FORM 2
THE PATENT ACT, 1970
(39 of 1970) &
The Patents Rules. 2003
i
COMPLETE SPECIFICATION
(See section 10 and rule 13)
Title of the invention
"NOVEL POLYMORPHIC FORMS OF ALCAFTAD1NE"
Enaltec Labs Pvt Ltd. an Indian Company, having its Registered Office at 17lthFloor, Kesar Solitaire. Plot No.5 Sector-19, Sanpada, Navi Mumbai Maharashtra. India. Pin Code: 400705
1. The following specification particularly describes the invention and the manner in which it is to
be performed.

NOVEL POLYMORPHIC FORMS OF ALCAFTADINE
FIELD OF THE INVENTION:
The present invention relates to novel polymorphic forms of alcaftadine. The present invention further relate to processes of preparing novel polymorphic forms of alcaftadine and pharmaceutical composition thereof.
BACKGROUND OF THE INVENTION:
Alcaftadine is chemically 6, 11-dihydro-ll-(l-methyl-4-piperidinylidene)-5H-imidazo [2. 1-b] [3] benzazepine-3-carboxaldehyde and is known from U.S Patent No. 5,468,743 and is represented by a compound of structural formula I.

Alcaftadine is a H1 histamine receptor antagonist sold in USA under the proprietary name of "LASTACAFT" and is indicated for the prevention of itching associated with allergic conjunctivitis.
The process of preparing alcaftadine compound of structural formula I is disclosed in US Patent No. 5,468,743 for preparing "alcaftadine analogous compound", which is represented below in Scheme no. I, Scheme no. II and Scheme no. III. The alcaftadine obtained according to Scheme no. I, Scheme no. II and Scheme no. IIIis characterized by melting point 171.6°C (referred herein after as Form I).

A survey of the literature on alcaftadine did not provide any reference to its crystal structure or the possibility of different polymorphs. Information about the solid-state properties of a drug substance is important. For example, different forms may have significantly different solubilities. Further, the handling and stability of a drug substance may depend critically on the solid state of the drug.
Polymorphism is defined as "the ability of a compound to crystallize in more than one distinct crystal species" and different crystal arrangements of the same chemical compound are termed polymorphs. Polymorphs of the same compound arise due to differences in the internal arrangement of atoms and have different free energies and therefore different physical properties such as solubility, chemical stability, melting point, density, flow properties; bioavailability and so forth.
The inventors of the present application have found that alcaftadine can exhibits polymorphism i.e. alcaftadine can exist in different polymorphic forms and accordingly novel polymorphic forms of alcaftadine are provided.

SUMMARY OF THE INVENTION:
First aspect of the present invention is to provide novel polymorphic forms of alcaftadine.
According to another aspect, the present invention relates to crystalline forms of alcaftadine.
According to another aspect, the present invention relates to a-crystalline form of alcaftadine.
According to another aspect, the present invention relates to process for the preparation of a-crystalline form of alcaftadine.
According to another aspect, the present invention relates to a process of preparing a-crystalline form of alcaftadine comprising the steps of:
a. suspending crude alcaftadine in an organic solvent,
b. stirring suspension obtained in step-a and,
c. isolating a-crystalline form of alcaftadine.
According to another aspect, the present invention relates to a process of preparing a-crystaliine form of alcaftadine comprising the steps of:
a. suspending crude alcaftadine in a ketone solvent,
b. stirring suspension obtained in step-a and.
c. isolating a-crystalline form of alcaftadine.
According to another aspect, the present invention relates to β-crystalline form of alcaftadine.
According to another aspect, the present invention relates to process for the preparation of β-crystalline form of alcaftadine.
According to another aspect, the present invention relates to a process of preparing β-crystalline form of alcaftadine comprising the steps of:
a. suspending crude alcaftadine in an organic solvent,

