Pharmaceutical preparations

Abstract

A formulation comprising dantrolene or a pharma- ceutically acceptable salt thereof and cyclodextrin in a molar ratio of 1:3 to 1:12, and also comprising polyethylene glycol (PEG) having an average molecular weight in the range of 1500 to 6000.

Description

[Technical field]

[0001] The present invention relates to improved formulations of dantrolene. More particularly, but not exclusively, the present invention relates to improved dantrolene formulations having improved solubility, among other advantages. [Background technology]

[0002] Dantrolene (1-({[5-(4-nitrophenyl)furan-2-yl]methylidene}amino)imidazol-idine-2,4-dione), commonly used in its sodium salt form, dantrolene sodium, is a skeletal muscle relaxant used to relieve chronic severe spasticity and malignant hyperthermia. Malignant hyperthermia is an inherited sensitivity of skeletal muscle to volatile anesthetics and depolarizing neuromuscular blocking drugs used in general anesthesia. In susceptible individuals, these drugs can induce a dramatic and uncontrolled increase in skeletal oxidative metabolism, overwhelming the body's ability to supply oxygen, remove carbon dioxide, and regulate body temperature, ultimately leading to circulatory collapse and death if not promptly treated.

[0003] Dantrolene exerts its effects on skeletal muscle by affecting calcium efflux, decreasing excitation-contraction coupling in muscle cells and causing a decrease in the force of the contractile process.

[0004] Dantrolene (as dantrolene sodium) is also in development for the treatment of other conditions, including acute radiation syndrome in patients with hematopoietic syndrome exposed to high doses of radiation, psychostimulant-induced intoxication (MDMA and methamphetamine intoxication), exertional heat stroke, concussion and other forms of traumatic brain injury, nerve agent-induced encephalopathy, and coronavirus disease (COVID-19).

[0005] Dantrolene is a good skeletal muscle relaxant, but its pharmacological effect is limited because it is poorly soluble in water.This poor solubility causes difficulties in preparing a solution suitable for intravenous administration and the need to administer a large volume of solution in a short time to deliver an effective dose.Poor solubility also affects the pharmacologic acceptable salt of dantrolene, which, when in solution, gradually precipitates in the form of free acid, making the solution unacceptable for injection.

[0006] Cyclodextrins are cyclic oligosaccharides consisting of a ring of glucose subunits linked by α-1,4 glycosidic bonds. Cyclodextrins have a variety of applications in the food and pharmaceutical industries, including in terms of drug delivery and stabilization.

[0007] WO 2018 / 146187 describes a pharmaceutical formulation comprising a complex of dantrolene or a salt thereof with cyclodextrin. However, the authors of WO 2018 / 146,187 found that the addition of further compounds to the formulation reduced the solubility of dantrolene.

[0008] Thus, there remains a need to provide formulations of dantrolene and its salts that have improved solubility in aqueous media, thus facilitating administration of the drug to patients in need thereof. Summary of the Invention

[0009] According to a first aspect, the present invention provides a formulation comprising dantrolene or a pharma- ceutically acceptable salt thereof and cyclodextrin in a molar ratio of 1:3 to 1:12, and also comprising polyethylene glycol (PEG) having an average molecular weight in the range of 1500 to 6000.

[0010] According to a second aspect of the present invention there is provided a dry formulation prepared by drying the liquid formulation described herein.

[0011] According to a third aspect of the present invention, there is provided a dry preparation comprising 100-130 mg of dantrolene sodium, 3000-4000 mg of 2-hydroxypropyl-β-cyclodextrin, and 350-450 mg of PEG3350.

[0012] According to a fourth aspect of the present invention, there is provided a liquid formulation prepared by dissolving the dry formulation described herein in a pharma- ceutically acceptable solvent.

[0013] According to a fifth aspect of the present invention, there is provided an aqueous solution comprising dantrolene or a pharma- ceutically acceptable salt thereof and cyclodextrin in a molar ratio of 1:3 to 1:12, and also comprising PEG having an average molecular weight in the range of 1500 to 6000.

[0014] According to a sixth aspect of the present invention, there is provided an aqueous solution comprising: (i) 6 mg / mL dantrolene sodium hemi-heptahydrate equivalent; (ii) 176.5 mg / mL 2-hydroxypropyl-β-cyclodextrin; and (iii) 20 mg / ml PEG3350.

[0015] According to a seventh aspect of the present invention, there is provided an aqueous solution comprising: (i) 5.3 mg / mL dantrolene sodium hemi-heptahydrate equivalent; (ii) 156.2 mg / mL 2-hydroxypropyl-β-cyclodextrin; and (iii) 17.7 mg / ml PEG3350.

[0016] According to an eighth aspect of the present invention, there is provided a vial comprising: (i) 101 mg of anhydrous dantrolene sodium (equivalent to 120 mg of dantrolene sodium hemi-heptahydrate); (ii) 3.530 g of 2-hydroxypropyl-β-cyclodextrin; and (iii) 400 mg of PEG3350.

[0017] According to a ninth aspect of the invention there is provided a formulation, solution or vial as described herein for use as a medicament.

[0018] According to a tenth aspect of the invention there is provided a formulation, solution, or vial as described herein for use in the treatment of malignant hyperthermia.

[0019] It will of course be understood that features described in relation to one aspect of the invention may be incorporated in other aspects of the invention, for example, formulations of the invention may incorporate any of the features described with reference to compositions and methods of the invention, and vice versa. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The present invention relates to a formulation comprising a pharma- ceutically acceptable salt of dantrolene and a cyclodextrin in a molar ratio of 1:3 to 1:12, and also comprising PEG having an average molecular weight in the range of 1500-6000.

[0021] The present invention relates to improved formulations of dantrolene. In particular, the present invention is based on the surprising discovery that the inclusion of cyclodextrin and polyethylene glycol (PEG) of the recited molecular weight range results in a formulation that has good solubility of dantrolene and also has other beneficial properties in aqueous solution. The achievement of both of these properties is particularly surprising. Previous disclosures have reported that while cyclodextrin can improve the solubility of dantrolene or its salts, the inclusion of additional components has a strong adverse effect, negating the improved solubility. The formulations of the present invention simultaneously achieve good solubility and other beneficial properties in aqueous solution.

[0022] In particular, the inclusion of PEG in the recited molecular weight range in the formulation of the present invention reduces or prevents foaming when the aqueous solution of the formulation is stirred. This provides the additional benefit of shortening the time required to make the solutions described herein "ready for injection". Stirring is generally required when the formulation (which is generally a dry formulation) is mixed with an aqueous solvent to convert it to a liquid form before use. This is important in clinical situations where dantrolene is commonly used (e.g., treatment of malignant hyperthermia), where rapidity of drug preparation and administration is important.

