WO2012066565A2

WO2012066565A2 - Asenapine maleate amorphous and crystalline form and process for preparation thereof

Info

Publication number: WO2012066565A2
Application number: PCT/IN2011/000783
Authority: WO
Inventors: Shriprakash Dhar Dwivedi; Ashok Prasad; Piyush Rajendra Sharma
Original assignee: Cadila Healthcare Limited
Priority date: 2010-11-16
Filing date: 2011-11-11
Publication date: 2012-05-24
Also published as: WO2012066565A3

Abstract

The present invention discloses substantially pure monoclinic form of asenapine maleate having d95 particle size of less than about 100 microns.

Description

ASENAPINE MALEATE AMORPHOUS AND CRYSTALLINE FORM AND PROCESS FOR PREPARATION THEREOF FIELD OF THE INVENTION

The invention encompasses monoclinic form of asenapine maleate having particle size in terms of d95 is less than about 100 microns. The present invention provides microcrystalline monoclinic form of asenapine maleate having particle size in terms of d95 is less than about 10 microns and process for preparing and pharmaceutical composition of it. The present invention also relates to amorphous asenapine maleate, process for preparing it and pharmaceutical composition thereof. BACKGROUND OF THE INVENTION

Asenapine Maleate, which is the generic name for the compound of formula (I), trans-5-chloro-2-methyl-2,3,3a, 12b-tetrahydro- l H-dibenz[2,3:6,7] oxepine[4,5- cjpyrrole Maleic acid salt, is an antipsychotic drug used for treatment for schizo hrenia.

(I)

U.S Patent No. 4, 145,434 discloses asenapine and its process for preparation. Asenapine is developed as Maleate salt.

U.S Patent No. 7,73 1 ,458 discloses crystalline asenapine maleate salt in the orthorhombic form. It also discloses process for preparation of crystall ine asenapine maleate in monoclinic form.

PCT publication no. 95/23600 A l discloses pharmaceutical composition for sublingual or buccal administration of asenapine maleate. *

US patent application Pub. No. 20080090892 Al discloses asenapine and pharmaceutically acceptable salts, solvates, and hydrates thereof, wherein the compound is at least 50% amorphous based on total weight of the compound.

One of the most important physical properties of a pharmaceutical compound, which can form polymorphs, is its solubility in aqueous solution, particularly the solubility in gastric juices of a patient. Other important properties relate to the ease of processing the form into pharmaceutical dosages, as the tendency of a powdered or granulated form to flow and the surface properties that determine whether crystals of the form will adhere to each other when compacted into a tablet.

The discovery of stable polymorphic form of a pharmaceutically useful compound provides a new opportunity to improve the performance characteristics of a pharmaceutical product. It enlarges the repertoire of materials that a formulation scientist has available for designing, for example, a pharmaceutical dosage form of a drug with a targeted release profile or other desired characteristic.

SUMMARY OF THE INVENTION

An aspect of the present invention is to provide substantially pure monoclinic form of asenapine maleate and process for preparation thereof.

Another general aspect of the present invention is to provide substantially pure monoclinic form of asenapine maleate having d95 particle size of less than about 100 microns.

Another general aspect of the present invention provides process for preparing substantially pure monoclinic form of asenapine maleate having d95 particle size of less than about 100 microns.

The present invention provides a process for controlling the particle size of substantially pure monoclinic form having d95 particle size of less than about 100 microns.

An another aspect of the present invention is to provide substantially pure microcrystalline monoclinic form of asenapine maleate having d95 particle size of less than about 10 microns

In another general aspect, the process for preparing substantially pure microcrystalline monoclinic form of asenapine maleate comprising the steps of;

a) milling asenapine maleate to obtain particle size in terms of d95 less than about 10 microns

b) slurrying micronized asenapine maleate in one or more organic solvents to form a solution; and

c) isolating substantially pure microcrystalline monoclinic form of asenapine maleate.

Another aspect of the present invention also relates to amorphous form of Asenapine Maleate and process for preparation thereof. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a characteristic powder X-ray powder diffraction (XRPD) pattern of amorphous Asenapine Maleate.

FIG. 2 is the characteristic particle size distribution (PSD) of substantially pure monoclinic form of Asenapine Maleate wherein d95 is less than about 30 microns obtained by sieving through 200 mesh.