b. stirring suspension obtained in step-a and,
c. isolating p-crystalline form of alcaftadine.
According to another aspect, the present invention relates to a process of preparing p-crystalline form of alcaftadine comprising the steps of:
a. suspending crude alcaftadine in an ether solvent,
b. stirring suspension obtained in step-a and,
c. isolating P-crystalline form of alcaftadine.
Another aspect of the present invention is to provide amorphous form of alcaftadine.
Another aspect of the present invention is to provide process for the preparation of amorphous form of alcaftadine.
Another aspect of the present invention is to provide a process of preparing amorphous form of alcaftadine comprising the steps of:
a. preparing a solution of alcaftadine in an organic solvent and
b. recovering alcaftadine in the amorphous form from the solution thereof by the removal of
the solvent by techniques selected from the group comprising of spray-drying or freeze-
drying.
Another aspect of the present invention is to provide a process of preparing amorphous form of alcaftadine comprising the steps of:
a. preparing a solution of alcaftadine in an organic solvent,
b. removing the solvent from the solution obtained in step-a by agitated thin film drying.
and
c. recovering alcaftadine in the amorphous form from the agitated thin film dryer.
Another aspect of the present invention is to provide a process of preparing amorphous form of alcaftadine comprising the steps of:

a. melting crystalline form of alcaftadine and
b. recovering alcaftadine in the amorphous form.
Another aspect of the present invention is to provide a pharmaceutical composition comprising α-crystalline form of alcaftadine.
Another aspect of the present invention is to provide a pharmaceutical composition comprising β-crystalline form of alcaftadine.
Another aspect of the present invention is to provide pharmaceutical composition comprising amorphous form of alcaftadine.
BRIEF DESCRIPTION OF THE DRAWINGS:
Figure 1 depicts X-ray diffraction pattern of α-crystalline form of alcaftadine Figure 2 depicts Infra-Red spectra of a-crystalline form of alcaftadine Figure 3 depicts X-ray diffraction pattern of β-crystalline form of alcaftadine Figure 4 depicts Infra-Red spectra of β-crystalline form of alcaftadine Figure 5 depicts X-ray diffraction pattern of amorphous form of alcaftadine
DETAIL DESCRIPTION OF THE INVENTION:
The present invention relates to novel polymorphic forms of alcaftadine and process for the preparation thereof.
The present invention further relates to a-crystalline form of alcaftadine characterized by X-ray diffraction pattern having peaks at 8.3, 10.9, 12.7, 14.7, 15.1, 15.4, 16.0, 16.5, 17.2. 17.7. 18.7. 19.1, 19.9,21.1, 22.0, 22.7,24.1, 24.7, 25.1, 26.3, 26.7,27.2, 28.0, 28.5 ± 0.2 degrees two theta.
In another embodiment the present invention relates to a-crystalline form of alcaftadine characterized by X-ray diffraction pattern as depicted in Figure 1.

In another embodiment the present invention relates to α-crystalline form of alcaftadine characterized by Infra-Red spectrum as depicted in Figure 2.
In another embodiment the present invention relates to β-crystalline form of alcaftadine characterized by X-ray diffraction pattern having peaks at 10.0, 11.4, 12.0. 15.5. 16.2. 18.4. 19.6. 20.2,20.5,22.0,23.1, 23.5, 24.6, 25.4, 25.8, 28.8, 31.3 ± 0.2 degrees two theta.
In another embodiment the present invention relates to β-crystalline form of alcaftadine characterized by X-ray diffraction pattern as depicted in Figure 3.
In another embodiment the present invention relates to β-crystalline form of alcaftadine characterized by Infra-Red spectrum as depicted in Figure 4.
In another embodiment the present invention relates to an amorphous form of alcaftadine characterized by X-ray diffraction pattern as depicted in Figure 5.
The crude alcaftadine used according to the present invention can be prepared by methods disclosed in the art such as those described in U.S Patent No. 5.468,743. which is incorporated herein by reference.
The a-crystalline form of alcaftadine is prepared by suspending crude alcaftadine in an organic solvent, stirring the resulting suspension at a temperature in the range of 0°C to 50°C for a period of 30 minutes to 6 hours and isolating the a-crystalline form of alcaftadine from the suspension.
The β-crystalline form of alcaftadine is prepared by suspending crude alcaftadine in an organic solvent, stirring the resulting suspension at a temperature in the range of 0°C to 50°C for a period of 30 minutes to 8 hours and isolating the β -crystalline form of alcaftadine from the suspension.
Organic solvent according to the present invention can be selected from the group comprising. but not limited to, alcohols, furans, ethers, ketones, nitriles, esters, hydrocarbons such as

