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 . 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 . 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 . 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 ). 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 . the compound 1 or a salt thereof can be produced by a known method , for example , a method described in japanese patent no . 2761023 . 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 . 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 . 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 ). 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 . 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 . 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 . 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 . 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 . 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 . 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 . 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 . 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 . 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 . t : average tumor weight of a group with administration of the test compound c : average tumor weight of a group without administration of the test compound the results are shown in fig1 . 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 . 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 . the results are presented in fig2 . 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 . 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 . the results are shown in fig3 . 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 .
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 - benzoyl ] amino ] benzoic acid or a salt thereof .