Title: Composition for sustained release of human growth
United States Patent: 6,500,448
Issued: December 31, 2002
Inventors: Johnson; OluFunmi Lily (Cambridge, MA); Ganmukhi;
Medha M. (Carlisle, MA); Bernstein; Howard (Cambridge, MA); Auer; Henry
(Chicago, IL); Khan; M. Amin (Downingtown, PA)
Assignee: Alkermes Controlled Therapeutics, Inc. (Cambridge,
Appl. No.: 505508
Filed: February 17, 2000
A pharmaceutical composition for the sustained release of human growth
hormone from a polymer matrix is disclosed. The pharmaceutical composition
comprises a biocompatible polymer, particles of metal cation-complexed human
growth hormone wherein said particles are dispersed within the biocompatible
polymer and an aqueous injection vehicle.
DETAILED DESCRIPTION OF THE INVENTION
The foregoing and other objects, features and advantages of the invention
will be apparent from the following more particular description of
preferred embodiments of the invention.
The human growth hormone (hGH) used in this invention is biologically
active hGH in its molecular (monomeric or non-aggregated) form. Molecular
hGH is typically non-immunogenic.
Aggregated hGH may induce an immune response resulting in antibodies
formed against hGH. This may compromise the efficacy of long-term hGH
therapy. Additionally, aggregated hGH may stimulate an auto-immune
response to endogenous hGH.
A sustained release of biologically active, non-aggregated human growth
hormone is a release which results in measurable serum levels of
biologically active, monomeric hGH over a period longer than that obtained
following direct administration of aqueous hGH. It is preferred that a
sustained release be a release of hGH for a period of about a week or
more, and more preferably for a period of about two weeks or more.
A sustained release of biologically active, non-aggregated hGH from a
polymeric matrix can be continuous or non-continuous release with
relatively constant or varying rates of release. The continuity of hGH
released and level of hGH released can be established by using, inter alia,
one or more types of polymer compositions, hGH loadings, and/or selection
of excipients to produce the desired effect.
Stabilized (hGH) comprises biologically active, non-aggregated hGH which
is complexed with at least one type of multivalent metal cation, having a
valency of +2 or more, from a metal cation component. Stabilized hGH in
the sustained release composition of the present invention is in
Suitable multivalent metal cations include metal cations contained in
biocompatible metal cation components. A metal cation component is
biocompatible if the cation component is non-toxic to the recipient, in
the quantities used, and also presents no significant deleterious or
untoward effects on the recipient's body, such as an immunological
reaction at the injection site.
Typically, the molar ratio of metal cation component to hGH, for the metal
cation stabilizing the hGH, is between about 4:1 to about 100:1 and more
typically about 4:1 to about 10:1.
A preferred metal cation used to stabilize hGH is Zn+2. In a more
preferred embodiment, the molar ratio of metal cation component,
containing Zn+2 cations, to hGH is about 6:1.
The suitability of a metal cation for stabilizing hGH can be determined by
one of ordinary skill in the art by performing a variety of stability
indicating techniques such as polyacrylamide gel electrophoresis,
isoelectric focusing, reverse phase chromatography, HPLC and potency tests
on hGH lyophilized particles containing metal cations to determine the
potency of the hGH after lyophilization and for the duration of release
from microparticles. In stabilized hGH, the tendency of hGH to aggregate
within a microparticle during hydration in vivo and/or to lose biological
activity or potency due to hydration or due to the process of forming a
sustained release composition, or due to the chemical characteristics of a
sustained release composition, is reduced by complexing at least one type
of metal cation with hGH prior to contacting the hGH with a polymer
Stabilized hGH is typically stabilized against significant aggregation in
vivo over the sustained release period. Significant aggregation is defined
as an amount of aggregation resulting in aggregation of about 15% or more
of the initial amount of encapsulated hGH monomer. Preferably, aggregation
is maintained below about 5% of the initial dose of hGH monomer. More
preferably, aggregation is maintained below about 2% of the initial dose.
The hGH in a hGH sustained release composition can also be mixed with
other excipients, such as bulking agents or additional stabilizing agents,
such as buffers to stabilize the hGH during lyophilization.
Bulking agents typically comprise inert materials. Suitable bulking agents
are known to those skilled in the art.
A polymer, or polymeric matrix, suitable for the sustained release
composition of the present invention, must be biocompatible. A polymer is
biocompatible if the polymer, and any degradation products of the polymer,
are non-toxic to the recipient and also present no significant deleterious
or untoward effects on the recipient's body, such as an immunological
reaction at the injection site.
The polymer of the hGH sustained release composition must also be
biodegradable. Biodegradable, as defined herein, means the composition
will degrade or erode in vivo to form smaller chemical species.
