U.S. patent application number 12/391836 was filed with the patent office on 2009-12-10 for delivery of corticosteroids through iontophoresis.
This patent application is currently assigned to EyeGate Pharmaceuticals, Inc.. Invention is credited to Perry Calias, Gary Cook, Mike Jaffe, Michael A. Patane.
Application Number | 20090306579 12/391836 |
Document ID | / |
Family ID | 41016683 |
Filed Date | 2009-12-10 |
United States Patent
Application |
20090306579 |
Kind Code |
A1 |
Jaffe; Mike ; et
al. |
December 10, 2009 |
DELIVERY OF CORTICOSTEROIDS THROUGH IONTOPHORESIS
Abstract
Disclosed herein are formulations of dexamethasone or a prodrug
thereof suitable for delivery by ocular iontophoresis and methods
of use thereof.
Inventors: |
Jaffe; Mike; (East Hartford,
CT) ; Cook; Gary; (Westford, MA) ; Calias;
Perry; (Melrose, MA) ; Patane; Michael A.;
(Andover, MA) |
Correspondence
Address: |
FOLEY & LARDNER LLP
111 HUNTINGTON AVENUE, 26TH FLOOR
BOSTON
MA
02199-7610
US
|
Assignee: |
EyeGate Pharmaceuticals,
Inc.
|
Family ID: |
41016683 |
Appl. No.: |
12/391836 |
Filed: |
February 24, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61031267 |
Feb 25, 2008 |
|
|
|
61047950 |
Apr 25, 2008 |
|
|
|
Current U.S.
Class: |
604/20 ;
514/180 |
Current CPC
Class: |
A61N 1/0448 20130101;
A61P 29/00 20180101; A61N 1/303 20130101; A61K 9/0048 20130101;
A61N 1/044 20130101; A61F 9/0008 20130101; A61K 41/00 20130101;
A61P 27/02 20180101; A61K 9/0009 20130101; A61K 31/573
20130101 |
Class at
Publication: |
604/20 ;
514/180 |
International
Class: |
A61N 1/30 20060101
A61N001/30; A61K 31/573 20060101 A61K031/573; A61P 29/00 20060101
A61P029/00; A61P 27/02 20060101 A61P027/02 |
Claims
1. A method for iontophoretically delivering a corticosteroid,
corticosteroid derivative, prodrug or salt thereof into the eye of
a subject, comprising: a) administering the compound to the eye of
the subject; and b) performing ocular iontophoresis under
conditions such that the pH is between about 2.5 and about 6.5,
thereby delivering the compound into the eye.
2. The method of claim 1, wherein the corticosteroid is a
dexamethasone compound, derivative thereof.
3. The method of claim 2, wherein the starting pH is about 5.7.
4. The method of claim 1, wherein the corticosteroid is in the form
of a prodrug.
5. The method of claim 1, wherein the corticosteroid is delivered
by injection prior to iontophoresis.
6. The method of claim 5, wherein the method of injection is
selected from the group consisting of: an intracameral injection,
an intracorneal injection, a subconjonctival injection, a subtenon
injection, a subretinal injection, an intravitreal injection and an
injection into the anterior chamber.
7. The method of claim 1, wherein the corticosteroid is
administered topically prior to iontophoresis.
8. The method of claim 7, wherein the topical administration
comprises providing the corticosteroid in a form selected from the
group consisting of: a liquid solution, a paste and a hydro
gel.
9. The method of claim 7, wherein the corticosteroid is embedded in
a foam matrix.
10. The method of claim 7, wherein the corticosteroid is supported
in a reservoir.
11. The method of claim 1, wherein the step of ocular iontophoresis
is carried out prior to, during or after the step of administering
the corticosteroid.
12. The method of claim 1, wherein the compound is delivered by an
iontophoretic dose of about 1.7.times.10.sup.-4 mAmin to about 120
mAmin.
13. The method of claim 12, wherein the compound is delivered by an
iontophoretic dose of between about 10 mAmin and about 30
mAmin.
14. The method of claim 13, wherein the iontophoretic dose is about
20 mAmin.
15. The method of claim 14, wherein the compound is delivered at a
current of about 4.0 mA for a period of about 5 minutes.
16. The method of claim 12, wherein the compound is delivered at a
variable or fixed current of less than about 10 mA.
17. The method of claim 12, wherein the compound is delivered for a
time of less than about 10 minutes.
18. A kit for iontophoretically delivering dexamethasone into the
eye of a subject, wherein the kit is to be used for iontophoresis
between a pH range of about 2.5 to about 6.5, and an apparatus for
iontophoretically delivering the compound into the eye of a
subject.
19. A dexamethasone formulation suitable for ocular iontophoretic
delivery into the eye of a subject.
20. The formulation of claim 19, wherein the dexamethasone is in
the form of a prodrug.
21. The formulation of claim 19, wherein iontophoretic delivery is
to be performed in a pH range of between about 2.5 and about
6.5.
22. The formulation of claim 21, wherein the pH is about 5.7.
23. A device for delivering dexamethasone, comprising: a) a
reservoir comprising at least at least one medium comprising a
dexamethasone formulation, the reservoir extending along a surface
intended to cover a portion of an eyeball; and b) an electrode
associated with the reservoir so as to, when polarized, supply an
electric field directed through the medium and toward a surface of
the eye, wherein at least a portion of the dexamethasone
formulation is delivered transdermally through the surface of the
eye through iontophoresis.
24. The device of claim 23, wherein the reservoir comprises; a) a
first container for receiving the at least one medium comprising
the dexamethasone formulation; b) a second container for receiving
an electrical conductive medium comprising electrical conductive
elements; and c) a semi-permeable membrane positioned between the
first and second containers, the semi-permeable membrane being
permeable to electrical conductive elements and non-permeable to
the active substances.
25. A method for treating a corticosteroid-sensitive ophthalmic
disease in a mammal, comprising administering an effective amount
of a corticosteroid by ocular iontophoresis.
26. The method of claim 25, wherein the ophthalmic disease is
selected from the group consisting of: uveitis, dry eye,
post-operative inflammation and corneal graft rejection.
27. The method of claim 26, wherein the corticosteroid is
dexamethasone phosphate.
28. The method of claim 27, wherein administration of dexamethasone
phosphate occurs in a single dose.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application 61/031,267, filed Feb. 25, 2008, and U.S. Provisional
Application 61/047,950, filed Apr. 25, 2008, the entire contents of
each of which are incorporated herein by reference.
BACKGROUND
[0002] Corticosteroids are widely prescribed therapeutics.
Systemic, topical and injected formulations are routinely employed
for a variety of ophthalmic conditions. In particular, topical
applications account for the widest use of non-invasively delivered
corticosteroids for ocular disorders. This approach, however,
suffers from low bioavailability and, thus, limited efficacy.
[0003] Dexamethasone, member of the glucocorticoid class of steroid
hormones, acts as an anti-inflammatory and immunosuppressant.
Ocular formulations are used that allow for diffusion of
dexamethasone across an ocular membrane, however, such topical
formulations suffer from slow, inadequate and uneven uptake.
Because current ocular delivery methods achieve low ocular
exposures, frequent applications are required and compliance issues
are significant.
[0004] Topical dexamethasone applications involving ocular
iontophoresis have not been described. Based on
commercially-available, columbic-controlled iontophoresis for
topical applications to the skin of a variety of therapeutics, it
is clear that even well understood pharmaceuticals require
customized formulations for iontophoresis. These alterations
maximize dosing effectiveness, improve the safety and manage
commercial challenges. The known technical formulation challenges
presented by dermatological applications may translate in to ocular
delivery. However, ocular iontophoresis presents additional
formulation needs. Thus, developing novel formulations that are
ideally suited for ocular iontophoretic delivery of corticosteroids
is required. Such formulations include many variables, including:
API concentration, solute, excipients, stabilizers, buffering
agents, delivery applicator, iontophoretic dose, etc. Developing
corticosteroids suitable for non-invasive local ocular delivery
will significantly expand treatment options for
ophthalmologists.
