Note: Descriptions are shown in the official language in which they were submitted.
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OCTREOTIDE-PAMOATE AND ITS USE IN SUSTAINED RELEASE FORMULATIONS OF
WATER SOLUBLE PEPTIDES
BACKGROUND OF THE INVENTION
This application has been divided out of Canadian Patent Application
Serial No. 2,316,052 filed July 5, 1990 which was itself divided out
of Canadian Patent Application Serial No. 2,020,477 filed July 5,
1990.
This invention relates to the compound octreotide pamoate.
The parent invention relates to sustained release (depot)
formulations of drugs in particular water soluble peptides, e.g.
somatostatin or somatostatin analogs, such as octreotide, in a
biodegradable and biocompatible polymeric carrier, e.g. a matrix or
a coating, e.g. in the form of an implant or preferably a
microparticle (also known as a microcapsule or a microsphere).
The invention also relates to such formulations, showing
satisfactory peptide release profiles over a particular period of
time.
Peptide drugs often show after oral or parenteral administration a
poor bioavailability in the blood, e.g. due to their short
biological half-lives caused by their metabolic instability. If
orally or nasally administered they additionally often show a poor
resorption through the mucuous membranes. A therapeutically
relevant blood level over an extended period of time is difficult to
achieve.
The parenteral administration of peptide drugs as a depot
formulation in a biodegradable polymer, e.g. as microparticles or
implants, has been proposed enabling their sustained release
i
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after a residence time in the polymer which protects the peptide
against enzymatic and hydrolytic influences of the biological
media.
Although some pa~enteral depot formulations of peptide drugs in
a polymer in the form of microparticles or an implant, are
known, satisfactory peptide release profiles are in practice
only obtained in very few cases. Special measures must be taken
to achieve a continuous peptide release for a therapeutically
active drug serum level and if desired avoiding too high drug
serum concentrations, which cause undesired pharmacological side
reactions.
The peptide drug release pattern is dependant on numerous
factors, e.g. the type of the peptide, and e.g. whether it is
present in its free or in another form, e.g. salt form, which
may influence its water solubility. Another important factor is
the choice of polymer, from the extended list of possibilities
which have been described in the literature.
Each polymer type has its characteristic biological degradation
rate. Free carboxyl groups may be~formed which contribute to the
pH value in the polymer and thus additionally influence the
water solubility of the peptide and thus its release pattern.
Other factors, which may influence the release pattern of the
depot formulation, are the drug loading of its polymeric
carrier, the manner of its distribution in the polymer, the
particle size and, in case of an implant, additionally its
shape. Further is the site of the formulation in the body of
influence.
Until now no somatostatin composition in sustained release form
for parenteral administration has reached the market, perhaps
because no composition exhibiting a satisfactory serum level
profile could be obtained.
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DESCRIPTION OP THE PRIOR ART
Polymer formulations with drugs which are designed to give
prolonged or delayed release of the drug are known in the art.
US Patent No. 3,773,919 discloses controlled drug release
formulations in which the drug, e.g. a water soluble peptide
drug is dispersed in a biodegradable and biocompatible linear
polylactide or polylactide-co- glycolide polymer. However, no
drug release patterns have been described and there is no
reference to a somatostatin. US Patent 4,293,539 describes
anti-bacterial formulations in microparticle form.
US Patent No. 4,675,189 describes sustained release formulations
of the LHRH analog decapeptide nafareline and analogous LHRH
congeners in polylactide-co-glycolide polymers. No release'
pattern has been described.
T.Chang,J.Bioeng., Vol.l, pp 25-32, 1976 described prolonged
release of biologicals, enzymes and vaccines from
microparticles.
Polymers/copolymers of lactic acid and lactide/glycolide
copolymers and related compositions for use in surgical
applications and for sustained release and biodegradation have
been reported in US Pat.Nos 3,991,776; 4,076,798 and 4,118,470.
European patent application 0 203 031 describes a series of
somatostatin octapeptide analogs, e.g. Compound RC-160 having
the formula:-
D-Phe-Cys-Tyr-D-Trp-Lys-Val-Cys-Trp-NH2
,having a bridge between the -Cys- moieties,
in columns 15-16.
The possibility of the somatostatins being microencapsulated
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with polylactide-co-glycolide polymer has been mentioned in
claim 18, but no instructions have been disclosed how to obtain
a continuous therapeutically active serum level.
US Patent No. 4,011,312 describes that a continuous release of
an antimicrobial drug, e.g. the water soluble polymyxin B from a
polylactide-co-glycolide matrix of a low molecular weight (below
2000) and a relatively high glycolide content in the form of an
implant, can be obtained, when the implant is inserted into the
teat canal of a cow. The drug is released within a short period
of time, due to the high glycolide content and the low molecular
weight of the polymer, which both stimulate a quick polymer
biodegradation and thus a corresponding quick release of the
drug. A relatively high drug loading content additionally
contributes to a quick drug release. No somatostatins and no
drug release patterns have been described.
European Patent No. 58481 discloses that a continuous release of
a water soluble peptide from a polylactide polymer implant is
stimulated by lowering the molecular weight of at least a part
of the polymer molecules, by introducing glycolide units into
the polymer molecule, by increasing the block polymer character
of the polymer when polylactide-co-glycolide molecules are used,
by increasing the drug loading content of the polymer matrix and
by enlarging the surface of the implant.
Although somatostatins are mentioned as water soluble peptides,
no somatostatin release profiles have been described and no
indication has been given how to combine all these parameters to
obtain e.g. a continuous somatostatin serum level over at least
one week, e.g. one month.
European Patent No. 92918 describes that a continuous release of
peptides, preferably of hydrophilic peptides, over an extended
period of time can be obtained, when the peptide is incorporated
in a conventional hydrophobic polymer matrix, e.g. of a
polylactide, which is made more accessible for water by
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introducing in its molecule a hydrophilic unit, e.g. of
polyethyleneglycol, polyvinylalcohol, dextran, polymethacryl-
amide. The hydrophilic contribution to the amphipathic polymer
is given all the ethylene oxide groups in case of a polyethylene
glycol unit, by the free hydroxyl groups in the case of a
polyvinylalcohol unit or of a dextran unit, and by the amide
groups in the case of a polymethyacrylamide unit. Due to the
presence of the hydrophilic unit in the polymer molecules the
implant will obtain hydrogel properties after the absorption of
water. Somatostatin is mentioned as an hydrophilic peptide, but
no release profile has been described and no indication has been
given, what type of polymer is preferred for this peptide, and
what molecular weight and how many hydrophilic groups it should
have.
