U.S. patent application number 10/833619 was filed with the patent office on 2004-10-14 for emulsion vehicle for poorly soluble drugs.
This patent application is currently assigned to Sonus Pharmaceuticals, Inc.. Invention is credited to Constantinides, Panayiotis P., Lambert, Karel J., Quay, Steven C..
Application Number | 20040202712 10/833619 |
Document ID | / |
Family ID | 27357338 |
Filed Date | 2004-10-14 |
United States Patent
Application |
20040202712 |
Kind Code |
A1 |
Lambert, Karel J. ; et
al. |
October 14, 2004 |
Emulsion vehicle for poorly soluble drugs
Abstract
An emulsion of .alpha.-tocopherol, stabilized by biocompatible
surfactants, as a vehicle or carrier for therapeutic drugs, which
is substantially ethanol free and which can be administered to
animals or humans various routes is disclosed. Also included in the
emulsion is PEGylated vitamin E PEGylated .alpha.-tocopherol
includes polyethylene glycol subunits attached by a succinic acid
diester at the ring hydroxyl of vitamin E and serves as a primary
surfactant, stabilizer and a secondary solvent in emulsions of
.alpha.-tocopherol.
Inventors: |
Lambert, Karel J.; (Seattle,
WA) ; Constantinides, Panayiotis P.; (Gurnee, IL)
; Quay, Steven C.; (Edmonds, WA) |
Correspondence
Address: |
CHRISTENSEN, O'CONNOR, JOHNSON, KINDNESS, PLLC
1420 FIFTH AVENUE
SUITE 2800
SEATTLE
WA
98101-2347
US
|
Assignee: |
Sonus Pharmaceuticals, Inc.
|
Family ID: |
27357338 |
Appl. No.: |
10/833619 |
Filed: |
April 28, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10833619 |
Apr 28, 2004 |
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10151079 |
May 17, 2002 |
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10151079 |
May 17, 2002 |
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09003173 |
Jan 5, 1998 |
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6458373 |
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60034188 |
Jan 7, 1997 |
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60048840 |
Jun 6, 1997 |
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Current U.S.
Class: |
424/450 ;
514/458 |
Current CPC
Class: |
Y10S 514/938 20130101;
Y10S 514/975 20130101; Y10S 977/775 20130101; A61K 9/0019 20130101;
A61K 9/4858 20130101; A61K 47/22 20130101; Y10S 977/907 20130101;
Y10S 977/801 20130101; Y10S 977/915 20130101; A61K 9/1075 20130101;
A61P 35/00 20180101 |
Class at
Publication: |
424/450 ;
514/458 |
International
Class: |
A61K 031/355; A61K
009/127 |
Claims
1-24. (Canceled)
25. A method of administering a chemotherapeutic agent to a subject
in need there of, comprising: providing a pharmaceutical
composition comprising a chemotherapeutic agent and a tocopherol,
wherein the chemotherapeutic agent is at least one of a taxoid, a
taxane, or a taxine, and wherein the concentration of the
chemotherapeutic agent is at least about 5 mg/ml; and administering
the pharmaceutical composition in a therapeutically effective
amount to a subject in need thereof.
26. The method of claim 25, wherein the chemotherapeutic agent is
paclitaxel.
27. The method of claim 26, wherein the concentration of the
paclitaxel in the composition is at least about 10 mg/ml.
28. The method of claim 26, wherein the concentration of the
paclitaxel in the composition is at least about 20 mg/ml.
29. The method of claim 28, wherein the tocopherol is
.alpha.-tocopherol.
30. The method of claim 25, wherein the composition further
comprises a tocopherol polyethylene glycol derivative.
31. The method of claim 30, wherein the tocopherol polyethylene
glycol derivative is d-.alpha.-tocopherol polyethylene glycol 1000
succinate.
32. The method of claim 25, wherein the composition further
comprises polyethylene glycol.
33. The method of claim 25, wherein the composition further
comprises a polyoxypropylene-polyoxyethylene glycol nonionic block
co-polymer.
34. The method of claim 25, wherein the composition is stable for
at least 3 months.
35. The method of claim 25, wherein the composition is administered
parentally.
36. The method of claim 25, wherein the composition is administered
by intravenous infusion over a period of less than 3 hours.
37. The method of claim 25, wherein the composition is administered
by bolus injection.
38. A method of administering a chemotherapeutic agent to a subject
in need there of, comprising: providing a pharmaceutical
composition comprising a chemotherapeutic agent, a tocopherol, and
a tocopherol polyethylene glycol derivative, wherein the
chemotherapeutic agent is at least one of a taxoid, a taxane, or a
taxine; and administering the pharmaceutical composition in a
therapeutically effective amount to a subject in need thereof.
39. The method of claim 38, wherein the chemotherapeutic agent is
paclitaxel.
40. The method of claim 39, wherein the concentration of the
paclitaxel in the composition is at least about 5 mg/ml.
41. The method of claim 39, wherein the concentration of the
paclitaxel in the composition is at least about 10 mg/ml.
42. The method of claim 39, wherein the concentration of the
paclitaxel in the composition is at least about 20 mg/ml.
43. The method of claim 38, wherein the tocopherol is
.alpha.-tocopherol.
44. The method of claim 38, wherein the tocopherol polyethylene
glycol derivative is tocopherol polyethylene glycol succinate.
45. The method of claim 38, wherein the composition further
comprises polyethylene glycol.
46. The method of claim 38, wherein the composition further
comprises a polyoxypropylene-polyoxyethylene glycol nonionic block
co-polymer.
47. The method of claim 38, wherein the composition is administered
parentally.
48. The method of claim 38, wherein the composition is administered
by intravenous infusion over a period of less than 3 hours.
49. The method of claim 38, wherein the composition is administered
by bolus injection.
50. A method of treating a carcinoma in a subject suffering
therefrom, comprising: providing a pharmaceutical composition
comprising a chemotherapeutic agent and a tocopherol, wherein the
chemotherapeutic agent is at least one of a taxoid, a taxane, or a
taxine, and wherein the concentration of the chemotherapeutic agent
is at least about 5 mg/ml; and administering the pharmaceutical
composition in a therapeutically effective amount to a subject
suffering from a carcinoma.
51. The method of claim 60, wherein the chemotherapeutic agent is
paclitaxel.
52. The method of claim 61, wherein the concentration of the
paclitaxel in the composition is at least about 10 mg/ml.
53. The method of claim 61, wherein the concentration of the
paclitaxel in the composition is at least about 20 mg/ml.
54. The method of claim 60, wherein the tocopherol is
.alpha.-tocopherol.
55. The method of claim 60, wherein the composition further
comprises a tocopherol polyethylene glycol derivative.
56. The method of claim 65, wherein the tocopherol polyethylene
glycol derivative is d-.alpha.-tocopherol polyethylene glycol 1000
succinate.
57. The method of claim 60, wherein the composition further
comprises polyethylene glycol.
58. The method of claim 60, wherein the composition further
comprises a polyoxypropylene-polyoxyethylene glycol nonionic block
co-polymer.
59. The method of claim 60, wherein the composition is stable for
at least 3 months.
60. The method of claim 60, wherein the composition is administered
parentally.
61. The method of claim 60, wherein the composition is administered
by intravenous infusion over a period of less than 3 hours.
62. The method of claim 60, wherein the composition is administered
by bolus injection.
63. The method of claim 60, wherein the carcinoma is a breast
carcinoma.
64. The method of claim 60, wherein the carcinoma is a lung
carcinoma.
65. The method of claim 60, wherein the carcinoma is a skin
carcinoma.
66. The method of claim 60, wherein the carcinoma is a uterus
carcinoma.
67. A method for treating a carcinoma in a subject suffering
therefrom, comprising: providing a pharmaceutical composition
comprising a chemotherapeutic agent, a tocopherol, and a tocopherol
polyethylene glycol derivative, wherein the chemotherapeutic agent
is at least one of a taxoid, a taxane, or a taxine; and
administering the pharmaceutical composition in a therapeutically
effective amount to a subject suffering from a carcinoma.
68. The method of claim 77, wherein the chemotherapeutic agent is
paclitaxel.
69. The method of claim 78, wherein the concentration of the
paclitaxel in the composition is at least about 5 mg/ml.
70. The method of claim 78, wherein the concentration of the
paclitaxel in the composition is at least about 10 mg/ml.
71. The method of claim 78, wherein the concentration of the
paclitaxel in the composition is at least about 20 mg/ml.
72. The method of claim 77, wherein the tocopherol is
.alpha.-tocopherol.
73. The method of claim 77, wherein the tocopherol polyethylene
glycol derivative is tocopherol polyethylene glycol succinate.
74. The method of claim 77, wherein the composition further
comprises polyethylene glycol.
75. The method of claim 77, wherein the composition further
comprises a polyoxypropylene-polyoxyethylene glycol nonionic block
co-polymer.
76. The method of claim 77, wherein the composition is administered
parentally.
77. The method of claim 77, wherein the composition is administered
by intravenous infusion over a period of less than 3 hours.
78. The method of claim 77, wherein the composition is administered
by bolus injection.
79. The method of claim 77, wherein the carcinoma is a breast
carcinoma.
80. The method of claim 77, wherein the carcinoma is a lung
carcinoma.
81. The method of claim 77, wherein the carcinoma is a skin
carcinoma.
82. The method of claim 77, wherein the carcinoma is a uterus
carcinoma.
Description
RELATED APPLICATIONS
[0001] This application is a non-provisional application based on
U.S. Provisional Application No. 60/034,188 filed Jan. 7, 1997 and
U.S. Provisional Application No. 60/048,840 filed Jun. 6, 1997.
