THE NEW TELMISARTAN ZINC SALT AND THE PREPARATION THEREOF

Technical Field

[1] The present invention relates to a telmisartan zinc salt with improved physico- chemical properties of the free acid of telmisartan which is an angiotensin II antagonist that is useful for the treatment of hypertensive diseases, and a method for preparing the same. Background Art

[2] The compound

2- [4- [ [4-methyl-6- ( 1 -methylbenzoimidazol-2-yl)-2-propylbenzoimidazol- 1 -yl] methyl] phenyl] benzoic acid (hereinafter, referred to as "telmisartan") is known from European Patent EP 502 314 Bl and has the following chemical structure:

[4] Telmisartan is known to be an angiotensin antagonist, particularly an angiotensin II antagonist which, by virtue of its pharmacological properties, may be used, for example, to treat hypertension and cardiac insufficiency, to treat ischemic peripheral circulatory disorders and myocardial ischaemia, to prevent the progression of cardiac insufficiency after myocardial infarction, and to treat diabetic neuropathy, glaucoma, and the like.

[5] Telmisartan was discovered and developed by Boehringer Ingelheim. Under the trademarks MICARDIS ^R and MICARDISPLUS ^R (combination with hydrochlorothiazide) the company markets telmisartan in 84 countries around the world, including the USA, Japan and European countries. Telmisartan is a member of the angiotensin II receptor blocker (ARB) class and is being investigated in the most ambitious and far-reaching research programme conducted with an ARB. In the clinical trial programmes ONTARGET, PROTECTION and PROFESS, over 58,000 patients have been enrolled to investigate the cardiovascular protective effects of MICARDIS ^R .

[6] The free acid of telmisartan hasa very limitedsolubility. For this reason, in the industrial production of telmisartan, commercially available free acid formulations of telmisartan are prepared by direct contact of telmisartan with a strong alkalizer such as sodium hydroxide. Such a production process is potentially dangerous to human health. In addition, quality reproducibility of the final formulation may vary depending on a period of reaction time. Physicochemical properties of telmisartan in the solid free acid form may also pose difficulties of direct application thereof to the human body, so many researches have been actively conducted to overcome the limited applicability of telmisartan.

[7] In order to overcome these disadvantages of telmisartan, for example, International

Publication Nos. WO2003/037876 and WO 2006/044754 disclose acid or base addition salts of telmisartan, and telmisartan preparations containing alkali metal ex- cipients.

[8] Further, European Patent EP 1 144 386 Bl, and International Publication Nos. WO

2003/037876 and WO 2006/050509 disclose sodium salts of telmisartan which are intended to overcome the disadvantages of the free acid of telmisartan.

[9] However, considering the ongoing discussion of the possibility that the blood pressure of hypertensive patients may be susceptible to changes in dietary sodium intake, sodium salts of telmisartan may cause additional problems in antihypertensive treatment (Hypertension 27, 481-490, 1996). Generally, additional intake of sodium over the normal level results in the presence of more fluids in blood vessels, which makes the heart to supply more blood to the body. Further, vascular constriction influenced by sodium intake inhibits the amount and flow of blood entering the heart, so the heart must pump more blood into a closed circulatory system of the human body. As a consequence, high sodium intake increases blood pressure.

[10] Taking into consideration only the easy manufacturability of a telmisartan formulation, a sodium salt of telmisartan may be an approximate solution to the problems associated with poor physicochemical properties of the free acid of telmisartan such as limited solubility and the like.However, giving consideration to the above-mentioned adverse effects of sodium intake on hypertensive patients, it can be seen that application of the telmisartan sodium salt as an antihypertensive drug inevitably involves problems in terms of safety.

[11] Further, WO 2006/050921 and EP 1 719 766 Bl disclose magnesium and calcium salts of telmisartan. However, the telmisartan magnesium and calcium salts suffer from disadvantages associated with poor properties of pharmaceutically important factors, e.g. high hygroscopicity and low thermal stability, as compared to the free acid form of telmisartan.

[12] To this end, there is a need for an addition salt of telmisartan which is ofhigh purity and high quality thus making it suitable for application to a pharmaceutical composition, in conjunction with improvements of formulation-related factors of tablet preparations such as solubility, solid rheology and electrostaticity, including high hygroscopicity and low stability which are disadvantages of telmisartan in the free acid form.

