PEMETREXED DIPOTASSIUM FORMULATIONS

Aspects of the present invention relates to pharmaceutical composition comprising crystalline pemetrexed dipotassium hydrate and process for preparation thereof.

INTRODUCTION

The chemical name of Pemetrexed is (S)-2-(4-(2-(2-amino-4-oxo-4,7-dihydro-3H-pyrrolo[2,3- d]pyrimidin-5-yl)ethyl)benzamido)pentanedioic acid and has the following chemical structure:

Pemetrexed disodium is the most common salt of pemetrexed di acid. Pemetrexed disodium heptahydrate is the active ingredient of Eli Lilly and Company's ALIMTA® injectable composition. Pemetrexed disodium heptahydrate has the following chemical structure:

Pemetrexed disodium is a multi-targeted antifolate that strongly inhibits various folate- dependent enzymes, including thymidylate synthase (TS), dihydrofolate reductase (DHFR) and glycinamide ribonucleotide formyltransferase (GARFT). Pemetrexed disodium has been proved effective on a wide variety of solid tumors in clinical trials. Currently, pemetrexed disodium is commercial available in USA, European Union, Canada, Japan and China etc. for treatment of malignant pleural stromal tumor as a first-line drug, and local advanced and metastatic non-small cell lung cancer as a second-line drug. In the treatment of malignant pleural stromal tumor, pemetrexed disodium is a unique chemotherapeutic agent in the market currently. In the second-line treatment of non-small cell lung cancer, pemetrexed disodium has a comparative efficacy and reduced toxicities compared with the standard drug Docetaxel. Hence, it is more likely for pemetrexed disodium to become a new standard treatment of the second-line treatment for non-small cell lung cancer. In addition, the clinical studies of pemetrexed disodium in the treatment of breast, bowel, pancreatic, head and neck, gastric and bladder cancers are still ongoing.

Riebesehl et al in US6,686,365 provides a pharmaceutical composition comprising pemetrexed, at least one antioxidant selected from the group consisting of monothioglycerol, L-cysteine, and thioglycolic acid, and a pharmaceutically acceptable excipient.

WO2008/021411A2 provide processes for the preparation of lyophilized pharmaceutically acceptable salts of pemetrexed diacid, in particular, pemetrexed disodium salt, directly from pemetrexed diacid or salts thereof, i.e., without isolating the obtained pemetrexed salt prior to lyophilizing it.

WO2010/030598 A2 application describes Pharmaceutical formulations comprising amorphous pemetrexed or its salts, and processes to prepare the formulations.

WO2012/015810 A2 discloses long term storage stable pemetrexed-containing liquid pharmaceutical compositions. The compositions can include pemetrexed or pharmaceutically acceptable salts thereof; an antioxidant selected from lipoic acid, dihydrolipoic acid, methionine and mixtures thereof; a chelating agent selected from lactobionic acid, sodium citrate, tribasic and mixtures thereof; and a pharmaceutically acceptable fluid. The pH of the compositions is in a range of about 8 to about 9.5 and total impurities in the range of less than about 5%.

CN 101081301 Al discloses medicine composition containing pemetrexed, at least one kind of antioxidant as additive selected from L-arginine, L-glutathione, L-methionine and L- tryptophan, and pharmaceutically acceptable excipient.

CN 1907284 Al discloses a pharmaceutical composition comprising pemetrexed, characterized in that to contain pemetrexed and stabilizer in composition, its weight ratio is Chelius et al in US7,138,521 describes a stable crystalline heptahydrate form of pemetrexed disodium salt. The patent states that pemetrexed can exist in the form of a heptahydrate which is more stable than the previously known 2.5 hydrate and shows that the primary advantage of the heptahydrate crystalline form over the 2.5 hydrate crystal form is its stability and also with respect to formation of related substances. It also shows that when the heptahydrate is subjected to elevated temperatures, low humidity, and/or vacuum, it is converted to the 2.5 hydrate (hemi-pentahydrate) crystal form by loss of water.

US 8,088,919 provide crystalline forms of pemetrexed diacid, and processes for the preparation thereof.

Abovementioned disclosures related to formulation of pemetrexed are known to be with either pemetrexed di sodium salt or its diacid (often referred as pemetrexed). Being pemetrexed as an important anticancer therapeutic agent, additional and improved ways of utilizing pemetrexed different salt/s may be of immense value to pharmaceutical science and the healthcare of cancer patients. Hence, there exists an apparent need in the development of new salt formulation and its process/es, which may be stable, commercially viable, safer for patient health, and with better and consistent quality parameters.

The present inventors have found a stable formulation of new salt form of pemetrexed diacid as Pemetrexed dipotassium hemiheptahydrate, which is stable and usable for intended therapeutic purposes.

SUMMARY OF INVENTION

Particular aspects of the present application relates to pharmaceutical composition comprising pemetrexed dipotassium and its hydrates and process for preparation thereof.