SUMMARY
[0005] Described herein are devices and methods for enhancing the
delivery of negatively charged compounds into and through tissues,
e.g., the eye. More specifically, the methods and devices described
herein utilize iontophoresis to actively deliver a compound, e.g.,
dexamethasone phosphate, into a mammalian eye. The methods and
devices focus on developing corticosteroid formulations and use of
these formulations to maximize drag delivery, e.g., through
iontophoresis, and patient safety. These novel formulations are
suitable for treating a variety of inflammatory-mediated ocular
disorders. The formulations, which include different strengths of
the active pharmaceutical ingredient (API), are capable of being
used with different iontophoretic doses (e.g., current levels and
application times). These solutions can, for example: (1) be
appropriately buffered to manage initial and terminal pHs, (2) be
stabilized to manage shelf-life (chemical stability), and/or (3)
include other excipients that modulate osmolarity. Furthermore, the
drug product solutions are crafted to minimize the presence of
competing ions. These unique dosage forms can address a variety of
therapeutic needs. Ocular iontophoresis is a novel, non-invasive,
out-patient approach for delivering substantial amounts of APIs
into many ocular tissues. This non-invasive approach can lead to
results comparable to or better than those achieve with ocular
injections, without the significant risk of infection associated
with the latter.
[0006] One embodiment is directed to a method for iontophoretically
delivering a corticosteroid, corticosteroid derivative, prodrug or
salt thereof into the eye of a subject, comprising: a)
administering the compound to the eye of the subject; and b)
performing ocular iontophoresis under conditions such that the pH
is between about 2.5 and about 6.5, thereby delivering the compound
into the eye. In a particular embodiment, the corticosteroid is a
dexamethasone compound, derivative thereof. In a particular
embodiment, the starting pH is about 5.7. In a particular
embodiment, the corticosteroid is in the form of a prodrug. In a
particular embodiment, the corticosteroid is delivered by injection
prior to iontophoresis. In a particular embodiment, the method of
injection is selected from the group consisting of: an intracameral
injection, an intracorneal injection, a subconjonctival injection,
a subtenon injection, a subretinal injection, an intravitreal
injection and an injection into the anterior chamber. In a
particular embodiment, the corticosteroid is administered topically
prior to iontophoresis. In a particular embodiment, the topical
administration comprises providing the corticosteroid in a form
selected from the group consisting of: a liquid solution, a paste
and a hydro gel. In a particular embodiment, the corticosteroid is
embedded in a foam matrix. In a particular embodiment, the
corticosteroid is supported in a reservoir. In a particular
embodiment, the step of ocular iontophoresis is carried out prior
to, during or after the step of administering the corticosteroid.
In a particular embodiment, the compound is delivered by an
iontophoretic dose of about 1.7.times.10.sup.4 mAmin to about 120
mAmin, e.g., between about 10 mAmin and about 30 mAmin. In a
particular embodiment, the iontophoretic dose is about 20 mAmin. In
a particular embodiment, the compound is delivered at a current of
about 4.0 mA for a period of about 5 minutes. In a particular
embodiment, the compound is delivered at a variable or fixed
current of less than about 10 mA. In a particular embodiment, the
compound is delivered for a time of less than about 10 minutes.
[0007] One embodiment is directed to a kit for iontophoretically
delivering dexamethasone into the eye of a subject, wherein the kit
is to be used for iontophoresis between a pH range of about 2.5 to
about 6.5, and an apparatus for iontophoretically delivering the
compound into the eye of a subject.
[0008] One embodiment is directed to a dexamethasone formulation
suitable for ocular iontophoretic delivery into the eye of a
subject. In a particular embodiment, the dexamethasone is in the
form of a prodrug. In a particular embodiment, iontophoretic
delivery is to be performed in a pH range of between about 2.5 and
about 6.5, In a particular embodiment, the pH is about 5.7.
[0009] One embodiment is directed to a device for delivering
dexamethasone, comprising: a) a reservoir comprising at least at
least one medium comprising a dexamethasone formulation, the
reservoir extending along a surface intended to cover a portion of
an eyeball; and b) an electrode associated with the reservoir so as
to, when polarized, supply an electric field directed through the
medium and toward a surface of the eye, wherein at least a portion
of the dexamethasone formulation is delivered transdermally through
the surface of the eye through iontophoresis. In a particular
embodiment, the reservoir comprises: a) a first container for
receiving the at least one medium comprising the dexamethasone
formulation; b) a second container for receiving an electrical
conductive medium, comprising electrical conductive elements; and
c) a semi-permeable membrane positioned between the first and
second containers, the semi-permeable membrane being permeable to
electrical conductive elements and non-permeable to the active
substances.
[0010] One embodiment is directed to a method for treating a
corticosteroid sensitive ophthalmic disease in a mammal, comprising
administering an effective amount of a corticosteroid by ocular
iontophoresis. In a particular embodiment, the ophthalmic disease
is selected from the group consisting of: uveitis, dry eye, post
operative inflammation and corneal graft rejection. In a particular
embodiment, the corticosteroid is dexamethasone phosphate. In a
particular embodiment, administration of dexamethasone phosphate
occurs in a single dose.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a schematic overview of the iontophoresis
apparatus and procedure.
[0012] FIG. 2 is a graph showing in vitro delivery of DEX
phosphate.
[0013] FIG. 3 is a graph showing in vitro delivery of DEX phosphate
using varying sodium citrate concentrations.
[0014] FIG. 4 is a graph showing linear dependence of DEX phosphate
flux on applied current (mean.+-.SD, n=4).
[0015] FIG. 5 is an image showing the setup of iontophoretic dosing
in New Zealand rabbit eyes with the Eye Gate II device and
generator.
[0016] FIG. 6 is a graph showing tear flow measurement in rabbits
injected in the lacrimal gland with either Concanavalin A or
phosphate-buffered, saline (n=8 for each group). Rabbits were given
a single iontophoretic dose of either dexamethasone phosphate or
phosphate-buffered saline on Day 2. Tear flow was measured, with
Schirmer strips and was recorded as the distance in mm of flow in 5
minutes. (*=P<0.01).
[0017] FIG. 7 are representative slit-lamp microscope images of
fluorescein staining on the ocular surface of rabbits on Day 8 of
the study. Left panel: Group 1--Rabbit had Con A-induced dry eye
and was iontophoretically treated with saline on Day 2. Middle
Panel: Group 2--Rabbit had Con A-induced dry eye and was
iontophoretically treated with Dex-P on Day 2. Right panel: Group
3--Rabbit was Injected with saline and was iontophoretically
treated with saline on Day 2.
[0018] FIG. 8 is a graph showing fluorescein staining score in
rabbits after a single iontophoretic dose of either dexamethasone
phosphate solution or phosphate-buffered saline in the lacrimal
gland (n=8 for each group). *=P<0.01).
[0019] FIG. 9 is a graph showing the expression of
interleukin-1beta (IL-1.beta.) in the lacrimal glands and corneas
of rabbits on Day 4 or Day 8 after lacrimal gland injection of
concanavalin A or saline and iontophoretic treatment with
dexamethasone phosphate or saline on Day 2. n=4, *=P<0.01. No
significant difference was noted in the cornea, indicating a
specific lacrimal gland inflammatory response.
[0020] FIG. 10 is a graph showing expression of transforming growth
factor beta-1 (TGF-.beta.1) in the lacrimal glands and corneas of
rabbits on Day 4 or Day 8 after lacrimal gland injection of
concanavalin A or saline and iontophoretic treatment with
dexamethasone phosphate or saline on Day 2. n=4, *=P<0.01. No
significant difference was noted in the cornea, indicating a
specific lacrimal gland inflammatory response.
DETAILED DESCRIPTION
[0021] The process of iontophoresis involves applying a current to
an ionizable substance, for example a drug product, to increase its
mobility across a surface. Three principle forces govern the flux
caused by the current. The primary force is electrochemical
repulsion, which propels like charged species through surfaces
(tissues). The earliest investigations of iontophoresis involve
transdermal applications.