The US Patent GB 2,145,422 B describes that a sustained release
of drugs of several types, e.g. of vitamins, enzymes,
antibiotics, antigens, can be obtained over an extended period
of time, when the drug is incorporated in an implant, e.g. of
microparticle size, made of a polymer of a polyol, e.g. glucose
or mannitol, having one or more, preferably at least 3,
polylactide ester groups. The polylactide ester groups
preferably contain e.g. glycolide units.
No peptides, e.g. somatostatins, are mentioned as drugs and no
serum drug levels have been disclosed.
SUH!lARY OF THB INVENTION
This invention relates to sustained release formulations, e.g.
microparticle formulations, of a drug, especially of a
hormonally active water-soluble somatostatin or a somatostatin
analog such as octreotide, providing a satisfactory drug plasma
level and, e.g. in a biodegradable, biocompatible polymer, e.g.
in a encapsulating polymer matrix. The polymer matrix may be a
synthetic or natural polymer.
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The microparticles of this invention may be prepared by any
conventional technique, e.g. an organic phase separation
technique, a spray drying technique or a triple emulsion
technique, wherein the polymer is precipitated together with the
drug, followed by hardening of the resulting product, when the
phase separation or triple emulsion technique are used.
If desired the sustained release formulations may be in the form
of an implant.
We have found an especially useful modification of the phase
separation technique for preparing microparticles of any drug.
Accordingly the present invention also provides a process for
the production of a microparticle comprising a drug in a
biodegradable, biocompatible carrier which comprises the steps
of:-
a) dissolving the polymeric carrier material in a solvent, in which the drug
compound is not soluble,
b) adding and dispersing a solution of the drug compound in a solvent, e.g. an
alcohol, which is anon-solvent fox the polymer, in the solution of step a),
c) adding a phase inducing agent to the dispersion of step
b), to induce microparticle formation,
d) adding an oil-in-water emulsion to the mixture of step c) to
harden the microparticle, and
e) recovering the microparticle.
We have also found an especially useful modification of the
triple emulsion technique for preparing microparticles of any
drug.
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Accordingly the present invention provides:
A process for producing microparticles which comprises
(i) intensively mixing a water-in-oil emulsion formed from an
aqueous medium and a water-immiscible organic solvent containing
in one phase the drug and in the other a biodegradable,
biocompatible polymer, with an excess of an aqueous medium
containing an emulsifying substance or a protective colloid to
form a water-in-oil-in-water emulsion, without adding any drug
retaining substance to the water-in-oil emulsion or applying any
intermediate viscosity increasing step,
ii) desorbing the organic solvent therefrom,
iii) isolating and drying the resultant microparticles.
The present invention additionally provides the microparticles
obtained according these processes.
The present invention also provides:-
a) a sustained release formulation comprising a peptide drug
compound in a 4°/6o to 6°/ao polylactide-co-glycolide ester
of a polyol, the polyol unit chosen from the group of a
(C3-6)carbon chain containing alcohol having 3 to 6 hydroxyl
groups and a mono- or di-saccharide, and the esterified
polyol having at least 3 polylactide-co-glycolide chains.
b) A SUStained release formulation comprising a peptide drug
compound chosen from the group of a calcitonin, lypressin or
a somatostatin in a '°/6o to 6°/ao polylactide-co-glycolide
polymer having linear chains of a molecular weight MW between
25,000 and 100,000, a polydispersity MW/Mn between 1.2 and 2
in a concentration of from 0.2, preferably 2 to 10~ of weight
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of the peptide drug compound therein.
c) A sustained release formulation comprising octreotide or a
salt or a derivative thereof in a biodegradable,
biocompatible polymeric carrier.
We have found that a novel salt of octreotide is the pamoate
which is very stable in such formulations.
The present invention accordingly provides (i) octreotide
pamoate and (ii) a process for the production of octreotide
pamoate which comprises reacting octreotide with embonic acid
(or a reactive derivative thereof).
Additionally the present invention provides:-
A method of administering a peptide to a subject which comprises
administering parenterally to a subject in need of such
treatment a depot formulation as defined above, especially for
the treatment of acromegaly or breast cancer.
DESCRIPTION OP THB PREFSRRBD
The drugs of use in the processes of the invention are
preferably water soluble drugs, e.g. peptides.
The peptides of use in the processes and formulations of this
invention may be a calcitonin, such as salmon calcitonin,
lypressin, and the naturally occuring somatostatin and synthetic
analogs thereof.
The naturally occuring somatostatin is one of the preferred
compounds and is a tetradecapeptide having the structure:-
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Ala-Gly-Cys-Lys-Asn-Phe-Phe-Trp
Cys-Ser-Thr-Phe-Thr-Lys
This hormone is produced by the hypothalmus gland as well as
other organs, e.g. the GI tract, and mediates, together with
GRF, q.v. the neuroregulation of pituitary growth hormone
release. In addition to inhibition of GH release by the
pituitary, somatostatin is a potent inhibitor of a number of
systems, including central and peripheral neural,
gastrointestinal and vascular smooth muscle. It also inhibits
the release of insulin and glucagon.
The term "somatostatin" includes its analogues or derivatives
thereof. By derivatives and analogues is understood
straight-chain, bridged or cyclic polypeptides wherein one or
more amino acid units have been omitted and/or replaced by one
or more other amino radicals) of and/or wherein one or more
functional groups have been replaced by one or more other
functional groups and/or one or more groups have been replaced
by one or several other isosteric groups. In general, the term
covers all modified derivatives of a biologically active peptide
which exhibit a qualitatively similar effect to that of the
unmodified somatostatin peptide.
Agonist analogs of somatostatin are thus useful in replacing
natural somatostatin in its effect on regulation of physiologic
functions.
