U.S. patent application number 13/014613 was filed with the patent office on 2011-05-26 for implantable or insertable medical devices for controlled delivery of a therapeutic agent.
This patent application is currently assigned to BOSTON SCIENTIFIC SCIMED, INC.. Invention is credited to Marlene C. Schwarz.
Application Number | 20110123594 13/014613 |
Document ID | / |
Family ID | 29733835 |
Filed Date | 2011-05-26 |
United States Patent
Application |
20110123594 |
Kind Code |
A1 |
Schwarz; Marlene C. |
May 26, 2011 |
Implantable or Insertable Medical Devices For Controlled Delivery
of a Therapeutic Agent
Abstract
The present invention is directed to novel implantable or
insertable medical devices that provide controlled release of a
therapeutic agent. According to an embodiment of the present
invention, a therapeutic-agent-releasing medical device is
provided, which comprises: (a) an implantable or insertable medical
device; (b) a release layer disposed over at least a portion of the
implantable or insertable medical device; and (c) a therapeutic
agent. The release layer comprises a styrene copolymer and at least
one additional polymer. The release layer regulates the rate of
release of the therapeutic agent from the medical device upon
implantation or insertion of the device into a patient. The present
invention is also directed to methods of forming the above
implantable or insertable medical devices, methods of administering
a therapeutic agent to a patient using such devices, and methods of
modulating the release of therapeutic agent from such devices.
Inventors: |
Schwarz; Marlene C.;
(Auburndale, MA) |
Assignee: |
BOSTON SCIENTIFIC SCIMED,
INC.
Maple Grove
MN
|
Family ID: |
29733835 |
Appl. No.: |
13/014613 |
Filed: |
January 26, 2011 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11518647 |
Sep 11, 2006 |
7901702 |
|
|
13014613 |
|
|
|
|
10175334 |
Jun 19, 2002 |
7105175 |
|
|
11518647 |
|
|
|
|
Current U.S.
Class: |
424/423 ;
424/422; 514/449 |
Current CPC
Class: |
A61L 27/34 20130101;
A61L 29/085 20130101; A61L 2300/602 20130101; A61L 2300/416
20130101; A61L 29/16 20130101; A61L 31/10 20130101; A61P 9/00
20180101; A61L 27/56 20130101 |
Class at
Publication: |
424/423 ;
424/422; 514/449 |
International
Class: |
A61F 2/82 20060101
A61F002/82; A61M 31/00 20060101 A61M031/00; A61K 31/337 20060101
A61K031/337; A61P 9/00 20060101 A61P009/00 |
Claims
1-25. (canceled)
26. A method of forming the therapeutic-agent-releasing medical
device that comprises (a) an implantable or insertable medical
device; (b) a release layer disposed over at least a portion of the
implantable or insertable medical device, said release layer
comprising (i) a styrene copolymer selected from an alternating
styrene copolymer and a random styrene copolymer and (ii) an
additional polymer; and (c) a therapeutic agent, said release layer
regulating the rate of release of the therapeutic agent from the
medical device upon implantation or insertion of the device into a
patient, said method comprising: (1) providing a solution
comprising: one or more solvents, said styrene copolymer and said
additional polymer; (2) applying said solution to a surface of said
implantable or insertable medical device; and (3) removing said
solvents from said solution to form said release layer.
27. The method of claim 26, wherein said solution further comprises
said therapeutic agent.
28. The method of claim 26, wherein said solution is applied over a
therapeutic-agent-containing region that comprises said therapeutic
agent.
29. The method of claim 26, wherein said solution is applied by a
solvent spraying technique.
30. A method of releasing a therapeutic agent within a patient
comprising (1) providing a therapeutic-agent-releasing medical
device that comprises (a) an implantable or insertable medical
device; (b) a release layer disposed over at least a portion of the
implantable or insertable medical device, said release layer
comprising (i) a styrene copolymer selected from an alternating
styrene copolymer and a random styrene copolymer and (ii) an
additional polymer; and (c) a therapeutic agent, said release layer
regulating the rate of release of the therapeutic agent from the
medical device upon implantation or insertion of the device into a
patient and (2) implanting or inserting the
therapeutic-agent-releasing medical device of into a patient.
31. The method of claim 30, wherein said medical device is selected
from a catheter, a guide wire, a balloon, a filter, a stent, a
stent graft, a vascular graft, a vascular patch, a shunt, and an
intraluminal paving system.
32. The method of claim 30, wherein said medical device is inserted
into the vasculature.
33. The method of claim 32, wherein said therapeutic agent is
released in the treatment of restenosis.
34. A method of modulating a rate of release of a therapeutic agent
by a release layer that (a) is disposed over at least a portion of
an implantable or insertable medical device and (b) comprises (i) a
styrene copolymer selected from an alternating styrene copolymer
and a random styrene copolymer and (ii) an additional polymer, said
method comprising changing the composition of said release
layer.
35. The method of claim 34, wherein the rate of release is
modulated by changing the amount of styrene copolymer relative to
the amount of the additional polymer.
36. The method of claim 35, wherein the rate of release of the
therapeutic agent is increased by increasing the amount of the
styrene copolymer relative to the amount of the additional polymer,
or the rate of release of the therapeutic agent is decreased by
decreasing the amount of the styrene copolymer relative to the
amount of the additional polymer.
