WO2011002184A2

WO2011002184A2 - Phosphoric acid ester of bicalutamide for treating prostate cancer

Info

Publication number: WO2011002184A2
Application number: PCT/KR2010/004153
Authority: WO
Inventors: Sun Young Jang; Sung Bum Kim; Byung Ku Kim; Min Hoe Heo; Eun Young Kim; Tae Hun Song; Young Hoon Kim; Kwee Hyun Suh; Gwan Sun Lee
Original assignee: Hanmi Pharm. Co., Ltd.
Priority date: 2009-06-30
Filing date: 2010-06-25
Publication date: 2011-01-06
Also published as: KR20110001378A; WO2011002184A3

Abstract

Provided is a phosphoric acid ester of bicalutamide and a pharmaceutically acceptable salt thereof, and a pharmaceutical composition containing the same as an active ingredient for treating prostate cancer, with which a linear correlation between the systemic exposure to bicalutamide and the dosage level can be achievable, making it possible to increase the bioavailability of bicalutamide upon oral administration at a high dosage level.

Description

PHOSPHORIC ACID ESTER OF BICALUTAMIDE

FOR TREATING PROSTATE CANCER

FIELD OF THE INVENTION

The present invention relates to a phosphoric acid ester derivative of bicalutamide or a pharmaceutically acceptable salt thereof, and a pharmaceutical composition for treating prostate cancer containing the same as an active ingredient, which exhibits a linear correlation between the systemic availability of bicalutamide and the dosage level, making it possible to increase the bioavailability of bicalutamide at a high oral administration dosage thereof.

BACKGROUND OF THE INVENTION Bicalutamide is a non-steroidal anti-androgen which has the IUPAC name of N-[4-cyano-3-(trifluoromethyl)phenyl]-3-[(4-fluorophenyl)sulfonyl]-2- hydroxy-2-methylpropanamide. It was first disclosed in EP Patent No. 0 100 172 and its structure is shown in Formula II. Bicalutamide is a chiral compound having one asymmetric carbon, which can exist as (R)- or (S)- enantiomer.

The method for preparing bicalutamide racemate is described in the above-mentioned EP Patent No. 0 100 172, and there have been reported methods for preparing (R)- and (S)-enantiomers thereof by optical resolution of the racemate [H. Tucker et al., J. Med. Chem., 1988, 3_i, 885-887], or asymmetric synthesis [K. D. James et al., Tetrahedron, 2002, 58, 5905-5908].

The properties of bicalutamide as an anti-androgen agent and its usefulness in treating prostate cancer have been reviewed [B. J. A Furr et al., Urology, 1996, 47(Suppl. IA), 13-25; Q J, C et al., Urology, 1996, 47(Suppl. IA), 70-79; and A. Mukherjee et al., Xenobiotica, 1996, 26, 117-122], and the (R)-enantiomer, the dextrorotatory isomer, has been revealed to be more active than the (S)-enantiomer in in vivo and ex vivo studies. Currently, a number of generic products of bicalutamide racemate, including the brand name Casodex^® of AstraZeneca, are used for treating and reducing the risk of prostate cancer.

In general, for patients with advanced prostate cancer, bicalutamide is orally administered in combination with a luteinizing hormone-releasing hormone (LHRH) analogue or surgical castration at a daily dose of 50 mg, and, for patients with localized or locally advanced prostate cancer, it is orally administered, alone or as adjuvant in the treatment by radical prostatectomy or radiotherapy at a daily dose of 150 mg.

The bioavailability of an orally administered drug can be calculated by comparing the area under the curve (AUC) based on a plasma drug concentration v. elapsed time plot after administration via oral or intravenous route, i.e., systemic exposure. In addition, the relative bioavailability of a drug for a series of formulations with different doses can be assessed by comparing the AUCs based on various doses. If the dose- AUC correlation is not linear, the systemic exposure to the drug does not depend on the incremental increase of the does, i.e., no further significant increase in the drug's efficacy is achievable beyond a certain dose level. Moreover, there is observed a high degree of inter-patient variability in the degree of systemic exposure.

The bioavailability of an orally administered drug is largely affected by factors which influence the absorption across mucosal membrane in the GI tract such as the solubility and gastrointestinal mucosal permeability of the drug. Bicalutamide is a lipophilic drug (log P_Octanoi_/water ⁼2.92 where P is the partition coefficient), which has a very high gastrointestinal mucosal permeability, but has a very low water solubility of less than 0.005 mg/mL. Therefore, the absorption rate and the degree of bicalutamide absorption are determined by its rate of dissolution and degree of solubility.