Preferred known somatostatins are:-
a) (D)Phe-Cys-Phe-(D)Trp-Lys-Thr-Cys-Thr-of
(Generic name Octreotide)
b) (D)Phe-Cys-Tyr-(D)Trp-Lys-Val-Cys-ThrNH2
I
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*
c) (D)Phe-Cys-Tyr-(D)Trp-Lys-Val-Cys-TrpNHz
d) (D)Trp-Cys-Phe-(D)Trp-Lys-Thr-Cys-ThrNHz
e) (D)Phe-Cys-Phe-(D)Trp-Lys-Thr-Cys-ThrNH2
f) 3-(2-(Naphthyl)-(D)Ala-Cys-Tyr-(D)Trp-Lys-Val-Cys-ThrNHZ
g) (D)Phe-Cys-Tyr-(D)Trp-Lys-Val-Cys-~-Nal-NHz
h) 3-(2-naphthyl)-Ala-Cys-Tyr-(D)Trp-Lys-Val-Cys-~-Nal-NH2
i) (D)Phe-Cys-~-Nal-(D)Trp-Lys-Val-Cys-Thr-NHz
wherein in each of compounds a) to i) there is a bridge between
the amino acids marked with a * as indicated in the next
formula.
Other preferred somatostatins are:-
*______________________________*
H-Cys-Phe-Phe-(D)Trp-Lys-Thr-Phe-Cys-OH
(See Vale et al., Metabolism, 27, Supp.l, 139 (1978)).
Asn-Phe-Phe-(D)Trp-Lys-Thr-Phe-Gaba
(See European Pat. Publication No. 1295, published April 4, 1979).
MeAla-Tyr-(D)Trp-Lys-Val-Phe
(See Verber et al., Life Sciences, 34, 1371-1378 (1984)
and European Pat.Appln.No. 82106205.6 (published as No.
70 021)) also known as cyclo
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(N-Me-Ala-Tyr-D-Trp-Lys-Val-Phe).
NMePhe-His-(D)Trp-Lys-Val-Ala
(See R.F.Nutt et al.,. Klin.Wochenschr. (1986) 64
(SuppI.VII)
H-Cys-His-His-Phe-Phe-(D)Trp-Lys-Thr-Phe-Thr-Ser-Cys-OH
(see EP-A-200,188).
X-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-NHz
and
X-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-of
wherein X is a cationic anchor
especially
Ac-hArg(EtZ)-Gly-Cys-Phe-D-Trp-Lys-Thr-Cys-NHZ
(See EP 0363589A2)
wherein in the above mentioned amino acids there is a bridge
between the amino acids marked with a *.
The term derivative includes also the corresponding derivatives
bearing a sugar residue.
When somatostatins bear a sugar residue, this is preferably
coupled to a N-terminal amino group and/or to at least one amino
group present in a peptide side chain, more preferably to a
N-terminal amino group. Such compounds and their preparation are
disclosed, e.g. in WO 88/02756.
The term octreotide derivatives includes those including the
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moiety
-D-Phe-Cys-Phe-DTrp-Lys-Thr-Cys- having a bridge between the Cys
residues.
Particularly preferred derivatives are N°~-[a-glucosyl-
(1-4-deoxyfructosyl]-DPhe-Cys-Phe-DTrp-Lys-Thr-Cys-Thr-of and
N°~-[~-deoxyfructosyl-DPhe-Cys-Phe-DTrp-Lys-Thr-Cys-Thr-ol, each
having a bridge between the -Cys- moieties, preferably in
acetate salt form and described in Examples 2 and 1 respectively
of the above mentioned application.
The somatostatins may exist e.g. in free form, salt form or in
the form of complexes thereof. Acid addition salts may be formed
with e.g. organic acids, polymeric acids and inorganic acids.
Acid addition salts include e.g. the hydrochloride and acetates.
Complexes are e.g. formed from somatostatins on addition of
inorganic substances, e.g. inorganic salts or hydroxides such as
Ca- and Zn-salts and/or an addition of polymeric organic
substances.
The acetate salt is a preferred salt for such formulations,
especially for microparticles leading to a reduced initial drug
burst. The present invention also provides the pamoate salt,
which is useful, particularly for implants and the process for
its preparation.
The pamoate may be obtained in conventional manner, e.g. by
reacting embonic acid (pamoic acid) with octreotide e.g. in free
base form. The reaction may be effected in a polar solvent, e.g.
at room temperature.
The somatostatins are indicated for use in the treatment of
disorders wherein long term application of the drug is
envisaged, e.g. disorders with an aetiology comprising or
associated with excess GH-secretion, e.g. in the treatment of
acromegaly, for use in the treatment of gastrointestinal
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disorders, for example, in the treatment or prophylaxis of
peptic ulcers, enterocutaneous and pancreaticocutaneous fistula,
irritable bowel syndrome, dumping syndrome, watery diarrhea
syndrome, acute pancreatitis and gastroenteropathic endocrine
tumors (e. g. vipomas, GRFomas, glucagonomas, insulinomas,
gastrinomas and carcinoid tumors) as well as gastro-intestinal
bleeding, breast cancer and complications associated with
diabetes.
The polymeric carrier may be prepared from biocompatible and
biodegradable polymers, such as linear polyesters, branched
polyesters which are linear chains radiating from a polyol
moiety, e.g, glucose; Other esters are those of polylactic acid,
polyglycolic acid, polyhydroxybutyric acid, polycaprolactone,
polyalkylene oxalate, polyalkylene glycol esters of acids of the
Kreb's cycle, e.g. citric acid cycle and the like and copolymers
thereof.
The preferred polymers of this invention are the linear
polyesters, and the branched chain polyesters.
The linear polyesters may be prepared from the alphahydroxy
carboxylic acids, e.g. lactic acid and glycolic acid, by the
condensation of the lactone dimers, see for example US Pat. No.
3,773,919.
Linear polylactide-co-glycolides which are preferably used
according to the invention conveniently have a molecular weight
between 25,000 and 100,000 and a polydispersibility Mw/Mn e.g.
between 1.2 and 2.
The branched polyesters preferably used according to the
invention may be prepared using polyhydroxy compounds e.g.
polyol e.g, glucose or mannitol as the initator. These esters of
a polyol are known and described in UK Patent GB 2,145,422 B.