halogenated aliphatic hydrocarbon solvents or the like or mixtures thereof. Ketone solvent can be selected from the group comprising, but not limited to acetone, methyl ethyl ketone, methyl isobutyl ketone, dibutyl ketone, diethyl ketone, dipropyl ketone, diisopropyl ketone, methyl butyl ketone, methyl propyl ketone, methyl isopropyl ketone, ethyl isopropyl ketone or mixture(s) thereof.
The ether solvent can be selected from the group comprising, but not limited to. tetrahydroliiran. dioxane, diethyl ether, diisopropyl ether, dibutyl ether, methyl tertiary butyl ether, methyl ethyl ether, methyl isobutyl ether or mixture(s) thereof.
The alcohol solvents can be selected from the group comprising, but not limited to, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, t-butanol, pentanol or mixture(s) thereof.
The ester solvents can be selected from the group comprising, but not limited to, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, tertiary butyl acetate, pentyl acetate or mixture(s) thereof
The nitrile solvents can be selected from the group comprising, but not limited to. acetnnimle. propionitrile or mixture(s) thereof.
The halogenated aliphatic hydrocarbon solvents can be selected from the group comprising, but not limited to, dichloromethane, dichloroethane. chloroform, carbon tetrachloride or mixture(s) thereof.
The crystalline forms (α and/or β) of alcaftadine may be isolated by any known process in the art such as filtration, centrifugation, washing, drying or the combinations thereof.
The isolated crystalline forms (α and/or β) of alcaftadine may be dried at a temperature in the range of 40°C to 110°C for a period of 2 hours to 12 hours under reduced pressure.

A solution of crude alcaftadine in an organic solvent may be prepared by dissolving alcaftadine in an organic solvent at a temperature in the range of 20°C to 60°C.
Alternatively, such a solution may be obtained directly from a reaction in which alcaftadine is formed.
In another embodiment according to present invention, the solvent may be removed from the solution by a technique which includes, for example, spray drying and freeze drying.
In one aspect, alcaftadine amorphous form may be recovered from the solution using a spray drying technique. A Mini-Spray Dryer (Model: Buchi 190, Switzerland) can be used. The Buchi 190 Mini-Spray Dryer operates on the principle of nozzle spraying in a parallel flow, i.e., the sprayed product and the drying gas flow in the same direction. The drying gas can be air or inert. gases such as nitrogen, argon and carbon dioxide.
In another aspect, alcaftadine amorphous form may be recovered from the solution using a freeze drying technique. A freeze dryer (Model; Virtis Genesis SQ Freeze Dryer) can be used in this technique. The Virtis Genesis SQ Freeze Dryer operates on the principle of lyophilizatiom i.e., a process of stabilizing initially wet materials (aqueous solution or suspensions) by freezing them. then subliming the ice while simultaneously desorbing some of the bound moisture (primary drying). Following removal of the ice. desorption may be continued (secondary drying). This process may be carried out under vacuum.
The spray drying may be accomplished using a spray dryer which operates on the principle of nozzle spraying in a parallel flow, i.e., the sprayed product and the drying gas flow in the same direction. The drying gas can be air or one or more inert gases such as nitrogen, argon, and carbon dioxide. Moreover, the product obtained may be further or additionally dried to achieve the desired moisture values. For example, the product may be further or additionally dried in α tray drier, dried under vacuum and/or in a Fluid Bed Dryer.

The solution of alcaftadine may be optionally treated with activated charcoal and the resulting solution is filtered through hyflo bed to get filtrate.
The resulting filtrate is fed into an agitated thin film dryer (AT.FD). The solvent is subsequently removed from the solution by agitated thin film drying.
The drying process may be accompanied by heating at a temperature in the range of 30°C to 60°C under reduced pressure.
The feeding rate of the solution may be controlled in such α way to facilitate the thin film formation and the evaporation rate. The rotor and vapor duct can have a sealing system so that the drying can preferably be carried under vacuum. Vacuum operation also facilitates amorphous form of alcaftadine to be obtained without degradation.
The crystalline form of alcaftadine may be melted at a temperature in the range of 160°C to 190°C.
The alcaftadine amorphous form may be recovered by the steps of cooling and milling of melted alcaftadine. The milling of melted alcaftadine may be carried out in a mortar and pestle.
The cooling of melted alcaftadine may be carried out up to the temperature in the range of 20-30°C.
The term "recovering alcaftadine in the amorphous form" according to the present invention includes unloading, amassing, gathering, scaling and/or piling amorphous form of alcaftadine.
The amorphous form of alcaftadine may be optionally further dried under vacuum at a temperature in the range of 40°C to 110°C for 2 hours to 8 hours to obtain amorphous form of alcaftadine with desired residual solvent content.

