ETORICOXIB AND POLYMORPHS THEREOF FIELD OF THE INVENTION

The invention relates to an improved process for the preparation of etoricoxib and polymorphs thereof. In particular, the invention relates to a process for the preparation of stable crystalline Form-I of etoricoxib. Further, the invention also relates to a process for the preparation of amorphous form of etoricoxib. The invention also relates to pharmaceutical compositions that include the stable crystalline Form-I of etoricoxib.

BACKGROUND AND THE PRIOR ART

The following discussion of the prior art is intended to present the invention in an appropriate technical context and allow its significance to be properly appreciated. Unless clearly indicated to the contrary, however, reference to any prior art in this specification should be construed as an admission that such art is widely known or forms part of common general knowledge in the field.

Etoricoxib is a selective COX-2 inhibitor which has been shown to be as effective as non-selective non-steroidal anti-inflammatory drugs in the management of chronic pain in rheumatoid arthritis, osteoarthritis and other COX-2 mediated disorders. Etoricoxib is -chloro-3-(4-methanesulfonylphenyI)-6' ^: methyl- [2,3 'jbipyridinyl having structural Formula (I).

(I)

Etoricoxib belongs to a class of drugs known as COX-2 inhibitors that are used in the treatment of COX-2 mediated disorders. The therapeutic application of etoricoxib as a COX-2 inhibitor is disclosed in International (PCT) Publication No. WO 96/10012 Al and WO 96/16934 Al . U.S. Patent No. 5,861,419 discloses a process for the preparation of etoricoxib. Polymorphism is the occurrence of different crystalline forms of a single compound and it is a property of some compounds and complexes. Thus, polymorphs are distinct solids sharing the same molecular Formula, yet each polymorph may have distinct physical properties. Therefore, a single compound may give rise to a variety of polymorphic forms where each form has different and distinct physical properties, such as different solubility profiles, different melting point temperatures and/or different x-ray diffraction peaks. Since the solubility of each polymorph may vary, identifying the existence of pharmaceutical polymorphs is essential for providing pharmaceuticals with predicable solubility profiles. It is desirable to investigate all solid-state forms of a drug, including all polymorphic forms, and to determine the stability, dissolution and flow properties of each polymorphic form. Polymorphic forms of a compound can be distinguished in a laboratory by X-ray diffraction spectroscopy and by other methods such as, infrared spectrometry. For a general review of polymorphs and the pharmaceutical applications of polymorphs See G. M. Wall, Pharm Manuf. 3, 33 (1986); J. K. Haleblian and W. McCrone, J. Pharm. Sci., 58, 91 1 (1969); and J. K. Haleblian, J. Pharm. Sci., 64, 1269 (1975), all of which are incorporated herein by reference.

International (PCT) Publication No. WO 2001/092230 A l (the WO '230 Al ) discloses different polymorphic forms of etoricoxib, specifically disclosed are Forms I, II, III, IV, V, hemihydrate and sesquihydrate as well as amorphous form characterized by X-ray powder diffraction d-spacings and differential scanning calorimetry (DSC).

The WO '230 Al discloses a process for the preparation of Form V by heating etoricoxib in isopropyl acetate at 55°C. The suspension was cooled at ambient temperature and the solids were isolated by filtration. The solids were washed with IPAC and dried in vacuum to give the Form V polymorph as a colorless solid.

International (PCT) Publication No. WO 2001 /037833 Al discloses polymorphic Form V of etoricoxib and process for its preparation. International (PCT) Publication No. WO 2002/096877 Al discloses a pharmaceutical composition comprising 1 -50% of polymorphic Form V of etoricoxib and remainder of the compound comprising at least one polymorph selected from Forms I, II, III and IV. The WO '833 application discloses a process for the preparation of crystalline Form-I of etoricoxib by recrystallizing Form II obtained using ethyl acetate or from a solvent mixture of isopropanol/hexane.

International (PCT) Publication No. WO 2005/085199 Al discloses different polymorphic forms of etoricoxib, viz. Forms IX, X, XI, XII, XIII, XIV, XV and XVI.

