Note: Descriptions are shown in the official language in which they were submitted.
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NanoParticles in Photodynamic Therapy
.
The present invention relates to a pharmaceutical composition comprising the zinc phthalo-
cyanine complex and a polymer which is suitable for the formation of nanoparticles, to a
process for the preparation of said pharmaceutical composition and to the therapeutic use
thereof, e.g. in photodynamic therapy.
Both the zinc phthalocyanine complex and its therapeutic use in photodynamic therapy for
the treatment of tumors are known, q.v. J.D.Spikes, Photochem. Photobiol. 43, 691 (1986J.
The zinc phthalocyanine complex is administered in vivo intraperitoneally to mice or rats in
the form of an aqueous suspension, and the carcinoma induced in experimental animals is
irradiated with high-energy light, preferably with concentrated visible light (LASER).
The use of intraperitoneal dosage forms in human therapy is considered inacceptable in
view of serious pains caused when piercing the abdominal cavity. The skillful use of the
injection syringe in this difficult mode of administration is strictly mandatory for the practicing
physician. Several attempts have, therefore, been made to find safer and better dosage
forms which are more acceptable to the patient and the administering physician.
The intravenous dosage form allows the systemic distribution of the active ingredient, but
requires solubility of the active agent in the aqueous injection fluid. The zinc phthalocyanine
complex, however, is characterized by extremely low water solubility and insolubility in
almost all organic solvents. As an exception to this observation, it has been found that the
zinc phthalocyanine complex is soluble in some selected polar aprotic agents such as
dimethyl sulfoxide, N-methyl-2-pyrrolidone or pyridine.
To overcome these solubility problems, it has been proposed to solubilize the zinc phthalo-
cyanine complex in the aqueous phase by the addition of a vehicle. By using, for example,
phospholipids as solubilizers, the complex can be solubilized by encapsulation in uni-
lamellar liposomes which are homogeneously dispersible in aqueous phase, q.v. Reddi et
al., Br. J. Cancer, Vol. 56, pages 597-600 (1987J.
This homogeneous liposome dispersion is nevertheless still unsuitable for the purposes of
intravenous administration to humans because the dispersion is prepared in accordance
with the so-called injection method using relatively large amounts of toxic pyridine, q.v.
G. Valduga et al., J. Inorg. Biochem. 59-65, Vol. 29 (1987).
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Pyridine is one of the few solvents in which the zinc phthalocyanine complex is at all
soluble. That solution is diluted with ethanol, and the pyridine-containing ethanolic solution
is injected at elevated temperature into water or a buffer solution. In accordance with that
method, a residue of the organic solvent will permanently remain in the aqueous phase as a
result of the formation of an azeotropic mixture, even if the toxic solvent pyridine is replaced
by less toxic organic solvents such as dimethyl sulfoxide or N-methyl-2-pyrroiidone.
The enc~psul~tion of the zinc phthalocyanine complex in liposomes formed from a phos-
pholipid mixture of selected phospholipids is disclosed in U.S. Patenf Speci~ication
5,270,053. A solvent-free dry preparation containing a homogeneous mixture of a synthetic,
substantially pure phosphatidyl choline derivative with a synthetic, substantially pure phos-
phatidyl serine derivative as well as the zinc phthalocyanine complex is dispersed in an
aqueous phase, and a liposome dispersion, primarily multilamellar liposomes, is sub-
sequently formed which is intravenously applicable.
These methods of encapsulating a pharmaceutical agent of low water-solubility in lipo-
somes, as well as other proposed methods, such as the incorporation in micelles, mixed
micelles, reversed micelles, microcapsules or microspheres have the clear advantage of
improved solubilization. Unfortunately, these advantages are again diminished by a range
of problems, including the low stability of the aqueous systems owing to the separation of
the phase into the individual components, insufficient amounts of encapsulated active
agent, the strong dependency of the particle size on the method employed, unsatisfactory
uniformity and insufficient reproducibility of the products obtained, and other problems.
