Drug – bio-affecting and body treating compositions – Designated organic active ingredient containing – Having -c- – wherein x is chalcogen – bonded directly to...
Reexamination Certificate
2000-05-03
2001-10-23
Jones, Dwayne C. (Department: 1614)
Drug, bio-affecting and body treating compositions
Designated organic active ingredient containing
Having -c-, wherein x is chalcogen, bonded directly to...
Reexamination Certificate
active
06306894
ABSTRACT:
CROSS-REFERENCE TO RELATED FOREIGN APPLICATION
This application claims priority under 35 USC 119 to Australian Patent No. 6074 filed Nov. 27, 1992.
BACKGROUND OF THE INVENTION
Paclitaxel is a compound extracted from the bark of a western yew,
Taxus brevifolia
and known for its antineoplastic activity. It is described for example in The Merck Index, Eleventh Edition 1989, monograph 9049.
In 1977, paclitaxel was chosen for development as an antineoplastic agent because of its unique mechanism of action and good cytotoxic activity against IP implanted D16 melanoma and the human X-1 mammary tumor xenograft. Paclitaxel is believed to function as a mitotic spindle poison and as a potent inhibitor of cell replication in vitro. Other mitotic spindle points (colchicine and podophyllotoxin) inhibit microtubule assembly. Paclitaxel employs a different mechanism of action since it appears to shift the equilibrium of polymerimization/depolymerization toward polymer assembly and to stabilize microtubules against depolymerization under conditions which would cause rapid disaggregation of microtubules. The interference with the polymerization/depolymerization cycle in cells appears to interfere with both the replication and migration of cells.
After extensive preclinical screening in mouse tumor models, paclitaxel entered clinical trials in 1983. Over the past few years, paclitaxel has demonstrated good response rates in treating both ovarian and breast cancer patients who were not benefitting from vinca alkaloid or cisplatin therapy. It has also shown encouraging results in patients with other types of cancer including lung, melanoma, lymphoma, head and neck.
For further information, reference may be made to the U.S. National Cancer Institute's Clinical Brochure for Taxol, revised July 1991, and papers presented at the Second National Cancer Institute Workshop on Taxol and Taxus held in Alexandria, Va. USA on Sep. 23-24, 1992.
BRIEF DESCRIPTION OF THE INVENTION
It is a disadvantage of the known formulation that the paclitaxel therein degrades, with the result that the shelf life of the formulation is unsatisfactory, and there is therefore a need for a paclitaxel solution of improved stability.
Accordingly, in a general aspect the invention provides a solution containing paclitaxel, cremophor EL™ and ethanol, characterized in that the pH of the solution has been adjusted into the range 1 to 8 by addition of an acid.
Acids in the form of powders, for example citric acid, are preferred over those which contain water, for example sulfuric acid. The most preferred acid for use in accordance with the present invention is citric acid, but a wide range of acids may be used including the following:
Citric acid—monohydrous
Citric acid—anhydrous
Citric acid—hydrous
Acetic acid
Formic acid
Ascorbic acid
Aspartic acid
Benzene sulphonic acid
Benzoic acid
Hydrochloric acid
Sulphuric acid
Phosphoric acid
Nitric acid
Tartaric acid
Diatrizoic acid
Glutamic acid
Lactic acid
Maleic acid
Succinic acid
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
Due to its limited solubility in water, Paclitaxel is usually prepared and administered in a vehicle containing cremophor EL™ (a polyethoxylated castor oil which acts as a solubilizer) and ethanol. A commercially available solution supplied by Bristol-Myers Squibb (BMS) is formulated with these components and has a pH of 9.1.
As indicated above, the invention essentially teaches addition of an acid to a paclitaxel formulation to adjust its pH into the range 1 to 8, preferable 5 to 7.
In a preferred procedure adopted by the applicant, which it will be clearly understood is non-limiting, the following steps were carried out:
Mixing Instructions
Solution 1
Citric acid was dissolved in absolute alcohol, using a ratio of 8 mls of absolute alcohol to 1 gram of citric acid, and the solution was stirred for fifteen (15) minutes.
Solution 2
Cremophor EL was weighed out into the main mixing vessel.
Solution 3
Solution 1 was added to solution 2, and the container used for solution 2 was washed with a minimum quantity of absolute alcohol to ensure complete transfer of the citric acid. Solution 3 was mixed and bubbled with nitrogen for at least 15 minutes. The paclitaxel was weighed out and slurried using absolute alcohol, using a ratio of 8 ml of absolute alcohol to 1 gm of paclitaxel. The slurried paclitaxel was added to solution 3 and the slurrying vessel was washed with a minimum quantity of absolute alcohol. Solution 3 was adjusted to 75% of required volume using absolute alcohol, and thoroughly stirred for at least 45 minutes until completely dissolved. Once completely dissolved, the volume was checked and made up as necessary with absolute alcohol and the final solution stirred for 5 minutes.
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Carver David
Elliott Robyn
Ewald Hernita
Handreck Paul
Prout Timothy
Jones Dwayne C.
NaPro BioTherapeutics, Inc.
Saliwanchik Lloyd & Saliwanchik
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