Note: Descriptions are shown in the official language in which they were submitted.
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FORMULATIONS FOR PARENTERAL USE OF ESTRAMUSTINE PHOSPHATE
WITH IMPROVED PHARMACOLOGICAL PROPERTIES
The present invention relates to pharmaceutical
formulations of estramustine phosphate for parenteral use
with improved pharmacological properties and, more
particularly, to formulations of estramustine phosphate for
parenteral use further comprising sulfoalkyl ether
cyclodextrins and human albumin.
Estramustine phosphate (The Merck Index, XII Ed., No. 3749,
1996) is an estradiol-17(3-phosphate derivative widely known
in the art as antitumor agent, currently used in the
treatment of advanced adenocarcinoma of the prostate.
The drug is usually administered orally, preferably at a
dose of 10-15 mg/kg/day. Intravenous administration,
however, is also adopted in some particular cases.
For example, initial intravenous administration of
estramustine phosphate, followed by oral administration,
has been reported at dosages paralleling the oral
administration for the drug, i.e. 300-600 mg daily given
intravenously and usually repetitively over for several
consecutive days (see, for a reference, British Journal of
Urology, 1977, 49, 73-79; J. Uro1.108:303-306, 1972; Eur.
Clin. Pharmacol. 26(1), 113-119, 1984; Eur. Urol. 1990, 17,
216-218).
Estramustine phosphate as well as other well-known
cytotoxic compounds used in antitumor therapy are known to
cause, or potentially cause, vascular damages at the site
of injection when parenterally, in particular
intravenously, administered.
As an example, studies in patients treated with
estramustine phosphate administered as a slow intravenous
injection or as a bolus, at 300 mg/day, revealed
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thrombophlebitis and local irritations at the peripheral
intravenous injection sites.
These drawbacks are considered major limitations for the
intravenous administration of estramustine phosphate, thus
requiring, in many patients, the establishment of central
line administration or, in some cases, even discontinuation
of the treatment.
With the aim of minimising the unwanted effects associated
with the intravenous administration of cytotoxic agents, a
few means are reported in the art.
Among them is the use of cyclodextrins, for instance
hydroxypropyl-cyclodextrin, in the preparation of
formulations for parenteral administration of cytotoxic
known to cause ulcerative lesions. See, for a reference, US
patent No. 5,804,568 in the name of Supergen Inc.
Cyclodextrin derivatives such as sulfoalkyl ether
cyclodextrins are known in the art as solubilizing agents
for insoluble or poorly soluble drugs (see, for a
reference, US 5,134,127 in the name of the University of
Kansas).
Also known in the art are formulations for the intravenous
administration of estramustine phosphate containing human
albumin, reported to be characterised by fewer local side-
effects upon injection of the active (see, for a reference,
H. Schutz et al.; Krankenhauspharmazie, II year, issue No.
3, 1988).
In this respect, we found formulations for parenteral use
comprising estramustine phosphate together with sulfoalkyl
ether cyclodextrins and human albumin which, unexpectedly,
resulted to achieve optimal protection from side-effects
associated with estramustine administration.
It is therefore the object of the present invention a
formulation for parenteral use comprising estramustine
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phosphate in admixture with a sulfoalkyl ether cyclodextrin
and human albumin.
Once administered intravenously to patients, the
formulations object of the present invention do not provoke
ulcerative damages, nor thrombophlebitis, at the site of
injection.
Very interestingly, the estramustine phosphate formulations
of the invention result to be endowed with unexpected
pharmacological properties, expressed in terms of toxicity
at the site of injection, markedly improved with respect to
formulations containing, as a single protective excipient,
a sulfoalkyl ether cyclodextrin or, alternatively, human
albumin.
In the present invention, unless otherwise specified, with
the term formulation comprising estramustine phosphate, as
the active ingredient, we intend any formulation comprising
estramustine phosphate either in the acid form or as a
pharmaceutically acceptable salt for parenteral
administration such as, for instance, a salt with a basic
amino acid or with N-methyl glucamine, otherwise referred
to as meglumine.