The polyol contains at least 3 hydroxy groups and has a
molecular weight of up to 20,000, with at least 1, preferably at
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least 2, e.g. as a mean 3 of the hydroxy groups of the polyol
being in the form of ester groups, which contain poly-lactide or
co-poly-lactide chains. Typically 0.2Y glucose is used to
initiate polymerisation. The structure of the branched
polyesters is star shaped. The preferred polyester chains in the
linear and star polymer compounds preferably used according to
the invention are copolymers of the alpha carboxylic acid
moieties, lactic acid and glycolic acid, or of the lactone
dimers. The molar ratios of lactide: glycolide is from about
75:25 to 25:75, e.g. 60:40 to 40:60, with from 55:45 to 45:55,
e.g. 55:45 to 50:50 the most preferred.
The star polymers may be prepared by reacting a polyol with a
lactide and preferably also a glycolide at an elevated
temperature in the presence of a catalyst, which makes a ring
opening polymerization feasible.
We have found that an advantage of the star polymer type in the
formulations of the present invention is, that its molecular
weight can be relatively high, giving physical stability, e.g. a
certain hardness, to implants and to microparticles, which
avoids their sticking together, although relatively short
polylactide chains are present, leading to a controllable
biodegradation rate of the polymer ranging from several weeks to
one or two months and to a corresponding sustained release of
the peptide, which make a depot formulation made therefrom
suitable for e.g. a one month's release.
The star polymers preferably have a main molecular weight MW in
the range of from about 10,000 to 200,000, preferably 25,000 to
100,000, especially 35,000 to 60,000 and a polydispersity e.g.
of from 1.7 to 3.0, e.g. 2.0 to 2.5. The intrinsic viscosities
of star polymers of Mw 35.000 and MW 60.000 are 0.36 resp. 0.51
dl/g in chloroform. A star polymer having a Mw 52.000 has a
viscosity of 0.475 dl/g in chloroform.
The terms microsphere, microcapsule and microparticle are
considered to be interchangeable with respect to the invention,
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and denote the encapsulation of the peptides by the polymer,
preferably with the peptide distributed throughout the polymer,
which is then a matrix for the peptide. In that case preferably
the terms microsphere or more generally microparticle are used.
Using the phase separation technique of the present invention
the formulations of this invention may be prepared for example
by dissolving the polymeric carrier material in a solvent, which
is a nonsolvent for the peptide, following by the addition and
dispersing a solution of the peptide in the polymer-solvent
composition. A phase iriducer e.g. a silicone fluid is then added
to induce encapsulation of the peptide by the polymer.
The drug burst effect can be significantly reduced by
insitu precipation of ultra fine drug particules, by adding
a drug solution to the polymer solution prior to phase
separation. The prior art method involves adding dry particles
directly to the polymer solution.
The therapeutic duration of peptide release can be increased
by hardening/washing the microparticles with an emulsion of
buffer/heptane. The prior art method involves a hardening step
followed by either no subsequent washing, or a
separate aqueous washing step.
An emulsion of the type oil-in-water (_ °/W) may be used to wash
and harden the microspheres and remove non-encapsulated peptide.
The wash aids in the removal of non-encapsulated peptide from
the surface of the microspheres. The removal of excess peptide
from the microspheres diminishes the initial drug burst, which
is characteristic of many conventional encapsulation
formulations. Thus, a more consistent drug delivery over a
period of time is possible with the present microsphere
formulations.
The emulsion also aids in the removal of residual polymer
solvent and the silicone fluid. The emulsion may be added to the
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polymer peptide mixture, or the mixture added to the emulsion.
It is preferred that the polymer peptide mixture be added to the
emulsion.
The olw emulsion may be prepared using a emulsifier such as
sorbitan mono-oleate (Span~ 80 ICI Corp.) and tic like, to form a
stable emulsion. The emulsion may be buffered with a buffer
which is non-detrimental to the peptide and the polymer matrix
material. The buffer may be from pH 2 to 8 with a pH 4
preferred. The buffer may be prepared from acidic buffers such
as phosphate buffer, acetate buffer and the like. Water alone
may be substituted for the buffer.
$eptane, hexane and the like may be used as the organic phase of
the buffer.
The emulsion may contain dispersing agents such as silicone oil.
A preferred-emulsion may comprise heptane, pH 4 phosphate
buffer, silicone oil and sorbitan mono-oleate. When an initial
drug release may be desirable, a single non-solvent hardening
step may be substituted for the emulsion hardening. Heptane,
hexane and the like, may be used as the solvent.
Other alternatives to the o/w emulsion may be used for hardening
the microcapsules, such as:-
Solvent plus emulsifier for hardening the microcapsules without
washing; and solvent plus emulsifier for hardening followed by a
separate washing step.
The o/w emulsion may be used without the dispersing agent. The
dispersing agent, however, avoids aggregation of the dry
particles of microcapsules due to static electricity, and helps
to reduce the level of residual solvent.
Examples of the solvent for the polymer matrix material include
methylene chloride, chloroform, benzene, ethyl acetate, and the
like. The peptide is preferably dissolved in an alcoholic
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solvent, e.g. methanol, which is miscible with the polymer
solvent.
The phase inducers (coacervation agents) are solvents which are
miscible with the polymer-drug mixture, and cause the embryonic
microcapsules to form prior to hardening; silicone oils are the
preferred phase inducers.
The o/w emulsion may be prepared in a conventional manner using
heptane, hexane and the like for the organic phase.
The microparticles of this invention may also be prepared by the
generally known spray-drying procedure. According to this method
the somatostatin, or a solution of the peptide in an organic
solvent, e.g, methanol, in water or in a buffer, e.g of pH 3-8
and a solution of the polymer in an organic solvent, not
miscible with the former one, e.g. methylene chloride, are
thoroughly mixed.
The formed solution, suspension or emulsion is then sprayed in a
stream of air, preferably of warm air. The generated
microparticles are collected, e.g. by a cyclon and if desired
washed, e.g. in a buffer solution of e.g. pH 3.0 to 8.0
preferably of pH 4.0 or distilled water and dried in a vacuum
e.g. at a temperature of 20 to 40°C. The washing step can be
applied, if the particles exhibit a drug burst in vivo, and the
extent of the drug burst would be undesired. As a buffer an
acetate buffer can be used.
