FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
Complete Specification
[See Sections 10 and rule 13]
Title: Stable palonosetron 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 a stable palonosetron injection comprising palonosetron or a pharmaceuticals acceptable salt thereof as active ingredient for preventing and/or reducing emesis. In particular, the present invention relates to a stable palonosetron injection, wherein the pH of the injection is less than 4. Further, the present invention relates to a process for the preparation of said stable palonosetron injection.
BACKGROUND OF THE INVENTION
Palonosetron is an emesis-inhibiting drug. Chemically Palonosetron is described as (3aS) - 2, 3, 3a, 4, 5, 6 - Hexa-hydro-2-[(S)-l-Aza-bicyclo [2.2.2] Oct - 3 - yl]2, 3, 3a, 4.-5.6-hexahydro-l-oxo-lHbenz[de]isoquinoline, and is preferably present as the monohydrochloride.
Emesis is a troubling consequence of cytotoxic therapy, radiotherapy, and postoperative environments that drastically affects the quality of life of people undergoing such treatments. A class of drugs referred to as 5-HT.sub.3 (5-hydroxytryptamine) receptor antagonists has been developed that treat such emesis by antagonizing cerebral functions associated with the 5-HT.sub.3 receptor. Drugs within this class include ondansetron, graniselron. alosetron, tropisetron. and dolasetron and palonosetron. These 5-HT.sub.3 antagonists are often supplied as oral tablets or oral elixirs or intravenous administration.
The clinical investigations concerning palonosetron injection have been reported in U.S. patent 5202333. These investigations have shown that the drug is an order of

magnitude more potent than most existing 5-HT.sub.3 receptor antagonists, has a surprising half-life of about 40 hours, and is effective to reduce delayed-onset nausea induced by chemotherapeutic agents. However, formulating palonosetron in liquid formulations has not proven an easy task, typically due to shelf-stability issues.
U.S. patents 7947724, 7947725 and 7960424 disclose an intravenous formulation of palonosetron injection as an Example in the specification:

Ingredients mg/ml
Palonosetron HC1* 0.05
Mannitol 41.5
EDTA 0.5
Trisodium citrate 3-7 .
Citric acid 1.56
Sodium hydroxide solution pH: 5.0 ±0.5
Hydrochloride acid solution

Water for injection Upto 1.0 ml
* Calculated as a free base.
However, it has been found that prior art formulations have certain difficulties. Such formulations are stable only in the pH range of 4.0 to 6.0.
Therefore, there exists a need for a palonosetron formulation with increased stability and thereby increased shelf life. There also exists a need for stable palonosetron injection with desired stability, wherein the pH of the injection is less than 4.

OBJECTS OF THE INVENTION
The primary object of the invention is to provide a stable palonosetron injection comprising palonosetron or a pharmaceutically acceptable salt thereof, for preventing and/or reducing emesis.
Another object of the invention is to provide a stable palonosetron injection comprising palonosetron or pharmaceutically acceptable salt thereof and at least one pharmaceutically acceptable excipient. wherein the pH of the injection is less than 4.
Another object of the invention is to provide a stable palonosetron injection with increased shelf-life that allows for prolonged storage.
Another object of the invention is to provide a process for the preparation of said stable palonosetron injection.
SUMMARY OF THE INVENTION
In a first embodiment, the invention relates to a stable palonosetron injection comprising palonosetron or a pharmaceutically acceptable salt thereof, for preventing and/or reducing emesis.
In another embodiment, the invention relates to a stable palonosetron injection comprising palonosetron or pharmaceutically acceptable salt thereof and at least one pharmaceutically acceptable excipient. wherein the palonosetron injection shows increased stability and the pH of the injection is less than 4.

In another embodiment, the invention relates to a stable palonosetron injection with increased shelf-life that allows for prolonged storage.
In another embodiment, the invention relates to process for the preparation of a stable palonosetron injection, wherein the pH of the injection is less than 4.
DETAILED DESCRIPTION
The present invention comprises a stable palonosetron injection comprising palonosetron or pharmaceutically acceptable salt thereof and pharmaceutically acceptable excipients. for preventing and/or reducing emesis.
In an embodiment, the present invention provides a stable palonosetron injection for preventing and/or reducing emesis comprising: a) from about 0.01 mg/ml to about 5 mg/ml palonosetron or a pharmaceutically acceptable salt thereof; and b) at least one pharmaceutically acceptable excipient. The preferred concentration of palonosetron is 0.05 mg/ml.
The inventors have further discovered that by adjusting the formulation's pH and/or excipients it is possible to increase the stability of palonosetron injections.
In another embodiment, the invention provides a stable palonosetron injection for preventing and/or reducing emesis comprising: a) palonosetron or a pharmaceutically acceptable salt thereof; and b) at least one pharmaceutically acceptable excipient, wherein the pH of the injection is less than 4.

