FORM 2
THE PATENTS ACT, 1970
(39 of l970)
AND
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rulel3)
1. TITLE OF THE INVENTION:
"LYOPHILIZED IXABEPILONE AND A PROCESS THEREOF'
2. APPLICANT (S):
(a) NAME: BDR Pharmaceuticals International Pvt. Ltd.,
(b) NATIONALITY; Indian Company incorporated under the Indian
Companies ACT, 1956
(c) ADDRESS: 407-408 Sharda chambers, New Marine Lines, Mumbai 400020,
Maharashtra, India.
3.PREAMBLE TO THE DESCRIPTION:
The following specification describes the invention and the manner in which it is to
be performed.

TECHNICAL FIELD:
This invention relates to a stable and easy to administer lyophilized Ixabepilone for injection after reconstitution through any suitable parenteral diluent. The invention further describes the solvents and excipients as well as process for lyophilisation of Ixabepilone.
BACKGROUND AND PRIOR ART:
Epothilones are macrolide compounds having structure as below,

Where R is H for epothilone A and R is CH3 for epothilone B useful for treating hyper-proliferative cellular diseases such as tumor cells by exerting microtubule stabilizing effects. Various Epothilone analogs are disclosed in international application publication Nos. WO/1993/10121 and WO/1997/19086.
Ixabepilone is a potent anticancer agent for the treatment of aggressive metastatic or locally advanced breast cancer no longer responding to currently available
WO/1999/02514 discloses various Epothilone analogs and their pharmaceutically acceptable salts, solvates and hydrates including Ixabepilone (example 3), their synthesis procedures and use in the treatment of hyperproliferative cellular diseases as well as lyophilisation of epothilone analogues. Ixabepilone (1R,5S,6S,7R,10S,14S,16S)-6,10-dihydroxy-l,5,7,9,9-pentamethyl-14-[(E)-l-(2-ethyl-l,3-thiazol-4-yl)prop-l-en-2-yl]-17-oxa-13-azabicyclo[14.1.0] heptadecane-8,12-dione (Formula I) is a semisynthetic analog of epothilone B known since 1997.


chemotherapies and retains activity in cases where tumor cells are insensitive to paclitaxel which also acts to stabilize microtubules.
In spite of the prior art disclosure, a specific Patent, IN224075 have been granted to Bristol Myers Squibb arising out of a national phase application of WO/2001/070716 describes the process of lyophilisation of epothilone analogue Ixabepilone using a mixture of known organic solvents and excipients i.e. at least 50% v/v tertiary butyl alcohol and water and reconstituting in polyethoxyylated castor oil and anhydrous ethanol and then diluting with lactated ringer's solution.
There have been further Patent Applications by Dr. Reddys filed in India on lyophilized Ixabepilon such as 2089/CHE/2011 and 11/CHE/2011 which has equivalent US granted Patent US8618146 describes the use of at least 20% tertiary butyl alcohol with acetone or acetonitrile for lyophilisation of Ixabepilone.
The prior art Patents or Patent Applications only differ in selection of solvents and excipients. The temperature and pressure ranges for primary and secondary drying during lyophilisation cycle are disclosed in prior art or substantially within the commercial ranges detailed and claimed by commercial lyophilizers or freeze drying equipments in market available for procurement and utilisation and are as per their standard leaflets and SOPs of Instruction Manuals of Iyophilizers available in the market place.
Ixabepilone is acid labile with maximum stability in aqueous solution with pH in the neutral to alkaline range. Thus, Ixabepilone is susceptible to degradation, decomposition, or deactivation in aqueous solution, particularly in acidic solutions. Lyophilized preparations of the epothilone analogue Ixabepilone described in prior arts are accompanied with the limitation of necessity of smaller batch size as well as the residual solvents issues.
The present invention have attempted to overcome these problems of lyophilisation processes of Ixabepilone by employing buffers alongwith the suitable organic solvents.

DETAIL DESCRIPTION OF THE INVENTION:
Ixabepilone being sensitive to low pH and acidic conditions and is susceptible to degradation, decomposition in aqueous particularly acidic solutions, the present inventors have successfully formulated Ixabepilon for lyophilisation using pharmaceutically acceptable buffers i.e. citrate buffer, phosphate buffer preferably citrate buffer with the known pharmaceutically acceptable organic solvents selected from i.e. anhydrous ethanol, isopropyl alcohol,benzyl alcohol,tertiary butyl alcohol or mixture thereof.
It has been observed that in presence of suitable buffers in preferred organic solvents in absence of water, Ixabepilone could be lyophilized into a stable amorphous powder ready for reconstitution and delivery to the patients through infusions such as normal saline or others.
Some of the combinations of buffers and solvents have been evaluated as given in table 1.
Table 1