BACKGROUND OF THE INVENTION
[0002] Hundreds of medically useful compounds are discovered each
year, but clinical use of these drugs is possible only if a drug
delivery vehicle is developed to transport them to their
therapeutic target in the human body. This problem is particularly
critical for drugs requiring intravenous injection in order to
reach their therapeutic target or dosage but which are water
insoluble or poorly water soluble. For such hydrophobic compounds,
direct injection may be impossible or highly dangerous, and can
result in hemolysis, phlebitis, hypersensitivity, organ failure
and/or death. Such compounds are termed by pharmacists
"lipophilic", "hydrophobic", or in their most difficult form,
"amphiphobic".
[0003] A few examples of therapeutic substances in these categories
are ibuprofen, diazepam, griseofulvin, cyclosporin, cortisone,
proleukin, etoposide and paclitaxel. Kagkadis, K A et al. (1996)
PDA J Pharm Sci Tech 50(5):317-323; Dardel, O. 1976. Anaesth Scand
20:221-24. Sweetana, S and M J U Akers. (1996) PDA J Pharm Sci Tech
50(5):330-342.
[0004] Administration of chemotherapeutic or anti-cancer agents is
particularly problematic. Low solubility anti-cancer agents are
difficult to solubilize and supply at therapeutically useful
levels. On the other hand, water-soluble anti-cancer agents are
generally taken up by both cancer and non-cancer cells thereby
exhibiting non-specificity.
[0005] Efforts to improve water-solubility and comfort of
administration of such agents have not solved, and may have
worsened, the two fundamental problems of cancer chemotherapy: 1)
non-specific toxicity and 2) rapid clearance form the bloodstream
by non-specific mechanisms. In the case of cytotoxins, which form
the majority of currently available chemotherapies, these two
problems are clearly related. Whenever the therapeutic is taken up
by noncancerous cells, a diminished amount of the drug remains
available to treat the cancer, and more importantly, the normal
cell ingesting the drug is killed.
[0006] To be effective in treating cancer, the chemotherapeutic
must be present throughout the affected tissue(s) at high
concentration for a sustained period of time so that it may be
taken up by the cancer cells, but not at so high a concentration
that normal cells are injured beyond repair. Obviously, water
soluble molecules can be administered in this way, but only by
slow, continuous infusion and monitoring, aspects which entail
great difficulty, expense and inconvenience.
[0007] A more effective method of administering a cancer
therapeutic, particularly a cytotoxin, is in the form of a
dispersion of oil in which the drug is dissolved. These oily
particles are made electrically neutral and coated in such a way
that they do not interact with plasma proteins and are not trapped
by the reticuloendothelial system (RES), instead remaining intact
in the tissue or blood for hours, days or even weeks. In most
cases, it is desirable if the particles also distribute themselves
into the surrounding lymph nodes which are injected at the site of
a cancer. Nakamoto, Y et al. (1975) Chem Pharm Bull
23(10):2232-2238. Takahashi, T et al. (1977) Tohoku J Exp Med
123:235-246. In many cases direct injection into blood is the route
of choice for administration. Even more preferable, following
intravenous injection, the blood-borne particles may be
preferentially captured and ingested by the cancer cells
themselves. An added advantage of a particulate emulsion for the
delivery of a chemotherapeutic is the widespread property of
surfactants used in emulsions to overcome multidrug resistance.
[0008] For drugs that cannot be formulated as an aqueous solution,
emulsions have typically been most cost-effective and gentle to
administer, although there have been serious problems with making
them sterile and endotoxin free so that they may be administered by
intravenous injection. The oils typically used for pharmaceutical
emulsions include saponifiable oils from the family of
triglycerides, for example, soybean oil, sesame seed oil,
cottonseed oil, safflower oil and the like. Hansrani, P K et al.,
(1983) J Parenter Sci Technol 37:145-150. One or more surfactants
are used to stabilize the emulsion, and excipients are added to
render the emulsion more biocompatible, stable and less toxic.
Lecithin from egg yolks or soybeans is a commonly used surfactant.
Sterile manufacturing can be accomplished by absolute sterilization
of all the components before manufacture, followed by absolutely
aseptic technique in all stages of manufacture. However, improved
ease of manufacture and assurance of sterility is obtained by
terminal sterilization following sanitary manufacture, either by
heat or by filtration. Unfortunately, not all emulsions are
suitable for heat or filtration treatments.
[0009] Stability has been shown to be influenced by the size and
homogeneity of the emulsion. The preferred emulsion consists of a
suspension of sub-micron particles, with a mean size of no greater
than 200 nanometers. A stable dispersion in this size range is not
easily achieved, but has the benefit that it is expected to
circulate longer in the bloodstream. Further, less of the stable
dispersion is phagocytized non-specifically by the
reticuloendothelial system. As a result the drug is more likely to
reach its therapeutic target. Thus, a preferred drug emulsion will
be designed to be actively taken up by the target cell or organ,
and is targeted away from the RES.
[0010] The use of vitamin E in emulsions is known. In addition to
the hundreds of examples where vitamin E in small quantities [for
example, less than 1%, RT Lyons. Pharm Res 13(9): S-226, (1996)
"Formulation development of an injectable oil-in-water emulsion
containing the lipophilic antioxidants K-tocopherol and
P-carotene"] is used as an anti-oxidant in emulsions, the first
primitive, injectable vitamin E emulsions per se were made by
Hidiroglou for dietary supplementation in sheep and for research on
the pharmacokinetics of vitamin E and its derivatives. Hidiroglou M
and Karpinski K. (1988) Brit J Nutrit 59:509-518.
[0011] For mice, an injectable form of vitamin E was prepared by
Kato and coworkers. Kato Y., et al. (1993) Chem Pharm Bull
41(3):599-604. Micellar solutions were formulated with Tween 80,
Brij 58 and HCO-60. Isopropanol was used as a co-solvent, and was
then removed by vacuum evaporation; the residual oil glass was then
taken up in water with voitexing as a micellar suspension. An
emulsion was also prepared by dissolving vitamin E with soy
phosphatidycholine (lecithin) and soybean oil. Water was added and
the emulsion prepared with sonication.
[0012] In 1983, E-Ferol, a vitamin E emulsion was introduced for
vitamin E supplementation and therapy in neonates. Alade S L et al.
(1986) Pediatrics 77(4):593-597. Within a few months over 30 babies
had died as a result of receiving the product, and the product was
promptly withdrawn by FDA order. The surfactant mixture used in
E-Ferol to emulsify 25 mg/mL vitamin E consisted of 9% Tween 80 and
1% Tween 20. These surfactants seem ultimately to have been
responsible for the unfortunate deaths. This experience illustrates
the need for improved formulations and the importance of selecting
suitable biocompatible surfactants and carefully monitoring their
levels in parenteral emulsions and.
[0013] An alternative means of solubilizing low solubility
compounds is direct solubilization in a non-aqueous milieu, for
example alcohol (such as ethanol) dimethylsulfoxide or triacetin.
An example in PCT application WO 95/11039 describes the use of
vitamin E and the vitamin E derivative TPGS in combination with
ethanol and the immuno-suppressant molecule cyclosporin.
Alcohol-containing solutions can be administered with care, but are
typically given by intravenous drip to avoid the pain, vascular
irritation and toxicity associated with bolus injection of these
solutions.
[0014] Problems with pharmaceutical formulations in non-aqueous
solvents and solubilizers such as alcohol (ethanol, isopropanol,
benzyl alcohol, etc.) relate to the ability of these solvents to
extract toxic substances, for example plasticizers, from their
containers. The current commercial formulation for the anti-cancer
drug paclitaxel, for example, consists of a mixture of hydroxylated
castor oil and ethanol, and rapidly extracts plasticizers such as
di-(2-ethylhexyl)-phthalate from commonly used intravenous infusion
tubing and bags. Adverse reactions to the plasticizers have been
reported, such as respiratory distress, necessitating the use of
special infusion systems at extra expense and time. Waugh, et al.
(1991) Am J Hosp Pharmacists 48:-1520.
[0015] In light of these problems, it can be seen that the ideal
emulsion vehicle would be inexpensive, non-irritating or even
nutritive and palliative in itself, terminally sterilizable by
either heat or filtration, stable for at least 1 year under
controlled storage conditions, accommodate a wide variety of water
insoluble and poorly soluble drugs and be substantially
ethanol-free. In addition to those drugs which are lipophilic and
dissolve in oils, also needed is a vehicle which will stabilize,
and carry in the form of an emulsion, drugs which are poorly
soluble in lipids and in water.
SUMMARY OF THE INVENTION
[0016] In order to meet these needs, the present invention is
directed to pharmaceutical compositions including:
.alpha.-tocopherol, a surfactant or mixtures of surfactants, with
and without an aqueous phase, and a therapeutic agent wherein the
composition is in the form of an emulsion, micellar solution or a
self-emulsifying drug delivery system. In a preferred form, the
solution is substantially ethanol-free.
[0017] The pharmaceutical compositions can be stabilized by the
addition of various amphiphilic molecules, including anionic,
nonionic, cationic, and zwitterionic surfactants. Preferably, these
molecules are PEGylated surfactants and optimally PEGylated
.alpha.-tocopherol.
[0018] The amphiphilic molecules further include surfactants such
as ascorbyl-6 palmitate; stearylamine; sucrose fatty acid esters,
various vitamin E derivatives and fluorine-containing surfactants,
such as the Zonyl brand series and a
polyoxypropylene-polyoxyethylene glycol nonionic block
copolymer.
[0019] The therapeutic agent of the emulsion may be a
chemotherapeutic agent preferably a taxoid analog and most
preferably, paclitaxel.
[0020] The emulsions of the invention can comprise an aqueous
medium when in the form of an emulsion or micellar solution. This
medium can contain various additives to assist in stabilizing the
emulsion or in rendering the formulation biocompatible.
