amide bond with a lysine residue which may exist at any position in the peptide and which has an amino group in the side chain;
(2) a thioester bond with a cysteine residue which may exist at any position in the peptide and which has a thiol group in the side chain;
(3) an ester bond with a serine residue or a threonine residue which may exist at any position in the peptide and which has a hydroxy group in the side chain;
(4) a disulfide bond between the [10B]borocaptate group represented by the formula (b) and a cysteine residue which may exist at any position and which has a thiol group in the side chain;
(5) a thioester bond between the [10B]borocaptate group represented by the formula (b) and an aspartic acid residue or a glutamic acid residue which may exist at any position in the peptide and which has a carboxy group in the side chain; and the like. The amide bond, the thioester bond, the ester bond, and the disulfide bond can be formed by any organic chemical method.

(Peptide Capable of Selectively Binding to Tumor Vascular Endothelial Cell)

[0051] The peptide capable of selectively binding to a tumor vascular endothelial cell is not particularly limited, as long as it can selectively bind to a tumor vascular endothelial cell. However, a peptide capable of selectively binding to annexin 1 is preferable. Annexin 1 has been identified as a specific tumor endothelial cell surface marker and is known to be specifically expressed in tumor vascular endothelial cells (Oh, P. et al. Nature 2004; 429: pp. 629-635). The present invention relates to an anticancer drug comprising a compound comprising a .sup.10B-containing group and a peptide capable of selectively binding to annexin 1, in which the .sup.10B-containing group is an L-p-[10B]boronophenylalanine group or a [10B]borocaptate group.

[0052] Examples of the peptide capable of selectively binding to annexin 1 include a peptide which comprises an amino acid sequence of IFLLWQR, which has 7 to 15 amino acids (preferably 7 to 13 amino acid residues, more preferably 7 to 12 amino acid residues, and most more preferably 8 to 11 amino acid residues), and in which one or two amino acids of IFLLWQR may be substituted by any amino acid. More specifically, examples of the peptide capable of selectively binding to annexin 1 include an amino acid sequence of IFLLWQR (amino acids 1 to 7 of SEQ ID NO: 1), an amino acid sequence of IFLLWQRX (amino acids 1 to 8 of SEQ ID NO: 1), an amino acid sequence of IFLLWQRXX (amino acids 1 to 9 of SEQ ID NO: 1), an amino acid sequence of IFLLWQRXXX (amino acids 1 to 10 of SEQ ID NO: 1), an amino acid sequence of IFLLWQRXXXX (amino acids 1 to 11 of SEQ ID NO: 1), or an amino acid sequence of IFLLWQRXXXXX (amino acids 1 to 12 of SEQ ID NO: 1), in which each X independently represents a polar or charged amino acid, and in which one or two amino acids of IFLLWQR in each of the amino acid sequences may be substituted.

[0053] For example, each X may be independently selected from any set consisting of five amino acids of the amino acids C, R, K, S, T, H, D, E, N, Q, and M, any set consisting of four amino acids of all the amino acids, any set consisting of three amino acids of all the amino acids, any set consisting of two amino acids of all the amino acids, or any one of all the amino acids. For example, each X may be independently selected from a set consisting of three amino acids C, R, and K. Examples of the peptide capable of selectively binding to annexin 1 include IFLLWQRCRR (SEQ ID NO: 2), IFLLWQRKRR (SEQ ID NO: 3), IFLLWQRCR (SEQ ID NO: 4), IFLLWQRCRRRR (SEQ ID NO: 5), and the like.

[0054] The peptide may be bound directly or via a linker to .sup.10B (preferably a .sup.10B-containing group) at any amino acid residue of the peptide. As the binding position, a position between the sixth and twelfth amino acid residues (preferably, a side chain of the amino acid residue) in the respective amino acid sequences can be exemplified. A position between the seventh and eleventh amino acid residues is preferred, a position between the eighth and tenth amino acid residues is more preferred, and a position at the eighth or ninth amino acid residue is the most preferred.