fn another embodiment the present invention relates to the pharmaceutical composition of alcaftadine comprising α-crystalline form of alcaftadine and one or more pharmaceuticaHy acceptable excipients,
In another embodiment the present invention relates to the pharmaceutical composition of alcaftadine comprising β-crystalline form of alcaftadine and one or more pharmaceuticaHy acceptable excipients.
In another embodiment the present invention relates to the pharmaceutical composition of alcaftadine comprising amorphous form of alcaftadine and one or more pharmaceuticaHy acceptable excipients.
XRD diffraction measurement was performed on X-Ray powder diffractometer Bruker D8
Advance powder diffractometer with the detector Lynxeye (Bruker). The analysis conditions
were as follows:
Scan range [°2-theta]: 2-39.98;
Scan mode: Continuous;
Step size [°2-theta]: 0.0170°;
Scan step time[s]: 51.04 seconds;
Sample spin: 15 rpm;
Sample holder: glass;
Measurement Temperature [°C]: 25
Anode Material: Cu
K-Alpha [A]: 1.54060
Prior to analysis, the samples were gently ground by means of mortar and pestle in order to obtain a fine powder. The sample might be mixed with n-dodecane in order to avoid the environment contamination by airborne particles coming from the powder. The ground sample or its suspension with n-dodecane was adjusted into a cavity of the sample holder and the surface of the sample was smoothed by means of a cover glass.

EXAMPLES:
In the following examples, the preferred embodiments of the present invention are described only by way of illustrating the process of the invention. However, these are not intended to limit the scope of the present invention in any way.
Example 1: Preparation of a-crystalline form of alcaftadine
Crude alcaftadine (l0 gm) was suspended in acetone (30ml) at 25°C and resulting suspension was
stirred 3 hours at 25°C. The resulting solids were filtered, washed with acetone (10ml) and dried
at 45°C for 8 hours under reduced pressure.
Yield: 9.7gm
XRD: As depicted in Figure 1
IR: As depicted in Figure 2
Purity: 99.96% (By HPLC)
Example 2: Preparation of p-crystalline form of alcaftadine
Crude alcaftadine (lOgm) was suspended in diethyl ether (40ml) at 25-30°C and resulting
suspension was stirred 2 hours at 25°C. The resulting solids were filtered, washed with diethyl
ether (10ml) and dried at 50°C for 12 hours under reduced pressure.
Yield: 9.8gm
XRD: As depicted in Figure 3
IR: As depicted in Figure 4
Purity: 99.87% (By HPLC)
Example 3: Preparation of amorphous form of alcaftadine.
Crystalline alcaftadine (lOgm) was dissolved in isopropanol (60ml) at 30-40°C. The clear
solution was subjected to spray drying in a mini spray dryer at an inlet temperature of 80°C and
an outlet temperature of 50°C with a feed rate of 15 ml/minute. Alcaftadine in an amorphous
form was thus isolated.
Yield: 9.5 gm
Purity: 99.97% (By HPLC)

Example 4: Preparation of amorphous form of alcaftadine.
A solution of alcaftadine (l00gm) in methanol (1200ml) was fed into ATFD at a vacuum of 50-
100 mm Hg and a jacket temperature of 45-54°C. The obtained solid was dried under reduced
pressure at a temperature of 70°C for 5 hours to get title compound.
Yield: 82gm
Purity: 99.85% (By HPLC)
Example 5: Preparation of amorphous form of alcaftadine.
A solution of alcaftadine (lOOgm) in methanol (1200ml) was treated with activated charcoal
(l0gm) and the resulting solution was filtered through hyflo bed to get filtrate. The resulting
filtrate was fed into ATFD at a vacuum of 50-100 mm Hg and a jacket temperature of 45-54°C.
The obtained solid was dried in a vacuum tray drier under reduced pressure at 70°C for 6 hours
to get title compound.
Yield: 80gm
Purity: 99.95% (By HPLC)
Example 6: Preparation of amorphous form of alcaftadine.
Crystalline alcaftadine (lOgm) was placed in to an oven at 175°C for 45 minutes. The melted
alcaftadine was cooled to 25°C and then it was milled in a mortar and pestle to get title
compound.
Yield: 9.8 gm
Purity: 99.94% (By HPLC)