[0021] The pharmaceutical compositions of the invention are
typically formed by dissolving a therapeutic agent in ethanol to
form a therapeutic agent solution. .alpha.-tocopherol is then added
to the therapeutic agent solution to form an .alpha.-tocopherol and
therapeutic agent solution. Next, the ethanol is removed to form a
substantially ethanol-free .alpha.-tocopherol and therapeutic agent
solution. The substantially ethanol free .alpha.-tocopherol and
therapeutic agent solution is blended with and without an aqueous
phase incorporating a surfactant to form a pre-emulsion. For IV
delivery the pre-emulsion is then homogenized to form a fine
emulsion. For oral delivery, the pre-emulsion is typically
encapsulated in a gelatin capsule.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The invention will be better understood by reference to the
figures, in which:
[0023] FIG. 1A shows the particle size of a paclitaxel emulsion
(QWA) at 7.degree. C. over time;
[0024] FIG. 1B shows the particle size of a-paclitaxel emulsion
(QWA) at 25.degree. C. over time;
[0025] FIG. 2 is an HPLC chromatogram showing the integrity of a
paclitaxel in an emulsion as described in Example 5;
[0026] FIG. 3A shows the paclitaxel concentration of a paclitaxel
emulsion (QWA) at 4.degree. C. over time;
[0027] FIG. 3B shows the paclitaxel concentration of a paclitaxel
emulsion (QWA) at 25.degree. C. over time; and
[0028] FIG. 4 shows the percentage of paclitaxel released over time
from three different emulsions. The symbol .cndot. represents the
percentage of paclitaxel released over time from an emulsion
commercially available from Bristol. Myers Squibb. The symbol
.tangle-solidup. represents the percentage of paclitaxel released
over time from an emulsion of this invention containing 6 mg/ml
paclitaxel (QWA) as described in Example 6. The symbol .diamond.
represents the percentage of paclitaxel released over time from an
emulsion of this invention (QWB) containing 7 mg/ml paclitaxel as
described in Example 7.
DETAILED DESCRIPTION OF THE INVENTION
[0029] To ensure a complete understanding of the invention the
following definitions are provided:
[0030] .alpha.-tocopherol: .alpha.-tocopherol, also known as
vitamin E, is an organic molecule with the following chemical
structure (Scheme I): 1
[0031] In addition to its use as a primary solvent,
.alpha.-tocopherol and its derivatives are useful as a therapeutic
agents.
[0032] Surfactants: Surface active group of amphiphilic- molecules
which are manufactured by chemical processes or purified from
natural sources or processes. These can be anionic, cationic,
nonionic, and zwitterionic. Typical surfactants are described in
Emulsions: Theory and Practice, Paul Becher, Robert E. Krieger
Publishing, Malabar, Fla., 1965; Pharmaceutical Dosage Forms:
Dispersed Systems Vol. I, Martin M. Rigear, Surfactants and U.S.
Pat. No. 5,595,723 which is assigned to the assignee of this
invention, Sonus Pharmaceuticals. All of these references are
hereby incorporated by reference.
[0033] TPGS: TPGS or PEGylated vitamin E is a vitamin E derivative
in which polyethylene glycol subunits are attached by a succinic
acid diester at the ring hydroxyl of the vitamin E molecule. TPGS
stands for D-.alpha.-tocopherol polyethyleneglycol 1000 succinate
(MW=530). TPGS is a non-ionic surfactant (HLB=16-18) with the
structure of Scheme II: 2
[0034] Various chemical derivatives of vitamin E TPGS including
ester and ether linkages of various chemical moieties are included
within the definition of vitamin E TPGS.
[0035] Polyethylene glycol: Polyethylene glycol (PEG) is a
hydrophilic, polymerized form of ethylene glycol, consisting of
repeating units of the chemical
structure--(CH.sub.2--CH.sub.2--O--)
[0036] AUC: AUC is the area under the plasma concentration-time,
commonly used in pharmacokinetics to quantitate the percentage of
drug absorption and elimination. A high AUC generally indicates
that the drug will successfully reach the target tissue or
organ.
[0037] Poloxamers or Pluronics: are synthetic block copolymers of
ethylene oxide and propylene oxide having the general
structure:
OH (OCH.sub.2CH.sub.2)a (OCH.sub.2CH.sub.2CH.sub.2)b
(OCH.sub.2CH.sub.2)a H
[0038] The following variants based on the values of a and b are
commercially available from BASF Performance Chemicals (Parsippany,
N. J.) under the trade name Pluronic and which consist of the group
of surfactants designated by the CTFA name of Poloxamer 108, 188,
217, 237, 238, 288, 338, 407, 101, 105, 122, 123, 124, 181, 182,
183, 184, 212, 231, 282, 331, 401, 402, 185, 215, 234, 235, 284,
333, 334, 335, and 403. For the most commonly used poloxamers 124,
188, 237, 338 and 407 the values of a and b are 12/20, 79/28,
64/37, 141/44 and 101/56, respectively.
[0039] Solutol HS-15: is a polyethylene glycol 660 hydroxystearate
manufactured by BASF (Parsippany, N.J.). Apart from free
polyethylene glycol and its monoesters, di-esters are also
detectable. According to the manufacturer, a typical lot of Solutol
HS-15 contains approximately 30% free polyethylene glycol and 70%
polyethylene glycol esters.
[0040] Other surfactants: Other surfactants useful in the invention
include ascorbyl-6 palmitate (Roche Vitamins, Nutley N.J.),
stearylamine, and sucrose fatty acid esters (Mitsubishi Chemicals).
Custom surfactants include those compounds with polar water-loving
heads and hydrophobic tails, such as a vitamin E derivative
comprising a peptide bonded polyglutamate attached to the ring
hydrokyl and pegylated phytosterol.
[0041] Hydrophile-lipophile balance: An empirical formula used to
index surfactants. Its value varies from 1-45 and in the case of
non-ionic surfactants from about 1-20. In general for lipophilic
surfactants the HLB is less than 10 and for hydrophilic ones the
HLB is greater than 10.
[0042] Biocompatible: Capable of performing functions within, or
upon a living organism in an acceptable manner, without undue
toxicity or physiological or pharmacological effects.
[0043] Substantially ethanol-free: A composition having an ethanol
concentration less than about 1.0% (w/v) ethanol.
[0044] Emulsion: A colloidal dispersion of two immiscible liquids
in the form of droplets, whose diameter, in general, are between
0.1 and 3.0 microns and which is typically optically opaque, unless
the dispersed and continuous phases are refractive index matched.
Such systems possess a finite stability, generally defined by the
application or relevant reference system, which may be enhanced by
the addition of amphiphilic molecules or viscosity enhancers.
[0045] Microemulsion: A thermodynamically stable isotropically
clear dispersion of two immuniscible liquids, such as oil and
water, stabilized by an interfacial film of surfactant molecules.
The microemulsion has a mean droplet diameter of less than 200 nm,
in general between 10-50 nm. In the absence of water, mixtures of
oil(s) and non-ionic surfactant(s) form clear and isotropic
solutions that are known as self-emulsifying drug delivery systems
(SEDDS) and have successfully been used to improve lipophilic drug
dissolution and oral absorption
[0046] Aqueous Medium: A water-containing liquid which can contain
pharmaceutically acceptable additives such as acidifying,
alkalizing, buffering, chelating, complexing and solubilizing
agents, antioxidants and antimicrobial preservatives, humectants,
suspending and/or viscosity modfying agents, tonicity and wetting
or other biocompatible materials.
[0047] Therapeutic Agent: Any compound natural of synthetic which
has a biological activity, is soluble in the oil phase and has an
octanol-buffer partition coefficient (Log P) of at least 2 to
ensure that the therapeutic agent is preferentially dissolved in
the oil phase rather than the aqueous phase. This includes
peptides, non-peptides and nucleotides. Lipid conjugates/prodrugs
of water soluble molecules are within the scope of therapeutic
agent.
[0048] Chemotherapeutic: Any natural or synthetic molecule which is
effective against one or more forms of cancer, and particularly
those molecules which are slightly or completely lipophilic or
which can be modified to be lipophilic. This definition includes
molecules which by their mechanism of action are cytotoxic
(anti-cancer agents), those which stimulate the immune system
(immune stimulators) and modulators of angiogenesis. The outcome in
either case is the slowing of the growth of cancer cells.
[0049] Chemotherapeutics include Taxol (paclitaxel) and related
molecules collectively termed taxoids, taxines or taxanes. The
structure of paclitaxel is shown in the figure below (Scheme III).
3
[0050] Included within the definition of "taxoids" are various
modifications and attachments to the basic ring structure (taxoid
nucleus) as may be shown to be efficacious for reducing cancer cell
growth and to partition into the oil (lipid phase) and which can be
constructed by organic chemical techniques known to those skilled
in the art. The structure of the taxoid nucleus is shown in Scheme
IV. 4
[0051] Chemotherapeutics include podophyllotoxins and their
derivatives and analogues. The core ring structure of these
molecules is shown in the following figure (Scheme V): 5
[0052] Another important class of chemotherapeutics useful in this
invention are camptothecins, the basic ring structure of which is
shown in the following figure, but includes any derivatives and
modifications to this basic structure which retain efficacy and
preserve the lipophilic character of the moleculeshown below
(Scheme VI). 6
[0053] Another preferred class of chemotherapeutics useful in this
invention are the lipophilic anthracyclines, the basic ring
structure of which is shown in the following figure (Scheme VII):
7
[0054] Suitable lipophilic modifications of Scheme VII include
substitutions at the ring hydroxyl group or sugar amino group.
[0055] Another important class of chemotherapeutics are compounds
which are lipophilic or can be made lipophilic by molecular
chemosynthetic modifications well known to those skilled in the
art, for example by combinatorial chemistry and by molecular
modelling, and are drawn from the following list: Taxotere,
Amonafide, Illudin S, 6-hydroxymethylacylfulvene Bryostatin 1,
26-succinylbryostatin 1, Palmitoyl Rhizoxin, DUP 941, Mitomycin B,
Mitomycin C, Penclomedine. Interferon .alpha.2b, angiogenesis
inhibitor compounds, Cisplatin hydrophobic complexes such as
2-hydrazino-4,5-dihydro-1H-imidazole with platinum chloride and
5-hydrazino-3,4-dihydro-2H-pyrrole with platinum chloride, vitamin
A, vitamin E and its derivatives, particularly tocopherol
succinate.
