Complete Specifícation
Background of the Invention
Pemetrexed belongs to the class of chemotherapy drugs called folate antimetabolites and is used in the treatment of malignant pleural mesothelioma and non-small cell lung cáncer. Pemetrexed has the chemical ñame N-{4-[2-(2-Amino-4-oxo-4,7-dihydro-lH-pyrrolo[2,3-d]pyrimidin-5-yi)ethyi]benzoyl}-L-glutamic acid. The chemical structure is represented below:
Pemetrexed was approved by the United States Food and Drug Administration in February 2004 under the brand ñame Alimta" for the treatment of malignant pleural mesothelioma in combination with cisplatin, a platinum-containing chemotherapeutic drug. Alimta® is available as sterile lyophilized powder for intravenous infusión, in single-dose vials containing 100 mg or 500 mg equivalent Pemetrexed. In July 2004, the drug was approved by the FDA as a second line agent for the initial treatment of advanced or metastatic non-small cell lung cáncer.
Pemetrexed was first disclosed in US patent No. 5,344,932. Crystalline forms of Pemetrexed disodium designated as Disodium MTA Hydrate Form I have been described in WO/2001/014379.
US patent No. 7,138,521 describes a stable crystalline heptahydrate form of Pemetrexed having a characteristic X-ray diffraction pattern.
W0/2008/124485 discloses various crystalline forms of the pemetrexed diacid and an amorphous pemetrexed disodium.

EP 1943252 discloses a process for the preparation of a lyophilized di-base-addition salt of pemetrexed, in particular, a pemetrexed disodium salt, directly from pemetrexed diacid or an acid or base addition salt thereof.
US 2011201631 Al discloses a solid pharmaceutical formulation comprising amorphous pemetrexed.
Pemetrexed is available under the brand ñame Alimta® as sterile lyophilized powder for intravenous infusión, in single-dose vials. However, reconstitution of the lyophilized product is clinically inconvenient and also lyophilization process is time consuming and often incurs significant expense.- Henee, there is a strong need to develop altérnate formulations of Pemetrexed.
The inventors have developed ready to use liquid formulation of Pemetrexed which overcomes the disadvantages of the formulations reported in prior art.
Summary of the invention
The present invention relates to ready to use liquid parenteral pharmaceutical formulations of Pemetrexed and method of preparing such compositions.
One aspect of the invention provides stable ready to use liquid parenteral pharmaceutical formulation comprising of Pemetrexed, amino acids, saccharides, chelating agents and solvents.
Another aspect of the present invention is to provide ready to use liquid parenteral pharmaceutical formulation comprising of Pemetrexed diacid, disaccharides, arginine, chelating agents, suitable solvent or mixture of solvents; and other pharmaceutically acceptable adjuvants thereof.

Detailed description of the invention
In the context of this invention "Pemetrexed" refers to the pharmaceutically acceptable salts, solvates, hydrates, acids and free base forms, preferably Pemetrexed diacid.
As used herein, "ready to use Pemetrexed" formulations refers to formulations that contain Pemetrexed in dissolved or solubilised form and are to be intended to be used as such or upon further dilution in intravenous diluents.
An embodiment of the invention provides ready to use liquid parenteral pharmaceutical formulation comprising:
i. Pemetrexed,
ii. Amino acids,
iii. Saccharides,
iv. Chelating agents;
v. One or more solvents; Optionally other pharmaceutically acceptable adjuvants thereof.
A preferred embodiment of the invention comprises: i. Pemetrexed Diacid,
ii. Amino acids such as arginine, histidine or lysine
iii. Disaccharides such as sucrose, mannitol
iv. Chelating agents such as DOTA, DTPA
v. Solvents such as water, ethanol Optionally other pharmaceutically acceptable adjuvants thereof.
Suitable Amino acids according to the present invention include basic ámino acids such as arginine, histidine and lysine. Most preferred amino acid is Arginine.