[0023] Thus, in another aspect of the present invention, there is provided a use of PEG for reducing foaming in a formulation during stirring, said formulation comprising (i) dantrolene or a pharma- ceutically acceptable salt thereof, and (ii) a cyclodextrin, wherein the solubility of dantrolene in said formulation further comprising PEG is not decreased compared to the solubility of dantrolene in said formulation without PEG.In a further aspect, there is provided a PEG for use in reducing foaming in a formulation during stirring, said formulation comprising (i) dantrolene or a pharma- ceutically acceptable salt thereof, and (ii) a cyclodextrin, wherein the solubility of dantrolene in said formulation further comprising PEG is not decreased compared to the solubility of dantrolene in said formulation without PEG. In a further aspect, a method is provided for reducing foaming in a formulation during stirring, the formulation comprising (i) dantrolene or a pharma- ceutically acceptable salt thereof, and (ii) a cyclodextrin, the method comprising adding PEG to the formulation, wherein the solubility of dantrolene in the formulation further comprising PEG is not decreased compared to the solubility of dantrolene in the formulation without PEG. In another aspect, a method is provided for preparing an aqueous formulation, the method comprising the steps of (i) providing a dry formulation comprising dantrolene or a pharma- ceutically acceptable salt thereof, a cyclodextrin, and PEG, (ii) mixing the dry formulation with an aqueous solvent, and (iii) stirring the mixture to convert the dry formulation to an aqueous form, wherein the presence of PEG reduces foaming during stirring of the mixture compared to a comparable formulation without PEG, and the solubility of dantrolene in the formulation with PEG is not decreased compared to the solubility of dantrolene in the comparable formulation without PEG. In the aspects of the invention described in this paragraph, dantrolene, cyclodextrin and PEG may be defined as described elsewhere herein.Therefore, in another aspect of the present invention, there is provided a use of PEG having an average molecular weight in the range of 1500 to 6000 to reduce foaming in a formulation during stirring, wherein the formulation comprises (i) dantrolene or a pharma- ceutically acceptable salt thereof, and (ii) a cyclodextrin, wherein the dantrolene and the cyclodextrin are present in the formulation in a molar ratio of 1:3 to 1:12, and the solubility of dantrolene in the formulation further comprising PEG is not reduced compared to the solubility of dantrolene in the formulation not comprising PEG. In a further aspect, there is provided a PEG having an average molecular weight in the range of 1500 to 6000 for use in reducing foaming in a formulation during agitation, wherein the formulation comprises (i) dantrolene or a pharma- ceutically acceptable salt thereof, and (ii) a cyclodextrin, wherein the dantrolene and the cyclodextrin are present in the formulation in a molar ratio of 1:3 to 1:12, and wherein the solubility of dantrolene in the formulation further comprising the PEG is not reduced compared to the solubility of dantrolene in the formulation not comprising the PEG. In a further aspect, there is provided a method for reducing foaming in a formulation during stirring, wherein the formulation comprises (i) dantrolene or a pharma- ceutically acceptable salt thereof, and (ii) a cyclodextrin, wherein the dantrolene and the cyclodextrin are present in the formulation in a molar ratio of 1:3 to 1:12, and the method comprises adding PEG having an average molecular weight in the range of 1500 to 6000 to the formulation, and wherein the solubility of dantrolene in the formulation further comprising the PEG is not reduced compared to the solubility of dantrolene in the formulation not comprising the PEG.In another aspect, a method of preparing an aqueous formulation is provided, comprising: (i) providing a dry formulation comprising: (a) dantrolene or a pharma- ceutically acceptable salt thereof; (b) a cyclodextrin, wherein the dantrolene and the cyclodextrin are present in the formulation in a molar ratio of 1:3 to 1:12; and (c) a PEG having an average molecular weight in the range of 1500 to 6000; (ii) mixing the dry formulation with an aqueous solvent; and (iii) stirring the mixture to convert the dry formulation to an aqueous form, wherein the presence of PEG reduces foaming during stirring of the mixture compared to an equivalent formulation not containing PEG, and the solubility of dantrolene in the formulation containing PEG is not reduced compared to the solubility of dantrolene in an equivalent formulation not containing PEG. In the aspects of the invention described in this paragraph, the formulation, dantrolene, cyclodextrin, and / or PEG may be further defined as described elsewhere herein.

[0024] In another aspect of the present invention, there is provided a use of PEG for reducing foaming in a formulation during stirring, said formulation comprising (i) dantrolene or a pharma- ceutically acceptable salt thereof, and (ii) a cyclodextrin, wherein the solubility of dantrolene in said formulation further comprising PEG is increased compared to the solubility of dantrolene in a comparable formulation comprising PEG but not cyclodextrin.In a further aspect, there is provided a PEG for use in reducing foaming in a formulation during stirring, said formulation comprising (i) dantrolene or a pharma- ceutically acceptable salt thereof, and (ii) a cyclodextrin, wherein the solubility of dantrolene in said formulation further comprising PEG is increased compared to the solubility of dantrolene in a comparable formulation comprising PEG but not cyclodextrin. In a further aspect, a method is provided for reducing foaming in a formulation during stirring, the formulation comprising (i) dantrolene or a pharma- ceutically acceptable salt thereof, and (ii) a cyclodextrin, the method comprising adding PEG to the formulation, whereby the solubility of dantrolene in the formulation further comprising PEG is increased compared to the solubility of dantrolene in a comparable formulation comprising PEG but not comprising cyclodextrin. In another aspect, a method is provided for preparing an aqueous formulation, the method comprising the steps of (i) providing a dry formulation comprising dantrolene or a pharma- ceutically acceptable salt thereof, cyclodextrin, and PEG, (ii) mixing the dry formulation with an aqueous solvent, and (iii) stirring the mixture to convert the dry formulation to an aqueous form, the presence of PEG reduces foaming during stirring of the mixture compared to a comparable formulation not containing PEG, and the solubility of dantrolene in the formulation comprising PEG is increased compared to the solubility of dantrolene in a comparable formulation comprising PEG but not comprising cyclodextrin. In the aspects of the invention described in this paragraph, the agent, dantrolene, cyclodextrin and / or PEG may be defined as described elsewhere herein.Therefore, in another aspect of the present invention, there is provided a use of PEG having an average molecular weight in the range of 1500 to 6000 to reduce foaming in a formulation during stirring, wherein the formulation comprises (i) dantrolene or a pharma- ceutically acceptable salt thereof, and (ii) a cyclodextrin, wherein the dantrolene and the cyclodextrin are present in the formulation in a molar ratio of 1:3 to 1:12, and the solubility of dantrolene in the formulation further comprising the PEG is improved compared to the solubility of dantrolene in an equivalent formulation comprising PEG but not cyclodextrin. In a further aspect, there is provided a PEG having an average molecular weight in the range of 1500 to 6000 for use in reducing foaming in a formulation during agitation, wherein the formulation comprises (i) dantrolene or a pharma- ceutically acceptable salt thereof, and (ii) a cyclodextrin, wherein the dantrolene and the cyclodextrin are present in the formulation in a molar ratio of 1:3 to 1:12, and wherein the solubility of dantrolene in the formulation further comprising the PEG is improved compared to the solubility of dantrolene in an equivalent formulation comprising PEG but not cyclodextrin. In a further aspect, there is provided a method for reducing foaming in a formulation during stirring, wherein the formulation comprises (i) dantrolene or a pharma- ceutically acceptable salt thereof, and (ii) a cyclodextrin, wherein the dantrolene and the cyclodextrin are present in the formulation in a molar ratio of 1:3 to 1:12, and the method comprises adding PEG having an average molecular weight in the range of 1500 to 6000 to the formulation, wherein the solubility of dantrolene in the formulation further comprising the PEG is improved compared to the solubility of dantrolene in an equivalent formulation comprising PEG but not cyclodextrin.In another aspect, a method of preparing an aqueous formulation is provided, comprising: (i) providing a dry formulation comprising: (a) dantrolene or a pharma- ceutically acceptable salt thereof; (b) a cyclodextrin, wherein the dantrolene and the cyclodextrin are present in the formulation in a molar ratio of 1:3 to 1:12; and (c) a PEG having an average molecular weight in the range of 1500 to 6000; (ii) mixing the dry formulation with an aqueous solvent; and (iii) stirring the mixture to convert the dry formulation to an aqueous form, wherein the presence of PEG reduces foaming during stirring of the mixture compared to an equivalent formulation not containing PEG, and the solubility of dantrolene in the formulation containing PEG is increased compared to the solubility of dantrolene in an equivalent formulation containing PEG but not cyclodextrin. In the aspects of the invention described in this paragraph, the formulation, dantrolene, cyclodextrin and / or PEG may be further defined as described elsewhere herein. Improved solubility of dantrolene can be defined as a dantrolene solubility of at least 0.3 mg / ml, at least 0.33 mg / ml, at least 0.5 mg / ml, at least 1 mg / ml, at least 1.5 mg / ml, at least 2 mg / ml, at least 2.5 mg / ml, at least 3 mg / ml, at least 3.5 mg / ml, at least 4 mg / ml, at least 4.5 mg / ml, at least 5 mg / ml, at least 5.3 mg / ml or at least 5.5 mg / ml, for example, a hemi-heptahydrate equivalent of about 6 mg / ml in the formulations described herein (e.g., aqueous formulations).The improvement in dantrolene solubility can be achieved by administering the following to the patient in the formulation described herein (e.g., aqueous formulation): 0.4 mg / ml to 10 mg / ml, 0.5 mg / ml to 10 mg / ml, 1 mg / ml to 10 mg / ml, 1.5 mg / ml to 10 mg / ml, 2 mg / ml to 10 mg / ml, 2.5 mg / ml to 10 mg / ml, 3 mg / ml to 10 mg / ml, 3.5 mg / ml to 10 mg / ml, 4 mg / ml to 10 mg / ml, 4.5 mg / ml to 10 mg / ml, 5 mg / ml to 10 mg / ml, 6 mg / ml to 10 mg / ml, 7 mg / ml to 10 mg / ml, 8 mg / ml to 10 mg / ml, 9 mg / ml to 10 mg / ml, 10 mg / ml to 10 mg / ml, 11 mg / ml to 10 mg / ml, 12 mg / ml to 10 mg / ml, 13 mg / ml to 10 mg / ml, 14 mg / ml to 10 mg / ml, 15 mg / ml to 10 mg / ml, 16 mg / ml to 10 mg / ml, 17 mg / ml to 10 mg / ml, 18 mg / ml to 10 mg / ml, 19 mg / ml to 20 mg / ml, 20 mg / ml to 20 mg / ml, 21 mg / ml to 20 mg / ml, 22 mg / ml to 20 mg / ml, 23 mg / ml to 20 mg / ml, 24 mg / ml to 20 mg / ml, 25 mg / ml to 20 mg / ml, 26 mg / ml to 20 mg / ml, 27 mg / ml to 20 mg / ml, 28 mg / ml to 20 mg / ml, In some embodiments, the solubility of dantrolene in the hemi-heptahydrate equivalent may be defined as a solubility of dantrolene in the hemi-heptahydrate equivalent of 0.5mg / ml to 10mg / ml, 5.3mg / ml to 10mg / ml, 5.5mg / ml to 10mg / ml, 0.5mg / ml to 8mg / ml, 0.5mg / ml to 7mg / ml, 0.5mg / ml to 6mg / ml, 1mg / ml to 7mg / ml, 1.5mg / ml to 7mg / ml, 2mg / ml to 7mg / ml, 2.5mg / ml to 7mg / ml, 3mg / ml to 7mg / ml, or 4mg / ml to 6mg / ml.