[0056] Other compounds useful in the invention include:
1,3-bis(2-chloroethyl)-1-nitrosurea ("carmustine" or "BCNU"),
5-fluorouracil, doxorubicin ("adriamycin"), epirubicin,
aclarubicin, Bisantrene
(bis(2-imidazolen-2-ylhydrazone)-9,10-anthracenedicarboxaldehy- de,
mitoxantrone, methotrexate, edatrexate, muramyl tripeptide, muramyl
dipeptide, lipopolysaccharides, 9-b-d-arabinofuranosyladenine
("vidarabine") and its 2-fluoro derivative, resveratrol, retinoic
acid and retinol, Carotenoids, and tamoxifen.
[0057] Other compounds useful in the application of this invention
include: Palmitoyl Rhizoxin, DUP 941, Mitomycin B, Mitomycin C,
Penclomedine, Interferon .alpha.2b, Decarbazine, Lonidamine,
Piroxantrone, Anthrapyrazoles, Etoposide, Camptothecin,
9-aminocamptothecin, 9-nitrocamptothecin, camptothecin-11
("Irinotecan"), Topotecan, Bleomycin, the Vinca alkaloids and their
analogs [Vincristine, Vinorelbine, Vindesine, Vintripol,
Vinxaltine, Ancitabine], 6-aminochrysene, and navelbine.
[0058] Other compounds useful in the application of the invention
are mimetics of taxol, eleutherobins, sarcodictyins,
discodermolides and epothiolones.
[0059] Taking into account these definitions, the present invention
is directed to pharmaceutical compositions in the form of
emulsions, micellar solutions or self-emulsifying drug delivery
systems which are substantially free of ethanol solvent.
[0060] The therapeutic agents of the compositions of this invention
can initially be solubilized in ethanol. However, the ethanol is
removed in order to form a substantially ethanol-free composition.
The ethanol concentration is less than 1% (w/v), preferably less
than 0.5%, and most preferably less than 0.3%. The therapeutic
agents can also be solubilized in methanol, propanol, chloroform,
isopropanol, butanol and pentanol. These solvents are also removed
prior to use.
[0061] The compositions of the invention contain .alpha.-tocopherol
as a carrier for therapeutic drugs, which can be administered to
animals or humans via intravascular, oral, intramuscular, cutaneous
and subcutaneous routes. Specifically, the emulsions can be given
by any of the following routes, among others: intraabdominal,
intraarterial, intraarticular, intracapsular, intracervical,
intracranial, intraductal, intradural, intralesional, intralocular,
intralumbar, intramural, intraocular, intraoperative,
intraparietal, intraperitoneal, intrapleural, intrapulmonary,
intraspinal, intrathoracic, intratracheal, intratympanic,
intrauterine, and intraventricular. The emulsions of the present
invention can be nebulized using suitable aerosol propellants which
are known in the art for pulmonary delivery of lipophilic
compounds.
[0062] In its first aspect, the invention is directed to the use of
.alpha.-tocopherol as the hydrophobic dispersed phase of emulsions
containing water insoluble, poorly water soluble therapeutic
agents, water soluble therapeutic agents which have been modified
to be less water soluble or mixtures thereof. Also called vitamin
E, .alpha.-tocopherol is not a typical lipid oil. It has a higher
polarity than most lipid oils, particularly triglycerides, and is
not saponifiable. It has practically no solubility in water.
[0063] In the second aspect, the invention is a an
.alpha.-tocopherol emulsion in the form of a self-emulsifying
system where the system is to be used for the oral administration
of water insoluble (or poorly water soluble or water soluble agents
modified to be less water soluble or mixtures thereof) drugs where
that is desired. In this embodiment, an oil phase with surfactant
and drug or drug mixture is encapsulated into a soft or hard
gelatin capsule. Suitable solidification agents with melting points
in the range of 40 to 60.degree. C. such as high molecular-weight
polyethylene glycols (MW>1000) and glycerides such as those
available under the trade name Gellucires (Gattefose Corp. Saint
Priest, France) can be added to allow filling of the formulation
into a hard gelatin capsule at high temperature. Semi-solid
formulations are formed upon room temperature equilbration. Upon
dissolution of the gelatin in the stomach and duodenum, the oil is
released and forms a fine emulsion with a mean droplet diameter of
between 2-5 microns spontaneously. The emulsion is then taken up by
the microvilli of the intestine and released into the
bloodstream.
[0064] In a third aspect, the invention comprises microemulsions
containing .alpha.-tocopherol. Microemulsions refer to a sub-class
of emulsions where the emulsion suspension is essentially clear and
indefinitely stable by virtue of the extremely small size of the
oil/drug microaggregates dispersed therein.
[0065] In a fourth aspect of the invention, PEGylated vitamin E
(TPGS) is used as a primary surfactant in emulsions of vitamin E.
PEGylated vitamin E is utilized as a primary surfactant, a
stabilizer and also as a supplementary solvent in emulsions of
vitamin E. Polyethylene glycol (PEG) is also useful as a secondary
solvent in the emulsions of this invention.
[0066] The .alpha.-tocopherol concentration of the emulsions of
this invention can be from about 2 to about 10% w/v. The ratio of
.alpha.-tocopherol to TPGS is optimally from about 1:1 to about
10:1 (w/w).
[0067] The emulsions of the invention may further include
surfactants such as ascorbyl-6 palmitate; stearylamine; sucrose
fatty acid esters and various vitamin E derivatives comprising
.alpha.-tocopherol nicotinate, tocopherol phosphate, and nonionic,
synthetic surfactant mixtures, containing a fluorine-containing
surfactant, such as the Zonyl brand series and a
polyoxypropylene-polyoxyethylene glycol nonionic block
copolymer.
[0068] The emulsions of the invention can comprise an aqueous
medium. The aqueous phase has an osmolality of approximately 300
mOsm and may include potassium or sodium chloride sorbitol,
mannitol, polyethylene glycol, propylene glycol albumin, polypep
and mixtures thereof. This medium can also contain various
additives to assist in stabilizing the emulsion or in rendering the
formulation biocompatible. Acceptable additives include acidifying
agents, alkalizing agents, antimicrobial preservatives,
antioxidants, buffering agents, chelating agents, suspending and/or
viscosity-increasing agents, and tonicity agents. Preferably,
agents to control the pH, tonicity, and increase viscosity are
included. Optimally, a tonicity of at least 250 mOsm is achieved
with an agent which also increases viscosity, such as sorbitol or
sucrose.
[0069] The emulsions of the invention for intravenous injection
have a particle size of 10 to 500 nm, preferably 10 to 200 nm and
most preferably 10 to 100 nm. For intravenous emulsions, the spleen
and liver will eliminate particles greater than 500 nm in size
through the RES.
[0070] A preferred form of the invention includes paclitaxel, a
very water-insoluble cytotoxin used in the treatment of uterine
cancer and other carcinomas. An emulsion composition of the present
invention comprises a solution of vitamin E containing paclitaxel
at a concentration of up to 20 mg/mL, four times that currently
available by prescription, and a biocompatible surfactant such that
the emulsion microdroplets are less than 0.2 microns and are
terminally sterilizable by filtration.
[0071] A further embodiment of the invention is a method of
treating carcinomas comprising the parenteral administration of a
bolus dose of paclitaxel in vitamin E emulsion with and without
PEGylated vitamin E by intravenous injection once daily or every
second day over a therapeutic course of several weeks. Such method
can be used for the treatment of carcinomas of the breast, lung,
skin and uterus.
[0072] The general principles of the present invention may be more
fully appreciated by reference to the following non-limiting
examples.
EXAMPLES
Example 1
Dissolution of Paclitaxel in .alpha.-tocopherol
[0073] .alpha.-Tocopherol was obtained from Sigma Chemical. Company
(St Louis Mo.) in the form of a synthetic dl-.alpha.-tocopherol of
95% purity prepared from phytol. The oil was amber in color and
very viscous. Paclitaxel was purchased from Hauser Chemical
Research (Boulder Col.), and was 99.9% purity by HPLC. Paclitaxel
200 mg was dissolved in 6 mL of dry absolute ethanol (Spectrum
Chemical Manufacturing Corp, Gardenia Calif.) and added to 1 gm
.alpha.-tocopherol. The ethanol was then removed by vacuum at
42.degree. C. until the residue was brought to constant weight.
Independent studies showed that the ethanol content was less than
0.3% (w/v).
[0074] The resultant solution was clear, amber and very viscous,
with a nominal concentration of 200 mg/gm (w/w) paclitaxel in
.alpha.-tocopherol. Higher concentrations of Paclitaxel (up to 400
mg/gm, w/w) can be solubilized in .alpha.-tocopherol.
Example 2
Anionic Surfactant Used to Prepare .alpha.-tocopherol Emulsions
[0075] Paclitaxel 2 gm in 10 gm of .alpha.-tocopherol, prepared as
described in Example 1, was emulsified with ascorbyl palmitate as
the triethanolamine salt by the following method. A solution
consisting of ascorbic acid 20 mM was buffered to pH 6.8 with
triethariolamine as the free base to from 2.times. buffer. 50 mL of
the 2.times. buffer was placed in a Waring blender. 0.5 gm of
ascorbyl-6-palmitate (Roche Vitamins and Fine Chemicals, Nutley
N.J.), an anionic surfactant, was added and the solution blended at
high speed for 2 min at 40.degree. C. under argon. The
.alpha.-tocopherol containing paclitaxel was then added into the
blender with the surfactant and buffer. Mixing was continued under
argon until a coarse, milky, pre-emulsion was obtained,
approximately after 1 min at 40.degree. C. Water for injection was
then added, bringing the final volume to 100 mL.