Organic process research & development 2003, (7) 958-961 discloses preparation of crystalline hemihydrate and anhydrous form of etoricoxib using isopropyl acetate and water combination. The hemihydrate and anhydrous forms of etoricoxib obtained by using isopropyl acetate/water are charaterised by X-ray powder diffraction (Figure. 2).

Journal of Organic Chemistry, 2000, 65(25), 8415-8420 dislcoses the preparation of etoricoxib by condensation of ketosulfone of Formula (IV) and CDPH compound (IIIA) in presence of potassium tert-butoxide as base.

International (PCT) Publication No. WO 2010/097802 discloses the preparation of etoricoxib by condensation of ketosulfone of Formula (IV) and CDPTH compound (III) is presence of potassium tert-butoxide as base.

The present invention provides processes for the preparation of etoricoxib and crystalline Form-I thereof, which is easily scalable and industrially applicable. The invention also provides an improved process for the preparation of etoricoxib which avoids the use of potassium tert-butoxide.

SUMMARY OF THE INVENTION:

In one general aspect there is provided a stable etoricoxib crystalline Form-I.

In another general aspect there is provided a stable etoricoxib crystalline Form-I having a particle size distribution dO. l < 5 μιη, d0.5 < 12 μιη and d0.9 < 50 μιτι.

In another general aspect there is provided a stable etoricoxib crystalline

Form-I substantially free from Form-V, characterized by having no peak at about 13.7 A by X-ray powder diffraction.

In another general aspect there is provided a stable etoricoxib crystalline Form-I substantially free from Form-IV, characterized by having no peak at about 8.7 A by X-ray powder diffraction. In another general aspect there is provided a stable etoricoxib crystalline Form-I substantially free from hemihydrate, characterized by having no peak at about 5.3 A by X-ray powder diffraction.

In another general aspect, there is provided an improved process for the preparation of etoricoxib of Formula (I).

the process includes:

(a) providing etoricoxib hydrochloride;

(b) hydrolyzing the etoricoxib hydrochloride with a suitable base;

(c) extracting the etoricoxib with one or more of first solvents;

(d) optionally removing the solvents; and

(e) obtaining the etoricoxib by treating with one or more of second solvents.

In another general aspect there is provided a process for the preparation of crystalline Form-I of etoricoxib of Formula (I).

the process includes:

(a) providing etoricoxib hydrochloride;

(b) hydrolyzing the etoricoxib hydrochloride with a suitable base;

(c) extracting the etoricoxib with one or more of first solvents;

(d) optionally removing the solvents;

(e) crystallizing the etoricoxib with one or more of second solvents; and

(f) obtaining the crystalline Form-I of etoricoxib. In another general aspect there is provide a process for the preparation of crystalline Form-I of etoricoxib of Formula (I).

the process includes:

(a) providing a solution of etoricoxib in one or more of suitable solvents;

(b) optionally removing the solvent to obtain a residue of etoricoxib; and

(c) obtaining the crystalline Form-I of etoricoxib by crystallizing in one or more of second solvents.

In another general aspect there is provide a process for the preparation of crystalline Form-I of etoricoxib of Formula (I).

the process includes:

(a) providing a solution of etoricoxib in one or more suitable solvents; and

(b) obtaining the crystalline Form-I of etoricoxib by addition of one or more suitable anti -sol vents.

; In another general aspect there is provide a process for the preparation of amorphous form of etoricoxib of Formula (I).

the process includes:

(a) providing a solution of etoricoxib in one or more suitable solvents; and

(b) obtaining the amorphous form of etoricoxib by addition of one or more suitable anti-solvents.

In another general aspect there is provided an improved process for the preparation of etoricoxib of Formula (I).

the process includes:

(a) reacting ketosulfone compoun

with a compound of Formula

wherein R ₂ through R ₅ are independently C] _-6 alkyl, aryl, aralkyl. R ₂ and R ₃ together as well as R4 and R ₅ together represents a cyclic group, optionally containing one or more heteroatom selected from N, O or S,

in the presence of sodium hydride in one or more suitable solvents to obtain etoricoxib; and

(b) obtaining the etoricoxib of Formula (I). In another general aspect there is provided a pharmaceutical composition comprising a therapeutically effective amount of stable crystalline Form-I of etoricoxib having a particle size d0.9 < 50 μπι.