Degradation can result, for example, by enzymatic, chemical and physical
Suitable biocompatible, biodegradable polymers include, for example,
poly(lactides), poly(glycolides), poly(lactide-co-glycolides), poly(lactic
acid)s, poly(glycolic acid)s, poly(lactic acid-co-glycolic acid)s,
polycaprolactone, polycarbonates, polyesteramides, polyanhydrides,
poly(amino acids), polyorthoesters, polycyanoacrylates, poly(p-dioxanone),
poly(alkylene oxalate)s, biodegradable polyurethanes, blends and
Further, the terminal functionalities of the polymer can be modified. For
example, polyesters can be blocked, unblocked or a blend of blocked and
unblocked polymers. A blocked polymer is as classically defined in the
art, specifically having blocked carboxyl end groups. Generally, the
blocking group is derived from the initiator of the polymerization and is
typically an alkyl group. An unblocked polymer is as classically defined
in the art, specifically having free carboxyl end groups.
Acceptable molecular weights for polymers used in this invention can be
determined by a person of ordinary skill in the art taking into
consideration factors such as the desired polymer degradation rate,
physical properties such as mechanical strength, and rate of dissolution
of polymer in solvent. Typically, an acceptable range of molecular weights
is of about 2,000 Daltons to about 2,000,000 Daltons. In a preferred
embodiment, the polymer is a biodegradable polymer or copolymer. In a more
preferred embodiment, the polymer is a poly(lactide-co-glycolide)
(hereinafter "PLGA") with a lactide:glycolide ratio of about 1:1 and a
molecular weight of about 5,000 Daltons to about 70,000 Daltons. In an
even more preferred embodiment, the molecular weight of the PLGA used in
the present invention has a molecular weight of about 6,000 to about
The amount of hGH, which is contained in a dose of sustained release
microparticles, or in an alternate sustained release device, containing
biologically active, stabilized hGH particles is a therapeutically or
prophylactically effective amount, which can be determined by a person of
ordinary skill in the art taking into consideration factors such as body
weight, condition to be treated, type of polymer used, and release rate
from the polymer.
In one embodiment, an hGH sustained release composition contains from
about 0.01% (w/w) to about 50% (w/w) of biologically active, stabilized
hGH particles. The amount of such hGH particles used will vary depending
upon the desired effect of the hGH, the planned release levels, the times
at which hGH should be released, and the time span over which the hGH will
be released. A preferred range of hGH particle loading is between about
0.1% (w/w) to about 30% (w/w) hGH particles. A more preferred range of hGH
particle loading is between about 0.1% (w/w) to about 20% (w/w) hGH
particles. The most preferred loading of the biologically active,
stabilized hGH particles is about 15% (w/w).
In another embodiment, a hGH sustained release composition also contains a
second metal cation component, which is not contained in the stabilized
hGH particles, and which is dispersed within the polymer. The second metal
cation component preferably contains the same species of metal cation, as
is contained in the stabilized hGH. Alternately, the second metal cation
component can contain one or more different species of metal cation.
The second metal cation component acts to modulate the release of the hGH
from the polymeric matrix of the sustained release composition, such as by
acting as a reservoir of metal cations to further lengthen the period of
time over which the hGH is stabilized by a metal cation to enhance the
stability of hGH in the composition.
A metal cation component used in modulating release typically contains at
least one type of multivalent metal cation. Examples of second metal
cation components suitable to modulate hGH release, include, or contain,
for instance, Mg(OH)2, MgCO3 (such as 4.MgCO3 Mg(OH)2.5H2
O), ZnCO3 (such as 3Zn(OH)2.2ZnCO3), CaCO3, Zn3
(C6 H5 O7)2, Mg(OAc)2, MgSO4, Zn(OAc)2,
ZnSO4, ZnCl2, MgCl2 and Mg3 (C6 H5
O7)2. A suitable ratio of second metal cation
component-to-polymer is between about 1:99 to about 1:2 by weight. The
optimum ratio depends upon the polymer and the second metal cation
A polymeric matrix containing a dispersed metal cation component to
modulate the release of a biologically active agent from the polymeric
matrix is further described in U.S. Pat. No. 5,656,297 to Bernstein et
al., and co-pending PCT Patent Application PCT/US95/05511, the teachings
of which are incorporated herein by reference in their entirety.
The hGH sustained release composition of this invention can be formed into
many shapes such as a film, a pellet, a cylinder, a disc or a
microparticle. A microparticle, as defined herein, comprises a polymeric
component having a diameter of less than about one millimeter and having
stabilized hGH particles dispersed therein. A microparticle can have a
spherical, non-spherical or irregular shape. It is preferred that a
microparticle be a microsphere. Typically, the microparticle will be of a
size suitable for injection. A preferred size range for microparticles is
from about 1 to about 180 microns in diameter.