Surprisingly, it has now been found that the zinc phthalocyanine complex is enc~r-s~ ted in
pharmaceutically effective amounts in nanoparticles formed from selected pharmaceutically
acceptable polymers. Accordingly, the following invention relates to a pharmaceutical
composition which is suitable for the solubilization of the zinc phthalocyanine complex. The
composition is characterized by the following components:
a) the zinc phthalocyanine complex;
b) a pharmaceutically acceptable polymer which is suitable for the formation of
nanoparticles and, optionally;
c) further pharmaceutically acceptable additives which are suitable for incorporation in a
dosage form for the intended mode of administration.
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The pharmaceutical composition according to the present invention has the benefit of
providing enhanced solubilization of the zinc phthalocyanine complex and specific release
in selected target regions of malignant tissues such as neoplasms. This renders the
pharmaceutical composition particularly useful for use in photodynamic therapy.
The general terms used throughout the specification of this invention are preferably defined
as follows:
The term "pharmaceutical composition" means a mixture containing the zinc phthalocyanine
complex that can be administered to a host in a therapeutic method of treating the disease
or condition indicated. The composition is especially suitable for parenteral administration,
especially i.v., but also for topical administration.
The term "solubilization" defines the homogeneous dispersion of the zinc phthalocyanine
complex of extremely low water solubility in an aqueous phase containing nanoparticles
with the aid of a pharmaceutically acceptable solubilizer which is suitable for the preparation
of nanoparticles.
Nanoparticles are solid spheroid particles ranging in size from about 10 to 1000 nm. When
dispersed in an aqueous phase, they have colloidal properties. The term nanoparticles is a
generic term that comprises nanospheres and nanocapsules. Nanospheres have a
polymeric matrix type structure, whereas nanocapsules have a shell formed of polymers
surrounding a liquid core. Nanoparticles encapsulate the zinc phthalocyanine complex of
extremely low water solubility.
The term "encapsulation" indicates the presence of the active agent zinc phthalocyanine in
nanoparticles. In nanospheres, the active agent may be adsorbed at their surface or
entrapped, e. 9. as microcrystals, in the polymeric matrix, or may be dissolved therein. In
nanocapsules the active agent may be dispersed in the liquid present in the core, but may
also be adsorbed at the surface, entrapped or dissolved in the polymeric matrix.
Component a) - active agent: the zinc phthalocyanine component is listed as "ciaftalan zinc"
in List 74 of proposed INNs (International Nonproprietary Names) published in the Vol.9,
No.4 (199~) issue of the WHO Drug Information.
Component b) - polymers: a pharmaceutically acceptable polymer which is suitable for the
formation of nanoparticles is, for example, a pharmaceutically acceptable homopolymer or
copolymer from monomers selected from the group consisting of L-lactide N or S, D-lactide
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S, D,L-lactide S, glycolide S or trimethylene carbonate. Those polymers are marketed under
the trade-mark MEDISORB (Registered Trade-Mark of Medisorb Technologies Inc.),
PURASORB (Registered Trade-Mark of PURAC Biochem.) or RESOMER (Registered
Trademark of Boehringer Ingelheim, Germany).
Suitable products are MEDISORB polymers of the L or DL series, e.g. 100 L or DL, or 8515,
7525, 6535, or 5050 DL, or RESOMER homopolymers of the L series, formed from L-
lactide, e.g. L 104, 206 - 210, or 214, R series formed from racemic D,L-lactide, e.g. R 104,
202, 203, or 206 - 208 or G series formed from glycolide, e.g. G 205, or copolymers of the
LR series formed from L-lactide with D,L-lactide, e.g. LR 708, or 909 or DL-lactide with
glycolide, e.g. RG 502 - 505, 752, 755, 756, or 858.
Whenever other modes of administration, such as topical administration, are intended, other
polymers suitable for the formation of nanoparticles may be selected. An alternative
polymer is a pharmaceutically acceptable copolymer formed from monomers selected from
the group consisting of methacrylic acid, methacrylic acid esters, acrylic acid and acrylic
acid esters. These polymers are commercially available from Rohm Pharma GmbH,
Weiterstadt, Germany, and are marketed under the trademark EUDRAGIT (Registered
Trademark of Rohm Pharma GmbH).