In another general aspect there is provided storage stable crystalline Form-I of etoricoxib.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

FIG 1. shows the X-ray diffractogram (XRD) of Etoricoxib crystalline Form-I prepared by the process of present invention.

FIG 2. shows the differential scanning calorimetry (DSC) of Etoricoxib crystalline Form-I prepared by the process of present invention.

FIG 3. shows the X-ray diffractogram (XRD) of Etoricoxib amorphous form prepared by the process of present invention.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the term "stable" refers to crystalline etoricoxib Form-I that includes either of the following:

a) crystalline Form-I does not convert to Form-V or hydrates or other known crystalline forms, when stored at a temperature of up to about 40°C and a relative humidity of up to about 75% for atleast 6 months, or

b) crystalline Form-I does not convert to Form-V or hydrates or other known crystalline forms when stored at a temperature of up to about 25°C and a relative humidity of up to about 60% for atleast 6 months.

The stable crystalline Form-I does not show an X-ray powder diffraction peak at a diffraction angle (2Θ) of about 8.7 A for Form-IV or 13.7 A for Form-V or 5.3 A for hemihydrate, when stored at a temperature of up to about 40°C and a relative humidity of up to about 75% for atleast 6 months.

The stable crystalline Form-I does not show an X-ray powder diffraction peak at a diffraction angle (2Θ) of about 8.7 A for Form-IV or 13.7 A for Form-V or 5.3 A for hemihydrate, when stored at a temperature of up to about 25°C and a relative humidity of up to about 60%) for atleast 6 months.

The term "substantially free" herein means, the crystalline Form-I of etoricoxib that contains crystalline Form-V, Form-IV or hemihydrate less than about 1.0%, particularly less than 0.5%, more particularly not in detectable amount when measured by x-ray powder diffraction with respect to its corresponding peaks.

The other known forms as herein above means, crystalline forms selected from Form-II, Form-Ill, Form-IV, Form-V, hemihydrate or sesquihydrate or amorphous form as characterized in European Patent No. EP 1296951 B l, which is incorporated herein as reference in its entirety.

As used here in the term "obtain" or "obtaining" may include decantation or unloading from hydrogenator or pressure reactor. The product obtained may be further or additionally dried to achieve the desired moisture values and remove traces of solvents atleast under ICH limits. For example, the product may be dried in a tray drier, dried under vacuum and/or in a Fluid Bed Drier.

As used here in the term "about" may include the values from ±0.2° in case of 2-theta for diffractogram values. The term "about" may also include the values from ±3°C in case of differential scanning calorimetry.

The present invention can comprise (open ended) or consist essentially of the components of the present invention as well as other ingredients or elements described herein. As used herein, "comprises" means the elements recited, or their equivalent in structure or function, plus any other element or elements which are not recited. The terms "having" and "including" are also to be construed as open ended unless the context suggest otherwise.

All ranges recited herein include the endpoints, including those that recite a range "between" two values. Terms such as "about", "general", "substantially," and the like are to be construed as modifying a term or value such that it is not an absolute. Such terms will be defined by the circumstances and the terms that they modify as those terms are understood by those skill in the art. This includes, at very least, the degree of expected experimental error, technique error and instrument error for a given technique used to measure a value.

When a molecule or other material is identified herein as "pure", it generally means, unless specified otherwise, that the material is about 99% pure or more. In general, this refers to purity with regard to unwanted residual solvents, reaction byproducts, impurities and unreacted starting materials. In the case substantially pure etoricoxib, "pure" also means about 99% of more of crystalline Form-I free from other known crystalline forms as appropriate or in the case of crystalline solids.

The inventors have found an improved process for the preparation of etoricoxib of Formula (I) and, in particular, the crystalline Form-I of etoricoxib and amorphous form of etoricoxib.

The crystalline Form-I of etoricoxib is characterized by its X-ray powder diffraction pattern and differential scanning calorimetry thermogram as shown in Figures 1 and 2, respectively. The amorphous form of etoricoxib is characterized by its X-ray powder diffraction pattern as shown in Figure 3.

