FORM 2

THE PATENTS ACT, 1970
(39 OF 1970)
COMPLETE SPECIFICATION
(See section 10)
CRYSTALLINE HYDRATE OF HYPOGLYCEMIC AGENT
SUN PHARMACEUTICAL INDUSTRIES LTD.
A company incorporated under the laws of India having their office at ACME PLAZA, ANDHERI-KURLA ROAD, ANDHERI (E), MUMBAI-400059, MAHARASHTRA, INDIA.
The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed.

CRYSTALLINE HYDRATE OF HYPOGLYCEMIC AGENT
The present invention relates to crystalline hydrate of hypoglycemic agent, compound of formula 1, commonly known as nateglinide (INN name) and its pharmaceutical compositions. Compound of formula I is useful in the treatment of type II diabetes.

BACKGROUND OF THE INVENTION
United States Patent No. 4,816,484 (assigned to Novartis; referred to herein as '484 patent) discloses D-phenylalanine derivatives, including compound of formula I, and process for their preparation. The compound of formula I obtained is recrystallized from aqueous methanol to yield crystalline product with a melting point of 129-130°C.
United States Patent No. 5,463,116 (assigned to^Novartis) designates the crystals obtained by '484 patent as form B, which are unstable to mechanical grinding. It discloses another crystal form, Form H having a melting range of 136-142°C with enhanced stability. Form H is prepared by two methods viz. crystallizing from solvent in which compound of formula 1 is completely or incompletely soluble or by dispersing in a solvent or mixture of solvents.
United States Patent Application Publication 2004/0116526 Al (assigned to Teva) claims six new polymorphic forms of compound of formula I, designated as D, F, G, I, O and T. This patent designates the hydrate of compound of formula I prepared by following the example B3 of United States Patent No. 5,463,116 as Form Z. Form Z has been characterized by water content of about 10 to 50%, Differential Scanning Calorimetry (DSC), Powder X-Ray Diffractometry (XRD) and Infra Red spectroscopy (IR).
PCT publication 03/022251 filed by Alembic Limited prepares form AL by dissolving compound of formula 1 in a water miscible polar solvent selected from acetonitrile, dimethylformamide and
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dimethylacetamide at 60 to 75°C and precipitating at 28 to 35°C. Form AL has a melting range of 174-178°C.
OBJECT OF THE INVENTION
The object of the present invention is to provide crystalline hydrate of nateglinide with improved crystal characteristics.
It is another object of the present invention to provide a pharmaceutical composition comprising crystalline hydrate of nateglinide.
SUMMARY OF THE INVENTION
The present invention provides crystalline hydrate of hypoglycemic agent, compound of formula I, with water content of about 2 to about 7% by weight.
The present invention further provides a pharmaceutical composition comprising crystalline hydrate of hypoglycemic agent, compound of formula I, with water content of about 2 to about 7% by weight and pharmaceutically acceptable excipients wherein the composition is bioequivalent to nateglinide formulations commercially available in the United States of America on the date of filing of this application.
DETAILED DESCRIPTION OF THE INVENTION
We have found crystalline hydrate of nateglinide with water content of about 2 to about 7 % wt / \vt, having fusion point of about 105°C by Differential Scanning Calorimetry (DSC). Further solid-state techniques like Powder X-Ra'y Diffractometry (XRD) and Infra Red spectroscopy (IR) exhibit characteristic peaks similar to that disclosed for form Z.
The crystalline hydrate of nateglinide exhibits an infrared absorption spectrum in potassium bromide as disclosed for Form Z.
The crystalline hydrate of nateglinide is characterized by the DSC data: Fusion temperature at about 105 °C at a heating rate of 20 °C per minute. (Fig. 1)
The crystalline hydrate of hypoglycemic agent, compound of formula I, has water content of about 2 to about 7 % by weight, preferably monohydrate.
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The crystalline hydrate of nateglinide of the present invention may be advantageously prepared in a symmetrical form having an aspect ratio equal to or less than about 2. Generally, crystals with large aspect ratios for e.g. needle-shaped crystals, have poor flow properties.
The crystalline hydrate of nateglinide has Volume Mean Diameter (VMD) less than about 5 micron.
According to the present invention the crystalline hydrate of nateglinide may be prepared by a process comprising dissolving compound of formula I in organic solvent(s) containing water, heating and cooling, if required, and separating crystalline hydrate of compound of formula I.
Alternatively, crystalline hydrate of nateglinide may be prepared by directly dissolving compound of formula I, in an alkali or alkaline earth metal hydroxide solution followed by acidification of the aqueous solution.
Yet another method may involve alkaline hydrolysis of ester of nateglinide such as Ci to C6 alkyl or aralkyl or alkylaryl ester in an organic solvent followed by neutralization with acid to yield crystalline hydrate of hypoglycemic agent of compound of formula I.
The organic solvent may be selected from the group consisting of aliphatic or aromatic or cyclic hydrocarbon such as n-pentane, n-hexane, n-octane, cyclohexane, toluene and the like; halogenated aliphatic or aromatic hydrocarbons such as dichloromethane, chlorobenzene and the like; alkanols such as methanol, ethanol, t-butanol, isopropanol, cyclohexanol and the like; ethers such as diethylether, tetrahydrofuran, dioxane and the like; ketones such as acetone, methylethylketone, cyclohexanone and the like; nitriles such as ■ acetonitrile and the like; amides such as dimethylformamide, dimethylacetamide and the like; esters such as ethylacetate, butylacetate and the like.
The crystallization step may be carried out at higher, ambient or lower temperature.
Isolation of the crystalline hydrate of nateglinide may be achieved by filtration/centrifugation and drying. Filtration may be carried out in the presence or absence of vacuum. Drying may be carried out at ambient temperature in the presence or absence of vacuum.
Crystalline hydrate of nateglinide is non hygroscopic and stable at ambient conditions.
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Pharmaceutically active compounds may exist as several different polymorphs, which are characterized by different physical and chemical properties, such as difference in melting point, apparent solubility, chemical reactivity, dissolution rate, optical and electrical properties, vapor pressure, density, and the like. The therapeutic effect of a pharmaceutically active compound depends on the blood plasma levels of the compound, which in turn depends on the amount of the compound absorbed. Absorption of the compound is dependent on the solubility of the compound in the physiologic environment. Hence, use of a different polymorph of the same compound may not provide similar blood plasma levels. For example, Abbott's Ritonavir, a compound useful as an antiviral compound, had to be withdrawn from the market since the compound changed to another polymorphic form during manufacturing process, the new form being only half as soluble as the first. Hence, therapeutically effective blood levels of ritonavir were not being achieved.
Nateglinide is practically insoluble in water. A change in crystal form can affect the dissolution rate and thus the bioavailability of a drug, whose absorption is dissolution rate limited. Thus, a change in crystal form of nateglinide raises concerns of bioavailability. Pharmaceutical compositions comprising the nateglinide crystal form of the present invention have been found that provide essentially the same bioavailability of nateglinide as that provided by the commercially available preparation.
The phrase "essentially the same bioavailability" as used herein means that if a pharmaceutical composition comprising nateglinide crystal form of the present invention and a pharmaceutically acceptable carrier is tested in a crossover study (usually comprising a cohort of at least 10 or more human subjects), the average Area Under the Curve (AUC) and/or the Cmax for each crossover group is at least 80% of the (corresponding) average AUC and/or Cmax observed when the same cohort of subjects is dosed with the nateglinide formulation whose New Drug Application (NDA) received approval of United States Food and Drug Administration (USFDA). Use of AUCs, Cmax and crossover studies is, of course well understood in the art. It may also be noted that the NDA product is approved for marketing on the basis of its therapeutic efficacy and safety demonstrated in human studies. The therapeutic efficacy and safety parameter may change if there is a change in bioavailability and thus once the NDA is approved, then it continues to be manufactured in a reproducible manner to provide the same bioavailability as the originally approved product. If there is a change in the manufacturing process, then the NDA holder must submit to the USFDA data demonstrating that the bioavailability of the product obtained using the new process is the same as that of the originally approved product. If there is a significant change in bioavailability of the product such that the therapeutic efficacy of the drug is affected, then the NDA holder will no longer be able to
