FIELD OF THE INVENTION
The present invention relates to pharmaceutical compositions containing a nitrosourea and to a method for the treatment of cancer. In particular, the invention relates to a stable pharmaceutical composition containing Carmustine in the form of ready-to-use solutions and methods for preparing the same.
BACKGROUND OF THE INVENTION
Halogenated alkyl nitrosoureas have long been known as antineoplastic agents. The best known of the class is l,3-bis(2-chloroethyl)-l-nitrosourea (Carmustine) having the following formula.
0
II
CI - CH2 - CH2 - N - C - NH - CH2 - CH2 - CI
NO
Also known as BCNU or BiCNU, Carmustine is widely evaluated for use in several cancers and since 1972 has been charted by the National Cancer Institute for utilization against brain tumors, colon cancer, Hodgkins 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 intact 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:

a) Double handling: To administer a lyophilized preparation, the lyophilized cake has to be first reconstituted and then administered;
b) Dissolution time of the cake: In some cases, the complete dissolution of the powder may require prolonged shaking because of solubilisation problems;
c) Health Hazard: Improper reconstitution of a lyophilized powder sometimes result in the formation of air-borne droplets ("blow-back"), which, in the case of a potent antitumor agent such as carmustine may be a health hazard to the personnel making up the solution for injection;
d) Improper dose: There is always a problem in reconstituting a lyophilized powder in that an inappropriate quantity of diluents may be used because of a different vial size. This could result in an improper dose being administered to a patient; and
e) Cost of manufacture: The manufacture of a lyophilized formulation is quite costly, since it not only requires capital investment for installation of a lyophilizer, but also its maintenance.
International patent application no. WO/2008/119260 discloses a pharmaceutical composition comprising a pharmaceutically effective amount of carmustine, tween surfactant, and cosolvent of glycerin and/or polyglycol. The said pharmaceutical composition may be a 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. In the disclosed process 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.
Despite the availability of prior art for different types of formulations of carmustine; because of the low solubility and stability of carmustine, it is cumbersome, inconvenient and expensive to manufacture ready-to-use liquid compositions of the drug.
Hence, there is an ongoing need for stable, therapeutically acceptable formulations of Carmustine, whose preparation and administration does not require either lyophilization or reconstitution. In particular, there is need for a stable, parenteral formulation of carmustine which can be administered as a ready-to-use option to a person in need, without the hassles of reconstitution.
SUMMARY OF THE INVENTION
The present inventors have found that by the judicious use of suitable excipients and procedures a stable, ready-to-use, injectable formulation of carmustine can be obtained.

In one embodiment, specific quantities of the various ingredients added at particular stages during the process of preparation impart to the novel formulation its desired properties.
The present invention provides pre-mixed, ready-to-use, parenteral formulation of carmustine that is stable enough for clinical use, and yet provides a suitable carmustine concentration for immediate use, by parenteral administration.
Thus, in one embodiment, the present invention provides a stable, ready-to-use, liquid pharmaceutical composition of carmustine, suitable for parenteral administration.
In yet another embodiment, the present invention provides a stable, ready-to-use, liquid pharmaceutical composition comprising carmustine dissolved in a suitable solvent system, free of surfactants.
In another embodiment, the present invention provides a simple and cost-effective method of preparing a ready-to-use, liquid pharmaceutical composition of carmustine, having improved solubility and stability.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to a stable, ready-to-use, liquid pharmaceutical composition, suitable for parenteral administration.
As used herein, a "ready-to-use" or "RTU" composition is a sterile, aqueous or non-aqueous or a combination thereof, injectable composition that is stable and has not been reconstituted from a lyophilizate. The RTU composition is also a sterile, aqueous or non-aqueous or a combination thereof, injectable composition that is stable and has been diluted from a concentrated, liquid solution.
As used herein, a "stable" composition is defined as no aggregation observed when the said pharmaceutical preparation is kept for stability studies carried out at 2° C. to 8° C. (Real time study) and 25° C/60% relative humidity (Accelerated study) for at least 6 months and wherein the assay of carmustine would not be less than 90%.