The inventors also have developed a process for the preparation of crystalline Form-I of etoricoxib by providing solution of etoricoxib in one or more of suitable solvent and obtaining crystalline Form-I of etoricoxib by removal of solvent. The inventors have also developed a process for the preparation of amorphous form of etoricoxib by providing the solution of etoricoxib in one or more of suitable solvent and obtaining amorphous of etoricoxib by addition of one or more of suitable anti- solvent.

In general, the removal of solvent may be done by a technique which includes, for example, filtration, filtration under vacuum, decantation, centrifugation, distillation and distillation under vacuum.

The product obtained may be further or additionally dried to achieve the desired moisture values. For example, the product may be dried in a hot air oven, tray drier, dried under vacuum and/or in a Fluid Bed Drier.

The prior art references like U.S. Patent No. 5,861 ,419 and our own International (PCT) publication WO 2010/097802 A2 are incorporated herein by reference in their entirety wherein the process for the preparation of intermediates and etoricoxib is disclosed.

In one general aspect, there is provided stable etoricoxib crystalline Form-I.

In another general aspect, there is provided a stable etoricoxib crystalline Form-I having particle size distribution dO. l < 5 μηι, d0.5 < 12 μπι and d0.9 < 50 μιη. In particular, the particle size distribution is dO. l < 3 μιη, d0.5 < 10 μιτι and d0.9 < 35 μιη, when measured by Malvern particle size analyzer. In general, the particle size distribution may be achieved by the process of the present invention or alternatively by any one of the known methods reported in the art like micronization, milling, grinding and sieving etc. which may reduce the particle.

In another general aspect, there is provided a stable etoricoxib crystalline Form-I substantially free from Form-V, characterized by having no peak at about 13.7 A by X-ray powder diffraction.

In another general aspect, there is provided a stable etoricoxib crystalline Form-I substantially free from Form-IV, characterized by having no peak at about 8.7 A by X-ray powder diffraction.

In another general aspect, there is provided a stable etoricoxib crystalline Form-I substantially free from hemihydrate, characterized by having no peak at about 5.3 A by X-ray powder diffraction.

In another general aspect, the stable crystalline Form-1 of etoricoxib may be characterized by atleast 6 months stability results as outline in Table-1 which is representative for one of the batch.

Table !

^a NLT = Not less than

bNMT = Not more than

In another general aspect, there is provided an improved process for preparation of etoricoxib of Formula (I),

the process comprises:

(a) providing etoricoxib hydrochloride;

(b) hydrolysing the etoricoxib hydrochloride with suitable base;

(c) extracting etoricoxib with one or more of first solvent;

(d) optionally, removing the solvent; and

(e) obtaining etoricoxib by treating with one or more of second solvent.

In general the etoricoxib hydrochloride may be prepared by the process as disclosed in prior art reference WO 2010/097802 A2 for the preparation of etoricoxib and converting etoricoxib thus obtained to hydrochloride by treating with a hydrochloride source. The WO '802 A2 is incorporated herein as reference in its entirety.

In general, the etoricoxib hydrochloride may be hydrolyzed with suitable base comprises of alkali or alkaline earth metal hydroxide, alkali or alkaline earth metal carbonate or bicarbonates , hydrides, ammonia and the like. In particular, the suitable base comprises one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, cesium hydroxide, magnesium hydroxide and the like, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium hydride, potassium tert-butoxide, ammonia and the like. In particular, sodium hydroxide may be used.

Embodiments of the process include, hydrolysis of etoricoxib hydrochloride in presence of sodium hydroxide in water at about 25°C. The reaction proceeds further by extraction of etoricoxib obtain in-situ after hydrolysis in one or more of first solvent. The first solvent comprises one or more of toluene, xylene, ethylbenzene, chlorobenzene, n-heptane, n-hexane, ethyl acetate, isopropyl acetate, n-butyl acetate, t-butyl acetate, methylene dichloride, ethylene dichloride and the like. In particular, the first solvent may be methylene dichloride.

