Uses of liposome components

Abstract

The objective of this invention is to provide a treatment agent for Merkel cell carcinoma. According to this invention, a treatment agent for Merkel cell carcinoma is provided, comprising an aqueous solution having an inner aqueous phase of liposomes and an outer aqueous phase of dispersed liposomes, wherein the liposomes contain topotecan or its salt, the lipids constituting the liposomes include polyethylene glycol-modified lipids, dihydrosphingomyelin, and cholesterol, and the inner aqueous phase contains an ammonium salt.

Description

[Technical Field]

[0001] This invention relates to a treatment agent for the prevention or treatment of Merkel cell carcinoma. [Previous Technology]

[0002] Merkel cell carcinoma is a highly malignant tumor with a high probability of local recurrence, regional lymph node metastasis, and distant metastasis, and a poor prognosis. Its primary treatment is extensive resection, followed by prophylactic lymph node dissection and radiotherapy. In cases of recurrence and metastasis, immune checkpoint inhibitors are used. Although various chemotherapy therapies have been reported, no definitive chemotherapy regimen has been established.

[0003] On the other hand, in chemotherapy, therapies that use liposomes to accumulate drugs at the site of lesions such as cancer and expose them for a long time have been studied extensively.

[0004] Patent Document 1 describes a liposome composition containing diacylphospholipid ethanolamine, dihydrosphingomyelin and cholesterol modified by hydrophilic polymers as components of the liposome membrane, which exhibits a high AUC (area under the blood concentration-time curve).

[0005] Patent Document 2 describes a liposome containing topotecan within a liposome containing sphingomyelin and cholesterol. Patent Document 3 describes a liposome containing topotecan within a liposome containing dihydrosphingomyelin and cholesterol.

[0006] Patent Document 4 describes a liposomal camptothecin preparation suitable for improving the stability of camptothecin. The preparation comprises (a) camptothecin encapsulated in liposomes, (b) a first solution located outside the liposomes and having a pH below 4.5, and (c) a second solution located inside the liposomes. Furthermore, the liposomes are described as containing dihydrosphingomyelin and cholesterol.

[0007] Patent Document 5 describes a liposome in which topotecan is contained in a liposome containing purified hydrogenated soybean phospholipids or sphingomyelin, cholesterol and hydrophilic polymer derivative lipids in the presence of ammonium sulfate.

[0008] [Patent Document 1] International Publication No. 2018 / 181963 [Patent Document 2] U.S. Patent No. 7,060,828B2 [Patent Document 3] U.S. Patent No. 7,811,602B2 [Patent Document 4] Japanese Patent Publication No. 2008-519045 [Patent Document 5] U.S. Patent No. 6,355,268B2

[0009] As mentioned above, apart from immune checkpoint inhibitors, no effective treatment for the prevention or treatment of Merkel cell carcinoma has been identified. On the other hand, there are currently no reports on the results of administering liposomes containing topotecan or its salts to cancer patients, and no studies have been conducted on the pharmacological effects of liposomes containing topotecan or its salts on cancer patients. [Summary of the Invention]

[0010] As a result of in-depth research conducted by the inventors in order to solve the above-mentioned problems, they discovered that liposomes containing topotecan or its salts are effective in treating Merkel cell carcinoma, and thus completed the present invention.

[0011] That is, the present invention provides the following. [1] A treatment agent for Merkel cells, comprising an aqueous solution having an inner aqueous phase of liposomes and an outer aqueous phase of dispersed liposomes, wherein the liposomes contain topotecan or a salt thereof, the lipids constituting the liposomes comprising polyethylene glycol-modified lipids, dihydrosphingomyelin and cholesterol, and an ammonium salt thereof in the inner aqueous phase. [2] The treatment agent as described in [1], wherein the dihydrosphingomyelin is a dihydrosphingomyelin having alkyl groups having 16 carbons and 18 carbons. [3] The treatment agent as described in [1] or [2], wherein the ammonium salt is ammonium sulfate, and the molar ratio of sulfate ions contained in the inner aqueous phase to the total molar of topotecan or a salt thereof contained in the treatment agent is 0.36 or more. [4] The treatment agent of any one of [1] to [3], wherein the polyethylene glycol-modified lipid is a diacylphosphatidylethanolamine modified with polyethylene glycol or methoxy polyethylene glycol. [5] The treatment agent of any one of [1] to [4], wherein the ratio of cholesterol to the total cholesterol content of the lipids constituting the liposome is 35 to 43 mmol. [6] The treatment agent of any one of [1] to [5], wherein the pH of the external aqueous phase is 5.5 to 8.5. [7] The treatment agent of any one of [1] to [6], wherein the topotecan or its salt contained in the liposome is administered at a dose of 0.1 mg / m² body surface area to 10 mg / m² body surface area per administration, calculated as topotecan. [8] The treatment agent of any one of [1] to [7], wherein the administration is repeated once every 1 to 8 weeks. [9] The treatment agent as described in any of [1] to [8], wherein the route of administration is intravenous.

