Abstract:
Disclosed is a novel combination therapy of sorafenib having a remarkable antitumor effect. Specifically disclosed is an antitumor agent obtained by combining sorafenib or a salt thereof with 4-[[3,5-bis(trimethylsilyl)benzoyl]amino]benzoic acid or a salt thereof.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a novel antitumor agent containing sorafenib or a salt thereof and 4-[[3,5-bis(trimethylsilyl)benzoyl]amino]benzoic acid or a salt thereof. 
       BACKGROUND ART 
       [0002]    A raf kinase protein, which is a product of oncogene raf, transmits signals of growth factor receptors to the MAP kinase cascade, and through the activation of the kinase cascade, accelerates the proliferation of cancer cells. Insulin-like Growth Factor-II (IGF-II) is a characteristic proliferation factor which is increasingly expressed in many cancer cells including liver cancer, it is known that an increase in the signals of type I IGF receptors, which are the receptors of the foregoing Insulin-like Growth Factor, causes activation of the raf kinase cascade. It is known that a reduction in endogenous raf kinase inhibitor proteins accelerates the onset of cancer. Furthermore, it is reported that increased expression of Vascular Endothelial Growth factor (VEGF), which is a representative angiogenesis factor and is one of the targets for cancer treatment, is correlated with the poor prognosis of liver cancer patients. Therefore, a multikinase inhibitor drug which has both an inhibitory action against raf kinases and an inhibitory action against VEGFR kinases, N-(4-chloro-3-(Trifluoromethyl)phenyl)-N′-(4-(2-(N-methylcarbamoyl)-4-pyridyloxy)phenyl)urea (hereinafter, sorafenib), has been approved as a therapeutic drug for renal cancer and liver cancer (Patent Document 1 and Non-Patent Document 2). 
         [0003]    Furthermore, in order to obtain new antitumor effects, attempts have also been made to use sorafenib or a salt thereof and another antitumor agent such as gemcitabine or doxorubicin in combination (Patent Documents 2 and 3, and Non-Patent Documents 2 and 3). 
         [0004]    However, satisfactory antitumor effects have not been hitherto obtained, and there is a strong demand for a novel combination therapy of sorafenib or a salt thereof exhibiting more potent antitumor effects. 
       PRIOR ART DOCUMENTS 
     Patent Documents 
       [0000]    
       
         Patent Document 1: JP-B-3845792 
         Patent Document 2: JP-A-2005-511658 
         Patent Document 3: WO 2006/125539 
       
     
       Non-Patent Documents 
       [0000]    
       
         Non-Patent Document 1: Nature Reviews Drug Discovery, 2006; 5(10):835-44. 
         Non-Patent Document 2: Annals of Oncology, 2006; 17(5):866-873. 
         Non-Patent Document 3: Clinical Cancer Research, 2006; 12(1):144-51. 
       
     
       SUMMARY OF THE INVENTION 
     Problem to be Solved by the Invention 
       [0011]    The present invention is to provide a novel combination therapy of sorafenib or a salt thereof exhibiting remarkable antitumor effects. 
       Means for Solving the Problem 
       [0012]    Under such circumstances, the inventors of the present invention conducted extensive research on a novel combination therapy of sorafenib or a salt thereof and another antitumor agent, in order to develop a cancer treatment method that further contributes to the prolongation of the survival time of patients. As a result, the inventors found that when 4-[[3,5-bis(trimethylsilyl)benzoyl]amino]benzoic acid (hereinafter, referred to as “compound 1”), which is a RARα-selective agonist compound, is used in combination with sorafenib or a salt thereof, a synergistic antitumor effect is obtained, and this antitumor effect is remarkably excellent as compared with the antitumor effects obtainable by known combination therapies using gemcitabine, doxorubicin or the like. 
         [0013]    The compound 1 is a drug showing a mechanism of action that is different from that of those drugs whose synergistic antitumor effects resulting from a combined use with sorafenib have been previously confirmed. It is quite surprising that a combined use of sorafenib and the compound 1 provides a stronger antitumor effect as compared with the conventional combined use of antitumor agents. 