[0022] When an electric current passes through an aqueous solution
containing electrolytes and a charged material (for example, the
active pharmaceutical ingredient or API), several events occur: (1)
the electrode generates ions, (2) the newly generated ions
approach/collide with like charged particles (typically the drug
being delivered), and (3) the eleetrorepulsion between the newly
generated ions force the dissolved/suspended charged particles (the
API) into and/or through the surface adjacent (tissue) to the
electrode. Continuous application of electrical current drives the
API significantly further into the tissues than is achieved with
simple topical administration. The degree of iontophoresis is
proportional to the applied current and the treatment time.
Corticosteroids can be delivered at fixed or variable current
settings ranging from, for example, about 1 mA to about 10 mA. The
overall iontophoretic dose is a function of current and time. The
iontophoretic dose, for example, can be applied over a period of
less than about 10 minutes, less than about 15 minutes, less than
about 20 minutes, or about 5 minutes.
[0023] Iontophoresis occurs in water-based preparations, where ions
can be readily generated by electrodes. Two types of electrodes can
be used to produce ions: (1) inert electrodes and (2) active
electrodes. Each type of electrode requires aqueous media
containing electrolytes. Iontophoresis with an inert electrode is
governed by the extent of water hydrolysis that an applied current
can produce. The electrolysis reaction yields either hydroxide
(cathodic) or hydronium (anodic) ions. Some formulations contain
buffers, which can mitigate pH shifts caused by these ions. The
presence of certain buffers introduces like charged ions that can
compete with the drug product for ions generated electrolytically,
which can decrease delivery of the drug product. The electrical
polarity of the drug delivery electrode is dependent on the
chemical nature of the drug product, specifically its
pK.sub.a(s)/isoelectric point and the initial dosing solution pH.
It is primarily the electrochemical repulsion between the ions
generated via electrolysis and the drug product's charge that
drives the drug product into tissues. Thus, iontophoresis offers a
significant advantage over topical drug application, in that it
increases drug absorption. The rate of drug delivery may be
adjusted by varying the applied current, as determined by one of
skill in the art.
[0024] Ocular iontophoresis has been reported in the literature,
but the fundamental understanding of this approach for drug
delivery, especially at the typically much higher currents used, is
not at the same level as that for transdermal electrotransport. The
present invention, therefore, is directed to unexpected discoveries
about the formulations and conditions for using particular DEX
phosphate formulations for ocular iontophoresis. In particular,
electrical properties of the sclera (charge, permselectivity, pI)
and the basics of iontophoretic transport of model anionic species
(e.g., buffered DEX phosphate) are described.
DEFINITIONS
[0025] As used herein, the term "subject" refers to an animal, in
particular, a mammal, e.g., a human.
[0026] As used herein, the term "efficacy" refers to the degree to
which a desired effect is obtained. Specifically, the term refers
to the degree to which dexamethasone or a prodrug thereof is
effective in treating inflammation. The term "efficacy" as used in
the context of the present invention, also refers to relief or
reduction of one or more symptoms or clinical events associated
with inflammation.
[0027] As used herein, "anterior uveitis" refers to an intraocular
inflammation of the anterior portion of the uvea (i.e., the iris
and ciliary body). "Iritis" refers to an inflammation, of the iris
only, while "iridocyclitis" involves both the iris and the ciliary
body. The terms "anterior uveitis", "iritis", and "iridocyclitis"
are often used synonymously. Anterior uveitis is termed "acute"
when the inflammation lasts less than 12 weeks or "chronic" when it
lasts longer. Chronic anterior uveitis is characterized by a
duration of greater than three months and the recurrence of the
disease with multiple episodes. Recurrence indicates the return of
intraocular inflammation after a period of quiescence.
[0028] As used, herein, "DEX" generally refers to dexamethasone
compounds, derivatives and salts thereof, e.g., dexamethasone
phosphate, dexamethasone sodium phosphate. As used herein, the term
"derivative" can refer to a chemical modification, for example, of
a corticosteroid.
[0029] As used herein, "glucocorticoids" refers to corticosteroids,
often useful in treating various inflammation disorders.
Glucocorticoids or corticosteroids, like dexamethasone, suppress
inflammation by inhibiting, for example, edema, fibrin, deposition,
capillary deposition, and phagocytic migration of the inflammatory
response. As in other tissues, corticosteroids do not appear to
have specific effects in ocular tissues but exert a broad spectrum
of anti-inflammatory activity. The effects of corticosteroids in
ocular tissues include: 1) reduction of the cellular immune
response, 2) reduction of inflammatory vascular permeability, 3)
stabilization of the blood-aqueous barrier, 4) limitation of
fibrinoid exudation, 4) inhibition of fibroblast
transdifferentiation, 5) inhibition of epithelial proliferation, 6)
inhibition of inflammatory corneal neovascularization, 7)
retardation of wound healing, 8) elevation of intraocular pressure,
and 9) induction of cataract. Corticosteroids also inhibit
leukocyte movement to the inflamed site and may reduce the ability
of leukocytes to remain in the inflamed areas.
Active Pharmaceutical Ingredients
APIs
[0030] The present invention is directed to methods and
formulations comprising one or more of DEX, DEX phosphate and DEX
sodium phosphate. Active substances, e.g., dexamethasone and
formulations thereof, are preferably present in a concentration
between approximately 0.1 mg and approximately 100 mg per ml of
medium.
[0031] The active substances are ionizabie by themselves or are in
a form that facilitates their ionization. Thus, it is possible to
bond active substances to additives presenting terminating ions,
such as, for example, a polymer, a dendrimer, a polymer
nanoparticle or a microsphere, or a liposome (the active substance
is then contained in the aqueous core and not in the wall of the
liposome). Various other examples of techniques for improving
active substances ionization are known in the art (Bourlais, C. et
al. Prog. Retin Eye Res., 17:33-58, 1998; Ding, S., Pharm. Sci.
Tech, Today, 1:328-335 1998; Lallemand, F. et al., Eur. J. Pharm.
Biopharm., 56:307-318, 2003).
Methods for Treating Ocular Inflammation
[0032] Corticosteroids have unparalleled anti-inflammatory effects
and rapid onset of action. Corticosteroid ophthalmic solutions have
been used to treat acute inflammatory conditions in the anterior
eye tissues (McGhee, C. et al., Drug Saf., 25:33-55, 2002). Two
clinical studies, for example, demonstrate that topical application
of a potent corticosteroid using a short-term, intensive-dosing
regimen alleviates acute dry eye signs and symptoms in patients
with moderate to severe keratoconjunctivitis sicca (KCS) who were
unresponsive to artificial tear supplementation (Marsh, P. and
Pflugfelder, S., Ophthalmology, 106:811-816, 1999; Hong, S. et al.,
J. Ocul. Pharmacol. Ther., 23:78-82, 2007). Patients experienced
dry eye signs and symptoms relief for time periods that extended
significantly beyond the active dosing period, suggesting that the
treatment modified the underlying causative inflammatory pathology.
Topical corticosteroids remain the mainstay treatment for corneal
graft rejection episodes. The pharmacological effects of steroids
include blockage of the prostaglandin synthesis by inhibiting
phospholipase A2 and the lipo-oxygenase pathways, decrease of both
cellular and fibrinous exudation, inhibition of chemotaxis and
phagocytosis, restoration of capillary permeability, stabilisation
of the lysosomal membranes of polymorphonuclear cells (PMN), and
inhibition of graft vascularization.
[0033] Anterior uveitis encompasses a wide range of etiologies; the
most common form of anterior uveitis is of unknown etiology. The
signs and symptoms of uveitis vary with etiology and location of
inflammation. Anterior uveitis is differentiated from more common
types of ocular inflammation by its presentation of pain or
photophobia, circumlimbal redness and anterior chamber cells and
flare. Patients with anterior uveitis may exhibit symptoms of pain
in one eye unless the anterior uveitis is secondary to a systemic
disease, in which case pain or redness is not necessarily a
symptom. Common vision-threatening complications of anterior
uveitis (e.g., posterior subcapsular cataract (PSC), glaucoma and
macular edema) generally occur due to its recurrent nature.