FIG. 3 is the characteristic particle size distribution (PSD) of substantially pure monoclinic form of Asenapine Maleate wherein d95 is less than about 10 microns obtained by micronization after sieving of 200 mesh.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides substantially pure monoclinic form of Asenapine Maleate of formula (I)

The term 'substantially pure' used herein is with respect to 'polymorphic purity^' of the crystalline monoclinic form of asenapine maleate.

The 'substantially pure' monoclinic form of asenapine maleate is having polymorphic purity of at least 99.99% of monoclinic form or which contains preferably less than about 1 % of orthorhombic form, more preferably 0.05% of orthorhombic form and most preferably no detectable amount of orthorhombic form of asenapine maleate or free from orthorhombic form of asenapine maleate.

In one general aspect, there is provided a process for preparing substantially pure monoclinic form of asenapine maleate comprising the steps of:

a) slurrying asenapine maleate in one or more of suitable organic solvent to form a solution; and

b) isolating substantially pure microcrystalline monoclinic form of asenapine maleate.

In general, the slurry of asenapine maleate may be obtained by dissolving asenapine maleate in one or more suitable organic solvents comprises of C_3-6 ketones or a mixture thereof with water, N-methylpyrrolidone, C_3-6 amides, halo-substituted C₆-i2 aromatic hydrocarbons propylene glycol, dimethyl sulfoxide, dimethyl carbonate, CM alkyl alcohols, a mixture of a C|.g alkyl alcohol and water, acetonitrile or a mixture thereof with water, C₂.₆ alkyl acetates or their mixture with water, cellosolve, dimethyl carbonate, polyethylene glycol methyl ether and C₂-s ethers.

In general, the asenapine maleate used as the starting material may be monoclinic form of having polymorphic purity of 99% to 99.5%.

The embodiments of the process may include heating the slurry of the step (i) to obtain reaction mass followed by cooling. The reaction mass may be heated upto temperature of 40 to 60°C and the cooling at about 5°C to 10°C. The reaction mass may be stirred for 30 minutes to 2 hours.

The substantially pure monoclinic form of asenapine maleate may be isolated by filtration, or removal of solvent under vaccum, drying under vaccum or any other techniques known in the art.

The particle size of the drug substance influences biopharmaceutical properties of the drug product. For example, the particle size of the drug substance affects drug product manufacturing and dissolution and hence its bioavailability.

Since asenapine dissolves in the saliva the particle size is important. When drug substance particles are small, it takes only short periods of time to achieve high concentrations. From this perspective small particles are preferred. In addition, smaller particle size tends to improve the homogeneity of powder blends, which may result in improved uniformity of the contents of the drug product.

For asenapine maleate, the particle size, in terms of d95, is particularly less than about 100 microns, more particularly less than about 50 microns and most particularly less than about 30 microns. As used throughout the disclosure, the term d95 means that 95% of the particles (based on volume) are smaller than or equal to the indicated size.

In another general aspect, the present invention provides substantially pure monoclinic form of asenapine maleate that is microcrystalline. The term "microcrystalline" means that the form comprises particles having a size distribution characterized by a d95 of less than 10 microns, particularly less than 7 microns.

In another general aspect, the invention provides a process for controlling the particle size of substantially pure monoclinic form of asenapine maleate,

the process comprising:

a) sieving asenapine maleate having D95 particle size of about 250 microns;

b) isolating asenapine maleate having D95 particle size of less than about 30 microns; c) milling asenapine maleate obtained in step (b); and d) isolating substantially pure monoclinic form of asenapine maleate particles having D95 particle size of less than about 10 microns.

In general, the sieving of asenapine maleate in step (a) is performed through 200 mesh.

The sieving of asenapine maleate in step (a) through 200 mesh results in substantially pure monoclinic form of asenapine maleate having D95 particle size of less than about 30 microns in single stroke.

After sieving step the micronization step (c) is performed to further reduce the particle size to microcrystalline asenapine maleate comprises of jet milling performed with feeding pressure of about 3 kg and grinding pressure of about 4 kg.

The jet milling cycle may vary from 1 to 5 cycles to obtain (D95) less than about 10 microns. During the step of micronization there is possibility of conversion of asenapine maleate monoclinic form into orthorhombic form. To overcome this possibility the present invention provides a process for obtaining substantially pure microcrystalline monoclinic form of asenapine maleate.