Preferably, estramustine phosphate is in the form of its
meglumine salt.
With the term sulfoalkyl ether cyclodextrin we refer to any
cyclodextrin of the above type wherein alkyl stands for
straight or branched C1-C6 alkyl group such as methyl,
ethyl, n.propyl, isopropyl, n.butyl, isobutyl, sec-butyl,
tert-butyl, n.pentyl, n.hexyl and the like.
Preferably, the formulation of the present invention
comprises estramustine phosphate in admixture with
sulfobutyl ether i~-cyclodextrin.
According to a preferred embodiment of the invention, the
weight ratio between estramustine phosphate and sulfoalkyl
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ether cyclodextrin is comprised from about 1:0.5 to about
1:5, respectively.
However, higher amounts of sulfoalkyl ether cyclodextrin
with respect to the active are sill effective and hence
comprised within the scope of the present invention.
According to another preferred embodiment of the invention,
the above formulations are advantageously used for
intravenous use.
As such, these formulations of the invention can be
administered to patients either as a slow injection, e.g.
over about 30 minutes to about 3 hours, or as a bolus
injection, also referred to as IV (intravenous) push.
In another preferred embodiment of the invention either
(i) the estramustine phosphate is in lyophilised form and
the parenterally acceptable carrier or diluent is a
physiological solution for parenteral use containing
the sulfoalkyl ether cyclodextrin and the human
albumin, or
(ii) the estramustine phosphate and sulfoalkyl ether
cyclodextrin are in lyophilised form and the
parenterally acceptable carrier or diluent is a
physiological solution for parenteral use containing
the human albumin.
The invention also provides a product which comprises
estramustine phosphate in lyophilised form and a
physiological solution for parenteral use containing human
albumin.
The formulations of the invention also provide a very
advantageous method for delivering estramustine phosphate
intravenously, even when high doses of the active are
needed.
It is therefore a further object of the invention a
formulation for parenteral use comprising estramustine
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phosphate, as a single infusion dosage of the active
exceeding 1300 mg, in admixture with a sulfoalkyl ether
cyclodextrin and human albumin.
According to another preferred embodiment of the invention,
5 it is further provided a formulation for parenteral use
comprising estramustine phosphate, as a single infusion
dosage of the active exceeding 950 mg/m', in admixture with
a sulfoalkyl ether cyclodextrin and human albumin.
The formulations object of the present invention allow the
administration of the active either as a single agent or,
alternatively, in combination with known anticancer
treatments such as radiation therapy or chemotherapy
regimen in combination with cytostatic or cytotoxic agents,
antibiotic-type agents, alkylating agents, antimetabolite
agents, hormonal agents, e.g. aromatase inhibitors,
immunological agents, interferon-type agents,
cyclooxygenase inhibitors (e. g. COX-2 inhibitors),
metallomatrixprotease inhibitors, telomerase inhibitors,
tyrosine kinase inhibitors, anti-growth factor receptor
agents, anti-HER agents, anti-EGFR agents, anti-
angiogenesis agents, farnesyl transferase inhibitors, ras-
raf signal transduction pathway inhibitors, cell cycle
inhibitors, other cdks inhibitors, tubulin binding agents,
topoisomerase I inhibitors, topoisomerase II inhibitors,
and the like.
As an example, the above formulations can be administered
in combination with one or more chemotherapeutic agents,
optionally within liposomal formulations thereof.
Examples of chemotherapeutic agents are, for instance,
taxane, taxane derivatives, CPT-11, camptothecin and
derivatives thereof, anthracycline glycosides, e.g.
doxorubicin, idarubicin or epirubicin, etoposide,
navelbine, vinblastine, carboplatin, cisplatin and the
like, optionally within liposomal formulations thereof.
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In addition, the above formulations can be also
administered in combination with protein kinase inhibitors
such as, for instance, the indolinone derivatives disclosed
by Sugen in the international patent applications WO
96/40116 and WO 99/61422, which are herewith incorporated
by reference.