[0012] [A] A method for treating Merkel cell carcinoma, comprising administering a composition having an inner aqueous phase of liposomes and an outer aqueous phase of dispersed liposomes, wherein the liposomes contain topotecan or a salt thereof, the lipids constituting the liposomes comprising polyethylene glycol-modified lipids, dihydrosphingomyelin and cholesterol, and the inner aqueous phase comprising an ammonium salt. [B] A treatment agent for treating Merkel cells, comprising an inner aqueous phase of liposomes and an outer aqueous phase of dispersed liposomes, wherein the liposomes contain topotecan or a salt thereof, the lipids constituting the liposomes comprising polyethylene glycol-modified lipids, dihydrosphingomyelin and cholesterol, and the inner aqueous phase comprising an ammonium salt. [C] Use of a composition for manufacturing a treatment agent for treating Merkel cell carcinoma, the composition comprising an aqueous solution having an inner aqueous phase of liposomes and an outer aqueous phase of dispersed liposomes, wherein the liposomes contain topotecan or a salt thereof, the lipids constituting the liposomes comprising polyethylene glycol-modified lipids, dihydrosphingomyelin, and cholesterol, the inner aqueous phase containing an ammonium salt, and the topotecan or its salt contained in the liposomes being administered at a dose of 0.1 mg / m² body surface area to 10 mg / m² body surface area, calculated as topotecan. [Effects of the Invention]

[0013] The treatment agent of the present invention is useful in the treatment of Merkel cell carcinoma, such as for prevention or treatment. Furthermore, by administering the treatment agent of the present invention to a subject, the volume reduction of Merkel cell carcinoma is significant. Moreover, based on the effects obtainable by the treatment agent of the present invention, it is expected that the progression-free survival, overall survival, and QOL of the administered subject will be prolonged.

Implementation Method

[0015] [Form for implementing the invention]

[0016] Unless otherwise specified, the range indicated by "~" in this invention includes values ​​at both ends. "Treatment" refers to the treatment or prevention of various diseases. "Subject" refers to mammals such as humans, rats, monkeys, and livestock that require prevention or treatment, preferably humans. "Prevention" refers to suppressing onset, reducing the risk of onset, or delaying onset. "Treatment" refers to the improvement or suppression (maintenance or delay) of a disease or condition. "Progression-free survival" refers to the period during which cancer does not progress and remains stable during (or after) treatment. "Overall survival" refers to the period during which a subject survives from the date of allocation of the treatment or the date of treatment in a clinical trial. "QOL" is an abbreviation for Quality of Life, referring to the quality of life of a subject undergoing treatment or convalescence, including physical, mental, social, and economic aspects.

[0017] Hereinafter, the present invention will be described in detail. The treatment agent of the present invention is a treatment agent for Merkel cells, comprising an aqueous solution having an inner aqueous phase of liposomes and an outer aqueous phase of dispersed liposomes, wherein the liposomes contain topotecan or its salt, the lipids constituting the liposomes include polyethylene glycol-modified lipids, dihydrosphingomyelin and cholesterol, and the inner aqueous phase contains ammonium salts.

[0018] (Liposomes) A ​​lipid system consists of closed small cells formed by lipid bilayer membranes using lipids, and the space within the closed small cells contains an aqueous phase (inner aqueous phase). The inner aqueous phase contains water, etc. Liposomes usually exist in the form of an aqueous solution dispersed outside the closed small cells (outer aqueous phase). Liposomes can be single-layered (also called single-layer lamella or uni-lamella, a structure in which the bilayer membrane is a single layer), or multilayered (also called multilayered, a structure of multiple bilayer membranes in an onion-like shape, with each layer separated by an aqueous layer). In this invention, from the viewpoint of safety and stability for pharmaceutical use, single-layered liposomes are preferred.

[0019] As long as the liposome is capable of containing a drug, its morphology is not particularly limited. "Contains" refers to the form in which the drug is contained within the aqueous phase of the liposome. For example, forms in which the drug is encapsulated in a closed space formed by a membrane, forms contained within the membrane itself, and combinations thereof can be given.