Microparticles can accordingly be obtained, exhibiting an
improved somatostatin release profile in vivo.
The invention thus also relates to the microparticles prepared
by this process.The invention thus additionally provides a
sustained release formulation prepared by mixing a somatostatin
or a solution of a somatostatin in methanol or water or a buffer
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of pH 3 -8 and a solution of the polylactide-co-glycolide in
methylene chloride and spraying the formed solution, emulsion or
suspension of somatostatin in the polymer solution in a stream
of warm air, collecting the microspheres and washing them in a
buffer solution of pH 3.0 to 8.0 or destilled water and drying
them in a vacuum at a temperature of from 20 to 40°C. Compared
with microparticles, prepared according to the phase separation
technique, they do not contain silicon oil, even not in traces,
since no silicon oil is used in the spray drying technique.
The formulations of the invention may also be prepared using a
triple-emulsion procedure. In a typical technique, peptide e.g.
octreotide is dissolved in a suitable solvent e.g. water and
emulsified intensively into a solution of the polymer, e.g.
50/50 poly(D,L-lactide-co-glycolide)glucose in a solvent, which
is a non-solvent for the peptide, e.g.in methylene chloride.
Examples of the solvent for the polymer matrix material include
methylene chloride, chloroform, benzene, ethyl acetate, and the
like. The resulting water/oil (w/o) emulsion is further
emulsified into an excess of water, containing an emulsifying
substance, e.g. an anionic or non-ionic surfactant or lecithin
or a protective colloid e.g. gelatine, dextrin,
carboxymethylcellulose, polyvinylpyrrolidone, polyvinyl alcohol,
which provides continuous generation of the triple (w/o/w)
emulsion. The microparticles are formed by spontaneous
precipitation of the polymer and hardened by evaporation of the
organic solvent. Gelatine serves to prevent agglomeration of the
microspheres. After sedimentation of the microparticles the
supernatant is decanted and the microparticles are washed with
water and then with acetate buffer. The microparticles are then
filtered and -dried.
The peptide can also be dispersed directly in the polymer
solution, whereafter the resulting suspension is mixed with the
gelatine containing water phase.
The triple emulsion procedure is known from the US-Patent No.
CA 02535463 1990-07-05
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4,652,441. According to this patent in a first step a drug
solution (1) in a solvent, e.g. somatostatin in water (Column 2,
lines 31-32), is thoroughly mixed with an excess of a
polylactide-co-glycolide solution (2) in another solvent, in
which the first solvent is not soluble, e.g. methylene chloride,
giving a water-in-oil type (w/o) emulsion (3) of fine
drug-containing droplets of (1) in solution(2).
In solution (1) is additionally dissolved a so-called
drug-retaining substance (Column 1, line 31), e.g. gelatin,
albumin, pectin, or agar.
In a second step the viscosity of the inner phase (1) is
.increased by appropriate means, like heating, cooling, pH
change, addition of metal ions, or cross linking of e.g. gelatin
with an aldehyde.
In a third step, an excess of water is thoroughly mixed with the
W/o-emulsion (3), (Column 7, lines 52-54), leading to a
W/o/W-type ternary-layer emulsion. In the excess of water a
so-called emulsifying agent may if desired be present (Column 7,
line 56), choosen from the group of e.g. an anionic or nonionic
surfactant or e.g. polyvinyl pyrrolidone, polyvinyl alcohol or
gelatine.
In a fourth step the W/o/W-emulsion is subjected to "in-water
drying", (line 52). This means that the organic solvent in the
oil layer is desorbed to generate microparticles.
The desorption is accomplished in a manner known per se (Column
8, lines 3-5), e.g. by pressure decrease while stirring (Column
8, lines 5-7) or e.g. by blowing nitrogen gas through the oil
layer (e. g. methylene chloride) (line 19).
The formed microparticles are recovered by centrifugation or
filtration (lines 26-27) and the components which are not
incorporated in the polymer are removed by washing with water
(line 29). If desired, the microparticles are warmed under
reduced pressure to achieve) better removal of water and of
solvent (e. g. methylene chloride from the microparticle wall
(lines 30-32).
Whilst the above process is satisfactory for the production of
i
CA 02535463 1990-07-05
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formulations according to the invention, however, the so-called
drug-retaining substance mentioned above, e.g. gelatine,
albumin, pectin or agar, is still enclosed in the resultant
microparticles.
We have now found that when the addition of the drug retaining
substance (= in solution (1)) and the step of increasing the
viscosity of the inner phase is avoided, and in the excess of
water of the ternary w/o/W-emulsion, the measure of adding an
emulsifying substance or a protective colloid, like gelatine is
maintained, satisfactory microparticles can still be obtained.
additionally, the microparticles do not contain any drug
retaining substance, and only a very small quantity of methylene
chloride.
Therefore the invention provides a process for the production of
microparticles prepared by intensively mixing:-
a) a solution of a drug, preferably a somatostatin, especially
octreotide in an aqueous medium, preferably water or a
buffer, preferably in a weight/volume ratio of 0.8 to 4.0 g /
1 to 120 ml, especially 2.5 / 10 and in a buffer of pH 3-8,
especially an acetate buffer, and
b) a solution of a polymer, preferably a polylactide-
co-glycolide, such as mentioned above, in an organic solvent,
not miscible with the aqueous medium, e.g. methylene
chloride, preferably in a weight/volume ratio of 40g/90 to
400m1, especially 40/100, preferably in such a manner that
the weight/weight ratio of the drug to the polymer is from
1/10 to 50, especially 1/16 and the volume/volume ratio of
the aqueous medium/organic solvent is 1/1.5 to 30, especially
1/10, intensively mixing the W/o-emulsion of a) in b)
together with
c) an excess of an aqueous medium, preferably water or a buffer,
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e.g. an acetate or phosphate buffer, preferably of a pH 3-8,
containing an emulsifying substance or a protective colloid,
preferably in a concentration of 0.01 to 15.0X, particularly
gelatine, especially in a concentration of 0.1 to 3 X,
particularly 0.5% of weight, preferably at a volume/volume
mixing speed ratio of ab) / c) of from 1/10 to 100,
especially 1/40,
without adding any drug retaining substance to the water-in-oil
emulsion or applying any intermediate viscosity increasing step,
hardening the embryonic microparticles in the formed
W/o/w -emulsion by desorption, preferably by evaporation, of the
organic solvent, preferably methylene chloride, and
by isolating, optionally washing and drying the generated
microparticles.