An especially preferred polymer of the EUDRAGIT series is the 1:1- to 1 :2-copolymer which
is formed from monomers selected from the group consisting of methacrylic acid and
methacrylic acid lower alkyl esters, such as the 1:1- to 1 :2-copolymer of methacrylic acid
and methyl methacrylate. The 1 :1-copolymers are marketed in the EUDRAGIT L series,
such as L 12.5, 100, or L 30 D. The corresponding 1 :2-copolymers are marketed in the
EUDRAGIT S series, such as S 12.5 or S 100.
Another preferred polymer of the EUDRAGIT series is the 1:1- copolymer of methacrylic
acid and acrylic acid ethyl ester. This polymer is marketed under the product name
EUDRAGIT L 100-55.
Another polymer which is suitable for the formation of nanoparticles is polyvinyl acetate
phthalate (PVAP) or a pharmaceutically acceptable cellulose derivative selected from the
group consisting of hydroxypropyl methyl cellulose acetate succinate (HPMCAS),
hydroxypropyl methyl cellulose phthalate (HPMCP), cellulose acetate phthalate (CAP), and
cellulose acetate trimellitate (CAT).
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HPMCP is marketed by Eastman Kodak Corp.. HPMCP 50 (USP/NF type 220824) and
HPMCP 55 (USP/NF type 200731 ) are especially preferred.
CAP is marketed under the trademark AQUATERIC ( Registered Trademark of FMC Corp.)
or is commercially available from Eastman (composition: phthalyl 35 %, acetyl 24 %,
moisture 1 %, free acid 0.5 % (as phthalic acid)).
CAT is commercially available from Eastman (composition: trimellityl 29 %, acetyl 22 %,
moisture 1 %, free acid 0.5 % (as phthalic acid)).
Component c) - additives: Pharmaceutically acceptable additives are determined by the
dosage form for the intended mode of administration. A preferred mode of administration is
parenteral, especially i.v., but also topical, e.g. ocular.
Parenteral dosage forms are particularly useful for intravenous, but also for intramuscular
administration. If intravenous administration is intended, water is added that has been
sterilized and freed from pyrogens, according to the prescriptions of national pharma-
copoeias, such as The U.S. Pharmacopoeia (USP) or Deutsches Arzneibuch (DAB). The
addition of water-soluble additives, which are suitable for the adjustment of isotonic
conditions, is particularly preferred, typically sodium chloride, sorbitan, mannitol, glucose,
lactose or fructose. If intramuscular administration is intended, oily carrier liquids, such as
sesame oil or olive oil, but also lecithin, may be added.
Additives for topical formulations are listed in standard textbooks, e.g. Remington's
Pharmaceutical Sciences or Hagers Handbuch der Pharmazeutischen Praxis. Topical
formulations are in particular creams, ointments, gels, pastes or topically administered
aerosols and also suspensions of nanoparticles or ophthalmic compositions.
Suitable additives for topical and especially ophthalmic compositions are in particular inert
carriers, solubilizers, tonicity-increasing agents, buffer substances, preservatives,
thickeners, and other adjuncts. Such additives are e.g. ethanol, vegetable oil, mineral oil
containing hydroxyethyl cellulose, ethyl oleate, carboxymethyl cellulose, polyvinyl-
pyrrolidone, and other non-toxic water-soluble polymers intended for ophthalmic use, e.g.
cellulose ethers such as methyl cellulose, alkali metal salts of carboxymethyl cellulose or
hydroxymethyl, hydroxyethyl, or hydroxypropyl cellulose, acrylates or methacrylates such
assalts of polyacrylic acid or ethyl acrylate, polyacrylamides, natural products such as
gelatin, alginates, pectins, tragacanth, karaya gum, xanthan gum, carrageenan, agar or
acacia, starch derivatives such as starch acetate and hydroxypropyl starch, and also other
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synthetic additives such as polyvinyl alcohol, polyvinylpyrrolidone. polyvinyl methyl ether,
polyethylene oxide, preferably crosslinked polyacryiic acid such as neutral Carbopol~ or
mixtures of these polymers.