[0020] The average particle size of liposomes is generally 10nm to 1000nm, with 20nm to 500nm being preferred, 30nm to 300nm being even better, 30nm to 200nm being further preferred, 30nm to 150nm being even more preferred, and 50nm to 150nm being particularly preferred. Spherical or similar morphology of liposomes is preferred.

[0021] In anticipation of an EPR (Enhanced permeability and retention) effect, a substantially diameter of 50–200 nm is preferred, a substantially diameter of 50–150 nm is more preferred, and a substantially diameter of 50–100 nm is even more preferred. The term "substantially" means that at least 75% of the liposomes are within the specified diameter range. Regarding the aforementioned "at least 75%", at least 80% is preferred, and at least 90% is even more preferred. Furthermore, in this invention, unless otherwise stated, "average particle size" refers to the average particle size (preferably cumulative average particle size) measured using dynamic light scattering. The "average particle size" can be measured using a device capable of measuring the average particle size by light scattering.

[0022] The components constituting the lipid bilayer of the liposome are selected from lipids. The liposomes of the present invention contain diacylphosphatidylethanolamine, dihydrosphingomyelin, and cholesterol modified with hydrophilic polymers as components of the liposome membrane.

[0023] The liposomes of the present invention comprise dihydrosphingomyelin. By using dihydrosphingomyelin, the retention of liposomes in the blood can be improved. Furthermore, the septal properties of the liposome membrane can be improved, thereby preventing leakage of topotecan or its salts. Dihydrosphingomyelin generally has two long-chain alkyl groups in its molecule; examples include those having two 16-carbon long-chain alkyl groups, those having 16 and 18-carbon long-chain alkyl groups, and those having 16 and 20-24-carbon long-chain alkyl groups. From the viewpoint of preventing drug leakage from liposomes, compounds having 16 and 18-carbon long-chain alkyl groups are preferred as dihydrosphingomyelin. This is because the more carbon groups, the higher the melting point, and thus a liposome membrane with high septal properties can be formed.

[0024] [Chemical Formula 1]

[0025] As dihydrosphingomyelin, for example, dihydrosphingomyelin obtained by reducing sphingomyelin derived from natural substances using conventional methods can be used, or dihydrosphingomyelin obtained through synthesis can be used. Since most dihydrosphingomyelin derived from natural substances such as eggs generally have two long-chain alkyl groups with 16 carbon atoms, from the viewpoint that dihydrosphingomyelin with long-chain alkyl groups having 16 and 18 carbon atoms can be obtained with high purity, it is preferable to use the one obtained through chemical synthesis.

[0026] The ratio of dihydrosphingomyelin in the total lipids constituting the liposomes is preferably 30-80 mmol, more preferably 40-70 mmol, and even more preferably 50-60 mmol.

[0027] The liposomes of the present invention comprise lipids modified with polyethylene glycol (hereinafter referred to as PEG-modified lipids). Furthermore, polyethylene glycol can also be used in the form of derivatives, such as methoxy polyethylene glycol. In the case of PEG modification, derivatives of polyethylene glycol are also included. Examples of PEG-modified lipids include PEG-modified phospholipids, PEG-modified monoglycerides, PEG-modified diglycerides, PEG-modified dehydrated sorbitol fatty acid esters, PEG-modified monoalkyl ethers, and PEG-modified sterols. The above-mentioned hydrophilic polymers can be used individually or in combination of two or more.

[0028] The molecular weight of polyethylene glycol is not particularly limited, but is 500 to 10,000 Daltons, preferably 1,000 to 7,000 Daltons, and even more preferably 2,000 to 5,000 Daltons.

[0029] Examples of PEG-modified lipids include 1,2-distearyl-3-phosphatidylethanolamine-PEG2000 (manufactured by NOF CORPORATION), distearylglycerol-PEG2000 (manufactured by Nippon Oil & Fats Co., Ltd.), and 1,2-distearyl-3-phosphatidylethanolamine-PEG5000 (manufactured by Nippon Oil & Fats Co., Ltd.), as well as cholesterol-PEG 600 (manufactured by Merck. Ltd.), and cholesterol-PEG 600, etc.

[0030] From the viewpoint of versatility and blood retention, PEG-modified phospholipids and PEG-modified monoalkyl ethers are preferred as PEG-modified lipids, with PEG-modified phospholipids being even more preferred. Among PEG-modified phospholipids, PEG-modified phosphatidylethanolamine is preferred, and diacitylphosphatidylethanolamine modified with polyethylene glycol or methoxy polyethylene glycol is even more preferred.