[0034] Medical management of anterior uveitis depends on severity
and consists of topical or systemic corticosteroid treatment and
often with cycloplegics. When topical steroid drops are used, the
frequency of treatment can range from every 15 to 30 minutes, to
every hour, or to every other day depending on the severity of the
inflammation being treated. The role of corticosteroids in treating
anterior uveitis is to decrease inflammation by reducing, for
example, the production of exudates, stabilizing cell membranes,
inhibiting the release of lysozyme by granulocytes, and suppressing
the circulation of lymphocytes. Cycloplegics serve three purposes
in the treatment of anterior uveitis: 1) to relieve pain by
immobilizing the iris; 2) to prevent adhesion of the iris to the
anterior lens capsule (posterior synechia), which can lead to iris
bombe and elevated intraocular pressure (IOP); and 3) to stabilize
the blood-aqueous barrier and help prevent further protein leakage
(flare).
[0035] The steroid hormone dexamethasone
[9-fluoro-11.beta.,17,21-trihydroxy-16.alpha.-methylpregna-1,4-diene-3,20-
-dione] belongs to the class of glucocorticoid steroid hormones
that can suppress the inflammatory response to a variety of agents
of mechanical/surgical, chemical, and/or immunological nature. The
anti-inflammatory activity of dexamethasone administered
systemically is about six to ten times greater than that of
prednisone or prednisolone and about 30 to 40 times more potent
than cortisone, Dexamethasone (DEX) has been shown to be effective
in suppressing and/or blocking inflammation in the eye in human
clinical studies and in rabbit models.
[0036] DEX is currently available in multiple commercial forms,
which include some prodrugs: dexamethasone base (alcohol), acetate
or disodium phosphate. DEX and its prodrugs can be administered
orally, topically, by intravenous or intramuscular injection or
inhaled. In ophthalmology, DEX disodium phosphate (Decadron.RTM.,
Merck & Co.) 0.1% solution has been used. Although 0.1%
solutions are widely used for ocular treatments, the doses and
durations of treatment vary considerably across individual
patients. DEX phosphate 0.1% solutions do not readily penetrate the
intact cornea. Selection of the DEX dose for treatment of ocular
inflammation is based mostly on clinical effectiveness data, with
supportive information from pharmacology and pharmacokinetic
studies.
[0037] Patients with anterior uveitis are typically treated
aggressively with a potent topical steroid agent during the initial
stage of inflammation, and re-evaluated at frequent intervals, with
a schedule of steroid tapering dictated by clinical response, as
determined by one of skill in the art. Thus, in practice, the
principal means of regulating the dosage of a topically applied
corticosteroid is to vary the frequency with which the medication
is instilled. When a maximal effect is desired, topical steroids
are administered hourly, or even more frequently. In very severe
cases of anterior uveitis, prednisolone acetate 1% or dexamethasone
alcohol 0.1% may be required hourly around the clock, together with
periocular and/or oral corticosteroids as adjunctive therapy.
Compliance with these regimens is often a consideration when
treatment effectiveness is being evaluated. Most treatment failures
with topical steroids are believed to be due to poor patient
compliance, inadequate dosing, or abrupt or rapid tapering
schedules.
[0038] In addition to uveitis, other conditions suitable for
treatment by iontophoresing dexamethasone into the eye include, for
example, dry eye, diabetic macular edema, age-related macular
degeneration, and other inflammatory eye conditions.
Ocular Iontophoresis Apparatus
[0039] Devices for delivering, for example, dexamethasone and
suitable formulations thereof, have been described (U.S. Pat. No.
6,154,671; U.S. Pub. App. No. 2006/0142706; U.S. Pub. App. No.
2005/0245856; WO 2006/072887; and U.S. Pub. App. No. 2007/0123814;
the contents of each of which are herein incorporated by reference
in their entireties).
[0040] In a preferred embodiment, an iontophoretic device, with a
topical applicator, is used to perform ocular iontophoresis. An
example of such a device is described below, however, one of skill
in the art would appreciate that other devices suitable for ocular
iontophoresis are useful for using the formulations and methods of
the present invention.
[0041] The iontophoresis applicator is annular in shape, and
designed to fit over the sclera of the eye, to allow direct
delivery of drug to the eye. The inner diameter of the applicator
is the same diameter as the average cornea to help facilitate the
centering of the device on the eye. The active contact surface
between the eye and the applicator consists of soft polyurethane
hydrophilic foam; this foam serves as the reservoir for the
dexamethasone phosphate solution to be delivered during treatment.
The electrode is inert and annular in shape to match the shape and
size of the foam.
[0042] The foam reservoir can be made of hydrophilic foam that
facilitates the reservoir filling process and helps eliminate air
bubbles in the system. The distal part of the applicator and the
foam reservoir of the applicator function as the interface between
the eye and the device. The dimensions of these components are
specifically designed to fit over the sclera, 1 mm from the limbus.
The inside diameter of the applicator serves as a viewing port to
aid in placement and centration of the applicator.
[0043] The dimensioning and shape of the reservoir is such that the
molecules to be delivered are distributed in a homogeneous manner
and on the large ocular area so as to minimize their action per
area unit, and thus to preserve the superficial ocular tissue from
too much stress, and also to deliver the produce precisely in
targeted intraocular tissues with avoiding systemic absorption. A
larger surface area allows a lower electric field resident time on
the eyeball and limits the current density on it.
[0044] The application, surface of the reservoir can be chosen for
covering a target area. It is thus not only the surface area, but
also the shape of the reservoir that can be adapted for reaching
the purpose of maximizing a homogeneous distribution of active
substances. The reservoir of the device, for example, can be
adapted to administer the active substances via at least a part of
the cornea alone, or at least a part of the sclera and at least a
part of the cornea, or at least a part of the sclera alone. In some
embodiments, the application surface of the reservoir is annular
and capable of extending around the optical axis of the
eyeball.
[0045] The medium housed in the reservoir extends from a surface of
the eyeball. The medium can include, for example, a natural or
synthetic gel member, a natural or synthetic foam that is
geometrically and compositionally compatible for ocular
applications for receiving the active substances in solution, or a
single solution. Electrically-conductive media, such as, for
example, water or hydrogel, can also be placed in the reservoir to
guide and conduct the electric field through the reservoir to the
surface of the eyeball. The medium can also contain supplemental
agents, such as, for example, electrolytes, stability additives,
medicament preserving additives, pH regulating buffers, PEGylating
agents and any other agent that, when associated, increase the
half-life and/or bioavailability.
[0046] The applicator electrode can be made of, for example, a flat
film with a silver coating on one surface and a conductive carbon
coating on the other surface. The silver coated surface of the
electrode is in contact with the source connector pin and helps
disperse the current evenly around the electrode. The conductive
carbon is in contact with the drug product in the foam reservoir
and serves to transfer the current to the drug product; the carbon
surface is inert and does not react with the drug product. The
electrode is, for example, about 6 mm away from the surface of the
eye to minimize any potential thermal effects from the applicator
electrode.
[0047] A passive or return electrode can be placed on a portion of
the body (to "loop" current through the body), for example on an
ear, the forehead or a cheek. As with the active electrode, the
passive electrode can include an anode or a cathode depending upon
whether the active substances are cationic or anionic. The return
electrode can be very similar to, for example, a standard TENS type
electrode. It consists of multiple layers of conductive materials
that are designed to allow the current to pass out from the patient
and back to the constant current generator. The electrode is flat,
rectangular in shape and sized to fit on the forehead. A
commercially-available conductive gel adhesive secures the
electrode to the patient.
[0048] The active, or applicator electrode, can be advantageously
arranged, in operation, to present current density of about 10
mA/cm.sup.2 or less, and to be polarized for about ten minutes or
less. In some embodiments, the device includes a protective layer
optionally formed on a surface of the active electrode so as to
protect it or to protect the inactive substances from metallic
contaminants, as described in FR 04/04673, the contents of which
are herein incorporated by reference in its entirety. The device
can be advantageously arranged in such a manner that the distance
between the active electrode and the ocular surface is chosen to
prevent any damage of the ocular tissue due to the electric field.
A distance from the ocular surface to the active electrode can be
chosen, for example, to be at least about 4 mm.