The invention also provides the process variant, in which the
drug is dispersed directly in the polymer solution, whereafter
the resulting dispersion is mixed with the gelatine containing
water phase.
The invention also provides to the microparticles, produced by
these processes. Like microparticles prepared according to the
spray drying technique, they do not contain silicon oil.
Compared with microparticles prepared according to the known
triple emulsion process type, they do not contain any amount of
a protective colloid.
The sustained release formulations can also be made by other
methods known per se, e.g.
- if the peptide is stable enough for the production of an
implant, by heating microparticles containing the peptide, e.g.
a somatostatin in a polylactide-co-glycolide, especially such as
described above or a mixture thereof obtained by mixing the
peptide and the polymer, at a temperature of e.g. from 70 to
CA 02535463 1990-07-05
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100°C and extruding and cooling the compact mass, after which
the extrudate is cut and optionally washed and dried.
Conveniently the formulations according to the invention are
produced under aseptic conditions.
The formulations according to the invention may be utilized in
depot form, e.g. injectable microspheres or implants.
They may be administered in conventional manner, e.g.
subcutaneous or intramuscular injection, e.g. for indications
known for the drug contained therein.
The sustained release formulations containing octreotide may be
administered for all the known indications of the octreotide or
derivatives thereof, e.g. those disclosed in GB 2,199,829 A
pages 89-96, as well as for acromegaly and for breast cancer.
The microparticles of this invention may have a size range from
about 1 to 250 microns diameter, preferably 10 to 200,
especially 10 to 130, e.g. 10 to 90 microns. Implants may be
e.g. from about 1 to 10 cubic mm. The amount of drug i.e.
peptide present in the formulation depends on the desired daily
release dosage and thus on the biodegradation rate of the
encapsulating polymer. The exact amount of peptide may be
ascertained by bioavailability trials. The formulations may
contain peptide in an amount from at least 0.2, preferably 0.5
to 20 per cent by weight relative to the polymeric matrix,
preferably 2.0 to 10, especially 3.0 to b7~ of weight.
The release time of the peptide from the microparticle may be
from one or two weeks to about 2 months.
Conveniently the sustained release formulation comprises a
somatostatin, e.g. octreotide in a biodegradable biocompatible
polymeric carrier which, when administered to a rat
CA 02535463 1990-07-05
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subcutaneously at a dosage of 10 mg somatostatin per kg of
animal body weight, exhibits a concentration of a somatostatin
in the blood plasma of at least 0.3 ng/ml and preferably less
than 20 ng/ml during a 30 day term, or conveniently a 60 day's
term.
Alternatively conveniently the sustained release formulation
comprises a somatostatin, e.g. octreotide in a biodegradable
biocompatible polymeric carrier, which, when administered to a
rabbit intramuscularly at a dosage of 5 mg per kg of body
weight, exhibits a concentration of a somatostatin of at least
0.3 ng/ml during a 50 day's term and conveniently a
concentration of at most 20 ng/ml.
Further preferred properties of the obtained somatostatin, e.g.
octreotide containing depot formulations are, depending on the
used production processes:-
Phase separation technique
Rabbit 5 mg of somatostatin/kg, intramuscularly
retardation (0-42 days) 76%
average plasma level (cp, ideal)(0-42 days) 4 ng/ml
AUC (0-42 days) 170 ng/ml x days
Spray dry ng technique:
Rat 10 mg of somatostatin /kg, subcutaneously
retardation (0-42 days) > 75 Y
average plasma level (cp,iaaal) (0-42 days) 4-6 ng/ml
AUC (0-42 days) 170-210 ng/ml x
days
Rabbit 5 mg of somatostatin/kg, intramuscularly
retardation (0-43 days) > 75 9;
average plasma level (cp,iaaai) (0-43 days) 4-6 ng/ml
AUC (0-43 days) 200-240 ng/ml x
CA 02535463 1990-07-05
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days
Triple emulsion technique:
Rat 10 mg of somatostatin/kg, subcutaneously
retardation (0-42 days) > 75 %
average plasma level (cp,iae,l) (0-42 days) 4-6.5 ng/ml
AUC (0-42 days) 170-230 ng/ml x
days
Rabbit 5 mg of somatostatin/kg, intramuscularly
retardation (0-42/43 days) > 74 %
average plasma level (cp,iae,l) (0-42/43 days) 3.5-6.5 ng/ml
AUC (0-42/43 days) 160-270 ng/ml x
days
The invention thus also provides somatostatin preferably
octreotide and octreotide analog compositions, having the
following properties:-
1. a retardation of at least 70%, preferably at least 74%, e.g.
at least 75%, 80%, 88% or at least 89% over a period of from
0 to 42 or 43 days and/or
2. an average plasma level (Cp.;a.ai) of 2,5-6,5, preferably
4-6,5~ng/ml over a period of from 0 to 42 days, in the rat,
when 10 mg of somatostatin is subcutaneously administered
and/or an average plasma level of 3,5-6.5, e.g. 4-6,5 ng/ml
over a period of from 0 to 42 or 43 days in the rabbit when 5
mg of somatostatin is intramuscularly administered and/or
3. an AUC over a period of from 0 to 42 days of at least 160,
preferably of from 170-230 ng/ml x days, for the rat, when 10
mg of somatostatin is subcutaneously administered and/or an
AUC over a period of from 0 to 42 or 43 days of at least 160,
preferably of from 180 to 275, e.g. from 200 to 275 ng/ml x
days for the rabbit, when 5 mg of somatostatin is
intramuscularly administered.
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For the quantitative characterization of the sustained release
formulations described above we use the method of area deviation
(AD) published by F.Nimmerfall and J.Rosenthaler;
Intern.J.Pharmaceut. 32, 1-6 (1986).