In general, the process parameters include washing methylene. dichloride layer with water and separating the layer before removal of methylene dichloride. The solvent was distilled below 50°C upto half the volume followed by addition of one or more of second solvent. The second solvent comprises one or more of methanol, ethanol, isopropanol, n-butanol, hexanol, heptanol, dodecanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, isobutyl acetate, isopropyl acetate, n- butyl acetate, dimethyl formamide, dimethyl acetamide, dimethyl sulfoxide, sulfolane, acetonitrile, N-methyl pyrrolidone and the like. In particular, isopropyl acetate was used.

Embodiments of the process further includes, addition of isopropyl acetate to half volume methylene dichloride containing etoricoxib and heating the reaction mixture at about 40°C to 90°C. In particular, the reaction mixture was heated from about 45°C to about 55°C to obtain the suspension. The reaction mixture may be cooled prior to obtaining of etoricoxib. The cooling may be particularly done to about 0°C to about 10°C to obtain etoricoxib. The process may further include drying etoricoxib followed by milling with suitable mesh size to obtain uniform particle size.

In another general aspect, there is provided a process for the preparation of crystalline Form-I of etoricoxib of Formula (I),

the process comprises:

(a) providing etoricoxib hydrochloride;

(b) hydrolysing the etoricoxib hydrochloride with suitable base;

(c) extracting etoricoxib with one or more of first solvent;

(d) optionally, removing the solvent;

(e) crystallizing etoricoxib with one or more of second solvent; and (g) obtaining crystalline Form-I of etoricoxib.

In general, the crystallization of etoricoxib may be performed in one or more of second solvent comprises of methanol, ethanol, isopropanol, n-butanol, hexanol, heptanol, dodecanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, isobutyl acetate, isopropyl acetate, n-butyl acetate, dimethyl formamide, dimethyl acetamide, dimethyl sulfoxide, sulfolane, acetonitrile, N-methyl pyrrolidone and the like. In particular, isopropyl acetate was used.

Embodiments of the process may further include heating the suspension of etoricoxib in isopropyl acetate at about 40°C to about 90°C, particular at about 55°C to obtain crystalline etoricoxib. The process parameters may further include drying of crystalline etoricoxib obtained from isopropyl acetate at higher temperature. Particular, crystalline etoricoxib may be dried at about 70°C to 75°C for 1-10 hours to obtain crystalline Form-I of etoricoxib.

In another general aspect, there is provide a process for the preparation of crystalline Form-I of etoricoxib of Formula (I),

the process comprises:

(a) providing the solution of etoricoxib in one or more of suitable solvent;

(b) optionally, removing the solvent to obtain the residue of etoricoxib; and

(c) obtaining crystalline Form-I of etoricoxib by crystallizing the residue in one or more of second solvent.

In general, the solution of etoricoxib may be obtained by dissolving etoricoxib in one or more of suitable solvent comprises one or more of toluene, xylene, ethylbenzene, chlorobenzene, n-heptane, n-hexane, ethyl acetate, isopropyl acetate, n- butyl acetate, t-butyl acetate, methylene dichloride, ethylene dichloride. In particular, the solvent may be methylene dichloride.

Embodiments of the process may include optionally removing the solvent for obtaining residue of etoricoxib. The solvent may be removed for example, one or more of filtration, filtration under vacuum, decantation, centrifugation, distillation, distillation under vacuum and the like.

In general, the process parameters may include treating the residue with one or more of suitable second solvent to obtain the suspension. The second solvent comprise of one or more of methanol, ethanol, isopropanol, n-butanol, hexanol, heptanol, dodecanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, isobutyl acetate, isopropyl acetate, n-butyl acetate, dimethyl formamide, dimethyl acetamide, dimethyl sulfoxide, sulfolane, acetonitrile, N-methyl pyrrolidone and the like. In particular, isopropyl acetate may be used.

Embodiments of the process may further include heating the suspension of etoricoxib in isopropyl acetate at about 40°C to about 90°C, particular at about 55°C to obtain crystalline etoricoxib. The process parameters may further include drying of crystalline etoricoxib obtained from isopropyl acetate at higher temperature. Particular, crystalline etoricoxib may be dried at about 70°C to 75°C for 1 -10 hours to obtain crystalline Form-I of etoricoxib.