[n a preferred embodiment, the stable palonosetron injection shows increased stability and thereby increased shelf-life in the pH range of 3.0 to 3.9.
Similarly, in another embodiment the invention provides a process for preparation of a stable palonosetron injection for preventing and/or reducing emesis comprising: a) palonosetron or a pharmaceutically acceptable salt thereof; and b) at least one pharmaceutically acceptable excipient, wherein the pH of the injection is less than 4.
There are many examples to those of skill in the art of suitable solutions to adjust the pH of any formulation. Two exemplary solutions are sodium hydroxide and hydrochloric acid solution, either of which could be used to adjust the pH of the stable palonosetron injection.
The pharmaceutically acceptable excipients include buffer(s), chelating agent(s) and tonicifying agent(s) and optionally other agents useful in the injection formulations.
According to the present invention, the process for the preparation of a stable palonosetron injection comprises: a) admixing palonosetron or a pharmaceutically acceptable salt thereof and b) at least one pharmaceutically acceptable excipient. wherein the pharmaceutically acceptable excipient comprises of a buffer, chelating agent and mannitol.
The buffer is preferab]y citrate buffer. In various embodiments, the citrate buffer can be in the form of citric acid and/or a salt of citric acid such as trisodium citrate. In various embodiments, the ranges of buffer concentration can be about 10 to about 40 millimoles, or preferably 15-30 millimoles.
The inventors have further discovered that the addition of mannitol and a chelating

agent can increase the stability of palonosetron formulation, wherein the pH of the said injectable formulation is less than 4.
The chelating agent is preferably EDTA. and, in various embodiments the chelating agent is present in a concentration of from about 0.005 to about 1.0 mg/ml or from about 0.05 mg/ml to about 1.0 mg/ml or from about 0.3 to about 0.7 mg/ml, or most optimally about 0,5 mg/ml.
In various embodiments, the mannitol (tonicifying agent) is present in a concentration of from about 10.0 mg/ml to about 80.0 mg/ml, from about 20.0 mg/ml to about 60.0 mg/ml, or preferably from about 40,0 to about 45.0 mg/ml.
Palonosetron injectable formulations shall be administered by any preferred route including intramuscular, intravenous or subcutaneous.
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.
Example 1 describes the formulation of a stable palonosetron Injection.
Example 2 indicates that Palonosetron HCl Injection is stable up to 6 months at accelerated conditions.
Example 3 indicates that Palonosetron HCI Injection is stable up to minimum period of 24 months at long-term storage conditions.

Example 1: Stable palonosctron Injection
The palonosetron injection described below (concentration: 0.05 mg/ml) was prepared from the following components:

Ingredients Concentration (mg/ml)
Palonosetron 0.05 mg/ml
Mannitol 41.5
Citric acid monohydrate 2.0
Sodium citrate 2.0
Disodium EDTA 0.5
NaOH (For pH adjustment) pH: 3.0 to 3.9
HC1 (For pH adjustment)

Water for injection q.s.
Brief manufacturing process:
1) Add required amount of water for injection in the vessel.
2) The desired amount of disodium EDTA was added and dissolved by stirring.
3) Then preferred amount of mannitol was added and dissolved by stirring.
4) Further the desired amount of citric acid monohydrate / sodium citrate was added and dissolved by stirring.
5) Then palonosetron HC1 was added in above solution and stirred to get dispersion.
6) The drug was solubilized by adding sodium hydroxide and/or hydrochloric acid and the pH value of the solution was adjusted in the range of 3.0 to 3.9.
7) The final volume was adjusted with water for injection and stir for few minutes.
8) Filter the solution with 0.2 u filter and fill in the vials and then subject to terminal sterilization.