In another general aspect, the invention provides a process for preparing substantially pure microcrystalline monoclinic form of asenapine maleate comprising the steps of;

a) milling asenapine maleate to obtain D95 particle size of less than about 10 microns; and

b) slurrying the micronized asenapine maleate in one or more of suitable organic solvents to form a solution; and

The miling in step (a) is performed to reduce the particle size to microcrystalline level and to achieve microcrystalline Asenapine Maleate. The milling step is performed with feeding pressure of about 3 kg and grinding pressure of about 4 kg.

The milling cycles may vary from 1 to 5 cycles to obtain (D95) less than about 10 microns. The slurry of micronized asenapine maleate may be obtained by dissolving asenapine maleate in one or more suitable organic solvents.

The micronized asenapine maleate when used as the starting material may be monoclinic form of asenapine maleate having polymorphic purity of 99% to 99.5%.

The solvent for step (a) for preparing slurry of microcrystalline asenapine maleate comprises one or more of C3.6 ketones or a mixture thereof with water, N- methylpyrrolidone, amides, halo-substituted C6-i₂ aromatic hydrocarbons propylene glycol, dimethyl sulfoxide, dimethyl carbonate, C alkyl alcohols, a mixture of a Ci_-8 alkyl alcohol and water, acetonitriie or a mixture thereof with water, C2-6 alkyl acetates or their mixture with water, cellosolve, dimethyl carbonate, polyethylene glycol methyl ether and C2-8 ethers.

In general, the slurry as in step (a) may be prepared by heating to obtain the reaction mass followed by cooling. The reaction mass may be heated upto temperature of 40 to 60°C and the cooling temperature may be 5 to 10°C. The reaction mass may be stirred for 30 to 60 minutes.

The isolation of substantially pure microcrystalline morioclinic form of asenapine maleate may involve filtration, removal of solvent under vaccum, drying under vaccum or any other techniques known in the art.

In another general aspect, the invention provides a process for preparing microcrystalline monoclinic form of asenapine maleate having (D95) less than about 10 microns, the process comprises

a) treating asenapine with maleic acid in a solvent to obtain the solution;

b) obtaining asenapine maleate having (D95) particle size of about 250 microns;

c) sieving asenapine maleate obtained in step (b);

d) isolating asenapine maleate with (D95) particle size less than about 30 microns; e) milling asenapine maleate obtained in step (d); and

isolating microcrystalline monoclinic form of Asenapine Maleate having (D95) less than about 10 microns.

The reaction is preferably carried out in suitable solvent. The solvent system is preferably selected so as to facilitate the salt reaction and to allow subsequent separation of the resulting acid addition salt. Advantageously, both Asenapine and the reactant acid are dissolvable, at least partly, in the solvent system, at least at elevated temperatures. In the process, a mixture, slurry, or solution of Asenapine and a solvent may be contacted with a reactant acid, or conversely, a mixture, slurry, or solution of reactant acid and a solvent may be contacted with Asenapine. In another embodiment, both partners may be combined with a solvent system prior to being contacted together, whereby the solvent system used for reactant acid may be identical with or different from the solvent system used for the asenapine. The solvent system can be comprised of a single solvent or a mixture of solvents. When two or more solvents are used, a two phase reaction scheme may be used wherein the asenapine and reactant acid are primarily reacted in one phase and the resulting asenapine salt of formula (II) compound is primarily present in the other phase due to, inter alia, solubility differences, etc.

The temperature of contact of asenapine and reactant acid in the solvent system is from ambient to the boiling point of the solvent system, with elevated temperatures, but generally less than the boiling point, being preferred. It is not required that a complete solution is formed in this step, i.e. slurry or two-phase solutions are also possible, though a single solution is generally preferred.

The solvent for step (i) is selected from group consisting of C_3-6 ketone or a mixture thereof with water, N-methylpyrrolidone, C₃_6 amides, halo-substituted C₆- i 2 aromatic hydrocarbons propylene glycol, dimethyl sulfoxide, dimethyl carbonate, C alkyl alcohols such as methanol, ethanol, isopropanol, acetonitrile or a mixture thereof with water, C₂-6 alkyl acetates or their mixture with water, cellosolve, dimethyl carbonate, polyethylene glycol methyl ether and C₂.₈ ethers.