[0076] The pre-emulsion was transferred to the feed vessel of a
Microfluidizer Model 110Y (Microfluidics Inc, Newton Mass.). The
unit was immersed in a bath to maintain a process temperature of
approximately 60.degree. C. during homogenization, and was flushed
with argon before use. After priming, the emulsion was passed
through the homogenizer in continuous recycle for 10 minutes at a
pressure gradient of about 18 kpsi across the interaction head. The
flow rate was about 300 mL/min, indicating that about 25 passes
through the homogenizer resulted.
[0077] The resultant paclitaxel emulsion in an .alpha.-tocopherol
vehicle was bottled in amber vials under argon and stored with
refrigeration at 7.degree. C. and 25.degree. C. Samples were taken
at discrete time intervals for particle sizing and chemical
analysis.
[0078] Data taken with a Nicomp Model 376 Submicron Particle Sizer
(Particle Sizing Systems Inc, Santa Barbara Calif.) showed that the
emulsion had a mean particle diameter of 280 nm.
Example 3
Use of PEGylated Vitamin E (TPGS)
[0079] A ternary phase diagram was constructed for
.alpha.-tocopherol, PEGylated vitamin E (TPGS, vitamin-E
polyoxyethyleneglycol-1000-succinate- , obtained from Eastman
Chemical Co., Kingsport Tenn.), and water. TPGS was first melted at
42.degree. C. and mixed gravimetrically with .alpha.-tocopherol at
various proportions from 1 to 100% TPGS, the balance being
.alpha.-tocopherol. Mixtures were miscible at all concentrations.
Water was then added to each mixture in such a way that the final
water concentration was increased stepwise from zero to 97.5%. At
each step, observations were made of the phase behavior of the
mixture. As appropriate, mixing was performed by vortexing and
sonication, and the mixture was heated or centrifuged to assess its
phase composition.
[0080] A broad area of biphasic o/w emulsions suitable for
parenteral administration was found at water concentrations above
80%. The emulsions formed were milky white, free flowing liquids
that contained disperse .alpha.-tocopherol microparticles
stabilized by non-ionic surfactant. Also in this area,
microemulsions potentially suitable as drug carriers were observed
at TPGS to oil ratios above about 1:1. At lower water content, a
broad area containing transparent gels (reverse emulsions) was
noted. Separating the two areas (high and low water content) is an
area composed of opaque, soap-like liquid crystals.
[0081] Phase diagrams of .alpha.-tocopherol with surfactant
combinations, for example TPGS with a nonionic, anionic or cationic
co-surfactant (for example glutamyl stearate, ascorbyl palmitate or
Pluronic F-68), or drug can be prepared in a similar manner.
Example 4
.alpha.-Tocopherol Emulsion for Intravenous Delivery of
Paclitaxel
[0082] A formulation of the following composition was prepared:
1 Paclitaxel 1.0 gm % .alpha.-tocopherol 3.0 gm % TPGS 2.0 gm %
Ascorbyl-6-Palmitate 0.25 gm % Sorbitol 5.0 gm % Triethanolamine to
pH 6.8 Water qs to 100 mL
[0083] The method of preparation was as follows: synthetic
.alpha.-tocopherol (Roche Vitamins, Nutley N.J.), paclitaxel
(Hauser, Boulder Col.), ascorbyl 6-palmitate (Aldrich Chemical Co,
Milwaukee Wis.) and TPGS were dissolved in 10 volumes of anhydrous
undenatured, ethanol (Spectrum Quality Products, Gardenia Calif.)
with heating to 40-45.degree. C. The ethanol was then drawn off
with vacuum until no more than 0.3% remained by weight.
[0084] Pre-warmed aqueous solution containing a biocompatible
osmolyte and buffer were added with gentle mixing and a white milk
formed immediately. This mixture was further improved by gentle
rotation for 10 minutes with continuous warming at 40-45.degree. C.
This pre-mixture at about pH 7 was then further emulsified as
described below.
[0085] The pre-mixture at 40-45.degree. C. was homogenized in an
Avestin C5 homogenizer (Avestin, Ottawa Canada) at 26 Kpsi for 12
minutes at 44.degree. C. The resultant mixture contained
microparticles of .alpha.-tocopherol with a mean size of about 200
nm. Further pH adjustment was made with an alkaline 1 M solution of
triethanolamine (Spectrum Quality Products).
[0086] In order to avoid gelation of the TPGS during the early
stage of emulsification, all operations were performed above
40.degree. C. and care was taken to avoid exposure of the solutions
to cold air by covering all vessels containing the mixture.
Secondly, less than 2% TPGS should generally be dissolved in
.alpha.-tocopherol oil before pre-emulsification, the balance of
the TPGS being first dissolved in the aqueous buffer before the
pre-emulsion is prepared. The solution gels at concentrations of
TPGS higher than 2%.
[0087] Physical stability of the emulsion was then examined by
placing multiple vials on storage at 4.degree. C. and 25.degree. C.
Over several months, vials were periodically withdrawn for particle
sizing. Mean particle size, as determined with the Nicomp Model 370
(Particle Sizing Systems, Santa Barbara Calif.), is shown for the
two storage temperatures in FIG. 1. The particle size distribution
was bi-modal.
Example 5
Chemical Stability of Paclitaxel in an .alpha.-tocopherol
Emulsion
[0088] After emulsification, the formulation of Example 4 was
analyzed for paclitaxel on a Phenosphere CN column (5 microns,
150.times.4.6 mm). The mobile, phase consisted of a methanol/water
gradient, with a flow rate of 1.0 mL/min. A UV detector set at 230
nm was used to detect and quantitate paclitaxel. A single peak was
detected (FIG. 2), which had a retention time and mass spectrogram
consistent with native reference paclitaxel obtained from Hauser
Chemical (Boulder Col.).
[0089] Chemical stability of the emulsion of example 4 was examined
by HPLC during storage. The data of FIG. 3 demonstrate that
paclitaxel remains stable in the emulsion for periods of at least 3
months, independent of the storage temperature. Taken together, the
data of FIG. 2 and 3 demonstrate successful retention of drug
potency and emulsion stability when stored at 4.degree. C. for a
period of at least 3 months.
Example 6
Paclitaxel Emulsion Formulation QWA
[0090] An emulsion of paclitaxel 10 mg/ml for intravenous drug
delivery, having the following composition, was prepared as
described in Example 4.
2 Paclitaxel 1.0 gm % .alpha.-tocopherol 3.0 gm % TPGS 1.5 gm %
Ascorbyl-6-Palmitate 0.25 gm % Sorbitol 4.0 gm % Triethanolamine to
pH 6.8 Water qs to 100 mL
Example 7
Paclitaxel Emulsion Formulation QWB
[0091] A second emulsion of paclitaxel 10 mg/ml for intravenous
drug delivery, having the following composition, was prepared as
described in Example 4.
3 Paclitaxel 1.0 gm % .alpha.-tocopherol 3.0 gm % TPGS 1.5 gm %
Solutol HS-15 1.0 gm % Sorbitol 4.0 gm % Triethanolamine to pH 6.8
Water qs to 100 mL
[0092] Solutol HS-15 is a product of BASF Corp, Mount Olive
N.J.
Example 8
10 mg/mL Paclitaxel Emulsion Formulation QWC
[0093] A third emulsion formulation of paclitaxel 10 mg/ml was
prepared as follows using Poloxamer 407 (BASF Corp, Parsippany
N.J.) as a co-surfactant.
4 Paclitaxel 1.0 gm % .alpha.-tocopherol 6.0 gm % TPGS 3.0 gm %
Poloxamer 407 1.0 gm % Sorbitol 4.0 gm % Triethanolamine to pH 6.8
Water for injection qs to 100 mL
[0094] In this example, 1.0 gm Poloxamer 407 and 1.0 gm paclitaxel
were dissolved in 6.0 gm .alpha.-tocopherol with ethanol 10 volumes
and gentle heating. The ethanol was then removed under vacuum.
Separately, an aqueous buffer was prepared by dissolving 3.0 gm
TPGS and 4.0 gm sorbitol in a final volume of 90 mL water for
injection. Both oil and water solutions were warmed to 45.degree.
C. and mixed with sonication to make a pre-emulsion. A vacuum was
used to remove excess air from the pre-emulsion before
homogenization.
[0095] Homogenization was performed in an Avestin C5 as already
described. The pressure differential across the homogenization
valve was 25 kpsi and the temperature of the feed was 42-45.degree.
C. A chiller was used to ensure that the product exiting the
homogenizer did not exceed a temperature of 50.degree. C. Flow
rates of 50 mL/min were obtained during homogenization. After about
20 passes in a recycling mode, the emulsion became more
translucent. Homogenization was continued for 20 min. Samples were
collected and sealed in vials as described before. A fine
.alpha.-tocopherol emulsion for intravenous delivery of paclitaxel
was obtained. The mean particle diameter of the emulsion was 77 nm.
Following 0.22.mu. sterile filtration through a 0.22 micron
Durapore filter (Millipore Corp, Bedford Mass.), the emulsion was
filled in vials and stored at 4.degree. C. until used for
intravenous injection.
Example 9
5 mg/mL Paclitaxel Emulsion Formulation QWC
[0096] An additional emulsion of paclitaxel was prepared as
described in Example 8 but incorporating 5 instead of 10 mg/ml of
the drug. The composition of this emulsion is as follows:
5 Paclitaxel 0.5 gm % .alpha.-tocopherol 6.0 gm % TPGS 3.0 gm %
Poloxamer 407 1.0 gm % Sorbitol 4.0 gm % Triethanolamine to pH 6.8
Water for injection qs to 100 mL
[0097] Following homogenization as described in example 8, a
somewhat translucent emulsion of .alpha.-tocopherol and paclitaxel
with a mean particle diameter of 52 nm was obtained. Following
sterile filtration through a 0.22 micron Durapore filter (Millipore
Corp, Bedford Mass.), the emulsion was filled in vials and stored
at 4.degree. C. until used for intravenous injection. Drug losses
on filtration were less than 1%.