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market the product using the approval received on the original product, and will instead need to file a NDA for the new product to obtain USFDA approval for it.
In preferred embodiments of the present invention, the pharmaceutical compositions comprising nateglinide crystal form of the present invention are bioequivalent to commercially available preparations of nateglinide. Approval of a generic version (Abbreviated New Drug Application, ANDA) of a proprietary drug (New Drug Application, NDA) by the Food and Drug Administration (FDA), as mentioned above, requires demonstration of "chemical equivalence" (similar quantities and availability of the active ingredient in proprietary and generic formulations), and "bioequivalence" (defined by absorption parameters generally falling between 80% and 125% of those obtained with the proprietary agent under the same testing conditions). Hence, a generic drug formulation to be approved by the FDA, has to be bioequivalent to the reference listed drug or the proprietary formulation. The present invention provides a pharmaceutical composition for the treatment of diabetes mellitus that releases nateglinide in a manner to provide desirable blood level profile of nateglinide that provides efficacy in the treatment of diabetes. For example, when administered as a single dose in fasted state to healthy human subjects it provides area under the plasma concentration-time curve (AUC) which is comparable to that provided by the pharmaceutical composition of nateglinide commercially available in the United States of America in April 2004. Alternatively, it provides peak plasma levels (CnBx) that are comparable with those provided by the pharmaceutical composition of nateglinide commercially available in the United States of America in April 2004. Herein, the term comparable means that 90 percent confidence intervals for the ratio of the population geometric means between the pharmaceutical composition of the present invention and the nateglinide oral drug delivery system commercially available in the United States of America, namely Startix®, based on log-transformed data, is contained in the limits'of 70-135 percent for AUC and Cniax. More preferred embodiments of the present invention are bioequivalent to nateglinide drug delivery systems commercially available in the United States of America. Bioequivalence may be determined according to United States Food and Drug Administration (USFDA) guidelines and criteria.
The pharmaceutical composition of the present invention uses crystalline nateglinide hydrate in an amount ranging from about 5mg to about 800mg. The pharmaceutical composition of the present invention includes pharmaceutically acceptable excipients that are conventionally used to obtain an oral dosage form. Examples of pharmaceutically acceptable excipients that may be used in the present invention include, but are not limited to, disintegrants such as starch, cellulose derivatives, gums, crosslinked polymers, carbonates and bicarbonates of alkali and alkali earth metals, and the like; binders such as starch, gelatin, sugars, cellulose derivatives, polyvinylpyrrolidone and the like;
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lubricants such as talc, magnesium stearate, colloidal silicon dioxide, polyethylene glycol and mixtures thereof; wicking agents such as microcrystalline cellulose, silicified microcrystalline cellulose and the like, and mixtures thereof. The excipients are used in amounts such that the pharmaceutical composition obtained is bioequivalent to commercially available pharmaceutical formulations of nateglinide.
The pharmaceutical composition of the present invention may be prepared by the conventional process of wet granulation, dry granulation or direct compression, using methods and facilities known to a person skilled in the pharmaceutical art.
The pharmaceutical composition of the present invention may be prepared by the conventional process of wet granulation, dry granulation or direct compression, using methods and facilities known to a person skilled in the pharmaceutical art, and utilizing conventionally used pharmaceutically acceptable excipients. Crystalline hydrate of hypoglycemic agent, compound of formula I, is found to be hydrophilic raising no concern during wet granulation as well as in dry compaction process. The crystalline hydrate of hypoglycemic agent, compound of formula I, as such or micronised, showed good compressibility. Granules prepared with either wet granulation or dry compaction process yield tablets with satisfactory crushing strengths, without any problems during compression. The aspect ratio of the crystalline compound of the present invention is such that it provides desirable flow properties to the compound. The compound can be easily mixed with pharmaceutical excipients and has no evidence of any significant static charges.
Crystalline hydrate of hypoglycemic agent, compound of formula I, showed good stability towards mechanical stress exerted during granulation process. There is no change in XRD pattern during processing and storage of tablet formulation. It is also stable to micronization process.
X-Ray diffractogram of hydrate of compound of formula I was compared with X-Ray diffractogram of synthetic mixture of hydrate of compound of formula I with placebo, granules and tablet. The characteristic peak positions and peak heights were identical for hydrate of compound of formula I, synthetic mixture of hydrate of compound of formula I with placebo, granules and tablet. This suggests no change in polymorphic form.
Compound of formula I may be synthesized by any prior known method such as in United States Patent No. 4,816,484 or our Indian co-pending application 860/MUM/2004 and then crystallized by
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the process of the present invention to yield Crystalline hydrate of hypoglycemic agent, compound of formula I.
The invention is further illustrated but not restricted by the description in the following examples.
EXAMPLES
Example 1: Process for the preparation of crystalline hydrate of nateglinide :
100 g of methyl ester of compound of formula I was added to tetrahydrofuran and water. Aqueous potassium hydroxide solution was added to the reaction mixture slowly with stirring at room temperature. The reaction mixture was stirred for 3-5 hours. After completion of reaction, water was added to the reaction mixture. The reaction mixture was filtered and acidified with 5N HC1. The product was extracted with methylene dichloride and treated with aqueous potassium hydroxide. The organic layer was discarded and the aqueous layer was degassed t) remove traces of methylene dichloride. To the aqueous layer 5 N HC1 was then added dropwise with stirring at room temperature. The resultant suspension was stirred for 3-4 hours at room temperature. The product was filtered and washed with water and dried in oven at 40°C to get crystalline hydrate of nateglinide (Water content 5.3 %). On milling, crystalline hydrate of nateglinide has water content of about 2%.
Example 2 : X-ray data granules and tablet of crystalline hydrate of nateglinide
X-ray data were recorded on Powder diffractometer (Philips, Holland) using Cu KK source (^.=1.5406A°) with 45kV, 40 mA.. The detector used for XRD data acquisition was solid-state detector (X'celerator). XRD patterns were recorded using 0.02° step size and 2 sec time per step in range of 3° to 40°. Specimens were prepared on spinner sample holder by back filling technique. XRD scan of synthetic mixture of crystalline hydrate of compound of formula I and placebo, granules and tablet of crystalline hydrate of compound of formula I were recorded and compared with XRD scan of crystalline hydrate of compound of formula I. It was found that peak positions and peak heights were identical for synthetic mixture, granules and tablet with crystalline hydrate of nateglinide with no change in polymorphic form
Example 3 : DSC data of crystalline hydrate of nateglinide
DSC data was recorded on DSC 822 e ( Mettler Toledo) using the following conditions: Sample preparation : Seal 1-2 mg sample in 40 micro liter aluminum crucible. Temperature range : 35 -350° Heating range : 20° per min.
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Example 4 : Crystal Habit of crystalline hydrate of nateglinide
The aspect ratio was determined using the instrument NIKON, eclipse E400.
Crystalline hydrate of nateglinide with moisture content of 5.0% exhibited mean aspect ratio of 1.5.
Crystalline hydrate of nateglinide with moisture content of 12.5% exhibited mean aspect ratio of 5.2.
Particle size analysis of the crystalline hydrate is as follows:
Crystalline hydrate of nateglinide with moisture content of 5.0% exhibited VMD of 4.67 microns.
Crystalline hydrate of nateglinide with moisture content of 12.5% exhibited VMD of 8.78 microns.
Example 5 : Pharmaceutical composition
An oral formulation comprising compound of formula I was obtained as mentioned in Table 1 below.
Table 1

