EP1998808A1

EP1998808A1 - Stable pharmaceutical composition of taxanes

Info

Publication number: EP1998808A1
Application number: EP07706195A
Authority: EP
Inventors: Dinesh Kumar; Santosh Kumar Deolia; Rajeev Kumar Yadav; Rajesh Singh Tomar
Original assignee: Dabur Pharma Ltd
Current assignee: Fresenius Kabi Oncology Ltd
Priority date: 2006-02-21
Filing date: 2007-02-07
Publication date: 2008-12-10
Also published as: AU2007219104A1; AU2007219104B2; CA2642324A1; WO2007096900A1; AR059452A1; CA2642324C

Abstract

The present invention discloses a non-ionic solvent having a conductivity value of less than or equal to 5.0 micro semens, which is capable of providing a stabilized pharmaceutical composition comprising a taxane. The present invention relates to a stable pharmaceutical composition of taxanes and a method for preparation thereof.

Description

STABLE PHARMACEUTICAL COMPOSITION OF TAXANES

FIELD OF THE INVENTION

The present invention relates to a stable pharmaceutical composition of taxanes and a method for preparation thereof. In particular, the present invention relates to a stable pharmaceutical composition of Paclitaxel and a method for preparation thereof. The present invention also relates to a non-ionic solvent having a conductivity value of less than or equal to 5.0 micro semens, which is capable of providing a stabilized pharmaceutical composition comprising a taxane and methods for the preparation of such solvents.

BACKGROUND OF THE INVENTION

Taxane derivatives have found wide acceptance for treatment of variety of tumors, especially ovarian cancer, breast cancer, lung cancer, prostate cancer and AIDS related kaposi's sarcoma. Taxanes have also been shown to be effective against other type of cancers, such as melanoma, lymphoma, and those developed in the neck and head. The scientific literature is replete with reports of the efficacy of taxanes in the treatment of variety of unrelated conditions viz. neoplasm in the skin, gastric cancer, polycystic kidney disease etc. Their wide spectrum in vivo activity against malignant tumors has enabled them to be studied as a key therapeutic agent in the treatment of diseases resistant to other anticancer therapies.

Taxane derivatives currently in clinical practice include Paclitaxel (Wani MC, et al., JAm Chem Soc, 1971, 9JL 2325-2327) and Docetaxel (US 4,814,470), which are marketed under the brand name of Taxol^® and Taxotere^® respectively.

A marketed Taxol^® composition is a solution for injection comprising Paclitaxel, cremophor EL and ethanol in a vial, wherein the concentrated solution must be further diluted with normal saline (NS), 5% dextrose in water (D5W) and 5% dextrose in normal saline (D5NS) prior to administration. Similarly a marketed Taxotere^® composition is a solution for injection comprising of Docetaxel and Polysorbate 80. This concentrate is mixed with an initial diluent (13% ethanol in water for injection) supplied in another vial and further diluted with 0.9% sodium chloride or 5% dextrose prior to injection. Surfactants such as cremophor or Polysorbate 80 are included in the said formulations because taxanes are poorly soluble (Paclitaxel has solubility of less than 0.01 mg/ml) in water and other common vehicles used for the parenteral administration of drugs.

Cremophor EL is commercially available polyoxyethylated castor oil supplied by M/s BASF. The use of cremophor EL has distinct advantages such as stimulating haemopoiesis reconstituting capacity in mammals and promotes protection in mammals, subjected to anticancer treatments such as radiation and/or chemotherapy, as described by Bertoncello Ivan in WO 91/02531.

Even though, cremophor EL is not only effective in solubilizing Paclitaxel but also offers a distinct advantage of stimulating haemopoiesis reconstituting capacity, however, its use is associated with certain toxic and hypersensitive reactions, which limits the use of cremophor-paclitaxel formulation in various clinical settings. Further,

Agharkar et al in US 5,504,102 have noted that the cremophor/ethanol formulation of

Paclitaxel precipitates upon dilution with infusion fluid and exhibit a loss of potency of greater than 60% after storage for 12 weeks at 5O⁰C. The loss of potency is attributed to the decomposition of paclitaxel during storage. It was further reported that taxane compositions using crude polyoxyethylated castor oil or Polysorbate as disclosed by

Bastart et al. in US 5,403,858; US 5,698,582 and US 5,714,512 were unstable. In addition to the abovementioned disadvantages, cremophor El has other limitations such as presence of high ionic content, metallic and oxidizing impurities, which further destabilizes the paclitaxel in a pharmaceutical composition thereby rendering it unsafe for patient administration.

From the forgoing, it would be apparent that use of commercially available polyoxyethylated castor oil, in particular Cremophor EL, in a taxane formulation, specifically in a paclitaxel formulation, invariably results in a composition, which does not possess adequate storage stability.