Example 10
Paclitaxel Emulsion Formulation QWD
[0098] A fifth emulsion of .alpha.-tocopherol for intravenous
administration of paclitaxel was prepared as follows:
6 Paclitaxel 0.5 gm % .alpha.-tocopherol 6.0 gm % TPGS 3.0 gm %
Poloxamer 407 1.5 gm % Polyethyleneglycol 200 0.7 gm % Sorbitol 4.0
gm % Triethanolamine to pH 6.8 Water for injection qs to 100 mL
[0099] Synthetic .alpha.-tocopherol USP-FCC obtained from Roche
Vitamins (Nutley, N.J.) was used in this formation.
Polyethyleneglycol 200 (PEG-200) was obtained from Sigma Chemical
Co.
[0100] Following homogenization, a somewhat translucent emulsion
with a mean particle diameter of 60 nm was obtained. Following
0.22.mu. sterile filtration through a 0.22 micron Durapore filter
(Millipore Corp, Bedford Mass.), the emulsion was filled in vials
and stored at 4.degree. C. until used for intravenous injection.
Drug losses on filtration were less than 1%.
Example 11
Dissolution of Paclitaxel in TPGS and Preparation of Micellar
Solutions
[0101] We observed good solubility of paclitaxel in TPGS, about 100
mg drug per 1.0 gm of TPGS. Micellar solutions of TPGS containing
paclitaxel were prepared as follows. A stock solution of paclitaxel
in TPGS was made up by dissolving 90 mg paclitaxel in 1.0 gm TPGS
at 45.degree. C. with ethanol, which was then removed under vacuum.
Serial dilutions were then prepared by diluting the paclitaxel
stock with additional TPGS to obtain paclitaxel in TPGS at
concentrations of 0.1, 1, 5, 10, 25, 50, 75 and 90 mg/mL. Using
fresh test tubes, 100 mg of each paclitaxel concentration in TPGS
was dissolved in 0.9 mL water. All test tubes were mixed by vortex
and by sonication at 45.degree. C. Clear micellar solutions in
water were obtained corresponding to final paclitaxel
concentrations of 0.01, 0.1, 0.5, 1.0, 2.5, 5.0, 7.5 and 9.0
mg/mL.
[0102] A Nicomp Model 370 laser particle sizer (Particle Sizing
Systems, Santa Barbara Calif.) was used to examine the solutions.
Particle sizes on the order of 10 nm were obtained, consistent with
the presence of micelles of TPGS and paclitaxel.
[0103] Micellar solutions of paclitaxel in TPGS containing up to
2.5 mg/mL paclitaxel were stable for at least 24 hr whereas those
at 5.0, 7.5 and 9.0 mg/mL were unstable and drug crystals formed
rapidly and irreversibly. These observations imply that paclitaxel
remains solubilized only in the presence of an
.alpha.-tocopherol-rich domain within the emulsion particles. Thus,
an optimum ratio of .alpha.-tocopherol to TPGS is needed in order
to produce emulsions in which higher concentrations of paclitaxel
can be stabilized.
[0104] When adjusted to the proper tonicity and pH, micellar
solutions have utility for slow IV drip administration of
paclitaxel to cancer patients, although the AUC is expected to be
low.
[0105] The utility of TPGS in .alpha.-tocopherol emulsions is a
synergy of several desirable characteristics. First, it has its own
affinity for paclitaxel, probably by virtue of the
.alpha.-tocopherol that makes up the hydrophobic portion of its
molecular structure. Secondly, interfacial tension of TPGS in water
with .alpha.-tocopherol is about 10 dynes/cm, sufficient to
emulsify free .alpha.-tocopherol, especially when used with a
co-surfactant. Third, polyoxyethylated surfactants such as TPGS,
have well established, superior properties as a "stealth coat" for
injectable particles, by dramatically reducing trapping of the
particles in the liver and spleen, as is well known in the art. But
the unexpected and unique finding with TPGS as a surfactant for
.alpha.-tocopherol emulsions, was the finding of all three
desirable characteristics in a single molecule. An additional
advantage of TPGS is the fact that it forms stable self-emulsifying
systems in mixtures with oils and solvents such as propylene glycol
and polyethylene glycol, suggesting a synergy when used with
.alpha.-tocopherol for oral drug delivery.
[0106] When adjusted to the proper tonicity and pH, micellar
solutions have utility for slow IV drip administration of
paclitaxel to cancer patients, although the AUC is expected to be
low.
Example 12
20 mg/mL Paclitaxel Emulsion Formulation
[0107] A coarse, emulsion containing 20 mg/mL paclitaxel in
.alpha.-tocopherol was obtained with 5% .alpha.-tocopherol and 5%
TPGS by the methods described in Example 4, simply by increasing
the concentrations. No effort was made to test higher
concentrations simply because no further increase is necessary for
clinically useful intravenous-emulsions.
Example 13
Use of Other PEG Surfactants in .alpha.-tocopherol Emulsions
[0108] A variety of other pegylated surfactants, for example Triton
X-100, PEG 25 propylene glycol stearate, Brij 35 (Sigma Chemical
Co), Myrj 45, 52 and 100, Tween 80 (Spectrum Quality Products), PEG
25 glyceryl trioleate (Goldschmidt Chemical Corp, Hopewell Va.),
have utility in emulsifying .alpha.-tocopherol.
[0109] However, experiments with other pegylated surfactants failed
to convincingly stabilize paclitaxel in an .alpha.-tocopherol
emulsion. To demonstrate the unique utility of TPGS, three
emulsions were prepared as described in Example 9, but Tween 80 and
Myrj 52 were substituted for TPGS as the primary surfactant in
separate emulsions. These two surfactants were chosen because Tween
80 and Myrj 52 have HLB values essentially equivalent to TPGS and
make reasonably good emulsions of .alpha.-tocopherol. However, when
5 mg/mL paclitaxel was included in the formulation, drug
crystallization was noted very rapidly after preparation of the
pre-emulsion, and the processed emulsions of Tween 80 and Myrj 52
were characterized as coarse, containing rod-shaped particles up to
several microns in length, consistent with crystals of paclitaxel.
Unlike the TPGS emulsion, which passed readily through a 0.22
micron filter with less than 1% loss of drug, the Tween and Myrj
emulsions were unfilterable because of the presence of this
crystalline drug material.
[0110] There are several possible explanations for the unexpected
improvement of the .alpha.-tocopherol paclitaxel emulsions with
TPGS. The drug has good solubility in TPGS, up to about 100 mg/mL.
Most likely it is the strength of the affinity of paclitaxel benzyl
side chains with the planar structure of the .alpha.-tocopherol
phenolic ring in the TPGS molecule that stabilizes the complex of
drug and carrier. In addition the succinate linker between the
.alpha.-tocopherol and PEG tail is a novel feature of this molecule
that distinguishes its structure from other PEGylated surfactants
tested.
Example 14
Poloxamer-based .alpha.-tocopherol Emulsion
[0111]
7 .alpha.-tocopherol 6.0 gm % Poloxamer 407 2.5 gm % Ascorbyl
Palmitate 0.3 gm % Sorbitol 6.0 gm % Triethanolamine to pH 7.4
Water qs to 100 mL
[0112] An .alpha.-tocopherol emulsion was prepared using Poloxamer
407 (BASF) as the primary surfactant. The white milky pre-mixture
was homogenized with continuous recycling for 10 minutes at 25 Kpsi
in a C5 homogenizer (Avestin, Ottawa Canada) with a feed
temperature of 45.degree. C. and a chiller loop for the product out
set at 15.degree. C. A fine, sterile filterable emulsion of
.alpha.-tocopherol microparticles resulted. However, when this
formulation was made with paclitaxel, precipitation of the
paclitaxel was noted following overnight storage in the
refringerator, again underlying the superior utility of TPGS as the
principle surfactant.
Example 15
Lyophilized Emulsion Formulation
[0113] Maltrin M100 (Grain Processing Corporation, Muscatine Iowa)
was added as a 2.times. stock in water to the emulsion of Example
14. Aliquots were then frozen in a shell freezer and lyophilized
under vacuum. On reconstitution with water, a fine emulsion was
recovered.
[0114] Lyophilized formulations have utility where the indefinite
shelf life of a lyophilized preparation is preferred. Lyophilizable
formulations containing other saccharides, such as mannitol,
albumin or PolyPep from Sigma Chemicals, St. Louis, Mo. can also be
prepared.
Example 16
In vitro Release of Paclitaxel from .alpha.-tocopherol
Emulsions
[0115] One of the desired characteristics of a drug delivery
vehicle is to provide sustained release of the incorporated drug, a
characteristic quite often correlated with improved
pharmacokinetics and efficacy. In particular, long-circulating
emulsions of paclitaxel can improve the delivery of the drug to
cancer sites in the body. We have surprisingly found that the
emulsions of the present invention do provide sustained release of
paclitaxel when compared to the only FDA-approved formulation of
paclitaxel at this time [Taxol.RTM., Bristol Myers Squibb(BMS),
Princeton N.J.]. Emulsions were prepared having paclitaxel
concentrations of 6 mg/mL (QWA) and 7 mg/mL (QWB). For comparison,
Taxol contains 6 mg/ml of paclitaxel dissolved in
ethanol:cremophore EL 1:1 (v/v). In vitro release of paclitaxel
from the different formulations into a solution of
phosphate-buffered saline (PBS) at 37.degree. C. was monitored
using a dialysis membrane that is freely permeable to paclitaxel
(MW cut-off of 10 kilodaltons). Quantification of the drug in pre-
and post-dialysis samples was performed by HPLC. Drug release
profiles in terms of both percent release and concentration of
paclitaxel released over time were generated. As can be seen from
the data in FIG. 4, less than 5% of paclitaxel was dialyzed from
the emulsions over 24 hr, whereas about 12% was recovered outside
the dialysis bag from the marketed BMS formulation. This indicates
that drug release from the emulsion was significantly slowed
relative to the commercially available solution.
