DESC:FIELD OF THE INVENTION
The present invention relates to a liquid pharmaceutical formulation containing carmustine at a high concentration, wherein the solubility of the carmustine is improved. Typically, the formulation disclosed according to present invention contains at least 20 mg /ml of carmustine. Specifically, the formulation disclosed according to present invention contains 20 mg/ml to 500 mg/ml of carmustine dissolved in a solvent system comprising polyethylene glycol and a solubilizer.
BACKGROUND OF THE INVENTION
Halogenated alkyl nitrosoureas have long been known as antineoplastic agents. The best known in the class is 1, 3-bis(2-chloroethyl)-1-nitrosourea, which is generically known as carmustine. Also known as BCNU or BiCNU, carmustine is widely evaluated for use in several cancers and since 1972 has been investigated by the National Cancer Institute for treatment against brain tumours, colon cancer, hodgkin’s disease, lung cancer, and multiple myeloma.
Carmustine is a cell cycle-nonspecific nitrosourea analog that alkylates DNA and RNA, interfering with the synthesis and function of DNA, RNA and proteins. It also binds to and modifies (carbamoylates) glutathione reductase, which consequently leads to cell death. Though the drug has poor oral bioavailability, following IV infusion, it is rapidly taken up by the tissues, and due to the high lipid solubility, it can cross the blood brain barrier. However, it is rapidly degraded, with no unmetabolized drug detectable after 15 minutes.
At present, carmustine for injection is solely available in the form of lyophilized material, which need to be reconstituted before administration. However, the lyophilized formulation is associated with several disadvantages such as, double handling, longer dissolution time for the lyophilized cake, improper dose.
Various attempts have been made to prepare a liquid formulation of carmustine, however, the low aqueous solubility of carmustine and poor stability of liquid formulations of carmustine has vexed researchers in this field for long. Even today, there is no commercially available