In brief, the AD method calculates the area deviations of the
experimental plasma profile from an ideal profile which is a
constant average plasma level (= CP_;,a " 1) produced by
conversion of the experimental area under the plasma level-time
curve (AUC) to a rectangle of equal area. From the percental
area deviation (referred to AUC) the 9; retardation is calculated
as follows:-
7~ retardation = 100 x (1 - AD/AUC)
By this method the whole plasma profile measured over a
preselected time period is characterized by means of a single
numerical index.
In Proc. natl. Acad.Sci.USA 85 (1988) 5688-5692 has been
described in Figure 4 a plasma level profile of the octapeptide
analog of somatostatin of the formula
D-Phe-Cys-Tyr-D-Trp-Lys-Val-Cys-Trp-NHz
in the rat.
However, a clear comparison can not be made with the plasma
level data of the compositions of the invention in the rat,
mentioned just before, since the described plasma level profile
has based on another administration method (intramuscular
injection) and - what is more important- the microcapsules'
loading level (between 2 and 69~) and dosage amount for
administration (25 to 50 mg portions of microcapsules for 30
days, although for at least during 45 days determinations were
made) were not exactly indicated. Additionally the type of used
CA 02535463 1990-07-05
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poly(Dl-lactide-co-glycolide) was not exactly described.
The disclosure value of the publication is thus too low to admit
it to be a prepublication, interfering with the invention.
The following examples illustrate the invention.
Mw of polymers is the mean molecular weight as determined by
GLPC using polystyrene as standard.
EXAMPLE 1:
One g. of poly(D,L-lactide-co-glycolide)(50/50 molar, M" _
45,000; polydispersity ca. 1.7) was dissolved in 15 ml of
methylene chloride with magnetic stirring followed by the
addition of 75 mg of Octreotide acetate dissolved in 0.5 ml of
methanol. Fifteen ml of silicon oil (brand Dow 360 Medical Fluid
1000 cs) (silicone fluid) was added to the polymer-peptide
mixture. The resulting mixture was added to a stirred emulsion
containing 400 ml n-heptane, 100 ml pH 4 phosphate buffer, 40 ml
Dow 360 Medical Fluid~, 350 cs and 2 ml Span 80 (emulsifier).
Stirring was continued for a minimum of 10 minutes. The
resulting microparticles were recovered by vacuum filtration and
dried overnight in a vacuum oven. The yield was approximately
90X of microparticles in the 10 to 40 micron size range.
The microparticles were suspended in a vehicle and administered
IM in a 4 mg dose of Octreotide to white New Zealand rabbits.
Blood samples were taken periodically, indicating plasma levels
of 0.5 to 1.0 ng/ml for 30 days as measured by Radioimmunoassay
{RIA) analysis.
RYAMDT.F 7
One g of poly(D,L-lactide-co-glycolide) glucose (M" = 45,000
(55/45 molar produced according to the process of GB 2,145,422
CA 02535463 1990-07-05
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B; polydispersity ca. 1.7; produced from 0.2% glucose) was
dissolved in 25 ml of ethyl acetate with magnetic stirring
followed by the addition of 75 mg of Octreotide dissolved in 3
ml of methanol. Twentyfive ml of silicon oil (brand Dow 360
Medical Fluid, 1000 cs) was added to the polymer-peptide
mixture. The resulting mixture was added to the emulsion
described in Example 1. Stirring was continued for a minimum of
10 minutes. The resulting microparticles were recovered by
vacuum filtration and dried overnight in a vacuum oven. The
yield was greater than 809; of microparticles in the 10 to 40
micron size range.
The microparticles were suspended in a vehicle and administered
IM in a 4 mg dose of octreotide to white New Zealand rabbits.
Blood samples were taken periodically indicating plasma levels
of 0.5 to 2 ng/ml for 21 days as measured by RIA.
FxeMVT ~ ~
A solution of 1.5 g of Octreotide acetate in 20 ml of methanol
was added with stirring to a solution of 18.5 g
of poly(D,L-lactide-co-glycolide)glucose (50:50 molar, Mw
45,000) in 500 ml of methylene chloride. Phase separation was
effected by adding 500 ml of Dow 360 Medical Fluid (1000 cs) and
800 ml of Dow 360 Medical
Fluid (350 cs) to the peptide-polymer suspension. The resultant
mixture was added to a stirred emulsion consisting
of 1800 ml of n-heptane, 2000 ml of sterile water and 40 ml
of Span 80. After stirring for 10 minutes, the microspheres
were collected by vacuum filtration.
Half of the product was dried overnight in a vacuum oven at
37 C. The residual methylene chloride level was 1.2%.
The other half of the product was washed by stirring with
1000 ml of ethanol containing 1 ml of Span 80. After stirring
CA 02535463 1990-07-05
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for one hour, the ethanol was decanted and the
microparticles were stirred with 1000 ml of n-heptane
containing 1 ml of Span 80. After stirring for one hour, the
microparticles were collected by vacuum filtration and
dried overnight in a vacuum oven at 37 C. The residual
methylene chloride level of the microparticles washed in this
manner was reduced from 1.2% to 0.12%.
The combined yield of the product was 18.2 g (91%) of
microparticles containing 5.69: 0ctreotide, mean diameter
of 24 microns, 1.5% residual heptane.
The microparticles were suspended in a vehicle and injected
intramuscularly in 5 mg/kg dose of Octreotide to white
rabbits. Blood samples were taken periodically, indicating
plasma levels of 0.3 to 7.7 ng/ml for 49 days as measured
by RIA.
EXAMPLE 4:
One g of poly (D,L,-lactide-co-glycolide)glucose Mw 46,000
(50:50) molar produced according to the process of GB 2,145,422
B, Polydispersity ca. 1.7, produced from 0.2% glucose) was
dissolved in 10 ml of methylene chloride with magnetic stirring
followed by the addition of 75 mg of Octreotide dissolved in
0.133 ml of methanol. The mixture was intensively mixed e.g. by
means of an Ultra-Turax~ for one minute at 20,000 rpm causing a
suspension of very small crystals of Octreotide in the polymer
solution.
The suspension was sprayed by means of a high speed turbine
(Niro~ Atomizer) and the small droplets dried in a stream of warm
air generating microparticles. The microparticles were collected
by a Zyklon~ and dried overnight at room temperature in a
vacuum oven.