Example 17
Biocompatibility of .alpha.-tocopherol Emulsions Containing
Paclitaxel
[0116] An acute single-dose toxicity study was performed. Mice
20-25 gm each were purchased and acclimatized in an approved animal
facility. Groups of mice (n=3) received doses of the formulation
containing from 30 to 90 mg/kg paclitaxel in the .alpha.-tocopherol
emulsion prepared as described in Example 6. All injections were
given intravenously by tailvein bolus.
[0117] Although all injections were given by bolus IV push, no
deaths or immediate toxicity were observed at any dose, even at 90
mg/kg. The results for body weight are shown in Table 1. Weight
loss was 17% in the highest group but all groups, even at 90 mg/kg,
recovered or gained body weight over a period of 10 days post
injection.
[0118] A vehicle toxicity study was also done. Animals receiving
drug-free emulsion grew rapidly, and gained slightly more weight
than animals receiving saline or not injected. This was attributed
to the vitamin and calorie content of the formulation.
[0119] We observed a maximal tolerable dose (MTD) for paclitaxel of
greater than 90 mg/kg (Table 1), with no adverse reactions noted.
This is more than double the best literature values reported, in
which deaths were observed at much smaller doses. Taxol, the
FDA-approved BMS formulation, causes death in mice at bolus
intravenous doses of 10 mg/kg, a finding repeated in our hands. In
the rat, BMS Taxol was uniformly fatal at all dilutions and dose
regimes we tested. In contrast, the composition of Example 6 was
well tolerated in rats, and is even improved over Taxotere, a less
toxic paclitaxel analogue commercially marketed by Rhone-Poulenc
Rorer.
[0120] One possible explanation for the high drug tolerance is that
the emulsion is behaving as a slow-release depot for the drug as
suggested from the in vitro release data in Example 16.
8TABLE 1 Average Body Weight Change of Mice Treated with Paclitaxel
Emulsion Treatment Number BW Change (gm) (dose, mg/kg) of Animals
Day 2 Day 7 Saline 4 1.0 3.4 Vehicle 4 1.2 3.5 Paclitaxel Emulsion
2 -1.0 2.2 (QWA) (36.3) Paclitaxel Emulsion 4 -1.8 1.7 (QWA) (54.4)
Paclitaxel Emulsion 4 -1.5 1.6 (QWA) (72.6) Paclitaxel Emulsion 1
-1.6 (QWA) (90.7)
Example 18
Efficacy Evaluation of Paclitaxel Emulsion
[0121] The paclitaxel emulsion of Example 6 was also evaluated for
efficacy against staged B16 melanoma tumors in nude mice and the
data is shown in Table 2. Once again, the marketed product BMS
Taxol was used as a reference formulation. Tumor cells were
administered subcutaneously and therapy started by a tail vein
injection at day 4 post-tumor administration at the indicated
dosing schedule. Efficacy was expressed as percent increase in
life-span (% ILS).
[0122] The following conclusions can be drawn from the data in
Table 2: a) an increased life span of about 10% was obtained by
administration of BMS Taxol at 10 mg/kg Q2Dx4, b) %ILS values
improved to 30-50% by administration of the .alpha.-tocopherol
emulsion of paclitaxel at 30, 40 or 50 mg/kg Q2Dx4, dose levels
made possible by the higher MTD, c) a nice dose response was
observed when the emulsion was administered at 30, 50 and 70 mg/kg
Q4Dx3, with about 80% ILS being observed at 70 mg/kg and, d) even
at 90 mg/kg dosed only once at day 4, there was about 36% ILS.
These data clearly illustrate the potential of the emulsions of the
present invention to substantially improve the efficacy of
paclitaxel.
Example 19
Efficacy Evaluation of Paclitaxel Emulsions
[0123] The emulsions of examples 6, 7 and 8 (QWA, QWB and QWC
respectively) were compared for efficacy against B16 melanoma in
mice; BMS taxol was again used as a reference formulation. Methods
essentially identical to those of Example 18 were used. The data
from this study is summarized in Table 3. Efficacy was expressed
as: a) percent tumor growth inhibition (% T/C, where T and C stand
for treated and control animals, respectively); b) tumor growth
delay value (T-C), and c) log cell kill which is defined as the
ratio of the T-C value over 3.32.times.tumor doubling time. The
latter parameter for this particular tumor model was calculated to
be 1.75 days. As can be seen from the results in Table 3, all
measures of efficacy: tumor growth inhibition, tumor growth delay
value and log cell kill demonstrate superior efficacy of
.alpha.-tocopherol emulsions as a drug delivery vehicle over BMS
Taxol, particularly when the emulsions were dosed every four days
at 70 mg/kg. As explained in Example 16, this increased efficacy is
likely a result of improved drug biocompatibility and/or sustained
release.
9TABLE 2 Survival of Mice with B16 Tumors Treated with QWA and BMS
Taxol Mean Survival % ILS.sup.b Time, Days (vs vehicle) Treatment
Group & Schedule (Mean .+-. S.E.M.sup.a) (Mean .+-. S.E.M)
Vehicle Control (Days 4, 8, 12) 13.2 .+-. 0.9 -- Saline Control
(Days 4, 8, 12) 15.8 .+-. 1.2 19.7 .+-. 8.6 BMS Taxol (10 mg/kg)
16.4 .+-. 0.7 24.2 .+-. 5.4 (Days 4, 6, 8, 10) QWA (30 mg/kg) (Days
4, 6, 8) 19.2 .+-. 1.4 45.4 .+-. 10.3 QWA (40 mg/kg) (Days 4, 6, 8)
21.3 .+-. 1.4 61.4 .+-. 10.3 QWA (50 mg/kg) (Days 4, 6, 8) 18.8
.+-. 0.7 42.4 .+-. 5.7 QWA (30 mg/kg) (Days 4, 8, 12) 15.3 .+-. 0.8
15.9 .+-. 6.4 QWA (50 mg/kg) (Days 4, 8, 12) 20.7 .+-. 1.3 56.8
.+-. 9.5 QWA (70 mg/kg) (Days 4, 8, 12) 24.2 .+-. 0.9 83.3 .+-. 6.4
QWA (90 mg/kg) (Day 4 only) 18.0 .+-. 0.6 36.4 .+-. 4.4 .sup.aSEM =
Standard Error of Mean .sup.b% ILS = % Increase in Lifespan = [(T -
C)/C] .times. 100 where: T = mean survival of treated C = mean
survival of control according to the NCI standards an ILS value
greater than 50% indicates significant anti-tumor activity.
[0124] T=mean survival of treated
[0125] C=mean survival of control
[0126] according to the NCI standards an ILS value greater than 50%
indicates significant anti-tumor activity.
10TABLE 3 Comparison of 3 paclitaxel emulsions and BMS taxol
against early-stage B16 melanoma Total Median tumor Median tumor
wt. Dosage Dosing Schedule Dose wt. on day 15 on day 18 mg % T/C T
- C Log cell Test Article mg/kg/day (days) (mg/kg) (mg) (range) Day
15 (days) kill total Control 0 4, 6, 8, 10 0 836 2139 -- -- -- BMS
Taxol 20 4, 6, 8, 10 80 383 1217 46 2 0.34 QWA 20 4, 6, 8, 10 80
381 1197 46 2 0.34 QWA 40 4, 6, 8, 10 160 104 306 12 7 1.2 QWA 70
4, 8, 12, 16, 20 350 15 11 -2 QWB 20 4, 6, 8, 10 80 197 653 24 5
0.86 QWB 30 4, 6, 8, 10 120 139 449 17 5 0.86 QWB 40 Toxic QWC 20
4, 6, 8, 10 80 319 848 34 3 0.52 QWC 40 4, 6, 8, 10 160 53 194 6 8
1.4 QWC 70 4, 8, 12, 16, 20 350 33 66 4 >15 >2.6 Tumor
Doubling Time calculated to be 1.75 days. % T/C = Tumor Growth
Inhibition (Day 15) = (median tumor wt. or treated/median tumor wt.
control) .times. 100 T - C = Tumor Growth Delay value = median time
for treatment group (T) and control group (C) tumors to reach a
predetermined size (usually 750-1000 mg) Log cell kill = (T - C
value)/(3.32 .times. tumor doubling time)
Example 20
Self-emulsification of an .alpha.-tocopherol/Tagat TO Mixture
[0127] .alpha.-tocopherol 2.0 gm and Tagat TO (Goldschmidt Chemical
Corp, Hopewell Va.) 800 mg were dissolved together. About 80 mg of
the oily mixture was transferred to a test tube and water was then
added. With gentle hand mixing, there was immediate development of
a rich milky emulsion, consistent with "self-emulsifying systems"
proposed as drug delivery systems, in which surfactant-oil mixtures
spontaneously form an emulsion upon exposure to aqueous media.
Example 21
Self-emulsifying Formulation Containing Paclitaxel
[0128] Paclitaxel 50 mg/ml was prepared in .alpha.-tocopherol by
the method described in Example 1. Tagat TO 20% (w/w) was added.
The resultant mixture was clear, viscous and amber in color. A 100
mg quantity of the oily mixture was transferred to a test tube. On
addition of 1 mL of water, with vortex mixing, a fine emulsion
resulted.