As reported in the literature regarding the pharmacokinetics and pharmacodynamics of bicalutamide in animals and humans [I. D. Cockshott et al., Xenobiotica, 1991, 21_, 1347-1355; I. D. Cockshott, Clin. Pharmacokinet, 2004, 43, 855-878], the bioavailability of bicalutamide is shown to vary widely depending on the dose, and the dose-systemic exposure correlation has been reported to be non-linear in tests with rat, dog, and human. It is known that, for example, the bioavailability of the drug observed in a test with rats ranges from 72.0% to 87.5% at 1 mg/kg single dose, but it decreases to 10.4% to 12.0% when the dosage is increased to 250 mg/kg. Similarly in humans, although the exposure of bicalutamide or its active enantiomer, (R)- bicalutamide, linearly increases to a certain extent at doses of 100 mg to 150 mg, it reaches a plateau at a dose above 150 mg and no further practical increase in systemic exposure is achievable at a dose above 300 mg.

Therefore, a linear increase in the bioavailability of bicautamide, or (R)-bicalutamide, with increasing dosage can provide significantly advantageous effects over conventional formulations. For example, one possible benefit of achieving relatively higher bioavailability would be more effective in the treatment of patients with more advanced stages of prostate cancer than is currently possible with the conventional formulations. This could be useful for treating metastatic prostate cancer, using, for example, bicalutamide as a monotherapeutic agent (i.e., not in combination with LHRH analogue therapy or surgical castration). Further, if a linear relationship between the dose and systemic exposure is achievable, there would increase the predictability and uniformity of the treatment according to the dosage in the patient population and also reduce the inter-patient variability in the bicalutamide concentration in plasma. Still further, such increased systemic exposure and bioavailability would be useful in reducing the daily dose of bicalutamide required to achieve the same level of bioavailability achievable by a conventional formulation.

There have been various attempts to accomplish the objective stated above. For instance, there have been attempts to increase the systemic exposure of bicalutamide with increasing dosage by using a solid dispersion formulation comprising bicalutamide and an enteric polymer as disclosed in

International Patent Publications WO 02/067893, WO 03/032950, and WO

06/090129; and nanoparticulate bicalutamide particles having an effective average particle size of less than 2,000 nm as disclosed in International Patent Publication WO 06/069098. However, such disclosures based on pharmaceutical approaches using bicalutamide or (R)-bicalutamide are not clear on the issue of whether or not the above objective can be accomplished.

The present inventors have found that the bioavailability of bicalutamide can be highly enhanced at a high dose level, and successfully achieved a linear correlation between the dosage of bicalutamide or an active enantiomer (R)-bicalutamide and the systemic exposure, by administering bicalutamide as the form of a prodrug, i.e., bicalutamide phosphoric acid ester or a pharmaceutically acceptable salt thereof.

SUMMARY OF THE INVENTION

Therefore, it is an object of the present invention to provide a phosphoric acid ester of bicalutamide or pharmaceutically acceptable salts thereof, and a pharmaceutical composition for treating prostate cancer containing the same as an active ingredient, with which the systemic exposure to bicalutamide increases linearly with the dosage level, thereby providing increased bioavailability of bicalutamide upon oral administration at a high dosage level. In accordance with one aspect of the present invention, there is provided a phosphoric acid ester of bicalutamide of Formula I or a pharmaceutically acceptable salt thereof:

Further, there is provided a pharmaceutical composition for treating or reducing the risk of prostate cancer, comprising a phosphoric acid ester of bicalutamide of Formula I or a pharmaceutically acceptable salt thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the present invention will become apparent from the following description of the invention, when taken in conjunction with the accompanying drawings, which respectively show: Fig. 1 : the degree of systemic exposure (the area under the curve (AUCo- i_nf) of time-drug concentration) according to the dosage level of bicalutamide and a bicalutamide phosphoric acid ester in rats, respectively;

Fig. 2: the correlations between the degrees of systemic exposure and the dosage of bicalutamide and a bicalutamide phosphoric acid ester in rats, respectively; and

Fig. 3: the dependency of the bioavailability on the dosage of bicalutamide and a bicalutamide phosphoric acid ester in rats. DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the present invention is described in detail.

The term "phosphoric acid ester of bicalutamide" as used herein refers to a kind of prodrug produced by substituting one of hydroxyl groups of a phosphoric acid with a hydroxyl group of bicalutamide, which is absorbed in the GI tract and the phosphoric acid ester group thereof is hydrolyzed at tissues, bloods, or liver, etc., to generate the pharmacologically active bicalutamide.

The term "pharmaceutically acceptable salt" as used herein refers to a salt commonly used in this art, and includes, but not limited thereto, for example, a salts of an inorganic metal such as sodium, potassium, calcium, magnesium, zinc, or iron.; an ammonium salt; a salt with a basic amino acid such as arginine or lysine; a salt with an organic amine such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, ethanolamine, diethanolamine, l-amino-2-propanol, 3-amino-

1-propanol, hexamethylenetriamine, piperidine, piperazine, pyrrolidine, morpholine, n-methylglucamine (meglumine), creatinine, or tromethamine; and a quaternary ammonium salt such as choline or tetramethylammonium. A preferable inorganic metal salt is sodium, potassium, calcium, or magnesium salt, and a preferable organic salt is arginine, lysine, n-methylglucamine, or choline salt.

