CA2423884A1

CA2423884A1 - Improved paclitaxel-based antitumor formulation

Info

Publication number: CA2423884A1
Application number: CA002423884A
Authority: CA
Inventors: Maurizio Zenoni; Simone Maschio
Original assignee: ACS Dobfar SpA
Current assignee: Abraxis Bioscience LLC
Priority date: 2002-03-29
Filing date: 2003-03-28
Publication date: 2003-09-29
Also published as: MXPA03002544A; KR20030078740A; AU2003200926A1; NO340395B1; ITMI20020680A1; US20030187062A1; NZ524604A; JP2003300877A; US20070020337A1; CN1935121A; ZA200302039B; IL154761A0; ITMI20020680A0; NO20031447L; EP1348430A1; BR0300826A; RU2003108822A; NO20031447D0

Abstract

Antitumor formulation based on nanoparticles of paclitaxel and human serum al-bumin as obtained by the addition of a biocompatible acid to an aqueous albumin solution before this is mixed with paclitaxel during the nanoparticle production process, the injectable solutions of this formulation having a pH between 5.4 and 5.8 and having stability and inalterability with time.

Description

IMPROVED PACLITA%EL-EASED ANTITUMOI2 F°ORMULATI011f The present invention relates to an antitumor formulation based on pacli-taxel and albumin nanoparticles able to give injectable reconstituted aqueous mixtures having high inalterability with time.
Paclitaxel is a natural substance well known in literature, with important antitumor activity. Its poor water solubility makes it difficult to administer to man, for which reason various systems have been developed to render it injectable.
Bristol Myers Squibb (BMS) have conceived and patented a composition, known by the name of TAXOLO, in which the paciitaxel is emulsified with cremo-phor which induces various side effects in the patient (Lorenz et al., Agents Action 7, 63-67 ( 1987); Weiss et al., J. Clin. Oncol. 8, 1263 ( 1990)). The BMS
formulation also involves lengthy administration times due to the dilution of the active princi-ple.
To obviate the described drawbacks, BMS have patented (EP-A-0584001, EP-A-0783885, EP-A-0783886, US 5641803, US 5670537) formulations of TAXOL~
with the same dose of paclitaxel but with other excipients able to prevent strong anaphylactic reactions. However in all cases patient administration must be ef fected very- slowly, over a period of about 3 hours.
To prevent the side effects of TAXOLO, the cremophor was replaced with human serum albumin (HSA) in view of its biocompatibility and its considerable capacity to bind to the paclitaxel (Kumar et al., Res. Comm. in Chem. Path, and Pharm., 80 (3), 337-343 (1993); Paal et al., Eur. J. Biochem. 268, 2187-2191 (2001)). The property of HSA to form microspheres containing active principles dis-solved in organic solvents insoluble in water (Kramer et al., J. Pharm. Sci.
63, 1646-1647 (1974); Grinstaff and Suslick, J. Am. Chem. Soc. 112, 7807-7809 (1990); Grinstaff and Suslick, Polym. Prepr. 32, 255-256 (1991)) has also enabled the development of systems for administering paclitaxel in higher concentrations than with TAXOLO.
Injectable nanoemulsions of paclitaxel and HSA can be obtained by known ultrasonication, high pressure homogenization and microfluidization techniques (Alleman et al., Eur. J. Pharm. Biopharm. 39 (5), 173-191 (1993)).
On the basis of these elements and by using the aforestated ultrasonication and high pressure homogenization techniques, the American company VivoRx _2_ Pharmaceuticals Inc. has developed the formulation CAPXOL~R1 containing pacli-taxel and HSA.
In US 5439686, US 5498421, US 5560933 and the corresponding WO
94/ 18954, VivoRx claims microparticles of paclitaxel and HSA prepared using ul-trasonication techniques, to give particles of mean size (MPS) < IO microns.
The preparation methods described in these patents cannot be used on an industrial scale, and moreover the microparticles thus obtained have too high an MPS, which makes them unsuitable and unusable for administration to patients.
This was well known to the said VivoRx, which then in US 5916596 and US
6096331 and in WO 98/ I4I74 and WO 99/001 I3 described and claimed sterile nanoemulsions of paclitaxel and HSA obtained by reconstituting with sterile aque-ous 0.9% NaCl solution lyophilized powders with MPS < 0.2 microns. These nanoemulsions, which are obtained using high pressure homogenization, as de-scribed in the cited patents, are stated 1:o have high stability, where the term "stability" means that the MPS is constant with time and that nanoparticle precipi-tation is absent (US 6096331, Ex. 11).
Using maximum care, the present applicants have several times reproduced the examples of the aforestated patents, in particular Examples 1, 5 and 6 of US
5916596, without ever obtaining the result specified in the examples and claimed in the patent. Having prepared the mixtures as described, then processing them with an Avestin homogenizer within the pressure range recommended in US
5916596, nanoemulsions at pH=6.7 were obtained which, when evaporated in a rotavapor as reported in the said patent, always provided nanoemulsions with MPS
of about 0.2 microns (increase of MPS > 0.02 microns after evaporation) which are poorly stable in their formulations in injectable physiological solutions (increase in MPS of about 0.05 microns and tendency to sediment in about 12 hours) and diffi-cult to filter through 0.22 microns filters for their sterilization, in contrast to that stated in the said patent, The present applicants have made the most careful attempts to effect filtra-tion with the membranes described in US 5916596, but these attempts have al-ways failed, with clogging of the filters and paclitaxel yields always < 30%, in con-trast to the 70-100% declared. Moreover the stability (evaluated in accordance with the teachings of Example 11 of US 6096331) of the products prepared by the method just described, then lyophilized and reconstituted as reported in US