[0049] The transfer system can be comprised of a syringe and spike,
serving to transfer the drug product from a standard vial to the
foam reservoir of the applicator. The spike, which can be
fabricated from plastic, has a sharp end that is used to perforate
the top seal of the glass vial containing the DEX phosphate
ophthalmic solution. The distal end of the transfer system mates
with the applicator to facilitate the transfer of drug product from
the syringe to the applicator reservoir. Alternatively, the
transfer system can be provided as a sterile, single-use,
disposable product.
[0050] The iontophoresis generator can be a hand held battery
operated device designed to deliver a constant current to the
applicator in the predetermined range used for iontophoretic
delivery of the drug product. The generator automatically ramps up
the current at a predetermined rate to the desired current, as
determined by one of skill in the art.
Iontophoresis Parameters
[0051] Several interdependent factors influence the overall
efficacy and safety of a particular topical steroid preparation in
the treatment of ocular inflammatory disease. These include the
ability of a topical steroid to penetrate through the cornea,
sclera or blood-ocular barrier, relative anti-inflammatory potency
and duration of action, the dose and frequency of administration
and the adverse event profile. Given the medical imperative to
intervene early and aggressively in eyes with, for example,
anterior uveitis, and the high frequency of administration required
to achieve adequate therapeutic levels of steroid in the anterior
chamber, alternative methods of steroid delivery into the eye are
of clinical interest.
[0052] Described herein are pertinent solution parameters that
produce a DEX sodium phosphate formulation effective for delivery
by ocular iontophoresis. Both the upper and lower effectiveness
limits of each parameter are described, and one of skill in the art
would know how to adjust these parameters to produce, for example,
a controlled rate of drug delivery. The parameters considered are
as follows: [0053] 1. pH This is measured by a calibrated pH meter.
Various pH ranges are obtained by pH adjustment with acid or base
using various buffering systems including, for example, phosphate
buffers. [0054] 2. Conductivity This is measured by a calibrated
pH/conductivity meter. Various conductivity ranges are obtained by
altering the salt (e.g., NaCl, KCl, etc.) concentration. [0055] 3.
Osmolarity. This is measured by a calibrated osmometer. Various
osmolality ranges are obtained by addition of, for example,
mannitol. [0056] 4. Ionic Strength Various ionic strengths are
obtained by the addition of various ionic compounds (e.g. NaCl,
KCl, CaCl.sub.2, MgCl.sub.2, etc.). Ionic strength is determined by
using the following calculation:
[0056] I = 1 2 C i z i 2 ##EQU00001## where I is ionic strength,
C.sub.i is the concentration of the i.sup.th molecule, and z.sub.i
is the charge of the i.sup.th molecule. [0057] 5. Viscosity This is
measured by a calibrated viscometer. Various viscosities are
obtained by the addition of, for example, various polyethylene
glycol species (PEG's).
[0058] Other parameters that are considered in optimizing delivery
of DEX include, for example, use of inert versus active electrodes,
choice of buffer system, choice of excipient (possibly required for
adjusting osmolarity), compound charge (e.g., pK.sub.a and pI),
compound solubility, API concentration, compound stability, choice
of drug stabilizer, co-solvents and emulsions.
[0059] The applicator used to deliver the drug formulation utilizes
an electrode (inert or active) that stimulates the electrolysis of
water to produce ions (hydroxide or hydronium), which are required
to deliver charged molecules. An anion at physiological pH,
cathodic delivery (generating hydroxide ions), therefore, is
required to deliver DEX phosphate. This process generates hydroxide
ions that promote movement of the anionic DEX phosphate into the
ocular tissues, and concurrently raises the pH of the drug
solution. The drug product solution offers sufficient buffering
capacity to accommodate all hydroxide ions generated with dosing.
The unique physicochemical properties of DEX phosphate,
specifically the two pKa's of DEX phosphate, allow the production
of a highly water soluble formulation with significant buffering
capacity.
[0060] An aqueous formulation of DEX would not be suitable for
ocular iontophoresis because DEX lacks a charged group and has very
limited aqueous solubility (0.1 mg/mL). These two shortcomings are
overcome by utilizing the prodrug of dexamethasone, e.g.,
dexamethasone phosphate, which offers an additional advantage,
internal buffering capacity. The finished drag product intended for
iontophoretic delivery in patients with anterior uveitis is an
aqueous solution of DEX phosphate (at a concentration of about, for
example, 40 mg/mL, between about 25 and 50 mg/mL; and between about
10 and 100 mg/mL) produced by methods known in the art (e.g., by
suspending the API in water for injection and then adjusting the pH
of the solution to 5.7 with sodium hydroxide). As the solution
becomes less acidic, DEX phosphate dissolves, resulting in a clear
solution. In one embodiment, the finished drug product can be
filter sterilized and aseptically filled into USP Type 1 glass
vials. The vials can be closed with, for example, bromobutyl rubber
stoppers and an aluminum overseal. The vials of finished drug
product can be stored at about 2-8.degree. C., protected from
light. The product can be warmed to room temperature prior to
administration.
EXEMPLIFICATION
Example 1
Conditions for Ocular Iontophoresis of DEX
[0061] In vitro testing was performed at .+-.3 mA using a 10 mg/mL
solution in 100 mM sodium citrate at pH.about.5.66. Approximately
1% transferred to receptor using cathodic delivery.
[0062] In vitro testing was performed using four different
concentrations of sodium citrate buffer to examine the effect of
reducing the number of competing ions on transport efficiency of
DEX. Decreasing the amount of sodium citrate increased DEX flux
(see FIGS. 1 and 2).
[0063] Other conditions are varied including, for example,
eliminating the pH change from the lower concentrations of sodium
citrate solutions and using various non-charged excipients to
modulate the donor solution osmolarity.
Example 2
DEX Electrotransport Across Rabbit Sclera with an Inert
Electrode
[0064] Described herein is a study of ocular iontophoresis:
specifically, a characterization of the barrier's permselectivity
and to establish structure-transport relationships. The
electrotransport of model anionic compounds (DEX phosphate) has
been examined across rabbit sclera. DEX phosphate, a widely used
ophthalmic drug, was chosen as model negatively-charged agent. It
is a further goal to examine whether drug flux across the sclera
can be optimized using the same strategies that have proven
successful for skin and, in particular, to confirm that linear
"flux-current" relationships also apply at the higher current
densities used in ocular delivery.
Methods
[0065] All transscleral iontophoresis studies were performed in
side-by-side diffusion cells (transport area=0.2 cm.sup.2, volume=4
mL) with excised rabbit sclera. The tissue was freed from the
conjuctiva, extraocular muscles and retina. The sclera was clamped
between the two half-cells, with the conjunctival side facing the
drug solution. Pt or Ag/AgCl electrodes were used to deliver the
constant current, which was provided by a power supply. Each
experiment was performed in at least quadruplicate. Appropriate
passive, no-current controls were performed.
[0066] Cathodal trans-scleral iontophoresis of DEX phosphate was
conducted at 0.5, 1, and 2 mA for 2 hours. The donor solution was
0.4% w/v DEX phosphate in water. The receptor solution was again
phosphate-buffered saline at pH 7.4. A limited number of
experiments were also carried out, in this instance, using sheep
sclera. The data from these studies were indistinguishable from
those obtained using the corresponding rabbit membranes. Samples of
the receptor phase were assayed for dexamethasone by HPLC.
Results
[0067] Iontophoretic delivery of dexamethasone phosphate across the
sclera was facile, and the fluxes achieved after one hour were
directly proportional to the applied current (FIG. 4).
Example 3
[0068] Testing was performed using dexamethasone and the two
prodrugs, DEX sodium phosphate and DEX phosphate. Based on
comparative pharmacokinetic data, DEX phosphate was selected as a
suitable prodrug for iontophoretic delivery. Since dexamethasone is
considered to be the active moiety of the prodrugs, this section
describes the pharmacology of dexamethasone.
[0069] Published literature supports the pharmacologic effect of
dexamethasone, particularly in models of ocular inflammation. A
number of experiments have been reported that characterize the
pharmacologic effects of dexamethasone, both in vitro and in vivo.