The term "risk of prostate cancer" as used herein refers to a secondary disorder which may lead to prostate cancer, including: poor urinary flow; urinary frequency, urgency, or retention; repeated urinary tract infections; blood in the urine or semen; decreased ability to achieve or maintain erection; decreased sperm content of ejaculate; and low abdominal pain.

The phosphoric acid ester of bicalutamide of Formula I is a divalent acid as a mono-substituted phosphoric acid. Accordingly, when the phosphoric acid ester of bicalutamide as a divalent acid forms salts, mono- or di-salts may be formed, and various forms of salts may be formed based on the valency of paring cations. For example, it will form both monosodium and disodium salts with monovalent cations such as sodium, and will conventionally form monocalcium salts with divalent cations such as calcium.

The phosphoric acid ester of bicalutamide of Formula I or pharmaceutically acceptable salt thereof is obtainable in many forms such as a hydrate, solvate, or a mixture thereof, in accordance with conventional preparation methods or by various methods known to one of ordinary skill in the art. The fact that medical ingredients can be present in the form of a hydrate, solvate or a mixture thereof is known to one skilled in the art, and various methods of preparing and characterizing it are also known. Accordingly, it is obvious that these are in the scope of the present invention, though they all are not characterized by preparation in the present invention.

In the phosphoric acid ester of bicalutamide or pharmaceutically acceptable salt thereof in accordance with the present invention, 50% or more, preferably 90% or more, more preferably 95% or more, still more preferably 98%, or most preferably 99% or more may be of the (R)-enantiomeric form.

The phosphoric acid ester of bicalutamide or pharmaceutically acceptable salt thereof in accordance with the present invention may be prepared as following Reaction Scheme I. In Reaction Scheme I, bicalutamide of Formula II is subjected to a reaction with lithium diisopropylamide (LDA) and tetrabenzyl pyrophosphoric acid of Formula III in an organic solvent (e.g., tetrahydrofuran (TFIF)), to obtain a dibenzyl compound of phosphoric acid ester of bicalutamide of Formula IV, and the dibenzyl compound of Formula IV is then subjected to a hydrogenation reaction in an alcohol (e.g., methanol) to remove a dibenzyl group, thereby obtaining the phosphoric acid ester of bicalutamide of Formula I according to the present invention.

The phosphoric acid ester of bicalutamide of Formula I prepared by the above-mentioned method may be present in the form of a solvate or hydrate as well as in the form of a pharmaceutically acceptable salt thereof or a hydrate or solvate thereof. In each form, 50% or more, preferably 90% or more, more preferably 95% or more, still more preferably 98%, or most preferably 99% or more may be of the (R)-enantiomeric form.

The phosphoric acid ester of bicalutamide in accordance with the present invention has significantly enhanced solubility of over 100 times compared to bicalutamide, in water, or a primary (pH 1.2 HCl buffer) and secondary dissolution media (pH 6.8 phosphate buffer) commonly used in laboratory tests for anticipating the absorption rate and degree of the drug (see

Table 1). The primary or secondary medium is a test solution having the pH in the gastrointestine or duodenum (or small intestine), respectively. As the compound of the present invention showed significantly enhanced solubility in the gastrointestinal tract, the absorption of the drug will highly increase.

When the phosphoric acid ester of bicalutamide in accordance with the present invention is orally administered to a mammal, the systemic exposure of bicalutamide or (R)-bicalutamide, i.e., the area under the curve (AUC) based on a plasma drug concentration v. elapsed time plot after administration, was shown to linearly increase with increasing dosage, unlike the oral administration of bicalutamide {see Table 2). As the bioavailability is maintained with increasing dosage, it is possible to treat patients with more advanced stages of prostate cancer than is currently possible with the conventional formulations, and to effectively treat metastatic prostate cancer, using bicalutamide as a monotherapeutic agent (i.e., not in combination with LHRH analogue therapy or surgical castration). Further, it is possible to increase the predictability and uniformity of the treatment according to the dosage in a patient population and also to reduce the inter-patient variability in the bicalutamide concentration in plasma. Furthermore, it is possible to achieve the same level of bioavailability achievable by a conventional formulation, in spite of a small dosage.

In addition, the present invention provides a pharmaceutical composition for treating or reducing the risk of prostate cancer, comprising a phosphoric acid ester of bicalutamide of Formula I or a pharmaceutically acceptable salt thereof.

The pharmaceutical composition according to the present invention may be formulated into an oral dosage form containing an effective amount of the phosphoric acid ester of bicalutamide of Formula I or pharmaceutically acceptable salt thereof, and may be alternatively formulated into an injectable formulation such as subcutaneous, intramuscular or intravenous injection, suppositories, or transdermal formulation, according to the significantly enhanced solubility of the phosphoric acid ester of bicalutamide or pharmaceutically acceptable salt thereof. Exemplary pharmaceutical compositions include tablets, capsules, troches, powders, suspensions, solutions, syrups, and patches, and when the ease of administration is contemplated, a tablet or capsule is more preferred as a single dose.