Many attempts have been made to formulate a stable paclitaxel formulation through utilizing either one or both of the following methodologies:

1) addition of an acid and/or their metal salts, chelators, stabilizers and/or antioxidants into the formulation; or 2) purification of polyoxyethylated castor oil, in particular Cremophor EL, prior to utilization into the formulation To name a few; a) Agharkar et al in US 5,504,102 disclose addition of an acid, particularly a mineral acid such as HCl, HBr, HI, HF, H₂SO_4> HNO₃₁ or acetic acid to a pharmaceutical composition of paclitaxel in polyethoxylated castor oil.

When such acids are employed in preparation of a pharmaceutical composition, the final pH of the formulation goes invariably to an acidic range, which in turn could cause administration site reactions, thereby further causing patient discomfort. Prescribing information of Taxol^®, which has pH in the acidic range, indicates that the said formulation causes injection site reactions in approximately 13% of patients and includes erythema, tenderness, skin discoloration, or swelling at the injection site. Secondly, the aforementioned methods wherein an acid is added, further has the limitation that pH of the formulation needs to be maintained constantly within a range of 4-6. Deviation of pH to higher (alkaline) values, results in degradation of the taxane composition. Thus it provides only a narrow pH range to work on. b) Carver et al in 5,733,888; 5,972,992; 5,977,164; and 6,140,359 again disclose addition of an acid, specifically organic and mineral acids, to a pharmaceutical composition of paclitaxel in cremophor to maintain the pH within the range of 5 to 7. Acids in the form of powders, for example citric acids, are disclosed as most preferred than those which contain water for example sulfuric acid. However, again, eventhough, the preferred acids are in powder form, the pharmaceutical composition of paclitaxel containing an acid suffers from the abovementioned limitation that, the pH of such compositions invariably goes to an acidic range, which has potential to cause injection site reactions and thereby patient discomfort, and further it leaves a very narrow pH range to experiment. c) Zhang et al in WO 2001/072300 disclose a taxane formulation in polyethoxylated castor oil, which is stabilized by addition of a metal salt of an acid. Preferred acids are gluconic acid, amino acid, ascorbic acid, pamitic acid, citric acid, an alpha or beta hydroxy acid, sulfuric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, hydrofluoric acid, alpha-hydroxy methyl sulfinic acid, benzoic acid, sulfonic acid, and the metal salt is iron, copper, zinc, magnesium, calcium, manganese, aluminum, tin, platinum etc. It is further disclosed that such metal salts stabilize the taxane composition by inhibiting the solvolysis of the ester side chain at C- 13, deacetylation at C-IO and epimerization at C-7. Addition of a metal salt of an acid not only raises concerns regarding acceptability of such composition by Health Authorities all over the world, but also suffers from the abovementioned limitation of unwanted injection site reactions and narrower range of pH to experiment upon. d) Han et al. in US 6,090,844 disclose addition of calcium disodium edetate and tromethamine to a composition of paclitaxel in polyepoxilated castor oil and anhydrous alcohol has the ability to reduce side effects, which are normally associated with Taxol^® formulation. e) Lee et al. in US 2005/026995 disclose addition of a stabilizer such as N-acetyl amino acid stabilizes injectable composition of paclitaxel in polyoxyl hydrogenated castor oil and alcohol. f) Owens et al in US 6,071,952 and 6,153,644 disclose treatment of cremophor with an anti-oxidant such as citric acid to achieve a stable taxane composition. It is further disclosed that addition of antioxidants to a pharmaceutical composition inhibits degradation of taxanes by reducing the oxidizing agents present in the solubilizng and dispersing agent.

However, it might be mentioned that Health Authorities all over the world are very concerned about the level of extraneous agent such as stabilizing agents, chelating agents, preservatives and antioxidants utilized in preparation of pharmaceutical compositions. As a consequence, regulatory approval norms today are very stringent about the nature and level of extraneous agents present in a drug product. In view of this, the range or freedom available to experiment with various extraneous agents is minimum. Presence of any unapproved agent in the pharmaceutical composition renders such formulation unacceptable to Health Authorities, even though, such solutions may be stable. g) Further, Agharkar et al in US 5,504,102 disclose purification of cremophor so as to have a reduced carboxylate anion content. The carboxylate anion content is lowered by either contacting the cremophor El with an aluminum oxide bed to separate the carboxylate anions as well as other impurities or by the addition of an acid, particularly a mineral acid such as hydrochloric acid or nitric acid to the formulation.