The pharmaceutical compositions of the present invention comprise one or more saccharides such as, but not limited to sucrose, glucose, xylose, galactose, fructose, lactose, maltose, mannitol, sorbitol, xylitol, raffínose, dextrose, trehalose and the like. Of these the preferred saccharide is sucrose and mannitol. Sucrose is a disaccharide comprised of the monosaccharides glucose and fructose and has been used as a stabilizer in several Intravenous Immune Globulins (IVIG) products. The percentage of saccharides ranges from about 0.5% to 20% by weight of the formulation.
The pharmaceutical compositions of the present invention contains chelating agents such
as, but not limited to DOTA (l,4,7,10-tetraazacyclododecan-l,4,7,10-tetraacetic acid),
DTPA (diethylenetriamine-N,N,N',N",N"-pentaacetate), EDTA
(Ethylenediaminetetraacetic acid), ODDA (1 ,4, 10, ■- -13-tetraoxa-7, 16-
diazacyclooctadecane-7); TTTA (1,7,13-triaza-4,10,16-trioxacyclooctadecane-N,N',N"-triacetate), DOTRP (tetraethyleneglycol-1,5,9- triazacyclododecane-N,N',N",-tris(methylenephosphonic acid); DOTMA 1,4,7,10- tetraazacyclododecane-a,a',a",a' ' '-tetramethyl-N,N',N",N" '-tetraacetic acid; EGTA (ethylene glycol-bis(P-aminoethyl ether)-tetraacetic acid), HEDTA (N (hydroxy ethyl) ethylenediaminetriacetic acid), NTA (nitrilotriacetic acid). The percentage of chelating agent ranges from about ^0.01% to 5% based on total weight of the formulation.
Suitable solvents can be selected from aqueous and non-aqueous solvents such as, but are not limited to, glycerine, ethanol, n-propanol, n-butanol, isoproponal, ethyl acétate, dimethyl carbonate, acetonitrile, dichloromethane, methyl ethyl ketone, methyl isobutyl ketone, cyclohexane, dimethylacetamide (DMA), dimethyl sulfoxide (DMSO), l-methyl-2-pyrrolidone (NMP), l,3-dimethyl-2-imidazolidinone (DMI), acetone, tetrahydrofuran (THF), dimethylformamide (DMF), propylene carbonate (PC), dimethyl isosorbide, water and mixtures thereof. Mixtures of non-aqueous and aqueous solvents can also be used. Preferred solyent is water.

The pharmaceutical compositions of the present invention may contain one or more anti-oxidants, preservatives such as, but are not limited to butylated hydroxyanisole (BHA), butylated hydroxyl toluene (BHT), citric acid, lactic acid, benzoic acid, tocopherol (Vitamin E), monothioglycerol, ascorbic acid, methyl paraben, benzyl alcohol, propyl gállate, thioglycolic acid, niacinamide, nicotinic acid, creatine, citric acid, tartaric acid, phosphoric acid, gluconic acid, thiodipropionic acid, acetonic dicarboxylic acid, aminoacids and the like.
The formulation of the present invention may additionally comprise buffer, pH adjusting agents, stabilizers such as, but not limited to citrate buffer, glutamate, dicarboxylic acid, lecithin, di(hydroxyethyl)glycine, sorbitol, bicarbonate, tartrate, benzoate, lactate, gluconaté; glycine, TRIS buffer,acétate buffer, boric acid buffer, phosphate-buffer, acetic acid, lactic acid, amino acids, meglumine.
Pemetrexed diacid is practically insoluble in water. The inventors have surprisingly found that the presence of basic amino acids, saccharides and chelating agents yields a stable liquid formulation of Pemetrexed overcoming the disadvantages associated with prior art. The basic amino acids aid in the solubilization of Pemetrexed diacid in water.
Solubility of drug with various weight ratio of drug: arginine in water at 25°C temperature is summarized in Table 1.

The data from table 1 confirms the inventors finding that the presence of arginine in the formulation resulted in solubilization of Pemetrexed diacid in water. Complete solubilization was observed at a weight ratio of around 1:2 to 1:4 of Pemetrexed diacid: Arginine.
Compositions of the present invention will have a pH from 6 to 11. Preferably the pH would be from 8 to 10.
Pemetrexed formulations prepared with and without sucrose were tested for stability under accelerated conditions, at 60°C for 2 days. The stability data is summarized in Tables 2.
Formulations prepared with sucrose have less impurities, whereas formulations prepared without sucrose the impurities were found to be high.
Formulations prepared with increased quantity of mannitol (F-4) have less impurities compared to the formulations with reduced quantity of mannitol (F-3).
Formulations were prepared with and without DOTA were tested for stability under accelerated conditions, at 60°C for 2 days. The stability data is summarized in Table 3.