The pharmaceutical composition in accordance with the present invention may further comprise other ingredients such as carriers, diluents, or excipients, in conjunction with an effective amount of the phosphoric acid ester of Formula I or pharmaceutically acceptable salt thereof as an active ingredient, and may additionally or optionally comprise an effective amount of other active ingredients.

Exemplary carriers, diluents, or excipients include, but are not limited to, excipients such as starches, sugars, lactose, dextrin, mannitol, sorbitol, mircrocrystalline cellulose, low substituted hydroxypropyl cellulose, sodium carboxymethylcellulose, gum arabia, amylopectin, light anhydrous silicic acid, and synthetic aluminum silicate; fillers and extenders such as calcium phosphate and silicate derivatives; binders such as starches, sugars, mannitol, trehalose, dextrin, amylopectin, sucrose, gluten, gum arabia, cellulose derivatives such as methylcellulose, carboxymethylcellulose, sodium carboxymethylcellulose, microcrystalline cellulose, hydroxypropyl cellulose, and hydroxypropyl methylcellulose, etc., gelatin, alginate, and polyvinylpyrrolidone; lubricants such as talc, calcium or magnesium stearate, hydrogenated castor oil, talcum powder, and solid polyethylene glycols; disintegrants such as povidone, crosscarmellose sodium, and crospovidone; and surfactants such as polysorbates, cetyl alcohols, and glycerol monosterate.

The pharmaceutical composition comprising various carriers, diluents, or excipients in conjunction with an effective amount of the phosphoric acid ester of Formula I or pharmaceutically acceptable salts thereof may be conventionally prepared by methods known in the art {see [Remington's Pharmaceutical Sciences, Mack Publishing Company, Easton, PA, 19^th Edition, 1995])

Meanwhile, solid oral formulations such as tablets, capsules or powders according to the present invention may be formulated into a solid dispersion formulation with various enteric polymers as disclosed in International Patent Publication WO 02/067896 or may be formulated into a nanoparticle as disclosed in International Patent Publication WO 06/069098, and may be otherwise coated with various forms of enteric polymers by a number of methods. Further, the tablets and capsules may be formulated by release- controlling means and drug delivery devices commonly used in this art, as disclosed in U.S. Patent Nos. 3,845,770, 3,916,899, and 4,008,719.

In the pharmaceutical composition according to the present invention, the amount of the phosphoric acid ester of bicalutamide of Formula I or pharmaceutically acceptable salt as an active ingredient is 1 mg to 2,000 mg/single dose, preferably 10 mg to 1,000 mg/single dose, so that it can be administered in a single dose or uniformly divided doses.

Further, in the oral pharmaceutical composition according to the present invention, the amount of the phosphoric acid ester of bicalutamide of Formula I or pharmaceutically acceptable salt as an active ingredient is 0.1 to 95% by weight, preferably 1 to 70% by weight based on the total amount of the single dose composition.

The following Examples are given for the purpose of illustration only, and are not intended to limit the scope of the invention.

Analytical values described in following Examples, e.g., melting point, water content, proton nuclear magnetic resonance spectroscopy, and infrared spectroscopy were measured using a capillary digital melting point apparatus (Barnstead Electrothermal, U.K.), 795 KFT titrino (Metrohm, Switzerland), AVANNC DPX 300 (Bruker, Germany), and MB-100 FT-IR spectrometer (Bomen, Canada), respectively.

Example 1: Preparation of O-dibenzyl phosphoric acid ester of bicalutamide (racemate)

i) 3.1 mL (22.1 mmol) of diisopropylamine was dissolved in 50 mL of tetrahydrofuran and cooled to -15°C. Then, 11.0 mL (17.6 mmol) of hexane solution in which n-butyl lithium is dissolved at a concentration of 1.6M was added dropwise thereto and stirred at -15°C for 15 min to prepare a tetrahydrofuran solution of lithium diisopropylamide.

ii) 6.29 g (14.6 mmol) of bicalutamide racemate was dissolved in 200 mL of tetrahydrofuran and cooled to -78°C. Then, the tetrahydrofuran solution of lithium diisopropylamide prepared in step i) was added dropwise thereto and stirred at -78°C for 5 min. 9.5 g (17.6 mmol) of O-tetrabenzyl pyrophosphoric acid was added to the reaction solution at a time, and stirred at -78⁰C for 2 hours and at 0⁰C for 1 hour. Subsequently, 200 mL of a saturated ammonium chloride solution was added thereto, and extracted twice using each 200 mL of ethyl acetate. The organic layer was washed with saline water, dried over anhydrous magnesium sulfate, and concentrated under a reduced pressure, to obtain 7.1 g (70%) of O-dibenzyl phosphoric acid ester of bicalutamide (racemate) as light yellow foam.