However, adsorbents, such as aluminum oxide, when used for purification of cremophor require critical monitoring for their presence in the final preparation. Theses adsorbing agents, if present, even in traces, may have detrimental effect rendering such formulations highly toxic for human administration. Thus, use of these adsorbing agents calls for use of specific filters or purification process, which not only makes the entire process complex but also costly. Moreover, needless to mention, this would increase the cost of manufacturing. h) Kysilka et al in US 2005/0142225, disclose use of a silica gel column to reduce the content of acidic and basic compounds present in polyoxyethylated castor oil for producing a stable taxane composition. i) Further, in US 6,096,911, Dralle-Voss et al disclose a process for purification of cremophor by treating it with a mixture of adsorbents such as aluminium oxide and silicate. j) Anevski et al. in US 6,388,112 disclose yet another method for purification of cremophor which involves use of an activated carbon and an ion exchange resin column for reducing the amount of salts, acids and various other ionic impurities present in cremophor. However, as in the case of aluminium oxide, use of carbon, aluminium oxide, silicate and silica gel as adsorbents for purification of cremophor requires critical monitoring for their presence in the final preparation, since, even traces of theses adsorbing agents have detrimental effects rendering such formulations highly toxic for human administration. k) Nikolayev et al in US 5,925,776 disclose that a stable paclitaxel formulation could be achieved by purifying the cremophor by treatment with a strong cationic exchange resin, which helps in removing a substantial portion of the cations present in a crude polyethoxylated castor oil.

1) Burman et al in US 2005/0016926, disclose use of reverse-phase chromatography to reduce the ionic, metallic and oxidizing impurities content of the cremophor. m) Furthermore, James et al in NL 95/00340 disclose a stabilized, pharmaceutically acceptable composition of Paclitaxel and disclose that pre-treatment of the surfactant with a molecular sieve material preferably a porous aluminium oxide that allows a paclitaxel solution having long-term stability to be formed. Utilization of ionic exchange resin, chromatographic columns or reverse phase column chromatographic technique for the purification of cremophor requires judicious selection of solvent systems, resins and columns. Moreover, such selection is not easy because it requires some technical skill and manual dexterity for proper setting and running of the column. Moreover, efficiency of such chromatographic techniques is dependent on vagaries of critical parameters like column packing, particle size of material used for column packing, solvent systems used during the process etc. Furthermore, running a column is time-consuming and tedious, especially for large samples. This makes the entire purification process not only cumbersome involving an extra step in the formulation, but also costly rendering such methods mainly of academic interest. Because of the abovementioned associated limitations, the use of such techniques raises concerns in the mind of a manufacturer regarding the commercial viability of such methods. n) Joshi-Hangal et al in US 6,710,195 disclose that ageing of Cremophor by exposing it to a gaseous atmosphere such as oxygen for a certain period of time leads to a stable pharmaceutical composition of paclitaxel. This patent further discloses that ageing could also be performed by heating the cremophor to a stated temperature or by applying a defined pressure. Such pre-treated cremophor has been claimed to produce a stabilized paclitaxel composition. However, the ageing process, as disclosed, is carried out for at least 3 days and optionally for at least 14 days at a temperature range of 30 ⁰C to 70 ⁰C and by pressurizing polyoxyethylated castor oil to be at least 1.2 to 3.0 atmospheric pressure, is highly time consuming, costly, and inconvenient thereby rendering it commercially unviable. o) Kang Hoon Seok et al in KR 2000061111 disclose a pharmaceutical composition of paclitaxel injection comprising ethyl acetate fractional extract of cremophor, povidone, polyethylene glycol and assistant emulsifier. The KR 2000061111, further, discloses that when only ethyl acetate fractional extract of cremophor is utilized in preparation of paclitaxel injection, it showed inferior stability than that of a marketed formulation. In order to improve the stability, use of various vegetable oils or polyethylene glycol ester of mixed fatty acids originated from vegetable oil as assistant solubilizer is recommended.

Again, the disclosed method suffers from the limitation that the desired stability is achieved in this method only by addition of various vegetable oils or polyethylene glycol ester of mixed fatty acids originated from vegetable oil as assistant solubilizer. Additions of such extraneous additives are frowned upon by Health Authorities, rendering such compositions unacceptable.

From the foregoing disclosures, it would be abundantly evident that a stabilized formulation of paclitaxel is obtained either by addition of an extraneous agent such as acidifying, chelating, solubilizing or stabilizing agents into the pharmaceutical composition of paclitaxel in alcohol and cremophor EL or by utilization of a purified cremophor.

However, all the prior art disclosures invariably suffer from one or more of the aforementioned limitations rendering such methods uneconomical, inconvenient, tedious, unpleasant to patients, and not particularly acceptable to Health Authorities.

A great need, if not imperative, therefore, exists for a pharmaceutical composition of taxanes, which is not only patient friendly, acceptable to Health

Authorities, but also is manufactured by a method which is simple, convenient, economical and more importantly is free from the limitations associated with the prior art method.