Examples of buffer substances are acetate, ascorbate, borate, bicarbonate/ carbonate,
citrate, gluconate, lactate, phosphate, propionate, and so-called tris buffers. The amount of
buffer substance is added to maintain a physiologically acceptable pH-range.
Tonicity-enhancing agents are, for example, ionic compounds, such as alkali metal or
alkaline earth metal halides, e.g. CaCI2, Kbr, KCI, LiCI, Nal, NaBr, or NaCI, or boric acid.
Non-ionic tonicity-enhancing agents are, for example, urea, glycerol, sorbitol, mannitol,
propylene glycol, or dextrose. Sufficient tonicity-enhancing agent is added that the
ophthalmic composition has an osmolality in a preferred range of about 50 to 400 mOsmol.
Examples of preservatives are quaternary ammonium salts such as cel~ -ide,
benzalkonium chloride, alkylmercury salts of thiosalicylic acid such as thiomersal,
phenylmercury nitrate, acetate, or borate, parabens such as methylparaben or
propylparaben, alcohol, e.g. chlorobutanol, benzyl alcohol, or phenylethanol, guanidine
derivatives, e.g. chlorhexidine, or po!yhexamethylenebiguanide, or sorbic acid. If desired,
the amount of preservative which is necessary to ensure sterility is added to the ophthalmic
composition.
The present invention in particular relates to a pharmaceutical composition suitable for
intravenous administration and containing
a) the zinc phthalocyanine complex;
b) a pharmaceutically acceptable homopolymer or copolymer from monomers selected from
the group consisting of L-lactide N or S, D-lactide S, D,L-lactide S, or glycolide S;
c) further pharmaceutically acceptable additives which are suitable for incorporation in a
dosage form for intravenous administration.
The present invention also relates to a process for the preparation of said pharmaceutical
composition which is characterized in that an aqueous dispersion of nanoparticles is formed
containing
a) the zinc phthalocyanine complex;
b) a pharmaceutically acceptable polymer which is suitable for the formation of
nanoparticles;
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and the dispersion is processed further with the optional addition of pharmaceutically
acceptable additives c), which are suitable for incorporation into a dosage form for the
intended mode of administration.
Various methods of performing this process are known. They are compiled in Eric Allémann
ef al., Eur. J. Pharm. Biopharm. 39(5), 173 - 191 (1993). The methods for the preparation of
nanospheres mentioned in this reference are particulary preferred.
An especially preferred method comprises the preparation of an aqueous gel containing a
hydrophilic polymer with the optional addition of a water-soluble salt. This gel is mixed with
a solution of an organic solvent containing the active agent and the polymer which is
suitable for the formation of nanoparticles. Phase separation is then observed, and, after
addition of water, the nanoparticles formed are homogeneously dispersed in the aqueous
phase. The aqueous phase is then processed further to the pharmaceutical dosage form
intended, e.g. by applying conventional purification and separation methods.
The preparation of the aqueous gel containing the hydrophilic polymer is disclosed in
E. Allémann, loc. cit., and the additional references cited therein. The gel is formed by
adding water to the hydrophilic polymer. Suitable hydrophilic polymers are polyvinyl alcohols
such as the ones marketed under the trademark MOWIOL (Registered Trademark of
Hoechst AG, Germany). Preferred are polyvinyl alcohols having a degree of hydrolysis of
more than 70 % (partially hydrolized grades), especially more than 87 %, e.g. MOWIOL of
the 88 and 92 series, e.g. 4-88, 5-88, 8-88,18-88, 23-88, 26-88, and 40-88. To facilitate the
separation of the phase from the organic phase, which is subsequently added, it is
preferred to add to the gel phase a physiologically acceptable water-soluble salt, e.g.
magnesium chloride, or magnesium acetate.
The gel phase is added, with stirring, to a solution of the organic solvent, e.g. acetone or
benzyl alcohol, which contains the active agent, e.g. the zinc phthalocyanine complex and
the pharmaceutically acceptable polymer, which is suitable for the formation of
nanoparticles defined above.