In the method of this invention for forming a composition for the
sustained release of biologically active, non-aggregated hGH, a suitable
amount of particles of biologically active, stabilized hGH are dispersed
in a polymer solution.
A suitable polymer solution contains between about 1% (w/w) and about 30%
(w/w) of a suitable biocompatible polymer, wherein the biocompatible
polymer is typically dissolved in a suitable polymer solvent. Preferably,
a polymer solution contains about 2% (w/v) to about 20% (w/v) polymer. A
polymer solution containing 5% to about 10% (w/w) polymer is most
A suitable polymer solvent, as defined herein, is solvent in which the
polymer is soluble but in which the stabilized hGH particles are
substantially insoluble and non-reactive. Examples of suitable polymer
solvents include polar organic liquids, such as methylene chloride,
chloroform, ethyl acetate and acetone.
To prepare biologically active, stabilized hGH particles, hGH is mixed in
a suitable aqueous solvent with at least one suitable metal cation
component under pH conditions suitable for forming a complex of metal
cation and hGH. Typically, the complexed hGH will be in the form of a
cloudy precipitate, which is suspended in the solvent. However, the
complexed hGH can also be in solution. In an even more preferred
embodiment, hGH is complexed with Zn+2.
Suitable pH conditions to form a complex of hGH typically include pH
values between about 7.0 and about 7.4. Suitable pH conditions are
typically achieved through use of an aqueous buffer, such as sodium
bicarbonate, as the solvent.
Suitable solvents are those in which the hGH and the metal cation
component are each at least slightly soluble, such as in an aqueous sodium
bicarbonate buffer. For aqueous solvents, it is preferred that water used
be either deionized water or water-for-injection (WFI).
It is understood that the hGH can be in a solid or a dissolved state,
prior to being contacted with the metal cation component. It is also
understood that the metal cation component can be in a solid or a
dissolved state, prior to being contacted with the hGH. In a preferred
embodiment, a buffered aqueous solution of hGH is mixed with an aqueous
solution of the metal cation component.
Typically, the complexed hGH will be in the form of a cloudy precipitate,
which is suspended in the solvent. However, the complexed hGH can also be
in solution. In an even more preferred embodiment, hGH is complexed with
The complexed hGH is then dried, such as by lyophilization, to form a
particulate of stabilized hGH. The complexed hGH, which is suspended or in
solution, can be bulk lyophilized or can be divided into smaller volumes
which are then lyophilized. In a preferred embodiment, the complexed hGH
suspension is micronized, such as by use of an ultrasonic nozzle, and then
lyophilized to form stabilized hGH particles. Acceptable means to
lyophilize the complexed hGH mixture include those known in the art.
Preferably, particles of stabilized hGH are between about 1 to about 6
micrometers in diameter. The hGH particles can be fragmented separately,
as described in co-pending U.S. patent application Ser. No. 08/006,682,
filed Jan. 21, 1993, which describes a process for producing small
particles of biologically active agents, which is incorporated herein in
its entirety by reference. Alternately, the hGH particles can be
fragmented after being added to a polymer solution, such as by means of an
ultrasonic probe or ultrasonic nozzle.
In another embodiment, a second metal cation component, which is not
contained in the stabilized hGH particles, is also dispersed within the
It is understood that a second metal cation component and stabilized hGH
can be dispersed into a polymer solution sequentially, in reverse order,
intermittently, separately or through concurrent additions. Alternately, a
polymer, a second metal cation component and stabilized hGH and can be
mixed into a polymer solvent sequentially, in reverse order,
intermittently, separately or through concurrent additions.
The method for forming a composition for modulating the release of a
biologically active agent from a biodegradable polymer is further
described in U.S. Pat. No. 5,656,297 to Bernstein et al.
In this method, the polymer solvent is then solidified to form a polymeric
matrix containing a dispersion of stabilized hGH particles.
One suitable method for forming an hGH sustained release composition from
a polymer solution is the solvent evaporation method described in U.S.
Pat. No. 3,737,337, issued to Schnoring et al., U.S. Pat. No. 3,523,906,
issued to Vranchen et al., U.S. Pat. No. 3,691,090, issued to Kitajima et
al., or U.S. Pat. No. 4,389,330, issued to Tice et al. Solvent evaporation
is typically used as a method to form hGH sustained release microparticles.
In the solvent evaporation method, a polymer solution containing a
stabilized hGH particle dispersion, is mixed in or agitated with a
continuous phase, in which the polymer solvent is partially miscible, to
form an emulsion. The continuous phase is usually an aqueous solvent.
Emulsifiers are often included in the continuous phase to stabilize the
emulsion. The polymer solvent is then evaporated over a period of several
hours or more, thereby solidifying the polymer to form a polymeric matrix
having a dispersion of stabilized hGH particles contained therein.