Example 2: Stability Data of Palonosetron HCI Injection (0.05 mg/ml)

Product Palonosetron Hydrochloride Injection 0.05 m«/ml
Label Claim: Each ml contains:
Palonosetron Hydrochloride equivalent to
Palonosetron ... 0.05 mg
Water for injection Ph. EurAISP ... q.s. to 1 ml
Pack Details 6 ml USP Type 1 Clear glass vials & stoppered with 20 mm Chlorobutyl rubber stopper
Fill volume 5.50 ml ±0.2 ml
Test Parameters Initial 40°± 2°C / 75+5 % RH (Inv)6 Months
Description * *
pH 3.4 3.5
Assay of Palonosetron (By HPLC) 99.8 % 08.4 %
Related substances (By HPLC)
Carboxamide BQL ND
Dehydroamide BQL 0.08%
(3aR;3S)-Diastereoisomer 0.08% 0.07%
Palonosetron N-Oxide ND ND
Single maximum Unknown impurity ND BQL
Total impurities 0.08% 0.2%
Color & clarity of solution ** **
Particulate matter 181 42

00 02
* A clear colorless solution, practically free from foreign particles
** Solution is clear and colorless as purified water
Inv - Inverted
BQL - Below quantification level, Limit of quantification for Carboxide is 0.044%,
Limit of quantification for Dehydroamide is 0.044%
ND-Not detected

Example 3: Stability Data of Palonosetron HCI Injection (0.05 mg/ml)

Product Palonosetron Hydrochloride Injection 0.05 mg/ml
Label Claim: Each ml contains:
Palonosetron Hydrochloride equivalent to
Palonosetron ... 0.05 mg
Water for injection Ph. Bur./USP ... q.s. to 1 ml
Pack Details 6 ml USP Type I Clear glass vials & stoppered with 20 mm Chlorobutyl rubber stopper
Fill volume 5.50 ml ±0.2 ml
Test Parameters Initial 25°± 2°C/60±5 % RH (Inv) 12 Month 25°± 2°C/60±5 % RH (Inv) 24 Month
Description * * *
pH 3.4 3.4
Assay of Palonosetron (By HPLC) 99.8% 98.8% 98.8%
Related substances (By HPLC)
Carboxamide BQL ND ND
Dehydroamide BQL 0.08% ND
(3aR, 3S) -Diaslereoisomer 0.08% 0.07% 0.07%
Palonosetron N-Oxide ND ND ND
Single maximum Unknown impurity ND BQL ND
Total impurities 0.08% 0.1% 0.07%
Color & clarity of solution ** ** **
Particulate matter 181 30 69

00 02 00
* A clear colorless solution, practically free from foreign particles
** Solution is clear and colorless as purified water
Inv - Inverted
BQL - Below quantification level. Limit of quantification for Carboxide is 0.044%,
Limit of quantification for Dehydroamide is 0.044%
ND-Not detected

We claim:
1. A stable palonosetron injection comprising palonosctron or pharmaceutically
acceptable salt thereof and at least one pharmaceutically acceptable excipient,
wherein the pH of the injection is less than 4.
2. The stable palonosetron injection of claim 1 comprising:
a) from about 0.01 mg/ml to about 5 mg/ml palonosetron or a pharmaceutically acceptable salt thereof; and
b) at least one pharmaceutically acceptable excipient.
wherein the pH of the injection is less than 4.
3. The stable palonosetron injection of claim 1 comprising:
a) from about 0.01 mg/ml to about 5 mg/ml palonosetron or a pharmaceutically acceptable salt thereof; and
b) the pharmaceutically acceptable excipient selected from the group of buffer(s). chelating agent(s) and tonicifying agent(s) and optionally other agents,
wherein the pH of the injection is less than 4.
4. The stable palonosetron injection of claim 1 comprising:
a) from about 0.01 mg/ml to about 5 mg/ml palonosetron or a pharmaceutically acceptable salt thereof; and
b) the pharmaceutically acceptable excipients comprising citrate buffer, Disodium EDTA and mannitol,
wherein the pH of the injection is less than 4.
5. A stable palonosetron injection comprising:
a) Palonosetron,
b) mannitol.

c) Citrate buffer.
d) Disodium EDTA.
e) optionally pH adjustment agents.
f) Water for Injection,
wherein the pH of the injection is less than 4.