¹H-NMR (300MHz, CD₃OD, ppm): δ 1.82(s, 3H), 4.12(s, 2H), 5.14- 5.21(m, 4H), 7.23(t, J=8.67Hz, 2H), 7.32-7.40(m, 10H), 7.90-7.97(m, 4H), 8.17(d, J=1.48Hz, IH)

IR (KBr, cm^"1): υ 3388, 2230, 1590, 1528, 1494, 1325, 1144, 1012

Example 2: Preparation of phosphoric acid ester of bicalutamide (racemate)

5.7 g (8.3 mmol) of O-dibenzyl phosphoric acid ester of bicalutamide (racemate) prepared in Example 1 was dissolved in 100 mL of methanol and 0.57 g of palladium 10% on carbon was added thereto, and stirred at room temperature under a hydrogen gas until the starting material disappears. The resulting mixture was filtered to remove carbon, washed with methanol, and the filtrate was concentrated under a reduced pressure. Then, 10 mL of ethyl acetate was added to the residue as white foam, completely dissolved while refluxing, and kept overnight in a refrigerator. The precipitate was filtered, washed with cold ethyl acetate, and dried at 40⁰C, to obtain 3.8 g (90%) of phosphoric acid ester of bicalutamide (racemate) as an anhydrous form of white crystalline powder.

Melting point: 214 to 216°C

Water content (KF coulometer): 0.30%

¹H-NMR (300MHz, CD₃OD₅ ppm): δ 1.82(s, 3H), 4.10(dd, J=20.83Hz, J=14.68Hz, 2H), 7.24(t, J=8.73Hz, 2H), 7.92-8.08(m, 4H), 8.25(d, J=I.69Hz, IH)

IR (KBr, cm^"1): υ 3415, 2233, 1700, 1614, 1592, 1432, 1238, 1179, 1149, 1074 Example 3: Preparation of phosphoric acid ester of bicalutamide (racemate)

5.1 g (10.0 mmol) of the phosphoric acid ester of bicalutamide (racemate) prepared in accordance with the method of Example 2 was suspended in 100 mL of water, stirred at 50⁰C for 5 hours, cooled to 0⁰C, and further stirred for 2 hours. The precipitate was filtered, washed with cold distilled water, and dried at 40⁰C, to obtain 5.O g (93%) of phosphoric acid ester of bicalutamide (racemate) as a dihydrate form of white crystalline powder.

Melting point: 106 to 108⁰C

Water content (KF coulometer): 6.49% (theoretical water content of dihydrate 6.59%)

¹H-NMR (300MHz, CD₃OD, ppm): δ 1.83(s, 3H), 4.10(dd, J=6.65Hz, J=14.8Hz, 2H), 7.25(t, J=6.85Hz, 2H), 7.94-8.06(m, 4H), 8.23(d, J=I .72Hz, IH)

IR (KBr, cm --1): υ 3530, 3293, 2234, 694, 1533, 496, 1387, 1324, 1084, 532

Example 4: Preparation of O-dibenzyl phosphoric acid ester of (R)- bicalutamide

6.29 g (14.6 mmol) of (R)-bicalutamide was dissolved in 200 mL of tetrahydrofuran and cooled to -78°C. Then, the tetrahydrofuran solution of lithium diisopropylamide prepared in step i) of Example 1 was added dropwise thereto and stirred at -78°C for 5 min. 9.5 g (17.6 mmol) of O-tetrabenzyl pyrophosphoric acid was added to the reaction solution at a time, and stirred at - 78°C for 2 hours and at 0⁰C for 1 hour. Then, 200 mL of a saturated ammonium chloride solution was added thereto, and extracted twice using each 200 mL of ethyl acetate. The organic layer was washed with saline water, dried over anhydrous magnesium sulfate, and concentrated under a reduced pressure, to obtain 7.6 g (75%) of O-dibenzyl phosphoric acid ester of (R)- bicalutamide as light yellow foam.

¹H-NMR (300MHz, CD₃OD, ppm): δ 1.82(s, 3H), 4.12(s, 2H), 5.14- 5.21(m,4H), 7.22-7.38(m, 12H), 7.91-7.94(m, 4H), 8.16(d, J=1.98Hz, IH)

IR (KBr, cm-¹): υ 3388, 2232, 1585, 1525, 1490, 1321, 1144, 1012

Example 5: Preparation of phosphoric acid ester of (R)-bicalutamide

5.7 g (8.3 mmol) of O-dibenzyl phosphoric acid ester of (R)- bicalutamide prepared in Example 4 was dissolved in 100 mL of methanol and 0.57 g of palladium 10% on carbon was added thereto, and stirred at room temperature under a hydrogen gas until the starting material disappears. The resulting mixture was filtered to remove carbon, washed with methanol, and the filtrate was concentrated under a reduced pressure. Then, 10 mL of ethyl acetate was added to the residue as white foam, completely dissolved while refluxing, and kept overnight in a refrigerator. The precipitate was filtered, washed with cold ethyl acetate, and dried at 40⁰C, to obtain 3.6 g (85%) of phosphoric acid ester of (R)-bicalutamide as a white crystalline powder.