37. The method of claim 34, wherein the rate of release is
modulated by changing the molecular weight of the styrene
copolymer.
38. The method of claim 34, wherein the rate of release is
modulated by changing the amount of the styrene monomer relative to
the total amount of monomer within the styrene copolymer.
39-42. (canceled)
Description
STATEMENT OF RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 11/518,647, filed Sep. 11, 2006, which is a continuation
of U.S. patent application Ser. No. 10/175,334, now U.S. Pat. No.
7,105,175 issued Sep. 12, 2006, all of which are incorporated by
reference herein in their entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to implantable or insertable
medical devices for controlled delivery of one or more therapeutic
agents.
BACKGROUND OF THE INVENTION
[0003] Numerous medical devices have been developed for the
delivery of therapeutic agents to the body.
[0004] In accordance with some delivery strategies, a therapeutic
agent is provided (a) within a polymeric carrier layer and/or (b)
beneath a polymeric barrier layer that is associated with an
implantable or insertable medical device. Once the medical device
is placed at the desired location within a patient, the therapeutic
agent is released from the medical device at a rate that is
dependent upon the nature of the polymeric carrier and/or barrier
layer.
[0005] The desired release profile for the therapeutic agent is
dependent upon the particular treatment at hand, including the
specific condition being treated, the specific therapeutic agent
selected, the specific site of administration, and so forth. As a
result, there is a continuing need for polymeric layers, including
polymeric barrier layers and carrier layers, that are able to
provide a broad range of therapeutic agent release rates.
SUMMARY OF THE INVENTION
[0006] The present invention is directed to novel implantable or
insertable medical devices, which provide for release of a
therapeutic agent. According to a first aspect of the present
invention, a therapeutic-agent-releasing medical device is
provided, which comprises: (a) an implantable or insertable medical
device; (b) a release layer disposed over at least a portion of the
implantable or insertable medical device; and (c) a therapeutic
agent. The release layer comprises a styrene copolymer and an
additional polymer. The release layer regulates the rate of release
of the therapeutic agent from the medical device upon implantation
or insertion of the device into a patient. Alternating and random
styrene copolymers are preferred.
[0007] In some embodiments, the release layer is a carrier layer
that comprises the therapeutic agent. In other embodiments, the
release layer is a barrier layer disposed over a
therapeutic-agent-containing region, which comprises the
therapeutic agent.
[0008] Preferred medical devices include catheters, guide wires,
balloons, filters, stents, stent grafts, vascular grafts, vascular
patches, shunts, and intraluminal paving systems. The device can be
adapted, for example, for implantation or insertion into the
coronary vasculature, peripheral vascular system, esophagus,
trachea, colon, biliary tract, urinary tract, prostate or
brain.
[0009] Beneficial therapeutic agents for the practice of the
present invention include anti-thrombotic agents,
anti-proliferative agents, anti-inflammatory agents, anti-migratory
agents, agents affecting extracellular matrix production and
organization, antineoplastic agents, anti-mitotic agents,
anesthetic agents, anti-coagulants, vascular cell growth promoters,
vascular cell growth inhibitors, cholesterol-lowering agents,
vasodilating agents, and agents that interfere with endogenous
vasoactive mechanisms.
[0010] Preferred styrene copolymers include copolymers comprising
(a) a styrene monomer and (b) a monomer comprising a carbon-carbon
double bond. Monomers comprising a carbon-carbon double bond
include alkylene monomers (e.g., ethylene, propylene, butadiene,
butylenes, isobutylene and isoprene), vinyl monomers (e.g., vinyl
ethers, vinyl acetates, vinyl aliphatics, halogenated vinyl
compounds, vinyl pyrrolidone, acrylonitrile, vinyl alcohols, and
vinyl acrylamides), acrylate monomers or derivatives of the same
(e.g., methyl acrylate, methyl methacrylate, acrylic acid,
methacrylic acid, hydroxyethyl acrylate, hydroxyethyl methacrylate,
glyceryl acrylate, glyceryl methacrylate, acrylamide,
methacrylamide and ethacrylamide), and maleic anhydride monomers or
derivatives of the same (e.g., maleic anhydride, maleic anhydride
in a free acid form, maleic anhydride in a salt form, or maleic
anhydride in a partial ester form).
[0011] Specific styrene copolymers for the practice of the present
invention include copolymers of styrene and maleic anhydride and
copolymers of styrene and acrylonitrile.
[0012] In some embodiments, the additional polymer is blended with
the styrene copolymer in the release layer. In others, the
additional polymer is crosslinked with the styrene copolymer in the
release layer. Specific examples of additional polymers for the
practice of the present invention include elastomers such as the
following: (1) copolymers containing (a) one or more blocks of
polyisobutylene and (b) one or more blocks of polystyrene or
poly-alpha-methylstyrene, (2) copolymers containing (a) one or more
blocks of polystyrene or poly-alpha-methylstyrene and (b) one or
more polymer blocks of ethylene and butylene, and (3) poly(butyl
methacrylates).