WE CLAIM:
1. A process of preparing α-crystalline form of alcaftadine comprising the steps of:
a. suspending crude alcaftadine in an organic solvent.
b. stirring suspension obtained in step-a and.
c. isolating a-crystalline form of alcaftadine.
2. The process according to claim no. 1, wherein the a-crystalline form of alcaftadine is
characterized by:
a) X-ray diffraction pattern having peaks at 8.3, 10.9, 12.7, 14.7, 15.1, 15.4, 16.0, 16.5, 17.2, 17.7, 18.7, 19.1, 19.9, 21.1, 22.0, 22.7, 24.1, 24.7, 25.1, 26.3, 26.7. 27.2, 28.0, 28.5 • 0.2 degrees two theta or
b) having substantially the same X-ray diffraction pattern as depicted in Figure 1 or
c) having substantially the same Infra-Red spectrum as depicted in Figure 2.

3. The process according to claim no. 1, wherein organic solvent is a ketone solvent selected from the group comprising of acetone, methyl ethyl ketone, methyl isobuty] ketone, dibutyl ketone, diethyl ketone, dipropyl ketone, diisopropyl ketone, methyl butyl ketone. methyl propyl ketone, methyl isopropyl ketone, ethyl isopropyl ketone or mi\ture(s) thereof.
4. A process of preparing p-crystalline form of alcaftadine comprising the steps of:
a. suspending crude alcaftadine in an organic solvent,
b. stirring suspension obtained in step-a and,
c. isolating β-crystalline form of alcaftadine.
5. The process according to claim no. 4, wherein the β-crystalline form of alcaftadine is
characterized by:
a) X-ray diffraction pattern having peaks at 10.0, 11.4, 12.0, 15.5, 16.2, 18.4, 19.6, 20.2, 20.5,22.0,23.1, 23.5, 24.6, 25.4,25.8,28.8, 31.3 ± 0.2 degrees two theta or

b) having substantially the same X-ray diffraction pattern as depicted in Figure 3 or
c) having substantially the same Infra-Red spectrum as depicted in Figure 4.

6. The process according to claim no. 4, wherein organic solvent is an ether solvent selected from the group comprising of tetrahydrofuran. dioxane, diethyl ether. diisopropyl ether. dibutyl ether, methyl tertiary butyl ether, methyl ethyl ether, methyl isobutyl ether or mixture(s) thereof.
7. A process of preparing amorphous form of alcaftadine comprising the steps of:
a. preparing a solution of alcaftadine in an organic solvent and
b. recovering alcaftadine in the amorphous form from the solution thereof by the
removal of the solvent by technique selected from the group comprising of agitated
thin film drying, spray-drying or freeze-drying.
8. The process according to claim no. 7, wherein organic solvent is selected from the group comprising of ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, dibutyl ketone, diethyl ketone, dipropyl ketone, diisopropyl ketone, methyl butyl ketone, methyl propyl ketone, methyl isopropyl ketone, ethyl isopropyl ketone or mixture(s) thereof; alcohol solvents such as methanol, ethanol, propanol, isopropanol. butanol, isobutanol, t-butanol, pentanol or mixture(s) thereof; ester solvents such as ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, tertiary butyl acetate, pentyl acetate or mixture(s) thereof; nitrile solvents such as acetonitrile, propionitrile or mixture(s) thereof; halogenated aliphatic hydrocarbon solvents such as dichloromethane, dichloroethane, chloroform, carbon tetrachloride or mixture(s) thereof; and/or ether solvents such as tetrahydrofuran, dioxane, diethyl ether, diisopropyl ether, dibutyl ether. methyl tertiary butyl ether, methyl ethyl ether, methyl isobutyl ether or mixture(s) thereof.
9. A process of preparing amorphous form of alcaftadine comprising the steps of: a. melting crystalline form of alcaftadine and

b. recovering alcaftadine in the amorphous form.
10. The process according to claim no. 9, wherein crystalline form of alcaftadine is melted at a temperature in the range of 160°C to 190°C.