Ingredients Quantity (mg/tablet) Quantity (% w/w)
Compound of Formula I 120.0 17.44
Colloidal silicon dioxide 18.50 2.69
Mannitol SD 25 136.0 19.76
Corn starch (Purity 21-A) 210.0 30.52
Crospovidone 50.0 7.27
Polyvinylpyrrolidone (PVP K-30) 12.00 1.74
Sodium lauryl sulfate 6.00 0.87
Silicified microcrystalline cellulose (Prosolv SMCC HD 90) 101.0 14.68
Sodium bicarbonate 8.00 1.16
Magnesium stearate 6.50 0.94
Opadry yellow 20.00 Coated to a weight
gain of 3% by
weight
Compound of Formula I, mannitol and colloidal silicon dioxide were sifted through ASTM sieve #20 (ASTM stands for American Society for Testing and Materials) and mixed to obtain a blend. Corn starch, PVP, K-30 and crospovidone were sifted through ASTM sieve #40 and mixed to obtain another blend. The two blends thus obtained were mixed and granulated with an aqueous solution of sodium lauryl sulfate. The granules thus obtained were dried at 60°C to a moisture content of 4% and milled through 2mm sieve through a clit mill. The milled granules were lubricated with a mixture of presifted Prosolv SMCC, crospovidone, sodium bicarbonate, colloidal silicon dioxide and magnesium stearate. The lubricated mass was compressed and coated with an aqueous suspension of Opadry yellow to a target weight gain of 3% by weight of the tablet.
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The tablets were subjected to dissolution testing using 1000ml of pH 4.5 buffer in United States Pharmacopoeia dissolution apparatus, type n, at 37°C, at 75 rpm. The dissolution profile of the tablets was compared with that of Starlix® tablets and the results are recorded in Table 2 below.
Table 2

