HK40005976B - Anti-tumor agent, anti-tumor effect enhancer, and anti-tumor kit - Google Patents

Description

Antitumor agent, antitumor effect enhancer, and antitumor kit

Technical Field

The present invention relates to an antitumor agent, an antitumor effect enhancer and an antitumor kit.

Background Art

1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl)cytosine (hereinafter sometimes referred to as "Compound A") is known to have excellent antitumor activity and is useful as an antitumor agent (Patent Document 1). Compound A is also known to have strong antitumor activity when orally administered to mice (Non-Patent Documents 1 and 2). Salts of Compound A and methods for their production are also known (Patent Documents 2 to 4).

Taxane-based antitumor agents such as paclitaxel and Nab (nanoparticle albumin-bound) paclitaxel are also useful in chemotherapy for malignant tumors. However, the efficacy of a single-dose taxane-based antitumor agent against tumors is known to be low, at 10-25%, and the survival time of cancer patients is short (12-15 months) (Non-Patent Document 3).

In clinical practice, multi-dose combination therapy is used to compensate for differences in tumor sensitivity among anti-tumor agents and enhance their efficacy. Combinations of paclitaxel with other agents are also known (Patent Document 5). For example, the efficacy of gemcitabine combined with Nab-paclitaxel in pancreatic cancer patients was 23%, with a median survival of 8.5 months (Non-Patent Document 4), which is not considered sufficiently effective as a treatment.

Previous technical literature

Patent Literature

Patent Document 1: International Publication No. 1997/038001

Patent Document 2: International Publication No. 2013/146833 Pamphlet

Patent Document 3: International Publication No. 2011/074484 Pamphlet

Patent Document 4: International Publication No. 2014/027658 Pamphlet

Patent Document 5: International Publication No. 2013/100014 Pamphlet

Non-patent literature

Non-patent document 1: Cancer Letters, 1999, Vol. 144, pp. 177-182

Non-patent document 2: Oncology report, 2002, Vol. 9, p1319-1322

Non-patent document 3: Journal of Clinical Oncology, 2005, Vol. 23, pp. 7794-7803

Non-patent document 4: New England Journal of Medicine, 2013, Vol. 369, pp. 1691-1703

Summary of the Invention

Technical issues to be solved by the invention

In recent years, antitumor drugs have been widely used in combination therapy instead of being administered alone. However, when any antitumor drugs are used in combination, it is not clear whether their antitumor effects are enhanced or whether their effects counteract each other.

The present invention aims to provide an antitumor agent, an antitumor kit, and an antitumor effect enhancer having superior antitumor effects compared to gemcitabine, paclitaxel, and combination therapy thereof.

Means for solving technical problems

Therefore, the present inventors have studied the combined use of various drugs and have found that the combined use of paclitaxel and Compound A exhibits a significant antitumor effect, thereby completing the present invention.

That is, the present invention provides the following.

(1) An antitumor agent comprising paclitaxel or a salt thereof and 1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl)cytosine or a salt thereof or a prodrug thereof.

(2) The antitumor agent according to (1), wherein the amount of 1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl)cytosine or a salt or prodrug thereof is 0.01 to 100 times the molar amount of paclitaxel or a salt thereof.

(3) The antitumor agent according to (1) or (2), wherein the antitumor agent is used for pancreatic cancer.

(4) The antitumor agent according to any one of (1) to (3), wherein the paclitaxel is a nanoparticle containing paclitaxel and albumin.

(5) The antitumor agent according to any one of (1) to (4), wherein the paclitaxel is Nab paclitaxel.

(6) An antitumor effect enhancer comprising 1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl)cytosine or a salt or prodrug thereof used in combination with paclitaxel or a salt thereof.

(7) An antitumor kit comprising a preparation containing paclitaxel or a salt thereof and a preparation containing 1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl)cytosine or a salt thereof or a prodrug thereof.

(8) An antitumor agent comprising 1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl)cytosine or a salt or prodrug thereof used in combination with paclitaxel or a salt thereof.

(6-1) The anti-tumor effect enhancer according to (6), wherein the paclitaxel is a nanoparticle containing paclitaxel and albumin.

(6-2) The anti-tumor effect enhancer according to (6) or (6-1), wherein the paclitaxel is Nab paclitaxel.

(7-1) The antitumor kit according to (7), wherein the paclitaxel is a nanoparticle containing paclitaxel and albumin.