In one aspect of the present invention, it relates to a pharmaceutical composition comprising pemetrexed di potassium hemiheptahydrate characterized by X-ray powder diffraction pattern containing at least 5 characteristic 29° diffraction angle peaks selected from the XRPD peak set of 5.00, 13.70, 16.90, 20.00, 21.40, 23.6, 24.2 and 28.30 ± 0.20 2Θ°, and a pharmaceutically acceptable amount of an excipient, wherein said composition is having moisture content less than 5% w/w.

In one aspect of the present invention, it relates to a lyophilized composition of pemetrexed di potassium hemiheptahydrate, wherein the composition is characterized by X-ray powder diffraction pattern containing at least 5 characteristic 29° diffraction angle peaks selected from the XRPD peak set of 4.03, 4.26, 5.28, 11.53, 18.83, 21.76, 22.16, 24.75, 25.36, 25.98, 26.60, 27.92, 28.25, 31.78, 32.76, 34.38, 34.98, 38.78, 44.14 and 47.23 ± 0.2° 2Θ.

In particular, the invention further relates to pharmaceutical composition comprising pemetrexed di potassium hemiheptahydrate and a pharmaceutically acceptable amount of an excipient effective to form a lyophilized cake. For example, the lyophilized preparations of the invention may contain one or more Cryoprotectants or a combination thereof.

Among further aspects, the invention relates to pharmaceutical composition comprising pemetrexed di potassium hemiheptahydrate, wherein a moisture content of the formulation is preferably less than about 5% by weight.

The present invention also relates to pharmaceutical composition comprising about lOmg/ml to about lOOmg/ml of pemetrexed di potassium hemiheptahydrate calculated as pemetrexed; excipients comprising about lOmg/ml to about 200mg/ml of the excipient, wherein the excipient comprising at least one Cryoprotectant, and a solvent selected from water, DMSO, ethanol and acetonitrile.

The present invention also relates to pharmaceutical composition comprising about lOmg/ml to about lOOmg/ml of pemetrexed di potassium hemiheptahydrate calculated as pemetrexed; excipients comprising about lOmg/ml to about 200mg/ml of the excipient, wherein the excipient comprising at least one Cryoprotectant, and water.

In another aspect of the present invention, it relates to a process for preparing a pharmaceutical composition containing a pemetrexed dipotassium hydrate, which process comprises the steps of:

a) dissolving a Cryoprotectant or a combination of Cryoprotectants in water for injection to form a solution;

b) adding a pemetrexed dipotassium hemiheptahydrate to the solution and dissolving the pemetrexed dipotassium hemiheptahydrate in the solution;

c) optionally filtering the solution obtained in step 2) to obtain a filtered solution;

d) Adjusting the pH to about 6 to about 8 using diluted sodium hydroxide solution or diluted hydrochloric acid solution

e) freezing the solution obtained in step 4) to form a frozen solution; and f) freeze drying the frozen solution to form the pharmaceutical composition, wherein the composition is having moisture content less than 5% w/w and substantially free of any additional pH modifier.

In another aspect of the present invention, it relates to a process for preparing a pharmaceutical composition containing a pemetrexed di potassium hydrate, which process comprises the steps of:

a) dissolving a Cryoprotectant or a combination of Cryoprotectants in water for injection to form a solution;

b) adding a pemetrexed dipotassium hemiheptahydrate to the solution and dissolving the pemetrexed dipotassium hemiheptahydrate in the solution, and determining the pH of the solution;

c) adjusting the pH of the bulk solution to 7.20 by addition of one or combination of Potassium hydroxide or Sodium hydroxide, and Hydrochloric acid.

d) Make up the volume to 100% with WFI and stirred for 5 minutes, and optionally determining the final pH of the solution.

e) Optionally, filtering the solution obtained in step d) through 0.2μ filter to obtain a filtered solution;

f) freezing the solution obtained in step e) to form a frozen solution; and

g) freeze drying the frozen solution to form the pharmaceutical composition, wherein the composition is having moisture content less than 5% w/w.

In yet another aspect of the present invention, it relates to the lyophilized formulation that may be reconstituted with aqueous solution, comprising distilled or sterile water for injection or saline or physiological saline, wherein the saline comprises at least one of a 0.9% solution of sodium chloride, a 0.45%> or a 0.225%) solution of sodium chloride or bacteriostatic water for injection which optionally comprises methylparaben and/or propylparaben and/or 0.9% benzyl alcohol.

In a further aspect of the present invention, it relates to a method of treating a patient for cancer comprising reconstituting a pharmaceutical composition by combining a lyophilized powder with an aqueous solution to form the reconstituted pharmaceutical composition that is free of visual particles; and injecting the reconstituted pharmaceutical composition intravenously into a patient. BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is Illustration of X-ray powder diffraction (XRPD) pattern of Crystalline Pemetrexed dipotassium hemiheptahydrate, prepared according to Reference Example.