Often prodrugs of dexamethasone are used in these pharmacology
studies, and it is assumed that the conversion of these prodrugs to
dexamethasone occurs relatively rapidly and completely. These
combined data support that dexamethasone efficiently and
effectively inhibits inflammation. The in vitro and in vivo studies
leading to these findings are described herein.
[0070] Described herein are formulations and methods for delivering
DEX to a subject. The iontophoretic delivery of therapeutic agents
into the eye is of interest as a means of non-invasively achieving
higher drug levels inside the eye by promoting the movement of
charged substances (drug products) across biological membranes by
applying a low electrical current forming an electrical field. The
electric field causes electrorepulsions between the newly formed
ions and the drug product, which propels the drug product into
ocular tissue. The iontophoretic delivery of an aqueous dosing
solution of dexamethasone phosphate, an anion at physiological pH,
requires cathodic electrolysis with, for example, an inert
electrode. This process generates hydroxide ions that promote
movement of the anionic dexamethasone phosphate into the ocular
tissues, while concurrently raising the pH of the drug product
solution. The unique physicochemical properties of DEX phosphate,
specifically the two pKa's (1.9 and 6.4) of dexamethasone
phosphate, however, allow the production of a highly water soluble
formulation (40 mg/mL) with significant buffering capacity (initial
pH 5.7-5.8) to accommodate hydroxide ions generated.
[0071] The biophysical and biological mechanisms responsible for
the tissue penetration of active products are not well understood.
Most transdermal models are based on the modified Nernst-Planck
equation. According to this equation, total flux is the sum of
active and passive transport mechanisms: passive diffusion,
electrorepulsion, and electroosmosis flux, which are summarized in
the Nernst-Planck equation below:
Flux.sub.total=Flux.sub.passive+Flux.sub.electric+Flux.sub.osmotic
FLUX.sub.TOTAL=-D/(DC/DX)+(DZVFC.sub.i)/(KT).+-.CU
where: D=Diffusion coefficient (characteristic of the biological
membrane) dc/dx=Concentration gradient z=valence V=Electrical field
F=Faraday's constant K=Boltzmann's constant
T=Temperature
[0072] C.sub.i=Ionized drug concentration C=Drug concentration
u=convective flow of water
In Vitro Testing
[0073] In vitro experiments were conducted to evaluate drug product
stability under iontophoresis. These experiments employed Ussing
chambers, using a wide range of iontophoretic doses (e.g., up to
120 mAmin). Compound concentrations were measured using HPLC
analysis coupled to a UV detector, and standard curves were
generated by testing solutions at various concentrations.
[0074] The donor and receiving chambers are connected by a ball and
socket joint with freshly harvested rabbit scleral tissue
compressed into the joint (using the cell clamp and tension knob).
A 40 mg/mL aqueous DEX phosphate solution (pH adjusted to 5.7 with
1.0 N aqueous sodium hydroxide) was placed in the donor chamber.
The receiving chamber was filled with 0.9% saline. After standing
at room temperature for up to 120 minutes, samples were removed
from the donor and accepting chambers to appraise DEX phosphate and
dexamethasone concentrations. Next, inert electrodes were placed
into the donor and acceptor chambers. The connecting wires were
configured at the generator in order to produce cathodic
iontophoresis. At a variety of time points, aliquots were removed
from the donor and receiving chambers in order to quantify
dexamethasone, dexamethasone phosphate, and any impurities. On
average, little or no dexamethasone/dexamethasone phosphate was
transferred passively (without current) and up to 5% of the
material was fluxed across the membrane (with current). For up to
120 minutes, no significant impurities were detectable in the donor
or receiving chambers. A linear proportional drug product
concentration relationship was obtained.
[0075] Approximately 95% of the original DEX phosphate
concentration was present in the donor chamber. The residual
solution contained one quantifiable material (concentration
>5%). The quantifiable material represented <5% of the total
area under the curve based on HPLC (UV detection), which was
dexamethasone (based on comparison to a reference standard). No
other quantifiable materials were detected.
[0076] The receptor chamber contained <5% of the total DEX
phosphate that was present at the beginning of the study in the
donor chamber. Within the receptor chamber solution, 95% of the
material was dexamethasone phosphate. The balance of the material,
which represented <5% of the total area under the curve based on
HPLC (UV detection), was dexamethasone (based on comparison to a
reference standard). No other quantifiable materials were
detected.
Absorption and Ocular Tissue Concentrations
[0077] The ocular tissue concentrations of DEX phosphate (the
prodrug) and dexamethasone (active moiety) two hours after topical
administration, subconjunctival injection and constant coulomb
iontophoresis delivery of DEX disodium phosphate were evaluated in
42 male and female Fauve de Bourgogne pigmented rabbits (6/group).
The seven treatments were single doses administered to the right
eye as follows; [0078] Group 1: Iontophoretic device placed on
right eye loaded with Sterile Water for Injection; no current was
applied; [0079] Group 2: Iontophoretic delivery of DEX disodium
phosphate with iontophoretic device at 2.5 mA for 5 minutes (device
loaded with 0.5 mL of DEX disodium phosphate 10 mg/mL solution,
Sigma) [0080] Group 3: Iontophoretic delivery of DEX disodium
phosphate with iontophoretic device 2.5 mA for 5 minutes (device
loaded with 0.5 mL of DEX disodium phosphate 40 mg/mL solution,
Sigma) [0081] Group 4: Iontophoretic delivery of DEX disodium
phosphate with iontophoretic device 2.5 mA for 5 minutes (device
loaded with 0.5 mL of DEX disodium phosphate 10 mg/mL solution,
Abraxis) [0082] Group 5: Subconjunctival injection of DEX disodium
phosphate (0.75 mL of DEX disodium phosphate 40 mg/mL solution,
Sigma) [0083] Group 6; Subconjunctival Injection of DEX disodium
phosphate (0.75 mL of DEX disodium phosphate 10 mg/mL solution,
Abraxis) [0084] Group 7: Topical instillation of DEX disodium
phosphate (0.05 mL of DEX disodium phosphate 10 mg/mL solution,
Abraxis)
[0085] Ocular tissues and plasma collected 2 hours post dosing were
analyzed for DEX phosphate and dexamethasone concentration. Samples
were analyzed by an ELISA or HPLC-MS/MS method. Iontophoresis or
subconjunctival administration provided higher ocular tissue
concentrations of DEX phosphate and dexamethasone compared to
topical instillation. Subconjunctival administration resulted in
very high concentrations of DEX phosphate and dexamethasone in
conjunctiva and choroid tissue. Other ocular tissues had high
levels of dexamethasone and DEX phosphate. Aqueous humor
concentrations correlated with iris-ciliary body tissue
concentrations two hours post dose for all dosing modalities
investigated. Vitreous humor concentrations correlated with retina
concentrations two hours post dose of all dosing modalities.
Systemic exposure at two hours post dosing was very low (<100
ng/mL) for iontophoresis and topical administration of DEX disodium
phosphate. Subconjunctival administration resulted in low but
measurable plasma levels (<4000 ng/mL) at two hours post
dose.
[0086] The pharmacokinetics of dexamethasone and DEX phosphate
after iontophoretic administration by the iontophoretic device were
characterized in 24 female New Zealand White rabbits. Dexamethasone
phosphate (60 mg/mL) was administered iontophoretically at 3 mA for
5 minutes as a single dose to both eyes or DEX phosphate 40 mg/mL
was iontophoretically delivered once daily for 3 consecutive days
to both eyes. Ocular tissues and plasma were analyzed for DEX
phosphate and dexamethasone concentrations by an HPLC-MS/MS method
in serial samples collected post dosing. Dose proportional
increases in plasma and ocular tissue concentrations and exposure
measures of dexamethasone were observed after iontophoretic
administration of the 40 mg/mL versus 60 mg/mL DEX phosphate
solution (Table 1).