[0055] The peptides may have a variety of modifications. The modifications may be used to alter or improve the properties of the peptide. For example, peptides disclosed may be those in which one or more amino acids are N-methylated, O-methylated, S-methylated, or C-methylated, or a combination thereof.

[0056] The amino and/or carboxy terminals of the peptide may be modified. Amino terminal modification includes methylation (e.g., NHCH.sub.3 or N(CH.sub.3).sub.2), acetylation (for example, by using acetic acid or a halogenated derivative thereof (e.g., α-chloroacetic acid, α-bromoacetic acid, or α-iodoacetic acid)), addition of a benzyloxycarbonyl (Cbz) group, or blocking an amino terminus with any blocking group including a carboxylate functionality defined by RCOO— or a sulfonyl functionality defined by R—SO.sub.2— (where R is selected from the group consisting of alkyl, aryl, heteroaryl, alkylaryl, etc.), and with a similar group. A person skilled in the art may also make the peptide incorporate a des-amino acid at the N-terminus (so that there is no N-terminal amino group) to reduce sensitivity to proteases or to restrict the conformation of the peptide compound. In a preferred embodiment, the N-terminus is acetylated with acetic acid or acetic anhydride.

[0057] Modification of the carboxy terminus includes a step of replacing a free acid with a carboxamide group, or a step of forming a cyclic lactam at the carboxy terminus to introduce structural restraint. A person skilled in the art may also cyclize the peptide disclosed or incorporate a desamino or descarboxy residue at the terminus of the peptide disclosed so that no terminal amino or carboxyl group exists to reduce sensitivity to proteases or restrict the conformation of the peptide. Examples of functional groups at the C-terminus of the peptide disclosed include amides, lower alkyl amides (amide lower alkyl), di (lower alkyl) amides (amide di(lower alkyl)), lower alkoxy, hydroxy, carboxy, and lower ester derivatives thereof, as well as pharmaceutically acceptable salts thereof.

[0058] A person skilled in the art can replace a naturally occurring side chain of a genetically encoded amino acid (or a D amino acid as a stereoisomer) with another side chain, for example, with a group (e.g., an alkyl group, a lower (C.sub.1 to 6) alkyl group, a cyclic four-membered, five-membered, six-membered, or seven-membered alkyl group, an amide group, a lower alkylamide group, a di(lower alkyl) amide group, a lower alkoxy group, a hydroxy group, or a carboxy group as well as a lower ester derivative thereof), and with a four-membered, five-membered, six-membered, or seven-membered heterocyclic group. In particular, a proline analog in which the ring size of the proline residue is changed from five members to four, six, or seven members may be used. The cyclic group may be saturated or unsaturated, and when the cyclic group is unsaturated, it may be aromatic or non-aromatic. The heterocyclic group preferably comprises one or more nitrogen, oxygen, and/or sulfur heteroatoms. Examples of such a group include furazanyl, furyl, imidazolidinyl, imidazolyl, imidazolinyl, isothiazolyl, isoxazolyl, morpholinyl (e.g., morpholino), oxazolyl, piperazinyl (e.g., 1-piperazinyl), piperidyl (e.g., 1-piperidyl, piperidino), pyranyl, pyrazinyl, pyrazolidinyl, pyrazolinyl, pyrazolyl, pyridazinyl, pyridyl, pyrimidinyl, pyrrolidinyl (e.g., 1-pyrrolidinyl), pyrrolinyl, pyrrolyl, thiadiazolyl, thiazolyl, thienyl, thiomorpholinyl (e.g., thiomorpholino), and

triazolyl. These heterocyclic groups may be substituted or unsubstituted. When a group is substituted, the substituent can be alkyl, alkoxy, halogen, oxygen, or substituted or unsubstituted phenyl.