Fig. 2 is Illustration of X-ray powder diffraction (XRPD) pattern of Crystalline Pemetrexed dipotassium hemiheptahydrate composition, prepared according to Example 3.

Fig. 3 is Illustration of X-ray powder diffraction (XRPD) pattern of Placebo lyophilized composition, prepared according to Example 5.

DETAILED DESCRIPTION

As set forth herein, aspects of the present invention provide pharmaceutical composition comprising pemetrexed dipotassium and its hydrates and process for preparation thereof.

In one aspect of the present invention, it relates to a pharmaceutical composition comprising pemetrexed di potassium hemiheptahydrate characterized by X-ray powder diffraction pattern containing at least 5 characteristic 29° diffraction angle peaks selected from the XRPD peak set of 5.00, 13.70, 16.90, 20.00, 21.40, 23.6, 24.2 and 28.30 ± 0.20 2Θ°, and a pharmaceutically acceptable amount of an excipient, wherein said composition is having moisture content less than 5% w/w.

In one aspect of the present invention, it relates to a lyophilized compositionof pemetrexed di potassium hemiheptahydrate, wherein the composition is characterized by X-ray powder diffraction pattern containing at least 5 characteristic 29° diffraction angle peaks selected from the XRPD peak set of 4.03, 4.26, 5.28, 11.53, 18.83, 21.76, 22.16, 24.75, 25.36, 25.98, 26.60, 27.92, 28.25, 31.78, 32.76, 34.38, 34.98, 38.78, 44.14 and 47.23 ± 0.2° 2Θ.

The characteristic peaks and their d spacing values of crystalline Pemetrexed dipotassium hemiheptahydrate for a particular batch material are tabulated in the Table- 1.

Table-1: Characteristic XRPD Peaks of Crystalline Pemetrexed dipotassium hemiheptahydrate S.No. Angle (2Θ°)±0.20 d Spacing Value (A ⁰ )

1 4.99 17.704

2 10.01 8.828

3 11.49 7.694

4 11.77 7.511

5 12.89 6.861

6 13.72 6.449

7 14.95 5.919

8 15.20 5.824

9 15.70 5.641

10 16.26 5.448

11 16.92 5.235

12 17.95 4.938

13 18.90 4.692

14 19.01 4.665

15 19.11 4.641

16 19.54 4.540

17 20.02 4.433

18 20.36 4.359

19 20.58 4.311

20 21.38 4.153

21 21.73 4.086

22 22.01 4.036

23 22.38 3.970

24 22.68 3.918

25 23.05 3.855

26 23.21 3.829

27 23.67 3.755

28 24.17 3.679

29 25.122 3.54189

30 25.597 3.47724

31 26.191 3.39979 32 26.369 3.37717

33 26.833 3.31987

34 27.524 3.23805

35 28.361 3.14437

36 29.377 3.03785

37 30.197 2.95723

38 30.959 2.88613

39 31.704 2.82007

40 31.921 2.80133

41 32.992 2.71282

42 34.174 2.62166

43 35.798 2.50634

44 40.522 2.22441

The term "pharmaceutical composition" as used in the context of the present invention refers to any of various dosage forms suitable for administration of a drug, such as parenterally, intra- peritoneally, intravenously, intra-arterially, intramuscularly, subcutaneously, orally etc.

In particular, the invention provides pharmaceutical composition comprising pemetrexed di potassium hemiheptahydrate and a pharmaceutically acceptable amount of an excipient effective to form a lyophilized cake. For example, the lyophilized preparations of the invention may contain one or more Cryoprotectants or a combination thereof.

Cryoprotectants (often referred as bulking agent) that have "generally regarded as safe" (GRAS) status from the United States Food and Drug Administration (FDA) are well known in the art of pharmaceutical lyophilization and tend to strengthen the structure of the resulting lyophilized cake. Bulking agents include saccharides, preferably monosaccharides or oligosaccharides, sugar alcohols, and mixtures thereof. More specifically, bulking agents used in the present invention include sucrose, dextrose, maltose, lactose, sorbitol, glycine, mannitol and dextran. A most preferred bulking agent is mannitol.

The present invention also relates to pharmaceutical composition comprising pemetrexed di potassium hemiheptahydrate, wherein a moisture content of the formulation is preferably less than about 5% by weight. The present invention also relates to pharmaceutical composition comprising about lOmg/ml to about lOOmg/ml of pemetrexed di potassium hemiheptahydrate calculated as pemetrexed; excipients comprising about lOmg/ml to about 200mg/ml of the excipient, wherein the excipient comprising at least one Cryoprotectant, and a solvent selected from water, DMSO, ethanol and acetonitrile.