The assay of carmustine in the said pharmaceutical preparation can be carried out by any of the methods known to the person skilled in the art, e.g. high performance liquid chromatography (HPLC method), spectrophotometry (UV spectrophotometry), etc. According to the present invention, HPLC was used for performing the assay studies.
The present invention provides a stable, ready-to-use, liquid pharmaceutical composition comprising carmustine dissolved in a suitable solvent system, free of surfactants
In another preferred embodiment, the present invention provides pharmaceutical composition comprising carmustine at concentrations about 5 mg/mL to about 20 mg/mL. Preferably, the concentrations of carmustine are in the range of about 10 mg/mL to about 15 mg/mL.
Any solvent which is physiologically acceptable and which is able to dissolve the carmustine may be used. The solution of the invention may also contain one or more additional components such as a co-solubilizing agent (which may be the same as a solvent).
Suitable solvents and co-solubilizing agents are selected from, but are not limited to, aliphatic amides, e.g. N,N-dimethylacetamide, N-hydroxy-2-ethyl-lactamide and the like; alcohols, e.g. ethanol, benzyl alcohol and the like; glycols and polyalcohols, e.g. propylene glycol, glycerin and the like; esters of polyalcohols, e.g. diacetine, triacetine and the like; polyglycols and polyethers, e.g. polyethyleneglycol 400, propylene glycol methylethers and the like; and dioxolanes, e.g. isopropylidenglycerin and the like.
Further, according to the present invention, the stable, ready-to-use, liquid formulation of carmustine for parenteral administration does not comprise of any surfactant.
In a preferred embodiment of the present invention, carmustine is dissolved in a solvent system comprising polyethylene glycol and alcohol. In another preferred embodiment of the present invention, carmustine is dissolved in a solvent system comprising polyethylene glycol 400 and N,N-dimethylacetamide.
The pharmaceutical composition of the present invention, prepared by using polyethylene glycol 400 and N,N-dimethylacetamide shows any individual impurity present less than 1.0% whereas total impurities are well below the pharmaceutical^ acceptable limit of 2.0%.

Impurity A, which is well know with the carmustine formulation is well below the limit of 1.0%.
Further, according to the present invention, other optional pharmaceutical excepients such as buffers, pH adjusters, antioxidants, reducing agents, antimicrobial preservatives, stabilizing agents etc. can also be used in the said pharmaceutical preparation.
In another embodiment, the present invention provides a process for the preparation of a stable, ready-to-use, liquid pharmaceutical composition comprising carmustine suitable for parenteral administration. A generalized 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 solvents and co-solubilizing agents,
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. 0.2 micron 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 readily varied by one of ordinary skill in the art.

EXAMPLES
Example - 1: Preparation of ready-to-use parenteral composition of Carmustine
Composition:

Composition Qty per mL
Carmustine 12.5 mg
N,N-dimethylacetamide 0.33 mL
Polyethylene Glycol 400 0.67 mL
Preparation: A sterile, ready-to-use, liquid formulation of carmustine for parenteral administration was prepared as follows:
a) about 80% of the required N,N-dimethylacetamide was taken,
b) dispensed quantity of polyethylene glycol 400 was added under stirring and the solution was cooled to 2°C,
c) carmustine was added to the above mixture and stirred for 30 min,
d) the final volume was made up with the N,N-dimethylacetamide,
e) the solution was filtered through 0.22 um filter & filled in to type I amber glass vials, and
f) the vials were then plugged with suitable rubber stopper & sealed.
The formulation prepared in the above example was analysed for various parameters such as pH, Impurity A and total impurities; and the results are summarised in the below Table:

Sr.
No. Test Specification [Tentative] Initial 2-8°C

1 Month 2 Month 3 Month 6 Month
1. Description Pale yellow
coloured
solution Pale yellow
coloured
solution Pale yellow
coloured
solution Pale yellow
coloured
solution Pale yellow
coloured
solution Pale yellow coloured solution
2. pH(10%aq. sol.) Between 4.0 and 6.8 4.4 4.1 4.1 3.9 3.7
3. Identification by HPLC TheRT comparison in the Assay Test Complies Complies Complies Complies Complies
4. Related substances by HPLC

Impurity A NMT 1.0% *ND 0.08% 0.13% 0.20% 0.47%

Any unspecified impurity NMT 0.2% 0.01 % (RRT-0.84) 0.02 % (RRT-1.28) 0.01 % (RRT-0.32) 0.01 % (RRT-0.46) 0.02 % (RRT-0.95)

