Patent Publication Number: US-2022226306-A1

Title: Composition for caspase inhibitor prodrug injection

Description:
TECHNICAL FIELD 
     The present invention relates to a pharmaceutical composition for injection of a caspase inhibitor prodrug. More specifically, the present invention relates to a pharmaceutical composition for injection comprising a prodrug of a caspase inhibitor, or a pharmaceutically acceptable salt or isomer thereof as an active ingredient, and a biocompatible polymer. 
     BACKGROUND ART 
     Caspases are a type of enzymes and are cysteine proteases that exist as an α2β2 tetramer. Caspase inhibitors interfere with the activity of these caspases, thereby regulating inflammation or apoptosis caused by the action of caspases. Diseases in which symptoms can be eliminated or alleviated by administration of these compounds include osteoarthritis, rheumatoid arthritis, degenerative arthritis, destructive bone disorder, hepatic diseases caused by hepatitis virus, acute hepatitis, hepatocirrhosis, brain damage caused by hepatitis virus, human fulminant liver failure, sepsis, organ transplantation rejection, ischemic cardiac disease, dementia, stroke, brain impairment due to AIDS, diabetes, gastric ulcer, etc. 
     Among compounds having various structures known as caspase inhibitors, isoxazoline derivatives were filed as Korean Patent Application Nos. 10-2004-0066726, 10-2006-0013107 and 10-2008-0025123. In addition, a prodrug of a caspase inhibitor based on an isoxazoline derivative was disclosed in International Publication No. WO 2007/015931 (Applicant: Vertex Pharmaceuticals Incorporated, USA). 
     Meanwhile, nivocasan ((R)—N-((2S,3S)-2-(fluoromethyl)-2-hydroxy-5-oxotetrahydrofuran-3-yl]-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamide) of the following Formula 2 is attracting attention as an effective caspase inhibitor. 
     
       
         
         
             
             
         
       
     
     However, when nivocasan is prepared as a polymeric microsphere formulation in a sustained-release formulation, a large amount of drug is lost during the preparation process according to its physicochemical properties, resulting in low encapsulation efficiency, and there is a limit to in vitro drug release period. 
     DISCLOSURE OF INVENTION 
     Technical Problem 
     Accordingly, the technical problem of the present invention is the provision of a composition for injection in which the encapsulation efficiency is greatly improved and the release period of the drug is greatly increased when a sustained-release formulation of a caspase inhibitor is prepared. 
     Solution to Problem 
     In order to solve the above technical problem, the present invention provides a pharmaceutical composition for injection comprising a compound of the following Formula 1, or a pharmaceutically acceptable salt or isomer thereof as an active ingredient; and a biocompatible polymer: 
     
       
         
         
             
             
         
       
     