Formulations prepared with DOTA were found to have less impurites, whereas formulations prepared without DOTA have more impurities. Henee, Pemetrexed formulation in the presence of saccharides such as sucrose and chelating agents such as DOTA resulted in a stable formulation which is evident from tables 2 and 3.
The most preferred embodiment of the ready to use Pemetrexed formulation comprises:
i. Pemetrexed Diacid 2 - 20%
ii. Arginine 5 - 30%
iii. Sucrose or mannitol 0.5 - 20%
iv. DOTA 0.01 - 10%
v. Water 50 - 98%
The invention further relates to a process of preparing ready to use liquid parenteral pharmaceutical formulation of Pemetrexed diacid comprising
(i) Addition of amino acid and saccharide to the solvent/vehicle.
(ii) Addition of the chelating agent.
(iii) Addition of the Pemetrexed diacid to the above solution followed by stirring till a
clear solution is obtained. (iv)Filtering and filling of the solution in suitable container or vials followed by stoppering and sealing of the vials.
Pemetrexed formulation prepared according to the invention was tested for stability under accelerated conditions. Surprisingly no significant increase in total impurities was observed even at the accelerated conditions.

Stability of the formulation after Dilution
Chemical and physical stability of formulation was evaluated by diluting the sample with 0.9%w/v sodium chloride solution.
Stability of diluted solutions (lmg/mL and 5mg/mL) was demonstrated for up to 48 hours following initial dilution, when stored at 2-8°C. Results are summarized in Table 5.
From the above table it is evident that there is no significant difference between initial and 48 hours sample. Henee, the invention formulation is found to be stable for 48hrs after dilution with 0.9%w/v sodium chloride solution.

The following examples further describe certain specific aspects and embodiments of the present invention and demónstrate the practice and advantages thereof. It is to be understood that the examples are given by way of illustration only and are not intended to limit the scope of the invention in any manner.
Examples
Manufacturing process:
Water for injection was taken in a compounding vessel and arginine was added and stirred, followed by the addition of sucrose. DOTA was added to the above solution and stirred. Pemetrexed Diacid was added and stirred till a clear solution was obtained. The solution was filtered, followed by stoppering and sealing of the vials.
Pemetrexed formulation prepared according to the invention was tested for stability at various conditions. The stability data of the invention formulation is summarized in Table4. The product is tested for stability by storing at various conditions like 2-8°C; 25°C±60%RH; 30°C±65%RH; 40°C±75%RH.

Manufacturing process: Water for injection was taken in a compounding vessel and arginine was added and stirred, followed by the addition of sucrose. DOTA was added to the above solution and stirred. Pemetrexed Diacid was added and stirred till a clear solution was obtained. The solution was fíltered, followed by stoppering and sealing of the vials.
Manufacturing process:
Water for injection was taken in a compounding vessel and arginine was added and stirred. Sucrose was added in F-2 and mannitol in F-3 and F-4. DOTA was added to the above solution and stirred. Pemetrexed Diacid was added and stirred till a clear solution was obtained. The solution was fíltered, followed by stoppering and sealing of the vials.
Manufacturing process:
Water for injection was taken in a compounding. vessel and arginine was added and stirred, followed by the addition of sucrose. DOTA was added (A-2) to the above solution and

stirred. Pemetrexed Diacid was added and stirred till a clear solution was obtained. The solution was filtered, followed by stoppering and sealing of the vials.

We claim:
Claim 1: A stable, ready to use liquid parenteral pharmaceutical formulation of Pemetrexed comprising of Pemetrexed and pharmaceutically acceptable adjuvants thereof.
Claim 2: A stable, ready to use liquid pharmaceutical formulation comprising (i) Pemetrexed (ii) Amino acids (iii) Saccharides (iv) One or more solvents (v) Optionally other pharmaceutically acceptable adjuvants thereof.
Claim 3: The pharmaceutical formulations of claim 2 comprising (i) Pemetrexed diacid (ii) Amino acids such as Arginine, histidine (iii) Disaccharides such as sucrose, mannitol (iv) Solvents such as water, dimethylacetamide, ter-butanol. (v) Chelating agents such as DOTA, EDTA.