[0059] A person skilled in the art can also readily modify the peptide by phosphorylation and other methods [as described, for example, in Hruby, et al. (1990) Biochem J., 268: pp. 249-262].

(Linker)

[0060] Binding between the amino acid residue (preferably the side chain of the amino acid residue) at any position of the peptide capable of selectively binding to a tumor vascular endothelial cell and .sup.10B (preferably a .sup.10B-containing group) may be via a linker as described above. Examples of the linker include a linker having 1 to 20 carbon atoms (preferably 2 to 15 carbon atoms, more preferably 3 to 10 carbon atoms) which may or may not contain a keto group, an ether bond, a thioether bond, an amide bond, a divalent succinimide group and/or a divalent maleimide group.

[0061] Firstly, examples of the bond between the .sup.10B-containing group and the linker include the following examples (6) to (9), but the present invention is not limited thereto:

(6) an amide bond formed of the [10B]boronophenylalanine group represented by the formula (a) or the [18F]fluoro[10B]boronophenylalanine group represented by the formula (c) and an amino group of any linker;
(7) an ester bond formed of the [10B]boronophenylalanine group represented by the formula (a) or the [18F]fluoro[10B]boronophenylalanine group represented by the formula (c) and a hydroxy group of any linker; and
(8) a thioether bond formed of the [10B]boronocaptate group represented by the formula (b) and a maleimide group of any linker.

[0062] (9) An amino group can be introduced into the terminus of the [10B]boronophenylalanine group represented by the formula (a) or the [18F]fluoro[10B]boronophenylalanine group represented by the formula (c) by forming an ester bond using the [10B]boronophenylalanine group represented by the formula (a) or the [18F]fluoro[10B]boronophenylalanine group represented by the formula (c) and any aminoalkyl alcohol (preferably an aminoalkyl alcohol with one to five carbon atoms). Subsequently, any linker having an N-hydroxysuccinimide-activated ester group can be reacted with the [10B]boronophenylalanine group represented by the formula (a) in which an amino group has been introduced at the terminus or the [18F]fluoro[10B]boronophenylalanine group represented by the formula (c) in which an amino group has been introduced at the terminus to bind the linker and the [10B]boronophenylalanine group or the [18F]fluoro[10B]boronophenylalanine group via an amide bond. The amide bond, the thioether bond, the thioester bond, the ester bond, and the disulfide bond can be formed by any organic chemical method.

[0063] Subsequently, examples of the bond between an amino acid residue at any position of the peptide capable of selectively binding to a tumor vascular endothelial cell and the linker include the following (11) to (14):

(11) an amide bond between an N-hydroxysuccinimide activated ester group of any linker and a lysine residue which may exist in any position of the peptide and which has an amino group in the side chain;
(12) a thioether bond between a maleimide group of any linker and a cysteine residue which may exist in any position of the peptide and which has a thiol group in the side chain;
(13) a thioester bond between an N-hydroxysuccinimide activated ester group of any linker and a cysteine residue which may exist in any position of the peptide and which has a thiol group in the side chain; and
(14) an ester bond between an N-hydroxysuccinimide activated ester group of any linker and a serine residue or a threonine residue which may exist at any position of the peptide and which has a hydroxy group in the side chain. The amide bond, the thioether bond, the thioester bond, and the ester bond can be formed by any organic chemical method.

[0064] Examples of preferred linkers that link .sup.10B (preferably a .sup.10B-containing group) to an amino acid residue at any position (preferably the side chain of the amino acid residue) of the peptide capable of selectively binding to a tumor vascular endothelial cell include linkers represented by the following formula (i) or (ii):

##STR00004##

wherein * and ** each represent a bond, and the present invention is, however, not limited thereto.