         [0014]    Specifically, The present invention is related to following items 1) to 6): 
         [0015]    1) An antitumor agent comprising sorafenib or a salt thereof and 4-[[3,5-bis(trimethylsilyl)benzoyl]amino]benzoic acid or a salt thereof in combination. 
         [0016]    2) The antitumor agent according to item 1), which is a combination preparation. 
         [0017]    3) The antitumor agent according to item 1) or 2), which is a kit comprising a preparation containing sorafenib or a salt thereof and a preparation containing 4-[[3,5-bis(trimethylsilyl)benzoyl]amino]benzoic acid or a salt thereof. 
         [0018]    4) Use of a combination of sorafenib or a salt thereof and 4-[[3,5-bis(trimethylsilyl)benzoyl]amino]benzoic acid or a salt thereof, for the preparation of an antitumor agent. 
         [0019]    5) A method for treating cancer, the method comprising administering to a patient a combination of sorafenib or a salt thereof and 4-[[3,5-bis(trimethylsilyl)benzoyl]amino]benzoic acid or a salt thereof. 
         [0020]    6) The method for treating cancer according to item 5), wherein sorafenib or a salt thereof and 4-[[3,5-bis(trimethylsilyl)benzoyl]amino]benzoic acid or a salt thereof are administered simultaneously or separately at an interval. 
       EFFECT OF THE INVENTION 
       [0021]    The antitumor agent of the present invention containing sorafenib or a salt thereof and the compound 1 or a salt thereof provides remarkably high antitumor effects, for example, a decrease in the tumor volume and stagnation of tumor growth, as compared with the conventional combined use of antitumor agents. Therefore, a longer survival time can be obtained by using the antitumor agent of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  is a graph showing the therapeutic effects of a combination therapy of sorafenib and compound 1; 
           [0023]      FIG. 2  is a graph showing the therapeutic effects of a combination therapy of sorafenib and doxorubicin; and 
           [0024]      FIG. 3  is a graph showing the therapeutic effects of a combination therapy of sorafenib and gemcitabine. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    Sorafenib of the present invention is a known compound represented by N-(4-chloro-3-(trifluoromethyl)phenyl)-N′-(4-(2-(N-methylcarbamoyl)-4-pyridyloxy)phenyl)urea, and is known to provide antitumor effects against cancers such as liver cancer and renal cancer according to inhibition of Raf kinases or VEGFR kinases. 
         [0026]    The salt of sorafenib is not limited as long as the salt is a pharmaceutically acceptable salt, and examples thereof include salts of inorganic acids and organic acids such as hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid, methanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, 1-naphthalenesulfonic acid, 2-naphthalenesulfonic acid, acetic acid, trifluoroacetic acid, malic acid, tartaric acid, citric acid, lactic acid, oxalic acid, succinic acid, fumaric acid, maleic acid, benzoic acid, salicylic acid, phenylacetic acid and mandelic acid, while a salt of p-toluenesulfonic acid is preferred. 
         [0027]    Sorafenib or a salt thereof can be produced by a known method, for example, a method described in Japanese Patent No. 3845792, and commercially available medicines such as Nexavar (registered trademark, manufactured by Bayer Pharmaceuticals Corp.) may also be used. 
         [0028]    Compound 1 of the present invention is a known RARα-selective agonist compound represented by 4-[[3,5-bis(trimethylsilyl)benzoyl]amino]benzoic acid, and is known to provide antitumor effects against numerous types of cancer such as liver cancer and lung cancer (J. Clin. Oncol. 2002, 20(16), 3522-3532; Japanese Patent No. 2761023). 
         [0029]    The salt of the compound 1 is not particulary limited as long as the salt is a pharmaceutically acceptable salt, and examples thereof include salts of metals such as sodium, potassium and calcium; ammonium salts; and salts of organic acids such as methylamine, ethylamine, trimethylamine, triethylamine, pyridine, picoline, arginine and lysine. 
         [0030]    The compound 1 or a salt thereof can be produced by a known method, for example, a method described in Japanese Patent No. 2761023. 