In general, the crystalline Form-I of etoricoxib may be characterized by its X- ray powder diffraction pattern having characteristic peaks at about 6.9°, 9.5°, 1 1.6°, 12.2°, 12.9°, 15.3°, 16.4°, 17.8°, 19.0°, 19.2°, 20.1°, 21.0°, 21 .7°, 22.6°, 23.1°, 23.5°, 23.9°, 26.2°, 28.3° degrees 2-theta. Further, etoricoxib may be characterized by differential scanning calorimetry having endothermic peak at about 139°C.

In another general aspect, there is provide a process for the preparation of crystalline Form-I of etoricoxib of Formula (I),

the process comprising:

(a) providing the solution of etoricoxib in one or more of suitable solvent; and

(b) obtaining crystalline Form-I of etoricoxib by addition of one or more of suitable anti-solvent. In general, the solution of etoricoxib may be obtained by dissolving etoricoxib in one or more of suitable solvent comprises of toluene, xylene, ethylbenzene, chlorobenzene, n-heptane, n-hexane, ethyl acetate, isopropyl acetate, n-butyl acetate, t-butyl acetate, methylene dichloride, chloroform, ethylene dichloride. In particular, the solvent may be methylene dichloride or chloroform.

The solution of etoricoxib in one or more of suitable solvent may be treated with one or more of suitable anti-solvent comprises of cyclohexane, n-hexane, n- heptane, diethyl ether, diisopropyl ether, methyl tert-butyl ether, ethyl acetate, n-butyl acetate, isopropyl acetate, n-butyl acetate and the like. In particular, n-heptane or n- hexane may be used.

In another general aspect, there is provide a process for the preparation of amorphous form of etoricoxib of Formula (I),

the process comprising:

(a) providing the solution of etoricoxib in one or more of suitable solvent; and

(b) obtaining amorphous form of etoricoxib by addition of one or more of suitable anti-solvent.

In general, the solution of etoricoxib may be prepared by dissolving etoricoxib of Formula (I) in one or more of suitable solvent comprises of methanol, ethanol, isopropanol, n-butanol, hexanol, heptanol, dodecanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, isobutyl acetate, isopropyl acetate, n-butyl acetate, dimethyl formamide, dimethyl acetamide, dimethyl sulfoxide, sulfolane, acetonitrile, N-methyl pyrrolidone and the like. In .particular, methanol, ethanol, isopropanol, acetone may be used.

The solution of etoricoxib in one or more of suitable solvent may be treated with one or more of suitable anti-solvent comprises of cyclohexane, n-hexane, n- heptane, diethyl ether, diisopropyl ether, methyl tert-butyl ether, ethyl acetate, n-butyl acetate, isopropyl acetate, n-butyl acetate and the like. In particular, n-heptane or n- hexane may be used.

The amorphous form of etoricoxib may be characterized by X-ray powder diffraction pattern as shown in FIG.3.

In another general aspect, etoricoxib can be prepared by the reaction scheme- 1 as shown below, which is also the scope of the present invention.

Scheme-1

In another general aspect, etoricoxib can be prepared by the reaction scheme-2 as shown below, which is also the scope of the present invention.

lll-AB (I)

Scheme-2

In another general aspect, there, is provided an improved process for the preparation of etoricoxib of Formula (I),

the process comprises:

(a) reacting ketosulfone compound of Formula (IV)

)

wherein R ₂ through R5 are independently Ci _-6 alkyl, aryl, aralkyl. R ₂ and R ₃ together as well as R ₄ and R5 together represents a cyclic group, optionally containing one or more heteroatom selected from N, O or S,

in presence of sodium hydride in one or more of suitable solvent to obtain etoricoxib; and

(b) obtaining etoricoxib of Formula (I).

In general, the compound of Formula (III-AB) may be selected from and not limited to the compounds of Formula (III-A) or (III-B) as herein below.