In this respect, the formulations object of the invention
can be preferably administered in combination with 3-[4-(2-
carboxyethyl-3,5-dimethylpyrrol-2-yl)methylidenyl]-2-
indolinone and 3[(2,4-dimethylpyrrol-5-yl)methylidenyl]-2-
indolinone, better known as Sugen SU 6668 and SU 5416,
respectively.
The formulations of the invention may be administered
sequentially with known anticancer agents when a
combination formulation is inappropriate.
Therefore, it is a further object of the present invention
a product containing a formulation for parenteral use of
estramustine phosphate in admixture with a sulfoalkyl ether
cyclodextrin and human albumin and one or more
chemotherapeutic agents, as a combined preparation for
simultaneous, separate or sequential use in anticancer
therapy.
Toxicology
To study the local irritant effects of estramustine
phosphate after repeated intravenous administrations to
rats, in comparison to a formulation of estramustine
phosphate according to the present invention, the active
was dissolved in different vehicles such as water solution
for injection and water solution for injection further
containing sulfobutyl ether i~-cyclodextrin and human
albumin. In addition, formulations of estramustine
phosphate in admixture with sulfobutyl ether f~-cyclodextrin
only or, alternatively, with human albumin only, were used
for comparison.
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In particular, the following water for injection solutions
wherein either the active estramustine phosphate (therein
referred to as EMP) as well as the excipients sulfobutyl
ether f~-cyclodextrin and human albumin (therein referred to
as SBECD and HA, respectively) are expressed in terms of
weight ratios, were prepared and tested:
(a) negative control: water for injection;
(b) positive control: EMPp
(c) comparison: EMP:SBECD=1:1;
(d) comparison: EMP:HA=1:0.21;
(e) tested solution: EMP:SBECD:HA=1:1:0.21;
Male Sprague-Dawley rats were used because of their
acceptance as a predictor of toxic change in man. The rats
were 6 weeks old at the start of the study.
Estramustine phosphate, in the form of meglumine salt, was
administered to groups of rats as a repeated intravenous
injection during 3 days. Rats were then sacrificed: a half
of the rats at the fourth day and a half at the fifth day.
The dose level of estramustine phosphate, in all the
different tested solutions, was of 150 mg/kg/day.
Clinical observations were recorded daily. Thrombophlebitic
side effects resulted in a dark bluish/blackish coloration
of the tail during the treatment period.
A score system based on tail coloration and its extension
was used to evaluate the different tested formulations.
The score system considered estramustine phosphate water
solution (b) as the positive control (i.e. marked
toxicity). Water for injection (a) was administered to the
control group as negative control (i.e. no toxicity signs).
Histological evaluation was carried out on the tail of the
rats treated with the composition of the invention.
Estramustine phosphate in a water solution (b) induced, at
the used dose, local irritant effects at the injection site
after the first administration and marked toxicity signs at
the end of the experiment.
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Likewise, toxicity signs at the injection site were also
observed for the comparison (c) and (d) EMP solutions
containing SBECD or HA, as the sole excipients.
On the contrary, no toxicity was observed with the
formulation of the invention containing sulfobutyl ether f~-
cyclodextrin and human albumin (e).
Moreover, histological evaluation of the tail of the rats
treated with the formulation (e) did not reveal any damage
when compared to the tails of the control group.
In addition, the synergistic protective effect exerted by
combining both SBECD and HA excipients, as per the
invention, can clearly be evidenced by considering the
formulation of the invention (e) in comparison to the
formulations (c) and (d) wherein each single excipient is
present in the same amount with respect to the active.
It was thus concluded that estramustine phosphate in a
water solution containing sulfoalkyl ether cyclodextrin and
human albumin, according to the present invention, induced
markedly less local irritant effects when compared with a
water solution of estramustine phosphate itself.
Even more surprisingly, the formulation of the invention
produced less local irritant effects also in comparison to
analogous solutions of estramustine phosphate containing
sulfoalkyl ether cyclodextrin only or human albumin only.