The present invention is a step forward in this direction in providing a novel, simple and economical method for a stable taxane composition. OBJECTS OF THE INVENTION An object of the present invention is to provide a stabilized taxane composition suitable for parenteral administration.

Another object of the present invention is to provide a stabilized taxane composition suitable for parenteral administration, which avoids addition of any extraneous agents such as stabilizing agents, chelating agents, acidifying agents and co- solubilizing agents for stabilizing taxane formulation.

Still another object of the present invention is to provide a stabilized taxane composition suitable for parenteral administration, which utilizes non-ionic solvents, purified by a method, which is simple, convenient, economical and patient friendly.

Yet another object of the present invention is to provide a stabilized taxane composition suitable for parenteral administration, which utilizes non-ionic solvents purified by a method free from the limitations associated with the prior art methods.

A further object of the present invention is to provide a stabilized paclitaxel composition suitable for parenteral administration.

A still further object of the present invention is to provide a stabilized paclitaxel composition suitable for parenteral administration, which avoids addition of any extraneous agents such as stabilizing agents, chelating agents, acidifying agents and co- solubilizing agents for stabilizing the paclitaxel formulation. Yet further object of the present invention is to provide a stabilized paclitaxel composition suitable for parenteral administration, which utilizes non-ionic solvents, purified by a method, which is simple, convenient, economical and patient friendly.

Still another object of the present invention is to provide a stabilized paclitaxel composition suitable for parenteral administration, which utilizes non-ionic solvents purified by a method free from the limitations associated with the prior art methods.

Yet another object of the present invention is to provide a simple, convenient and economical method for purification of non-ionic solvents, which renders such non- ionic solvents suitable for utilization in manufacture of a stable pharmaceutical composition of taxanes .

Yet further object of the present invention is to provide a method for purification of non-ionic solvents, which is free from the limitations associated with the prior art methods.

Still further object of the present invention is to provide a method for treatment of cancer comprising administration of such stable formulation of taxane to the human or animal in need of such treatment. SUMMARY OF THE INVENTION

In their endeavor to prepare a stable Paclitaxel formulation, the present inventors have come up with a simple, economical and convenient method for purifying non-ionic solvents, circumventing most of the limitations of the approaches hitherto practiced.

In particular, the present invention is directed to purification of non-ionic solvents suitable for preparation of stabilized injection compositions containing at least a taxane. Accordingly, it is a primary aspect of the present invention to provide a method for preparing a purified non-ionic solvent, which when used in a taxane composition has a stabilizing effect on such composition. The present invention also provides a method for preparation of a stabilized pharmaceutical composition using such purified non-ionic solvents. The stabilized pharmaceutical compositions produced using the purified non- ionic solvent of the present invention have been shown to have a shelf life greater than the compositions produced from untreated/unpurified non-ionic solvents.

Further, the present inventors have found that such a purification of non-ionic solvents could be achieved by selectively extracting the said solvent in an organic solvent system, which is water-immiscible. Solvent extraction technique could be used as a selective separation procedure for isolating and concentrating a valuable, non- ionic, non-polar solvent from impurities present therein, with the aid of a two layer solvent system having an aqueous or polar phase and a non-aqueous or non-polar water-immiscible organic phase.

The purification of non-ionic solvents by the method of the present invention utilizing an aqueous and a water-immiscible organic solvent phases, involves no critical process steps, and no particular significance need to be given for pH modification of the final formulation, for obtaining a stabilized formulation of taxanes. In particular, it has been found that a stable formulation of paclitaxel can be obtained by utilization of a simple purification technique of cremophor as disclosed herein and utilizing such purified cremophor for preparation of paclitaxel composition, involving neither addition of any extraneous agent such as stabilizing agent, chelating agent, oxidizing agent, preservatives nor adjustment of pH with a pharmaceutically acceptable pH modifier.

In a typical method, the commercially available non-ionic solvent is dissolved in a water- immiscible organic solvent, which is then washed with fractions of more polar, aqueous solvent. The two liquid phases are then allowed to separate. The addition of an aqueous phase to an organic phase containing non-ionic solvent, selectively removes all impurities leaving behind the pure solvent in the organic phase.

The removal of impurities is evident by observed change in the pH and conductivity values of the two liquid phases. Reduced conductivity of the non-ionic solvent is a clear indication of selective removal of all the ionic, polar impurities from the solvent by aqueous phase. Conductivity value of the purified cremophor drops to a value of below 5.0 from an initial conductivity value of about 5.5 to 7.5 observed with commercially available cremophor.