(7-2) The antitumor kit according to (7) or (7-1), wherein the paclitaxel is Nab paclitaxel.

(8-1) The antitumor agent according to (8), wherein the paclitaxel is a nanoparticle containing paclitaxel and albumin.

(8-2) The antitumor agent according to (8) or (8-1), wherein the paclitaxel is Nab paclitaxel.

(9) A method for treating tumors, preferably pancreatic cancer, by using paclitaxel or a salt thereof and 1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl)cytosine or a salt thereof or a prodrug thereof, the method comprising administering a therapeutically effective amount to a subject (including a human mammal) in need of such treatment.

(10) A method for treating tumors, characterized by administering to a subject a combination of a therapeutically effective amount of 1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl)cytosine or a salt or prodrug thereof for combined treatment and a therapeutically effective amount of paclitaxel or a salt thereof for combined treatment.

(11) A method for treating tumors, characterized in that a therapeutically effective amount of 1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl)cytosine or a salt or prodrug thereof used in combination therapy and a therapeutically effective amount of paclitaxel or a salt thereof used in combination therapy are administered to a subject simultaneously, separately, continuously or at intervals.

(12) Use of 1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl)cytosine or a salt or prodrug thereof for the manufacture of an antitumor agent in combination with paclitaxel or a salt thereof.

(13) Use of 1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl)cytosine or a salt or prodrug thereof in combination with paclitaxel or a salt thereof as an antitumor agent.

(14) 1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl)cytosine or a salt or prodrug thereof, which is used for treating tumors by administering it together with paclitaxel or a salt thereof as a single dosage form or as a separate dosage form.

Effects of the Invention

Compound A, or a salt or prodrug thereof, exerts a significant antitumor effect when used in combination with paclitaxel. Specifically, the antitumor agent and antitumor kit of the present invention exhibit superior tumor regression and tumor growth inhibition effects compared to gemcitabine alone, paclitaxel alone, or the combination of gemcitabine and paclitaxel. The antitumor effect enhancer of the present invention can enhance the antitumor effect when administered in combination with paclitaxel or a salt thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a graph showing changes in tumor volume in model mice bearing tumors subcutaneously transplanted with the human pancreatic cancer cell line Capan-1.

FIG2 is a graph showing changes in body weight in model mice bearing tumors subcutaneously transplanted with the human pancreatic cancer cell line Capan-1.

FIG3 is a graph showing the combined use effect on tumor growth inhibition in model mice bearing tumors subcutaneously transplanted with the human pancreatic cancer cell line Capan-1.

DETAILED DESCRIPTION

In the present invention, numerical values expressed as "%" are based on mass unless otherwise specified, and ranges expressed as "to" include both ends unless otherwise specified.

The "subject" refers to mammals such as humans, mice, monkeys, and livestock in need of prevention or treatment, and is preferably a human in need of prevention or treatment.

"Prevention" refers to the obstruction of disease onset, reduction of the risk of disease onset, or delay of disease onset.

"Treatment" refers to improvement or suppression (maintenance or delay) of the progress of a target disease or condition.

"Treatment" refers to the prevention or treatment of various diseases, etc.

"Tumor" refers to a benign or malignant tumor.

"Benign tumor" refers to a tumor whose cells and their arrangement resemble the morphology of the normal cells from which they originate and which is not invasive or metastatic.

"Malignant tumor" refers to a tumor whose morphology or arrangement of tumor cells is different from the normal cells from which they originate and which shows invasive or metastatic properties.

Hereinafter, the present invention will be described in detail.

The present invention provides an antitumor agent comprising paclitaxel or a pharmaceutically acceptable salt thereof (hereinafter sometimes referred to as "its salt") and 1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl)cytosine (Compound A) or a salt or prodrug thereof. Furthermore, the present invention provides an antitumor agent comprising a combination of paclitaxel or a salt thereof and Compound A or a salt or prodrug thereof.

First, Compound A or a salt or prodrug thereof will be described.

Examples of the salt include pharmaceutically acceptable salts, specifically mineral acid salts, organic carboxylic acid salts, and sulfonates. Preferred salts include mineral acid salts and sulfonates.