[0013] According to another aspect of the present invention, a
method of making a therapeutic-agent-releasing medical device is
provided. The method comprises: (a) providing a solution comprising
one or more solvents, a styrene copolymer and an additional
polymer; (b) applying the solution to a surface of an implantable
or insertable medical device; and (c) removing the solvents from
the solution to form a release layer. Solvent spraying is a
preferred technique for applying the above solution.
[0014] In some embodiments, for example, where a carrier layer is
being formed, the solution further comprises the therapeutic agent.
In other embodiments, for example, where a barrier layer is being
formed, the solution is applied over a therapeutic-agent-containing
region that comprises the therapeutic agent.
[0015] According to another aspect of the present invention, a
method of modulating a rate of release of a therapeutic agent from
a release layer is provided. The release layer is disposed over at
least a portion of an implantable or insertable medical device and
comprises a styrene copolymer and an additional polymer. Release is
modulated by changing the composition of the release layer. In some
embodiments, the release rate can be modulated by changing the
amount of the styrene copolymer relative to the amount of the
additional polymer. For example, the rate of release of the
therapeutic agent can be increased in certain embodiments by
increasing the amount of the styrene copolymer relative to the
amount of the additional polymer, while the rate of release can be
decreased by decreasing the amount of the styrene copolymer
relative to the amount of the additional polymer.
[0016] In other embodiments, the release rate is modulated by
changing the molecular weight of the styrene copolymer. In still
other embodiments, the release rate is modulated by changing the
amount of the styrene monomer relative to the total amount of
monomer within the styrene copolymer.
[0017] One advantage of the present invention is that implantable
or insertable medical devices are provided, which provide for
controlled release of a therapeutic agent.
[0018] Another advantage of the present invention is that
implantable or insertable medical devices are provided, which are
able to provide therapeutic agent release over a wide variety of
time frames.
[0019] Another advantage of the present invention is that effective
strategies are provided for controlling the release profile of a
therapeutic agent from an implantable or insertable medical
device.
[0020] These and other embodiments and advantages of the present
invention will become immediately apparent to those of ordinary
skill in the art upon review of the Detailed Description and Claims
to follow.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 illustrates cumulative release of paclitaxel as a
function of time for carrier layers containing paclitaxel and (a)
poly(butyl methacrylate) homopolymer, (b)
polystyrene-polyisobutylene-polystyrene block copolymer, (c)
polystyrene-b-poly(ethylene-r-butylene)-b-polystyrene block
copolymer, (d) poly(butyl methacrylate) homopolymer blended with a
random copolymer of styrene and maleic anhydride, (e)
polystyrene-polyisobutylene-polystyrene block copolymer blended
with a random copolymer of styrene and maleic anhydride and (f)
polystyrene-b-poly(ethylene-r-butylene)-b-polystyrene block
copolymer blended with a random copolymer of styrene and maleic
anhydride.
[0022] FIGS. 2A and 2B illustrate cumulative release of paclitaxel
as a function of time for carrier layers containing paclitaxel and
(a) a polystyrene-polyisobutylene-polystyrene block copolymer, (b)
a random copolymer of styrene and maleic anhydride and (c) a
polystyrene-polyisobutylene-polystyrene block copolymer blended
with various amounts of a random copolymer of styrene and maleic
anhydride, in accordance with an embodiment of the present
invention.
[0023] FIG. 3 illustrates cumulative release of paclitaxel as a
function of time for carrier layers containing paclitaxel and (a) a
polystyrene-polyisobutylene-polystyrene block copolymer, and (b) a
polystyrene-polyisobutylene-polystyrene block copolymer blended
with various amounts of styrene-co-acrylonitrile copolymer, in
accordance with an embodiment of the present invention.
[0024] FIG. 4 illustrates cumulative release of paclitaxel as a
function of time for carrier layers containing paclitaxel and (a)
polystyrene-polyisobutylene-polystyrene block copolymer, (b)
polystyrene-polyisobutylene-polystyrene block copolymer blended
with a random copolymer of styrene and maleic anhydride, (c)
polystyrene-polyisobutylene-polystyrene block copolymer blended
with an alternating copolymer of styrene and maleic anhydride
having a molecular weight of approximately 50,000, (d)
polystyrene-polyisobutylene-polystyrene block copolymer blended
with an alternating copolymer of styrene and maleic anhydride
having a molecular weight of approximately 1700.
[0025] FIG. 5 illustrates cumulative release of paclitaxel as a
function of time for carrier layers containing paclitaxel and (a) a
polystyrene-polyisobutylene-polystyrene block copolymer, (b) a
random copolymer of styrene and maleic anhydride containing
approximately 7 wt % maleic anhydride blended with a
polystyrene-polyisobutylene-polystyrene block copolymer, and (c) a
random copolymer of styrene and maleic anhydride containing
approximately 14 wt % maleic anhydride blended with a
polystyrene-polyisobutylene-polystyrene block copolymer, in
accordance with an embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0026] The present invention relates to the use of styrene
copolymers in release layers that control the release of
therapeutic agent from an implantable or insertable medical
device.
[0027] By "release layer" is meant a layer that regulates the rate
of release of a therapeutic agent. Two preferred release layers for
use in accordance with the present invention are carrier layers and
barrier layers.