     wherein 
     R 1  represents alkyl, cycloalkyl, aryl or —C(O)R 2 ; 
     R 2  represents alkyl, cycloalkyl, aryl, arylalkyl, or heteroaryl including one or more heteroatoms selected from N, O and S; and 
     the alkyl, cycloalkyl, arylalkyl and heteroaryl are optionally substituted, and the substituent may be one or more selected from alkyl, cycloalkyl, hydroxy, halo, haloalkyl, acyl, amino, alkoxy, carboalkoxy, carboxy, carboxyamino, cyano, nitro, thiol, aryloxy, sulfoxy and guanido group. 
     In the present invention, the compound of Formula 1 may form a pharmaceutically acceptable salt. A pharmaceutically acceptable salt may include an acid-addition salt which is formed from an inorganic acid such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, hydrobromic acid and hydroiodic acid; an organic acid such as tartaric acid, formic acid, citric acid, acetic acid, trichloroacetic acid, trifluoroacetic acid, gluconic acid, benzoic acid, lactic acid, fumaric acid, maleic acid and salicylic acid; or sulfonic acid such as methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid and p-toluenesulfonic acid, which form non-toxic acid-addition salt including pharmaceutically acceptable anion. In addition, a pharmaceutically acceptable carboxylic acid salt includes the salt with alkali metal or alkali earth metal such as lithium, sodium, potassium, calcium and magnesium; salts with amino acid such as lysine, arginine and guanidine; an organic salt such as dicyclohexylamine, N-methyl-D-glucamine, tris(hydroxymethyl)methylamine, diethanolamine, choline and triethylamine. The compound of Formula 1 according to the present invention may be converted into their salts by conventional methods. 
     Meanwhile, since the compound of Formula 1 according to the present invention can have an asymmetric carbon center and asymmetric axis or plane, they can exist as E- or Z-isomer, R- or S-isomer, racemic mixtures or diastereoisomer mixtures and each diastereoisomer, all of which are within the scope of the present invention. 
     Herein, unless indicated otherwise, the term “the compound of Formula 1” is used to mean all the compounds of Formula 1, including the pharmaceutically acceptable salts and isomers thereof. 
     Herein, the following concepts defining the substituents are used to define the compound of Formula 1. 
     The term “halogen” or “halo” means fluoride (F), chlorine (Cl), bromine (Br) or iodine (I). 
     The term “alkyl” means straight or branched hydrocarbons, may include a single bond, a double bond or a triple bond, and is preferably C 1 -C 10  alkyl. Examples of alkyl include, but are not limited to, methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, decyl, dodecyl, pentadecyl, octadecyl, acetylene, vinyl, trifluoromethyl and the like. 
     The term “cycloalkyl” means partially or fully saturated single or fused ring hydrocarbons, and is preferably C 3 -C 10  cycloalkyl. Examples of cycloalkyl include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl and the like. 
     Unless otherwise defined, the term “alkoxy” means alkyloxy having 1 to 10 carbon atoms. 
     The term “aryl” means aromatic hydrocarbons, preferably C 5 -C 12  aryl, and more preferably C 6 -C 10  aryl. Examples of aryl include, but are not limited to, phenyl, naphthyl and the like. 
     The term “heteroaryl” means 3- to 12-membered, more preferably 5- to 10-membered aromatic hydrocarbons which form a single or fused ring-which may be fused with benzo or C 3 -C 8  cycloalkyl-including one or more heteroatoms selected from N, O and S as a ring member. Examples of heteroaryl include, but are not limited to, pyridinyl, pyrimidinyl, pyridazinyl, pyrazinyl, oxadiazolyl, isoxadiazolyl, tetrazolyl, triazolyl, indolyl, indazolyl, isoxazolyl, oxazolyl, thiazolyl, isothiazolyl, furanyl, benzofuranyl, imidazolyl, thiophenyl, benzthiazole, benzimidazole, quinolinyl, indolinyl, 1,2,3,4-tetrahydroisoquinolyl, 3,4-dihydroisoquinolinyl, thiazolopyridyl, 2,3-dihydrobenzofuran, 2,3-dihydrothiophene, 2,3-dihydroindole, benzo[1,3]dioxin, chroman, thiochroman, 1,2,3,4-tetrahydroquinoline, 4H-benzo[1,3]dioxin, 2,3-dihydrobenzo[1,4]-dioxin, 6,7-dihydro-5H-cyclopenta[d]pyrimidine and the like. 
     Aryl-alkyl, alkyl-aryl and heteroaryl-alkyl mean groups which are formed by the combination of the above-mentioned aryl and alkyl, or heteroaryl and alkyl. Examples include, but are not limited to, benzyl, thiophenemethyl, pyrimidinemethyl and the like. 
     According to one embodiment of the present invention, in Formula 1 R 1  represents C 1 -C 8  alkyl or —C(O)R 2 ; and R 2  represents C 1 -C 20  alkyl, C 6 -C 10  aryl or C 6 -C 10  aryl-C 1 -C 7  alkyl. 
     According to another embodiment of the present invention, in Formula 1 R 1  represents C 1 -C 5  alkyl or —C(O)R 2 ; R 2  represents C 1 -C 10  alkyl, C 6 -C 10  aryl or C 6 -C 10  aryl-C 1 -C 5  alkyl; and the substituent is alkyl or haloalkyl. 
     Representative compounds of Formula 1 according to the present invention include, but are not limited to, the following compounds:
     (2S,3S)-2-(fluoromethyl)-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamido)-5-oxotetrahydrofuran-2-yl acetate;   (2S,3S)-2-(fluoromethyl)-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamido)-5-oxotetrahydrofuran-2-yl propionate;   (2R,3S)-2-(fluoromethyl)-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamido)-5-oxotetrahydrofuran-2-yl isobutyrate;   (2R,3S)-2-(fluoromethyl)-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamido)-5-oxotetrahydrofuran-2-yl pivalate;   (2S,3S)-2-(fluoromethyl)-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamido)-5-oxotetrahydrofuran-2-yl 3-methylbutanoate;   (2S,3S)-2-(fluoromethyl)-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamido)-5-oxotetrahydrofuran-2-yl 3,3-dimethylbutanoate;   (2S,3S)-2-(fluoromethyl)-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamido)-5-oxotetrahydrofuran-2-yl palmitate;   (2S,3S)-2-(fluoromethyl)-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamido)-5-oxotetrahydrofuran-2-yl benzoate;   (2S,3S)-2-(fluoromethyl)-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamido)-5-oxotetrahydrofuran-2-yl 4-(trifluoromethyl)benzoate;   (2S,3S)-2-(fluoromethyl)-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamido)-5-oxotetrahydrofuran-2-yl 2-phenylacetate;   (5R)—N-((3S)-2-ethoxy-2-(fluoromethyl)-5-oxotetrahydrofuran-3-yl)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamide; and   (5R)—N-((3S)-2-(fluoromethyl)-2-methoxy-5-oxotetrahydrofuran-3-yl)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamide.   