TABLE-US-00001 TABLE 1 Ocular Single Dose-40 mg/mL Dex P Single
Dose-60 mg/mL Dex P Tissue or Dex AUC.sub.0-6 h Dex AUC.sub.0-24 h
Dex AUC.sub.0-6 h Dex AUC.sub.0-24 h Plasma (.mu.g h/g or .mu.g
h/mL) (.mu.g h/g or .mu.g h/mL) (.mu.g h/g or .mu.g h/mL) (.mu.g
h/g or .mu.g h/mL) Aqueous Humor 56.5 73.8 123 132 Vitreous 1.5 2.2
2.3 3.0 Choroid 24.9 35.9 49.5 66.7 Plasma 1.6 3.3 3.7 6.6 Ocular
Single Dose-40 mg/mL Dex P Single Dose-60 mg/mL Dex P Tissue or Dex
C.sub.max Dex T.sub.max Dex C.sub.max Dex T.sub.max Plasma (.mu.g/g
or .mu.g/mL) (hours) (.mu.g/g or .mu.g/mL) (hours) Aqueous Humor
16.6 2 40.5 2 Vitreous 0.360 2 0.657 2 Choroid 7.43 0.25 12.5 0.25
Plasma 0.342 0.25 0.997 2 Dex P = Dexamethasone Phosphate; Dex =
Dexamethasone; AUC = area under the concentration-time curve over a
specified time period; Tmax = time to maximum concentration; Cmax =
maximum concentration
[0087] Peak dexamethasone concentrations in ocular tissues or
plasma occurred relatively rapidly, within two hours post
iontophoretic dosing. Significant ocular tissue concentrations of
dexamethasone occurred up to six hours post iontophoretic dosing.
In general, dexamethasone and DEX phosphate were nearly completely
cleared from plasma and ocular tissues within 48 hours after
iontophoretic administration. The choroid tissue concentration did
not decline as rapidly as that of the other ocular tissues. While
choroid tissue concentrations of dexamethasone and DEX phosphate
were measurable at 48 hours post iontophoretic delivery of DEX
phosphate, they were generally less than 10% of peak choroid
concentrations. Compared to peak concentrations of dexamethasone
and DEX phosphate, plasma and ocular tissue concentrations were
relatively low at 24 hours post iontophoretic administration. At 24
hours post dosing, ocular tissues and plasma concentrations were
less than 10% of peak dexamethasone or DEX phosphate concentrations
in all tissues except for the choroid. Dexamethasone and DEX
phosphate concentrations in aqueous humor correlated with
concentrations in the iris-ciliary body.
[0088] The effect of pH and chemical form of DEX phosphate on
dexamethasone and DEX phosphate plasma and ocular tissue
concentrations after delivery by constant coulomb iontophoresis was
evaluated in 6 female New Zealand White rabbits. The treatments
included DEX phosphate 40 mg/mL pH 5.8 made from DEX phosphate free
acid, DEX phosphate 40 mg/mL pH 5.8 made from DEX phosphate
disodium salt, and DEX phosphate 40 mg/mL pH 17.0 made from DEX
phosphate disodium salt. A single iontophoretic dose of 2.5 mA for
5 minutes was administered. Dexamethasone concentrations in plasma
and ocular tissues were higher after iontophoretic delivery of DEX
phosphate formulations prepared from DEX phosphate free acid when
compared to formulations prepared from DEX phosphate disodium
salt.
TABLE-US-00002 TABLE 2 EVALUATION OF RABBITS/FAUVE DE STERILE WATER
IN DEVICE; DEX-P AND DEX TOPICAL, BOURGOGNE/42 M&F NO CURRENT;
CONCENTRATIONS AT T = 2 SUBCONJUNCTIVAL 6/GROUP SIGMA DEX DISODIUM
P HOURS DETERMINED IN INJECTION AND 10 MG/ML AND 40 MG/ML OCULAR
TISSUES AND PLASMA CONSTANT COULOMB IONTOPHORETIC DOSE OF
IONTOPHORESIS OR IONTOPHORESIS 2.5 MA FOR 5 MIN; SUBCONJ. DOSING
PROVIDE DELIVERY OF ABRAXIS, DEX DISODIUM P HIGHER TISSUE
DEXAMETHASONE 10 MG/ML, IONTOPHORESIS CONCENTRATIONS OF DEX-P +
DISODIUM PHOSPHATE 2.5 MA FOR 5 MIN; DEX IN ALL TISSUE IN FAUVE DE
ABRAXIS DEX DISODIUM P COMPARED TO TOPICAL BOURGOGNE RABBITS 10
MG/ML, TOPICAL; INSTILLATION. ABRAXIS DEX DISODIUM P SUBCONJUNC.
DOSING 10 MG/ML AND RESULTED IN VERY HIGH SIGMA DEX DISODIUM P
CONCENTRATIONS OF DEX-P 40 MG/ML AND DEX IN CONJUNCTIVA
SUBCONJUNCTIVAL AND CHOROID TISSUE. INJECTION; AQUEOUS HUMOR SINGLE
DOSE TO RIGHT CONCENTRATIONS EYE. CORRELATE WITH IRIS-CILIARY BODY
TISSUE CONCENTRATIONS 2 H POST DOSE FOR ALL TESTED DOSING
MODALITIES. VITREOUS HUMOR CONCENTRATIONS CORRELATE WITH RETINA
CONCENTRATIONS 2 H POST DOSE OF ALL TESTED MODALITIES. SYSTEMIC
EXPOSURE IS VERY LOW FOR IONTOPHORESIS AND TOPICAL DOSES.
SUBCONJUNC. DOSING RESULTED IN LOW BUT MEASURABLE PLASMA LEVELS AT
2 H. EVALUATION OF THE RABBITS/NEW DEX-P 40 MG/ML AND DOSE
PROPORTIONAL PK CURVE OF ZEALAND WHITE/ 60 MG/ML INCREASES IN
PLASMA AND DEXAMETHASONE 24 F DOSE: 3 MA FOR 5 MIN OCULAR TISSUE
PHOSPHATE SINGLE DOSE OR ONCE A CONCENTRATIONS AND ADMINISTERED BY
DAY FOR 3 CONSECUTIVE EXPOSURES WERE OBSERVED CONSTANT COULOMB DAYS
TO BOTH EYES. AFTER IONTOPHORETIC IONTOPHORESIS USING
ADMINISTRATION OF THE 40 THE EYEGATE II MG/ML VERSUS 60 MG/ML
DEVICE IN NEW DEXAMETHASONE ZEALAND RABBITS PHOSPHATE SOLUTION. DEX
AND DEX-P WERE NEARLY COMPLETELY CLEARED FROM PLASMA AND OCULAR
TISSUES 48 H AFTER IONTOPHORETIC ADMINISTRATION. DEX AND DEX-P
CONCENTRATIONS WERE VERY LOW AFTER 24 H IN PLASMA AND OCULAR
TISSUES. DEX CONCENTRATIONS IN AQUEOUS HUMOR CORRELATE WITH
CONCENTRATIONS IN IRIS-CILIARY BODY TISSUE. EFFECT OF PH ON
RABBITS/NEW DEX-P 40 MG/ML PH 5.8 DEX CONCENTRATIONS IN DELIVERY OF
ZEALAND WHITE/6 F FROM DEX-P FREE ACID, PLASMA AND OCULAR TISSUES
DEXAMETHASONE DEX-P 40 MG/ML PH 5.8 WERE HIGHER AFTER PHOSPHATE BY
FROM DEX-P DISODIUM IONTOPHORETIC DELIVERY OF CONSTANT COULOMB SALT
DEX-P FORMULATIONS IONTOPHORESIS USING DEX-P 40 MG/ML PH 7.0
PREPARED FROM DEX-P FREE EYEGATE II DEVICE IN FROM DEX-P DISODIUM
ACID WHEN COMPARED TO NEW ZEALAND RABBITS SALT FORMULATIONS
PREPARED DOSE: 2.5 MA FOR 5 MIN FROM DEX-P DISODIUM SALT. SINGLE
DOSE.
Example 4
[0089] Additional parameters for iontophoretic delivery are varied.