In general, the suitable solvent comprises one or more of hydrocarbons like benzene, toluene, xylene, ethyl benzene and the like, halogenated hydrocarbon like chloroform, methylene dichloride, ethylene dichloride and the like, alcohols like methanol, ethanol, isopropanol, t-butanol and the like, ketones like acetone, methyl ethyl ketone, methyl isobutyl ketone, and the like, aprotic polar solvents like dimethyl formamide, dimethyl acetamide, N-methyl pyrrolidone, dimethylsulfoxide and the like, ethers like diethyl ether, 1 ,4-dioxane, diisopropyl ether, methyl tert-butyl ether, tetrahydrofuran and the like, nitriles like acetonitrile and the like or mixture thereof. In particular, the mixture of dimethyl formamide and toluene may be used.

The isolation of etoricoxib may be done with the process disclosed in WO

2010/097802 A2 which is incorporated herein as reference in its entirety.

Powder X-ray diffraction of etoricoxib forms can be obtained under following conditions.

(i) Characterization by Powder X-ray diffraction

The X-ray powder diffraction spectrum was measured under the following experimental conditions:

Instrument : X-Ray Diffractometer, D/Max-2200/PC Make: Rigaku,

Japan.

X- Ray : Cu/40kv/40mA

Diverging : 10

Scattering Slit : 10

Receiving Slit : 0.15 mm

Monochromator RS : 0.8 mm

Counter : Scintillation Counter

Scan Mode : Continuous

Scan Speed : 3.0000 / Min

Sampling Width : 0.020

Scan Axes : Two Theta / Theta

Scan Range : 2.0000 to 40.0000

Theta Offset : 0.0000 The crystalline Form-I of Etoricoxib shows DSC peak melting temperature of 139°C and x-ray powder diffraction peaks at about degrees 2-theta and d-spacing : Table-II

Table-II

In another general aspect, the present invention accordingly provides a pharmaceutical composition comprising a therapeutically effective amount of crystalline Form-I of etoricoxib and one or more pharmaceutically acceptable carriers, excipients or diluents. In another general aspect, there is provided a pharmaceutical composition comprising a therapeutically effective amount of stable crystalline Form-I of etoricoxib having particle size d0.9 < 50 μιη.

In another general aspect, there is provided a pharmaceutical composition comprising a therapeutically effective amount of stable crystalline Form-I of etoricoxib having particle size distribution dO. l < 5 μπι, d0.5 < 12 μιη and d0.9 < 50 , μιη.

In another general aspect, the present invention accordingly provides a pharmaceutical composition comprising a therapeutically effective amount of amorphous form of etoricoxib and one or more pharmaceutically acceptable carriers, excipients or diluents.

In another general aspect, there is provided a storage stable crystalline Form-I of etoricoxib.

In particular, the storage stable crystalline Form-I of etoricoxib does not show any change in the XRD pattern after storage for three months at 40°C and 75% relative humidity or at 25°C and 60% relative humidity. More particularly, the storage . stable crystalline Form-I of etoricoxib has no detectable quantities of polymorphic

Form-IV or Form-V or a hemihydrate after storage for three months at 40°C and 75% relative humidity or at 25°C and 60% relative humidity.

The present invention is further illustrated by the following examples which are provided merely to be exemplary of the invention and do not limit the scope of the invention. Certain modification and equivalents will be apparent to those skilled in the art and are intended to be included within the scope of the present invention.

EXAMPLES

Example 1: Preparation of etoricoxib hydrochloride:

Potassium tertiary butoxide (0.456 Kg), l-(6-methylpyridin-3-yl)-2[4- (methylsulfonyl)- phenyl]ethanone (1.0 Kg) and 2-chloro-l,3-(bis morpholinyl) trimethinium hexafluoro phosphate of (Formula III) (1.612 Kg) were dissolved in THF (10.0 L) and the solution was heated at 30-55°C for 2-24 hrs. The reaction mixture was treated with acetic acid (1.45 Kg) and basified with ammonia gas (1.2 Kg) followed by the addition of ammonium acetate (0.277 Kg). The solvent was removed by distillation under vacuum to obtain a residue. The residue was treated with toluene and water mixture followed by the removal of toluene. The residue was crystallized in isopropanol to obtain etoricoxib. The etoricoxib thus obtained was converted to its hydrochloride by treating with methanolic HCl. The etoricoxib hydrochloride was recrystallized in methanol to obtain pure etoricoxib hydrochloride. HPLC purity > 99.0%.