Melting point: 196 to 200⁰C

Specific rotation: [α]_D ²⁷: -52° (c 1.0, MeOH)

1H-NMR (300MHz, CD₃OD, ppm): δ 1.83(s, 3H), 4.10(dd, J=7.85Hz,

J=14.8Hz, 2H), 7.25(t, J=8.72Hz, 2H), 7.88-8.06(m, 4H), 8.23(d, J=I .22Hz, IH)

IR(KBr, cm^"1): υ 3415, 2233, 1700, 1614, 1592, 1432, 1238, 1179, 1149, 1074 Example 6: Preparation of phosphoric acid ester disodium salt of bicalutamide (racemate)

2.0 g (3.9 mmol) of a phosphoric acid ester of bicalutamide was dissolved in 2 mL of methanol and a solution in which 0.32 g (7.8 mmol) of sodium hydroxide is dissolved in 2 mL of methanol was added thereto at 0⁰C, and stirred at room temperature for 30 min. 15 mL of isopropyl ether was added dropwise to the reaction solution and further stirred at room temperature for 3 hours. Then, the precipitate was filtered, washed with a cold mixed solvent of methanol and isopropyl ether (1 :5, v/v), and dried at 40⁰C, to obtain 1.63 g (75%) of phosphoric acid ester disodium salt of bicalutamide (racemate) as a white crystalline solid.

Melting point: 135 to 137°C

¹H-NMR (300MHz, CD₃OD, ppm): δ 1.70(s, 3H), 4.00(dd, J=38.6Hz, J=14.3Hz, 2H), 7.09(t, J=8.61Hz, 2H), 7.78(d, J=8.58Hz, IH), 7.89(dd, J=6.57Hz, J=2.1Hz, IH), 7.93-7.99(m, 2H), 8.14(d, J=I .72Hz, IH)

IR (KBr, cm^"1): υ 3353, 2232, 1526, 1431, 1381, 1291, 1241, 1141, 905, 512

Example 7: Preparation of phosphoric acid ester dicalcium salt of bicalutamide (racemate)

2.O g (3.9 mmol) of a phosphoric acid ester of bicalutamide was dissolved in 3 mL of methanol and a solution in which 0.44 g (7.8 mmol) of calcium hydroxide is dissolved in 2 mL of methanol was added dropwise thereto at 0⁰C, and stirred at room temperature for 2 hours. Then, the precipitate was filtered, washed with a cold mixed solvent of methanol and isopropyl ether (1 :1, v/v), and dried at 40⁰C, to obtain 1.63 g (71%) of phosphoric acid ester dicalcium salt of bicalutamide (racemate) as a white crystalline solid,

Melting point: 156 to 159°C

¹H-NMR (CDCl₃, ppm): δ 1.72(S, 3H), 3.98(dd, J=32.9Hz, J=14.0Hz, 2H), 7.07-7.13(m, 2H), 7.79(d, J=8.57Hz, IH), 7.89-7.97(m, 3H), 8.13(d, J=2.00Hz, IH)

IR (KBr, cm-¹): υ 3273, 2231, 1594, 1551, 1330, 1142, 982, 905

Example 8: Preparation of phosphoric acid ester monocalcium salt of bicalutamide (racemate)

2.62 g (4.72 mmol) of a phosphoric acid ester disodium salt of bicalutamide (racemate) was dissolved in 60 mL of a mixed solvent of water and acetone (5:1, v/v') and a solution in which 0.83 g (4.72 mmol) of calcium acetate monohydrate is dissolved in 3 mL of water was added dropwise thereto at room temperature, and stirred at 50⁰C for 1 hour. Then, the reaction solution was cooled to room temperature, stirred for 2 hours, and the precipitate was filtered and washed with a cold mixed solvent of water and acetone (5: 1, v/v'). The precipitate was dried at 40⁰C to obtain 2.36 g (73%) of phosphoric acid ester monocalcium salt of bicalutamide (racemate) as a white crystalline solid.

Melting point: 163 to 167°C

1H-NMR (300MHz, DMSO-J₆, ppm): 1.40-2.05(br, 3H), 3.72-3.80(br,

IH), 4.02-4.21(br, IH), 6.83-8.41(br, 7H)

IR (KBr, cm-¹): υ 3487, 2233, 1702, 1592, 1327, 1179, 1141, 1052, 1101

Example 9; Preparation of phosphoric acid ester disodium salt of (R)- bicalutamide

2.5 g (4.9 mmol) of a phosphoric acid ester of (R)-bicalutamide was dissolved in 2.5 mL of methanol and a solution in which 0.42 g (9.8 mmol) of sodium hydroxide is dissolved in 2.6 mL of methanol was added dropwise thereto at 0⁰C, and stirred at room temperature for 30 min. Then, 18 mL of isopropyl ether was added dropwise to the reaction solution and further stirred at room temperature for 3 hours. The resulting precipitate was filtered, washed with a cold mixed solvent of methanol and isopropyl ether (1 :5, v/v), and dried at 40⁰C, to obtain 2.14 g (79%) of phosphoric acid ester disodium salt of (R)- bicalutamide as a white crystalline solid.