[13] Zinc is a metallic chemical element with the symbol Zn, atomic number 30 and atomic weight 65.39. Zinc was recognized as useful mineral since the 1950's. With the revelation that "dwarfism" and "hypogonadism" are due to zinc deficiency, a great deal of interest has been focused on the importance of zinc in human health. In the United States, the recommended intake for zinc was established in the 1970's. In Korea, the recommended dietary allowance (RDA) for zinc was first presented in 1995. Zinc is the ubiquitous mineral which is found in all animal tissues and is involved in epithelial healing or prostate function. In addition, it is known that zinc is essential for dermal or skeletal growth and maintenance and for the synthesis of nucleic acids and proteins. As examples of pharmaceutical products utilizing these pharmacological actions of zinc, commercially available zinc sulfate preparations may be mentioned. According to the Dietary Reference Intakes for Koreans (KDRIs) published by The Korean Nutrition Society in 2005, the recommended daily intake of zinc is in the range of 8 to 10 mg for adult males, 7 to 8 mg for adult females, 10 to 11 mg for pregnant women, and 13 mg for lactating women, respectively. The tolerable upper intake level of zinc is 35 mg for both adult males and females. Due to the above-mentioned validated safety of zinc, zinc gluconate, zinc oxide, and the like are used as food additives, whereas zinc stearate and the like are used as pharmaceutical excipients.

[14] As a result of a variety of extensive and intensive studies and experiments to solve the problems suffered by conventional free acids of telmisartan as discussed before, the inventors of the present invention have developed zinc salts of telmisartan which are pharmaceutically very excellent and are also superior in terms ofsafety. Disclosure of Invention Technical Problem

[15] Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a novel zinc salt of telmisartan which exhibits excellent pharmaceutical properties and high safety, by improving disadvantages of the free acid of telmisartan that is an angiotensin II antagonist. [16] It is another object of the present invention to provide a method for preparing a novel zinc salt of telmisartan. Technical Solution

[17] In accordance with an aspect of the present invention, the above and other objects can be accomplished by the provision of a high-purity zinc salt of 2- [4- [ [4-methyl-6- ( 1 -methylbenzoimidazol-2-yl)-2-propylbenzoimidazol- 1 -yl] methyl] phenyl] benzoic acid (telmisartan), which is pharmaceutically acceptable and is very useful as a pharmaceutical composition for the prevention or treatment of hypertensive diseases and/or cardiovascular diseases due to improved physicochemical properties of a drug compound and which is represented by Formula 1 below:

(Formula 1)

[19] The telmisartan zinc salt of the present invention is provided in the form of an ionically-bonded salt produced by the combination of two telmisartan molecules into a divalent zinc ion. The telmisartan zinc salt in accordance with the present invention may be prepared directly from telmisartan of Formula 1 per se, or otherwise may be obtained from the conversion of the ready-made telmisartan salt into a desired form.

[20] In accordance with another aspect of the present invention, there is provided a method for preparing a zinc salt of telmisartan including reacting telmisartan with a zinc compound in the presence of an organic solvent.

[21] For example, the preparation of the telmisartan zinc salt includes a) dissolving or suspending the free acid of telmisartan in an organic solvent at a given temperature higher than room temperature; b) dissolving the zinc compound in the organic solvent or adding the zinc compound in the solid form to the solution or suspension of Step a) to obtain a reaction mixture; and c) solidifying the mixture of Step b) under various temperature and solvent conditions, followed by filtration, washing and drying of the resulting solid to prepare a desired zinc salt of telmisartan.

[22] Preferred examples of the zinc compound that can be used in the preparation method of the present invention may include zinc hydroxide, zinc acetate, zinc chloride, zinc bromide, zinc iodide, and the like. Although various equivalents of the zinc compound may be used relative to one mole of the telmisartan free acid, an amount of the zinc compound is preferably 0.5 mol or higher. The reaction temperature is in the range of 25 ⁰ C to 100 ⁰ C. The salt deposition temperature is preferably in the range of -1O ⁰ C to 100 ⁰ C.