The microparticles were washed with 1/15 molar acetate buffer
pH4.0 during 5 minutes and dried again at room temperature in a
CA 02535463 1990-07-05
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vacuum oven. After 72 hours the microparticles were sieved
(0.125 mm mesh size) to obtain the final product.
The microparticles were suspended in a vehicle and administered
i.m. in Smg/kg dose of Octreotide to white rabbits (chinchilla-
bastard) and s.c. in a lOmg/kg dose to male rats. Blood samples
were taken periodically, indicating plasma levels of 0.3 to 10.0
ng/ml (5 mg dose) in rabbits and 0.5 to 7.0 ng/ml in rats for 42
days as measured by Radioimmunoassay (RIA) analysis.
RYAMDT_F S
Microparticles were prepared by spray-drying in the same way as
described for example 4 with the only change that Octreotide was
suspended directly in the polymer solution, without use of
methanol.
The microparticles were suspended in a vehicle and administered
s.c. in a 10 mg/kg dose of Octreotide to male rats. Blood
samples were taken periodically, indicating plasma levels of 0.5
to 10.0 ng/ml in rats for 42 days as measured by
Radioimmunoassay (RIA) analysis.
EXAMPLE 6:
One g of poly(D,L,-lactide-co-glycolide)glucose, Mw 46,000
(50:50 molar produced according to the process of GB 2,145,422
B, Polydispersity ca. 1.7, produced from 0.2% glucose) was
dissolved in 2.5 ml of methylene chloride followed by the
addition of 75 mg of Octreotide dissolved in 0.125 ml of
deionized water. The mixture was intensively mixed e.g. by means
of an Ultra-Turax for one minute at 20,000 rpm (inner
W/0-phase).
One g of Gelatine A was dissolved in 200 ml of deionized water
at 50 oC and the solution cooled down to 20°C (outer W-phase).
The W/0- and the W-phases were intensively mixed. Thereby the
inner Wl0-phase was separated into small droplets which were
dispersed homogenously in the outer W-phase. The resulting
CA 02535463 1990-07-05
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triple emulsion was slowly stirred for one hour. Hereby the
methylene chloride was evaporated and the microcapsules were
hardened from the droplets of the inner phase. After
sedimentation of the microparticles the supernatant was sucked
off and the microparticles were recovered by vacuum filtration
and rinsed with water to eliminate gelatine.
Drying, sieving, washing and secondary drying of the
microparticles was done as described for example 4.
The microparticles were suspended in a vehicle and administered
i.m. in 5mg/kg dose of Octreotide to white rabbits (chinchilla-
bastard) and s.c. in a 10 mg/kg dose to male rats. Blood
samples were taken periodically, indicating plasma levels of 0.3
to 15.0 ng/ml (5 mg dose) in rabbits and 0.5 to 8.0 ng/ml in
rats for 42 days as measured by Radioimmunoassay (RIA) analysis.
EXAMPLE 7:
Microparticles were prepared by the triple-emulsion technique in
the same way as desribed for example 6 with three changes:-
1. 0.25 ml of acetate buffer pH 4.0 were used instead of 0.125
ml of water to prepare the inner W/0-phase.
2. rinsing after collection of the microparticles Was carried
out with 1/45 molar acetate buffer pH 4.0 instead of water.
3. further washing of microparticles was omitted.
FXAMPT.R Si
Microparticles were prepared by the triple-emulsion technique in
the same way as described for example 7 with the only change
that the inner W/0-phase was prepared by using water containing
0.7%(w/v) sodium chloride instead of acetate buffer.
EXAMPLE 9:
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Microparticles were prepared in the same manner as described in
example 6, with the only difference, that the drug compound is
dispersed directly in the polymer solution, whereafter the
resulting dispersion is mixed with the gelatine containing
water phase.
EXAMPLE 10:
Octreotide pamoate
.10.19 g of octreotide free base (10 mM) and 3.88 embonoic acid
(10 mM) are dissolved in 1 litre of water/dioxane (1:1). The
reaction mixture is filtered, and lyophilized to give a yellow
powder [aj2°D = + 7.5° (C = 0.35, in DMF), of octreotide pamoate
hydrate. Factor = 1.4 wherein the factor = weight of
lyophilizate/weight of octreotide contained therein.
The pamoate may replace the octreotide acetate present in the
microparticles of Examples 1-9 and has an excellent stability.
EXAMPLE 11:
A solution of 1 g of poly(D,L-lactide-co-glycolide) (50:50
molar, MW= 36,100) in 20 ml of methylene chloride was added with
stirring to a solution of 100 mg of calcitonin in 1.5 ml of
methanol. Phase separation was effected by adding 20 ml of
silicone fluid (Dow 360 Medical Fluid, 1000 cs). The resultant
mixture was added to a stirred emulsion consisting of 100 ml of
pH 4 phosphate buffer, 400 ml of n-heptane, 4 ml of Span 80, and
40 ml of silicone fluid (Dow 360 Medical Fluid, 1000 cs). After
stirring for 10 minutes, the microspheres were collected by
vacuum filtration and dried overnight in a vacuum oven at 37 C.
The yield was 1.1 g of microspheres containing 5.9 X calcitonin.
RXAMP1.R 1 7 ~_
CA 02535463 1990-07-05
s
- 32 -
A solution of 9.9 g of poly(D,L-lactide-co-glycolide) (50/50
- molar, Mw = 44,300) in 140 ml of methylene chloride was added to
100 mg of lypressin. The dispersion was magnetically stirred for
one hour before adding 140 ml of silicone fluid (Dow 360 Medical
Fluid, 1000 cs) and 2,5 ml of Span 80. The mixture was added to
2000 ml of heptane and stirred for 10 minutes. The resulting
microcapsules were collected by vacuum filtration, washed three
times with heptane, and dried 10 minutes under suction. Half of
the sample was washed by stirring in water fox 10 minutes; the
other half was not washed. Both samples were dried overnight in
a vacuum oven at 30 C. The total yield was 10.65 g of
microcapsules. Analysis of the washed sample was 0.59: lypressin
and 0.6% for the sample not washed with water.