A preferred method for forming hGH sustained release microparticles from a
polymer solution is described in U.S. Pat. No. 5,019,400, issued to
Gombotz et al., and co-pending U.S. patent application Ser. No.
08/443,726, filed May 18, 1995, the teachings of which are incorporated
herein by reference in their entirety. This method of microsphere
formation, as compared to other methods, such as phase separation,
additionally reduces the amount of hGH required to produce a sustained
release composition with a specific hGH content.
In this method, the polymer solution, containing the stabilized hGH
particle dispersion, is processed to create droplets, wherein at least a
significant portion of the droplets contain polymer solution and the
stabilized hGH particles. These droplets are then frozen by means suitable
to form microparticles. Examples of means for processing the polymer
solution dispersion to form droplets include directing the dispersion
through an ultrasonic nozzle, pressure nozzle, Rayleigh jet, or by other
known means for creating droplets from a solution.
Means suitable for freezing droplets to form microparticles include
directing the droplets into or near a liquified gas, such as liquid argon
and liquid nitrogen to form frozen microdroplets which are then separated
from the liquid gas. The frozen microdroplets are then exposed to a liquid
non-solvent, such as ethanol, or ethanol mixed with hexane or pentane.
The solvent in the frozen microdroplets is extracted as a solid and/or
liquid into the non-solvent to form stabilized hGH containing
nicroparticles. Mixing ethanol with other non-solvents, such as hexane or
pentane, can increase the rate of solvent extraction, above that achieved
by ethanol alone, from certain polymers, such as poly(lactide-co-glycolide)
A wide range of sizes of hGH sustained release microparticles can be made
by varying the droplet size, for example, by changing the ultrasonic
nozzle diameter. If very large microparticles are desired, the
microparticles can be extruded through a syringe directly into the cold
liquid. Increasing the viscosity of the polymer solution can also increase
microparticle size. The size of the microparticles can be produced by this
process, for example microparticles ranging from greater than about 1000
to about 1 micrometers in diameter. Yet another method of forming an hGH
sustained release composition, from a polymer solution, includes film
casting, such as in a mold, to form a film or a shape. For instance, after
putting the polymer solution containing a dispersion of stabilized hGH
particles into a mold, the polymer solvent is then removed by means known
in the art, or the temperature of the polymer solution is reduced, until a
film or shape, with a consistent dry weight, is obtained. Film casting of
a polymer solution, containing a biologically active agent, is further
described in U.S. Pat. No. 5,656,297 to Bernstein et al., the teachings of
which are incorporated herein by reference in their entirety.
It is believed that the release of the hGH can occur by two different
mechanisms. The hGH can be released by diffusion through aqueous filled
channels generated in the polymeric matrix, such as by the dissolution of
the hGH or by voids created by the removal of the polymer's solvent during
the synthesis of the sustained release composition.
A second mechanism is the release of hGH due to degradation of the
polymer. The rate of degradation can be controlled by changing polymer
properties that influence the rate of hydration of the polymer. These
properties include, for instance, the ratio of different monomers, such as
lactide and glycolide, comprising a polymer; the use of the L-isomer of a
monomer instead of a racemic mixture; and the molecular weight of the
polymer. These properties can affect hydrophilicity and crystallinity,
which control the rate of hydration of the polymer. Hydrophilic excipients
such as salts, carbohydrates and surfactants can also be incorporated to
increase hydration and which can alter the rate of erosion of the polymer.
By altering the properties of the polymer, the contributions of diffusion
and/or polymer degradation to hGH release can be controlled. For example,
increasing the glycolide content of a poly(lactide-co-glycolide) polymer
and decreasing the molecular weight of the polymer can enhance the
hydrolysis of the polymer and thus, provides an increased hGH release from
In addition, the rate of polymer hydrolysis is increased in non-neutral
pH's. Therefore, an acidic or a basic excipient can be added to the
polymer solution, used to form the microsphere, to alter the polymer
The composition of this invention can be administered to a human, or other
animal, by injection, implantation (e.g, subcutaneously, intramuscularly,
intraperitoneally, intracranially, intravaginally and intradermally),
administration to mucosal membranes (e.g., intranasally or by means of a
suppository), or in situ delivery (e.g. by enema or aerosol spray) to
provide the desired dosage of hGH based on the known parameters for
treatment with hGH of the various medical conditions.
Claim 1 of 37 Claims
What is claimed is:
1. A pharmaceutical composition for the sustained release of human growth
hormone from a polymer matrix, comprising:
a) a biocompatible polymer;
b) particles of metal cation-complexed human growth hormone, wherein said
particles are dispersed within the biocompatible polymer; and
c) an aqueous injection vehicle comprising about 3% weight/volume of
sodium carboxymethyl cellulose wherein the sodium carboxymethyl cellulose
is low viscosity.
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