liquid formulation of carmustine. The various reported liquid formulations for carmustine are as follows:
International patent application no. WO/2008/119260 discloses a pharmaceutical composition comprising a pharmaceutically effective amount of carmustine, tween surfactant and a co-solvent combination of glycerine and/or polyglycol. The said pharmaceutical composition may be in the form of a liquid or freeze dried powder for injection. The present invention also discloses the method of preparation of the said composition.
CN101143130 relates to a parenteral formulation of carmustine in the form of a stable oil-in-water emulsion. The composition comprises of pharmaceutically effective amount of carmustine, oil, a surfactant and water for injection. The invention also discloses the method of preparation of the said oil-in-water emulsion.
CN1110134 relates to an injectable, liposomal formulation and the process for its preparation wherein the fat-soluble pharmaceutically active ingredient and the liposome matrix are dissolved in an organic solvent to obtain lipid-soluble liquor or alternatively, only the liposome matrix is dissolved in the organic solvent, and then a water-soluble liquid pharmaceutically active ingredient is added to the lipid-soluble liquor. The organic solvent is then removed from the liquor by using vacuum drying method and then nitrogen gas is charged into it.
Further, CN101444482, CN101385709 and CN101427996 provide sustained-release injectable formulations containing a nitrosourea drug, which comprises of sustained-release microspheres and solvents. The sustained-release microspheres each comprise an anticancer-active component selected from nitrosourea drugs (such as nimustine and carmustine) and/or topoisomerase inhibitors, and a sustained-release agent. The solvents are common solvents or special solvents containing suspending agent. However, such processes are complex and expensive.
CN 1683016 discloses a process for preparation carrier particles containing surface transferrin for glioma-targeted-chemotherapy. Biodegradable polymers like polylactic acid, polyglycolic acid, polycaprolactone or copolymer of lactic acid and glycolic acid and chemotherapeutic drugs such as carmustine, adriamycin or taxols are dissolved in acetone, acetonitrile or dimethyl sulfoxide; and the solution is emulsified in a solution of transferrin or combined with transferrin chemically after co-dialysis with cholesterol modified glucosan dialdehyde to prepare the drug-carrying polymer particle containing surface transferrin. Such particles may be injected into tumor cavity for targeted release of the drug.
Indian patent application, 1909/MUM/2015, also discloses liquid formulation of carmustine, however, the concentration of carmustine present in the liquid formulation is from 5 mg/ml to 20 mg/ml and specifically 12.5 mg/ml. The recommended dose of carmustine as a single agent in previously untreated patients is 150 to 200 mg/m2 intravenously every 6 weeks. Therefore, for a person having normal body surface area, 250 mg to 350 mg dose is required, which amounts to be administration of at least 20 mL of injection.
Hence, there is a persistent need for a stable, therapeutically acceptable formulation containing high concentration of carmustine. In particular, there is need for a stable liquid pharmaceutical formulation, containing high concentrations of carmustine and which are stable not only at refrigerator temperatures but also at room temperature.
SUMMARY OF THE INVENTION
The present inventors have found that by judicious use of suitable excipients and procedures, a stable liquid pharmaceutical formulation containing high concentrations of carmustine can be obtained.
Typically, the present invention provides liquid pharmaceutical formulation containing at least 20 mg/ml of carmustine that is stable enough for clinical use, and yet provides the desirable carmustine concentration for immediate use, by parenteral administration.
Thus, in one embodiment, the present invention provides liquid pharmaceutical formulation containing high concentrations of carmustine, suitable for parenteral administration.
In yet another embodiment, the present invention provides a stable liquid pharmaceutical formulation comprising from about 20 mg/ml to about 500 mg/ml of carmustine dissolved in a solvent system comprising of polyethylene glycol and a solubilizer.
In an embodiment of the present invention, the liquid pharmaceutical formulation comprises about 20 mg/ml to about 500 mg/ml of carmustine, from about 0.01% w/v to about 90% w/v of polyethylene glycol and from about 0.001 % w/v to about 50% w/v solublizer.
More specifically, according to the preferred embodiment of the present invention, the ratio of polyethylene glycol to solublizer is from about 0.1 to 10.
Further, according to the present invention, other optional pharmaceutical excipients such as buffers, pH adjusters, antioxidants, reducing agents, antimicrobial preservatives, stabilizing agents etc. can also be used in the said pharmaceutical preparation. Typically, addition of antioxidants such as ascorbic acid, citric acid imparts desirable stability to the formulation.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides liquid pharmaceutical formulation containing high concentration of carmustine that is stable enough for clinical use, and yet provides the desirable carmustine concentration for immediate use, by parenteral administration.