[0025] Furthermore, the formulations of the present invention also allow for the preparation of liquid formulations of dantrolene that reach higher concentrations and / or smaller reconstitution volumes, thus further facilitating rapid administration of the drug to patients.

[0026] The inventors have also found that there is no need to include pH adjusting or buffering components. The formulations described herein achieve the desired solubility and other beneficial effects without the need to include additional components that affect pH. Fewer components reduce the clinical precautions that may be required, simplify product regulatory considerations, and also simplify the manufacture and storage of the formulation.

[0027] Generally, for clinical use, dantrolene products are supplied in vials with instructions to add solvent immediately prior to use. The vial has a size appropriate for the volume of solvent to be added. A smaller reconstitution volume than can be achieved with current formulations means that smaller vials can be used, thus further reducing the required hospital storage space and reducing the cost of goods (CoG).

[0028] In the formulation of an active ingredient that is poorly soluble or dissolves slowly, it is common to micronize the active ingredient. The formulation of the present invention allows the use of dantrolene with a larger particle size than is common in the prior art. This also reduces the CoG of the formulation.

[0029] Dantrolene can exist in the form of the free acid, which is represented by the following structural formula: [ka]

[0030] More often, dantrolene is used in the form of a pharma- ceutically acceptable salt, such as the sodium salt. Dantrolene sodium may be represented by the following structural formula: [ka]

[0031] Formulations of dantrolene sodium exist in the art, for example DANTRIUM® IV 20 mg marketed by Norgine Pharmaceuticals Limited, Uxbridge, UK.

[0032] A pharma- ceutically acceptable salt of dantrolene refers to the deprotonated form of dantrolene and a cationic counterion. In one embodiment of the invention, the cationic counterion is selected from the group of alkali metal, alkaline earth metal, ammonium, alkylammonium, polyalkylammonium, arylammonium, substituted or unsubstituted quinolizinium, and substituted or unsubstituted pyridinium.

[0033] In one embodiment of the invention, pharma- ceutically acceptable salts of dantrolene refer to salts of dantrolene in which the cationic counterion to the dantrolene anion is preferably selected from the group consisting of sodium, potassium, ammonium, calcium, magnesium, and ammonium salts of physiologically acceptable amino compounds, in particular arginine, lysine, meglumine, tromethamine, choline, benzyltrimethylammonium, tetramethylammonium, N-methylpyridinium, tetrabutylammonium, 2-(2,3-dihydroxy-1-proylamino)-quinolizinium, quinolizinium, 2-carbonyl-1-methylpyridinium, 2,3-dimethyl-1-phenyl-4-trimethyl-ammonium-3-pyrazolin-5-one, dimethylammonium, 1,3-dimethylimidazolium, and 2-(1-hydroxy-2-methyl)propyltrimethylammonium.

[0034] In one embodiment of the present invention, the pharma- ceutically acceptable salt of dantrolene refers to a salt of dantrolene in which the cationic counterion to the dantrolene anion is selected from the group consisting of sodium, potassium, ammonium, calcium and magnesium. In a preferred embodiment of the present invention, the pharma-ceutically acceptable salt of dantrolene refers to a salt of dantrolene in which the cationic counterion to the dantrolene anion is sodium, i.e., the sodium salt of dantrolene (also called dantrolene sodium). In a particularly preferred embodiment of the present invention, the pharma-ceutically acceptable salt of dantrolene is the hemi-heptahydrate of the sodium salt (i.e., dantrolene sodium hemi-heptahydrate).

[0035] Dantrolene active pharmaceutical ingredient (API), e.g., dantrolene sodium or dantrolene sodium hemi-heptahydrate, included in embodiments of the present invention may be optionally micronized to a particular particle size. In one embodiment, the formulation of the present invention contains dantrolene (e.g., dantrolene sodium) in a particle size of 70 μm or less, e.g., 63 μm or less, or 40 μm or less. In one embodiment, the formulation of the present invention contains dantrolene (e.g., dantrolene sodium) in a particle size of 0.2-70 μm, e.g., 5-70 μm, 10-70 μm, 25-70 μm, or 35-70 μm. In one embodiment, the formulation of the present invention contains dantrolene (e.g., dantrolene sodium) in a particle size of 0.2-50 μm, e.g., 5-50 μm, 10-50 μm, 25-50 μm, or 35-50 μm. Preferably, the dantrolene, eg, dantrolene sodium, is present in a particle size of about 5 to about 40 μm. For example, the dantrolene, eg, dantrolene sodium, is present in a particle size of about 40 μm.

[0036] Cyclodextrins are cyclic oligosaccharides formed from (α-1,4)-linked glucose subunits. Cyclodextrins have a hydrophobic central cavity and a hydrophilic outer surface, and due to their truncated cone or torus, cyclodextrins can interact with molecules of appropriate size to form inclusion complexes. In one embodiment of the invention, the cyclodextrin in the formulations described herein can have 5-30, 5-20, 5-15, 5-10, 5-8, or 6-8 glucose subunits in the cyclic structure. Cyclodextrins with 6, 7, or 8 glucose subunits in the cyclic structure are known as α (alpha)-cyclodextrin, β (beta)-cyclodextrin, and γ (gamma)-cyclodextrin, respectively. In one embodiment of the invention, the cyclodextrin in the formulations described herein has 7 glucose subunits (i.e., β-cyclodextrin).

[0037] In one embodiment of the present invention, the glucose subunits of the cyclodextrin in the formulations described herein may be substituted. The substituents are independently selected from the group consisting of alkyl, hydroxyalkyl, carboxyalkyl, alkylcarbonyl, carboxyalkoxyalkyl, sulfoalkyl, alkylcarbonyloxyalkyl, and alkoxycarbonylalkyl. For example, the cyclodextrins described above may be selected from the group consisting of C 1~8 Alkyl group, C 1~6 Alkyl group, C 1~4 Alkyl group, C 1~8 Hydroxyalkyl group, C 1~6 Hydroxyalkyl group, C 1~4 Hydroxyalkyl group, C 1~8 Sulfoalkyl groups, C 1~6 Sulfoalkyl group or C 1~4 In another embodiment of the invention, the cyclodextrin in the formulations described herein is substituted with a C 1~8 Alkyl group, C 1~6 Alkyl group or C 1~4 It may be substituted with an alkyl group, which is itself substituted with a hydroxyl group or a sulfo group. In the above, the term "alkyl" should be understood to include both straight and branched chain hydrocarbon groups. A sulfo group refers to a -SO3H moiety or its corresponding pharma- ceutically acceptable salt. Preferred counterions are those defined herein as counterions for the pharma- ceutically acceptable salts of dantrolene.