     The terms and abbreviations used herein retain their original meanings unless indicated otherwise. 
     In one embodiment of the present invention, the biocompatible polymer may be one or more selected from the group consisting of polylactide (PLA), polyglycolide (PGA), poly(lactide-co-glycolide)(PLGA), polycaprolactone, polyorthoester and polyphosphazine, but is not limited thereto. 
     In one embodiment of the present invention, the biocompatible polymer is poly(lactide-co-glycolide). Poly(lactide-co-glycolide) may be polymerized from lactide and glycolide by ring-opening polymerization in the presence of a catalyst. 
     In one embodiment of the present invention, a molar ratio of lactide to glycolide of the poly(lactide-co-glycolide) is preferably 90:10 to 10:90, more preferably 90:10 to 40:60, and more preferably 85:15 to 50:50. 
     Poly(lactide-co-glycolide)—that is a polymer obtained by polymerizing lactic acid and glycolic acid, which are materials in the body—has biocompatibility and biodegradability, so it is widely used in medical and pharmaceutical fields through controlled-release of drugs. The higher the ratio of glycolide in poly(lactide-co-glycolide), the greater the hydrophilicity, so that the decomposition rate in the body is faster since moisture is absorbed well, and hydrolysis is accelerated. Conversely, as the ratio of lactide increases, hydrophobicity increases and moisture is not absorbed well, so that the resistance to hydrolysis increases and the decomposition rate in the body is delayed. In addition, the larger the average molecular weight of poly(lactide-co-glycolide), the longer the chain length of the polymer and the longer the decomposition time. Furthermore, the decomposition rate of poly(lactide-co-glycolide) may be affected by the type of end group, molecular structure, crystallinity and the like. In one embodiment of the present invention, the pharmaceutical composition for injection may further comprise a solvent. Examples of the solvent include, but are not limited to, water, saline or phosphate-buffered saline. 
     The injectable pharmaceutical composition of the present invention may further comprise other ingredients such as a dispersing agent, a wetting agent or a suspending agent, if necessary. 
     Exemplary diseases that can be prevented or treated by the pharmaceutical composition for injection according to the present invention include, but are not limited to, those selected from apoptosis-associated diseases, inflammatory diseases, osteoarthritis, rheumatoid arthritis, degenerative arthritis and destructive bone disorders. 
     In one embodiment of the present invention, the pharmaceutical composition for injection according to the present invention may be used for the prevention, treatment or pain relief of osteoarthritis. 
     Advantageous Effects of Invention 
     In the present invention, by providing a pharmaceutical composition for injection in which the compound of Formula 1-which is a prodrug of a caspase inhibitor—is used, the encapsulation efficiency can be greatly improved when preparing polymeric microspheres, and the release period of the drug can be remarkably increased. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is photographs taken with a scanning electron microscope (SEM) of the microspheres prepared in Examples 1, 4 and 5. 
         FIG. 2  is a photograph taken with a scanning electron microscope (SEM) of the microspheres prepared in the Comparative Example. 
         FIG. 3  is a graph showing the results of the in vitro dissolution test in Experimental Example 2. 
     
    
    
     MODE FOR THE INVENTION 
     Hereinafter, the present invention will be described in more detail through preparation examples and examples. However, these examples are only illustrative, and the scope of the present invention is not limited thereto. 
     Preparation Example 1: (2S,3S)-2-(fluoromethyl)-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamido)-5-oxotetrahydrofuran-2-yl acetate 
     
       
         
         
             
             
         
       
     
     Nivocasan ((R)—N-((2S,3S)-2-(fluoromethyl)-2-hydroxy-5-oxotetrahydrofuran-3-yl]-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamide; 5.0 g, 12.0 mmol) was dissolved in dichloromethane (50 mL), and then acetyl chloride (0.94 mL, 13.2 mmol, 1.1 equiv), triethylamine (2.52 mL, 18.0 mmol, 1.5 equiv) and 4-dimethylaminopyridine (0.15 g, 1.2 mmol, 0.1 equiv) were added thereto while keeping the temperature of 5° C. or lower. The reaction mixture was stirred at 25° C. for about 2 hours, and the reaction was terminated by adding 10% aqueous sodium hydrogen carbonate solution (25 mL). After adding water (25 mL) and stirring, the organic layer was separated and distilled under reduced pressure. The obtained mixture was recrystallized in a 1:5 mixture of ethyl acetate and hexane (EtOAc:hexane=1:5) to obtain 3.0 g (yield: 54%) of the title compound. 
       1 H NMR (400 MHz, CDCl 3 ) δ 9.12 (d, 1H), 8.55 (d, 1H), 7.87 (d, 1H), 7.74-7.69 (m, 3H), 7.08 (d, 1H), 5.22 (m, 1H), 4.69 (d, 2H), 4.03 (d, 1H), 3.83 (d, 1H), 2.97 (m, 2H), 2.38 (m, 1H), 2.18 (s, 3H), 1.05 (dd, 6H) 
     Preparation Example 2: (2S,3S)-2-(fluoromethyl)-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamido)-5-oxotetrahydrofuran-2-yl propionate 
     
       
         
         
             
             
         
       
     