Example 22
Self-emulsifying Formulation of Paclitaxel
[0129] Paclitaxel 50 mg/ml was prepared in .alpha.-tocopherol by
the method described in Example 1. After removal of the ethanol
under vacuum, 20% TPGS and 10% polyoxyethyleneglycol 200 (Sigma
Chemical Co) were added by weight. A demonstration of the
self-emulsification ability of this system was then performed by
adding 20 mL of deionized water to 100 mg of the oily mixture at
37.degree. C. Upon gentle mixing, a white, thin emulsion formed,
consisting of fine emulsion particles demonstrated with the Malvern
Mastersizer (Malvern Instruments, Worcester Mass.) to have a mean
size of 2 microns, and a cumulative distribution 90% of which was
less than 10 microns.
Example 23
Etoposide Emulsion Formulation in .alpha.-tocopherol
[0130] Etoposide 4 mg (Sigma Chemical Co) was dissolved in the
following surfactant-oil mixture:
11 Etoposide 4 mg .alpha.-tocopherol 300 mg TPGS 50 mg Poloxamer
407 50 mg
[0131] Ethanol and gentle warming was used to form a clear amber
solution of drug in oil. The ethanol was then removed under
vacuum.
[0132] A pre-emulsion was formed by adding 4.5 mL of water
containing 4% sorbitol and 100 mg TPGS at 45.degree. C. with
sonication. The particle size was further reduced by processing in
an Emulsiflex 1000 (Avestin, Ottawa Canada). The body of the
Emulsiflex 1000 was fitted with a pair of 5 mL syringes and the
entire apparatus heated to 45.degree. C. before use. The 5 mL of
emulsion was then passed through it by hand approximately 10 times.
A free flowing, practical emulsion of etoposide in an
.alpha.-tocopherol vehicle resulted.
[0133] We note that the solubilized form of etopside in
.alpha.-tocopherol can also be used as an oral dosage form by
adaption of the methods of the preceding examples.
Example 24
Dissolution of Ibuprofen or Griseofulvin in .alpha.-tocopherol
[0134] Ibuprofen is a pain-killer, and may be administered by
injection when required if there is danger that the drug will
irritate the stomach. The following solution of ibuprofen in
.alpha.-tocopherol may be emulsified for intravenous
administration.
[0135] Ibuprofen (Sigma Chemicals), 12 mg. crystalline, dissolved
without solvent in .alpha.-tocopherol, 120 mg, by gentle heating.
The resultant 10% solution of ibuprofen in vitamin E can be
emulsified by the method s described in Examples 4, 6, 7, 8 or
22.
[0136] An antifungal compound, griseofulvin, 12 mg, was first
dissolved in 3 mL of anhydrous ethanol; .alpha.-tocopherol was then
added, 180 mg, and the ethanol was removed with gentle heating
under vacuum. The resultant solution of griseofulvin in
.alpha.-tocopherol is clear and can be emulsified by the methods
described in Examples 4, 6, 7, 8 or 22.
Example 25
Vitamin E Succinate Emulsion Formulation
[0137] Vitamin E succinate has been suggested as a therapeutic for
the treatment of lymphomas and leukemias and for the
chemoprevention of cancer. The following is a composition and
method for the emulsification of vitamin E succinate in
.alpha.-tocopherol. Sucrose ester S1170 is a product of Mitsubishi
Kagaku Foods Corp, Tokyo Japan. Vitamin E succinate, as the free
acid, was obtained as a whitish powder from ICN Biomedicals,
Aurora, Ohio. Emulsions incorporating other surfactants such as
pluronics, and TPGS along with .alpha.-tocopherol and
.alpha.-tocopherol succinate can be prepared in a similar manner
with and without a therapeutic agent.
[0138] .alpha.-Tocopherol 8 gm and vitamin E succinate 0.8 gm were
dissolved together in ethanol in a round bottom flask. After
removal of the solvent, 100 mL of an aqueous buffer was added. The
alkaline buffer consisting of 2% glycerol, 10 mM triethanolamine,
and 0.5 gm % sucrose ester S1170. After mixing for 2 min, the
pre-emulsion was transferred to an Avestin Model C-5 homogenizer
and homogenization was continued for about 12 minutes at a process
feed temperature of 58.degree. C. The pressure differential across
the interaction head was 25 to 26 kpsi. During homogenization, pH
was carefully monitored, and adjusted as required to pH 7.0. Care
was taken to exclude oxygen during the process. A fine white
emulsion resulted.
Example 26
.alpha.-tocopherol Levels in Esters
[0139] Levels of .alpha.-tocopherol in commercially available
esters: tocopherol-acetate, -succinate, -nicotinate, -phosphate and
TPGS were either provided by the vendor or determined by HPLC. The
concentration of free .alpha.-tocopherol in these solutions is less
than 1.0%, generally less than 0.5%.
Example 27
Resveratrol Emulsion Formulation
[0140] Resveratrol is a cancer chemopreventative first discovered
as an extract of grape skins. It has been proposed as a dietary
supplement.
[0141] Resveratrol was obtained from Sigma Chemical Co. While it
dissolved poorly in ethanol, upon addition of 10 mg resveratrol,
100 mg of .alpha.-tocopherol, 100 mg TPGS and ethanol, a clear
solution formed rapidly. Upon removal of the ethanol, a clear amber
oil remained.
[0142] The oily solution of resveratrol can be formulated as a
self-emulsifying system for oral delivery by the various methods of
the preceding examples.
Example 28
Muramyl Dipeptide Formulation
[0143] Muramyl dipeptides are derived from mycobacteria and are
potent immunostimulants representative of the class of muramyl
peptides, mycolic acid and lipopolysaccharides. They have use, for
example, in the treatment of cancer, by stimulating the immune
system to target and remove the cancer. More recently, muroctasin,
a synthetic analog, has been proposed to reduce non-specific side
effects of the bacterial wall extracts.
[0144] N-acetylmuramyl-6-O-steroyl-1-alanyl-d-isoglutamine was
purchased from Sigma Chemical Co. and 10 mg was dissolved in 100 mg
.alpha.-tocopherol and 80 mg TPGS. Ethanol was used as a co-solvent
to aid in dissolution of the dipeptide, but was removed by
evaporation under vacuum, leaving a clear solution in
.alpha.-tocopherol and surfactant.
[0145] This oil solution of the drug can be emulsified for
parenteral administration by the various methods of the preceding
examples.
Example 29
Alcohol-containing Emulsion
[0146] In attempting to adapt the teachings of PCT WO 95/11039 to
the oral administration of paclitaxel, the following formulation
was made.
12 Paclitaxel 0.125 gm .alpha.-tocopherol 0.325 gm TPGS 0.425 gm
Ethanol 0.125 gm
[0147] As before, paclitaxel was dissolved in a .alpha.-tocopherol
and TPGS with ethanol, which was then removed under vacuum. By dry
weight, residual ethanol was less than 3 mg (0.3% w/w). Fresh
anhydrous ethanol 0.125 gm was then added back to the formulation.
After mixing the suitability of the formulation for oral
administration, as in a gelatin capsule, was simulated by the
following experiment. An aliquot of 100 mg of the free-flowing oil
was added to 20 mL of water at 37.degree. C. and mixed gently with
a vortex mixer. A fine emulsion resulted. But after twenty minutes,
microscopy revealed the growth on large numbers of crystals in
rosettes, characteristic of paclitaxel precipitation. It was
concluded that this formulation was not suitable for oral
administration of paclitaxel because large amounts of the drug
would be in the form of crystals on entry into the duodenum, where
it would be prevented from uptake because of its physical form. We
speculate that the excess of ethanol, in combination with the high
ratio of TPGS to .alpha.-tocopherol, is responsible for the
observed crystallization of the drug from this formulation.
Example 30
Alcohol-containing .alpha.-tocopherol Emulsion
[0148] In attempting to adapt the teachings of PCT WO 95/11039 to
the intravenous administration of paclitaxel, the following
formulation was made:
13 Paclitaxel 0.050 gm .alpha.-tocopherol 0.100 gm Lecithin 0.200
gm Ethanol 0.100 gm Butanol 0.500 gm
[0149] As before, paclitaxel was dissolved in .alpha.-tocopherol
and TPGS with ethanol, which was then removed under vacuum. By dry
weight, residual ethanol was less than 2 mg (0.5% w/w). Fresh
anhydrous ethanol 0.100 gm and n-butanol 0.500 gm was then added
back to the formulation. A clear oil resulted. The injection
concentrate was tested for biocompatibility in administration by
standard pharmaceutical practice of admixture and saline. About 200
mg of the oil was dropped into 20 mL of saline and mixed. Large
flakes of insoluble material developed immediately and the greatest
amount of material formed dense deposits on the walls of the test
tube. The mixture was clearly unsuitable for parenteral
administration by any route, and we speculate that this is so
regardless of the identity of the drug contained in the
formulation. By trial and error we have learned that lecithin is a
poor choice as surfactant for .alpha.-tocopherol by virtue of its
low HLB (around 4). Other successful examples described here for
fine emulsions suitable for parenteral administration were all made
with high HLB surfactants. These surfactants include TPGS (HLB
around 17), Poloxamer 407 (HLB about 22) and Tagat TO (HLB about
14.0). In general, we found that .alpha.-tocopherol emulsification
is best performed with principal surfactants of HLB>10,
preferably greater than 12. Lecithin is not in this class, although
it could be used as a co-surfactant. In comparison, typical o/w
emulsions of triglycerides are made with surfactants of HLB between
7 and 12, demonstrating that .alpha.-tocopherol emulsions are a
unique class by virtue of the polarity and extreme hydrophobicity
of the .alpha.-tocopherol, factors that also favor the solubility
of lipophilic and slightly polar lipophilic drugs in
.alpha.-tocopherol. See Emulsions: Theory and Practice, 2nd Ed.
p.248 (1985).
* * * * *