[0038] The formulation according to one embodiment of the present invention comprises a cyclodextrin containing 5 to 10 glucose subunits, such as 6 to 8 glucose subunits, such as 7 glucose subunits, wherein the glucose subunits are optionally C 1~8The formulation according to one embodiment of the invention comprises a cyclodextrin containing 5 to 10 glucose subunits, such as 6 to 8 glucose subunits, such as 7 glucose subunits, wherein the glucose subunits are optionally C 1~4 The formulation according to one embodiment of the invention comprises a cyclodextrin containing 5 to 10 glucose subunits, for example 6 to 8 glucose subunits, for example 7 glucose subunits, wherein the glucose subunits are optionally substituted with methyl groups, C 1~4 Hydroxyalkyl group or C 1~4 The formulation according to one embodiment of the present invention comprises a cyclodextrin containing 5 to 10 glucose subunits, such as 6 to 8 glucose subunits, such as 7 glucose subunits, wherein the glucose subunits are optionally substituted with C 2~4 It is substituted with a hydroxyalkyl group. 2~4Specific examples of hydroxyalkyl groups include hydroxyethyl, hydroxypropyl, e.g., 2-hydroxypropyl, and hydroxybutyl. Thus, a formulation according to an embodiment of the invention includes a cyclodextrin containing 5-10 glucose subunits, e.g., 6-8 glucose subunits, e.g., 7 glucose subunits, wherein the glucose subunits are optionally substituted with 2-hydroxypropyl groups, e.g., 2-hydroxypropyl-β-cyclodextrin (HP-β-CD or HPBCD). Specific examples of 2-hydroxypropyl-β-cyclodextrin that may be used in the formulations of embodiments of the invention are Cavitron™ W7 (Ashland, Inc.) or Kleptose® HPB (Roquette). A specific example of a sulfoalkyl group is a sulfobutyl group. A specific example of a sulfoalkyl-substituted cyclodextrin that may be used in the formulation of embodiments of the invention is sulfobutylether-β-cyclodextrin (Captisol®, Ligand, San Diego, Calif., USA) as described in EP 2583668, the contents of which are incorporated herein by reference. A specific example of a methyl-substituted cyclodextrin that may be used in the formulation of embodiments of the invention is randomly methylated β-cyclodextrin (RM-β-CD or RMBCD) (Cavasol® W7 M, Wacker, or Kleptose® Crysmeb, Roquette).

[0039] A formulation according to one embodiment of the present invention comprises a cyclodextrin represented by formula I, [ka] In the formula, each substituent R is independently H, alkyl, hydroxyalkyl, carboxyalkyl, alkylcarbonyl, carboxyalkoxyalkyl, -C 1~10In one embodiment, each of the substituents R in formula I is independently selected from the group consisting of H, -CH2CH(CH3)OH, -(CH2)4SO3Na, CH3, glucosyl, hydroxyethyl, and maltosyl. In one embodiment, each of the substituents R in formula I is independently selected from the group consisting of H, -CH2CH(CH3)OH, -(CH2)4SO3Na, and hydroxyethyl. In a particularly advantageous embodiment, each of the substituents R in formula I is independently selected from the group consisting of H and -CH2CH(CH3)OH.

[0040] The degree of substitution of a cyclodextrin can be expressed in terms of average molar substitution, i.e., a measure of the average number of moles of all substituents per mole of glucose subunit. In one embodiment of the invention, the cyclodextrin of the formulation described herein has a molar substitution (MS) in the range of 0.05-10, e.g., 0.2-2, 0.25-1 or 0.5-0.8, e.g., about 0.65. In one embodiment of the invention, the cyclodextrin is a 2-hydroxypropyl-β-cyclodextrin having an MS of 0.4-1.5 or 0.2-0.9, e.g., 0.3-0.8, 0.5-0.7, or 0.58-0.68. Alternatively, the degree of substitution of a cyclodextrin can be expressed in terms of the average number of substituents per cyclodextrin molecule. In one embodiment of the invention, the cyclodextrin of the formulations described herein has an average of 4 to 8 substituents per cyclodextrin molecule, e.g., an average of 4 to 5, 4 to 6, 5 to 7, or 6 to 8 substituents per cyclodextrin molecule.

[0041] In the formulations of the invention, the pharma- ceutically acceptable salt of dantrolene and the cyclodextrin (e.g., dantrolene sodium and 2-hydroxypropyl-β-cyclodextrin) are present in a molar ratio of 1:3 to 1:12. In preferred formulations, the dantrolene and the cyclodextrin are present in a molar ratio of 1:5 to 1:10, such as 1:6 to 1:9.5, 1:6.7 to 1:9.1, or 1:7 to 1:9, such as 1:8 to 1:9 or 1:8.3 to 1:8.6.

[0042] In the formulations of the present invention, the polyethylene glycol (PEG) is a PEG that is solid at room temperature (20°C). For example, in the formulations of the present invention, the PEG has an average molecular weight in the range of 1500-6000. At room temperature (20°C), these PEGs are solid. For example, the PEG has an average molecular weight in the range of 2000-5000, such as 3000-4000. For example, the PEG may be PEG 3000, PEG 3350 or PEG 4000 as defined in the national pharmacopoeias, such as PEG 3350. Further examples of suitable PEGs recognized in the pharmacopoeias of some countries include macrogol, such as macrogol 4000. Optionally, the PEG used in the formulations of the present invention may comprise two or more different PEG compounds.

[0043] In certain embodiments of the formulation of the present invention, the amount of PEG may be expressed as a weight / weight ratio relative to the amount of cyclodextrin. For example, PEG may be present in an amount such that the weight / weight ratio of PEG to cyclodextrin is 1:2 to 1:50, such as 1:2 to 1:20. In one embodiment, PEG is present in an amount such that the weight / weight ratio of PEG to cyclodextrin is 1:3 to 1:15, such as 1:5 to 1:12. Preferably, the weight / weight ratio of PEG to cyclodextrin is 1:8 to 1:10, more preferably 1:8.5 to 1:9. When the cyclodextrin is 2-hydroxypropyl-β-cyclodextrin, e.g. HPBCD having an MS of 0.3 to 0.8 or 0.5 to 0.7, the PEG (e.g. PEG having an average molecular weight in the range of 3000 to 4000) is advantageously present in an amount such that the weight / weight ratio of PEG to cyclodextrin is 1:5 to 1:12 weight / weight relative to the amount of 2-hydroxypropyl-β-cyclodextrin, e.g. 1:8 to 1:10 or 1:8.5 to 1:9.

[0044] In certain embodiments of the formulations of the invention, the amount of PEG may be expressed as a weight / weight ratio relative to the amount of dantrolene. For example, PEG (e.g., PEG having an average molecular weight in the range of 3000-4000) may be present in an amount such that the weight / weight ratio of PEG to dantrolene is 1:0.1-1:10, e.g., 1:0.1-1:4 or 1:0.2-1:5. In one embodiment, PEG is present in an amount such that the weight / weight ratio of PEG to cyclodextrin is 1:0.2-1:4, e.g., 1:0.2-1:3.5.

[0045] Alternatively, in certain embodiments of the formulation of the invention, the amount of PEG may be expressed as a concentration in mg / mL. For example, PEG is present in a concentration of 0.5-50 mg / mL. For example, PEG is present in a concentration of 2.5-50 mg / mL, such as 5-50 mg / mL. In one embodiment, PEG is present in a concentration of 10-40 mg / mL, such as 15-30 mg / mL or 15-20 mg / mL. When the cyclodextrin is 2-hydroxypropyl-β-cyclodextrin, such as HPBCD with an MS of 0.3-0.8 or 0.5-0.7, PEG (e.g. PEG with an average molecular weight in the range of 3000-4000) is advantageously present in a concentration of 10-40 mg / mL, such as 15-30 or 15-20 mg / mL.

[0046] In certain embodiments of the formulations of the present invention, it is beneficial to include certain further components, such as pharmaceutical excipients and / or adjuvants well known in the art. The excipients and / or adjuvants may be provided, for example, with specifications as set out in the 2019 European Pharmacopeia (Ph.Eur.). Further examples of pharmaceutical excipients can be found in the Handbook of Pharmaceutical Excipients (9 th edition, 2020; Pharmaceutical Press (UK) and American Pharmaceutical Association (US).

[0047] For example, the formulation of the present invention may further include an antioxidant. An antioxidant may be included to enhance the stability of the formulation of the present invention by inhibiting deterioration due to oxidative processes. An exemplary antioxidant may include ascorbic acid. The formulation of the present invention may further include a solubilizer or crystallization inhibitor. A solubilizer or crystallization inhibitor may be included to maintain drug solubility and / or bioavailability. An exemplary solubilizer or crystallization inhibitor may include low molecular weight povidone, such as polyvinylpyrrolidone.