The solution obtained in step (i) may be stirred for 30 to 60 minutes at temperature of 40°C to 60°C. The temperature of the reaction mass may be gradually cooled and stirred.

The solution obtained in step (i) may be stirred for 1 to 2 hours at 5°C to 10°C The sieving of asenapine maleate in step (iii) is performed through 200 mesh. The milling step to obtain microcrystalline monoclinic Asenapine Maleate in step (v) comprises of jet milling performed with feeding pressure of about 3 kg and grinding pressure of about 4 kg.

The jet milling cycle may vary from 1 to 5 cycles to obtain (D95) less than about 10 microns. Another aspect of the present invention relates to a pharmaceutical composition comprising an effective amount of microcrystalline Asenapine Maleate in monoclinic form having particle size, in terms of d95, is less than 10 microns, a pharmaceutically acceptable excipient.

The composition can be an immediate release dosage form or an extended release dosage form or buccal or sublingual or injectable or embraces tablets as well as pellets/beads/spheroids or other encapsulated forms.

The compound can be in isolated and/or purified form, but such is not required.

The compound includes various physical forms of the salt including dissolved forms, oil or liquid forms, and solid forms including amorphous and crystalline forms. In yet another embodiment the invention encompasses a pharmaceutical composition comprising crystalline Asenapine Maleate monoclinic form and at least one pharmaceutically acceptable excipient.

Another aspect of the present invention relates to a pharmaceutical composition comprising an effective amount of Asenapine Maleate in monoclinic form having particle size, in terms of d95, is less than 100 microns and a pharmaceutically acceptable excipient.

Another embodiment of the invention encompasses the use of crystalline Asenapine Maleate monoclinic form having particle size, in terms of d95, is less than 100 microns for the manufacture of a medicament for the treatment of schizophrenia and acute mania associated with bipolar disorder.

The invention also encompasses pharmaceutical compositions comprising Asenapine salts of the invention. As used herein, the term "pharmaceutical compositions" or "pharmaceutical formulations" includes tablets, pills, powders, liquids, suspensions, emulsions, granules, capsules, suppositories, or injection preparations.

Pharmaceutical compositions containing the asenapine maleate of the invention may be prepared by using diluents or excipients such as fillers, bulking agents, binders, wetting agents, disintegrating agents, surface active agents, and lubricants. Various modes of administration of the pharmaceutical compositions of the invention can be selected depending on the therapeutic purpose, for example tablets, pills, powders, liquids, suspensions, emulsions, granules, capsules, suppositories, or injection preparations.

Another aspect of the present invention relates to the process for preparing amorphous form of asenapine maleate.

The reaction of asenapine maleate is preferably carried out in organic solvent or in mixture with water.

Another embodiment of the invention encompasses a process for preparing amorphous asenapine maleate comprising slurrying asenapine maleate in a solvent selected from a group consisting of organic solvent such as aromatic hydrocarbons, glycerol, tetrahydrofuran, esters, ethers, ketones, alcohols and water or a mixture thereof. Another embodiment of the invention encompasses a process for preparing amorphous asenapine maleate comprising spray drying a solution of asenapine maleate in alcoholic solvent.

Amorphous asenapine maleate can be isolated or recovered from the salt forming reaction by any convenient means. For example, the amorphous Asenapine Maleate can be precipitated out of a solution or reaction mixture. The precipitation may be spontaneous depending upon the solvent system used and the conditions. Alternatively, the precipitation can be induced by reducing the temperature of the solvent, especially if the initial temperature at contact is elevated.

In one general embodiment, there is provided a process for preparation an amorphous form of asenapine maleate, which includes one or more of the following steps:

a) providing a solution of asenapine maleate in a solvent or mixture of solvents; and b) obtaining amorphous form or asenapine maleate.

Step a) invovles providing a solution of asenapine maleate in a solvent or mixture of solvent.

The solution for step a) can be obtained by the known methods that include: (i) direct use of a reaction mixture containing asenapine maleate that is obtained in the course of its synthesis; or

(ii) dissolving asenapine maleate in a suitable solvent or mixture of solvents.