Pure water is then added to allow diffusion of the organic solvent into the aqueous phase,
and the nanoparticles are formed and homogeneously dispersed therein. The aqueous
phase may be processed further by conventional purification and separation methods
resulting in the preparation of the dosage form desired.
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The dispersion so obtained may be defined as an aqueous suspension of nanoparticles
containing zinc phthtalocyanine. According to the preferred method of phase separation of
the aqueous gel from the organic solvent, a homogeneous dispersion of nanospheres is
obtained. Nanospheres are clearly distinguishable by physical methods, such as photon
correlation spectroscopy (PCS), e. 9. with a COULTER NANO-SIZER, by LASER light
scattering methods or electron microscopy, from other microparticles, such as liquid
crystals, micells, reversed micells, liposomes, microspheres or microcapsules. For a
statistical average of more than 80 %, preferably more than 90 %, a mean average particle
size between 60 and 300 nm has been determined. The size of the nanoparticles obtained
depends on the established and known methods chosen for their preparation.
The homogeneous aqueous dispersion containing nanospheres is then processed further to
a conventional pharmaceutical dosage form by applying standard purification methods, e.g.
the ones known in the art for purifying nanoparticles, e.g. ultracentrifugation or cross-flow
filtration. The dispersion can also be Iyophilized in conventional manner, and the Iyophilisate
is then reconstituted to the pharmaceutical dosage form desired. Even after reconstituting
the Iyophilisate, a homogeneous nanodispersion is formed again. When preparing
Iyophilisates, the addition of specific amounts of water-soluble additives is recommended.
The invention also relates to the use of the pharmaceutical composition in a method for
treating the human or animal body by photodynamic therapy. The composition is
administered, preferably intravenously, in a range of 0.01 - 1,00 mg/kg, preferably 0.03 - 1.0
mg/kg active substance. In photodynamic therapy, the patient is exposed 20 min.- 24 h after
drug administration to a high energy light source of about 671 nm wavelength.
A parenteral dosage form is prepared by applying known methods such as the ones
mentioned in Hagers I /andbuch der Pharmazeutischen Praxis or Remington's
Pharmaceutical Sciences. In particular the additives customarily used for the preparation of
parenteral dosage forms may be added if necessary. Their choice depends on the type of
dosage form requested, e.g. intravenous or intramuscular dosage forms.
The homogeneous dispersion, optionally after concentration to standardized volumes, or
the Iyophilisate is added to suitable containers for unitary dosage forms such as vials.
The following Example illustrates the invention as disclosed in the instant specification
without limiting the scope thereof; temperatures are given in degrees Celsius; all percent-
ages mentioned are weight percentages (w/w):
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_ g _
Example: 40 9 of an aqueous gel containing 35 % magnesium acetate and 11 % polyvinyl
alcohol (MOWIOL 4-88, Hoechst) is added with stirring (5000 rpm), to an organic solution of
10 mg zinc phthalocyanine and 1.0 g polylactic acid (MEDISORB 100 DL) in N-methyl-2-
pyrrolidone (NMP) and acetone (1:9), resulting in the formation of an oil-in-water emulsion.
To this emulsion pure water (40 g) is added to allow the diffusion of the organic solvents
into the aqueous phase resulting in the formation of mono-dispersed polymeric nano-
particles.
The nanoparticulate dispersion is then purified by cross-flow filtration using a SARTOCON
Mini Device (Sartorius, Gottingen, Gemany) mounted with a polyolefin cartridge filter having
a 100 nm pore size. The filtration procedure is stopped after collecting 10 1 of filtrate. The
aqueous dispersion is finally frozen for 10 minutes at -55~ and freeze-dried for 24 h at
0.05 mbar.
The Iyophilisate is reconstituted in water with gentle agitation. The average particle size
measured with a COULTER NANO-SIZER before purification with cross-flow filtration is
264 nm (polydispersity index: 2) and after reconstitution of the Iyophilisate is 268 nm
(polydispersity index: 3). The freeze-dried nanoparticles contain 0,98 % of the active agent.