[0031] In the total lipids constituting the liposomes, the proportion of PEG-modified lipids is preferably 1-15 mol%, more preferably 2-10 mol.

[0032] The liposomes of the present invention contain cholesterol. Adding cholesterol to liposomes is expected to reduce the membrane fluidity of the liposomes by filling the gaps in the liposome membrane.

[0033] The cholesterol ratio in the lipids constituting the liposomes is preferably 20 mol% to 50 mol, more preferably 30 mol% to 45 mol, and even more preferably 35 to 43 mol.

[0034] (Topotecan or its salt) The liposomes of the present invention contain topotecan or its salt. The chemical name of topotecan is (10-[(dimethylamino)methyl]-4-ethyl-4,9-dihydroxy-1H-pyrano[3',4':6,7] indo[1,2-b]quinoline-3,14(4H,12H)dione, which is an anticancer agent with topoisomerase activity inhibition. In the present invention, topotecan can be topotecan itself, or a salt permitted as a pharmaceutical preparation, or a precursor drug for the release of topotecan in vivo. In the present invention, the use of topotecan hydrochloride is preferred.

[0035] (Ammonium sulfate in the internal aqueous phase) The internal aqueous phase of the liposomes in this invention contains an ammonium salt. Examples of ammonium salts include ammonium sulfate, ammonium citrate, ammonium phosphate, ammonium tartrate, ammonium succinate, fatty acid ammonium, ammonium chloride, and sucrose 8-ammonium sulfate. Among these, ammonium sulfate, ammonium citrate, ammonium phosphate, and sucrose 8-ammonium sulfate are preferred because they can improve the retention stability of the drug by reducing its solubility in the liposomes and causing it to precipitate. Ammonium sulfate is particularly preferred.

[0036] It is preferable that the mole ratio of sulfate ions contained in the aqueous phase to the total moles of topotecan or its salts contained in the treatment agent of the present invention is 0.36 or more, more preferably 0.4 or more, further preferably 0.4 or more and 1.8 or less, and especially preferably 0.6 or more and 1.8 or less. By setting the mole ratio of sulfate ions as described above, the leakage of the drug from liposomes in the blood can be inhibited.

[0037] Furthermore, in the treatment agent of the present invention, the ratio of sulfate ions contained in the aqueous phase of the liposomes to the total sulfate ions in the treatment agent (the aqueous phase ratio of sulfate ions) is preferably at least 80%, and more preferably at least 90%. Simultaneously, the ratio of topotecan or its salt contained in the aqueous phase of the liposomes to the total topotecan or its salt in the treatment agent (the aqueous phase ratio of the drug) is preferably at least 80%, and more preferably at least 90%.

[0038] The concentration of topotecan or its salt in liposomes can be measured, for example, by liquid chromatography / UV-Vis absorbance detection. Furthermore, the concentration of sulfate ions in the aqueous phase of the liposomes can be measured, for example, by ion chromatography.

[0039] (Method for manufacturing liposomes) The liposomes of the present invention are not particularly limited, for example, they can be implemented by referring to Patent Document 1 (International Publication No. 2018 / 181963).

[0040] (Treatment Agent) This invention relates to a treatment agent for Merkel cell carcinoma. Merkel cell carcinoma is a very rare type of skin cancer caused by the uncontrolled proliferation of Merkel cells present in the epidermis of the skin. The Merkel cell carcinoma of this invention can be localized or metastatic.

[0041] The treatment agent of the present invention can be used in the treatment of Merkel cell carcinoma resistant to immunotherapy. Resistance refers to the resistance of cancer cells to anticancer agents, including natural resistance where the anticancer agent becomes ineffective from the start of treatment and a state in which an initially effective anticancer agent becomes ineffective or less effective during continued treatment. Specifically, it refers to the following properties: although there is an initial response to the anticancer agent, a decreased responsiveness is shown in subsequent treatments, or the cells continue to proliferate during treatment with the anticancer agent without showing an appropriate response to the anticancer agent.

[0042] For tumors exhibiting resistance, it is important in cancer treatment to change the type of anticancer agent to prolong the period during which a therapeutic effect can be achieved. Furthermore, the type and quantity of resistant anticancer agents sometimes become important information in the selection of subsequent anticancer agents. Cancers suitable for treatment based on the present invention include Merkel cell carcinoma that has not undergone prior treatment with anticancer agents, and Merkel cell carcinoma that has undergone one or more prior treatments. Preferably, it is Merkel cell carcinoma that has undergone up to three prior treatments and has shown resistance to immunotherapy; particularly preferably, it is Merkel cell carcinoma that has shown resistance to immunotherapy and has undergone up to three prior treatments, including treatment with immunotherapy.