[0028] By "carrier layer" is meant a layer which contains a
therapeutic agent and from which the therapeutic agent is
released.
[0029] By "barrier layer" is meant a layer which is disposed
between a source of therapeutic agent and a site of intended
release and which impedes the rate at which the therapeutic agent
is released.
[0030] According to one aspect of the present invention, a medical
device is provided which comprises an outer carrier layer disposed
over at least a portion of an implantable or insertable medical
device. The outer carrier layer comprises a styrene copolymer, an
additional polymer and a therapeutic agent. Upon implantation or
insertion of the device, the therapeutic agent is released from the
carrier layer in a controlled fashion.
[0031] According to another aspect of the present invention, an
implantable or insertable medical device is provided, which
comprises (a) a therapeutic-agent-containing region and (b) a
barrier layer comprising a styrene copolymer and an additional
polymer over the therapeutic-agent-containing region. Because the
barrier layer is disposed over the therapeutic-agent-containing
region, the barrier layer acts to control release of the
therapeutic agent from the medical device after implantation or
insertion of the same.
[0032] Preferred implantable or insertable medical devices for use
in conjunction with the present invention include catheters (for
example, renal or vascular catheters such as balloon catheters),
guide wires, balloons, filters (e.g., vena cava filters), stents
(including coronary vascular stents, cerebral, urethral, ureteral,
biliary, tracheal, gastrointestinal and esophageal stents), stent
grafts, cerebral aneurysm filler coils (including GDC--Guglilmi
detachable coils--and metal coils), vascular grafts, myocardial
plugs, patches, pacemakers and pacemaker leads, heart valves,
biopsy devices, or any coated substrate (which can comprise, for
example, glass, metal, polymer, ceramic and combinations thereof)
that is implanted or inserted into the body, either for procedural
use or as an implant, and from which therapeutic agent is
released.
[0033] The medical devices contemplated for use in connection with
the present invention include drug delivery medical devices that
are used for either systemic treatment or for the localized
treatment of any mammalian tissue or organ. Non-limiting examples
are tumors; organs including but not limited to the heart, coronary
and peripheral vascular system (referred to overall as "the
vasculature"), lungs, trachea, esophagus, brain, liver, kidney,
bladder, urethra and ureters, eye, intestines, stomach, pancreas,
ovary, and prostate; skeletal muscle; smooth muscle; breast;
cartilage; and bone.
[0034] One particularly preferred medical device for use in
connection with the present invention is a vascular stent, which
delivers therapeutic agent into the vasculature for the treatment
of restenosis. As used herein, "treatment" refers to the prevention
of a disease or condition, the reduction or elimination of symptoms
associated with a disease or condition, or the substantial or
complete elimination a disease or condition. Preferred subjects are
mammalian subjects and more preferably human subjects.
[0035] "Therapeutic agents", "pharmaceutically active agents",
"pharmaceutically active materials", "drugs" and other related
terms may be used interchangeably herein and include genetic
therapeutic agents, non-genetic therapeutic agents and cells.
Therapeutic agents may be used singly or in combination.
[0036] Exemplary non-genetic therapeutic agents for use in
connection with the present invention include: (a) anti-thrombotic
agents such as heparin, heparin derivatives, urokinase, and PPack
(dextrophenylalanine proline arginine chloromethylketone); (b)
anti-inflammatory agents such as dexamethasone, prednisolone,
corticosterone, budesonide, estrogen, sulfasalazine and mesalamine;
(c) antineoplastic/antiproliferative/anti-miotic agents such as
paclitaxel, 5-fluorouracil, cisplatin, vinblastine, vincristine,
epothilones, endostatin, angiostatin, angiopeptin, monoclonal
antibodies capable of blocking smooth muscle cell proliferation,
and thymidine kinase inhibitors; (d) anesthetic agents such as
lidocaine, bupivacaine and ropivacaine; (e) anti-coagulants such as
D-Phe-Pro-Arg chloromethyl ketone, an RGD peptide-containing
compound, heparin, hirudin, antithrombin compounds, platelet
receptor antagonists, anti-thrombin antibodies, anti-platelet
receptor antibodies, aspirin, prostaglandin inhibitors, platelet
inhibitors and tick antiplatelet peptides; (f) vascular cell growth
promoters such as growth factors, transcriptional activators, and
translational promotors; (g) vascular cell growth inhibitors such
as growth factor inhibitors, growth factor receptor antagonists,
transcriptional repressors, translational repressors, replication
inhibitors, inhibitory antibodies, antibodies directed against
growth factors, bifunctional molecules consisting of a growth
factor and a cytotoxin, bifunctional molecules consisting of an
antibody and a cytotoxin; (h) protein kinase and tyrosine kinase
inhibitors (e.g., tyrphostins, genistein, quinoxalines); (i)
prostacyclin analogs; (j) cholesterol-lowering agents; (k)
angiopoietins; (l) antimicrobial agents such as triclosan,
cephalosporins, aminoglycosides and nitrofurantoin; (m) cytotoxic
agents, cytostatic agents and cell proliferation affectors; (n)
vasodilating agents; and (o) agents that interfere with endogenous
vascoactive mechanisms.