As used herein, the term “high concentration of carmustine” means that the carmustine is present in the formulation at a concentration of at least 20 mg/ml. More preferably, the term means, the concentration of carmustine in the liquid formulation is from about 20 mg/ml to about 500 mg/ml. Typically, the concentration of carmustine present in the formulation varies from about 50 mg/ml to 150 mg/ml, and more preferably, the concentration of the carmustine in the present formulation is 50-100 mg/ml.
As used herein, a "stable" formulation is defined as a formulation wherein no aggregation is observed when the said pharmaceutical preparation is stored below 10°C or at room temperature, for at least 6 months and wherein the assay of carmustine would not be less than 90%.
The present invention further provides a liquid pharmaceutical formulation containing from about 20 mg/ml to around 500 mg/ml of carmustine dissolved in a solvent system comprising of polyethylene glycol and a solubilizer.
Though, the present formulation is developed by using polyethylene glycol, however, any solvent which is physiologically acceptable and which is able to dissolve the carmustine may be used. The concentration of the solvent used in the formulation according to present invention varies from about 0.01% w/v to about 90% w/v of the formulation. Typically, it is from about 1% w/v to about 50% w/v according to the preferred embodiment of the present invention, the polyethylene glycol having an average degree of polymerization of 200-1000 are preferred and polyethylene glycol having an average degree of polymerization of 200 to 600 is more preferable.
The solution of the invention may also contain one or more additional components such as a solubilizer. Suitable solubilizers that can be used according to the present invention are selected from, but are not limited to, aliphatic amides such as N,N-dimethylacetamide, N-hydroxy-2-ethyl-lactamide, alcohols such as ethanol, benzyl alcohol, glycols and polyalcohols such as propylene glycol, glycerine, esters of polyalcohols such as diacetine, triacetine, polyglycols and polyethers such as propylene glycol methyl ethers, and dioxolanes such as isopropylidene glycerine. Dehydrated alcohol, polyethylene glycol and N,N-dimethylacetamide are the preferred solubilizers according to the present invention.
According to the preferred embodiment of the invention, the solubilizers are present from about 0.001% w/v to about 50% w/v of the formulation. Typically, it is from about 0.1% w/v to about 40% w/v of the formulation.
The present inventors have further found that the ratio of polyethylene glycol to solublizer also helps to impart stability to the formulation. Typically, the ratio of polyethylene glycol to solublizer is from about 0.1 to 10 and more preferably it is 1 to 5.
The pharmaceutical formulation of the present invention, prepared by using various molecular weight of polyethylene glycol and solublizer such as N, N-dimethylacetamide, propylene glycol or dehydrated alcohol shows less than 1.0% of any individual impurity whereas total impurities are well below the pharmaceutically acceptable limit of 2.0%. Impurity A, which is well known to the carmustine formulation is well below the limit of 1.0%.
Further, according to the present invention, other optional pharmaceutical excipients such as buffers, pH adjusters, antioxidants, reducing agents, antimicrobial preservatives, stabilizing agents etc. can also be used in the said pharmaceutical preparation. The present inventors have found that typically, addition of antioxidants such as ascorbic acid, citric acid further helps in improving the stability of the formulation.
In another embodiment, the present invention provides a process for the preparation of a stable, liquid pharmaceutical formulation comprising high concentration of carmustine, suitable for parenteral administration. A general process for manufacture of the said pharmaceutical preparation of carmustine according to the present invention comprises of:
a) preparing the solvent system by mixing the polyethylene glycol and solubilizer,
b) dissolving carmustine in the solvent system prepared in step (a),
c) optionally adding other pharmaceutical excipients such as pH adjusters, antioxidants, reducing agents, antimicrobial preservatives, osmotic agents, stabilizing agents, to the solution obtained in step (b)
d) making up the final volume of the solution obtained in step (c),
e) filter sterilizing the pharmaceutical preparation obtained in step (d), and
f) filling the solution obtained in step (e) into suitable container/closure system.
Optional inert gas sparging (nitrogen gas) can be carried out during any of the steps of the process. Modifications in the generalized process can be made as known to the person skilled in the art.
Pharmaceutical preparation prepared according to the process disclosed in the present invention is sterilized using filter sterilization, e.g. 0.2micron filter, to render the solution sterile. This sterile pharmaceutical preparation is filled in suitable container/closure system, e.g., ampoules, vials, prefilled syringe system, etc.
The following examples further illustrate the invention but should not be construed as in any way limiting its scope. In particular, the processing conditions are merely exemplary and can be varied by one of ordinary skill in the art.