Example 2; Preparation of etoricoxib hydrochloride:

Sodium hydride (15 g) and l-(6-methylpyridin-3-yl)-2[4-(methylsulfonyl)- phenyl]ethanone (100 g) were taken in dimethylformamide (200 mL) at 10°C. Toluene (500 mL) and compound of (Formula ΠΙ-Α) ( 1 12.32 g) were added to the reaction mixture and stirred for 3 hours at 10°C. The reaction mixture was treated with acetic acid (145.3 g) and basified with ammonia gas (277 g) followed by the addition of ammonium acetate (28.5 g). The solvent was removed by distillation under vacuum to obtain a residue. The reaction mixture was heated at 60°C for 6 hours and cooled to 40°C. Formaldehyde (21.6 g) was added and the reaction mixture was heated at 60°C for 1 hour. The separated aqueous layer was treated with tetrahydrofuran (5 mL) and toluene (300 mL) and solvents were removed to obtain a residue. The residue was treated with toluene and water mixture followed by the removal of toluene. The residue was crystallized in isopropanol to obtain etoricoxib in the presence of seed crystals of Form-I.

The etoricoxib thus obtained was converted to its hydrochloride by treating with methanolic HCl. The etoricoxib hydrochloride was recrystallized in methanol to obtain pure etoricoxib hydrochloride. HPLC purity > 99.0%.

The above example was repeated by replacing compound (III-A) with (III-B) to obtain etoricoxib Form-I or its hydrochloride salt.

Example 3; Preparation of crystalline Form-I etoricoxib:

To a stirred solution of sodium hydroxide (20.20 g) in water (250 mL), etoricoxib hydrochloride (50 g) was added at a temperature of 25°C to 35°C. The reaction mixture was stirred and extracted with methylene dichloride (250 mL). The separated organic layer was filtered through a hyflow bed and distilled out to give a residue. Isopropyl acetate (100 mL) was added to the residue and heated at 50-55°C. The reaction mixture was cooled to 0-10°C and solid was filtered. The solid was dried to obtain the crystalline Form-I of etoricoxib. Example 4: Preparation of crystalline Form-I of etoricoxib:

Etoricoxib (100 g) was dissolved in methylene dichloride (500 mL) followed by the addition of sodium chloride solution (45 gm in 300 ml). The reaction mixture was stirred to separate the organic layer. The separated organic layer was dried over anhydrous magnesium sulfate (15 g). The organic layer was filtered through a hyflow bed and methylene dichloride was distilled out to obtain a residue. Isopropyl acetate

(200 mL) was added to the residue and heated at 50 C. The reaction mixture was cooled and solid was filtered. The solid was dried to obtain the crystalline Form-I of etoricoxib. The Form-I of etoricoxib was characterized by XRPD (Fig.l) and DSC (Fig.2).

Example 5; Preparation of crystalline Form-I of etoricoxib:

Etoricoxib (5 g) was dissolved in chloroform (15 mL) by stirring at 25°C to get a clear solution. The clear solution was treated with n-hexane (100 mL) at- 25°C.

The reaction mixture was cooled to 5°C and the product obtained was filtered and washed with hexane. The product was dried in hot air oven at 60°-65°C to obtain 4 g crystalline Form-I of etoricoxib characterized by XRPD (Fig. l ) and DSC (Fig.2).

Example 6: Preparation of amorphous form of etoricoxib:

Etoricoxib (5 g) was dissolved in methanol (40 mL) by stirring at 25°C to get a clear solution. The clear solution was treated with n-hexane (200 mL) at 25°C. The reaction mixture was cooled to 5°C and the product obtained was filtered and washed with hexane. The product was dried in hot air oven at 60°C to obtain 3 g amorphous form of etoricoxib characterized by XRPD (Fig.3).

While the present invention has been described in terms of its specific embodiments, certain modifications and equivalents will be apparent to those skilled in the art and are intended to be included within the scope of the present invention.