[0037] Exemplary genetic therapeutic agents for use in connection
with the present invention include anti-sense DNA and RNA as well
as DNA coding for: (a) anti-sense RNA, (b) tRNA or rRNA to replace
defective or deficient endogenous molecules, (c) angiogenic factors
including growth factors such as acidic and basic fibroblast growth
factors, vascular endothelial growth factor, epidermal growth
factor, transforming growth factor .alpha. and .beta.,
platelet-derived endothelial growth factor, platelet-derived growth
factor, tumor necrosis factor .alpha., hepatocyte growth factor and
insulin-like growth factor, (d) cell cycle inhibitors including CD
inhibitors, and (e) thymidine kinase ("TK") and other agents useful
for interfering with cell proliferation. Also of interest is DNA
encoding for the family of bone morphogenic proteins ("BMP's"),
including BMP-2, BMP-3, BMP-4, BMP-5, BMP-6 (Vgr-1), BMP-7 (OP-1),
BMP-8, BMP-9, BMP-10, BMP-11, BMP-12, BMP-13, BMP-14, BMP-15, and
BMP-16. Currently preferred BMP's are any of BMP-2, BMP-3, BMP-4,
BMP-5, BMP-6 and BMP-7. These dimeric proteins can be provided as
homodimers, heterodimers, or combinations thereof, alone or
together with other molecules. Alternatively, or in addition,
molecules capable of inducing an upstream or downstream effect of a
BMP can be provided. Such molecules include any of the "hedgehog"
proteins, or the DNA's encoding them.
[0038] Vectors for delivery of genetic therapeutic agents include
(a) plasmids, (b) viral vectors such as adenovirus, adenoassociated
virus and lentivirus, and (c) non-viral vectors such as lipids,
liposomes and cationic lipids.
[0039] Cells for use in connection with the present invention
include cells of human origin (autologous or allogeneic), including
stem cells, or from an animal source (xenogeneic), which can be
genetically engineered, if desired, to deliver proteins of
interest.
[0040] Numerous therapeutic agents, not necessarily exclusive of
those listed above, have been identified as candidates for vascular
treatment regimens, for example, as agents targeting restenosis.
Such agents are useful for the practice of the present invention
and include one or more of the following: (a) Ca-channel blockers
including benzothiazapines such as diltiazem and clentiazem,
dihydropyridines such as nifedipine, amlodipine and nicardapine,
and phenylalkylamines such as verapamil, (b) serotonin pathway
modulators including: 5-HT antagonists such as ketanserin and
naftidrofuryl, as well as 5-HT uptake inhibitors such as
fluoxetine, (c) cyclic nucleotide pathway agents including
phosphodiesterase inhibitors such as cilostazole and dipyridamole,
adenylate/Guanylate cyclase stimulants such as forskolin, as well
as adenosine analogs, (d) catecholamine modulators including
.alpha.-antagonists such as prazosin and bunazosine,
.beta.-antagonists such as propranolol and
.alpha./.beta.-antagonists such as labetalol and carvedilol, (e)
endothelin receptor antagonists, (f) nitric oxide donors/releasing
molecules including organic nitrates/nitrites such as
nitroglycerin, isosorbide dinitrate and amyl nitrite, inorganic
nitroso compounds such as sodium nitroprusside, sydnonimines such
as molsidomine and linsidomine, nonoates such as diazenium diolates
and NO adducts of alkanediamines, 5-nitroso compounds including low
molecular weight compounds (e.g., S-nitroso derivatives of
captopril, glutathione and N-acetyl penicillamine) and high
molecular weight compounds (e.g., S-nitroso derivatives of
proteins, peptides, oligosaccharides, polysaccharides, synthetic
polymers/oligomers and natural polymers/oligomers), as well as
C-nitroso-compounds, O-nitroso-compounds, N-nitroso-compounds and
L-arginine, (g) ACE inhibitors such as cilazapril, fosinopril and
enalapril, (h) ATII-receptor antagonists such as saralasin and
losartin, (i) platelet adhesion inhibitors such as albumin and
polyethylene oxide, (j) platelet aggregation inhibitors including
aspirin and thienopyridine (ticlopidine, clopidogrel) and GP
IIb/IIIa inhibitors such as abciximab, epitifibatide and tirofiban,
(k) coagulation pathway modulators including heparinoids such as
heparin, low molecular weight heparin, dextran sulfate and
.beta.-cyclodextrin tetradecasulfate, thrombin inhibitors such as
hirudin, hirulog, PPACK (D-phe-L-propyl-L-arg-chloromethylketone)
and argatroban, FXa inhibitors such as antistatin and TAP (tick
anticoagulant peptide), Vitamin K inhibitors such as warfarin, as
well as activated protein C, (l) cyclooxygenase pathway inhibitors
such as aspirin, ibuprofen, flurbiprofen, indomethacin and
sulfinpyrazone, (m) natural and synthetic corticosteroids such as
dexamethasone, prednisolone, methprednisolone and hydrocortisone,
(n) lipoxygenase pathway inhibitors such as nordihydroguairetic
acid and caffeic acid, (o) leukotriene receptor antagonists, (p)
antagonists of E- and P-selectins, (q) inhibitors of VCAM-1 and
ICAM-1 interactions, (r) prostaglandins and analogs thereof
including prostaglandins such as PGE1 and PGI2 and prostacyclin
analogs such as ciprostene, epoprostenol, carbacyclin, iloprost and
beraprost, (s) macrophage activation preventers including
bisphosphonates, (t) HMG-CoA reductase inhibitors such as
lovastatin, pravastatin, fluvastatin, simvastatin and cerivastatin,
(u) fish oils and omega-3-fatty acids, (v) free-radical
scavengers/antioxidants such as probucol, vitamins C and E,
ebselen, trans-retinoic acid and SOD mimics, (w) agents affecting
various growth factors including FGF pathway agents such as bFGF
antibodies and chimeric fusion proteins, PDGF receptor antagonists
such as trapidil, IGF pathway agents including somatostatin analogs
such as angiopeptin and ocreotide, TGF-.beta. pathway agents such
as polyanionic agents (heparin, fucoidin), decorin, and TGF-.beta.