Suitable solvents that may be used in step a) include but are not limited to water; alcohols such as methanol, ethanol, isopropanol, 2-propanol, 1 -butanol, t-butyl alcohol, 1 -pentanol, 2-pentanol, amyl alcohol, ethylene glycol, glycerol and the like; ketones such as acetone, butanone, 2-pentanone, 3-pentanone, methyl butyl ketone, methyl isobutyi ketone, and the like; esters such as ethyl formate, methyl acetate, ethyl acetate, propyl acetate, t-butyl acetate, isobutyi acetate, hydrocarbons like toluene, xylene, methylene dichloride, ethylene dichloride, chlorobenzene, and the like, nitriles like acetonitrile, and polar aprotic solvents like Ν,Ν-dimethylformamide, N,N- dimethylacetamide, N-methylpyrrolidone, pyridine, dimethylsulfoxide, sulfolane, formamide, acetamide, propanamide, pyridine and the like; and mixtures thereof.

Step b) involves isolation of an amorphous form of asenapine maleate from the solution of step a). The isolation may be affected by removing solvent. Suitable techniques which may be used for the removal of solvent include using a rotational distillation device such as a Buchi otavapor, spray drying, agitated thin film dyring ("ATFD"), freeze drying (lyophilization), and the like or any other suitable technique.

Alternatively, isolation can be effected by addition of suitable antisolvent to the solution obtain in step a), optionally by concentrating the solution obtained in step a). Suitable anti-solvents that may be used can be selected from hydrocarbons like hexanes, n-heptane, n-pentane, cyclohexane, methylcyclohexane and the like; aromatic hydrocarbons like toluene, xylene, chlorobenzene, ethylbenzene and the like; ethers like diethyl ether, diisopropyl ether, t-butyl methyl ether, dibutyl ether, tetrahydrofuran, 1,4-dioxane, 2-methoxyethanol and the like.

The process for preparing amorphous asenapine maleate may further comprise a recovery process. The recovery of amorphous asenapine maleate may be done by a method that doesn't include a drying step. Such method includes, but is not limited to, filtering the suspension.

The above amorphous asenapine maleate may be prepared by a process comprising spray drying a solution of asenapine maleate in methanol. According to Remington: The Science and Practice of Pharmacy, 19th Ed., vol. II, pg. 1627, spray drying consists of bringing together a highly dispersed liquid and a sufficient volume of hot gas to produce evaporation and drying of the liquid droplets. A typical spray-drying apparatus includes a drying chamber, atomizing means for atomizing a solvent- containing feed into the drying chamber, a source of heated drying gas that flows into the drying chamber to remove solvent from the atomized-solvent-containing feed and product collection means located downstream of the drying chamber. Examples of such apparatus include Niro Models PSD- 1 , PSD-2 and PSD-4 (Niro A/S, Soeborg, Denmark).

Particularly, the solution is prepared by dissolving asenapine maleate in methanol. Particularly, the solution is spray-dried at an inlet temperature of from about room temperature to about 200° C, more preferably of about 60° C to about 120°C. Preferably, the solution is spray-dried at an outlet temperature of from about room temperature to about 120°C, more preferably of about 37° C to about 75°C.

Alternatively, asenapine salt can be isolated by evaporating the solvent and collecting residue. Such a method generally leads to an oil or solid amorphous form of asenapine salt. Similarly, an amorphous solid form of the asenapine salt compound can be recovered by spray drying or freeze drying or agitated thin film drying a solution containing the asenapine salt compound. In another general aspect, the invention encompasses a pharmaceutical composition comprising amorphous asenapine maleate and at least one pharmaceutically acceptable excipient.

One embodiment of the invention encompasses a pharmaceutical composition comprising amorphous asenapine maleate made by the processes of the invention, and at least one pharmaceutically acceptable excipient.

Yet another embodiment of the invention encompasses a process for preparing a pharmaceutical composition of asenapine maleate comprising combining amorphous asenapine maleate with at least one pharmaceutically acceptable excipient.

Another embodiment of the invention encompasses the use of amorphous asenapine maleate for the manufacture of a medicament for the treatment of schizophrenia and acute mania associated with bipolar disorder.

Another embodiment of the invention encompasses the use of amorphous asenapine maleate made by the processes of the invention for the manufacture of a pharmaceutical composition.

Having described the invention with reference to certain preferred embodiments, other embodiments will become apparent to one skilled in the art from consideration of the specification.