The present invention also relates to pharmaceutical composition comprising about lOmg/ml to about lOOmg/ml of pemetrexed di potassium hemiheptahydrate calculated as pemetrexed; excipients comprising about lOmg/ml to about 200mg/ml of the excipient, wherein the excipient comprising at least one Cryoprotectant, and water.

In one of the particular embodiment of the present invention, the pharmaceutical composition comprises about 33.37mg/ml pemetrexed di potassium hemiheptahydarte calculated as equivalent to about 25mg/ml of pemetrexed, and about 25 to 27 mg/ml of the excipient as mannitol, which in reconstitution solution comprises a pH value of about 6 to about 8.

In further embodiments, the invention relates to lyophilized powder being suitable for reconstitution to form a liquid composition for parenteral administration, wherein the lyophilized powder is having moisture content less than 5% w/w. The reconstituted pharmaceutical composition formed from the lyophilized powder wherein the reconstituted pharmaceutical composition is substantially free of any additional pH modifier.

The reconstituted pharmaceutical compositions of the present invention possess a pH value in the range of about 6 to about 8.

In yet another embodiment, the invention provides a method of using a pharmaceutical composition for the manufacture of a medicament for the treatment of cancer in a mammal, wherein the pharmaceutical composition comprises pemetrexed dipotassium hemiheptahydrate and a pharmaceutically acceptable amount of an excipient effective to form a lyophilized cake, wherein the composition is having moisture content less than 5% w/w and substantially free of any additional pH modifier, the method comprising forming the medicament from the pharmaceutical composition.

The embodiment of the present invention, further encompass their physical properties for the compositions derived from pemetrexed dipotassium, wherein the properties include, but are not limited to, porosity, density, particle size, dispersion-ability, moisture content, pH, syringe- ability, injectability, particulate matter, and endotoxins.

In yet further embodiment, the invention relates to a process for preparing a pharmaceutical composition containing a pemetrexed dipotassium hemiheptahydrate, which process comprises the steps of:

a) Dissolving a Cryoprotectant or a combination of Cryoprotectants in water for injection to form a solution;

b) adding a pemetrexed dipotassium hemiheptahydrate to the solution and dissolving the pemetrexed dipotassium hemiheptahydrate in the solution;

c) optionally filtering the solution obtained in step 2) to obtain a filtered solution;

d) Adjusting the pH to about 6 to about 8 using diluted sodium hydroxide solution or diluted hydrochloric acid solution

e) freezing the solution obtained in step 4) to form a frozen solution; and

f) freeze drying the frozen solution to form the pharmaceutical composition, wherein the composition is having moisture content less than 5% w/w and substantially free of any additional pH modifier.

In yet further embodiment, the invention relates to a process for preparing a pharmaceutical composition containing a pemetrexed dipotassium hemiheptahydrate, which process comprises the steps of:

a) dissolving a Cryoprotectant or a combination of Cryoprotectants in water for injection to form a solution;

b) adding a pemetrexed dipotassium hemiheptahydrate to the solution and dissolving the pemetrexed dipotassium hemiheptahydrate in the solution, and determining the pH of the solution;

c) adjusting the pH of the bulk solution to 7.20 by addition of one or combination of Potassium hydroxide or Sodium hydroxide, and Hydrochloric acid.

d) Make up the volume to 100% with WFI and stirred for 5 minutes, and optionally determining the final pH of the solution.

e) Optionally, filtering the solution obtained in step d) through 0.2μ filter to obtain a filtered solution;

f) freezing the solution obtained in step e) to form a frozen solution; and

g) freeze drying the frozen solution to form the pharmaceutical composition, wherein the composition is having moisture content less than 5% w/w. In yet further embodiment, the invention relates to a process for preparing a pharmaceutical composition containing a pemetrexed dipotassium hemiheptahydrate, which process comprises the steps of:

a) dissolving a Cryoprotectant or a combination of Cryoprotectants in water for injection to form a solution;

b) adding a pemetrexed dipotassium hemiheptahydrate to the solution and dissolving the pemetrexed dipotassium hemiheptahydrate in the solution, and determining the pH of the solution;

c) adjusting the pH of the bulk solution to 7.20 by addition of one or combination of Potassium hydroxide or Sodium hydroxide, and Hydrochloric acid.

d) Make up the volume to 100% with WFI and stirred for 5 minutes, and optionally determining the final pH of the solution.

e) Optionally, filtering the solution obtained in step d) through 0.2μ filter to obtain a filtered solution;

f) freezing the solution obtained in step e) to form a frozen solution; and

g) freeze drying the frozen solution to form the pharmaceutical composition, wherein the composition is having moisture content less than 5% w/w, and substantially free of any additional pH modifier.

Additional pH modifier wherever used in entirety of the present specification, indicates organic or inorganic compounds used additionally to modify the pH of the final bulk solution before lyophilization.

