FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
Complete Specification [See Sections 10 and rule13]
Title: Stable methotrexate injection. Applicant: (a)Astron Research Limited
(b) Nationality: Indian
(c) 10th Floor. Premier House. Bodakdev. Opp. Gurudwara. Sarkhej - Gandhinagar Highway ,
Ahmedabad-380054 Gujarat. India.
The following specification describes the invention and the manner in which this is to be performed:

FIELD OF THE INVENTION
The present invention relates to stable methotrexate injection containing methotrexate or a pharmaceutically acceptable salt thereof as active ingredient. m particular, the present invention relates to stable methotrexate injection, wherein the methotrexate is present in a pharmaceutical])' acceptable solvent at a concentration between 60 mg/ml to 90 mg/ml. The invention also relates to a ready-to-use pre-filled syringe.
BACKGROUND OF THE INVENTION
Methotrexate (MTX) is a folic acid antagonist. Chemically MTX is described as N-{4-[(2,4-diamino-6-pteridinylmethyl)methylamino]-benzoyl}-L-glutamic acid. Due to its effectiveness as a cytostatic agent, methotrexate has long been used predominantly in the field of oncology. The effectiveness of methotrexate in the treatment of psoriasis is known in the art.
Rheumatoid arthritis is usually therapeutically treated with fast-acting pain-relieving and short-term anti-inflammatory substances. However, these substances do not influence the actual course of the disease. Over the years, methotrexate has become the gold standard in the treatment of rheumatoid arthritis. Contrary to chemotherapy in the treatment of tumors, methotrexate as a basic therapeutic in the treatment of rheumatoid arthritis is dosed significantly lower, sometimes up to 1000 times lower. which is why the anti-rheumatic therapy is also referred to as "low-dosage methotrexate therapy". Usually the dosage range of 5.0 mg upto 40.0 mg per week is common for anti-rheumatic therapy.

In principle, methotrexate can be administered orally and parenterally. Due to its more advantageous bioavailability, parenteral application is superior to oral application. Cytostatics suitable for parenteral administration are usually prepared by dissolving the active substance in a suitable solvent, using a specific amount of active substance for each individual patient. However, handling cytostatics and preparing cytostatics-containing medicaments is not without challenges and subject to strict legal restrictions. Hence, ready-to-use pre-filled syringes were developed in order to eliminate this step of drawing up a syringe. These ready-to-use pre-filled syringes allow use by the physician, the medical staff, or self-application by patient.
Ready-to-use pre-filled syringe for parenteral administration containing methotrexate at a concentration of up to 25 mg/ml in a pharmaceutical!)' acceptable solvent (trade names: Lantarel.RTM. of the company Wyeth. Metex.RTM. of the applicant) is known from the prior art for the treatment of rheumatoid arthritis. Further. Ready-to-use pre-filled syringe for methotrexate at a concentration of 50 mg/ml is available in Europe (trade name: Metoject.RTM. of the company Medac).
However, it has been found that such formulations have certain difficulties. In the prior art formulations with lower concentration like 25 mg/ml and 50 mg/ml. the volume to be injected is higher which will result in more pain at the site of injection. There is therefore a need for pharmaceutical formulations of methotrexate, which upon subcutaneous administration to the patients results into less pain, which ultimately leads to a high degree of patient compliance. Thus the present invention relates to a higher concentration, which will result in less volume and hence less patient discomfort.

OBJECTS OF THE INVENTION
The primary object of the invention is to provide stable methotrexate injection, wherein the methotrexate is present in a pharmaceutical!)' acceptable solvent at a concentration between 60 mg/ml to 90 mg/ml.
Another object of the invention is to provide a ready-to-use pre-filled syringe containing a pharmaceutical formulation of methotrexate in a pharmaceutical!}' acceptable solvent at a concentration between 60 mg/ml to 90 mg/ml.
Another object of the invention is to provide a ready-to-use pre-filled syringe containing a pharmaceutical formulation of methotrexate in a pharmaceutically acceptable solvent at a concentration between 60 mg/ml to 90 mg/ml. administered by intravenous, intramuscular or subcutaneous injection for the treatment of inflammatory autoimmune diseases, in particular rheumatoid arthritis.
SUMMARY OF THE INVENTION
In a first embodiment, the invention relates to a stable methotrexate injection, wherein the methotrexate is present in a pharmaceutically acceptable solvent at a concentration between 60 mg/ml to 90 mg/ml.
In another embodiment, the invention relates to a ready-to-use pre-filled syringe containing a pharmaceutical formulation of methotrexate in a pharmaceutically acceptable solvent at a concentration between 60 mg/ml to 90 mg/ml.