While, the selective method of the present invention for purification non-ionic solvents, alone, is adequate to render it suitable in providing a stable taxane formulation, however, the method can also, if required, be used in conjunction with other methods known in the art.

As a point of illustration, a comparison of the stability profile of paclitaxel formulations viz., a formulation prepared using cremophor purified by the method of the present invention and a formulation prepared by using the commercially available cremophor is summarized in table —I. The stability of the two formulations is determined on the basis of the levels of formation of degradation products, as mentioned in an Official Monograph of Paclitaxel in the Unites States Pharmacopoeia.

TABLE -I

Comparative Degradation of A Paclitaxel Formulation Utilizing Commercially

Available Cremophor and That Utilizing Cremophor Purified by the Method of the

Present Invention, when Stored at 50⁰C For 10 Days

* - Solution in ethanol and cremophor

# - Prescribed in the official monograph of Paclitaxel in the United States Pharmacopoeia. 10-DAP - ( 10-deacetyl paclitaxel)

10-DA - 7-epi-T (lO-deacetyl-7-epi-paclitaxel) 7-epi-T - 7-epi-paclitaxel (7-epi-T) ND - Not detected

The degradation products of paclitaxel include Baccatin II, ethyl ester side chain of paclitaxel, 10-deacetyl paclitaxel (DAP), lO-deacetyl-7-epi-paclitaxel (10-DA-7epi- T) and 7-epi-paclitaxel (7-epi-T). From Table -I, it would be abundantly evident that the formulation of paclitaxel prepared by using cremophor purified by the method of the present invention shows highly superior stability profile in terms of degradation products. Thus, in essence the present invention provides a simple, convenient, less time consuming and economical process for purification of cremophor. Further this invention provides a pharmaceutical composition of paclitaxel prepared using such purified cremophor. This forms the basis of the present invention. Thus, in accordance with the above: In one aspect the present invention provides a stabilized taxane composition, particularly a stabilized paclitaxel composition suitable for parenteral administration. In another aspect, the present invention provides a stabilized taxane composition suitable for parenteral administration, which avoids addition of any extraneous agents such as stabilizing agents, chelating agents, acidifying agents and co-solubilizing agents for stabilizing taxane formulation. , In yet another aspect, the present invention provides a stabilized taxane composition suitable for parenteral administration, which utilizes non-ionic solvents, purified by a simple, convenient and economical method, comprising the steps of: a) dissolving the non-ionic solvent in an water-immiscible organic solvent; b) adding an aqueous solvent to the solution of step (a) to form a biphasic system; c) extracting/ selectively partitioning the non-ionic solvent into the organic phase; d) allowing the two immiscible phases to stand; e) separating the aqueous and organic phases; f) optionally, washing the organic phase with the aqueous solvent once more or twice; g) optionally, extracting the combined aqueous phase of step (e) and (f) with the water-immiscible organic solvent; h) combining all the water-immiscible organic phases of steps (e), (f) and (g); and i) evaporating the organic solvent to obtain the purified non-ionic solvent, having a conductivity of below 5.0. In still another aspect, the present invention provides a stabilized paclitaxel composition suitable for parenteral administration, which avoids addition of any extraneous agents such as stabilizing agents, chelating agents, acidifying agents and co- solubilizing agents for stabilizing the paclitaxel formulation.

In still further aspect, the present invention provides a stabilized paclitaxel composition suitable for parenteral administration, which utilizes non-ionic solvents, purified by a simple, convenient, economical and patient friendly method, comprising the steps of: a) dissolving the non-ionic solvent in an water-immiscible organic solvent; b) adding an aqueous solvent to the solution of step (a) to form a biphasic system; c) extracting/ selectively partitioning the non-ionic solvent into the organic phase; d) allowing the two immiscible phases to stand; e) separating the aqueous and organic phases; f) optionally, washing the organic phase with the aqueous solvent once more or twice; g) optionally, extracting the combined aqueous phase of step (e) and (f) with the water-immiscible organic solvent; h) combining all the water-immiscible organic phases of steps (e), (f) and (g); and i) evaporating the organic solvent to obtain the purified non-ionic solvent, having a conductivity of below 5.0.

In yet further aspect, the present invention provides a method for selectively removing the impurities from non-ionic solvents.

In still another aspect, the present invention provides a method to obtain a purified non-ionic solvent system, which has a conductivity value of less than or equal to 5.0.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is primarily directed to a method of purification of non- ionic solvents and their utilization in preparation of a stabilized pharmaceutical composition of taxanes. In particular, as mentioned hereinbefore, . the present invention is directed towards a solvent extraction process comprising two immiscible liquid phases; an aqueous solvent and a water-immiscible organic solvent, which selectively removes the impurities from the non-ionic solvents and results in purified non-ionic solvent, which has reduced conductivity. As used herein, the term "non-ionic solvent" refers to a condensation product of an alkylene oxide and a lipid or fatty acid. The preferred non-ionic solvent includes a polyoxyethylated castor oil such as that sold by M/s BASF under the trade name Cremophor EL^® or Cremophor ELP^®.