Examples of mineral salts include hydrochlorides, hydrobromides, hydroiodides, nitrates, phosphates, and sulfates, preferably hydrochlorides, hydroiodides, nitrates, or sulfates, and more preferably hydrochlorides. Examples of organic carboxylates include formates, acetates, citrates, oxalates, fumarates, maleates, succinates, malates, tartrates, aspartates, trichloroacetates, and trifluoroacetates. Examples of sulfonates include methanesulfonates, benzenesulfonates, p-toluenesulfonates, mesitylenesulfonates, and naphthalenesulfonates, preferably methanesulfonates.

The salt of compound A may be an anhydride, a hydrate or a solvate. When simply referred to as a "salt" in this specification, its form may be an anhydride, a hydrate or a solvate. When referred to as an "anhydride" in this specification, except for the cases specifically described, it refers to the case where it is in a state that is neither a hydrate nor a solvate. Even if it is a substance that does not originally form a hydrate or a solvate, the salt of compound A that does not have crystal water, hydration water and an interacting solvent is also included in the so-called "anhydride" in the present invention. Anhydride is sometimes also referred to as "anhydrous". When the salt of compound A is a hydrate, the number of hydration waters is not particularly limited, and it may be a monohydrate, a dihydrate, etc. As examples of solvates, methanolates, ethanolates, propanolates and 2-propanolates can be cited.

Specific examples of particularly preferred salts of Compound A are shown below.

1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl)cytosine methanesulfonate;

1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl)cytosine hydrochloride;

1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl)cytosine 1/2 sulfate;

1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl)cytosine nitrate; and

1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl)cytosine hydroiodide; and anhydrides of any of the foregoing salts.

A prodrug is a compound or a salt thereof in which, after administration, the functional gene that functions as the prodrug is cleaved by a reaction induced by enzymes or gastric factors in the body and converted into a compound exhibiting the desired pharmacological activity.

Examples of the group that forms a prodrug include those described in Stella VJ et al., Prodrugs: Challenges and Rewards. Parts 1 and 2, 2007, American Association of Pharmaceutical Scientists.

The prodrug of Compound A refers to a compound or a salt thereof that is converted into Compound A or its phosphate compound by a reaction caused by an enzyme or gastric acid under physiological conditions in vivo.

As a prodrug of Compound A, the description of International Publication No. 2016/068341 can be cited and referred to, and the contents are incorporated into the description of the present application.

More specifically, for example, the thionucleoside derivative represented by the general formula [1] or a salt thereof described in International Publication No. 2016/068341 is incorporated into the present specification, and its preferred range is also the same as that described in International Publication No. 2016/068341.

In the present invention, Compound A or its salt or prodrug may be used alone or in combination of two or more.

Next, the method for producing compound A or its salt or prodrug is described. Compound A can be produced, for example, by the method described in Patent Document 1 and Journal of Organic Chemistry (Journal of Organic Chemistry), 1999, Vol. 64, p7912-7920. A salt of compound A or its hydrate or solvate can be produced, for example, by the method described in Patent Document 4. A prodrug of compound A can be produced, for example, by the method described in International Publication No. 2016/068341.

The compound A of the present invention or a salt or prodrug thereof can be used as an antitumor agent and as an active ingredient of a pharmaceutical composition.

In the present invention, paclitaxel or its salt may be used alone or in combination of two or more. Paclitaxel or its salt may be used in addition to paclitaxel or its salt or a composition containing them.

Examples of the salt include pharmaceutically acceptable salts, and specific examples include salts of generally known basic groups such as an amino group, and acidic groups such as a hydroxyl group and a carboxyl group.

Examples of the salt in the basic group include salts with mineral acids such as hydrochloric acid, hydrobromic acid, nitric acid and sulfuric acid; salts with organic carboxylic acids such as formic acid, acetic acid, citric acid, oxalic acid, fumaric acid, maleic acid, succinic acid, malic acid, tartaric acid, aspartic acid, trichloroacetic acid and trifluoroacetic acid; and salts with sulfonic acids such as methanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, mesitylenesulfonic acid and naphthalenesulfonic acid.

Examples of the salt of the acidic group include salts with alkali metals such as sodium and potassium; salts with alkaline earth metals such as calcium and magnesium; ammonium salts; and salts with nitrogen-containing organic bases such as trimethylamine, triethylamine, tributylamine, pyridine, N,N-dimethylaniline, N-methylpiperidine, N-methylmorpholine, diethylamine, dicyclohexylamine, procaine, dibenzylamine, N-benzyl-β-phenylethylamine, 1-diphenylhydroxymethylamine, and N,N'-dibenzylethylenediamine.