         [0031]    As will be shown in the Examples that are described below, when sorafenib or a salt thereof and the compound 1 or a salt thereof are administered in combination, the agents exhibit a remarkably strong antitumor effect compared with the case where the agents are administered individually. Therefore, a preparation containing sorafenib or a salt thereof and the compound 1 or a salt thereof as active ingredients, is useful as an antitumor agent. 
         [0032]    There are no particular limitations on the cancer that can be treated by the antitumor agent of the present invention, and examples of the cancer include liver cancer, renal cancer, head and neck cancer, esophagus cancer, stomach cancer, colon cancer, rectum cancer, liver cancer, gall bladder/biliary duct cancer, pancreas cancer, lung cancer, breast cancer, ovary cancer, cervical cancer, uterine cancer, renal cancer, urinary bladder cancer, prostate cancer, testicular cancer, osteo/chondrosarcoma, leukemia, malignant lymphoma, multiple myeloma, skin cancer, brain tumor, and mesothelioma. Preferred examples include liver cancer, renal cancer and lung cancer. 
         [0033]    The antitumor agent of the present invention may be prepared as a combination preparation, by formulating the sorafenib or a salt thereof and the compound 1 or a salt thereof in their respective effective amounts, into a single preparation at an appropriate mixing ratio (single preparation form), or may be prepared by formulating individual preparations respectively containing the respective ingredients in their respective effective amounts, so that the preparations can be used simultaneously or separately at an interval (two-preparation form). 
         [0034]    The dosage form of the preparation is not particulary limited, and the dosage form can be optionally selected according to the purpose of treatment. Specific examples include oral preparations (tablets, coated tablets, powders, granules, capsules, liquids, and the like), injectable preparations, suppositories, patches, and ointments. The dosage form of Sorafenib or a salt thereof and the compound 1 or a salt thereof may be different or the same. 
         [0035]    A preparation containing sorafenib or a salt thereof and/or the compound 1 or a salt thereof according to the present invention, can be prepared by a conventionally known method using a pharmaceutically acceptable carrier. Examples of such a carrier include various carriers that are generally used in conventional drugs, such as an excipient, a binder, a disintegrant, a gliding agent, a diluent, a dissolution aid, a suspending agent, an isotonic agent, a pH adjusting agent, a buffering agent, a stabilizer, a colorant, a flavoring agent, and an odor improving agent. 
         [0036]    Examples of the excipient include lactose, sucrose, sodium chloride, glucose, maltose, mannitol, erythritol, xylytol, maltitol, inositol, dextran, sorbitol, albumin, urea, starch, calcium carbonate, kaolin, crystalline cellulose, silicic acid, methylcellulose, glycerin, sodium alginate, gum arabic and mixtures thereof. Examples of the gliding agent include purified talc, stearic acid salts, borax, polyethylene glycol and mixtures thereof. Examples of the binder include simple syrup, glucose liquid, starch liquid, gelatin solution, polyvinyl alcohol, polyvinyl ether, polyvinylpyrrolidone, carboxymethyl cellulose, shellac, methyl cellulose, ethyl cellulose, water, ethanol, potassium phosphate and mixtures thereof. Examples of the disintegrant include dried starch, sodium alginate, agar powder, laminaran powder, sodium hydrogen carbonate, calcium carbonate, polyoxyethylene sorbitan fatty acid esters, sodium lauryl sulfate, stearic acid monoglyceride, starch, lactose and mixtures thereof. Examples of the diluent include water, ethyl alcohol, macrogol, propylene glycol, ethoxylated isostearyl alcohol, polyoxylated isostearyl alcohol, polyoxyethylene sorbitan fatty acid esters and mixtures thereof. Examples of the stabilizer include sodium pyrosulfite, ethylenediamine tetraacetic acid, thioglycolic acid, thiolactic acid and mixtures thereof. Examples of the isotonic agent include sodium chloride, boric acid, glucose, glycerin and mixtures thereof. Examples of the pH adjusting agent and buffering agent include sodium citrate, citric acid, sodium acetate, sodium phosphate and mixtures thereof. Examples of a soothing agent include procaine hydrochloride, lidocaine hydrochloride and mixtures thereof. 