[23] Preferred examples of the organic solvent that can be used in the preparation method of the present invention may include lower alcohols such as methanol, ethanol, iso- propanol and butanol; ethers such as 1,4-dioxane, tetrahydrofuran, diethylether and isopropylether; amides such as dimethylformamide and diethylacetamide ketones such as acetone and methylethylketone; esters such as isopropylacetate; halogenated hydrocarbons such as chloroform and dichloromethane; lower hydrocarbons such as hexane, heptane and octane; dimethylsulf oxide and water. These solvent compounds may be used alone or in any combination thereof.

[24] The telmisartan zinc salt of the present invention exhibits significantly improved physicochemical properties of specific volume and electrostaticity of solids in conjunction with high solubility, good stability and non-hygroscopicity, as compared to known telmisartan. Therefore, pharmaceutical compositions containing the telmisartan zinc salt of the present invention can be effectively used for the treatment and prevention ofhypertension-related diseases.

[25] Further, even if the patient of interest takes the telmisartan zinc salt of the present invention at a maximum daily dose (80 mg in terms of telmisartan), an amount of the zinc salt to be absorbed into the body is only 5 mg which is below the recommended daily intake of zinc. Further, upon considering the recent report demonstrating that hypertension may be caused due to zinc deficiency (Pediatr. Res. 58(4), 672, 2005), it can be said that the telmisartan zinc salt is therapeutically or prophylactically beneficial for hypertension.

[26] Accordingly, the present invention provides a pharmaceutical composition for treatment or prevention of hypertensive diseases and/or cardiovascular diseases, containing a telmisartan zinc salt as an active ingredient and one or more pharmaceutically acceptable carriers.

[27] A dose of the telmisartan zinc salt in the composition of the present invention is very variable. As to the usual adult dose, an effective daily dose of the telmisartan zinc salt is in the range of about 10 to 100 mg, preferably 20 to 90 mg. The dosage and number of dosagescan be easily determined by the attending physician, depending on characteristics of formulations, weight and condition of the subject, administration routes, etc.

[28] As used herein, the term "pharmaceutically acceptable carrier" encompasses any of the standard pharmaceutically accepted carriers which are used in known pharmaceutical formulations such as sterile solutions, tablets, coated tablets and capsules. Typically such carriers contain excipients such as starch, milk, sugar, certain types of clay, gelatin, stearic acid, talc, vegetable fats or oils, gums, glycols, or other known excipients. Such carriers may also include flavor and color additives or other ingredients. Compositions containing such carriers may be formulated by well known conventional methods.

[29] Administration of the pharmaceutical composition in accordance with the present in- ventionis by any route including oral, rectal, injection. Most preferred are oral compositions such as tablets, capsules, granules, etc.

[30] In accordance with a further aspect of the present invention, there is provided a use of a telmisartan zinc salt for the preparation of a pharmaceutical composition for the treatment or prevention of hypertensive diseases and/or cardiovascular diseases.

[31]

[32] In accordance with another aspect of the present invention, there is provided a method for preventing or treating of hypertensive diseases and/or cardiovascular diseases, in comprising administering a therapeutically effective amount of a telmisartan zinc salt to mammal including a human in need of treatment or prevention of hypertensive diseases and/or cardiovascular diseases.

Advantageous Effects

[33] As will be specifically demonstrated hereinafter, the present invention enables high- purity production of a telmisartan zinc salt with no introduction of an additional purification process. The thus-produced telmisartan zinc salt exhibits excellent pharmaceutical properties associated with the solubility, stability and non-hygroscopicity, as well as improvements in physicochemical properties such as specific volume and elec- trostaticity of solids, which are required for practical commercializationof drug compounds. Therefore, the telmisartan zinc salt of the present invention in combination with a pharmaceutically acceptable carrier can be usefully employed as an active ingredient of antihypertensive drugs or cardio and vascular protective- pharmaceutical compositions. Mode for the Invention

[34] Now, the present invention will be described in more detail with reference to the following Examples. These examples are provided only for illustrating the present invention and should not be construed as limiting the scope and spirit of the present invention.

