FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
&
THE PATENT RULES, 2003
PROVISIONAL SPECIFICATION
(See section 10 and rule 13)
"CYCLODEXTRIN COMPLEXES OF ATOVAQUONE"
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 describes the invention.

CYCLODEXTRIN COMPLEXES OF ATOVAQUONE
The present invention relates to inclusion complexes of trans -2-[4-(4-chlorophenyl)cyclohexyl]-3-hydroxy-l,4-naphthalenedione a compound of formula I with cyclodextrins, a method lor their preparation and pharmaceutical compositions containing these complexes for therapeutic use.
The compound of formula I, commonly known as atovaquone, is an antiprotozoal agent used in the treatment and/or prophylaxis of Pneumocystis carinii pneumonia. Further uses of atovaquone as a therapeutic agent for toxoplasmosis and cryptosporidiosis are disclosed in European Patent application nos. EP 0445141 and 0496729, respectively.

Atovaquone is a yellow crystalline solid that is practically insoluble in water. The efficacy of atovaquone as a therapeutic agent is limited because of its oral bioavailability, which may be ascribed to its poor aqueous solubility.
Conventional means of improving bioavailability by reducing particle size of atovaquone, and therefore surface area available for dissolution, have been reported to be disadvantageous. A particular problem reported is that conventional processes of particle size reduction, such as air jet milling, were incapable of reducing the particle size of atovaquone below 6 microns. Further reduction was found to cause fracture of the crystal structure of atovaquone, thereby leading to oozing of a red dye when such milled material was suspended in an aqueous vehicle. US 6,649,659 claims microfluidized particles of atovaquone having mean particle size in the range 0.1 to 3 microns, produced using a microlfuidizer, and compositions thereof, wherein the compositions have improved bioavailability. The process of micro fluidization was also found not to cause fracture of the crystal structure of atovaquone.
Cyclodextrins are naturally occurring cyclomaltooligosaccharides consisting of 6(a). 7(b) or 8(y) (l->4) D-glucopyranosidic units. It has now been found that atovaquone can be advantageously
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complexed by inclusion into a, b or y-cylodextrins or with modified derivatives of cyclodextrins. We have found the complex to provide enhanced aqueous solubility and dissolution of atovaquone, thus providing atovaquone in a more bioavailable form.
The preparation of atovaquone-cyclodextrin complexes can be carried out in any of the following ways:
• Dissolution of the selected cyclodextrin in aqueous medium and mixing with a solution of atovaquone in an organic solvent, and isolation of the complex.
• Dissolution of the selected cyclodextrin and atovaquone in an aqueous medium containing a volatile amine, and isolation of the complex by drying up using flash evaporation, spray drying or freeze drying.
• Dissolution of the selected cyclodextrin and atovaquone in aqueous medium comprising a water miscible solvent and a volatile amine; isolation of the complex by drying up using flash evaporation, spray drying or freeze drying.
The complexes of atovaquone with these cyclodextrins possess high aqueous solubility, provide rapid absorption, enhanced bioavailability and better tolerability. In these complexes, atovaquone and cyclodextrin may be present in a molar ratio between 1:1 to 1:5, preferably between 1:2 to 1:3.
The following examples are provided only for the purpose of illustrating the invention, and in no way they may be construed as a limitation and scope of the invention.
Example-!: Preparation of atovaquone -b-cyclodextrin complex
To a stirred mixture of P-cyclodextrin in dematerialized water at 60-65°C is added atovaquone. Liquor ammonia is then added, followed by 2-propanol, whereby a clear reddish solution results. The solution is flash dried under vacuum at 85-90°C to obtain a yellowish powder of the atovaquone-cyclodextrin complex.
The quantities of ingredients as used for the preparation of atovquone-p-cyclodextrin 1:1, 1:2 and 1:3 complexes are provided in Tables 1-3 below:

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Table 1 -Atovaquone -b-cyclodextrin (1:1)
Materials Unit Quantity Mole ratio
Atovaquone g 0.50 1.00
b-cycIodextrin (on anhyd. Basis) g 1.55 1.00
Ammonia solution (23-25%) ml 1.00 -
2-Propanol ml 10.00 -
Demineralised Water ml 25.00 -
Table 2 - Atovaquone -b-cyclodextrin (1:2)
Materials Unit Quantity Mole ratio
Atovaquone g 0.50 1.00
p-cyclodextrin (on anhyd. Basis) g 3.10 2.00
Ammonia solution (23-25%) ml 1.00 -
2-Propanol ml 10.00 -
Demineralised Water ml 25.00 -
Table 3 - Atovaquone -b-cyclodextrin (1:3)
Materials Unit Qty Mole ratio
Atovaquone gm 0.50 1.00
p-cyclodextrin (on anhyd. Basis) gm 4.65 3.00
Ammonia solution (23-25%) ml 1.00 -
2-Propanol ml 10.00 -
Demineralised Water ml 25.00 -
Example-2: In-vitro dissolution profile of Atovaquone -b-cyclodextrin complexes
The drug release profiles of atovaquone -P-cyclodextrin complexes (Atv-b-CD) were compared with microfluidized atovaquone (commercially available as Mepron) and unmilled atovaquone, in 900ml of pH 8 sodium phosphate buffer containing 0.5% SLS in a United Stales Pharmacopoeia type II dissolution apparatus, at a speed of 50rpm. The results are recorded in Table 4 below.
Table 4

Time (min) Medium: 900ml, pH 8.0 Sodium Phosphate Buffer with 0.5% SLS, USP II, 50 rpm
% drug released
Trial I Trial II Trial III Microfluidized Atovaquone (MEPRON) Atovaquone
Atv-b-CD(1:1) Atv-b-CD (1:2) Atv-b-CD(1:3) (5A002)
0 0.00 0.00 0.00 0.00 0.00
15 2.06 56.87 59.18 27.9
30 2.87 62.62 65.38 32.73
45 3.68 63.03 67.91 34.93
60 3.02 62.45 70.41 34.55
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The data clearly demonstrates that atovaquone- b-cyclodextrin complexes (1:2 and 1:3) have higher release of the drug when compared with unmilled atovaquone and microfluidized atovaquone.
The drug release profiles of atovaquone -b-cyclodextrin complex (Atv-b-CD) was also compared with microfluidized atovaquone (commercially available as Mepron) and unmilled atovaquone, in 900ml of pH 8 sodium phosphate buffer containing 40% 2-propanol, in a United States Pharmacopoeia type II dissolution apparatus, at a speed of 50rpm. The results are recorded in Table 5 below.
Table 5

Time(min) Medium: 900ml, pH 8.0 Sodium Phosphate Buffer with 40% TPA, USP IT, 50 rpm
% drug released
Atovaquone atovaquone -b-cyclodextrin (1:3) Microfluidized Atovaquone (MEPRON)
(1:3) (5A002)
0 0.00 0.00 0.00
15 51.60 84.80 44.94
30 55.59 99.59 50.32
45 58.50 102.31 51.71
60 59.50 102.74 52.77
The data clearly demonstrates that atovaquone-b-cyclodextrin complex (1:3) has higher release of the drug when compared with microfluidized atovaquone.
Dated this 26th day of April 2007.

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