Examples of compositions containing paclitaxel or a salt thereof include nanoparticles containing paclitaxel and albumin (preferably human serum albumin) (albumin-bound paclitaxel injectable suspension (Nab-paclitaxel, trade name "ABRAXANE"), which is a nanoparticle preparation in which paclitaxel is encapsulated with albumin); high-molecular-weight micelles (NK105) in which paclitaxel is encapsulated in a block copolymer of polyethylene glycol and polyaspartic acid; a prodrug (Taxoprexin) in which paclitaxel is conjugated to the fatty acid docosahexaenoic acid (DHA); a prodrug (trade name "Opaxio") in which paclitaxel is conjugated to polyglutamine; and a prodrug in which paclitaxel is conjugated to a monoclonal antibody that targets tumor cells.

As paclitaxel, nanoparticles containing paclitaxel and albumin are preferred, and Nab paclitaxel is more preferred.

Compound A is an antitumor agent having an excellent DNA synthesis inhibitory effect. When used in combination with paclitaxel, Compound A is expected to enhance the antitumor effect of paclitaxel without significantly worsening toxicity.

(Antitumor Agent)

According to the present invention, there is provided:

An antitumor agent comprising paclitaxel or a salt thereof and 1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl)cytosine or a salt or prodrug thereof; and

An antitumor agent comprising 1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl)cytosine or a salt or prodrug thereof used in combination with paclitaxel or a salt thereof.

The antitumor agent of the present invention may contain additives commonly used in formulations, such as excipients, binders, lubricants, disintegrants, colorants, flavorings, emulsifiers, surfactants, solubilizers, suspending agents, isotonicity agents, buffers, preservatives, antioxidants, stabilizers, and absorption enhancers.

The antitumor agent of the present invention comprising paclitaxel or a salt thereof and Compound A or a salt thereof or a prodrug thereof may be a single-dose formulation comprising paclitaxel or a salt thereof and Compound A or a salt thereof or a prodrug thereof, or a two-dose formulation comprising paclitaxel or a salt thereof and Compound A or a salt thereof or a prodrug thereof. Preferably, the two-dose formulation comprises paclitaxel or a salt thereof and Compound A or a salt thereof or a prodrug thereof as separate formulations.

When paclitaxel or a salt thereof and Compound A or a salt or prodrug thereof are used as separate formulations, each formulation can be administered to a subject simultaneously, separately, sequentially, or at intervals. Furthermore, the administration route of the composition containing paclitaxel and the composition containing Compound A can be the same or different (e.g., oral administration versus injection).

Examples of administration routes of the antitumor agent of the present invention include intravenous, intraarterial, intrarectal, intraperitoneal, intramuscular, intratumoral, or intravesical injection, oral administration, transdermal administration, and/or suppository administration.

As route of administration, preferred non-oral administration. For example, intravenous injection (intravenous injection), intramuscular injection, intraperitoneal injection, subcutaneous injection, intraocular injection and/or intramedullary injection such as drip can be enumerated. As method of administration, the administration carried out by syringe or drip can be enumerated.

The dosage or blending amount of paclitaxel or its salt and Compound A or its salt or prodrug contained in the antitumor agent of the present invention is not particularly limited as long as it is within the range of the enhancement effect of the antitumor effect. The amount of Compound A or its salt or prodrug is 0.01 to 100 times the mole, preferably 0.1 to 50 times the mole, and more preferably 1 to 40 times the mole relative to 1 mole of paclitaxel.

Regarding the dosage and frequency of paclitaxel or its salt, for example, 1 to 1000 mg/m 2 can be administered orally or parenterally (eg, by injection, intravenous drip, and rectal administration) to adults, for example, once or several times a ^day .

The dosage and frequency of administration of Compound A or its salt or prodrug may be 1 to 2000 mg/m ² per day, divided into one or several doses. However, the dosage and frequency are not limited to these.

Examples of dosage forms of the antitumor agent of the present invention include tablets, capsules, powders, syrups, granules, pills, suspensions, emulsions, liquids, suppositories, eye drops, nasal drops, ear drops, patches, ointments, and injections, with injections being preferred. These dosage forms can be manufactured by conventional formulation methods known to those skilled in the art.

The antitumor agent of the present invention can be effectively used to treat various types of tumors, including, for example, melanoma, liver cancer, glioma, neuroblastoma, sarcoma, and tumors of the lung, colon, breast, bladder, ovary, testis, prostate, neck, pancreas, stomach, small intestine, and other organs. The antitumor agent of the present invention is preferably an anti-malignant tumor agent and can be used as an anticancer agent, and is particularly effective in treating pancreatic cancer.