[0043] The dosage form of the treatment agent of the present invention is preferably a liquid pharmaceutical preparation, for example, an injectable preparation. Regarding the concentration of topotecan or its salt contained in the liquid pharmaceutical preparation of the present invention, it is preferably 0.25 mg / mL to 5 mg / mL, calculated as topotecan. More preferably, it is 0.1 mg / mL to 3 mg / mL, and even more preferably, it is 0.5 mg / mL to 3 mg / mL.

[0044] The pH of the liquid pharmaceutical preparation of the present invention is preferably 5.5 to 8.5.

[0045] The liquid pharmaceutical formulation of the present invention may typically contain additives such as emulsifiers, surfactants, solubilizers, suspending agents, tension agents, buffers, preservatives, antioxidants, stabilizers, and absorption promoters.

[0046] As a tensioning agent, there are no particular limitations. For example, inorganic salts such as sodium chloride, potassium chloride, sodium hydrogen phosphate, sodium dihydrogen phosphate, and potassium dihydrogen phosphate can be cited; polyols such as glycerol, mannitol, and sorbitol can be cited; and sugars such as glucose, fructose, lactose, or sucrose can be cited.

[0047] As a stabilizer, there are no particular limitations. For example, sugars such as glycerol, mannitol, sorbitol, lactose or sucrose can be cited.

[0048] As an antioxidant, there are no particular limitations. Examples include ascorbic acid, urea acid, tocopherol homologues (e.g., vitamin E, four isomers of tocopherol α, β, γ, and δ), cysteine, EDTA, etc. Stabilizers and antioxidants can be used alone or in combination of two or more.

[0049] As pH adjusters, examples include sodium hydroxide, citric acid, acetic acid, triethanolamine, sodium hydrogen phosphate, sodium dihydrogen phosphate, and potassium dihydrogen phosphate.

[0050] The liquid pharmaceutical formulation of the present invention may contain pharmaceutically permissible organic solvents (such as ethanol), collagen, polyvinyl alcohol, polyvinylpyrrolidone, carboxyvinyl polymers, sodium carboxymethyl cellulose, sodium polyacrylate, sodium alginate, water-soluble polyglucan, sodium carboxymethyl starch, pectin, methylcellulose, ethylcellulose, xanthan gum, gum arabic, casein, gelatin, agar, diglycerides, propylene glycol, polyethylene glycol, petrolatum, paraffin, stearyl alcohol, stearic acid, human serum albumin (HSA), mannitol, sorbitol, lactose, PBS, sodium chloride, sugars, biodegradable polymers, serum-free culture medium, and additives permitted as pharmaceutical additives.

[0051] The method of administration of the treatment agent of the present invention is preferably non-oral administration. Examples of routes of administration include intravenous, intra-arterial, intramuscular, intraperitoneal, subcutaneous, intraocular, and intramedullary, with intravenous administration being preferred. Examples of methods of administration include administration via syringe or intravenous drip.

[0052] There are no particular limitations on the container for filling liquid pharmaceutical preparations, but materials with low oxygen permeability are preferred. Examples include plastic containers, glass containers, and bags made of laminated films.

[0053] The treatment agent of the present invention can also be used in combination with other active substances or treatment methods that are useful for treating cancer in the subject. As treatment methods, it can be used in combination with physical therapies such as radiotherapy and particle beam therapy, surgical treatments such as surgery, chemotherapy, molecular targeted therapy, and cancer immunotherapy. As other active substances, it can be used in combination with chemotherapeutic agents used in chemotherapy, molecularly targeted therapeutic agents used in molecular targeted therapy, cell preparations or antibody preparations used in cancer immunotherapy, immune checkpoint inhibitors, etc. Examples of chemotherapeutic agents include, for example, alkylating agents, antimetabolites, antitumor antibiotics, alkaloids, hormone therapy agents, platinum complexes, topoisomerase inhibitors, and microtubule agonists.

[0054] (Dosage) The dosage of topotecan or its salt contained in the liposomes of the treatment agent of the present invention is preferably 0.1 mg / m² body surface area to 10 mg / m² body surface area per administration, calculated as topotecan. More preferably, it is 0.5 mg / m² body surface area to 5 mg / m² body surface area, and even more preferably, it is 1.0 mg / m² body surface area to 3.5 mg / m² body surface area.