[0065] It is preferable that the bond * in the formulas (i) and (ii) forms a thioether bond with a cysteine residue at any position of the peptide, or a thioether bond with a [10B]borocaptate group represented by the formula (b). It is preferable that the bond ** in the formulas (i) and (ii) forms an amide bond with a lysine residue at any position of the peptide, or an ester bond with a [10B]boronophenylalanine group represented by the formula (a) or an [18F]fluoro[10B]boronophenylalanine group represented by the formula (c). It is also preferable that the bond ** in the formulas (i) and (ii) forms a thioester bond with a cysteine residue at any position of the peptide, or a thioester bond with a [10B]borocaptate group represented by the formula (b).

[0066] In actively growing cancer cells, metabolism of phenylalanine is enhanced, and phenylalanine cannot be synthesized in the cells. Therefore, it is known that cancer cells take up and utilize a large amount of phenylalanine in the blood. Therefore, phenylalanine compounds derived from the [10B]boronophenylalanine group represented by the formula (a) or [18F]fluoro[10B]boronophenylalanine group (for example, the formula (c)), etc. (by liberation, etc.) can also be taken up in a large quantity by cancer cells. Therefore, it is preferable that a phenylalanine compound is liberated from the compound by the action of an esterase, etc., which generally exists in cells, so that the phenylalanine compound can move to the cell nucleus where a greater cancer cell-killing effect is expected. From this viewpoint, it is preferable that the [10B]boronophenylalanine group represented by the formula (a) or an [18F]fluoro[10B]boronophenylalanine group (e.g., formula (c)) binds to a linker via an ester bond, or the [10B]boronophenylalanine group represented by the formula (a) or the [18F]fluoro[10B]boronophenylalanine group (e.g., formula (c)) binds to a peptide capable of selectively binding to a tumor vascular endothelial cell via a linker including an ester bond. It is more preferable that the [10B]boronophenylalanine group represented by formula (a) or the [18F]fluoro[10B]boronophenylalanine group (e.g., formula (c)) is bound by the bond ** in the formula (i) to the peptide capable of selectively binding to a tumor vascular endothelial cell via the linker represented by the formula (i).

[0067] On the other hand, the [10B]borocaptate compound (e.g., a dissociated product or separated product of [10B]borocaptate group represented by the formula (b)) has 12 .sup.10B per molecule of the [10B]borocaptate compound and is expected to have a large cancer cell-killing effect by BNCT. Meanwhile, the [10B]borocaptate compound per se is generally difficult to be taken up by cells and is known to remain around cancer cells. Thus, in the case of the [10B]borocaptate group in which the .sup.10B-containing group is represented by the formula (b), it is preferable that the peptide capable of selectively binding to a tumor vascular endothelial cell and the [10B]borocaptate group represented by the formula (b) are linked via a linker that is not easily cleaved by the action of esterase, etc., which is generally present in cells, (preferably, a linker that does not contain an ester bond). It is more preferable that the [10B]borocaptate group represented by the formula (b) is bound by the bond * in the formula (ii) and thereby the [10B]borocaptate group binds to the peptide capable of selectively binding to a tumor vascular endothelial cell via the linker represented by the formula (ii).

[0068] Preferred examples of the compound containing .sup.10B and a peptide capable of selectively binding to a tumor vascular endothelial cell in the present invention include a compound containing a structure represented by the following formula (i-1) or (ii-1) but are not limited thereto in the present invention.

##STR00005##

In which * and ** each represent a bonding site with the peptide capable of selectively binding to a tumor vascular endothelial cell. More preferred examples of the compound containing .sup.10B and a peptide capable of selectively binding to a tumor vascular endothelial cell in the present invention include a compound represented by the following formula (1) or (2), but are not limited thereto in the present invention.