antibodies, EGF pathway agents such as EGF antibodies, receptor
antagonists and chimeric fusion proteins, TNF-.alpha. pathway
agents such as thalidomide and analogs thereof, Thromboxane A2
(TXA2) pathway modulators such as sulotroban, vapiprost, dazoxiben
and ridogrel, as well as protein tyrosine kinase inhibitors such as
tyrphostin, genistein and quinoxaline derivatives, (x) MMP pathway
inhibitors such as marimastat, ilomastat and metastat, (y) cell
motility inhibitors such as cytochalasin B, (z)
antiproliferative/antineoplastic agents including antimetabolites
such as purine analogs (6-mercaptopurine), pyrimidine analogs
(e.g., cytarabine and 5-fluorouracil) and methotrexate, nitrogen
mustards, alkyl sulfonates, ethylenimines, antibiotics (e.g.,
daunorubicin, doxorubicin), nitrosoureas, cisplatin, agents
affecting microtubule dynamics (e.g., vinblastine, vincristine,
colchicine, paclitaxel and epothilone), caspase activators,
proteasome inhibitors, angiogenesis inhibitors (e.g., endostatin,
angiostatin and squalamine), rapamycin, cerivastatin, flavopiridol
and suramin, (aa) matrix deposition/organization pathway inhibitors
such as halofuginone or other quinazolinone derivatives and
tranilast, (bb) endothelialization facilitators such as VEGF and
RGD peptide, and (cc) blood rheology modulators such as
pentoxifylline.
[0041] Numerous additional therapeutic agents useful for the
practice of the present invention are also disclosed in U.S. Pat.
No. 5,733,925 assigned to NeoRx Corporation, the entire disclosure
of which is incorporated by reference.
[0042] A wide range of therapeutic agent loadings can be used in
connection with the medical devices of the present invention, with
the amount of loading being readily determined by those of ordinary
skill in the art and ultimately depending, for example, upon the
condition to be treated, the nature of the therapeutic agent
itself, the means by which the therapeutic agent is administered to
the intended subject, and so forth.
[0043] The present invention utilizes release layers comprising a
styrene copolymer and an additional polymer.
[0044] A "styrene copolymer" is a polymer formed from two or more
dissimilar monomers, at least one of which is styrene, or a styrene
derivative (e.g., alpha-methyl styrene, ring-alkylated styrenes or
ring-halogenated styrenes, or other substituted styrenes where one
or more substituents are present on the aromatic ring). Such
copolymers may be, for example, random copolymers, alternating
copolymers, block copolymers or graft copolymers, and may be, for
example, linear, star-shaped, or branched in form. Copolymers
comprising random polymer chains formed from two or more dissimilar
monomers, at least one of which is styrene or a styrene derivative
(referred to herein as "random styrene copolymers") and copolymers
comprising alternating polymer chains formed from two or more
dissimilar monomers, at least one of which is styrene or a styrene
derivative (referred to herein as "alternating styrene copolymers")
are preferred.
[0045] Examples of styrene copolymers for the practice of the
present invention include copolymers of: (1) a monomer of styrene
or a styrene derivative with (2) at least one additional monomer,
preferably selected from unsaturated monomers such as: (a) alkylene
monomers, such as ethylene, propylene, butadiene, butylenes (e.g.,
butylene, isobutylene), and isoprene; (b) halogenated alkylene
monomers (e.g., tetrafluoroethylene and chloroethylene); (c) vinyl
monomers and derivatives, such as, methyl vinyl ether, vinyl
acetate, vinyl ethylene (butadiene), vinyl chloride, vinyl
pyrrolidone, vinyl cyanide (acrylonitrile), and vinyl alcohol; (d)
acrylic acid monomers and derivatives, such as methyl acrylate,
methyl methacrylate, acrylic acid, methacrylic acid, hydroxyethyl
acrylate, hydroxyethyl methacrylate, glyceryl acrylate, glyceryl
methacrylate, acrylamide, methacrylamide and ethacrylamide; and (e)
maleic anhydride monomers and derivatives, including maleic
anhydride, maleic anhydride in a free acid form, maleic anhydride
in a salt form, and maleic anhydride in a partial ester form.