Total impurities NMT 2.0% 0.01% 0.1% 0.15% 0.21% 0.49%
5. % Assay by HPLC NMT 90.0% & NMT 110.0% of Labelled amount 101.8% 100.4% 99.0% 98.4% 97.5%
*ND: Not detected
Example -2: Preparation of ready-to-use parenteral composition of Carmustine Composition:

Composition Qty per mL
Carmustine 12.5 mg
N,N-dimethylacetamide 0.30 mL
Propylene Glycol 0.70 mL
Preparation: A sterile, ready-to-use, liquid formulation of carmustine for parenteral administration* was prepared as follows:
a) about 80% of the required N,N-dimethylacetamide was taken,
b) dispensed quantity of propylene glycol was added under stirring and the solution was cooled to 2°C,
c) carmustine was added to the above mixture and stirred for 30 min,
d) the final volume was made up with the N,N-dimethylacetamide,
e) the solution was filtered through 0.22 um filter & filled in to type I amber glass vials, and
f) the vials were then plugged with suitable rubber stopper & sealed.

Example -3: Preparation of ready-to-use parenteral composition of carmustine Composition:

Composition Qty per mL
Carmustine 12.5 mg
Citric acid USP 2.0 mg
Dehydrated Alcohol USP 270 mg
Polyethylene Glycol 400 USP 250 mg
Propylene Glycol USP 200 mg
Preparation: A sterile, ready-to-use, liquid formulation of carmustine for parenteral administration was prepared as follows:
a) about 80% of the required propylene glycol was taken,
b) dispensed quantity of polyethylene glycol 400 was added under stirring and the solution was cooled to 2°C,
c) dehydrated alcohol and citric acid was added to the above solution,
d) carmustine was added to the above mixture and stirred for 30 min,
e) the final volume was made up with the propylene glycol,
f) the solution was filtered through 0.22 um filter & filled in to type I amber glass vials, and
g) the vials were then plugged with suitable rubber stopper & sealed.
Example - 4: Preparation of ready-to-use parenteral composition of Carmustine Composition:

Composition Qty per mL
Carmustine 12.5 mg
Ascorbic acid USP 1.0 mg

Polyethylene Glycol 400 USP 1013.4 mg
Propylene Glycol USP 103.2 mg
Preparation: A sterile, ready-to-use, liquid formulation of carmustine for parenteral administration was prepared as follows:
a) about 80% of the required propylene glycol was taken,
b) dispensed quantity of polyethylene glycol 400 was added under stirring and the solution was cooled to 2°C,
c) ascorbic acid was added to the above solution,
d) carmustine was added to the above mixture and stirred for 30 min,
e) the final volume was made up with the propylene glycol,
f) the solution was filtered through 0.22 um filter & filled in to type I amber glass vials, and
g) the vials were then plugged with suitable rubber stopper & sealed.

We claim:
1. A stable, liquid pharmaceutical composition comprising carmustine and a solvent system.
2. A stable, liquid pharmaceutical composition of claim 1, wherein the composition is free of
surfactant.
3. The stable, liquid pharmaceutical composition of claim 1, wherein the composition is a ready
to use formulation.
4. The stable, liquid pharmaceutical composition of claim 1, wherein the solvent system for
carmustine is chosen from the group comprising of N,N-dimethylacetamide, N-hydroxy-2-. ethyl-lactamide, ethanol, benzyl alcohol, propylene glycol, glycerin, diacetine, triacetine, polyethylene glycol 400, propylene glycol, and mixtures thereof.
5. The stable, liquid pharmaceutical composition of claim 1, wherein the concentration of
carmustine is from 5 mg/mL to 20 mg/mL.
6. The stable, liquid pharmaceutical composition of claim 5, wherein the concentration of
carmustine is from 10 mg/mL to 15 mg/mL.
7. The stable, liquid pharmaceutical composition of claim 1, wherein the composition further
comprises one or more pharmaceutically acceptable excipients selected from the group comprising co-solubilizers, buffers, pH adjusters, antioxidants, reducing agents, antimicrobial preservatives, stabilizing agents, and mixtures thereof.
8. The stable, liquid pharmaceutical composition of claim 1, wherein the composition is suitable
for parenteral administration.
9. A method of preparation of the stable, liquid pharmaceutical composition of claim 1,
comprising the steps of:

a) preparing the solvent system by mixing the solvents and co-solubilizing agents,
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.