(Anti-tumor kit)

The antitumor kit of the present invention is a kit comprising a combination of (a) paclitaxel or a salt thereof and (b) compound A or a salt thereof or a prodrug thereof.

Furthermore, in the above kit, (a) paclitaxel or a salt thereof and (b) Compound A or a salt or a prodrug thereof can be prepared in various known formulations and accommodated in various commonly used containers according to their formulations.

Furthermore, in the above kit, (a) paclitaxel or a salt thereof and (b) Compound A or a salt thereof or a prodrug thereof may be contained in separate containers or mixed and contained in the same container. Preferably, (a) paclitaxel or a salt thereof and (b) Compound A or a salt thereof or a prodrug thereof are contained in separate containers.

(Anti-tumor effect enhancer)

The antitumor effect enhancer of the present invention is an antitumor agent comprising 1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl)cytosine or a salt or prodrug thereof used in combination with paclitaxel or a salt thereof.

The anti-tumor effect enhancer of the present invention may contain additives commonly used in formulations, such as excipients, binders, lubricants, disintegrants, colorants, flavorings, emulsifiers, surfactants, solubilizers, suspending agents, isotonicity agents, buffers, preservatives, antioxidants, stabilizers, and absorption enhancers.

The anti-tumor effect enhancer of the present invention can be administered to a subject simultaneously with, separately from, continuously with, or at intervals with paclitaxel or a salt thereof.

As the route of administration of the anti-tumor effect enhancer of the present invention, parenteral administration is preferred. For example, intravenous injection (intravenous injection) such as drip, intramuscular injection, intraperitoneal injection, subcutaneous injection, intraocular injection, and intramedullary injection can be mentioned. As the method of administration, administration by syringe or drip can be mentioned.

The dosage or incorporation amount of Compound A, or a salt thereof, or a prodrug contained in the antitumor effect enhancer of the present invention is not particularly limited as long as it is within the range that exhibits the antitumor effect enhancement effect. The dosage or incorporation amount of Compound A, or a salt thereof, or a prodrug is 0.01 to 100-fold, preferably 0.1 to 50-fold, and more preferably 1 to 40-fold, relative to 1 mol of paclitaxel.

The dosage and frequency of administration of Compound A or its salt or prodrug contained in the antitumor effect enhancer of the present invention can be 1 to 2000 mg/m ² per day, administered once or several times. However, the dosage and frequency are not limited to these dosages.

The anti-tumor effect enhancer of the present invention can be effectively used to treat a variety of tumor types, including, for example, melanoma, liver cancer, glioma, neuroblastoma, sarcoma, and tumors of the lung, colon, breast, bladder, ovary, testis, prostate, neck, pancreas, stomach, small intestine, and other organs. The anti-tumor effect enhancer of the present invention is preferably an anti-malignant tumor effect enhancer and is particularly effective in treating pancreatic cancer.

The present invention provides a method for treating tumors, preferably pancreatic cancer, using paclitaxel or a salt thereof and 1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl)cytosine or a salt or prodrug thereof. The method comprises administering a therapeutically effective amount to a subject (including a human mammal) in need of such treatment.

Furthermore, the present invention provides a method for treating tumors, characterized by administering to a subject a therapeutically effective amount of 1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl)cytosine or a salt or prodrug thereof for combined treatment and a therapeutically effective amount of paclitaxel or a salt thereof for combined treatment.

Furthermore, the present invention provides a method for treating tumors, characterized in that a therapeutically effective amount of 1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl)cytosine or a salt or prodrug thereof for combined treatment and a therapeutically effective amount of paclitaxel or a salt thereof for combined treatment are administered to a subject simultaneously, separately, continuously, or at intervals.

1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl)cytosine or a salt or prodrug thereof can be used to produce an antitumor agent in combination with paclitaxel or a salt thereof.

1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl)cytosine or a salt or prodrug thereof can be used as an antitumor agent in combination with paclitaxel or a salt thereof.

According to the present invention, 1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl)cytosine or a salt or prodrug thereof can be obtained, which is used for treating tumors by administering it together with paclitaxel or a salt thereof as a single dosage form or as separate dosage forms.