In the present embodiment, no additional pH modifier before lyophilization is utilized in order to retain the identity and purity of pemetrexed dipotassium hemiheptahydrate compound. This identity of pemetrexed dipotassium hemiheptahydrate compound may vary, if additional pH modifier(s) be utilized in the latter stages by displacing the potassium ions from the pemetrexed dipotassium hemiheptahydrate salt compound, in the lyophilized composition.

Though the specifics of the process may be known from the examples represented below in the example section, however, the technique known as lyophilization is employed to prepare pharmaceutical composition of the present invention is detailed herein below. The lyophilization process is employed for certain injectable pharmaceuticals that may exhibit poor active ingredient stability in aqueous solutions. Lyophilization process is suitable for injectable because it can be conducted under sterile conditions, which is a primary requirement for parenteral dosage forms. Cryoprotectants are excipients whose primary function is to protect the active constituent during a freezing process.

Lyophilization, also known as freeze-drying is a process in which water is removed from a product after it is frozen and placed under a vacuum, allowing the ice to change directly from a solid to a vapor, without passing through a liquid phase. The process consists of three separate, unique, and interdependent processes; a freezing phase, a primary drying phase (sublimation), and a secondary drying phase (desorption). These processes may be optimized to enhance the product stability as well as decrease the manufacturing costs.

Freezing Phase:

A primary function of the freezing phase is to ensure that the entire container having the complex solution is completely frozen, prior to proceeding to a subsequent phase. Additionally, it is usually desired that these containers freeze in a uniform manner. While there are different ways that this can be accomplished, one option is to chill the containers after they are loaded onto the lyophilizer shelves and holding for 30-60 minutes prior to initiation of the freezing cycle. It is generally not practical to equilibrate the shelves to a freezing temperature, because of frost accumulation during the filling and loading of the containers.

Primary Drying Phase:

Once the formulation is brought to the desired frozen state, primary drying via sublimation can proceed. The primary drying phase involves the removal of bulk water at a product temperature below the ice transition temperature under a vacuum (pressures typically between 50-300 mTorr). This phase can be a critical one for stabilizing an active. The goal is to identify the glass transition temperature (Tg') for the formulation. The Tg' is the temperature at which there is a reversible change of state between a viscous liquid and a rigid, amorphous glassy state. One can measure the Tg' of candidate formulations using a differential scanning calorimeter (DSC), in particular with modulated DSC. Generally, the collapse temperature is observed to be about 2-5°C greater than the Tg'. Hence, the shelf temperature is set such that the target product temperature is maintained near or below the Tg' of the formulation throughout the removal of As the solvent is progressively removed from the formulation containers, the product temperature will approach and reach the shelf temperature since it is no longer cooled by water sublimation. To optimize the duration of the primary dry phase, the removal of solvent vapor can be tracked using a moisture detector, or by monitoring the decrease in pressure difference between a capacitance manometer and a thermocouple pressure gauge or by a pressure drop measurement. The optimization of the primary dry cycle involves a removal of solvent as quickly as possible without causing cake collapse and subsequent product instability.

Secondary Drying Phase:

The secondary drying phase is the final segment of the lyophilization cycle, where residual moisture is removed from a formulation's interstitial matrix by desorption with elevated temperatures and/or reduced pressures. The final moisture content of a lyophilized formulation, which can be measured by Karl Fischer or other methods, is important because if the solid cake contains too much residual moisture, the stability of the active can be compromised. Hence, it is imperative that one achieves a moisture level as low as possible.

To accomplish a low residual moisture, the shelf temperature is typically elevated to accelerate desorption of water molecules. The duration of the secondary drying phase is usually short. When microstructure collapse occurs, the residual moisture is generally significantly greater than desired. One alternative is to purge the sample chamber of the lyophilizer with alternating cycles of an inert gas such as nitrogen, to facilitate displacement of bound water. However, another solution is to properly formulate the drug product and run an optimal lyophilization cycle.

The advantages of lyophilization include: ease of processing a liquid, which simplifies aseptic handling; enhanced stability of a dry powder; removal of water without excessive heating of the product; enhanced product stability in a dry state; and rapid and easy dissolution of reconstituted product. The product is dried without elevated temperatures, thereby eliminating adverse thermal effects, and then stored in the dry state in which there are relatively few stability problems.

Additionally, freeze dried products are often more soluble, dispersions are stabilized, and products subject to degradation by oxidation or hydrolysis are protected.

Pharmaceuticals to be freeze dried are frequently in aqueous solutions, ranging from about 0.01 to 40% by weight concentrations of total solids. Usually, an improvement in stability of the lyophilizate, compared to a solution, is due to the absence of water in the lyophilizate.