[35]

[36] Hereinafter, ¹ H NMR data given in the following Examples are the values measured using a Bruker UltraShield™ 400 (400 MHz) spectrometer. Unless otherwise specified, all reagents and solvents were purchased from Aldrich and Acros.

[37]

[38] HPLC conditions used for the measurement of the purity and content of telmisartan zinc saltsin the present invention were the same as those of the telmisartan analysis in the European Pharmacopoeia 6.2.

[39]

[40] Example 1: Synthesis of telmisartan zinc salt

[41] 30 g of telmisartan and 600 mL of acetone were refluxed at 53 ⁰ C to prepare a suspension to which 4.4 g of zinc chloride was then added, followed by stirring at that temperature for 2 hours. The reaction mixture was concentrated to 300 mL at 4O ⁰ C and 50 mbar under reduced pressure, followed by stirring at room temperature for 2 hours to precipitate a white solid. The resulting solid was washed with cold acetone, filtered, and dried under vacuum to obtain a telmisartan zinc salt.

[42]

[43] Yield: 30 g (93%), white powder

[44] Purity (HPLC): 99.81 %

[45] ¹ H NMR (400MHz, DMSO-d ⁶ )δ(ppm): 7.73-7.60 (4H, m), 7.49-7.40 (3H, m),

7.31-7.22 (5H, m), 7.17-7.16 (2H, m), 5.59 (3H, s), 3.79 (3H, s), 2.95-2.91 (2H, t), 2.61 (3H, s), 1.86-1.77 (2H, m), 1.01-0.97 (3H, t)

[46]

[47] Example 2: Synthesis of telmisartan zinc salt

[48] 150 mL of dimethylsulf oxide was added to 30 g of telmisartan, and the mixture was heated with stirring to 5O ⁰ C until a clear solution was obtained. To the resulting solution was added 4.4 g of zinc chloride, followed by stirring at that temperature for about one hour. The reaction mixture was cooled to room temperature and 600 mL of acetone was added thereto, followed by stirring to precipitate a white solid. The result- ingsolid was washed with cold acetone, filtered and dried under vacuum to obtain a telmisartan zinc salt.

[49]

[50] Yield: 27 g (85%), white powder

[51] Purity (HPLC): 99.91%

[52] ¹ H NMR (400MHz, DMSO-d ⁶ )δ(ppm): 7.73-7.60 (4H, m), 7.49-7.40 (3H, m),

7.31-7.22 (5H, m), 7.17-7.16 (2H, m), 5.59 (3H, s), 3.79 (3H, s), 2.95-2.91 (2H, t), 2.61 (3H, s), 1.86-1.77 (2H, m), 1.01-0.97 (3H, t)

[53]

[54] Example 3: Synthesis of telmisartan zinc salt

[55] 30 g of telmisartan and 600 mL of tetrahydrofuran were refluxed at 65 ⁰ C to prepare a suspension to which 4.4 g of zinc chloride was then added, followed by stirring at that temperature for 2 hours. The reaction mixture was concentrated to 300 mL at 4O ⁰ C and 50 mbar under reduced pressure, followed by stirring at room temperature for 2 hours to precipitate a white solid. The resulting solid was washed with cold tetrahydrofuran, filtered, and dried under vacuum to obtain a telmisartan zinc salt.

[56]

[57] Yield: 29 g (90%), white powder

[58] Purity (HPLC): 99.79%

[59] ¹ H NMR (400MHz, DMSO-d ⁶ )δ(ppm): 7.73-7.60 (4H, m), 7.49-7.40 (3H, m),

7.31-7.22 (5H, m), 7.17-7.16 (2H, m), 5.59 (3H, s), 3.79 (3H, s), 2.95-2.91 (2H, t), 2.61 (3H, s), 1.86-1.77 (2H, m), 1.01-0.97 (3H, t)

[60]

[61] Example 4: Synthesis of telmisartan zinc salt

[62] 30 g of telmisartan and 100 mL of dimethylsulf oxide were mixed and heated with stirring to 5O ⁰ C until a clear solution was obtained. To the resulting solution was added 4.4 g of zinc chloride, followed by stirring at that temperature for about one hour. The reaction mixture was cooled to room temperature and 300 mL of tetrahydrofuran was added thereto, followed by stirring at 5 ⁰ C for 2 hours to precipitate a white solid. The resultingsolid was washed with cold tetrahydrofuran, filtered and dried under vacuum to obtain a telmisartan zinc salt.