##STR00006##

<Other Components>

[0069] The .sup.10B drug of the present invention may or may not include a pharmaceutically acceptable carrier. The term “pharmaceutically acceptable” means that a material is not a biologically non-desired material nor another non-desired material. That is, the material may be administered to a subject together with the anticancer drug described above without causing any undesired biological action or without interacting in a harmful manner with any of the other components of the anticancer drug described above in which the material is contained. The carrier is, of course, selected as is well known to those skilled in the art to minimize any degradation of an active ingredient (the compound described above) and to minimize any adverse side effects in the subject described above. The materials may be present in a solution or a suspension (e.g., incorporated into microparticles, liposomes, or cells).

[0070] Suitable carriers include those described in Remington: The Science and Practice of Pharmacy (19.sup.th ed.) ed. A. R. Gennaro, Mack Publishing Company, Easton, Pa. 1995. Typically, a suitable amount of a pharmaceutically acceptable salt is used in the anticancer drug to render the anticancer drug isotonic. Examples of the pharmaceutically acceptable carriers include, but are not limited to, saline, Ringer's solution, and a dextrose solution. The pH of the solution is preferably from about 5 to about 8, and more preferably from about 7 to about 7.5. Further carriers include sustained release preparations (e.g., a semipermeable matrix of a solid hydrophobic polymer comprising an antibody, wherein the matrix is in the form of a molded article (e.g., a film, a liposome, or microparticles). It will be apparent to those skilled in the art that certain carriers may be more preferred, e.g., depending on the route of administration and the concentration of the composition to be administered.

[0071] Pharmaceutical carriers are known to those skilled in the art. These are most typically standard carriers for the administration of drugs to humans, including solutions (e.g., sterile water, saline, and buffered solutions of physiological pH).

[0072] In addition to the compounds generally preferred above, the .sup.10B drug of the present invention may include carriers, thickeners, diluents, buffers, preservatives, and surfactants, and the like.

<Use>

[0073] The anticancer drug of the present invention is suitable for BNCT because it can selectively accumulate rapidly in tumor tissue at a low dosage amount, in a high concentration. Irradiation with neutrons in BNCT is preferably performed within 60 minutes after the administration, more preferably within 40 minutes after the administration, more preferably within 30 minutes after the administration, and most preferably within 20 minutes after the administration. Although the lower limit value of the start of neutron irradiation is not particularly limited, the starting time is 5 minutes after the administration, and preferably 10 minutes after the administration. Although the irradiation dose (flux) of neutrons is not particularly limited, experiments are carried out in the range of 2×10.sup.6/cm.sup.2.Math.s or more (preferably 1×10.sup.7/cm.sup.2.Math.s or more, more preferably 1×10.sup.8/cm.sup.2.Math.s or more, more preferably 1×10.sup.9/cm.sup.2.Math.s or more, more preferably 1×10.sup.10/cm.sup.2.Math.s or more, more preferably 1×10.sup.11/cm.sup.2.Math.s or more, and most preferably 1×10.sup.12/cm.sup.2.Math.s or more). From the viewpoint of PGA measurement sensitivity, flux equal to or higher than this improves the resolution. Therefore, although the upper limit of flux is not particularly limited, for example, 1×10.sup.13/cm.sup.2.Math.s or less can be mentioned. 8×10.sup.12/cm.sup.2.Math.s or less is preferable, 6×10.sup.12/cm.sup.2.Math.s or less is more preferable, and 5×10.sup.12/cm.sup.2.Math.s or less is the most preferable.

[0074] Although physical dose of neutrons is not particularly limited, for example, a range of 5E.sup.−1 Gy or more can be mentioned as a total of thermal neutrons, epithermal neutrons, fast neutrons, and gamma rays. Although the upper limit of the physical dose is not particularly limited, for example, 5 Gy or less can be mentioned as the total.

<Target>

[0075] Although cancers to which the present .sup.10B drug may be applied are not particularly limited, examples thereof include: lymphomas (Hodgkin and non-Hodgkin), carcinomas, carcinomas of solid tissue, squamous epithelium carcinomas, adenocarcinomas, sarcomas, gliomas, high grade glioma, blastomas, neuroblastomas, plasmacytomas, histiocytomas, melanomas, adenomas, hypoxic tumors, myelomas, AIDS related lymphomas or sarcomas, metastatic cancers, and cancers in general.