Time (mins) Percent drug released
Starlix tablets (120mg) Tablets of Example 4
5 66 39
10 76 52
15 81 60
30 88 74
60 95 85
Example 6 :
The bioavailability of the pharmaceutical composition of compound of formula I (Example 4) and that of marketed nateglinide formulation was studied. A single dose, open label, randomized, comparative, two-way crossover study was carried out for the same. Nateglinide® 120mg tablets (Novartis, USA, Lot No. 948H1462) were used as the reference standard.
The pharmacokinetic assessment was based on the plasma levels of nateglinide measured by blood sampling. Blood samples were obtained before dosing and at the following times after administration of both the reference and test medications - 1, 1.5, 1.75, 2, 2.25, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 8, 12, 16 and 24 hours.
Sixteen healthy male volunteers were enrolled for the study and all of them completed the two-way crossover study. A high fat, high calorie meal was given 0.5 hours before dosing. Drinking water was prohibited 2 hours before and after dosing. Subjects received a single tablet of nateglinide (120mg, Example 4) with 240ml of water at ambient temperature, as the test medication, while a single tablet of Starlix XR 120mg (Novartis) was administered as the reference medication. Standard meals were provided at 4, 8 and 12 hours after dosing. Meal plans were identical for both the periods. The plasma concentration of nateglinide was determined for samples collected at different time points and averaged over the sixteen volunteers. The data is given in Table 3 below.
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Table 3