[63]

[64] Yield: 27.8 g (87%), white powder

[65] Purity (HPLC): 99.93%

[66] ¹ H NMR (400MHz, DMSO-d ⁶ )δ(ppm) : 7.73-7.60 (4H, m), 7.49-7.40 (3H, m),

7.31-7.22 (5H, m), 7.17-7.16 (2H, m), 5.59 (3H, s), 3.79 (3H, s), 2.95-2.91 (2H, t), 2.61 (3H, s), 1.86-1.77 (2H, m), 1.01-0.97 (3H, t)

[67]

[68] Comparative Example 1: Synthesis of telmisartan sodium salt

[69] 30 g of telmisartan was dissolved in 600 mL of ethanol and 2.4 g of sodium hydroxide was added thereto, followed by stirring at room temperature for about 1 hour. Ethanol which was used as a solvent of the reaction mixture was removed by dis- tillationunder reduced pressure. 100 mL of ethanol was added to the resulting solid and the mixture was dissolved under reflux. 500 mL of methyl t-butyl ether was added to the reaction mixture over one hour, and the mixture was cooled to room temperature to precipitate a white solid. The resulting solid was filtered and dried under vacuum to obtain a telmisartan sodium salt.

[70]

[71] Yield: 35.3 g (81%), white powder [72] Purity (HPLC): 99.14%

[73] ¹ H NMR (400MHz, DMSO-d ⁶ )δ(ppm): 7.73-7.60 (4H, m), 7.49-7.40 (3H, m),

7.31-7.22 (5H, m), 7.17-7.16 (2H, m), 5.59 (3H, s), 3.79 (3H, s), 2.95-2.91 (2H, t),

2.61 (3H, s), 1.86-1.77 (2H, m), 1.01-0.97 (3H, t) [74]

[75] Comparative Example 2: Synthesis of telmisartan magnesium salt

[76] 30 g of telmisartan was suspended with stirring in 1500 mL of methanol. 2.4 g of magnesium methoxide was added to the resulting suspension which was then refluxed at a temperature of 60 to 65 ⁰ C for about 12 hours. The reaction mixture was filtered and methanol was removed by distillation under reduced pressure. The residue was dried under vacuum to obtain a telmisartan magnesium salt. [77]

[78] Yield: 28.9 g (83%), pale yellow powder

[79] Purity (HPLC): 99.21%

[80] ¹ H NMR (400MHz, DMSO-d ⁶ )δ(ppm): 7.73-7.60 (4H, m), 7.49-7.40 (3H, m),

7.31-7.22 (5H, m), 7.17-7.16 (2H, m), 5.59 (3H, s), 3.79 (3H, s), 2.95-2.91 (2H, t),

2.61 (3H, s), 1.86-1.77 (2H, m), 1.01-0.97 (3H, t) [81]

[82] Comparative Example 3: Synthesis of telmisartan calcium salt

[83] 30 g of telmisartan was suspended with stirring in 1500 mL of methanol. To the resulting suspension was added 2.4 g of calcium hydroxide, followed by reflux at 60 to

65 ⁰ C for about 12 hours. The reaction mixture was filtered and methanol was removed by distillationunder reduced pressure. The residue was dried under vacuum to obtain a telmisartan calcium salt. [84]

[85] Yield: 29.7 g (87%), light white powder

[86] Purity (HPLC): 99.24%

[87] ¹ H NMR (400MHz, DMSO-d ⁶ )δ(ppm): 7.73-7.60 (4H, m), 7.49-7.40 (3H, m),

7.31-7.22 (5H, m), 7.17-7.16 (2H, m), 5.59 (3H, s), 3.79 (3H, s), 2.95-2.91 (2H, t),

2.61 (3H, s), 1.86-1.77 (2H, m), 1.01-0.97 (3H, t) [88] [89] Experimental Example 1: Purity of telmisartan salts prepared in Examples 1 to