Conditions include, for example, the following: [0090] Use of
active or inert electrodes; [0091] Varying osmolarity (typically
from about 200-240 mOsm/L); [0092] Varying the starting pH from
about 2.5 to about 6.5 (typically from about 5.7-5.8); [0093]
Buffer: none or use of buffering systems known in the art; [0094]
Choice of excipient; [0095] Drug product concentration (typically
about 40 mg/mL); [0096] Choice of drug product stabilizer: none (in
cases where a stabilizer can be an irritant), or other stabilizer
known in the art (see below); [0097] Varying co-solvents; and/or
[0098] Varying emulsions
[0099] Other conditions are also varied to optimize iontophoretic
delivery, for example, osmolarity can range from, for example,
about 200-600 mOsm/L, from about 250-500 mOsm/L, from about 300-400
mOsm/L, or from about 200-550 mOsm/L. One of skill in the art would
know how to vary osmolarity to achieve optimized results.
[0100] The starting pH, typically about 2.5-7.5 can also be varied
within this range to achieve optimized results, for example, a
range of about 3.0-6.5, about 3.5-6.0, about 4.0-6.0, or about
5.0-6.0 can be used.
[0101] One of skill in the art would know how to vary the buffer
system used to achieve a particular pH range. Exemplary buffer
systems include, for example, lithium, sodium, potassium acetate,
citrate, tartrate, etc.
[0102] One of skill in the art would know how to vary the choice of
excipient, which could be used to adjust osmolarity, for example,
by using non-charged sugars.
[0103] One of skill in the art will recognize that conditions will
vary based on parameters such as, for example, the pK.sub.a of the
compound to be delivered, the compound solubility, the
concentration of the compound to be delivered (for example, for
dexamethasone, from about 1-100 mg/mL, about 5-80 mg/mL, about
10-50 mg/mL, or from about 20-50 mg/mL).
[0104] Examples of conditions include, for example, the
following
A.
[0105] Electrode: Inert [0106] Device: Eye Gate II applicator
[0107] Current pole: cathodic [0108] Current range: 0.01-10 mA
[0109] Dose time: 1 second-10 minutes [0110] Total iontophoretic
dose (current.times.time in minutes): 0.01-100 mAmin
B.
[0110] [0111] Electrode: Inert [0112] Device: Eye Gate II
applicator [0113] Current pole: cathodic [0114] Current range:
0.1-10 mA [0115] Dose time: 30 seconds-10 minutes [0116] Total
iontophoretic dose (current.times.time in minutes): 0.1-100
mAmin
C.
[0116] [0117] Electrode: Inert [0118] Device: Eye Gate II
applicator [0119] Current pole: cathodic [0120] Current range:
0.5-10 mA [0121] Dose time: 30 seconds-5 minutes [0122] Total
iontophoretic dose (current.times.time in minutes): 0.5-50 mAmin
Preferred DEX formulations include, for example:
A.
[0122] [0123] Electrode: Active and inert [0124] Osmolarity:
200-600 mOsm/L [0125] Starting pH: 3.5-8.5 [0126] Vehicle: water
for injection [0127] Stabilizers: benzyl alcohol, benzalkonium
chloride, EDTA, Citrate, Bisulfite, Metabisulfite [0128]
Concentration: 1-100 mg/mL [0129] Storage: aerobic and anerobic
B.
[0129] [0130] Electrode: Inert [0131] Osmolarity: 200-400 mOsm/L
[0132] Starting pH: 5.4-6.4 [0133] Vehicle: water for injection
[0134] Stabilizers: 0.1% benzyl alcohol, 0.01% benzalkonium
chloride, 0.1% EDTA, 0.65% Citrate, 0.1% Bisulfite, 0.1%
Metabisulfite [0135] Buffer: lithium, sodium, potassium acetate,
citrate, tartrate, etc [0136] Choice of excipient: non-charged
sugars [0137] Concentration: 1-60 mg/mL [0138] Storage: aerobic and
anerobic
C.
[0138] [0139] Electrode: Inert [0140] Osmolarity: 200-300 mOsm/L
[0141] Starting pH: 5.7-6.1 [0142] Vehicle: water for injection
[0143] Concentration: 40 mg/mL
Example 5
Single-Dose Treatment with Dexamethasone Phosphate Resolves
Concanavalin A-Induced Dry Eye in Rabbits
[0144] Current treatment options for dry eye include long-term
treatment with artificial tears, topical corticosteroids such as
prednisolone, and punctal plugs, which may result in immediate
effects. These treatments can be combined with topical cyclosporine
A (Restasis.RTM.), which can take up to six months to improve
symptoms. Daily, multiple doses of topical corticosteroids are
required for effectiveness. Long-term dexamethasone treatment,
however, can have negative effects such as elevated intraocular
pressure. The efficacy of a single iontophoretically-delivered
dexamethasone phosphate (Dex-P) in rabbits with concanavalin
A-induced dry eye was assessed.
Induction of Dry Eye in Rabbits
[0145] 300 .mu.g of Concanavalin A (Sigma) in 30 mL of
phosphate-buffered saline (PBS) or PBS alone were injected into the
lacrimal glands of white New Zealand rabbits to induce inflammation
leading to dry eye symptoms, which is a well-established model of
dry eye syndrome.
Iontophoretic Drug Delivery
[0146] 48 hours after lacrimal gland injection, rabbits were given
a single 15 mA-min (-3.0 mA for 5 min) iontophoretic dose of
dexamethasone phosphate (40 mg/mL) or phosphate-buffered saline
using the Eye Gate II device (Eye Gate Pharmaceuticals, Inc) (FIG.
5). The animals were assigned to the following treatment
groups:
Group 1: Con A injection on Day 0, Treatment with Dex-P on Day 2
Group 2: Con A injection on Day 0, Treatment with PBS on Day 2
Group 3: PBS injection on Day 0, Treatment with PBS on Day 2 Group
4: PBS injection on Day 0 with no subsequent treatment
Clinical Observations
[0147] Animals were observed daily following Con A injection for
signs of ocular inflammation. Tear flow was measured using Schirmer
strips in all groups on Days 0, 1, 2, 4, 7, and 8 after Con A
injection (FIG. 6). Signs of ocular surface damage were assessed on
Days 0, 2, 4, and 8 using fluorescein staining and slit-lamp
microscopy (FIGS. 7 and 8), Staining was scored from 0 to 2 for
superior, central, and Inferior cornea for a total possible score
of 6.
Cytokine Assays
[0148] Animals were euthanized on Day 4 or Day 8 following Con A
injection. Upon sacrifice, the cornea and lacrimal gland were
removed and snap frozen in liquid nitrogen followed by storage at
-80.degree. C. All samples were homogenized by hand in a
ground-glass homogenizer in 0.5 mL of PBS+10 mM EDTA.
Interleukin-1-beta (IL-1.beta.), FIG. 9, and transforming growth
factor beta-1 (TGF-.beta.1), FIG. 10, were measured in lacrimal
gland and corneal extracts using human IL-1.beta. or TGF-.beta.1
ELISA kit (R&D Systems DuoSet ELISA development system)
according to manufacturer's instructions. Results were normalized
for total protein concentration measured in the protein assay. Due
to the high homology between rabbit and human IL-1.beta. and
TGF-.beta.1, human kits are appropriate for detecting the rabbit
cytokine.
Conclusions
[0149] A single iontophoretic dose of dexamethasone phosphate
increases tear flow in rabbits and decreases the amount of ocular
surface damage compared to control groups. Reduced IL-1.beta. and
TGF-.beta.1 expression is observed in the lacrimal glands of eyes
treated with a single iontophoretic dose of dexamethasone phosphate
compared to saline treatment and control groups. No significant
elevation of inflammatory cytokines in the cornea is observed on
Day 4 and Day 8, indicating a specific inflammatory response of the
lacrimal gland. A single iontophoretic dose of corticosteroid is a
safer and more effective alternative than multiple, daily topical
doses.
Other Embodiments
[0150] Other embodiments will be evident to those of skill in the
art. It should be understood that the foregoing detailed
description is provided for clarity only and is merely exemplary.
The spirit and scope of the present invention are not limited to
the above examples, but are encompassed by the following claims.
All references cited herein are incorporated by reference in their
entireties.
* * * * *