[0076] More specifically, the following can be mentioned: lymphoma, B-cell lymphoma, T-cell lymphoma, mycosis fungoides, Hodgkin's disease, myelogenic leukemia, bladder cancer, brain cancer, nervous system cancer, head and neck cancer, squamous epithelium carcinomas in the head and neck, kidney cancer, lung cancer (e.g., small cell lung cancer and non-small cell lung cancer), neuroblastoma/glioblastoma, ovarian cancer, pancreatic cancer, prostate cancer, skin cancer, liver cancer, melanoma, squamous epithelium carcinomas in the mouth, throat, larynx, and lung, colon cancer, cervical cancer, cervical carcinoma, breast cancer, epithelial cancer, kidney cancer, urinary and genital organ cancer, pulmonary cancer, esophagus cancer, gastric cancer, head and neck cancer, colon cancer, hematopoietic cancer, testicular cancer, colon and rectal cancer, or pancreatic cancer, etc.

EXAMPLES

[0077] Below, the present invention is described in more detail with reference to the Examples, but the scope of the present invention is not limited to these Examples.

Synthetic Example 1

[0078] ##STR00007##

[0079] The peptide represented by the amino acid sequence IFLLWQRCRR (SEQ ID NO: 2) was chemically synthesized using a 9-fluorenylmethoxycarbonyl method (Fmoc method). 2,000 mg of the peptide obtained and 3,000 mg of the compound represented by the above formula were mixed, and N-(6-maleimidecaproyloxy)succinimide (EMCS) was added dropwise to crosslink between a thiol group of cysteine of the peptide and a terminal amino group of the compound represented by the formula with the EMCS to obtain 420 mg of a compound represented by the following formula (1) (hereinafter, simply referred to as “IF7-.sup.10BPA”).

##STR00008##

Synthesis Example 2

[0080] The peptide represented by the amino acid sequence IFLLWQRKRR (SEQ ID NO: 3) was chemically synthesized using tert-butoxycarbonyl method (Boc method). 2,000 mg of the peptide obtained and 3,000 mg of sodium [10B]borocaptate were mixed, and N-(6-maleimidocaproyloxy)succinimide (EMCS) was added dropwise to crosslink between an amino group of lysine of the peptide and a thiol group of the sodium [10B]borocaptate with the EMCS to obtain 415 mg of a compound represented by the following formula (2) (hereinafter, simply referred to as “IF7-.sup.10BSH”).

##STR00009##

[Tumor Accumulation Ability Test]

Examples 1 and 2

[0081] Tumor accumulation ability was tested in tumor-bearing mice (7 mm in tumor diameter) seeded on the thigh with a murine bladder cancer cell MBT2, with respect to IF7-.sup.10BPA synthesized in Synthesis Example 1 above and IF7-.sup.10BSH synthesized in Synthesis Example 2 above. 100 μL (175 μg) of IF7-.sup.10BPA or IF7-.sup.10BSH adjusted to 7 mg/kg was administered to the tail vein of the tumor-bearing mice. .sup.10B levels (ppm) in the organs of the tumor-bearing mice were measured 5, 10, and 20 minutes after the tail-vein administration by the PGA-method.

[0082] FIGS. 1A and 1B are drawings indicating .sup.10B levels (ppm) in the organs of the tumor-bearing mice 5, 10, and 20 minutes after tail-vein administration of 100 μL (175 μg) of the IF7-.sup.10BPA and IF7-.sup.10BSH, respectively. As is clear from the results shown in FIGS. 1A and 1B, it can be seen that for both IF7-.sup.10BPA and IF7-.sup.10BSH, .sup.10B levels were less than 20 ppm in the brain, lung, heart, liver, kidney, bladder, stomach, intestine, spleen, skin, muscles, and blood 20 minutes after the administration, whereas .sup.10B specifically accumulated in the tumor tissue of the tumor-bearing mice at a level of at least 25 ppm, 20 minutes after the administration. Thus, both IF7-1BPA and IF7-.sup.10BSH could selectively accumulate in tumor tissue at a low dosage amount (7 mg/kg) rapidly (20 min) at a high level (Z 25 ppm), indicating that IF7-.sup.10BPA and IF7-.sup.10BSH are suitable as a .sup.10B drug for BNCT.