     Nivocasan (1.0 g, 2.4 mmol) was dissolved in dichloromethane (20 mL), and then propionyl chloride (0.23 mL, 2.65 mmol, 1.1 equiv), triethylamine (0.5 mL, 3.61 mmol, 1.5 equiv) and 4-dimethylaminopyridine (0.03 g, 0.24 mmol, 0.1 equiv) were added thereto while keeping the temperature of 5° C. or lower. The reaction mixture was stirred at 25° C. for about 2 hours, and the reaction was terminated by adding 10% aqueous sodium hydrogen carbonate solution (10 mL). After adding water (10 mL) and stirring, the organic layer was separated and distilled under reduced pressure. The obtained mixture was column separated by the use of a 1:2 mixture of ethyl acetate and hexane (EtOAc:hexane=1:2) to obtain 0.25 g (yield: 23%) of the title compound. 
       1 H NMR (400 MHz, CDCl 3 ) δ 9.12 (d, 1H), 8.55 (d, 1H), 7.87 (d, 1H), 7.74-7.69 (m, 3H), 7.08 (d, 1H), 5.22 (m, 1H), 4.69 (d, 2H), 4.03 (d, 1H), 3.83 (d, 1H), 2.98 (m, 2H), 2.45 (m, 2H), 2.37 (m, 1H), 1.20 (t, 3H), 1.05 (dd, 6H) 
     Preparation Example 3: (2R,3S)-2-(fluoromethyl)-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamido)-5-oxotetrahydrofuran-2-yl isobutyrate 
     
       
         
         
             
             
         
       
     
     Nivocasan (1.0 g, 2.4 mmol) was dissolved in dichloromethane (20 mL), and then isobutyryl chloride (0.73 g, 2.65 mmol, 1.1 equiv), triethylamine (0.5 mL, 3.61 mmol, 1.5 equiv) and 4-dimethylaminopyridine (0.03 g, 0.24 mmol, 0.1 equiv) were added thereto while keeping the temperature of 5° C. or lower. The reaction mixture was stirred at 25° C. for about 2 hours, and the reaction was terminated by adding 10% aqueous sodium hydrogen carbonate solution (10 mL). After adding water (10 mL) and stirring, the organic layer was separated and distilled under reduced pressure. The obtained mixture was column separated by the use of a 1:2 mixture of ethyl acetate and hexane (EtOAc:hexane=1:2) to obtain 0.06 g (yield: 5%) of the title compound. 
       1 H NMR (400 MHz, CDCl 3 ) δ 9.12 (d, 1H), 8.55 (d, 1H), 7.88 (d, 1H), 7.74-7.69 (m, 3H), 7.09 (d, 1H), 5.25 (m, 1H), 4.69 (d, 2H), 4.03 (d, 1H), 3.83 (d, 1H), 2.95 (m, 2H), 2.63 (m, 1H), 2.38 (m, 1H), 1.26 (dd, 6H), 1.05 (dd, 6H) 
     Preparation Example 4: (2R,3S)-2-(fluoromethyl)-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamido)-5-oxotetrahydrofuran-2-yl pivalate 
     
       
         
         
             
             
         
       
     
     Nivocasan (0.5 g, 1.2 mmol) was dissolved in dichloromethane (20 mL), and then pivaloyl chloride (0.17 g, 1.4 mmol, 1.1 equiv) and 4-dimethylaminopyridine (0.29 g, 2.4 mmol, 2.0 equiv) were added thereto while keeping the temperature of 5° C. or lower. The reaction mixture was stirred at 25° C. for about 2 hours, and the reaction was terminated by adding 10% aqueous sodium hydrogen carbonate solution (10 mL). After adding water (10 mL) and stirring, the organic layer was separated and distilled under reduced pressure. The obtained mixture was recrystallized in a 1:5 mixture of ethyl acetate and hexane (EtOAc:hexane=1:5) to obtain 0.1 g (yield: 17%) of the title compound. 
       1 H NMR (400 MHz, CDCl 3 ) δ 9.11 (d, 1H), 8.55 (d, 1H), 7.88 (d, 1H), 7.71 (m, 3H), 7.11 (d, 1H), 5.26 (m, 1H), 4.68 (d, 2H), 4.02 (d, 1H), 3.83 (d, 1H), 2.95 (m, 2H), 2.39 (m, 1H), 2.27 (s, 2H), 1.28 (s, 9H), 1.05 (dd, 6H) 
     Preparation Example 5: (2S,3S)-2-(fluoromethyl)-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamido)-5-oxotetrahydrofuran-2-yl 3-methylbutanoate 
     
       
         
         
             
             
         
       
     
     Nivocasan (0.5 g, 1.2 mmol) was dissolved in dichloromethane (20 mL), and then isovaleryl chloride (0.17 g, 1.4 mmol, 1.1 equiv), triethylamine (0.18 g, 1.8 mmol, 1.5 equiv) and 4-dimethylaminopyridine (0.015 g, 0.12 mmol, 0.1 equiv) were added thereto while keeping the temperature of 5° C. or lower. The reaction mixture was stirred at 25° C. for about 2 hours, and the reaction was terminated by adding 10% aqueous sodium hydrogen carbonate solution (10 mL). After adding water (10 mL) and stirring, the organic layer was separated and distilled under reduced pressure. The obtained mixture was recrystallized in a 1:5 mixture of ethyl acetate and hexane (EtOAc:hexane=1:5) to obtain 0.13 g (yield: 17%) of the title compound. 
       1 H NMR (400 MHz, CDCl 3 ) δ 9.11 (d, 1H), 8.52 (d, 1H), 7.86 (d, 1H), 7.71 (m, 3H), 7.11 (d, 1H), 5.23 (m, 1H), 4.71 (d, 2H), 4.04 (d, 1H), 3.83 (d, 1H), 2.95 (m, 2H), 2.35 (m, 1H), 2.28 (d, 2H), 2.15 (m, 1H), 1.05 (dd, 12H) 
     Preparation Example 6: (2S,3S)-2-(fluoromethyl)-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamido)-5-oxotetrahydrofuran-2-yl 3,3-dimethylbutanoate 
     