Furthermore, according to the present invention, an antitumor agent comprising 1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl)cytosine or a salt or a prodrug thereof used in combination with paclitaxel or a salt thereof can be obtained.

Example

The present invention will be further described in detail below with reference to Examples and Test Examples, but the present invention is not limited to these Examples, etc. Furthermore, the dosage of various antitumor agents used to enhance the antitumor effect shown in the following Test Examples was determined using the maximum tolerated dose (MTD) reported in research papers and the like.

(Example 1)

The methanesulfonate of 1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl)cytosine (Compound A) was synthesized by the method described in International Publication No. 2013/146833.

(Test Example 1)

Combined effect test using Capan-1 subcutaneously transplanted tumor model mice

As test substances, gemcitabine (hereinafter also referred to as Gem), ABRAXANE (hereinafter also referred to as Abx), and the mesylate of Compound A were used.

A solution prepared by dissolving gemcitabine hydrochloride (manufactured by Teva Takeda Pharma Ltd.) in physiological saline was used for gemcitabine, and a solution prepared by dissolving ABRAXANE (manufactured by Celgene Corporation) in physiological saline was used for ABRAXANE.

Capan-1 cells, a human pancreatic cancer cell line, were subcutaneously injected into the flanks of 5- to 6-week-old female BALB/cA Jcl-nu mice. Following tumor implantation, the major and minor diameters (mm) of the tumors were measured, and tumor volume (TV) was calculated. Mice were assigned to groups to achieve an equal average TV for each group. The day of grouping (n = 8) was designated Day 1.

The test solution for the ABRAXANE alone group was prepared at a dosage of 30 mg/kg/day. The test solution for the Compound A alone group was prepared at a dosage of 480 mg/kg/day. Compound A was administered via the tail vein of the mice once a week, starting on day 1, for a total of three doses. Similarly, ABRAXANE was administered via the tail vein of the mice once a week, starting on day 1, for a total of three doses. In the combined administration group, Compound A was administered at 480 mg/kg/day and ABRAXANE at 30 mg/kg/day.

For comparative experiments, gemcitabine was used as a control drug. The test solution for the gemcitabine alone group was prepared at 240 mg/kg/day. Gemcitabine was administered via the tail vein of the mice three times a week, starting on day 1. In the combination group, gemcitabine was administered at 240 mg/kg/day and ABRAXANE at 30 mg/kg/day.

In this study, the dosages of Compound A and gemcitabine were set using the MTD of each agent. ABRAXANE was used at the maximum dose that can be tolerated when used in combination with each agent. For antitumor agents, the dose at which maximal efficacy is observed is very close to the dose at which toxicity is observed. To evaluate the maximum antitumor effect of an agent in animal models, evaluation is generally performed near the MTD. In this study, the MTD and the dose at which maximal efficacy is observed are defined in a similar manner.

As an indicator of the antitumor effect, TV on day 33 (day 33) was measured in each drug administration group, and the relative tumor volume (RTV) and T/C (%) relative to day 1 were calculated using the following formula to evaluate the antitumor effect. Regarding the evaluation of the combined effect, when the average RTV value of the combined administration group was statistically significantly lower than the average RTV value of each single administration group (Welch's IUT, over all maximum p < 0.05), it was judged that there was a combined effect. The results are shown in Table 1 and Figure 1. In the table, the * mark indicates that a statistically significant difference was observed between the control group (also referred to as Control) and the Gem or Compound A single group.

TV (mm ³ ) = (long diameter × short diameter ² )/2

RTV = (TV on day 33) / (TV on day 1)

T/C (%) = [(average RTV value of the test solution administration group) / (average RTV value of the control group)] × 100

[Table 1]

*: indicates statistical significance

Compound A significantly enhanced the anti-tumor effects of ABRAXANE. Combined use in nude mice at a high dose (maximal effect dose), 480 mg/kg/day, induced significant tumor shrinkage. This effect is believed to be greater than that of gemcitabine, an existing drug. A more detailed description will be provided later.

Body weight (BW) was measured over time as an indicator of toxicity, and the average body weight change rate (BWC (%)) from day 1 to day 33 was calculated using the following formula (n represents the day of body weight measurement, with the final measurement day corresponding to day 33, the final evaluation day). The results are shown in FIG2 .

BWC (%) = [(BW on day n) - (BW on day 1)] / (BW on day 1) × 100

No worsening of body weight loss was observed during concurrent administration.