[0048] The formulation of the present invention may further comprise an osmotic agent. The osmotic agent may be included to ensure that the solution prepared from the formulation of the present invention has the desired osmolarity when mixed with the required volume of solvent. For example, it may be beneficial for the solution to be isotonic with blood, i.e., having an osmolarity of 270-300 mOsm / kg, particularly 285-290 mOsmol / kg. Exemplary osmotic agents include polyhydroxyalkanols having 2-10 carbon atoms, such as those selected from the group consisting of mannitol, fructose, glucose, gluconolactone, gluconate, sucrose, lactose, trehalose, dextrose, dextran, hydroxyethyl starch, and mixtures thereof. Further osmotic agents may be selected from the group consisting of glycine, gelatin, calcium gluconoglucoheptonate, potassium chloride, calcium chloride, sodium chloride, and mixtures thereof. A combination of osmotic agents can be utilized to ensure that solutions prepared from the formulations of the present invention are isotonic with blood when mixed with the required volume of solvent.

[0049] The formulations of the present invention may further include a pH adjuster. The pH adjuster may be included to ensure that the solution prepared from the formulation of the present invention has a desired pH when mixed with the required volume of solvent, for example, to improve stability, solubility, or compatibility with the desired route of administration. Exemplary pH adjusters may include acids, bases, or buffers, such as citric acid, tartaric acid, hydrochloric acid, sodium hydroxide, sodium acetate, sodium citrate, sodium carbonate, sodium bicarbonate, or calcium carbonate. As mentioned above, the inventors have found that for most purposes, pH adjusters are not required in the formulations of the present invention. The formulations described herein achieve the desired solubility and other beneficial effects without the need to include additional ingredients that affect pH. Nevertheless, in certain circumstances, pH adjusters may be added to achieve a particular pH.

[0050] In a preferred embodiment, the formulation of the present invention is a dry formulation.Dryness is beneficial for ensuring the long-term stability of the formulation of the present invention.Dry formulations also have the advantage of being light in weight (and therefore easy to transport) and small in volume.

[0051] The dry formulation can be obtained in dry form by any suitable means. For example, the dry formulation can be a lyophilized formulation. The lyophilized formulation can be prepared, for example, using a method including the steps of i) freezing, ii) optional annealing, iii) evacuation, (iv) primary drying, (v) secondary drying, (vi) capping with optional pre-venting with N2, and (vi) venting to atmospheric pressure with N2. Alternatively, the dry formulation can be an air-dried formulation.

[0052] In one embodiment, the present invention provides a lyophilized formulation comprising dantrolene sodium and 2-hydroxypropyl-β-cyclodextrin in a molar ratio of 1:6 to 1:9.5, and also comprising PEG having an average molecular weight in the range of 3000 to 4000, where on average, each 2-hydroxypropyl-β-cyclodextrin molecule is substituted with an average of 4 to 6 2-hydroxypropyl groups. For example, such a formulation comprises dantrolene sodium hemi-heptahydrate and 2-hydroxypropyl-β-cyclodextrin in a molar ratio of 1:8.3 to 1:8.6, and also comprising PEG3350, where on average, each 2-hydroxypropyl-β-cyclodextrin molecule is substituted with 5 2-hydroxypropyl groups.

[0053] As mentioned above, the present invention provides a liquid formulation prepared by dissolving the formulation according to the first claimed aspect of the invention in a pharma- ceutically acceptable solvent. The pharma- ceutically acceptable solvent for use in the liquid formulation may be, for example, water for injection, Ph Eur.

[0054] As also described above, the present invention provides an aqueous solution comprising a pharma- ceutically acceptable salt of dantrolene and a cyclodextrin in a molar ratio of 1:3 to 1:12, and also comprising PEG having an average molecular weight in the range of 1500 to 6000, at a concentration of 0.5 to 50 mg / mL. The present invention also provides an aqueous solution that may be prepared from any of the dry formulations disclosed herein via the addition of a suitable pharma- ceutically acceptable solvent.

[0055] In one embodiment, the liquid formulation, e.g., aqueous solution, according to the present invention comprises dantrolene, e.g., dantrolene sodium, in a concentration of 0.4-10 mg / mL. Preferably, the dantrolene, e.g., dantrolene sodium, is present in a concentration of 2-9 mg / mL, e.g., 4-8.5 mg / mL or 4-6.5 mg / mL. For example, the liquid formulation according to the present invention may contain dantrolene, e.g., dantrolene sodium, in a concentration of about 4.5, 5.05, 5.4, or 6 mg / mL. The aforementioned concentrations of dantrolene, e.g., dantrolene sodium, are expressed as anhydrous salt equivalents.

[0056] However, the above concentrations may also be expressed as dantrolene sodium 3.5 molar hydrate equivalents (i.e., hemi-heptahydrate equivalents), where 3.5 moles of hydrate indicates the presence of 3.5 water molecules per dantrolene molecule (i.e., 3.5 moles of water per mole of dantrolene or dantrolene sodium). The terms "hemi-heptahydrate equivalent" and "anhydrous salt equivalent" as used herein take into account the fact that anhydrous dantrolene sodium salt or dantrolene sodium hemi-heptahydrate salt dissociates when dissolved in solution. Thus, for example, when solvent is added to 6 mg of dantrolene sodium hemi-heptahydrate to a total volume of 1 mL, this produces a solution containing the equivalent of 6 mg / mL of dantrolene sodium hemi-heptahydrate.

[0057] By utilizing the respective molecular masses of the two compounds, it is possible to convert between the concentration of anhydrous dantrolene sodium and that of dantrolene sodium hemi-heptahydrate. For example, anhydrous dantrolene sodium at a concentration of 4.55 mg / mL (molecular mass 336.24 g / mol) is converted to 3.5 molar hydrate at a concentration of 5.4033 mg / mL (molecular mass 399.29 g / mol), and anhydrous dantrolene sodium at a concentration of 5.0525 mg / mL is converted to 3.5 molar hydrate at a concentration of 6 mg / mL. In one embodiment, a liquid formulation, e.g., an aqueous solution, according to the present invention contains dantrolene, e.g., dantrolene sodium hemi-heptahydrate, at a concentration of 0.4 to 10 mg / mL (expressed as hemi-heptahydrate equivalent). Preferably, the dantrolene, eg dantrolene sodium hemi-heptahydrate, is present in a concentration of 3-10 mg / mL, such as 4-8 mg / mL or 5-7 mg / mL, such as 6 mg / mL (all concentrations expressed as hemi-heptahydrate equivalents).

[0058] Alternatively, the concentration of dantrolene may be expressed as mmol / mL (millimoles per mL). Thus, in one embodiment, a liquid formulation, e.g., an aqueous solution, according to the invention contains dantrolene at a concentration of 0.001-0.05 mmol / mL, e.g., 0.005-0.025 mmol / mL or 0.01-0.020 mmol / mL. Preferably, dantrolene is present at a concentration of 0.012-0.016 mmol / mL, e.g., 0.013 mmol / mL or 0.015 mmol / mL. As can be easily calculated, a liquid formulation according to the invention containing dantrolene sodium at a concentration of 6 mg / mL hemi-heptahydrate equivalent (or 5.0525 mg / mL anhydrous equivalent) results in a dantrolene concentration of 0.015 mmol / mL.

[0059] In one embodiment, the liquid formulation according to the present invention comprises 2-hydroxypropyl-β-cyclodextrin present in a concentration of 100-300 mg / mL. Preferably, the 2-hydroxypropyl-β-cyclodextrin is present in a concentration of 100-200 mg / mL, such as 120-180 mg / mL or 150-180 mg / mL. More preferably, the concentration of the 2-hydroxypropyl-β-cyclodextrin is 176.5 mg / mL. Most preferably, the 2-hydroxypropyl-β-cyclodextrin is present in a concentration of 140-170 mg / mL or 150-160 mg / mL, such as 156.2 mg / mL. Preferably, 2-hydroxypropyl-β-cyclodextrin is present at a concentration of 100-200 mg / mL, such as 120-190 mg / mL, such as 150-185 mg / mL, such as 150-180 mg / mL, or such as 175-177 mg / mL. Preferably, the concentration of 2-hydroxypropyl-β-cyclodextrin is 176.5 mg / mL. Most preferably, 2-hydroxypropyl-β-cyclodextrin is present at a concentration of 140-170 mg / mL or 150-160 mg / mL, such as 156.2 mg / mL. As described herein, the pharma- ceutically acceptable salt of dantrolene and the cyclodextrin are present in the formulations described herein within certain molar ratio ranges, such as 1:3 to 1:12, 1:5 to 1:10, 1:6 to 1:9.5, 1:6.7 to 1:9.1, 1:7 to 1:9, 1:8 to 1:9, or 1:8.3 to 1:8.6.