A pharmacologically active constituent of many pharmaceutical products is present in such small quantities that, if freeze dried alone, it may not give a composition of suitable mass, and in some cases its presence would be hard to detect visually. Therefore, excipients are often added to increase the amount of solids present. In most applications it is desirable for a dried product cake to occupy essentially the same volume as that of the original solution. To achieve this, the total solids content of the original solution is frequently about 10 to 25% by weight.

Cryoprotectants or Bulking substances that are useful for this purpose, often in combination, include, but are not limited to, sodium or potassium phosphates (monobasic potassium phosphate, potassium dihydrogen phosphate, etc.), citric acid, tartaric acid, gelatin, lactose and other carbohydrates such as dextrose, mannitol and dextran, and occasionally preservatives. Various excipients contribute appearance characteristics to the cake, such as dull and spongy, sparkling and crystalline, firm or friable, expanded or shrunken, and uniform or striated. Therefore formulations of a composition to be freeze dried should be a result of consideration not only of the nature and stability characteristics required during the liquid state, both freshly prepared and when reconstituted before use, but also the characteristics desired in the final lyophilized cake.

The injectable pharmaceutical formulations may optionally include one or more other pharmaceutically acceptable excipients. The pharmaceutically acceptable excipients may include any one or more of: antibacterial preservatives, such as one or more of phenylmercuric nitrate, thiomersal, benzalkonium chloride, benzethonium chloride, phenol, cresol, and chlorobutanol; antioxidants including one or more of ascorbic acid, sodium sulfite, sodium bisulfite and sodium metabisulfite; chelating agents such as ethylenediamine tetraacetic acid (EDTA); buffers including one or more of acetate, citrate, tartarate, phosphate, benzoate and bicarbonate buffers; tonicity contributors including one or more of sodium chloride, potassium chloride, dextrose, mannitol, sorbitol and lactose; and alkaline substances including one or more of sodium hydroxide, potassium hydroxide, sodium carbonate and meglumine. In another embodiment of the invention, it provides a sterile vessel containing pemetrexed dipotassium for administration to a subject in need thereof. The sterile vessel containing a pharmaceutical formulation according to the present invention may be a vial, syringe, or ampoule.

Stress stability studies have shown that the two main degradation pathways for pemetrexed in solid state and in solution are oxidation and hydrolysis. Pemetrexed appears to be susceptible to oxidation and the presence of moisture; hence its formulations should be processed and maintained at minimum levels of oxygen. The headspace of a vial should contain less than about 8% (eight percent) v/v oxygen, or in the range of about 2% to about 5% v/v oxygen, or in the range of about 3% to about 5% v/v oxygen. The headspace of the vial can be adjusted to minimize the formulation contact with oxygen. It is generally desired that the headspace is not more than about one-third of the total volume of the container, with the contents occupying at least about two-thirds of the total volume of the container. For example, 5 ml of product may be contained in a 7.5 ml vial. To avoid oxidation, antioxidants can be included. If a greater headspace ratio is desired, then the concentration of an antioxidant may be adjusted as necessary.

Further embodiments of the invention also provides compositions and pharmaceutical formulations in lyophilized form, wherein the compositions after reconstitution form a clear solution within 3 minutes or less of gentle agitation.

In particular embodiment of the present invention, the reconstituted pharmaceutical composition may be injectable intravenously or intraperitoneal or intramuscular.

The reconstitution of lOOmg vial according to the present invention comprise reconstitution with aqueous solutions ranging between 4 to 5ml,similarly 500 mg vial according to the present invention comprise reconstitution with aqueous solution ranging between 18 to 25 ml, it is preferable to reconstitute either size of the vial to provide a solution containing about 25mg/ml of pemetrexed. Due to high soluble nature of the composition according to the present invention it requires less amount of aqueous solution for reconstitution over the prior art formulation of pemetrexed disodium, The aqueous solution of an approximately 10 to 50% less amount may be used in preparing the reconstitution over the prior art formulation of pemetrexed disodium. Owing to the advantage of compositions of the present invention a reconstitution solution devoid of sodium content may provide cardio protective role for the patients suffering with cardiac disorders due to use of sodium ion.

Particular embodiment of the present invention provides kits provided for delivery of the pemetrexed or its salts. A kit according to the present invention comprises a container holding the drug composition, a sterile reconstitution vehicle, and a sterile syringe.

The area used for processing the compositions and formulations of the present invention generally should comply with the requirements given in the current United States Pharmacopoeia ("USP") for parenteral dosage forms.

Certain specific embodiment of the invention will be further described in the following examples, which are provided only for purposes of illustration and are not intended to limit the scope of the invention in any manner.

The compositions for parenteral administration can be lyophilized powder, suspensions, emulsions or aqueous or non-aqueous sterile solutions.

The residual moisture levels in the lyophilized composition impact the storage stability of the lyophilized composition for a desired temperature and duration. Desirably, the amount of residual moisture in the lyophilized composition should be less than about 5% w/w.