5916596 and US 6096331 has never reached 24 hours (hence much less than the 72 hours declared in the patents).
The main object of tl-~e present invention is therefore to provide an antitumor formulation consisting of nanoparticles of paclitaxel and human serum albumin, which with a physiological solution enables injectable reconstituted mixtures to be formed in which said particles have a stability (in the aforestated sense) consid-erably greater than that possible in the known art, and specifically a stability ex-ceeding 24 hours.
This and further objects are attained by a formulation consisting of a lyophi-lized powder of nanoparticles of paclitaxel and human serum albumin, in which the paclitaxel is present in a quantitity between 1% and 20% and the albumin between 60% and 98%, the percentages being by weight and the mean nanoparticle size being less than 0.2 microns, characterized in that said lyophilized powder contains between 1% and 20% by weight of biocompatible salts obtained by salification of at least one biocompatible acid or due to the presence of at least one biocompatible acid buffer substance, the acid or the buffer substance being present in a quantity such that the pH of a reconstituted aqueous injectable mixture of the powder is between 5.4 and 5.8.
The presence of the salts is due to the fact that an acid buffer substance is (as chemists well know) formed by an acid and a salt thereof and that some basic groups present in albumin are salified by the acids, therefore providing a mixture having a pH lower than a typical pH of albumin, i.e. 6.79-6.89 according to Merck Index, 13th Ed. page 1519.
Experiments have shown that if use is made of an acid buffer substance (such as a mixture of citric acid and sodium citrate), the results are not so good as with the use of the acid alone (citric acid or other biocompatible acid), as far as the abovementioned stability is concerned.
Obviously, the pH of the lyophilized powder can be easily measured after water has been added to form an aqueous mixture with it. The acidic nanoparticles have been studied showing that also water is present therein: the amount of water in the powder is up to 5% (w/w), usually about 2% to 4.5% (w/w). As a conse-quence, even the above mentioned nanoparticles containing water form part of the present invention.

The invention also relates to injectable reconstituted aqueous mixtures of such formulations, in which the paclitaxel is present at a concentration between 0. l and 3 mg/ml, preferably between 0.5 and 2.5 mg/ml.
The formulations of the invention may be obtained by mixing a sterile aque ous solution of human serum albumin (HSA) with a sterile solution of paclitaxel and treating this mixture in accordance with the teachings of the aforesaid Vivorx patents, but differing from such teachings in the fact that to the aqueous HSA
so lution, before it is mixed with paclitaxel, at least one biocompatible acid or acid buffer substance is added in a quantity sufficient to bring the pH of the solution to between 5.4 and 5.8, preferably between 5.5 and 5.7.
The biocompatible acids may be chosen from the group consisting of HCl, citric acid, phosphoric acid, acetic acid, biocompatible organic and inorganic acids.
The same formulations may be obtained also by a process according to which an aqueous mixture containing paclitaxel and albumin at a temperature between 0°C and 40°C is subjected to homogenization treatment at high pressure between 9000 and 40000 psi, to give a nanoemulsion which is frozen between 20°C and -80°C and is finally lyophilized by heating at a temperature between +20°C and +35°C, wherein said aqueous mixture is obtained under sterile condi tions by dissolving said albumin in sterile water to a concentration between 2% and 3% (w/v), then adding to said albumin solution between 2% and 4% (v/v) of chloro-form and then paclitaxel in sterile powder form in a quantity between 5.40%
and 15.0%, preferably between 5.60% and 13.7%, by weight on the weight of the albu-min present in the solution, at least one biocompatible acid or acid buffer sub-stance being added to said albumin solution before adding the paclitaxel in a quantity sufficient to bring the pH of the mixture to between 5.4 and 5.8, preferably between 5.5 and 5.7.
It may be noted that the use of paclitaxel in sterile powder form in the latter process not only greatly simplifies the plant itself and the process compared with the known art and enables the time required to complete the mixing of the various components before the homogenization treatment to be considerably shortened, but also enables better final yields to be obtained and simplifies the conditions to be observed in order to obtain the desired sterile lyophilized powders.
The results obtained with the use of the formulations according to the pres-ent invention are totally unexpected and surprising, because they are in contrast to the teachings of the art which provides for the use of HSA solutions of pH
values resulting from the dilution of injectable solutions of said albumin complying with FDA specifications, hence at pH=6.9~0.5 (see Examples 1, 5 and 6 of US
5916596).
In contrast to the teachings of the known art, it has been discovered that at pH
values between 5.4 and 5.8 a stability of greater than 24 hours can be obtained for the reconstituted lyophilized products.
To clarify the understanding of the characterise=ics of the present invention, some non-limiting examples of its implementation will now be described.