       
         
         
             
             
         
       
     
     Nivocasan (0.5 g, 1.2 mmol) was dissolved in dichloromethane (20 mL), and then t-butyl acetyl chloride (0.19 g, 1.4 mmol, 1.1 equiv), triethylamine (0.18 g, 1.8 mmol, 1.5 equiv) and 4-dimethylaminopyridine (0.015 g, 0.12 mmol, 0.1 equiv) were added thereto while keeping the temperature of 5° C. or lower. The reaction mixture was stirred at 25° C. for about 2 hours, and the reaction was terminated by adding 10% aqueous sodium hydrogen carbonate solution (10 mL). After adding water (10 mL) and stirring, the organic layer was separated and distilled under reduced pressure. The obtained mixture was recrystallized in a 1:5 mixture of ethyl acetate and hexane (EtOAc:hexane=1:5) to obtain 0.14 g (yield: 23%) of the title compound. 
       1 H NMR (400 MHz, CDCl 3 ) δ 9.12 (d, 1H), 8.55 (d, 1H), 7.88 (d, 1H), 7.71 (m, 3H), 7.13 (d, 1H), 5.23 (m, 1H), 4.71 (d, 2H), 4.04 (d, 1H), 3.83 (d, 1H), 2.95 (m, 2H), 2.35 (m, 1H), 2.27 (s, 2H), 1.05 (dd, 15H) 
     Preparation Example 7: (2S, 3S)-2-(fluoromethyl)-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamido)-5-oxotetrahydrofuran-2-yl palmitate 
     
       
         
         
             
             
         
       
     
     Nivocasan (1.0 g, 2.4 mmol) was dissolved in dichloromethane (20 mL), and then palmitoyl chloride (0.73 g, 2.65 mmol, 1.1 equiv), triethylamine (0.5 mL, 3.61 mmol, 1.5 equiv) and 4-dimethylaminopyridine (0.03 g, 0.24 mmol, 0.1 equiv) were added thereto while keeping the temperature of 5° C. or lower. The reaction mixture was stirred at 25° C. for about 2 hours, and the reaction was terminated by adding 10% aqueous sodium hydrogen carbonate solution (10 mL). After adding water (10 mL) and stirring, the organic layer was separated and distilled under reduced pressure. The obtained mixture was column separated by the use of a 1:2 mixture of ethyl acetate and hexane (EtOAc:hexane=1:2) to obtain 0.11 g (yield: 7%) of the title compound. 
       1 H NMR (400 MHz, CDCl 3 ) δ 9.12 (d, 1H), 8.55 (d, 1H), 7.88 (d, 1H), 7.74-7.69 (m, 3H), 7.09 (d, 1H), 5.23 (m, 1H), 4.69 (d, 2H), 4.03 (d, 1H), 3.83 (d, 1H), 2.95 (m, 2H), 2.41 (m, 2H), 2.38 (m, 1H), 1.68 (m, 2H), 1.35-1.24 (m, 24H), 1.05 (dd, 6H), 0.88 (t, 3H) 
     Preparation Example 8: (2S,3S)-2-(fluoromethyl)-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamido)-5-oxotetrahydrofuran-2-yl benzoate 
     
       
         
         
             
             
         
       
     
     Nivocasan (0.5 g, 1.2 mmol) was dissolved in dichloromethane (20 mL), and then benzoyl chloride (0.17 g, 1.4 mmol, 1.1 equiv), triethylamine (0.18 g, 1.8 mmol, 1.5 equiv) and 4-dimethylaminopyridine (0.15 g, 1.2 mmol, 1.0 equiv) were added thereto while keeping the temperature of 5° C. or lower. The reaction mixture was stirred at 25° C. for about 2 hours, and the reaction was terminated by adding 10% aqueous sodium hydrogen carbonate solution (10 mL). After adding water (10 mL) and stirring, the organic layer was separated and distilled under reduced pressure. The obtained mixture was recrystallized in a 1:5 mixture of ethyl acetate and hexane (EtOAc:hexane=1:5) to obtain 0.14 g (yield: 22%) of the title compound. 
       1 H NMR (400 MHz, CDCl 3 ) δ 9.13 (d, 1H), 8.55 (d, 1H), 8.03 (d, 2H), 7.85 (d, 1H), 7.70 (m, 3H), 7.63 (t, 1H), 7.48 (m, 2H), 7.09 (d, 1H), 5.23 (m, 1H), 4.81 (d, 2H), 4.03 (d, 1H), 3.74 (d, 1H), 3.08 (m, 2H), 2.20 (m, 1H), 0.97 (dd, 6H) 
     Preparation Example 9: (2S,3S)-2-(fluoromethyl)-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamido)-5-oxotetrahydrofuran-2-yl 4-(trifluoromethyl)benzoate 
     
       
         
         
             
             
         
       
     