One particularly preferred schedule for administering the
formulation of estramustine phosphate according to the
invention is a single infusion given once weekly to a
maximal dose of 4000 mg or 3500 mg/mz.
Another preferred schedule is the administration of a
single drug infusion once every two to four weeks.
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One schedule may be preferred over another in consideration
of schedules with other optional concomitant therapy. These
schedules may repeat in serial or as repetitive fashion.
The formulations of the present invention are useful in
antitumor therapy, particularly in the treatment of
prostate cancer, breast cancer, melanoma, lung cancer,
pancreatic cancer, colorectal cancer, ovarian cancer and
cancers of the brain.
The formulations object of the present invention are
prepared according to conventional techniques adopted in
the preparation of pharmaceutical forms for parenteral use.
Typically, a proper amount of estramustine phosphate,
either as a dry powder or into a lyophilised form, is
dissolved in a pharmaceutically acceptable solution for
parenteral use and then admixed with a proper amount of a
sulfoalkyl ether cyclodextrin, for instance sulfobutyl
ether i~-cyclodextrin.
The above solution is then admixed with a proper amount of
human albumin, either as a dry powder or as a commercially
available solution, e.g. human albumin 250, 200 or 50,
optionally properly diluted.
As an example, a proper amount of estramustine phosphate in
the form of a suitable salt such as, for instance, N-methyl
glucamine salt, is dissolved in a suitable amount of
sterile water or aqueous dextrose solution, e.g. 50
dextrose in water for intravenous administration, and then
admixed with a proper amount of powdered sulfobutyl ether
i~-cyclodextrin.
The above admixture is subsequently added with a proper
amount of human albumin, for instance as a dry powder, and
subsequently stirred, sterilised and lyophilised according
to conventional techniques.
From the foregoing it is clear to the man skilled in the
art that each of the ingredients of the invention such as
sulfoalkyl ether cyclodextrin and human albumin, each
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independently as a powder or into a suitable solution, can
be admixed in any order to the active, already dissolved
into a proper solution or in the form of a dry powder.
Likewise, the formulations of the invention can also be
5 prepared by admixing the active with the aforementioned
ingredients already properly combined as above indicated.
The final freeze-dried formulation is then prepared and
stored in vials for injection; the addition of a proper
amount of sterile water or a physiological solution for
10 parenteral use enables the preparation of the final
formulation to be injected.
The above method is also suitable for preparing high
dosages estramustine phosphate formulations whilst
maintaining the desired weight ratio between the
components.
The unit strength of the formulation to be injected
depended on the concentration of the active in the solution
itself and, of course, on the filling volume of the vials
used to prepare the final formulation.
Additionally, the formulations of the present invention may
optionally contain pharmaceutically acceptable excipients
for parenteral administration such as, for instance,
bulking agents, e.g. lactose or mannitol, pH buffering
agents, anti-oxidant agents, preservative agents, tonicity
adjusters and the like.
The following examples are herewith intended to better
illustrate the present invention without representing any
limitation to it.
Example 1
Preparation of estramustine phosphate N-methyl glucamine
salt in admixture with sulfobutyl ether 8-cyclodextrin
(estramustine phosphate:sulfobutyl ether 8-cyclodextrin=1:1
weight ratio)
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300 mg of estramustine phosphate were weighed in a beaker
and dispersed by means of magnetic stirring in 5 ml of
water. 120.8 mg of N-methyl-glucamine were then added under
stirring to the watery dispersion of the active and, after
a few minutes, a clear solution was obtained. 312.5 mg of
sulfobutyl ether f~-cyclodextrin were added, maintaining the
solution under stirring till the solubilization was
completed.
The solution obtained was then brought to the final volume
of 10 ml with water so as to reach a final concentration of
30 mg/ml of estramustine phosphate and 31.25 mg/ml of
sulfobutyl ether i~-cyclodextrin (1:1 weight ratio - 1:0.25
molar ratio respectively).