         [0037]    Furthermore, the amount of sorafenib or a salt thereof and the compound 1 or a salt thereof in the preparation is preferably such that the amount of sorafenib or a salt thereof in the preparation is generally 1 to 1000 mg in terms of sorafenib, and the amount of the compound 1 or a salt thereof is 0.001 to 1000 mg. 
         [0038]    When the antitumor agent of the present invention is provided as a kit, the kit can be designed such that the preparations containing sorafenib or a salt thereof and the compound 1 or a salt thereof formulated as described above, are separately packaged, and the medicine preparations are taken out from the respective packages and used at the time of administration. Furthermore, the respective medicine preparations may also be packaged in a form appropriate for combined administration for each dose. 
         [0039]    The dosage amount of sorafenib or a salt thereof and the compound 1 or a salt thereof according to the present invention is not particulary limited, as long as it is an amount that allows sorafenib or a salt thereof and the compound 1 or a salt thereof to exhibit an antitumor effect in a synergistic manner and to effectively treat cancer. The amount of administration is appropriately adjusted in accordance with the age of the patient, type of cancer, stage of disease, presence or absence of metastasis, background of treatment, presence or absence of other antitumor agents, and the like. The dosage amount of sorafenib or a salt thereof is, for example, about 1 to 5000 mg/day in terms of sorafenib, and the dosage amount of the compound 1 or a salt thereof is about 0.05 to 5000 mg/day. A preferred dosage amount of sorafenib or a salt thereof is about 50 to 2000 mg/day in terms of sorafenib, and a preferred dosage amount of the compound 1 or a salt thereof is about 0.1 to 1000 mg/day. 
         [0040]    The order of administration or interval length of administration of sorafenib or salt thereof and the compound 1 or a salt thereof according to the present invention is not particulary limited, as long as the order of administration or the interval of administration is in the range in which a synergistic effect can be obtained. Furthermore, in the case of using the agents as a kit, the respective individual preparations may be administered simultaneously or separately at an interval. 
       EXAMPLES 
       [0041]    Hereinafter, the present invention will be described in more detail by way of Pharmacological Test Examples and Comparative Examples. However, these Examples should not be construded to limit the scope of the subject invention. 
         [0042]    As the solvent for the administration of various drugs in the following Test Examples, 0.5% hydroxypropylmethyl cellulose (Shin-Etsu Chemical Co., Ltd.) was used for the compound 1, and a mixed liquid of 2.5% of dimethyl acetamide (Wako Pure Chemical Industries, Ltd.), 7.5% of Cremophor (Nacalai Tesque, Inc.) and 90% of 0.1 N hydrochloric acid (Wako Pure Chemical Industries, Ltd.) was used for sorafenib. A set of one-week doses of the compound 1 was prepared and was stored in refrigeration in the dark. Sorafenib was weighed at every time of use, and a liquid for administration was prepared. Furthermore, human liver cancer cells JHH-7 which exhibited high expression of IGF-II and RARα were subcultured and maintained in a CO 2  incubator using ASF medium 104 (Ajinomoto Co., Inc.). BALE/cA Jcl-nu male nude mice (Clea Japan, Inc.) were used as the efficacy test animals. 
       Pharmacological Test Example 1 
     Combination Treatment Effect of Sorafenib and Compound 1 
       [0043]    Human liver cancer cell line JHH-7 composed of cells exhibiting high expression of RARα, was transplanted in an amount of 1×10 6  cells (0.02 mL) for each animal, into the left lateral liver lobe of a male nude mouse which was under nembutal anesthesia. On the 11 th  day after the transplantation, α-fetoprotein (AFP) in the blood was quantified (Diagnostic Automation, Inc., Cat. No.: 5106-16) as an index of tumor implantation, and the animals were grouped by stratified random allocation into seven animals per group so as to make the average AFP value uniform. The compound 1 and sorafenib were orally administered once a day for 14 consecutive days. The compound 1 was administered in an amount of 2 mg/kg, which is the minimum non-toxic dose allowing verification of the effectiveness in mouse. Sorafenib was administered in an amount of 10 mg/kg, which reaches a blood concentration close to that obtainable by administration of 400 mg, which is the clinical maximum dose. On the 15 th  day after the initiation of administration, the mice were killed by bleeding under ether anesthesia, subsequently tumors formed in the left lateral liver lobe were extracted, and the weight of the tumors was measured. The tumor growth rate (%) was calculated by the formula shown below, and the T/C value of each of the drug administered groups was calculated, while the average tumor weight of the non-drug administered control group was taken as 100%. This T/C value was used as an index of the antitumor effect. The statistical significance of the single drug administered groups was determined by Welch&#39;s two-tailed test, and the statistical significance of the effect synergizing action obtained by combined use was determined by the intersection union test based on Welch&#39;s two-tailed test. 