Preparation of a for~nulatioaa with C1 and paclitaxel dissolved in cloro-form An injectable aqueous 25% (w/v) HSA solution in accordance with FDA
specifications (pH=6.9~0.5) is diluted to 3% (iv/v) with sterile demineralized water, the pH being corrected to 5.6 with 1M HCl which salifies some basic groups pres-ent in albumin. 40 ml of said solution, previously sterilized, are mixed with 1.2 ml of a sterile solution of paclitaxel (59.0 mg/ml) in CHCIs> after which the mixture is processed in a homogenizer (suitably sterilized) at high pressure (9000-40000 psi) until a nanoemulsion (MPS < 0.2 microns) is obtained, this being frozen to -25°C
and lyophilized for 60 hours under sterile conditions, while raising the temperature to +20°C.
The powder obtained, containing 4.25 % (w/w) of paclitaxel and 3.6 (w/w) of water, is reconstituted with an aqueous 0.9% NaCI solution to a paclitaxel concen-tration of 2 mg/ml. The formulation obtained has an MPS of 0.16 microns, pH=5.6, and a stability > 24 hours.
Equivalent results were obtained by using phosphoric acid instead of HCl.

Preparation of a forxaaaalation with citric acid and paclitaxel dissolved in cloroforan An injectable aqueous 25% (w/v) I--1SA solution in accordance with FDA
specifications (pH=6.9~0.5) is diluted to 2.5% (w/v) with sterile demineralized wa-ter, the pH being corrected to 5.5 with sterile citric acid which salifies some basic groups present in albumin. 60 ml of said solution are mixed with 1.7 ml of a sterile solution of 60.0 rng/ml of paclitaxel in CHCl3, after which the mixture is processed in a homogenizer (suitably sterilized) at high pressure (9000-40000 psi) until a nanoemulsion (MPS < 0.2 microns) is obtained, this being rapidly frozen to -40°C
and lyophilized for 55 hours under sterile conditions, ~while raising the temperature to +35°C..
The powder obtained, containing 5.2% of paclitaxel and 4.9% (w/w) of water, is reconstituted with an aqueous 0.9% NaCI solution to a paclitaxel concentration of 2 mg/ml. The formulation obtained has an MPS of 0.17 microns, pH=5.5, and a stability > 24 hours.

Preparation of a formulation with ICI arid paclitaxel dissolved in cloro-form An injectable aqueous 25% HSA solution in accordance with FDA specifications is diluted to 3% (w/v) with sterile demineralized water, the pH being corrected to 5.6 with 1M HCl which salifies some basic groups present in albumin. 60 ml of said solution, suitably sterilized, are mixed with 1.5 ml of a sterile solution of 75 mg/ml of paclitaxel in CHCIs, after which the mixture is processed in a homogenizer (suitably sterilized) at high pressure (9000-40000 psi) until a nanoemulsion (MPS <
0.2 microns) is obtained, this being frozen to -50°C and lyophilized for 50 hours under sterile conditions, while raising the temperature to +30°C.
The powder obtained, containing 4.41% of paclitalYel and 3.8% (Tu/w) of wa-ter, is reconstituted with an aqueous 0.9% NaCI solution to a paclitaxel concentra-tion of 2.5 mg/m1. The formulation obtained has an M:PS of 0.175 microns, pH=5.6, and a stability > 24 hours.
By repeating the same procedure but without adding HCl and hence working at about pH 6.5, a formulation is obtained with an MPS of 0.24 microns and a stability of about 10 hours.