[0046] Specific examples of styrene copolymers include
acrylonitrile-butadiene-styrene copolymers,
acrylonitrile-chlorinated polyethylene-styrene copolymers,
acrylonitrile-styrene-acrylate copolymers,
acrylonitrile-ethylene-propylene-styrene copolymers,
ethylene-styrene copolymers, methyl methacrylate-butadiene-styrene
copolymers, methyl methacrylate-acrylonitrile-butadiene-styrene
copolymers, olefin modified styrene acrylonitrile copolymers,
butadiene-styrene copolymers, styrene-isoprene copolymers,
styrene-acrylonitrile copolymers, styrene-ethylene-butylene
copolymers, styrene-maleic anhydride copolymers, and styrene-methyl
methacrylate copolymers.
[0047] In forming the release layers of the present invention, the
styrene copolymers are blended or crosslinked with one or more
additional polymers. The additional polymers may be, for example,
homopolymers or copolymers, crosslinked or uncrosslinked, linear or
branched, natural or synthetic, thermoplastic or thermosetting.
[0048] Additional polymers include the following: polycarboxylic
acid polymers and copolymers including polyacrylic acids (e.g.,
acrylic latex dispersions and various polyacrylic acid products
such as HYDROPLUS, available from Boston Scientific Corporation,
Natick Mass. and described in U.S. Pat. No. 5,091,205, the
disclosure of which is hereby incorporated herein by reference, and
HYDROPASS, also available from Boston Scientific Corporation);
acetal polymers and copolymers; acrylate and methacrylate polymers
and copolymers; cellulosic polymers and copolymers, including
cellulose acetates, cellulose nitrates, cellulose propionates,
cellulose acetate butyrates, cellophanes, rayons, rayon
triacetates, and cellulose ethers such as carboxymethyl celluloses
and hydroxyalkyl celluloses; polyoxymethylene polymers and
copolymers; polyimide polymers and copolymers such as polyether
block imides, polyamidimides, polyesterimides, and polyetherimides;
polysulfone polymers and copolymers including polyarylsulfones and
polyethersulfones; polyamide polymers and copolymers including
nylon 6,6, polycaprolactams and polyacrylamides; resins including
alkyd resins, phenolic resins, urea resins, melamine resins, epoxy
resins, allyl resins and epoxide resins; polycarbonates;
polyacrylonitriles; polyvinylpyrrolidones (cross-linked and
otherwise); polymers and copolymers of vinyl monomers including
polyvinyl alcohols, polyvinyl halides such as polyvinyl chlorides,
ethylene-vinylacetate copolymers (EVA), polyvinylidene chlorides,
polyvinyl ethers such as polyvinyl methyl ethers, polystyrenes,
styrene-butadiene copolymers, acrylonitrile-styrene copolymers,
acrylonitrile-butadiene-styrene copolymers,
styrene-butadiene-styrene copolymers and
styrene-isobutylene-styrene copolymers, polyvinyl ketones,
polyvinylcarbazoles, and polyvinyl esters such as polyvinyl
acetates; polybenzimidazoles; ionomers; polyalkyl oxide polymers
and copolymers including polyethylene oxides (PEO);
glycosaminoglycans; polyesters including polyethylene
terephthalates and aliphatic polyesters such as polymers and
copolymers of lactide (which includes lactic acid as well as d-,l-
and meso lactide), epsilon-caprolactone, glycolide (including
glycolic acid), hydroxybutyrate, hydroxyvalerate, para-dioxanone,
trimethylene carbonate (and its alkyl derivatives),
1,4-dioxepan-2-one, 1,5-dioxepan-2-one, and
6,6-dimethyl-1,4-dioxan-2-one (a copolymer of polylactic acid and
polycaprolactone is one specific example); polyether polymers and
copolymers including polyarylethers such as polyphenylene ethers,
polyether ketones, polyether ether ketones; polyphenylene sulfides;
polyisocyanates (e.g., U.S. Pat. No. 5,091,205 describes medical
devices coated with one or more polyisocyanates such that the
devices become instantly lubricious when exposed to body fluids);
polyolefin polymers and copolymers, including polyalkylenes such as
polypropylenes, polyethylenes (low and high density, low and high
molecular weight), polybutylenes (such as polybut-1-ene and
polyisobutylene), poly-4-methyl-pen-1-enes, ethylene-alpha-olefin
copolymers, ethylene-methyl methacrylate copolymers and
ethylene-vinyl acetate copolymers; fluorinated polymers and
copolymers, including polytetrafluoroethylenes (PTFE),
poly(tetrafluoroethylene-co-hexafluoropropene) (FEP), modified
ethylene-tetrafluoroethylene copolymers (ETFE), and polyvinylidene
fluorides (PVDF); silicone polymers and copolymers; polyurethanes
(e.g., BAYHYDROL polyurethane dispersions); p-xylylene polymers;
polyiminocarbonates; copoly(ether-esters) such as polyethylene
oxide-polylactic acid copolymers; polyphosphazines; polyalkylene
oxalates; polyoxaamides and polyoxaesters (including those
containing amines and/or amido groups); polyorthoesters;
biopolymers, such as polypeptides, proteins, polysaccharides and
fatty acids (and esters thereof), including fibrin, fibrinogen,
collagen, elastin, chitosan, gelatin, starch, glycosaminoglycans
such as hyaluronic acid; as well as blends and copolymers of the
above.