Reconstitution of the lyophilized composition (which can be stored for an extended period of time at typical storage temperatures), typically just before administration to the patient, utilizes an appropriate liquid medium to produce a solution, suspension, dispersion, or emulsion. A reconstitution medium may include sterile water, water for injection, a pH buffered solution, or 5% dextrose solution (D5W). The reconstitution is usually performed at room temperature, however other temperatures may also be considered. The reconstituted lyophilized composition should pass the current United States Pharmacopeia (USP) Test 788 particulate matter specifications.

The USP particulate matter test defines the amount of foreign particulate matter, as observed by optical microscopy. According to Test 788, the limit in each product container for foreign particulate matter having sizes greater than or equal to 10 μιη is 3000, and for particles having sizes greater than or equal to 25 μιη is 300.

An important physicochemical characteristic of particulate compositions is the density properties. Bulk density is described as untapped or tapped. Untapped bulk density of a substance is the undisturbed packing density of that substance and tapped bulk density relates to the packing density after tapping a bed of substance until no change in the packing density is seen. Bulk density and tapped density can be determined using a compendial bulk density apparatus, a suitable method being given in United States Pharmacopeia 29, United States Pharmacopeial Convention, Inc., Rockville, Maryland, 2005, at pages 2638-2639.

While determining purity by HPLC, following analytical chromatographic conditions were used to determine the purity of the material along with impurity profile wherever required. Certain conditions may vary to some extent as per system suitability as well as person skilled in the art to perform the sample preparation and executing the analysis, however, method of purity according to the one of the merits of invention provides robust, consistent and reliable information.

Column : 4.6 X 250 mm, 5μ packing L-l or equivalent.

Flow rate : l .O mL/min.

Detector : 226 nm

Injection volume : 10 μΐ,

Column Oven temperature : 25°C ± 2 °C

Mobile phase-A : Buffer - 0.05M KH2P04 in 1000 mL water adjust pH to

6.0

Mobile phase-B : HPLC grade Acetonitrile Gradient Program

Time in minutes Mobile Phase- A Mobile Phase- B

0 90 10

5.0 90 10

17.0 70 30

40.0 70 30

45.0 90 10

50.0 90 10 Certain specific aspects and embodiments of the present application will be explained in more detail with reference to the following examples, which are provided by way of illustration only and should not be construed as limiting the scope of the invention in any manner.

EXPERIMENTAL DETAILS

Pemetrexed dipotassium hydrate is prepared by the example as given below.

Reference Example:

Preparation of Crystalline Pemetrexed dipotassium hydrate

Dipotassium salt of N-[4-[2-(2-amino-4,7-dihydro-4-oxo-lH-pyrrolo[2,3-d]pyrimidi n-5- yl)ethyl] benzoyl] -L-glutamic acid (20.0 g) was added in DM water (80 ml) under stirring at RT until dissolution.

It is subjected to filtration through hyflow bed. The filtrate is cooled to about 0-10°C with continuous stirring.

Ethyl alcohol is added gradually (325 ml) within 60-90 minutes at 0-10°C under continuous stirring. The solution temperature is raised gradually to 20-25°C under stirring.

Once the temperature of 20-25°C is attained, it is allowed to maintain for 3-4 hours at same temperature (20-25°C).

Isolated solid in the solution mass is filtered and washed with ethyl alcohol (45 ml).

It was subjected for drying under vacuum to give the title compound

Yield: 15 g, -75.0%

Purity (by HPLC): 99.53% w/w ; Water content (by KF): 11.00% w/w

Example 1-2: Pemetrexed Di Potassium Hemiheptahydrate composition

Manufacturing process:

1) Water for injection is placed into a mixing vessel and stirred continuously. During stirring, the solution is purged continuously with nitrogen gas.

2) To about 90% amount of water for injection, mannitol is added with stirring to dissolve. 3) Pemetrexed dipotassium hemiheptahydrate is added to the step 2) solution and dissolved with continuous stirring.

4) The pH of the solution is adjusted, as needed, to about 6.6 to 7.8 using 0.5N sodium hydroxide solution or 0.5N hydrochloric acid solution.

5) The volume is made up to 20 mL with the remaining water and mixed well.

6) For Example 2, 20 mL of the solution from step 5) is filled into 50 mL depyrogenated USP type I glass vials and the vials are loosely stoppered with slotted sterile bromobutyl rubber stoppers.

7) For Example 1, 4 mL of the solution from step 5) is filled into 10 mL USP type I glass vials and the vials are loosely stoppered with slotted sterile bromobutyl rubber stoppers.

8) The loosely stoppered vials are lyophilized in a freeze dryer. Lyophilization cycle parameters are as follows:

9) After completion of lyophilization, the vacuum is released by introduction of nitrogen and then vials are stoppered completely by hydraulic pressing. The vials are further sealed with flip-off seals.