Preparation of a formulation with citric acid from a paclitaxel solution An injectable aqueous 25°ro (w/v) z-iSA solution in accordance with FDA
specifications is diluted to 3°io (w/v) with sterile demineralized water, the pH being corrected to 5.4 with sterile citric acid which salifies some basic groups present in albumin.
50 ml of said solution are mimed under vigorous agitation for at least 40 minutes with 1.25 ml of a sterile solution of paclitaxel in chloroform (75 mg/ml).

The mixture is processed in a homogenizer (suitably sterilized) at high pres-sure (9000-40000 psi) until a nanoemulsion (MPS < X1.2 microns) is obtained, this being rapidly frozen to -30°C and lyophilized for 57 hours under sterile conditions, while raising the temperature to +35°C.
The powder obtained, containing 5.00% (w/w) of paclitaxel and 4.3 (w/w) of water, is reconstituted with an aqueous 0.9% NaCI solution to a paclitaxel concen-tration of 2 mg/ml. The formulation obtained has an MPS of 0.19 microns, pH=5.4, and a stability > 24 hours.
Equivalent results are obtained by using acetic acid instead of citric acid.
l0 EXAMPLE 5 Preparation of a forrnazlation with Cl and pa~;lit~~el in powder dorm An injectable aqueous 25% (w/v) HSA solution in accordance with FDA
specifications (pH=6.9~0.5) is diluted to 3% (w/v) with sterile demineralized water, the pH being corrected to a value of 5.6 with 1M HCl which salifies some basic groups present in albumin.
57 ml of said solution, previously sterilized, are mixed under vigorous stir-ring for at least 30 minutes, with 1.40 ml of sterile chloroform and with 108 mg of sterile paclitaxel (titre > 99%) in powder form.
The mixture is processed in a horraogenizer (suitably sterilized) at high pres-sure (9000-40000 psi) until a nanoemulsion (MPS < 0.2 microns) is obtained, this being rapidly frozen to -80°C and lyophilized for 55 hours under sterile conditions, v~rhile raising the temperature to +30°C.
The powder obtained, containing 4.8 3 °ro (w/w) of paclitaxel and 4%
(w/w) of water, is reconstituted with an aqueous 0.9';% NaCl solution to a paclitaxel concen-tration of 2 mg/ml. The formulation obtained has an MPS of 0.175 microns, pH=5.6, and a stability > 24 hours.
Equivalent results are obtained by using phosphoric acid instead of hydro-chloric acid.
It is important to remark that the use of sterile paclitaxel in powder form en-ables to achieve the important advantage that only one reactor is required for forming the liquid mixture containing HSA and paclitaxel with consequent reduc-tion of costs and time necessary for completing the process.
F'K A l~~ThT ~ ~

Preparation of a formulation with citric acid and paclitaxel in powder form An injectable aqueous 25% (~l/v) HSA solution in accordance with FDA
specifications is diluted to 3% (w/v) with sterile demineralized water, the pH
being corrected to a value of 5.4 with citric acid which salifies some basic groups present in albumin.
50 ml of said solution, previously sterilized, are mixed under vigorous stir-ring for at least 40 minutes, with 1.23 ml of sterile chloroform and with 98 mg of sterile paclitaxel (titre > 99%) in powder form.
The mixture is processed in a homogenizer (suitably sterilized) at high pres-sure -(9000-40000 psi) until a nanoemulsion (MPS < 0,2 microns) is obtained, this being rapidly frozen to -30°C and lyophilized for 57 hours under sterile conditions, while raising the temperature to +35°C.
The powder obtained, containing 4.80 % (w/w) of paclitaxel and 3.8% (w/w) of water, is reconstituted with an aqueous 0.9% NaCI solution to a paclitaxel con-centration of 2 mg/ml. The formulation obtained has an MPS of 0.19 microns, pH=5.4, and a stability > 24 hours.
Equivalent results are obtained by using acetic acid instead of citric acid.