[0060] In one embodiment the liquid formulation according to the invention comprises PEG, e.g. PEG 3350, present in a concentration of 0.5-50 mg / mL, such as 5-45 mg / mL, e.g. 10-40 mg / mL, or e.g. 10, 20, 30 or 40 mg / mL. Preferably the PEG, e.g. PEG 3350, is present in a concentration of 5-25 mg / mL, e.g. 10-25 mg / mL or 15-25 mg / mL, suitably 15-20 mg / mL. Preferably the PEG, e.g. PEG 3350, is present in a concentration of 17.7 mg / mL or 20 mg / mL.

[0061] In one embodiment, a liquid formulation, e.g., an aqueous solution, according to the present invention comprises dantrolene, e.g., dantrolene sodium, e.g., dantrolene sodium hemi-heptahydrate, present at a concentration of 0.4-10 mg / mL (expressed as dantrolene sodium hemi-heptahydrate equivalent), a cyclodextrin, e.g., 2-hydroxypropyl-β-cyclodextrin, present at a concentration of 100-300 mg / mL, and a PEG, e.g., PEG 3350, present at a concentration of 0.5-50 mg / mL. Preferably, a liquid formulation, e.g., an aqueous solution, according to the present invention comprises dantrolene, e.g., dantrolene sodium, e.g., dantrolene sodium hemi-heptahydrate, present at a concentration of 2-9 mg / mL (dantrolene sodium hemi-heptahydrate equivalent), a cyclodextrin, e.g., 2-hydroxypropyl-β-cyclodextrin, present at a concentration of 100-200 mg / mL, and a PEG, e.g., PEG 3350, present at a concentration of 5-25 mg / mL. More preferably, the liquid formulation, e.g., an aqueous solution, according to the present invention comprises dantrolene, e.g., dantrolene sodium, e.g., dantrolene sodium hemi-heptahydrate, present at a concentration of 4-6.5 mg / mL (equivalent to dantrolene sodium hemi-heptahydrate), a cyclodextrin, e.g., 2-hydroxypropyl-β-cyclodextrin, present at a concentration of 120-190 mg / mL, and a PEG, e.g., PEG 3350, present at a concentration of 15-25 mg / mL. For example, the liquid formulation, e.g., an aqueous solution, according to the present invention may comprise dantrolene, e.g., dantrolene sodium, e.g., dantrolene sodium hemi-heptahydrate, present at a concentration of 6 mg / mL (equivalent to dantrolene sodium hemi-heptahydrate), a cyclodextrin, e.g., 2-hydroxypropyl-β-cyclodextrin, present at a concentration of 176.5 mg / mL, and a PEG, e.g., PEG 3350, present at a concentration of 20 mg / mL.For example, a liquid formulation, e.g., an aqueous solution, according to the present invention may contain dantrolene, e.g., dantrolene sodium, present at a concentration of 5.3 mg / mL (equivalent to dantrolene sodium hemi-heptahydrate), a cyclodextrin, e.g., 2-hydroxypropyl-β-cyclodextrin, present at a concentration of 156.2 mg / mL, and a PEG, e.g., PEG3350, present at a concentration of 17.7 mg / mL.

[0062] Liquid formulations according to embodiments of the present invention advantageously have a pH greater than 7, such as a pH between 8 and 11, such as a pH between 8.8 and 11, such as a pH between 8.8 and 10, or such as a pH between 9 and 10. The pH of liquid formulations according to the present invention may preferably be between 8 and 9.5 or between 9 and 9.5, more preferably between 9.2 and 9.5.

[0063] The present invention also provides a kit comprising a first container (e.g., a vial as described herein) containing a formulation of the present invention embodiment as described herein, and a second container containing a diluent, i.e., a pharma- ceutically acceptable solvent. Preferably, the formulation of the present invention is a dry formulation, e.g., a lyophilized formulation. Examples of pharma- ceutically acceptable solvents include those described herein as suitable for use in the present invention. Preferably, the first container and the second container of the kit of the present invention are vials as disclosed herein.

[0064] The kits of the present invention find use in the treatment of malignant hyperthermia. The kits of the present invention may also find use in the treatment of chronic severe spastic or neuroleptic malignant syndrome. Alternatively, the kits of the present invention may also find use in the treatment of conditions including acute radiation syndrome in hematopoietic syndrome patients exposed to high doses of radiation, psychostimulant-induced intoxication (MDMA and methamphetamine intoxication), exertional heat stroke, concussion and other forms of traumatic brain injury, nerve agent-induced encephalopathy, and / or coronavirus disease (COVID-19).

[0065] The invention further provides the formulations, liquid formulations (e.g., liquid formulations prepared by dissolving a dry formulation, such as a lyophilized formulation, described herein, in a pharma- ceutically acceptable solvent), vials, kits, or aqueous solutions described herein for use as a medicament.

[0066] The invention also provides a formulation, liquid formulation (e.g., a liquid formulation prepared by dissolving a dry formulation, such as a lyophilized formulation, described herein, in a pharma- ceutically acceptable solvent), vial, kit, or aqueous solution described herein for the manufacture of a medicament for the treatment of malignant hyperthermia.

[0067] The invention also provides formulations, liquid formulations (e.g., liquid formulations prepared by dissolving a dry formulation, such as a lyophilized formulation, described herein, in a pharma- ceutically acceptable solvent), vials, kits, or aqueous solutions described herein for use in the treatment of severe spastic or neuroleptic malignant syndrome.

[0068] The invention further provides the formulations, liquid formulations (e.g., liquid formulations prepared by dissolving a dry formulation, such as a lyophilized formulation described herein, in a pharma- ceutically acceptable solvent), vials, kits, or aqueous solutions described herein for use in the treatment of acute radiation syndrome in hematopoietic syndrome patients exposed to high doses of radiation, psychostimulant-induced intoxication (MDMA and methamphetamine intoxication), exertional heat stroke, concussion and other forms of traumatic brain injury, nerve agent-induced encephalopathy, or coronavirus disease (COVID-19).

[0069] The present invention also provides a method for treating malignant hyperthermia in a subject in need thereof, comprising administering to said subject a pharma- ceutical effective amount of a formulation described herein, a liquid formulation (e.g., a liquid formulation prepared by dissolving a dry formulation, such as a lyophilized formulation described herein, in a pharma- ceutical acceptable solvent), or an aqueous solution.

[0070] The present invention further provides a method for treating chronic severe spastic or neuroleptic malignant syndrome in a subject in need thereof, comprising administering to said subject a pharma- ceutical effective amount of a formulation described herein, a liquid formulation (e.g., a liquid formulation prepared by dissolving a dry formulation, such as a lyophilized formulation described herein, in a pharma- ceutical acceptable solvent), or an aqueous solution.

[0071] The present invention further provides a method for treating acute radiation syndrome in hematopoietic syndrome patients exposed to high doses of radiation, psychostimulant-induced intoxication (MDMA and methamphetamine intoxication), exertional heat stroke, concussion and other forms of traumatic brain injury, nerve agent-induced encephalopathy, or coronavirus disease (COVID-19) in a subject in need thereof, comprising administering to said subject a pharmacologic effective amount of a formulation described herein, a liquid formulation (e.g., a liquid formulation prepared by dissolving a dry formulation, such as a lyophilized formulation described herein, in a pharmacologic acceptable solvent), or an aqueous solution.

[0072] The present invention also provides a method for producing the formulations, liquid formulations, kits or aqueous solutions described herein. The formulations of the embodiments of the present invention described herein can be produced by a method comprising the steps of: (i) providing a cyclodextrin (e.g., 2-hydroxypropyl-β-cyclodextrin) stock solution in a pharma- ceutically acceptable solvent; (ii) adding PEG (e.g., PEG3000, PEG3350, or PEG4000) and adding dantrolene (e.g., dantrolene sodium) to the cyclodextrin stock solution; (iii) mixing the solution to dissolve the dantrolene; and (iv) optionally adding more cyclodextrin stock solution if necessary to achieve the final weight. In the context of step (ii) above, PEG and dantrolene can be added to the stock solution in either order or simultaneously. The above method may further include the steps of (v) filtering, (vi) filling the vial, (Vii) drying the formulation (e.g., by lyophilization, optionally including an annealing step), and (viii) closing the vial. The above lyophilization step may include the steps of (a) freezing, (b) optional annealing, (c) evacuation, (d) primary drying, (e) secondary drying, (f) stoppering with optional pre-venting with N2, and (g) venting to atmospheric pressure with N2.