     Nivocasan (0.5 g, 1.2 mmol) was dissolved in dichloromethane (20 mL), and then 4-trifluoromethyl benzoyl chloride (0.30 g, 1.4 mmol, 1.1 equiv) and 4-dimethylaminopyridine (0.29 g, 2.4 mmol, 2.0 equiv) were added thereto while keeping the temperature of 5° C. or lower. The reaction mixture was stirred at 25° C. for about 2 hours, and the reaction was terminated by adding 10% aqueous sodium hydrogen carbonate solution (10 mL). After adding water (10 mL) and stirring, the organic layer was separated and distilled under reduced pressure. The obtained mixture was recrystallized in a 1:5 mixture of ethyl acetate and hexane (EtOAc:hexane=1:5) to obtain 0.1 g (yield: 13%) of the title compound. 
       1 H NMR (400 MHz, CDCl 3 ) δ 9.12 (d, 1H), 8.55 (d, 1H), 8.14 (d, 2H), 7.88 (d, 1H), 7.74 (m, 3H), 7.85 (m, 2H), 7.09 (d, 1H), 5.26 (m, 1H), 4.82 (d, 2H), 4.03 (d, 1H), 3.83 (d, 1H), 3.08 (m, 2H), 2.19 (m, 1H), 0.82 (dd, 6H) 
     Preparation Example 10: (2S,3S)-2-(fluoromethyl)-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamido)-5-oxotetrahydrofuran-2-yl 2-phenylacetate 
     
       
         
         
             
             
         
       
     
     Nivocasan (0.5 g, 1.2 mmol) was dissolved in dichloromethane (20 mL), and then phenylacetyl chloride (0.22 g, 1.4 mmol, 1.1 equiv), triethylamine (0.18 g, 1.8 mmol, 1.5 equiv) and 4-dimethylaminopyridine (0.015 g, 0.12 mmol, 0.1 equiv) were added thereto while keeping the temperature of 5° C. or lower. The reaction mixture was stirred at 25° C. for about 2 hours, and the reaction was terminated by adding 10% aqueous sodium hydrogen carbonate solution (10 mL). After adding water (10 mL) and stirring, the organic layer was separated and distilled under reduced pressure. The obtained mixture was recrystallized in a 1:5 mixture of ethyl acetate and hexane (EtOAc:hexane=1:5) to obtain 0.3 g (yield: 51%) of the title compound. 
       1 H NMR (400 MHz, CDCl 3 ) δ 9.12 (d, 1H), 8.55 (d, 1H), 7.88 (d, 1H), 7.74-7.69 (m, 3H), 7.37 (m, 2H), 7.30 (m, 3H), 7.09 (d, 1H), 5.23 (m, 1H), 4.69 (d, 2H), 4.03 (d, 1H), 3.83 (d, 1H), 3.74 (s, 2H), 2.95 (m, 2H), 2.38 (m, 1H), 1.05 (dd, 6H) 
     Preparation Example 11-1: (S)-4,4-diethoxy-5-fluoro-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamido)pentanoic acid 
     
       
         
         
             
             
         
       
     
     (Step A) Ethyl (S)-5-fluoro-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamido)-4-oxopentanoate 
     
       
         
         
             
             
         
       
     
     Nivocasan (500 mg, 1.2 mmol) was reacted with p-tosylic acid (114 mg, 0.6 mmol), triethoxymethane (20 ml, 120 mmol) and ethanol (20 ml) under reflux for 6 days. The reaction mixture was cooled to room temperature, saturated ammonium chloride solution was added thereto, and extracted with ethyl acetate. The organic layer was dried over sodium sulfate, concentrated and purified by the use of MPLC to obtain the title compound (230 mg, 37%). 
       1 H-NMR (CDCl 3 ) δ 9.15 (d, 1H), 8.54 (d, 1H), 7.84 (d, 1H), 7.75˜7.64 (m, 3H), 4.75˜4.86 (m, 1H) 4.53 (dd, 1H), 4.42 (dd, 1H), 4.02 (d, 1H) 3.97˜3.67 (m, 5H), 3.57˜3.50 (m, 3H), 2.71 (dd, 1H), 2.52˜2.36 (m, 2H), 1.18˜0.97 (m, 15H) 
     (Step B) (S)-4,4-diethoxy-5-fluoro-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamido)pentanoic acid 
     
       
         
         
             
             
         
       
     
     To ethyl (S)-5-fluoro-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisooxazole-5-carboxamido)-4-oxopentanoate (230 mg, 0.44 mmol) and lithium hydroxide (31.9 mg, 1.33 mmol), water (1.12 ml) and tetrahydrofuran (THF, 0.28 ml) were added, and the reaction was carried out at 40° C. for 3 hours. The reactant was cooled to room temperature, concentrated under reduced pressure, 1 N sodium hydroxide was added, and the water layer was washed with toluene. Then, 6N hydrochloric acid was added to adjust the pH to 3, followed by extraction using dichloromethane. The extracted organic layer was dried over sodium sulfate and filtered under reduced pressure to obtain the title compound. The obtained title compound was used in the next reaction without further purification. 
     Preparation Example 11-2: (5R)—N-((3S)-2-ethoxy-2-(fluoromethyl)-5-oxotetrahydrofuran-3-yl)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamide 
     
       
         
         
             
             
         
       
     