The combined effect of the present invention is evaluated using the combination index (CI), which is a quantitative indicator of the combined effect. CI can be calculated using the following formula based on Cancer Research, 2010, Vol. 70, pp. 440-446.

That is, if the drugs used in combination are drug 1 and drug 2, then

CI = (T/C when used together) ÷ 100 / {[(T/C of drug 1) ÷ 100] × [(T/C of drug 2) ÷ 100]}

CI＝1：Additive effect

CI＞1: antagonistic effect

CI < 1: Multiplicative effect

The CI was 0.80 when ABRAXANE and gemcitabine were used together, and 0.32 when ABRAXANE and Compound A were used together. Since CI < 1, a synergistic effect was observed due to the combined use, and the synergistic effect of Compound A was more significant than that of gemcitabine, an existing drug.

Furthermore, the combined use effect of the present invention is evaluated using the tumor growth control (GC) effect. The evaluation method used was the same as that in Figure 5B of Molecular Cancer Therapeutics, 2013, Vol. 12, pp. 2585-2696.

As described in the above-mentioned document, GC can be calculated by the following formula.

[1] When RTV>1

GC (%) = [(RTV-1 of the agent) / (RTV-1 of the control)] × 100

[2] When RTV≤1

GC (%) = (RTV of the drug - 1) × 100

The combined effect of ABRAXANE and Compound A or gemcitabine was estimated based on the single-agent efficacy using the following calculation formula. The results are shown in FIG3 and Table 2.

Estimated GC (%) of combined use = [GC (%) of ABRAXANE × GC (%) of single dose] ÷ 100

For example, in this test example, according to Table 1, regarding the GC (%) of ABRAXANE single dose,

Since RTV>1,

Therefore, [(2.03-1)/(4.01-1)]×100=34.2(%),

Regarding the GC (%) of gemcitabine, since RTV>1,

Therefore, [(2.74-1)/(4.01-1)]×100=57.8(%).

Therefore, the estimated combined GC (%) is (34.2×57.8)÷100=19.8 (%).

On the other hand, regarding the actual GC (%) of ABRAXANE and gemcitabine combined use,

Since RTV>1, [(1.11-1)/(4.01-1)]×100=3.7(%).

Therefore, the actual combined GC (%) was 3.7 (%) compared to the estimated combined GC (%) of 19.8 (%), and thus it is considered that there is a significant combined effect greater than the assumed combined effect.

When the same calculation is performed for compound A, for a single dose, since RTV>1,

Therefore, [(1.29-1)/(4.01-1)]×100=9.6(%).

Therefore, the estimated combined GC (%) is (34.2×9.6)÷100=3.3 (%).

The actual GC (%) is (0.21-1)×100=-79.0 (%) because RTV≤1. The solid arrow in FIG3 represents the combined effect of gemcitabine, and the dotted arrow represents the combined effect of Compound A.

Therefore, in Compound A, the actual combined use GC (%) was -79.0 (%), while the estimated combined use GC (%) was 3.3 (%), indicating that it also has a significant combined effect greater than the assumed combined use effect. This degree can be said to be more significant than that of gemcitabine, an existing drug.

[Table 2]

Industrial applicability

The present invention is useful as an antitumor agent and an antitumor kit showing a significant antitumor effect, and an antitumor effect enhancer.

Claims (3)

1. An antitumor agent comprising: Paclitaxel or its salts; and 1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranyl)cytosine or a salt thereof, The amount of 1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranyl)cytosine or a salt thereof used is 1 to 40 times the molar amount of paclitaxel or a salt thereof. The antitumor agent is used for pancreatic cancer. The paclitaxel mentioned is Nab-paclitaxel. 2. An antitumor reagent kit, comprising: Preparations containing paclitaxel or its salts; and Preparations containing 1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranyl)cytosine or a salt thereof, The amount of 1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranyl)cytosine or a salt thereof used is 1 to 40 times the molar amount of paclitaxel or a salt thereof. The antitumor kit is used for pancreatic cancer. The paclitaxel mentioned is Nab-paclitaxel. 3. Use of paclitaxel or a salt thereof in combination with 1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranyl)cytosine or a salt thereof in the manufacture of an antitumor agent, wherein, The amount of 1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranyl)cytosine or a salt thereof used is 1 to 40 times the molar amount of paclitaxel or a salt thereof. The antitumor agent is used for pancreatic cancer. The paclitaxel mentioned is Nab-paclitaxel.