A solution prepared as previously described, properly
sterilized by filtration, was tested for its local vein
tolerability in rats.
Example 2
The formulation described in Example 1 was also prepared by
solubilization of the commercially available Estracyt~
freeze-dried formulation containing 300 mg/vial of the
active. The reconstitution of the formulation was made
using 10 ml of a 31.25 mg/ml sulfobutyl ether i3-
cyclodextrin solution so as to obtain a final concentration
of 30 mg/ml of estramustine phosphate and 31.25 mg/ml of
cyclodextrin (1:1 weight ratio - 1:0.25 molar ratio
respectively).
Example 3
Preparation of estramustine phosphate N-methyl glucamine
salt in admixture with human albumin (estramustine
phosphate: albumin=1:0.21 weight ratio)
300 mg of estramustine phosphate were weighed in a beaker
and dispersed by means of magnetic stirring in 5 ml of
water. 120.8 mg of N-methyl-glucamine were then added under
stirring to the watery dispersion of the active and, after
a few minutes, a clear solution was obtained. 0.250 ml of a
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commercially available solution of human albumin at 250
concentration were added whilst maintaining the solution
under stirring.
The obtained solution was then brought to the final volume
of 10 ml with water so as to reach a final concentration of
30 mg/ml of estramustine phosphate and 6.25 mg/ml of human
albumin (1:0.21 weight ratio respectively).
A solution prepared as previously described, properly
sterilized by filtration, was tested for its local vein
tolerability in rats.
Example 4
The formulation described in Example 3 was also prepared by
solubilization of the commercially available Estracyt~
freeze-dried formulation containing 300 mg/vial of the
active. The reconstitution of the formulation was made by
using 10 ml of a 6.25 mg/ml human albumin solution so as to
obtain a final concentration of 30 mg/ml of estramustine
phosphate and 6.25 mg/ml of human albumin (1:0.21 weight
ratio respectively).
The albumin solution could be prepared either by dissolving
in water a proper amount of human albumin as a dry powder
or by properly diluting a commercially available human
albumin solution.
Example 5
Preparation of estramustine phosphate N-methyl glucamine
salt in admixture with sulfobutyl ether $-cyclodextrin and
human albumin (estramustine phosphate:sulfobutyl ether 8-
cyclodextrin:albumin=1:1:0.21 weight ratio, respectively).
300 mg of estramustine phosphate were weighed in a beaker
and dispersed by means of magnetic stirring in 5 ml of
water. 120.8 mg of N-methyl-glucamine were then added under
stirring to the watery dispersion of the active and, after
a few minutes, a clear solution was obtained. 312.5 mg of
sulfobutyl ether f~-cyclodextrin were added, maintaining the
solution under stirring until complete dissolution.
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0.250 ml of a commercially available solution of human
albumin at 25o concentration were then added, maintaining
the solution under stirring.
The solution was then brought to the final volume of 10 ml
with water so as to reach a final concentration of 30 mg/ml
of estramustine phosphate, 31.25 mg/ml of sulfobutyl ether
f~-cyclodextrin and 6.25 mg/ml of human albumin. The weight
ratio between the components of the solution were as
follows: estramustine phosphate:sulfobutyl ether f~
cyclodextrin:human albumin 1:1:0.21 respectively.
A solution prepared as previously described, properly
sterilized by filtration, was tested for its local vein
tolerability in rats.
Example 6
The formulation described in Example 4 was also prepared by
solubilization of the commercially available Estracyt~
freeze-dried formulation containing 300 mg/vial of the
active. The reconstitution of the formulation was made by
using 10 ml of a solution containing 31.25 mg/ml of
sulfobutyl ether f~-cyclodextrin and 6.25 mg/ml of human
albumin so as to reach a final concentration of 30 mg/ml of
the active. The weight ratio between the components of the
solution were as follows: estramustine phosphate:sulfobutyl
ether i3-cyclodextrin:human albumin 1:1:0.21 respectively.