     To (S)-4,4-diethoxy-5-fluoro-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisooxazole-5-carboxamido)pentanoic acid (200 mg, 0.38 mmol), trifluoroacetic acid (0.5 ml) and dichloromethane (5 ml) were added at 0° C. and stirred at room temperature for 2 hours. After stirring for 2 hours, the reaction mixture was concentrated under reduced pressure and the title compound (92 mg, 54%) was obtained through MPLC. 
       1 H-NMR (CDCl 3 ) δ 9.11 (d, 1H), 8.56 (d, 1H), 7.86 (d, 1H), 7.75˜7.64 (m, 3H), 7.38 (d, 1H) 4.94 (q, 1H) 4.66 (s, 1H), 4.54 (s, 1H), 4.09 (d, 1H), 4.02 (d, 1H) 3.90˜3.67 (m, 3H), 2.92 (dd, 1H), 2.59 (dd, 1H), 2.36 (p, 1H), 1.29˜1.19 (m, 4H), 1.06 (t, 6H) 
     Preparation Example 12-1: (S)-5-fluoro-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamido)-4,4-dimethoxypentanoic acid 
     
       
         
         
             
             
         
       
     
     (Step A) Methyl (S)-5-fluoro-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamido)-4,4-dimethoxypentanoate 
     
       
         
         
             
             
         
       
     
     Nivocasan (1 g, 2.4 mmol) was reacted with p-tosylic acid (229 mg, 1.2 mmol), triethoxymethane (10 ml, 90 mmol) and methanol (20 ml) under reflux for 4 days. The reaction mixture was cooled to room temperature, saturated ammonium chloride solution was added thereto, and extracted with ethyl acetate. The organic layer was dried over sodium sulfate, concentrated and purified by the use of MPLC to obtain the title compound (561 mg, 49%). 
     (Step B) (S)-5-fluoro-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamido)-4,4-dimethoxypentanoic acid 
     
       
         
         
             
             
         
       
     
     To methyl (S)-5-fluoro-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamido)-4,4-dimethoxypentanoate (562 mg, 1.18 mmol) and lithium hydroxide (134 mg, 5.59 mmol), water (3.42 ml) and THF (0.85 ml) were added, and the reaction was carried out at 40° C. for 4 hours. The reactant was cooled to room temperature, concentrated under reduced pressure, 1 N sodium hydroxide was added, and the water layer was washed with toluene. Then, 6N hydrochloric acid was added to adjust the pH to 3, followed by extraction using dichloromethane. The extracted organic layer was dried over sodium sulfate and filtered under reduced pressure to obtain the title compound. The obtained title compound was used in the next reaction without further purification. 
     Preparation Example 12-2: (5R)—N-((3S)-2-(fluoromethyl)-2-methoxy-5-oxotetrahydrofuran-3-yl)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamide 
     
       
         
         
             
             
         
       
     
     To (S)-5-fluoro-3-((R)-5-isopropyl-3-(isoquinolin-1-yl)-4,5-dihydroisoxazole-5-carboxamido)-4,4-dimethoxypentanoic acid (441 mg, 0.9 mmol), trifluoroacetic acid (0.5 ml) and dichloromethane (5 ml) were added at 0° C. and and stirred at room temperature for 2 hours. After stirring for 2 hours, the mixture was concentrated under reduced pressure and the title compound (196 mg, 51%) was obtained through MPLC. 
       1 H-NMR (CDCl 3 ) δ 9.12 (d, 1H), 8.56 (d, 1H), 7.86 (d, 1H), 7.75˜7.64 (m, 3H), 7.40 (d, 1H) 4.91 (q, 1H) 4.66 (dd, 1H), 4.54 (dd, 1H), 4.08 (d, 1H), 4.80 (d, 1H), 3.35 (s, 3H), 2.90 (dd, 1H), 2.56 (dd, 1H), 2.36 (p, 1H), 1.06 (t, 6H) 
     Examples 1 to 6: Preparation of Microspheres Encapsulating Prodrugs 
     According to the compositions denoted in Table 1 below, microspheres encapsulated with caspase inhibitor prodrugs were prepared. 
     The caspase inhibitor prodrugs and PLGA (L/G ratio=50:50, 75:25 or 85:15, M.W. 38,000-240,000) were weighed in a weight ratio of 1:5, an organic solvent dichloromethane was added in an amount of 10 times the weight of PLGA or the weight of the prodrug and PLGA, and stirred to prepare the disperse phase. 
     For the continuous phase, 150 mL or 4,800 mL of 1% or 2% polyvinyl alcohol (M.W. 31,000-50,000, degree of hydrolysis 87-89%) was used, and emulsions were prepared by membrane emulsification. 
     The prepared emulsions were stirred overnight at room temperature to remove solvent, washed with sterile purified water, and then lyophilized to obtain microspheres. 
     