The monoclinic form and the amorphous form of asenapine maleate and process for its preparation described in the present invention is demonstrated in examples illustrated below.

These examples are provided as illustration only and therefore should not be construed as limitation of the scope of invention.

Examples:

Example 1: Preparation of amorphous asenapine maleate:

10.0 g of asenapine maleate dissolved in 300.0 ml of acetone at 25°C to 30°C. The content was stirred for 30 minutes at 25°C to 30°C. To this, 1.0 g charcoal was added and stirred for 30 minutes at 25°C to 30°C and washed with 50 ml acetone. To the filtrate is concentrated under vacuum below 45°C till 100 ml acetone remained and further 50 ml acetone was added and stirred till clear solution. To the reaction mixture 2.2 ml liquor ammonia solution was added into the reaction mixture followed by spray drying in JISL Mini spray drier LSD-48. The product was dried at 40°C±5°C under vacuum for 16 hours to obtain stable amorphous asenapine maleate. Example 2: Preparation of microcrystalline monoclinic form of asenapine maleate

100 g of asenapine free base and 500 ml of isopropanol were added at 25°C to 35°C and heated up to 45°C to 50°C and 40 g of maleic acid (40 g) was added. The reaction mass was stirred at 50°C to 55°C for 45 minutes to obtain clear solution. The reaction mass was gradually cooled to 25°C to 35°C and further cooled to 5°C to 10°C and stirred for two hours. The product was filtered under vacuum and washed with isopropanol (2 x 50 ml) to afford Asenapine Maleate. The obtained asenapine maleate was further treated with 200 ml of acetonitrile followed by treatment with 200 ml of ethanol and stirred for 30 minutes. The reaction mass was cooled to 5°C to 10°C and stirred for 2 hours. The product was filtered and washed with 50 ml of ethanol and further treated with 400 ml of ethanol at 25°C to 35°C and heated to 65°C to 70°C. The product was filtered and washed with ethanol. The reaction temperature was cooled to 50-55°C, further cooled to 20-25°C and stirred for 1 hour. The reaction temperature was cooled to 5°C to 10°C and stirred for 2 hours. The product was washed with 50 ml of chilled ethanol to afford monoclinic form of asenapine maleate.

(D95) = 230 microns.

The obtained asenapine maleate monoclinic form was sieved through 200 mesh resulted with (D95) less than about 30 microns.

Further jet milling with feeding pressure of about 3 kg and grinding pressure of about 4 kg for 1 or 2 cycles resulted in microcrystalline monoclinic form of asenapine maleate with (D95) less than about 10 microns i.e. (D95) = 5 microns.

Example 3: Preparation of substantially pure microcrystalline monoclinic form of asenapine maleate

100 g of monoclinic asenapine maleate (polymorphic purity 99.5%) having particle size (D95) less than 5 microns obtained by micronization was treated with 100 ml of ethanol at 25°C to 35°C and heated to 65°C to 70°C. The product was filtered and washed with ethanol. The reaction temperature was cooled to 50-55°C, further cooled to 20-25°C and stirred for 1 hour. The reaction temperature was cooled to 5°C to 10°C and stirred for 2 hours. The product was washed with 50 ml of chilled ethanol to afford substantially pure microcrystalline monoclinic form of asenapine maleate.

(D95) = 5 microns.

Claims

Claims:

1. Substantially pure monoclinic form of asenapine maleate having d95 particle size of less than about 100 microns.

2. Substantially pure microcrystalline monoclinic form of asenapine maleate having d95 particle size of less than 10 microns.

3. A process for preparing substantially pure microcrystalline monoclinic form of asenapine maleate having particle size in terms of d95 less than about 10 microns comprises;

a) treating asenapine with maleic acid in a solvent to obtain the solution;

b) obtaining asenapine maleate having (D95) particle size of about 250 microns;

c) sieving asenapine maleate obtained in step (ii);

d) isolating asenapine maleate with (D95) particle size less than about 30 microns; e) milling asenapine maleate obtained in step (iv); and

f) isolating substantially pure microcrystalline monoclinic form of asenapine maleate with (D95) particle size less than about 10 microns.