Preparation of a for$nulation with sterile citric acid and paclitaxel in powder foryn.
An injectable aqueous 25% (w/v) HSA solution in accordance with FDA
specifications is diluted to 3% (w/v) with sterile demineralized water, the pH
being corrected to a value of 5.5 with sterile citric acid which salifies some basic groups present in albumin.
37 ml of said solution are mixed under vigorous stirring for at least 40 min-utes, with 0.91 ml of sterile chloroform and 71 mg of sterile paclitaxel.(titre > 99%) in powder form, after which the mixture is cooled to 5-8°C.
The mixture is processed in a homogenizer (suitably sterilized) at high pres-sure (9000-40000 psi) until a nanoemulsion (MPS < 0.2 microns) is obtained, this being rapidly frozen to -80°C and lyophilized for 58 hours under sterile conditions, while raising the temperature to +30°C.
The powder obtained, containing 4.70 % (w/w) of paclitaxel and 4.5% (w/w) of water, is reconstituted with an aqueous 0.9% NaCI solution to a paclitaxel con-,. . _g_ centration of 2 mg/ml. The formulation obtained has an MPS of 0.185 microns, pH=5.5, and a stability > 24 hours.

Preparation of a formulation containing 9.35% of paclitaxel An injectable aqueous 25% HSA solution in accordance with FDA specifications is diluted to 3% (w/v) with sterile demineralized water, the pH being corrected to 5.6 with 1M HCl which salifics some basic groups present in albumin. 60 ml of said solution, suitably sterilized, are mixed with 2.15 ml. of a sterile solution of 110 mg/ml of paclitaxel in CHC13, after which the mixture is processed in a homoge-nizer (suitably sterilized) at high pressure (9000-40000 psi) until a nanoemulsion (MPS < 0.2 microns) is obtained, this being frozen to -50°C and lyophilized for 50 hours under sterile conditions, while raising the temperature to +30°C.
The powder obtained, containing 9.36% of paclitaxel and 3.9% (w/w) of wa-ter, is reconstituted with an aqueous 0.9% NaCl solution to a paclitaxel concentra-tion of 2.5 mg/ml. The formulation obtained has an MPS of 0.1'75 microns, pH=5.6, and a stability > 24 hours.
T~'XAAlfI~T G' Q
Preparation of foranulation at pI-~ 5.5 An injectable aqueous 20% (w/v) HSA solution in accordance with FDA
specifications (pH=6.9T0.5) is diluted to 3% (w/v) with sterile demineralized water, the pH being corrected to a value of 5.5 with citric acid which salifies some basic groups present in albumin.
110 ml of said solution are mixed with 4.10 ml of sterile CHCIs and with 639 mg of sterile paclitaxel (titre > 99%) in powder form, then the mixture is processed ?5 in a high pressure homogenizer (suitably sterilized) until a nanoemulsion (MPS
about 0.2 microns) is obtained, this being filtered through a sterile filter (0.2 mi-Irons), evaporated under vacuum to remove the solvents, frozen and lyophilized under sterile conditions for 48 hours.
The powder obtained, containing 10.8 % (w/w) of paclitaxel, is reconstituted with an aqueous 0.9% NaCI solution to a paclitaxel concentration of 2 mg/ml.
The formulation obtained has an MPS of 0.15 microns and a stability > 24 hours.

Claims

1 An antitumor formulation consisting of a lyophilized powder of nanoparticles of paclitaxel and human serum albumin, in which the paclitaxel is present in a quantitity between 1% and 20% and the albumin between 60% and 98%, the per-centages being by weight and the mean nanoparticle size being less than 0.2 mi-crons, characterized in that said lyophilized powder contains between 1% and 20%
by weight of biocompatible salts obtained by salification of at least one bicompati-ble acid or due to the presence of at least one biocompatible acid buffer substance, the acid or the buffer substance being present in a quantity such that the pH
of a reconstituted aqueous injectable mixture of the powder is between 5.4 and 5.8.

2 A formulation as claimed in claim 1, characterized in that said pH is between 5.5 and 5.7.

3 A formulation as claimed in claims 1 and 2 characterized in that said lyophi-lized powder contains up to 5% (w/w) of water.

4 A formulation according to claims 1 to 3, characterized in that, when re-constituted to form a physiological injectable mixture, it contains paclitaxel at a concentration between 0.1 and 3 mg/ml.

Injectable aqueous mixture of a formulation according to claims 1 to 4, char-acterized in that it contains paclitaxel at a concentration between 0.1 and 3 mg/ml.

6 Injectable aqueous mixture as claimed in claim 5, characterized in that pa-clitaxel is present at a concentration between 0.5 and 2.5 mg/ml.

7 Physiological injectable mixture obtainable from an antitumor formulation according to any of the preceding claims.