Time (hrs) Plasma concentration (ng/ml) (Mean ± SD)

Tablet of Example 4 (120mg) Starlix® 120mg (Novartis)
0 1.14 2.17
1.0 877.313 1112.81
1.5 1099.25 1190.63
1.75 1027.75 1247.94
2.0 1050.938 1285.63
2.25 1153.313 1247.0
2.5 1137.375 1176.81
3.0 1080.375 895.81
3.5 915.375 844.69
4.0 788.188 772.81
4.5 892.5 751.94
5.0 655.688 527.81
5.5 438.25 363.06
6.0 287 266.4
8.0 111.913 84.84
12.0 34.881 28.87
16.0 10.003 8.82
24.0 0.815 1.64
The pharmacokinetic parameters calculated using the Win Nonlin software are given in Table 4 below.
Table 4
Ln-Transformed
Parameter Units Log transformed values Ratio
(%T/R) 90% confidence Intervals on the ratio

Reference
(Starlix® 120
mg) Test (nateglinide
tablet, 120 mg,
Example 4)
Lower Upper
c ng/ml 1654 1512 91.39 81.89 102.0
AUCo., ng.hr/ml 5329 5358 100.54 94.2 107.31
AUCo-i„f ng.hr/ml 5361 5382 100.39 94.1 107.10
While the invention has been described by reference to specific embodiments, this was done for purposes of illustration only and should not be construed to limit the spirit or the scope of the invention.
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We claim:
I. Crystalline hydrate of hypoglycemic agent, compound of formula I with water content of about 2 to about 7% by weight.

Formula I
2. Crystalline hydrate of hypoglycemic agent as claimed in claim 1, wherein the hydrate is monohydrate.
3. Crystalline hydrate of hypoglycemic agent as claimed in claim 1, characterized by fusion temperature of about 105°C when heated at a rate of 20°C/min under a nitrogen atmosphere in differential scanning calorimetric cell.
4. Crystalline hydrate of hypoglycemic agent as claimed in claim 1, characterized by mean aspect ratio equal to or less than about 2.
5. Crystalline hydrate of hypoglycemic agent as claimed in claim 1, characterized by a volume mean diameter less than about 5.0 microns.
6. A pharmaceutical composition comprising crystalline hydrate of hypoglycemic agent, compound of formula I, with water content of about 2 to about 7% by weight, and pharmaceutical^ acceptable excipients, wherein the composition has essentially the same bioavailability as nateglinide formulation whose New Drug Application received approval of United States Food and Drug Administration.
Dated this 17th day of November 2004
DILIP SHANGHVI CHAIRMAN AND MANAGING DIRECTOR SUN PHARMACEUTICAL INDUSTRIES LTD
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