Melting point: 125 to 128°C

Specific rotation: [α]_D ²⁷: -82° (c 1.0, MeOH)

¹H-NMR (300MHz, CD₃OD, ppm): δ 1.70(s, 3H), 3.95(dd, J=38.6Hz, J=14.3Hz, 2H), 7.00(t, J=8.61Hz, 2H), 7.78(d, J=8.58Hz, IH), 7.88(dd, J=6.57Hz, J=2.1Hz, IH), 7.90-7.99(m, 2H), 8.14(d, J=I .72Hz, IH) IR (KBr, cm^"1): υ 3348, 2233, 1535, 1429, 1370, 1285, 1241, 1140, 905, 510

Example 10: Preparation of phosphoric acid ester monocalcium salt of (R)- bicalutamide

2 g (3.61 mmol) of a phosphoric acid ester disodium salt of (R)- bicalutamide was dissolved in 45 mL of a mixed solvent of water and acetone

(5: 1, v/v') and a solution in which 0.64 g (3.61 mmol) of calcium acetate monohydrate is dissolved in 2.4 mL of water was added dropwise thereto at room temperature, and stirred at 5O⁰C for 1 hour. Then, the reaction solution was cooled to room temperature, stirred for 2 hours, and the precipitate was filtered and washed with a cold mixed solvent of water and acetone (5:1, v/v¹).

The precipitate was dried at 40⁰C to obtain 1.50 g (76%) of phosphoric acid ester monocalcium salt of (R)-bicalutamide as a white crystalline powder.

Melting point: 151 to 153°C

Specific rotation: [α]_D ²⁷: -93° (c 1.0, MeOH)

¹H-NMR (300MHz, DMSO-J₆, ppm): 1.40-2.1 l(br, 3H), 3.70-3.79(br, IH), 4.05-4.25(br, IH), 7.00-8.41(br, 7H)

IR (KBr₅Cm-¹)^ 3435, 2231, 1705, 1592, 1327, 1176, 1141, 1052, 1101

Experimental Example 1: Water solubility test

For the phosphoric acid ester of bicalutamide and monocalcium salt thereof prepared in each Example 2 and 8, the solubility test was carried out in pH 1.2 buffer prepared using distilled water, sodium chloride and hydrochloric acid solution (corresponding to the pH of the gastric juice) and in pH 6.8 buffer prepared using potassium dihydrogen phosphate and sodium hydroxide (corresponding to the pH in the intestinal juice) by a conventional method. The results were compared with that of bicalutamide. That is, bicalutamide, a phosphoric acid ester of bicalutamide, and a phosphoric acid ester monocalcium salt of bicalutamide were dissolved in a test solution at 20⁰C until they do not dissolve, filtered to remove insoluble materials, and the amount dissolved in 1 mL of the filtrate was analyzed using HPLC. The solubility of each sample was calculated by comparing the chromatograms of the samples with that of standard solution whose concentration is already known, and the results are shown in Table 1.

Experimental Example 2; Pharmacokinetic test

The bicalutamide phosphoric acid ester prepared in Example 2 and bicalutamide were each administered to rats (Harlan:Hsd (SD) BR rat, male, 8 weeks age, 5 rats/group) at dosage of 2 mg/kg, 10 mg/kg, 50 mg/kg, and 250 mg/kg as bicalutamide (vehicle: 0.5% Tween 80 aqueous solution, administration volume: 5 mL/kg), respectively, and 0.5mL of blood was then taken from jugular vein at intervals of 0.5, 1, 2, 4, 8, 12, 24, 48, and 72 hours after administration. Each blood was extracted with an organic solvent and the amount of bicalutamide present in plasma was determined by LC/MC/MS analysis (internal standard: ibuprofen). In order to evaluate bioavailability after oral administration, 5 mg of bicalutamide was dissolved in a 20% cremophor/saline solution and administered by intravenous injection. Then, blood was taken from jugular vein at intervals of 0.08, 0.25, 0.5, 1, 2, 4, 8, 12, 24, 48, and 72 hours and the amount of bicalutamide present in plasma was determined as described above.

Pharmacokinetic parameters, e.g., the area under the time-concentration curve (AUC₀-₇₂ and AUC₀.i_nf), the peak plasma concentration (C_max), the time to C_max (T_max), and the elimination half life (Ty₂), were calculated using

WinNonlin program (version 5.2, Pharsight, U.S.) from a plasma concentration curve of bicalutamide with various blood sampling times.

At this time, C_max and T_max were measured from direct observation and AUC_0-72 was calculated from 0 to 72 hours (last blood sampling time) using linear trapezoidal summation, and bioavailability (BA) after oral administration was calculated from following Equation I, using the areas under the time- concentration curve (AUCo-i_nf) after oral and intravenous administrations and the dosage thereof.