         [0000]      Tumor growth rate (%)= T/C× 100 
         [0044]    T: Average tumor weight of a group with administration of the test compound 
         [0045]    C: Average tumor weight of a group without administration of the test compound 
         [0046]    The results are shown in  FIG. 1 . The T/C values of the sorafenib single drug administered group and the compound 1 single drug administered group were 65% and 51%, respectively, and thus a significant therapeutic effect, as compared with the control group, was confirmed. On the other hand, the T/C value of the sorafenib and compound 1 combination group was 22%. The therapeutic effect of the combination group was statistically significant even when compared with the respective single drug administered groups, and an obvious synergism of activity was confirmed. In addition, it was also confirmed that this combination effect is similar to that of using tosylate salt that is in clinical use. 
       Comparative Example 1 
     Combination Treatment Effect of Sorafenib and Doxorubicin 
       [0047]    In the same manner as in the Pharmacological Test Example 1, human liver cancer cell line JHH-7 was transplanted in an amount of 1×10 6  cells (0.02 mL) for each animal, into the left lateral liver lobe of a male nude mouse which was under nembutal anesthesia. On the 11 th  day after the transplantation, the animals were grouped into seven animals per group, and the treatment experiment was initiated. Doxorubicin was administered such that 10 mg/kg, which is the maximum tolerated dose for a mouse, was administered one time intravenously. Sorafenib was orally administered once a day for 14 consecutive days. On the 15 th  day after the initiation of administration, the mice were killed by bleeding under ether anesthesia, subsequently tumors formed in the left lateral liver lobe were extracted, weighed and evaluated as in the Pharmacological Test Example 1 was made. 
         [0048]    The results are presented in  FIG. 2 . In the present test, the T/C values of the sorafenib single drug administered group and the doxorubicin single drug administered group were 62% and 70%, respectively. On the other hand, even though sorafenib and doxorubicin were used in combination, the T/C value was 65%, and the therapeutic effect was not substantially different from that of the sorafenib single drug administered group. Furthermore, the statistical significance was not found, and an obvious synergism of activity was not recognized. 
       Comparative Example 2 
     Combination Treatment Effect of Sorafenib and Gemcitabine 
       [0049]    In the same manner as in the Pharmacological Test Example 1, human liver cancer cell line JHH-7 was transplanted in an amount of 1×10 6  cells (0.02 mL) for each animal, into the left lateral liver lobe of a male nude mouse which was under nembutal anesthesia. On the 11 th  day after the transplantation, the animals were grouped into seven animals per group, and the treatment experiment was initiated. Gemcitabine was administered such that 120 mg/kg, which is the maximum tolerated dose for a mouse, was administered intraperitoneally four times in total at an interval of 3 days. Sorafenib was orally administered once a day for 14 consecutive days. On the 15 th  day after the initiation of administration, the mice were killed by bleeding under ether anesthesia, subsequently tumors formed in the left lateral liver lobe were extracted, weighed and evaluated as in the Pharmacological Test Example 1 was made. 
         [0050]    The results are shown in  FIG. 3 . In the present test, the T/C values of the sorafenib single drug administered group and the gemcitabine single drug administered group were 60% and 47%, respectively. The T/C value of the sorafenib and gemcitabine combination group was 38%. Similarly to the case of the combination of sorafenib and doxorubicin, an obvious effect synergizing action was not recognized.