As used herein, the term "water-immiscible organic solvent" refers to an organic solvent, which is immiscible with water. Examples of such water-immiscible solvents are, but not limited to, halogentated hydrocarbon solvents such as

Dichloromethane, Carbon tetrachloride, Chloroform, 1,2-dichloroethane, lower chlorinated alkanes containing 1 to 4 carbon atoms etc. and non-halogenated hydrocarbon solvents such as cyclohexane, n-hexane, n-heptane etc. Amongst the hydrocarbon solvents, the halogenated hydrocarbon solvents are more preferred and amongst the halogenated hydrocarbon solvents, Dichloromethane is highly preferred.

As used herein, the term "aqueous solvent' refers to water containing solvents. Water is a preferred solvent, whereas de-ionized water is more preferred and Milli-Q water of HPLC grade is highly preferred aqueous solvent. As used herein, the term "conductivity" refers to the ability of a solvent to conduct electric current. Since the charge on ions in solution facilitates the conductance of electrical current, the conductivity of a solution is proportional to its ionic concentration. Even though, the conductivity is roughly proportional to the concentration of ions in solution, but all ions do not conduct equally. Ions that move through solution easily conduct better. For example, small, fast moving ions like hydrogen ion (H⁺ ) impart greater conductivity to solutions than do bulky ions like bromide ion (Br ^" ), or heavily hydrated ions like sulfate ion (SO₄ ^2" ). If an aqueous solution conducts electricity, then it must contain ions. However, any solution, even one containing ions, provides considerable resistance to the flow of current through it. Conductivity, thus, is reciprocal of this resistance of the solution.

The principle by which instruments measure conductivity is simple. Two plates or electrodes are placed in the sample, and a constant voltage is applied across the plates, and the current is measured. Conductivity (G), the inverse of resistivity (R), is determined from the voltage and current values according to Ohm's law.

1 I (amps) R E (volts)

Normally, after purifying the crude cremophor by the method described in the present invention, a solution of cremophor in water is prepared. Normally, the ratio of cremophor to water is 10:1 w/w. then the two electrodes are placed in the sample and current flowing through the sample is measured. Normally, at least 25% drop in conductivity is observed. However, it should be noted that conductivity capacity of the commercially available non-ionic solvents, particularly, cremophor, increases on storage. The commercially available cremophor has a conductivity value of at least 5.5, normally in the range of 5.5 to 7.5, which could further increase depending on the storage duration. It was found that, the cremophor purified by the method of the present invention, has a conductivity value of less than or equal to 5 micro Semens.

Further it was found that, cremophor purified by the method of the present invention, and which has a conductivity value of below 5.0 produces a stable pharmaceutical composition of paclitaxel. The purified cremophor having a conductivity value in the range of 2.0 to 3.5 are preferred and those having a conductivity values below 2.5 are highly preferred for preparation of a stable pharmaceutical composition of paclitaxel. The process employed for the purification of non-ionic solvents, liquid-liquid extraction process, is carried out according to the well-established protocols of liquid extractions. However, standard deviation form this procedure, further enhancing efficiency of liquid-liquid extraction method are possible and therefore, the procedural steps should be not construed as limiting the scope of the invention.

In a typical method, the non-ionic solvent is first dissolved in a water- immiscible organic solvent. In a preferred embodiment, both, the non-ionic solvent and water-immiscible organic solvent are used in 1:1 ratio. Suitable methods to enhance the dissolution rate such as mixing could be employed to get a uniform solution. Aqueous solvent, preferably Milli-Q water is added to the above uniform solution to form a biphasic system. It is highly preferred to add the aqueous solvent in 1: 1 ratio of water- immiscible organic solvent. Further, stirring or agitation could be employed to effect the extraction of non-ionic solvent in two immiscible liquid phases. Preferably, a continuous stirring with the help of mechanical stirrer for about 2 to 30 minutes with 10 to 250 rpm is employed to perform the extraction. Then the biphasic mixture is allowed to stand for phase separation. Preferably, 12 hrs or more are required to have a clear phase separation at room temperature, when a biphasic system using dichloromethane as water-immiscible organic solvent and Milli-Q water as aqueous solvent is utilized in purification of commercially available cremophor. The two different layers of water- immiscible organic solvent and aqueous solvent are separated. Optionally, the organic phase is further washed with equal volumes of aqueous solvent once more or twice. Similarly, the combined aqueous phases obtained during the abovementioned process, could further be extracted with equal volumes of water-immiscible organic solvent. Then, all the fractions of water-immiscible organic phases are combined and the organic solvent is evaporated to obtain the purified non-ionic solvent, having a conductivity of below 5.0. The obtained, purified non-ionic solvent is further dried under vacuum at temperature of about 50 ⁰C to remove residual organic solvents and moisture to obtain a dried, purified non-ionic solvent.