Combination solvent system Ratio
Citrate Buffer(pH6.2) and benzyl alcohol 70:30 to 50:50
Phosphate Buffer(pH6-7.5) and benzyl alcohol 70:30 to 50:50
Citrate Buffer (pH6.2) and anhydrous ethanol 70:30 to 50:50
Phosphate Buffer (pH6-7.5) and anhydrous ethanol 70:30 to 50:50
Citrate Buffer(pH6.2) and isopropyl alcohol 70:30 to 50:50
Phosphate Buffer(pH6-7.5) and isopropyl alcohol 70:30 to 50:50
Citrate Buffer (pH6.2) and isopropyl alcohol and anhydrous ethanol 70:15:15 to 50:25:25
Phosphate Buffer (pH6-7.5) and isopropyl alcohol and anhydrous ethanol 70:15:15 to 50:25:25
Citrate Buffer (pH6.2) and benzyl alcohol and anhydrous ethanol. 70:15:15 to 50:25:25
Phosphate Buffer (pH6-7.5) and benzyl alcohol and anhydrous ethanol. 70:15:15 to 50:25:25
Citrate Buffer (pH6.2) and acetyl acetone and anhydrous ethanol. 70:15:15 to 50:25:25
Phosphate Buffer (pH6-7.5) and acetyl acetone and anhydrous ethanol. 70:15:15 to 50:25:25
Preferred combination of buffer and solvent is citrate buffer with benzyl alcohol and citrate buffer with anhydrous ethanol and benzyl alcohol or acetyl acetone. The ratio is in the range of 70:15:15 to 50:25:25. Several lyophilization cycles were performed by using

various combinations of shelf temperature and chamber pressure during primary drying and secondary drying to obtain lyophilized powder.
The primary drying of the resulting solution is carried out at suitable temperatures in the range of-80°c to 50°c under vacuum from about 5 millitorr to about 300 millitorr for an extended period to form a primary lyophilized product. X-ray Diffraction (XRD) technique can be used to confirm the amorphous nature of the lyophilized product.
The secondary drying of the lyophilisation cycle was carried out at temperatures from 10°c to 45°c under vacuum of from about 70 millitorr to about 300 millitorr for a period from about 24 hours to about 96 hours to provide a lyophilized product. Primary as well as secondary drying was undertaken as per procedures described in instruction manuals of commercial lyophilizers in use (Minifast, Lyomax, Lyofax) with protection from exposure to light. In the preferred embodiment, citrate buffer such as sodium citrate pH 62 in combination with preferred organic solvent in the range of 70:30 to 50:50 preferably 50:50. The resulting dry lyophilized amorphous powder can be reconstituted for use with a suitable parenteral diluent as known in the prior art resulting in the final concentration of 3mg per ml.
Formulations of the embodiments of the present invention have been tested for their storage stability under stress conditions such as 40°c and 75% relative humidity and found to be optimum stable.
Example I:
Ixabepilone is dissolved in anhydrous ethanol and preferably benzyl alcohol or acetyl acetone and then citrate buffer added in a suitable volume ratio under protection from light, solutions containing 15 to 45 mg of Ixabebipilone are filled in the depyrogenated glass vials, loosely covered with stopper and then subjected to primary and secondary drying during lyophilization step. No detectable drug degradation was observed. The resulting lyophile can be reconstituted with a suitable solution to achieve a final drug concentration of 3mg/ml.

WE CLAIM,
1. A lyophilized Ixabepilone comprising a buffer pH 6 to 7.5 and an organic solvent
in the volume ratio of 70:30 to 50:50 yielding a lyophilized Ixabepilone in an
amorphous form wherein the process for lyophilization further comprises of:
a) dissolving Ixabepilone in an organic solvent and citrate buffer pH 6.2 in the volume ratio of 70:30 to 50:50 to form a solution;
b) subjecting said solution to primary drying in a commercial lyophilizer in a closed system free from light at a temperature from about -80°c to 50°c under vacuum from about 5 millitorr to about 300 millitorr for 24 to 46 hours to form a primary lyophilized product;
c) subjecting the product of step b to secondary drying at temperatures from 10°c to 45°c under vacuum from about 70 millitorr to about 300 millitorr for a period from about 24 hours to about 96 hours to yield lyophilized Ixabepilone in an amorphous form subsequently packed in a vial post-lyophilization, ready for reconstitution prior to parenteral administration.

2. A lyophilized Ixabepilone of claim 1, wherein the buffer used is phosphate buffer or citrate buffer.
3. A lyophilized Ixabepilone of claim 1, wherein the preferred buffer is sodium citrate buffer pH 6.2.

3. A lyophilized Ixabepilone of claim 1, wherein the organic solvent is selected from the group of benzyl alcohol, anhydrous ethanol, isopropyl alcohol, acetyl acetone, etc.
4. A lyophilized Ixabepilone of claim 1, wherein the organic solvent is a pure benzyl alcohol or 50:50 mixture of anhydrous ethanol and benzyl alcohol.

5. A lyophilized Ixabepilone of claim 1, wherein the organic solvent is a 50:50 mixture of anhydrous ethanol and acetyl acetone.