Comparative Example 1

[0083] Additionally, as Comparative Example 1, a tumor accumulation ability test was similarly performed using R-D-fructopyranose, 2′ position of which is esterified with [10B]boronophenylalanine group represented by the formula (a) (hereinafter, simply referred to as “.sup.10BPA-fructose”). 100 μL (2,000 μg) of .sup.10BPA-fructose whose dosage amount was increased to 100 mg/kg was administered to the tail vein of tumor-bearing mice. .sup.10B levels (ppm) in the respective organs of the tumor-bearing mice were measured 20, 40, and 60 minutes after the tail-vein administration by ICP-AES method. FIG. 2 is a drawing indicating .sup.10B levels (ppm) in the organs of the tumor-bearing mice at 20, 40, and 60 minutes after tail-vein administration of 100 μL (2,000 μg) of .sup.10BPA-fructose. As is clear from the results shown in FIG. 2, .sup.10BPA-fructose did not accumulate at all in the tumor tissue even after 20, 40, and 60 minutes elapsed after the administration. It can be seen that .sup.10BPA-fructose did not significantly discriminate the tumor tissue from the other organs.

Example 3 and Comparative Examples 2 and 3

Example 3

[0084] .sup.10B levels in the respective organs of the tumor-bearing mice were measured in the same manner as in Example 1, except that the measurement was performed 40 minutes after the administration in addition to 5, 10 and 20 minutes, the number of n in the respective data was 3 or more, and the measurement results were indicated in violin plots. The results are indicated in FIG. 3A.

Comparative Example 2

[0085] .sup.10B levels in the respective organs of the tumor-bearing mice were measured in the same manner as in Example 3, except that instead of IF7-.sup.10BPA, [10B]boronophenylalanine (.sup.10BPA) in the same concentration was administered. The results are indicated in violin plots in FIG. 3B.

Comparative Example 3

[0086] .sup.10B levels in the respective organs of the tumor-bearing mice were measured in the same manner as in Comparative Example 2, except that the concentration of .sup.10BPA was changed from 7 mg/kg to 100 mg/kg. The results are indicated in violin plots in FIG. 3C.

(Results)

[0087] As is clear from the results shown in FIGS. 3A to 3C, it can be seen that in Example 3 in which IF7-.sup.10BPA was used, accumulation of .sup.10B in the tumor tends to occur in a shorter time after the administration than in the Comparative Examples 2 and 3 in which .sup.10BPA was used, in particular 20 minutes after the administration. Further, even if compared to Comparative Example 3, in which the concentration of .sup.10BPA was 100 mg/kg, .sup.10B level in the tumor in Example 3 in which IF7-.sup.10BPA was used can be said to be not inferior.

Example 4 and Comparative Example 4

Example 4

[0088] .sup.10B levels in the respective organs of the tumor-bearing mice were measured in the same manner as in Example 2, except that the measurement was performed 40 minutes after the administration in addition to 5, 10, and 20 minutes, the number of n in the respective data was 3 or more, and the measurement results were indicated in violin plots. The results are indicated in FIG. 4A.

Comparative Example 4

[0089] .sup.10B levels in the respective organs of the tumor-bearing mice were measured in the same manner as in Example 4, except that instead of IF7-.sup.10BSH, mercaptoundecahydrododeca [10B]borate (.sup.10BSH) in the same concentration was administered. The results are indicated in FIG. 4B in violin plots.