4. The process as claimed in claim 3(a), wherein the solvent comprises one or more of C3.6 ketones, water, N-methylpyrrolidone, C3-6 amides, halo-substituted C6-12 aromatic hydrocarbons, propylene glycol, dimethyl sulfoxide, dimethyl carbonate, C|.g alkyl alcohols, acetonitrile C₂-6 alkyl acetates, cellosolve, dimethyl carbonate, polyethylene glycol methyl ether and C₂-8 ethers.

5. The process as claimed in claim 3(a), wherein the solution may involve stirring along with the heating followed by cooling of the reaction mass.

6. The process as claimed in claim 3(a), wherein the solution may be stirred for 30 to 60 minutes at temperature of 40°C to 60°C.

7. The process as claimed in claim 3(a), wherein the solution may be stirred for 1 to 2 hours at temperature of 5°C to 10°C.

8. The process as claimed in claim 3(c), wherein sieving of asenapine maleate is performed through 200 mesh.

9. The process as claimed in claim 3(e), wherein milling is performed with feeding pressure of about 3 kg and grinding pressure of about 4 kg.

10. A process for preparing substantially pure microcrystalline monoclinic form of asenapine maleate, the process comprising:

a) milling asehapine maleate to obtain d95 particle size of less than about 10 microns; b) slurrying micronized asenapine maleate in one or more of suitable organic solvents to form a solution; and

1 1. The process as claimed in claim 10 (a), wherein the milling is performed with feeding pressure of about 3 kg and grinding pressure of about 4 kg.

12. The process as claimed in claim 10 (b), wherein the micronized asenapine maleate is having polymorphic purity of 99% to 99.5%.

13. The process as claimed in claim 10 (c), wherein the solvent comprises of one or more of C_3-6 ketones, water, N-methylpyrrolidone, C_{3 -}6 amides, halo-substituted C₆. 12 aromatic hydrocarbons, propylene glycol, dimethyl sulfoxide, dimethyl carbonate, C|_₈ alkyl alcohols, acetonitrile C₂_6 alkyl acetates, cellosolve, dimethyl carbonate, polyethylene glycol methyl ether and C₂_8 ethers.

14. The process as claimed in claim 10 (b), wherein the slurry may involve stirring along with the heating followed by cooling of the reaction mass.

15. The process as claimed in claim 14, wherein the reaction mass may be stirred for 30 to 60 minutes at temperature of 40°C to 60°C.

16. The process as claimed in claim 14, wherein the reaction mass may be stirred for 1 to 2 hours at temperature of 5°C to 10°C.

17. A pharmaceutical composition comprising an effective amount of asenapine maleate in substantially pure monoclinic form having d95 particle size of less than about 100 microns and a pharmaceutically acceptable excipient.

18. A process for preparing amorphous asenapine maleate of Formula (I),

the process comprises;

(a) providing a solution of asenapine maleate in a solvent or mixture of solvents; and (b) obtaining amorphous asenapine maleate.

19. The process as claimed in claim 18(a), wherein the solvent comprises one or more of water; alcohols such as methanol, ethanol, isopropanol, 2-propanol, 1-butanol, t- butyl alcohol, 1-pentanol, 2-pentanol, amy I alcohol, ethylene glycol, glycerol and the like; ketones such as acetone, butanone, 2-pentanone, 3-pentanone, methyl butyl ketone, methyl isobutyl ketone, and the like; esters such as ethyl formate, methyl acetate, ethyl acetate, propyl acetate, t-butyl acetate, isobutyl acetate, hydrocarbons like toluene, xylene, methylene dichloride, ethylene dichloride, chlorobenzene, and the like, nitriles like acetonitrile, and polar aprotic solvents like N,N- dimethylformamide, Ν,Ν-dimethylacetamide, N-methylpyrrolidone, pyridine, dimethylsulfoxide, sulfolane, formamide, acetamide, propanamide, pyridine and mixtures thereof.

20. The process as claimed in claim 18 (b), wherein amorphous form of asenapine maleate is obtained by suitable techniques comprises one or more of Buchi Rotavapor, spray drying, agitated thin film dyring ("ATPD⁵'), freeze drying (lyophilization) or use of sutiable anti-solvent selected from hexanes, n-heptane, n- pentane, cyclohexane, methylcyclohexane, toluene, xylene, chlorobenzene, ethylbenzene, diethyl ether, diisopropyl ether, t-butyl methyl ether, dibutyl ether, tetrahydrofuran, 1 ,4-dioxane, 2-methoxyethanolor.