4 and Comparative Examples 1 to 3 [90] Using telmisartan free salts with purity of 99.2% and 98.5%, test samples were prepared according to the procedure described in Examples 1 to 4 and Comparative

Examples 1 to 3. Purity of the samples was measured by HPLC. The results obtained are given in Table 1 below. [91] [Table 1]

[93] As can be seen from the results of Table 1 , the samples of Comparative Examples 1 to 3 exhibited no improvement in purity upon the preparation of telmisartan salts, whereas the samples of Examples 1 to 4 exhibited a significant increase in purity, thus confirming excellent purifying effects. With simple preparation of telmisartan addition salts (as illustrated in Examples 1 to 4) from poorly-soluble free acid forms of telmisartan which suffers from difficulties in the introduction of an additional purification process due to low solubility, it was found possible to achieve high purity of telmisartan which is pharmaceutically very suitable.

[94] [95] Experimental Example 2: Precipitabilitv of telmisartan salts [96] Generally, a poorly-soluble drug, even if it is dissolved in a medium, is deposited and precipitated again when solubility of the drug is poor. This poor solubility may be a factor that decreases oral absorption of the drug, so the evaluation of the precipitability of the drug becomes an evaluation item for the stability of an oral drug. Taking into

_* account 900 mL of purified water as a medium typically used in a dissolution test and the maximum daily dose, purified water was added to the free acid of telmisartan and the samples of Examples 1 and 3, Comparative Examples 1 to 3, which were each dissolved in 1 mg/mL of methanol, thereby preparing aqueous solutions containing 0.1 mg telmisartan/mL. Thereafter, these aqueous solutions were allowed to stand at room temperature under shading, and telmisartan contents of the samples were measured by HPLC, at zero time and after 24 hours of placement of the samples in containers. The results obtained are given in Table 2 below. [97] [Table 2]

[99] As can be seen from the results of Table 2, the commercially available telmisartan free acid was almost precipitated leaving only about 5% of the original mass, whereas Examples 1 and 3 exhibited significantly improved properties in precipitability, as compared to the free acid form of telmisartan. Therefore, the telmisartan zinc salts of the present invention have superior solubility in aqueous solutions, and very low probability of deposition and consequent precipitation (low precipitability) in an aqueous solution state, which are advantageous for the absorption of drugs.

[100] [101] Experimental Example 3: Hvgroscopicity of telmisartan salts [102] Low hygroscopicity is a very important factor for practical processing and storage of pharmaceutical products, among various properties required for drug compounds to be used as pharmaceutical raw materials. For the measurement of hygroscopicity, a telmisartan free acid and individual samples of Examples 1 and 2, and Comparative Examples 1 to 3 were dried under vacuum (P ₂ O5, for one day or more), and initial water contents of the samples were measured using a Karl Fisher method. Thereafter, amounts of sorbed water were automatically measured at 25°C and relative humidity (RH) of 15, 35, 55, 75 and 95%, respectively, using a hygroscopicity measurement apparatus (Model No. Hydrosorb 1000, manufactured by Quantachrome Instruments). The results obtained are given in Table 3 below. In this connection, it should be noted that the initial water content was defined as a water content of the test sample which will exhibit no further decrease in weight, after the drying wascontinuously and thoroughly conducted.

[103] [Table 3]

[105] As can be seen from the results of Table 3, the telmisartan free acid and the samples of Examples 1 and 2 exhibited very low hygroscopicity of about 0.5% over the entire range of relative humidity where the experiments were carried out, thus representing that a pharmaceutical raw material can be stably stored even when it is exposed to moisture in the air. On the other hand, each sample of Comparative Examples 1 to 3 had very poor properties as a pharmaceutical raw material, since they exhibit geo- metrically increased absorption of atmospheric moisture as the relative humidity increases. Giving particular consideration to the regulations that telmisartan should be managed to have a water content of less than 1 % according to the national standards for drug substances published by the Food and Drug Administration (FDA) and telmisartan having the above-specified water content of more than 1% should not be used for pharmaceutical applications, the samples of Comparative Examples 1 to 3 were found to have excessively high hygroscopicity which is not acceptable for drug formulations. On the other hand, it was confirmed that the telmisartan zinc salts of the present invention have excellent non-hygroscopic properties thus making it not absorb moisture, even when they were exposed to ambient humidity conditions.