[0055] It is preferable that the treatment agent of the present invention is administered once every 1 to 8 weeks, repeated multiple times. More preferably, it is administered once every 1 to 6 weeks, even more preferably, it is administered once every 1 to 4 weeks, and most preferably, it is administered once every 2 weeks.

[0056] When administering the treatment agent of the present invention once, it is preferable to administer it by infusion over a period of 5 minutes to 360 minutes. More preferably, it is administered over a period of 5 minutes to 240 minutes, even more preferably, over a period of 10 minutes to 120 minutes, and most preferably, over a period of 30 minutes to 120 minutes.

[0057] Regarding the dosage of topotecan or its salts contained in the treatment agent of the present invention, for example, it is calculated as approximately 0.1 mg / m² body surface area, approximately 0.5 mg / m² body surface area, approximately 1.0 mg / m² body surface area, approximately 1.5 mg / m² body surface area, approximately 2.0 mg / m² body surface area, approximately 2.5 mg / m² body surface area, approximately 2.6 mg / m² body surface area, approximately 3.0 mg / m² body surface area, approximately 3.5 mg / m² body surface area, approximately 4.0 mg / m² body surface area, etc. The following are considered optimal levels of body surface area: approximately 4.5 mg / m², approximately 5.0 mg / m², approximately 5.5 mg / m², approximately 6.0 mg / m², approximately 6.5 mg / m², approximately 7.0 mg / m², approximately 7.5 mg / m², approximately 8.0 mg / m², approximately 8.5 mg / m², approximately 9.0 mg / m², approximately 9.5 mg / m², and approximately 10 mg / m². More preferably, the concentrations are approximately 0.5 mg / m², approximately 1.0 mg / m² body surface area, approximately 1.5 mg / m² body surface area, approximately 2.0 mg / m² body surface area, approximately 2.5 mg / m² body surface area, approximately 2.6 mg / m² body surface area, approximately 3.0 mg / m² body surface area, approximately 3.5 mg / m² body surface area, and approximately 5.0 mg / m² body surface area; even more preferably, the concentrations are approximately 1.0 mg / m² body surface area and approximately 1.5 mg / m² body surface area. Approximately 2.0 mg / m² body surface area, approximately 2.5 mg / m² body surface area, approximately 2.6 mg / m² body surface area, approximately 3.0 mg / m² body surface area, approximately 3.5 mg / m² body surface area, and preferably approximately 1.0 mg / m² body surface area, approximately 1.5 mg / m² body surface area, approximately 2.0 mg / m² body surface area, approximately 2.5 mg / m² body surface area, approximately 2.6 mg / m² body surface area, and approximately 3.5 mg / m² body surface area. [Example]

[0058] The present invention will be further described in detail by way of the following embodiments, but the present invention is not limited to these embodiments.

[0059] <Preparation of a liquid pharmaceutical formulation containing liposomes containing topotecan> Referring to Patent Document 1 (International Publication No. 2018 / 181963), a liquid pharmaceutical formulation containing liposomes containing topotecan with the following composition (hereinafter referred to as Formulation A) was prepared. Topotecan hydrochloride 3.0 mg / mL (6.5 mmol) DHSM (Note 1) 10.4 mg / mL DSPE-MPEG2000 (Note 2) 3.6 mg / mL Cholesterol 3.6 mg / mL Ammonium sulfate 0.9 mg / mL (6.9 mmol) Sucrose appropriate amount L-histidine appropriate amount Sodium chloride appropriate amount Water (solvent) appropriate amount (Note 1) Dihydrosphingomyelin prepared by chemical synthesis in a manner that contains 98% or more of compound 1 having long-chain alkyl groups having carbons of 16 and 18. (Note 2) 1,2-Distearatel-sn-glycerol-3-phosphate ethanolamine-N-(methoxy(polyethylene glycol)-2000)

[0060] <Physical properties of formulation A> The pH of formulation A is 7.4, and the particle size of the liposomes contained in formulation A, calculated as the cumulative average particle size, is 91 nm. Furthermore, the molar ratio of sulfate ions to topotecan hydrochloride contained in the aqueous phase is 1.05.