In another embodiment, the invention relates to a ready-to-use pre-filled syringe containing a pharmaceutical formulation of methotrexate in a pharmaceutically acceptable solvent at a concentration between 65 mg/ml to 85 mg/ml. administered by intravenous, intramuscular or subcutaneous injection for the treatment of inflammatory autoimmune diseases, in particular rheumatoid arthritis.
DETAILED DESCRIPTION
According to the present invention, medicaments or pharmaceutical solution formulations are provided which comprise methotrexate at a concentration between 60 mg/ml to 90 mg/ml in a pharmaceutically acceptable solvent. In a preferred embodiment, the methotrexate is present in the medicament at a concentration between 65 mg/ml to 85 mg/ml. In an especially preferred embodiment, the methotrexate is present in the medicament at a concentration of 75 mg/ml in a pharmaceutically acceptable solvent.
All solvents which are pharmaceutically acceptable and are not incompatible with the active substance or other possible components of the medicament or the pharmaceutical solution formulation can be used as the pharmaceutically acceptable solvent. According to the present invention, especially suitable solvents include water, in particular water for injection, comprising isotonization additives, in particular isotonic sodium chloride solution. Examples o\' isotonization additives include soluble salts (sodium chloride, potassium chloride), sugars (glucose, lactose), sugar alcohols (mannilol. sorbitol) as well as combinations of these additives. The osmolality of the methotrexate injection is 250-350 milliosmoles/kg.

In addition to isotonization additives, the medicament according to the present invention can comprise additives common in the field of pharmaceutical solution formulations. In particular, the medicament according to the present invention can comprise additives such as buffers (acetate, phosphate, citrate buffers). In an especially preferred embodiment, the pH value of the medicament according to the present invention is between 7 and 9. Further, the injection can optionally comprise pH-adjusting agents like sodium hydroxide.
The medicaments according to the present invention are directed to the treatment of inflammatory autoimmune diseases. The medicaments of the present invention are especially preferred for the treatment of rheumatoid arthritis.
The medicaments of the present invention are administered parenterally. In particular, the medicaments are administered by intravenous, intramuscular or subcutaneous injection. According to a preferred embodiment of the present invention, the medicament is provided by subcutaneous self-administration by the patient (self-application). In the case of rheumatism, self-application has advantage that the weekly doctor's visit is no longer necessary.
In a preferred embodiment of the present invention, the medicament according to the present invention is contained in an injection device for a single application, in particular a ready-to-use pre-filled syringe. An injection device for a single application according to the present invention preferably contains a dose of the active substance methotrexate of 5 mg to 40 mg. The volume of the liquid necessary to provide the desired dose, which has to be contained in the injection device for a single application, depends on the concentration of the active substance solution and is obvious to the person skilled in the art. The fill volume can be 0.05 ml to 0.70 ml. and depending upon the requirement and feasibility it can be varied within limits.

Comparison of volume with respect to dose strength of formulation:

Dose Strength 25 mg/ml 60 mg/ml 75 mg/ml 90 mg/ml
Volume for 5 mg dose 0.2 mi 0.083 0.067 0.055
Volume for 40 mg dose 1.6 ml 0.667 0.533 0.444
The medicaments provided by the present invention contain methotrexate with a once weekly dosing. It can be expected that this has a positive impact on patient compliance. Thus, in a preferred embodiment, the present invention provides a ready-to-use pre-filled syringe containing a pharmaceutical solution formulation of methotrexate at a concentration of 75 mg/ml in a pharmaceutically acceptable solvent.
Preferably, the ready-to-use pre-filled syringe according to the present invention is designed such that it is suitable for the subcutaneous application of the active substance solution, which can be achieved by providing a hypodermic needle. Ready-to-use pre-filled syringes with suitable designs for self-administration by the patient himself are known in the prior art.
Example 1:
In the following section embodiments are described by a way of examples to illustrate the process of invention. However, these are not intended in any way to limit the scope of present invention.
A) Stable methotrexate Injection:
The methotrexate injection described below (concentration: 75 mg/ml) was prepared from the following components:

Ingredients
Concentration (mg/ml)
Methotrexate 60 - 90
Sodium chloride q.s.
Sodium hydroxide (For pH adjustment) q.s.
Water for injections q.s.
Brief manufacturing process:
1) For preparing the injection (Example 1). approximately 70% water for injection was taken in the vessel.
2) The desired amount of sodium chloride was added and dissolved by stirring.
3) Add required amount of methotrexate in above solution and stir to get dispersion.
4) The drug was solubilized by adding sodium hydroxide and pH value of the solution was adjusted to a value in the range of 7 to 9 (preferably pH of 8.3).
5) The final volume was adjusted with water for injection and stirred for 5 min.
6) Filter the solution with 0.2 u filter and fill in clear glass ready-to-use pre-filled syringe.
Example 2:

Ingredients Concentration (mg/ml)
Methotrexate 75.0
Sodium chloride 1.5
Sodium hydroxide (for pH adjustment) q.s to pH 8.4
Water for injection q.s. to 1 ml
Nitrogen q.s.
The stable methotrexate injection of Example 2 can be prepared by the manufacturing process as described in the Example 1.

Table: Stability data of Methotrexate Injection BP 75 mg/ml (30 mg/0.4 ml) PFS
Product: Methotrexate Injection BP 75 mg/ml (30 mg/0.4 ml) PFS (Batch size: 500 ml)
Condition Initial 40±2°C/75±5%RH
Duration
1 M 2 M 3 M
Tests Limit
Characteristics Clear Yellow to Brown solution Yellowish Clear solution Yellowish Clear solution Yellowish Clear solution Yellowish Clear solution
Assay 95.0%- 110.0% 101.6% 101.2% 98.7% 100.4%
Alkalinity Between 7.0 and 9.0 8.47 8.25 8.26 8.57
Related Substances (%)
Methopterin (Impurity C) NMT 3.0% 0.210% 0.689% 1.190% 1.665%
Other single known impurity NMT 0.2% 0.025% 0.034% 0.043% 0.105%
Single unknown impurity NMT 0.2% 0.047% 0.042% 0.072% 0.038%
Total impurities other than Impurity C NMT 1.0% 0.133% 0.1 84% 0.223% 0.418%
Tabic: Stability data of Methotrexate Injection BP 75 mg/ml (7.5 mg/0.1 ml) PFS
Product: Methotrexate Injection UP 75 m«/ml (7.5 mg/0,1 ml) PFS (Batch size: 500 ml)
Condition Initial 40±2°C/75±5%RH
Duration
1 M 2 M 3 M
Tests Limit
Characteristics Clear Yellow to Brown solution Yellowish Clear solution Yellowish Clear solution Yellowish Clear solution Yellowish Clear solution
Assay 95.0%- 1 10.0% 101.6% 101.2% 99.5%i 99.9%
Alkalinity Between 7.0 and 9.0 8.47 8.20 8.00 8.25
Related Substan ces (%)
Methopterin (Impurity C) NMT 3.0% 0.210% 0.691% 1.203% 1.637%
Other single known impurity NMT 0.2% 0.023% 0.027% 0.038% 0,1 07%
Single unknown impurity NMT 0.2% 0.047% 0.040% 0.045% 0.041%
Total impurities other than Impurity C NMT t.0% 0.133% 0.1 65% 0.225% 0.442%

The imparity profile results obtained by stability studies indicate that methotrexate injection is stable for at least three months.

We claim:
1. A stable methotrexate injection comprising a pharmaceutical formulation of methotrexate in a pharmaceutically acceptable solvent at a concentration between 60 mg/ml to 90 mg/ml.
2. The stable methotrexate injection of claim 1. wherein the injection comprises a pharmaceutical formulation of methotrexate in a pharmaceutically acceptable solvent at a concentration between 65 mg/ml to 85 mg/ml.
3. The stable methotrexate injection of claim 1. wherein the concentration of
methotrexate is 75 mg/ml.
4. The stable methotrexate injection of claim 1. wherein the injection is administered
through intravenous, intramuscular or subcutaneous route.
5. The stable methotrexate injection of claim 1, wherein the fill volume of the injection is from 0.05 ml to 0.70 ml.
6. The stable methotrexate injection of claim 1. wherein the pH of the injection is between 7 and 9.
7. The stable methotrexate injection of claim 1. wherein the injection can be administered as a ready-to-use pre-filled syringe.
8. The stable methotrexate injection of claim 1. wherein the injection comprises a pharmaceutical formulation of methotrexate in water for injection, optionally with isotonization additives.

9. The stable methotrexate injection of claim 1. wherein the injection comprises a pharmaceutical formulation comprising methotrexate, sodium chloride, sodium hydroxide and water for injection.