In a preferred embodiment the weight ratio of non-ionic solvent to organic phase is 1 :1 and it is further highly preferred that both the liquid phases viz., the aqueous phase and immiscible organic phase are used in 1:1 ratio.

As mentioned hereinbefore, the method of the present invention reduces the conductivity of the commercially available cremophor to a value of below 5.0 from an intial value of 5.5 to 7.5, thereby rendering it suitable for preparation of a pharmaceutical composition of paclitaxel.

Thus, the present invention also provides a pharmaceutically stable formulation of paclitaxel made using a purified non-ionic solvent and alcohol. The stabilized pharmaceutical composition of paclitaxel produced using the non-ionic solvent purified by the method of the present invention has been shown to have a shelf life greater than the compositions produced from commercially available non-ionic solvent.

The stabilized formulation of paclitaxel includes an alcohol, which may be added to the non-ionic solvent before or after combining the said solvent with paclitaxel. The alcohol may be a dehydrated alcohol. Compositions suitable for parenteral administration such as injection or infusion may be prepared by diluting the compositions with a suitable parenteral fluid prior to parenteral administration, injection or infusion.

In a typical pharmaceutical composition, each ml contains 6 mg of paclitaxel, and 527 mg of purified cremophor and 49-50% v/v dehydrated alcohol.

Furthermore, other than purification of non-ionic solvent by solvent extraction method, as described hereinbefore, no other unit operation or additive is required, and no particular significance need to be given for pH modification of the final formulation, for obtaining a stabilized formulation of paclitaxel. Further, neither addition of any extraneous agent such as stabilizing agent, chelating agent, oxidizing agent, preservatives nor adjustment of pH with a pharmaceutically acceptable pH modifier is required to get a stabilized pharmaceutical composition of paclitaxel.

The following non-limiting example is intended to demonstrate the preferred embodiment of the invention. One skilled in the art will readily recognize that numerous embodiments of the invention can be practiced to achieve the stabilizing effect. Example -1:

This example was carried out to determine the effect of purification method of the present invention on physicochemical properties of cremophor.

500 g of commercially available Cremophor was dissolved in 500 ml of dichloromethane in a glass container. Stirring was employed to get a uniform solution of cremophor. The solution was transferred to a separating funnel. To this solution 500 ml of de-ionized water is added. The two liquids were thoroughly mixed with the help of a mechanical stirrer for about 30 minutes with 250 rpm and then solution was allowed to stand in order to have separation of the two liquid phases. Lower layer of dichloromethane was separated. The separated organic layer was further washed with 500 ml of water. The two separated water layers were combined and washed with two fractions of 500 ml of dichloromethane. The separated organic layers were combined and organic solvent was evaporated. The obtained cremophor was further dried under vacuum at temperature of about 50 ⁰C to get the pure and dry cremophor. The obtained pure cremophor is then further subjected to various chemical tests. A comparative analysis of the obtained properties of purified cremophor with that of commercially available cremophor is presented in Table- II.

TABLE - II

Comparative Physico-Chemical Properties Of The Commercially Available Cremophor With That PvrifiedBy The Method Of The Present Invention

It would be evident form Table- II that purified cremophor has essentially similar results for Iodine Value, Hydroxyl value, Saponification value, Heavy metal and specific gravity. However, major changes are observed after purification of cremophor in the values of pH and conductivity.

After purification by the method of the present invention, as described herein before, impurities from non-ionic solvents are removed by aqueous solvent, because of which the pH of purified cremophor shows shift towards acidic range. After purification by current method, the cremophor shows a pH value in the range of 4.0 to

6.0.

Another parameter, which shows major change, is conductivity. The conductivity was measured with a conductivity meter of Ecoscan (CON-5). The two electrodes are immersed in the non-ionic solvent and a constant voltage is applied to two electrodes and the resulting current is measured.

Example -2:

Paclitaxel formulation was prepared by dissolving paclitaxel to get a final concentration of 6 mg/ml in 50:50 v/v mixture of cremophor purified by the method of the present invention and absolute ethanol. A paclitaxel formulation was also prepared similarly, to serve as a control by utilizing commercially available Cremophor and ethanol. Each ml of the prepared formulations contains 6 mg of paclitaxel, and 527 mg of either purified cremophor or commercially available cremophor.