EXAMPLES
Example – 1: Preparation of liquid pharmaceutical formulation of carmustine
Formulation Qty per mL
(1a) Qty per mL
(1b)
Carmustine 50 mg 50 mg
N,N Dimethylacetamide (DMA) 0.33 mL 0.33 mL
Polyethylene Glycol (PEG) 0.67 mL 0.67 mL
Citric acid anhydrous 2 mg -
Ascorbic Acid - 1 mg

The formulation was prepared by using the procedure as described above and is evaluated for various parameters. The results of these studies are summarised herein below:
Analytical Results (1a) (1b)
pH 3.7 3.2
Assay (%) 103.2 103.7
Impurity A (%) 0.06 0.08
Any unspecified Imp (%) ND 0.01
Total impurity (%) 0.06 0.09

Example – 2: Preparation of liquid pharmaceutical formulation of carmustine
Formulation Qty per mL
(2a) Qty per mL
(2b)
Carmustine 50 mg 50 mg
Dehydrated Alcohol (DHA) 0.33 mL 0.33 mL
Polyethylene Glycol (PEG) 0.67 mL 0.67 mL
Citric acid anhydrous 2 mg -
Ascorbic Acid - 1 mg

The formulation was prepared by using the procedure as described above and is evaluated for various parameters. The results of these studies are summarised herein below:
Analytical Results (2a) (2b)
pH 3.1 3.7
Assay (%) 101.9 98.8
Impurity A (%) 0.09 0.08
Any unspecified Imp (%) ND ND
Total impurity (%) 0.09 0.08
Example – 3: Preparation of liquid pharmaceutical formulation of carmustine
Formulation Qty per mL
(3a) Qty per mL
(3b)
Carmustine 50 mg 50 mg
Propylene Glycol 0.33 mL 0.33 mL
Polyethylene Glycol (PEG) 0.67 mL 0.67 mL
Citric acid anhydrous 2 mg -
Ascorbic Acid - 1 mg
Example – 4: Preparation of liquid pharmaceutical formulation of carmustine
Formulation Qty per mL
(4a) Qty per mL
(4b)
Carmustine 100 mg 100 mg
N,N Dimethylacetamide (DMA) 0.33 mL 0.33 mL
Polyethylene Glycol (PEG) 0.67 mL 0.67 mL
Citric acid anhydrous 2 mg -
Ascorbic Acid - 1 mg
Example – 5: Preparation of liquid pharmaceutical formulation of carmustine
Formulation Qty per mL
(5a) Qty per mL
(5b)
Carmustine 100 mg 100 mg
Dehydrated Alcohol 0.33 mL 0.33 mL
Polyethylene Glycol (PEG) 0.67 mL 0.67 mL
Citric acid anhydrous 2 mg -
Ascorbic Acid - 1 mg
Example – 6: Preparation of liquid pharmaceutical formulation of carmustine
Formulation Qty per mL
(6a) Qty per mL
(6b)
Carmustine 100 mg 100 mg
Propylene Glycol 0.33 mL 0.33 mL
Polyethylene Glycol (PEG) 0.67 mL 0.67 mL
Citric acid anhydrous 2 mg -
Ascorbic Acid - 1 mg

,CLAIMS:
1. A liquid pharmaceutical formulation comprising carmustine and solvent system, wherein the concentration of carmustine is about 20 mg/ml to 500 mg/ml.

2. The liquid pharmaceutical formulation as claimed in claim 1, wherein the solvent system comprises of polyethylene glycol and solubilizer.

3. The liquid pharmaceutical formulation as claimed in claim 2, wherein the ratio of polyethylene glycol to solubilizer is from about 0.1 to 10.

4. The liquid pharmaceutical formulation as claimed in claim 2, wherein the polyethylene glycol has an average degree of polymerization of 200-1000.

5. The liquid pharmaceutical formulation as claimed in claim 2, wherein the concentration of polyethylene glycol is from about 0.01% w/v to about 90% w/v of the formulation.

6. The liquid pharmaceutical formulation as claimed in claim 2, the solubilizer may be selected from aliphatic amides such as N,N-dimethylacetamide, N-hydroxy-2-ethyl-lactamide, alcohols such as ethanol, benzyl alcohol, glycols and polyalcohols such as propylene glycol, glycerine, esters of polyalcohols such as diacetine, triacetine, polyglycols and polyethers such as propylene glycol methyl ethers, and dioxolanes such as isopropylidene glycerine.

7. The liquid pharmaceutical formulation as claimed in claim 2, wherein the concentration of solubilizers are from 0.001% w/v to about 50% w/v of the formulation.

8. The liquid pharmaceutical formulation as claimed in claim 1, further comprises an antioxidant

9. The liquid pharmaceutical formulation as claimed in claim 8, wherein the antioxidants are selected from ascorbic acid and citric acid, or mixtures thereof.

10. The liquid pharmaceutical formulation as claimed in claim 1, wherein the formualtion is for immediate use, by parenteral administration.