Bioavailability (BA, %) = [{(AUC₀._inf)_po / (AUC₀._inf)iv} ^x (Dose_lv /

Dose_po)] x 100

wherein,

(AUCo.i_nf)_Po is the area under the time-concentration curve after oral administration;

(AUCo-i_nf)iv is the area under the time-concentration curve after intravenous administration;

Dose_po is the dose for oral administration as bicalutamide; and

Dose_iv is the dose for intravenous administration as bicalutamide. The data of pharmacokinetic parameters according to doses of bicalutamide and bicalutamide phosphoric acid ester in rats are shown in Table 2, and all measured and calculated values are indicated as mean ± standard error.

In addition, the systemic exposure (the area under the time-concentration curve, AUCo-i_nf), the correlation between the systemic exposure and dosage, and the bioavailability after oral administration, which are measured for bicalutamide and bicalutamide phosphoric acid ester, are shown in Figs. 1, 2, and 3, respectively.

In the correlation between the systemic exposure and dosage as depicted in Fig. 2, the regression equation for the curve of systemic exposure based on the oral dosage was obtained using Excel 2003 program (Microsoft), and the regression constant (R²) values at the time was used to assess the linearity of systemic exposure according to the oral dosage. As shown in Fig. 2, the regression constant (R²) values in the curve of systemic exposure based on the dosages of bicalutamide and bicalutamide phosphoric acid ester was each assessed as 0.8060 and 0.9972, and thus, in case of bicalutamide phosphoric acid ester, it was confirmed that the straightness, i.e., linearity is well maintained.

While the invention has been described with respect to the above specific embodiments, it should be recognized that various modifications and changes may be made to the invention by those skilled in the art which also fall within the scope of the invention as defined by the appended claims.

Claims

What is claimed is:

1. A phosphoric acid ester of bicalutamide of Formula I or a pharmaceutically acceptable salt thereof:

2. The phosphoric acid ester of bicalutamide or pharmaceutically acceptable salt thereof of claim 1, wherein 50% or more of the phosphoric acid ester of bicalutamide or pharmaceutically acceptable salt thereof is of the (R)- enantiomeric form.

3. The phosphoric acid ester of bicalutamide or pharmaceutically acceptable salt thereof of claim 2, wherein 90% or more of the phosphoric acid ester of bicalutamide or pharmaceutically acceptable salt thereof is of the (R)- enantiomeric form.

4. The phosphoric acid ester of bicalutamide or pharmaceutically acceptable salts thereof of claim 1, wherein the pharmaceutically acceptable salt is selected from the group consisting of salts with sodium, potassium, calcium, magnesium, zinc, iron, ammonium, arginine, lysine, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, ethanolamine, diethanolamine, l-amino-2-propanol, 3-amino- 1-propanol, hexamethylenetriamine, piperidine, piperazine, pyrrolidone, morpholine, n-methylglucamine, creatinine, tromethamine, choline, and tetramethy lammonium .

5. The phosphoric acid ester of bicalutamide or pharmaceutically acceptable salt thereof of claim 4, wherein the pharmaceutically acceptable salt is selected from the group consisting of sodium, potassium, calcium, magnesium, arginine, lysine, n-methylglucamine, and choline salts.

6. The phosphoric acid ester of bicalutamide or pharmaceutically acceptable salt thereof of any one of claims 1 to 5, wherein the phosphoric acid ester of bicalutamide or pharmaceutically acceptable salt thereof is present in the form of a hydrate, solvate, or a mixture thereof.

7. A pharmaceutical composition for treating or reducing the risk of prostate cancer, comprising the phosphoric acid ester of bicalutamide of claim 1 or pharmaceutically acceptable salt thereof as an active ingredient.

8. The pharmaceutical composition of claim 7, wherein the amount of the phosphoric acid ester of bicalutamide or pharmaceutically acceptable salt as an active ingredient is 1 mg to 2,000 mg/single dose.

9. The pharmaceutical composition of claim 8, wherein the amount of phosphoric acid ester of bicalutamide or pharmaceutically acceptable salt as an active ingredient is 10 mg to 1,000 mg/single dose.

10. The pharmaceutical composition of claim 7, wherein the composition is a formulation for oral administration.

1 1. The pharmaceutical composition of claim 10, wherein the amount of the phosphoric acid ester of bicalutamide or pharmaceutically acceptable salt is 0.1 to 95% by weight based on the total amount of the single dose composition.

12. The pharmaceutical composition of claim 11, wherein the amount of the phosphoric acid ester of bicalutamide or pharmaceutically acceptable salt is 1 to 70% by weight based on the total amount of the single dose composition.

13. The pharmaceutical composition of claim 7, wherein the risk of prostate cancer is a secondary disease which may lead to prostate cancer.

14. The pharmaceutical composition of claim 13, wherein the secondary disease is: poor urinary flow, urinary frequency, urgency, or retention; repeated urinary tract infections; blood in the urine or semen; decreased ability to achieve or maintain erection, decreased sperm content of ejaculate; or low abdominal pain.