[0061] <Reference Example 1: Predicting Appropriate Human Dosage Based on Non-Clinical Trial> Preparation A was diluted to 0.1, 0.2, and 0.4 mg / mL using 5% glucose solution, and administered intravenously to 15 male and 15 female SD mice (Charles River Laboratories Japan, Inc.) (30 mice in total) at doses of 0.5, 1, and 2 mg / kg (3, 6, and 12 mg / m²) at four weekly intervals (4 weeks). Each group was assigned a TK group (12 males and 12 females). In the groups with doses below 1 mg / kg, no deaths caused by Preparation A occurred during the trial period. Furthermore, the target organs for the toxicity of Preparation A were the hematopoietic, lymphatic, and digestive systems. In the group with a dose of 2 mg / kg, deaths or near-death were observed during the administration period and on the second day after the administration. In the groups with doses of Preparation A above 1 mg / kg, anemia and neutropenia caused by dose-responsive myelosuppression were confirmed. Furthermore, decreased lymphocytes, lymphocyte depletion in the spleen, thymus, and lymph nodes, necrosis of the gastrointestinal epithelium, hyperplasia of small intestinal glands, and depletion of hematopoietic cells in the bone marrow were observed, which were considered to be changes corresponding to the cell proliferation inhibition effect of preparation A. These changes all showed reversibility after a 4-week recovery period. On the other hand, no changes caused by preparation A were observed in the group treated with a dose of 0.5 mg / kg. Therefore, the maximum tolerated dose in mice was defined as 1 mg / kg (6 mg / m²) at which no deaths were confirmed, and the initial human dose was set at approximately one-tenth of the maximum tolerated dose, i.e., 1.0 mg / m².

[0062] <Reference Example 2: Relationship between toxicity and blood dynamics (toxicokinetics)> When the maximum tolerated dose of preparation A obtained in Reference Example 1, i.e., 1 mg / kg, was administered intravenously to mice, the total plasma exposure to topotecan was 28,400 ng / mL (Cmax) and 563,000 h·ng / mL (AUC0-96), while the exposure at a dose of 0.5 mg / kg for which no toxicity was confirmed was 11,000 ng / mL (Cmax) and 491,000 h·ng / mL (AUC0-96).

[0063] <Reference Example 3: Changes in Toxicity Curve over Time after Administration> Preparation A was diluted to 0.05, 0.1, and 0.2 mg / mL with 5% glucose solution, and administered intravenously to six male SD rats (Charles River Laboratories Japan, Inc.) at doses of 0.25, 0.5, and 1 mg / kg (1.5, 3, and 6 mg / m²). Blood samples were collected on days 1, 3, 5, 7, 10, 14, and 21 after administration for hematological examination, food intake measurement, and body weight measurement. No deaths or near-death experiences were confirmed in any of the doses. In the 1 mg / kg group, low values ​​in the erythrocyte and leukocyte systems persisted until day 14 after administration, showing a tendency to recover from day 10. Suppression of weight gain persisted until day 5 after administration, recovering after day 10. In the groups with doses below 0.5 mg / kg, the changes were milder and recovered more quickly compared to the 1 mg / kg group. Therefore, it can be concluded that when rats received a single intravenous administration of 1 mg / kg, the changes in the target organs of toxicity of formulation A—namely the hematopoietic, lymphatic, and digestive systems—were confirmed to have recovered by day 14.

[0064] <Reference Example 4: Predicting an Appropriate Human Dosing Schedule Based on Non-Clinical Trials> Based on the TK (Toxicokinetics) data of mice obtained in Reference Example 2, total topotecan exposure in humans was calculated using total pharmacokinetic analysis (PPK). The total topotecan clearance per body weight was calculated to be 1.86 mL / h / kg (mouse) based on the PPK model. When the human clearance was fitted using the power of body weight (CL=a*BWb), the human clearance for a patient weighing 70 kg was calculated to be 113 mL / h or 1.61 mL / h / kg body weight. This predicted clearance is approximately 100 times lower than the clearance of topotecan administered intravenously, which is 18.6 L / hr (Reference Mould et al. 2002, Ait-Oudhia, Mager and Straubinger 2014). Using the human clearance rate calculated by the PPK model, and simulating a dosing of formulation A in humans at a dose between 1 and 12 mg / m², the total t1 / 2 of topotecan was 18.5 hours (90% confidence interval: 13.2–24.6 hours), which is 9 times longer than the clearance rate when topotecan is administered intravenously (reference: HYCAMTIN, appendix). At the 2-week dosing interval, there was no accumulation between 1 and 12 mg / m², indicating a steady state. Based on these results, and considering the decrease in clearance rate and the increase in t1 / 2 based on liposomalization, dosing formulation A once every 2 weeks is predicted to be appropriate. Furthermore, in the mouse studies of Reference Example 3, it was confirmed that the changes caused by toxicity recovered within 2 weeks after administration; from this perspective, dosing once every 2 weeks is also predicted to be appropriate.