[106] [107] Experimental Example 4: Stability of telmisartan salts [108] Excellent solid-state stability of drug substances is very important for the formulation of tablets and capsules. In order to evaluate the stability of the drug compound of interest, the samples of Examples 1 and 2,and Comparative Examples 1 to 3 were stored under severe conditions of 100 ⁰ C (airtight state) for one week, and the relative thermal stability of the samples was measured by HPLC. The results obtained are given in Table 4 below.

[109] [Table 4]

[1 11] As a result, it was demonstrated that the telmisartan free acid and the samples of Examples 1 and 2 exhibited excellent thermal stability, whereas the samples of Comparative Examples 1 to 3 exhibited relatively poor thermal stability.

[112] [113] Experimental Example 5: Electrostaticity of telmisartan salts [114] Generally, compounds with a large build up of static electricity may cause problems associated with sticking of the compounds to the equipment and apparatus during the quantitative analysis and manufacture of pharmaceutical formulations. Therefore, in order to confirm the low electrostaticity of the compounds of the present invention, electrostatic properties of the telmisartan free acid and the samples of Examples 1 and 3, and Comparative Examples 1 to 3 were tested using a Faraday Cage apparatus (Model No. 325 Faraday Cage with SmartStir™, manufactured by AMETEK PAR) that is designed to measure static electricity of a subject material under the shielding of ?n external electrostatic field.The results obtained are given in Table 5 below.

[1 15] [Table 5]

[117] As a result, the samples of Examples 1 and 3, exhibited decreased static electricity (low eleclrostaticity), as compared to the telmisartan free acid and the samples of Comparative Examples 1 to 3, thus confirming that the compounds of the present invention have excellent processability taking into consideration instrument rubbing that may take place during the preparation of pharmaceutical formulations.

[1 18] [119] Experimental Example 6; Specific volume (volume per unit weight) of telmisartan salts

[120] Generally when a certain compound as a drug substance is formulated into a tablet, the specific volume of solid (volume per same unit weight) may affect the process convenience and formulation size. When the specific volume is large, this may result in very poor processability. Therefore, in order to confirm that telmisartan salts of the present invention have a low specific volume, the telmisartan free acid and the samples of Examples 1 and 3, and Comparative Examples 1 to 3 were placed in graduated cylinders. From a vertical height of 10 cm, free fall of the cylinders was repeated 20 times or more such that tapping of the samples was carried out to achieve sufficient compacting of the contents. The specific volume values of test samples were measured before and after tapping. The results obtained are given in Table 6 below.

[121] [Table 6]

Telmisartan Ex; i Ex. 3 Comp. Comp. Comp. free acid Ex. 1 Ex. 2 Ex. 3

Untapped 12.34 mL/g 3 .22 mL/g 3 .86 mL/g 10.88 mL/g 8 .95 mL/g 9 .85 mL/g

Tapped 8.93 mL/g 2 .31 mL/g 2 .77 mL/g 6.54 mL/g 5 .12 mL/g 4 .41 mL/g

[123] When compared with the telmisartan free acid and the samples of Comparative

Examples 1 to 3, the samples of Examples 1 and 3 exhibited a noticeable reduction of the specific volume. Powdered drug substances usually have high specific volumes and are therefore designed into suitable dosage forms (tablets or capsules) always after compression molding thereof. Therefore, when the specific volume is large, the pharmaceutical processability of the drug substance becomes very poor. The telmisartan zinc salts of the present invention have excellent physicochemical properties in terms of pharmaceutical processability. Industrial Applicability

[124] As apparent from the above description, the present invention enables high-purity production of a telmisartan zinc salt with no introduction of an additional purification process. The thus-produced telmisartan zinc salt exhibits excellent pharmaceutical properties associated with the solubility, stability and non-hygroscopicity, as well as improvements in physicochemical properties such as specific volume and electro- staticity of solids,which are required for practical commercialization of drug compounds. Therefore, the telmisartan zinc salt of the present invention in combination with a pharmaceutically acceptable carrier can be usefully employed as an active ingredient of antihypertensive drugs or cardio and vascular protective- pharmaceutical compositions.