10) The vials are cleaned externally and stored at 15-30°C.

The vials of Example 1 and 2 are stored at 40°C and 75% RH for 3 months and analyzed for pH, water content (by Karl-Fisher), drug assay, and other parameters. The results are tabulated below, where drug assays are percentages of the label pemetrexed content.

Parameter Example 1 Example 2

Initial Initial

pH (2.5% w/v -7.2 -7.2

Samples from Examples 1 and 2 were stored at 40 C and 75% RH, and at 30 C and 75% RH, for 3 months to assess the stability pattern. The stability pattern observed was consistent in comparison of initial analysis.

Example 3-4: Pemetrexed Di Potassium Hemiheptahydrate composition

Manufacturing process:

1) Water for injection is placed into a mixing vessel and stirred continuously. During stirring, the solution is purged continuously with nitrogen gas.

2) To about 90% amount of water for injection, mannitol is added with stirring to dissolve.

3) Pemetrexed dipotassium hemiheptahydrate is added to the step 2) solution and dissolved with continuous stirring, and the solution pH is determined;

4) The pH of the bulk solution is adjusted to 7.20using 0.5N potassium hydroxide solution or 0.5N hydrochloric acid solution.

5) The volume is made up to 20 mL with the remaining water and mixed well. The pH of the final bulk solution is determined.

6) The final bulk solution is filtered through 0.2μ filter.

7) For Example 4, 20 mL of the solution from step 6) is filled into 50 mL depyrogenated USP type I glass vials and the vials are loosely stoppered with slotted sterile bromobutyl rubber stoppers.

7) For Example 3, 4 mL of the solution from step 6) is filled into 10 mL USP type I glass vials and the vials are loosely stoppered with slotted sterile bromobutyl rubber stoppers.

8) The loosely stoppered vials are lyophilized in a freeze dryer. Lyophilization cycle parameters are as follows: Temperature Ramp Soak duration Pressure Pressure Condenser

Step

°C duration (min) (min) (mTorr) (mbar) Temp °C

Freezing

1 -15 60 60 - - -

2 -40 60 180 - - -

Primary Drying

3 -40 - 30 250 0.3330

4 -15 180 600 250 0.3330

5 -5 60 600 250 0.3330

-60

6 5 30 450 150 0.2000

7 25 60 510 100 0.1330

Secondary Drying

8 40 60 870 50 0.0670 -60

9) After completion of lyophilization, the vacuum is released by introduction of nitrogen and then vials are stoppered completely by hydraulic pressing. The vials are further sealed with flip-off seals.

10) The vials are cleaned externally and stored at 15-30°C.

Example 5-6: Placebo lyophilized compositions

Example 5&6 are Placebo lyophilized compositions for Example 3 & 4 Pemetrexed lyophilized compositions respectively.

Manufacturing process:

1) Water for injection is placed into a mixing vessel and stirred continuously. During stirring, the solution is purged continuously with nitrogen gas.

2) Mannitol is added with stirring to dissolve.

3) The solution pH is determined;

4) The pH of the bulk solution is adjusted to 7.20using 0.5N potassium hydroxide solution or 0.5N hydrochloric acid solution.

5) The volume is made up to 20 mL with the remaining water and mixed well. The pH of the final bulk solution is determined. 6) The final bulk solution is filtered through 0.2μ filter.

7) For Example 6, 20 mL of the solution from step 6) is filled into 50 mL depyrogenated USP type I glass vials and the vials are loosely stoppered with slotted sterile bromobutyl rubber stoppers.

8) For Example 5, 4 mL of the solution from step 6) is filled into 10 mL USP type I glass vials and the vials are loosely stoppered with slotted sterile bromobutyl rubber stoppers.

9) The loosely stoppered vials are lyophilized in a freeze dryer. Lyophilization cycle parameters are and post lyophilization steps are also followed in the same manner as described under Example 3-4.

Example 3 Pemetrexed Di Potassium Hemiheptahydrate composition(100mg/vial) &Example 5 placebo lyophilized composition were subjected to X-ray powder diffraction (XRPD) study.

Fig. 2is theillustration of XRPD pattern of Crystalline Pemetrexed dipotassium hemiheptahydrate composition, prepared according to Example 3.

Fig. 3is theillustration of XRPD pattern of Placebo lyophilized composition, prepared according to Example 5.

The abovementioned examples, which are provided by way of illustration, should not be construed as limiting the scope of the invention with respect to parameter/s, ingredient/s and quantities used in any manner.

Literature, references, including publications, issued patents and patent applications, cited in the specification are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

Usage of the terms "a" and "an" and "the" and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms "comprising," "having," "including," and "containing" are to be construed as open- ended terms (i.e., meaning "including, but not limited to,") unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. The term wt% refers to percent by weight. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples or exemplary language (e.g. "such as") provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.