(Results)

[0090] As is clear from the results shown in FIGS. 4A and 4B, it can be seen that in Example 4 in which IF7-.sup.10BSH was used, accumulation of .sup.10B in the tumor tends to occur 20 minutes to 40 minutes after the administration, in the same or higher levels compared to Comparative Example 4 in which .sup.10BSH was used.

[Neutron Irradiation Test]

Examples 5 and 6

Example 5

[0091] IF7-.sup.10BPA was administered to the tail vein of tumor-bearing mice seeded in the thigh with murine bladder cancer cell strain MBT2 at a dosage amount of 7 mg/kg. Thereafter, tumor volumes (mm.sup.3) thereof were measured for 21 days, with respect to a group (hot group), which was irradiated 40 minutes after the tail-vein administration with neutrons for 30 minutes under the following conditions and a group (cold group), which was not irradiated. The results are indicated in FIG. 5A. In the drawing, * represents p<0.05.

(1) Neutron fluence (cm.sup.−2.Math.s.sup.−1)
2.1E.sup.+12 (2.1×10.sup.12) to 4.6E.sup.+12
(2) Physical dose (Gy)
Thermal neutrons: 2.8E.sup.−1 to 6.1E.sup.−1
Epithermal neutrons: 3.0E.sup.−2 to 6.5E.sup.−2
Fast neutrons: 2.1E.sup.−1 to 4.6E.sup.−1
Gamma rays: 2.1E.sup.−1 to 4.6E.sup.−1
Total: 8.9E.sup.−1 to 1.5E.sup.0

Example 6

[0092] Administration was performed in the same manner as in Example 5, except that IF7-.sup.10BSH was administered instead of IF7-.sup.10BPA. Thereafter, tumor volumes (mm.sup.3) were measured for 21 days with respect to the hot group which was irradiated with neutrons 40 minutes after the administration and the cold group which was not irradiated. Results are indicated in FIG. 5B.

(Results)

[0093] As is clear from the results indicated in FIGS. 5A and 5B, it can be seen that the effect of reducing the tumor volume was pronounced in both the hot groups after the administration of IF7-.sup.10BPA or IF7-.sup.10BSH than in the cold groups after the administration of IF7-.sup.10BPA or IF7-.sup.10BSH.

Example 7 and Comparative Example 5

Example 7

[0094] IF7-.sup.10BPA was administered to tail vein of the tumor-bearing mice seeded with murine bladder cancer cell strain MBT2 at a dosage amount of 7 mg/kg. Thereafter, tumor volumes (mm.sup.3) were measured for 21 days with respect to a hot group which was irradiated with neutrons 40 minutes after the tail-vein administration and a cold group which was not irradiated. Results are indicated in FIG. 6A. As is clear from the results shown in FIG. 6A, it can be seen that the effect of reducing the tumor volume was more pronounced in the hot group after the administration of IF7-.sup.10BPA than in the cold group after the administration of IF7-.sup.10BPA. Further, it can be said that the effect of reducing the tumor volume was greater in the hot group after the administration of IF7-.sup.10BPA in Example 7 than in the hot group after the administration of [10B]boronophenylalanine (.sup.10BPA) in Comparative Example 5.

Comparative Example 5

[0095] The administration was performed in the same manner as in Example 7, except that 1BPA was administered instead of IF7-.sup.10BPA, tumor volumes (mm.sup.3) were measured for 21 days with respect to the hot group irradiated 40 minutes after the administration with neutrons and the cold group which was not irradiated. Results are indicated in FIG. 6B. As is clear from the results indicated in FIG. 6B, though the effect of reducing tumor volumes can be seen in the hot group after the administration of .sup.10BPA, compared to the cold group after the administration of .sup.10BPA, the effect is not as pronounced as in Example 7.

SEQUENCE LISTING

PCT19-001 ST25.txt

[0096]