       
         
           
               
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                   
                 Example No. 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
               
               
                   
                 Preparation 
                 Preparation 
                 Preparation 
                 Preparation 
                 Preparation 
                 Preparation 
               
               
                 Prodrug 
                 Example 1 
                 Example 2 
                 Example 8 
                 Example 1 
                 Example 1 
                 Example 1 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Prodrug amount (g) 
                 0.4 
                 0.4 
                 0.4 
                 3.4 
                 3.4 
                 2.5 
               
               
                 PLGA amount (g) 
                 2.0 
                 2.0 
                 2.0 
                 17.0 
                 17.0 
                 12.5 
               
               
                 PLGA L/G ratio 
                 50:50 
                 50:50 
                 50:50 
                 50:50 
                 75:25 
                 85:15 
               
               
                 PLGA M.W. (kDa) 
                 38-54 
                 38-54 
                 38-54 
                 38-54 
                  76-115 
                 190-240 
               
               
                 Organic solvent amount (g) 
                 20.0 
                 20.0 
                 20.0 
                 170.0 
                 170.0 
                 150.0 
               
               
                 PVA concentration (%, w/v) 
                 2 
                 2 
                 2 
                 1 
                 1 
                 1 
               
               
                 PVA solution amount (mL) 
                 150 
                 150 
                 150 
                 4,800 
                 4,800 
                 4,800 
               
               
                   
               
            
           
         
       
     
     Comparative Example: Preparation of Microspheres Encapsulating Nivocasan 
     According to the composition denoted in Table 2 below, microspheres encapsulated with nivocasan were prepared. 
     Nivocasan and PLGA (L/G ratio=50:50, M.W. 38,000-54,000) were weighed in a weight ratio of 1:5, an organic solvent dichloromethane was added in an amount of 10 times the weight of PLGA, and stirred to prepare the disperse phase. 
     For the continuous phase, 150 mL of 2% polyvinyl alcohol (M.W. 31,000-50,000, degree of hydrolysis 87-89%) was used, and emulsions were prepared by membrane emulsification. 
     The prepared emulsions were stirred overnight at room temperature to remove solvent, washed with sterile purified water, and then lyophilized to obtain microspheres. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Compound 
                 Nivocasan 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 Compound amount (g) 
                 0.4 
               
               
                   
                 PLGA amount (g) 
                 2.0 
               
               
                   
                 PLGA L/G ratio 
                 50:50 
               
               
                   
                 PLGA M.W. (kDa) 
                 38-54 
               
               
                   
                 Organic solvent amount (g) 
                 20.0 
               
               
                   
                 PVA concentration (%, w/v) 
                 2 
               
               
                   
                 PVA solution amount (mL) 
                 150 
               
               
                   
                   
               
            
           
         
       
     
     Experimental Example 1: Analysis of Microsphere Properties and Drug Encapsulation Rate 
     The properties of the microspheres prepared in the Examples and Comparative Example were characterized by drug precipitation during manufacture, the morphology of lyophilized microspheres, and floating in the aqueous phase upon redispersion. 
     Whether or not precipitation of the drug was confirmed through an optical microscope during manufacture, and the morphology of the lyophilized microspheres were observed by scanning electron microscopy. Whether or not floating of the microspheres in the aqueous phase was confirmed by redispersing the lyophilized microspheres in water. 
     For the amount of drug encapsulated in the microspheres, 30 mg of microspheres were dissolved in 50 mL of acetonitrile, and the supernatant obtained by ultracentrifugation was analyzed by HPLC (high-performance liquid chromatography). The encapsulation efficiency was calculated by measuring the encapsulation rate. 
       Encapsulation rate=(weight of measured drug)/(weight of measured microspheres (MS))*100(%) 
       Encapsulation efficiency=(weight of measured drug)/(weight of drug added initially)*100(%) 
     The measured results are summarized and represented in Table 3. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                   
                 Example 1 
                 Example 4 
                 Exmaple 5 
                 Example 6 
                 Comp. Ex. 
               
               
                   
               
             
            
               
                 Drug precipitation 
                 Almost 
                 Almost 
                 Almost 
                 Almost 
                 Large 
               
               
                   
                 none 
                 none 
                 none 
                 none 
                 amount 
               
               
                 Microsphere morphology 
                 Good 
                 Good 
                 Good 
                 Good 
                 Good 
               
               
                 Microsphere floating 
                 None 
                 None 
                 None 
                 None 
                 None 
               
               
                 Drug encapsulation rate (%, w/w) 
                 15.6 
                 14.4 
                 13.9 
                 14.5 
                 8.2 
               
               
                 Drug encapsulation efficiency (%) 
                 93.4 
                 86.4 
                 83.4 
                 87.0 
                 49.1 
               
               
                   
               
            
           
         
       
     
     As can be seen from Table 3, the microspheres of the Examples encapsulating the prodrugs showed little drug precipitation and excellent drug encapsulation efficiency, whereas in the microspheres of the Comparative Example encapsulating nivocasan, a large amount of the drug was precipitated during the preparation process, and the drug encapsulation efficiency was only about half in comparison with the Examples. 
     Experimental Example 2: In Vitro Dissolution Test of Microspheres 
     An in vitro dissolution test of the microspheres prepared in Examples 4 and 5 was carried out. The microspheres were shaken in phosphate-buffered saline (PBS, 37° C.), the eluate was collected and filtered at specific times, and the amount of drug released was analyzed by HPLC. Because the prodrug is converted to the parent drug, caspase inhibitor, by hydrolysis in aqueous solution, the amount of the released drug was confirmed through the amount of caspase inhibitor measured by HPLC.