Both the pharmaceutical composition samples were then subjected to a stability evaluation under accelerated temperature conditions. All the samples were preserved at

50 ⁰C. The stability profile shown by each foπnulation is summarized in Table - 1.

The foregoing description of the preferred embodiment of the invention has been presented for purpose of illustration and description. It is not intended to be exhaustive or to limit the invention to precise parameters disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiment has been chosen and described to provide the best illustration of the principles of the invention and its practical applications to thereby enable one of the ordinary skill in the art to utilize the invention in various embodiments and with various modifications. All such modifications and variations are within the scope of the invention as determined by the appended claims.

Claims

We claim:

1. A non-ionic solvent having a conductivity value of less than or equal to 5.0 micro semens, which is capable of providing a stabilized pharmaceutical composition comprising a taxane.

2. A non-ionic solvent having a conductivity value in the range of 2.0 to 3.5 micro semens, which is capable of providing a stabilized pharmaceutical composition comprising a taxane.

3. A non-ionic solvent according to any one of claims 1 and 2, wherein the non- ionic solvent is polyethoxylated castor oil or polyoxyl-35 -castor oil.

4. A stabilized pharmaceutical composition comprising a taxane and a non-ionic solvent having a conductivity value of less than or equal to 5.0 micro semens. 5. A stabilized pharmaceutical composition as claimed in claim 4 wherein said non-ionic solvent having a conductivity value in the range of 2.0 to 3.

5 micro semens.

6. A stabilized pharmaceutical composition as claimed in claim 4 or 5 wherein said non-ionic solvent is polyethoxylated castor oil or polyoxyl-35 -castor oil.

7. A stabilized pharmaceutical composition as claimed in any one of claims 4 to 6, wherein the taxane is paclitaxel.

8. A stabilized pharmaceutical composition as claimed in any one of claims 4 to 7 wherein the composition further comprises of alcohol.

9. A stabilized pharmaceutical composition according to claim 8, wherein the proportion of non-ionic solvent and alcohol is 1:1 v/v.

10. A process for preparation of a non-ionic solvent capable of providing a stabilized taxane pharmaceutical composition comprising the steps of: a) dissolving the non-ionic solvent in an water-immiscible organic solvent; b) adding an aqueous solvent to the solution of step (a) to form a biphasic system; c) extracting the non-ionic solvent into the organic phase; d) allowing the two immiscible phases to stand; e) separating the aqueous and organic phases; f) optionally, washing the organic phase with the aqueous solvent once more or twice; g) optionally, extracting the combined aqueous phase of step (e) and (f) with the water-immiscible organic solvent; h) combining all the water-immiscible organic phases of steps (e), (f) and

(g); and i) evaporating the organic solvent to obtain the non-ionic solvent.

11. A process for the preparation of a non-ionic solvent having conductivity value of less than equal to 5.0, which is capable of providing a stabilized taxane pharmaceutical composition comprising the steps of: a) dissolving the non-ionic solvent in an water-immiscible organic solvent; b) adding an aqueous solvent to the solution of step (a) to form a biphasic system; c) extracting the non-ionic solvent into the organic phase; d) allowing the two immiscible phases to stand; e) separating the aqueous and organic phases; f) optionally, washing the organic phase with the aqueous solvent once more or twice; g) optionally, extracting the combined aqueous phase of step (e) and (f) with the water-immiscible organic solvent; h) combining all the water-immiscible organic phases of steps (e), (f) and

(g); and i) evaporating the organic solvent to obtain the non-ionic solvent.

12. The process as claimed in claim 10 or 11 wherein the water-immiscible organic solvent is a non-halogenated hydrocarbon or a halogenated hydrocarbon.

13. The process according to claim 12, wherein the non-halogenated hydrocarbon is cyclohexane, n-hexane or n-heptane.

14. The process according to claim 12, wherein the halogenated hydrocarbon is dichloromethane, carbon tetrachloride, chloroform or 1,2-dichlorethane.

15. The process as claimed in any one of claims 10 to 14, wherein the water- immiscible organic solvent is dichloromethane.

16. The process as claimed in any one of claims 10 to 15, wherein the aqueous solvent is water or Milli-Q water.10 to 16, wherein the non-ionic solvent is polyethoxylated castor oil or polyoxyl-35-castor oil.

17. The process as claimed in any one of claims 10 to 15 wherein the non-ionic solvent is cremophor.

18. The process as claimed in any one of claims 10 to 15, wherein the proportion of non-ionic solvent to water-immiscible organic solvent is 1 :1.

19. The process as claimed in any one of claims 10 to 18 wherein the proportion of water-immiscible organic solvent and aqueous solvent is 1 :1.

20. The non-ionic solvent obtained by the process as claimed in any one of claims 10 to 19.