[0065] <Example: Drug Administration Trial> Based on the dosage predicted by Reference Example 1, Agent A was used in the treatment shown in Examples 1 and 2 below. The treatment was conducted at HonorHealth Research Institute in Scodale, Arizona, USA; Sarah Cannon Research Institute in Denver, Colorado, USA; University of Texas MD Anderson Cancer Center in Shulston, Texas, USA; and Dana Farber Cancer Institute in Boston, Massachusetts, USA.

[0066] Repeat the dosing cycle of administering Agent A to cancer patients once every 2 weeks. Specifically, Agent A is administered on day 1 and day 15 of a 28-day cycle, and the cycle consisting of these 28 days is repeated.

[0067] Treatment efficacy was determined using the following criteria. Subjects were evaluated using imaging diagnostics based on CT (Computed tomography) or MRI (Magnetic Resonance Imaging), and the following criteria were used for determination: CR (Complete Response): The tumor has completely disappeared. PR (Partial Response): The tumor size has decreased by more than 30% compared to the total size before medication. PD (Progressive Disease): The tumor size has increased by more than 20% and the absolute value has increased by more than 5 mm compared to the total size of the smallest tumor during the course of the disease, or a new lesion has appeared. SD (Stable Disease): The tumor size has not decreased to the same extent as PR and has not increased to the same extent as PD compared to the total size of the smallest tumor during the course of the disease. In addition, since the purpose of chemotherapy for solid cancer is to alleviate symptoms and prolong life, even if the treatment effect is SD, it can be judged that the drug is effective.

[0068] 1. A Merkel cell carcinoma patient who received topotecan at a dose of 2.0 mg / m² with each dose of formulation A was confirmed to have partial remission (PR) and continued treatment for approximately 32 weeks. This patient had previously received pembrolizumab-based epotazumab therapy. The patient was 62 years old and male.

[0069] The treatment agent of the present invention can achieve excellent preventive or therapeutic effects against Merkel cell carcinoma. Specifically, it has the effect of reducing the volume of Merkel cell carcinoma or maintaining the size of Merkel cell carcinoma. From these results, the treatment agent of the present invention is expected to prolong the patient's progression-free survival or overall survival, and has a very useful effect from the viewpoint of improving the patient's quality of life (QOL).

[0070] The therapeutic effect on Merkel cell carcinoma patients was confirmed by CT-based image diagnosis. The results are shown in Figure 1. Figure 1a shows the baseline image before administration of agent A. Figure 1b shows the CT image confirming PR 8 weeks after administration. Figure 1c shows the CT image confirming PR continued 16 weeks after administration. As shown in Figure 1, agent A showed excellent efficacy in the treatment of Merkel cell carcinoma. [Simplified Explanation of the Diagram]

[0014] Figure 1 a-c series represents CT images used to confirm the therapeutic effect on Merkel cell carcinoma patients.

Claims

1. Use of a liposome composition for manufacturing a treatment agent for Merkel cell carcinoma, the liposome composition comprising liposomes having an inner aqueous phase and an aqueous solution having an outer aqueous phase of dispersed liposomes, wherein the liposomes contain topotecan or a salt thereof, the lipids constituting the liposomes comprising polyethylene glycol-modified lipids, dihydrosphingomyelin and cholesterol, and the inner aqueous phase containing an ammonium salt, the treatment agent being administered by once at a dose of 1.0 mg / m² body surface area to 3.5 mg / m² body surface area, calculated as topotecan, and repeated several times every 2 weeks.

2. As claimed in claim 1, wherein the dihydrosphingomyelin is a dihydrosphingomyelin having alkyl groups having 16 carbons and 18 carbons.

3. As claimed in claim 1 or 2, wherein the ammonium salt is ammonium sulfate, and the ratio of sulfate ions contained in the aqueous phase to the total moles of topotecan or its salt contained in the treatment agent is 0.36 or more.

4. As claimed in claim 1 or 2, wherein the lipid modified by polyethylene glycol is a diacylphospholipid ethanolamine modified by polyethylene glycol or methoxy polyethylene glycol.

5. As claimed in paragraph 1 or 2, wherein the ratio of cholesterol to the total lipids constituting the liposome is 35 to 43 moles.

6. For the purposes of request item 1 or 2, wherein the pH of the external aqueous phase is 5.5 to 8.

5.

7. As requested in item 1 or 2, wherein the route of administration is intravenous.

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