[0073] The present invention further provides a formulation, liquid formulation, or aqueous solution as described herein that can be obtained by a process comprising the steps of: (i) providing a cyclodextrin (e.g., 2-hydroxypropyl-β-cyclodextrin) stock solution in a pharma- ceutically acceptable solvent; (ii) adding PEG (e.g., PEG3000, PEG3350, or PEG4000) and adding dantrolene (e.g., dantrolene sodium) to the cyclodextrin stock solution; (iii) mixing the solutions to dissolve the dantrolene; and (iv) optionally adding more cyclodextrin stock solution if necessary to achieve the final weight. In the context of step (ii) above, the PEG and dantrolene can be added to the stock solution in either order or simultaneously.

[0074] The present invention further provides the dry formulations described herein that can be obtained by a process comprising the steps of: (i) providing a cyclodextrin (e.g., 2-hydroxypropyl-β-cyclodextrin) stock solution in a pharma- ceutically acceptable solvent; (ii) adding PEG (e.g., PEG3000, PEG3350, or PEG4000) and adding dantrolene (e.g., dantrolene sodium) to the cyclodextrin stock solution; (iii) mixing the solution to dissolve the dantrolene; (iv) optionally adding more cyclodextrin stock solution if necessary to achieve a final weight; and (v) drying the resulting solution, for example by lyophilization, to obtain the dry formulation described above. In the context of step (ii) above, PEG and dantrolene can be added to the stock solution in any order or simultaneously.

[0075] The present invention further provides a dry formulation as described herein, comprising 100-120 mg of dantrolene sodium, 3000-4000 mg of 2-hydroxypropyl-β-cyclodextrin, and 350-450 mg of PEG3350.

[0076] As described above, the present invention further provides a vial containing: (i) 101 mg of anhydrous dantrolene sodium (equivalent to 120 mg of dantrolene sodium hemi-heptahydrate), which can also be expressed as 0.3 mmol of dantrolene; (ii) 3.53 g of 2-hydroxypropyl-β-cyclodextrin; and (iii) 400 mg of PEG3350.

[0077] The present invention further provides a vial comprising: (i) 0.3 mmol of dantrolene; (ii) 3.53 g of 2-hydroxypropyl-β-cyclodextrin; and (iii) 400 mg of PEG3350.

[0078] A further object of the present invention is a method for the preparation of a liquid formulation or an aqueous composition as described herein, comprising the step of dissolving a dry formulation as described herein in an aqueous diluent.

[0079] The amount of the formulation according to the invention required to achieve a therapeutic effect will vary depending on the particular route of administration and the characteristics of the subject being treated (e.g., age, weight, sex, or other concurrent medical conditions) and can be readily determined and administered by an ordinarily skilled physician. Preferably, the recommended dosing regimen is in the range of 1-10 mg / kg body weight, e.g., 10 mg / kg dantrolene sodium. In another embodiment, the dosing regimen is in the range of 1.5 mg / kg to 3.5 mg / kg, e.g., 2.5 mg / kg. An ordinarily skilled physician can calculate the number of vials required to obtain a particular dosage to be administered to a subject.

[0080] The formulations of the present invention are preferably administered parenterally, more preferably intravenously. Thus, in one embodiment, the liquid formulations according to the present invention are preferably administered parenterally, more preferably intravenously.

[0081] Although the present invention has been described and illustrated in relation to specific embodiments, it will be appreciated by those skilled in the art that the invention is susceptible to many different variations not specifically illustrated herein. By way of example only, certain possible variations are now described. EXAMPLES

[0082] Example 1: Effect of adding 2-hydroxypropyl-β-cyclodextrin (HPBCD) to dantrolene sodium solution This study was conducted to determine the effect of HPBCD on the solubility of dantrolene sodium. An initial comparison of different HPBCDs was performed using HP5 and HP7 substituted variants (Cavitron™ W7, Ashland, Inc.), which have a typical degree of substitution (average number of hydroxypropyl groups per cyclodextrin molecule) of 4.1-5.1 and 6.0-8.0, respectively. (Comparable products such as Kleptose® HPB (Roquette), an HP5 substituted β-cyclodextrin with a low endotoxin load (less than 10 IU / g) and a typical molar substitution (i.e., per anhydroglucose subunit) of 0.65 (range 0.58-0.68), are also available for commercial scale manufacture.

[0083] The solubility achieved for both the HP5 and HP7 variants was 8.5 mg / mL dantrolene sodium hemi-heptahydrate equivalent in 9 molar equivalents of HPBCD using purified water as the solvent. Due to the higher molecular weight of the HP7 variant, a greater weight of excipient was required to achieve the same molar equivalent concentration compared to the HP5 variant. Overall, the HP5 substituted β-cyclodextrin was preferred and was therefore used in subsequent test formulations.

[0084] 1A: Effect of particle size on dantrolene sodium solubility in HPBCD solution Further analysis was performed to determine the maximum possible concentration of dantrolene sodium at different particle sizes in water-only solutions of HP5-substituted β-cyclodextrin. Commercially available samples of dantrolene sodium with particle sizes of less than 2 μm and less than 63 μm were tested. The following experimental conditions were used for all test formulations: HPBCD concentration, 7 molar equivalents (expressed relative to dantrolene sodium hemi-heptahydrate salt). The results are shown in Table 1 below. DNa denotes dantrolene sodium. [Table 1]

[0085] For particle sizes less than 2 μm, the maximum concentration of dantrolene sodium that could be dissolved under these conditions was 4.55 mg / mL as anhydrous salt equivalent (5.36 mg / mL as hemi-heptahydrate equivalent). The solubility for particle sizes less than 63 μm was similar, at 4.5 mg / mL as anhydrous salt equivalent (5.35 mg / mL as hemi-heptahydrate equivalent).

[0086] Both these results, and those of the initial comparison between the HP5 and HP7 variants, indicate that the addition of HPBCD increases dantrolene sodium solubility compared to existing commercial formulations. For example, the DANTRIUM® IV formulation (Norgine Pharmaceuticals, Uxbridge, UK) achieves a solubility of 0.33 mg / mL (as dantrolene sodium hemi-heptahydrate equivalent). Furthermore, given the current requirement to micronize dantrolene sodium to a diameter of 2 μm or less for DANTRIUM® IV to allow for sufficient solubility, the similarity of solubility across both small (2 micron) and large (63 micron) particle sizes when combined with HPBCD is noteworthy.

[0087] 1B: Effect of parenterally compatible cosolvents on dantrolene solubility in HPBCD solutions This experiment was conducted to determine the effect of different parenterally compatible alcoholic and ketonic co-solvents on dantrolene sodium solubility in 7 molar equivalent HP5-substituted HPBCD solutions. The results are shown in Table 2 below. DNa represents dantrolene sodium. [Table 2]

[0088] These results indicate that the addition of parenterally compatible alcoholic or ketonic solvents did not improve dantrolene sodium solubility in the presence of HPBCD. Rather, all 15 solvents tested, including PEG300 and PEG400, decreased dantrolene solubility.

[0089] 1C: Comparison of dantrolene-HPBCD preparations with existing commercially available dantrolene preparations Table 3 below compares an existing commercially available dantrolene formulation, DANTRIUM IV®, with dantrolene / HP5 substituted HPBCD formulations. DNa indicates dantrolene sodium. [Table 3]

[0090] As shown in Table 3, formulations with HPBCD provide the following advantages over existing dantrolene formulations: higher concentration of dantrolene when reconstituted, smaller reconstitution volume, increased reconstitution speed, smaller vial size required, ability to use larger size dantrolene particles without the need for micronization to 2 μm, and elimination of the need for buffering.

[0091] Example 2 - Effect of adding antifoaming agent This experiment was conducted to evaluate the effect of adding an antifoaming agent to a dantrolene-HPBCD formulation (6 mg / mL dantrolene sodium API + 17.65% weight / volume (176.5 mg / mL equivalent) HPBCD (0.58-0.68 molar substitution range), both components obtained from commercial sources). Initial testing of dimethicone at 2% weight / volume (20 mg / mL equivalent) produced unsatisfactory results. The dimethicone did not completely dissolve and remained layered on top of the solution.

[0092] Commercially available PEG3350 was tested as an alternative antifoam agent using the following preparation process. (i) Preparation of a 17.65% weight / volume stock solution of HPBCD in water for injection; (ii) 2% w / v PEG3350 added to 17.65 w / v HPBCD solution (90% of final volume); (iii) heating the resulting PEG3350 / HPBCD solution to 30±5°C (O2 concentration was reduced to less than 2 ppm by N2-sparging); (iv) distributing dantrolene sodium API into the pre-heated PEG3350 / HPBCD solution; (v) mixing the solution at 30° C. for at least 30 minutes (until dantrolene sodium API is completely dissolved); (vi) The solution was cooled to room temperature (15-25 °C), the oxygen concentration was reduced by bubbling in N2, and the solution was brought to final weight with 17.65% wt / vol stock solution of HPBCD. (vii) filtration of the solution using a 0.22 μm PVDF filter; (viii) filling and pre-stoppering of vials; (ix) lyophilization, which includes the steps of (i) freezing, ii) optional annealing, iii) evacuation, (iv) primary drying, (v) secondary drying, (vi) pre-venting with N2 and stoppering, and (vii) venting to atmospheric pressure with N2 and final stoppering of the vials; (x) Inspection and labeling of vials.

[0093] The addition of PEG3350 resulted in a clear, homogenous solution. Upon shaking (after reconstitution of the lyophilized formulation with water for injection), the PEG3350 formulation cleared more quickly and produced less foam (as determined by visual inspection) compared to a formulation without antifoam, prepared using the same method as above but omitting step (ii). Surprisingly, PEG3350 did not reduce the solubility of dantrolene sodium, considering that dantrolene solubility was reduced when other solvents, including lower molecular weight PEG (PEG300 / 400), were added to the solution (Example 1B). (Similar results were obtained with a higher concentration of PEG3350 (4% w / v, 40 mg / mL equivalent).) These results identify PEG3350 as a surprisingly effective antifoaming agent for dantrolene formulations that does not reduce the solubility of the API.

[0094] Example 3 - Exemplary Dantrolene Formulations Examples of dantrolene formulations suitable for clinical use are described below.

[0095] The formulation is a lyophilized preparation containing commercially available dantrolene sodium hemi-heptahydrate (API particle size 40 μm), 2-hydroxypropyl-β-cyclodextrin, and PEG 3350, prepared according to the method detailed in Example 2. The preparation is packaged in 50 mL vials, each containing 101 mg of anhydrous dantrolene sodium (equivalent to 120 mg of dantrolene sodium hemi-heptahydrate) (also expressed as 0.3 mmol of dantrolene), 3530 mg of 2-hydroxypropyl-β-cyclodextrin, and 400 mg of PEG 3350. Reconstitution of the preparation in 20 mL of water for injection results in concentrations of 5.3 mg / mL of dantrolene sodium hemi-heptahydrate equivalent, 156.2 mg / mL of 2-hydroxypropyl-β-cyclodextrin, and 17.7 mg / mL of PEG 3350 in a total volume of 22.6 mL. Reconstitution time is 90 seconds or less. The reconstituted solution achieves a stable pH of 9.2-9.5 and does not require pH buffering.

[0096] Example 4 - Effect of PEG on Foaming in Comparative Dantrolene Solutions An exemplary formulation of the present invention (Formulation 5) was compared to several prior art formulations (Formulations 1-4) to determine the effect of PEG on the solution.

[0097] Formulations 1-5 were made as detailed below to give a total volume of 20 mL for each solution. Modifications of formulations 1-4 were also made as detailed below to give a total volume of 20 mL for each solution by adding PEG3350 (Macrogol 3350) such that the weight ratio of PEG to dantrolene was 1:3.333. All solutions were shaken by hand for 3 minutes. The height of the foam in each solution was measured as the time it took for the foam to sink. A visual inspection of the solutions was performed and any issues with solubility were noted. The results are shown in Table 4 below. [Table 4]

[0098] These results show that the addition of PEG to prior art dantrolene formulations 1-4 reduced the time it took for the foaming to subside after shaking. In addition, PEG also reduced the foam height in the vial for prior art formulations 2, 3, and 4. Furthermore, a comparison of formulation 5 with formulations 1-4 (in the absence of PEG) shows that the time it took for the foaming to subside in formulation 5 was much shorter when compared to prior art formulations 1-4 (not containing PEG), i.e., the time required to prepare a solution of dantrolene suitable for injection with formulation 5 was shorter when compared to the prior art formulations.

[0099] Formulation 1 was prepared according to Chen et al. (Journal of Pharmaceutical and Biomedical Analysis 135(2017)153-159), as described in Section 2.2, but without the lyophilization step. Formulation 2 was prepared according to Example 4 of WO 2017 / 067980. Formulation 3 was prepared according to Solution 2 of WO 2017 / 067980. Formulation 4 was prepared according to Example 2 of WO 2018 / 146187. Formulation 5 is an exemplary formulation of the invention prepared according to the method detailed in process steps (i)-(vii) of Example 2.

[0100] Where the above description describes integral inventions or elements that have known, obvious, or foreseeable equivalents, such equivalents are incorporated herein as if individually set forth. The true scope of the invention should be interpreted to include any such equivalents, and reference should be made to the claims to determine this true scope. The reader will also understand that any whole or feature of the invention described as preferred, advantageous, convenient, or the like is optional and does not limit the scope of the independent claims. It will be further understood that such optional whole or feature, while a possible advantage in some embodiments of the invention, may not be desirable and therefore may not be present in other embodiments.

Claims

1. A formulation comprising dantrolene or a pharma- ceutically acceptable salt thereof and a cyclodextrin in a molar ratio of 1:3 to 1:12, and also comprising a polyethylene glycol (PEG) having an average molecular weight in the range of 1500-6000.

2. The formulation of claim 1, wherein the pharma- ceutically acceptable salt of dantrolene is a sodium salt.

3. The cyclodextrin contains 5 to 10 glucose subunits, and the glucose subunits of the cyclodextrin are １～６ substituted with an alkyl group, which is itself substituted with a hydroxyl group or a sulfo group; 3. The formulation according to claim 1 or 2.

4. The glucose subunit of the cyclodextrin is ２～４ The formulation of claim 3 , which is substituted with a hydroxyalkyl group.

5. The formulation of claim 3, wherein the glucose subunits are substituted with 2-hydroxypropyl groups.

6. The formulation of claim 3, wherein, on average, each cyclodextrin molecule contains from 4 to 8 substituents.

7. 3. The formulation of claim 1 or 2, wherein the cyclodextrin contains 6 glucose subunits (α-cyclodextrin), 7 glucose subunits (β-cyclodextrin) or 8 glucose subunits (γ-cyclodextrin).

8. The cyclodextrin is a β-cyclodextrin of formula I, 【Chemistry 1】 wherein each R substituent is independently H, —CH ３ , -CH ２ CH (CH ３ )OH, -(CH ２ ) ４ SO ３ 3. The formulation of claim 1 or 2, wherein the hydroxyethyl group is selected from the group consisting of Na and hydroxyethyl.

9. Each R substituent is H and -CH ２ CH (CH ３ 9. The formulation of claim 8, wherein said alkyl group is independently selected from the group consisting of: )OH.

10. 3. The formulation of claim 1 or 2, wherein the dantrolene or the pharma- ceutically acceptable salt thereof and the cyclodextrin are present in a molar ratio of 1:5 to 1:

10.

11. The formulation of claim 1 or 2, wherein the PEG has an average molecular weight in the range of 3000 to 4000.

12. The formulation of claim 1 or 2, wherein the PEG is PEG 3000, PEG 3350 or PEG 4000.

13. 3. The formulation of claim 1 or 2, wherein the PEG is present in an amount such that the weight / weight ratio of PEG to cyclodextrin is from 1:3 to 1:

15.

14. 3. The formulation of claim 1 or 2, comprising dantrolene sodium hemi-heptahydrate and 2-hydroxypropyl-β-cyclodextrin in a molar ratio of 1:8.3 to 1:8.6, and also comprising PEG 3350 in an amount such that the weight / weight ratio of PEG 3350 to 2-hydroxypropyl-β-cyclodextrin is 1:8.5 to 1:9, wherein on average, each 2-hydroxypropyl-β-cyclodextrin molecule is substituted with five hydroxypropyl groups.

15. The formulation of claim 1 which is a dry formulation.

16. A dry formulation comprising: 100-130 mg of dantrolene sodium; 3000-4000 mg of 2-hydroxypropyl-β-cyclodextrin; and 350-450 mg of PEG 3350.

17. 17. A liquid formulation prepared by dissolving the dry formulation of claim 15 or 16 in a pharma- ceutically acceptable solvent.

18. 20. The liquid formulation of claim 17, wherein the pH of the formulation is greater than 7.

0.

19. 3. A formulation according to claim 1 or 2 for use as a medicament.

20. 3. A formulation as claimed in claim 1 or 2 for use in the treatment of malignant hyperthermia.

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