[0049] Some exemplary additional polymers for use in combination
with the present invention are block copolymers comprising at least
two polymeric blocks A and B. Examples of such block copolymers
include the following: (a) BA (linear diblock), (b) BAB or ABA
(linear triblock), (c) B(AB).sub.n or A(BA).sub.n (linear
alternating block), or (d) X-(AB).sub.n or X-(BA).sub.n (includes
diblock, triblock and other radial block copolymers), where n is a
positive whole number and X is a starting seed, or initiator,
molecule.
[0050] One specifically preferred group of polymers have
X-(AB).sub.n structures, which are frequently referred to as
diblock copolymers and triblock copolymers where n=1 and n=2,
respectively (this terminology disregards the presence of the
starting seed molecule, for example, treating A-X-A as a single A
block with the triblock therefore denoted as BAB). Where n=3 or
more, these structures are commonly referred to as star-shaped
block copolymers.
[0051] Other examples of additional polymers include branched block
copolymers such as dendritic block copolymers (e.g., arborescent
block copolymers), wherein at least one of the A and B blocks is
branched, and preferably wherein the A blocks are branched and
capped by the B blocks.
[0052] The A blocks are preferably soft elastomeric components
which are based upon one or more polyolefins or other polymer with
a glass transition temperature at or below room temperature. For
example, the A blocks can be polyolefinic blocks having alternating
quaternary and secondary carbons of the general formulation:
--(CRR'--CH.sub.2).sub.n--, where R and R' are linear or branched
aliphatic groups such as methyl, ethyl, propyl, isopropyl, butyl,
isobutyl and so forth, or cyclic aliphatic groups such as
cyclohexane, cyclopentane, and the like, with and without pendant
groups. Preferred polyolefinic blocks include blocks of
isobutylene,
##STR00001##
(i.e., polymers where R and R' are the same and are methyl groups).
Other examples of A blocks include silicone rubber blocks and
acrylate rubber blocks.
[0053] The B blocks are preferably hard thermoplastic blocks with
glass transition temperatures significantly higher than the
elastomeric A block that, when combined with the soft A blocks, are
capable of, inter alia, altering or adjusting the hardness of the
resulting copolymer to achieve a desired combination of qualities.
Preferred B blocks are polymers of methacrylates or polymers of
vinyl aromatics. More preferred B blocks are (a) made from monomers
of styrene
##STR00002##
styrene derivatives (e.g., .alpha.-methylstyrene, ring-alkylated
styrenes or ring-halogenated styrenes or other substituted styrenes
where one or more substituents are present on the aromatic ring) or
mixtures of the same, collectively referred to herein as "styrenic
blocks" or "polystyrenic blocks" or are (b) made from monomers of
methylmethacrylate, ethylmethacrylate hydroxyethyl methacrylate or
mixtures of the same.
[0054] More preferred are additional polymers that are elastomeric.
As defined herein, an "elastomeric" polymer is a polymer that can
be stretched to at least 1.5 times its original length at room
temperature and, upon release of the stretching stress, will return
with force to its approximate original length.
[0055] In some particularly preferred embodiments of the present
invention, a styrene copolymer is combined with one or more of the
following elastomers: (a) a copolymer of polyisobutylene with
polystyrene or poly-alpha-methylstyrene, more preferably
polystyrene-polyisobutylene-polystyrene triblock copolymers which,
along with other polymers appropriate for the practice of the
present invention, are described, for example, in U.S. Pat. No.
5,741,331, U.S. Pat. No. 4,946,899 and U.S. Ser. No. 09/734,639,
each of which is hereby incorporated by reference in its entirety;
(b) a copolymer containing one or more blocks of polystyrene and
one or more random polymer blocks of ethylene and butylene, for
example, a polystyrene-polyethylene/butylene-polystyrene (SEBS)
block copolymer, available as Kraton.TM. G series polymers
available from Kraton Polymers; (c) a homopolymer of n-butyl
methacrylate (BMA); and (d) arborescent polyisobutylene-polystyrene
block copolymers such as those described in Kwon et al.,
"Arborescent Polyisobutylene-Polystyrene Block Copolymers-a New
Class of Thermoplastic Elastomers," Polymer Preprints, 2002, 43(1),
266, which is hereby incorporated by reference in its entirety.
[0056] The release characteristics associated with the release
layers of the present invention can be varied in a number of ways,
including the following: (a) varying the type of styrene
copolymer(s) used within the release layer, (b) varying the
molecular weight of the styrene copolymer(s) used within the
release layer, (c) varying the relative amount of styrene monomer
in the copolymer, relative to the other monomers, and (d) varying
the type, molecular weight and/or relative amount of the additional
polymer. Several of these effects are demonstrated in the Examples
below.
[0057] Medical devices having a sustained release profile are
preferred in many cases. By "sustained release profile" is meant a
release profile in which less than 25% of the total release from
the medical device that occurs over the course of
implantation/insertion in the body occurs within the first 1-3 days
of administration. Conversely, this means that more than 75% of the
total release from the medical device will occur after the device
has been implanted/inserted for 1-3 days.
[0058] In general, the release layers of the present invention are
formed using any number of known techniques. Solvent-based
techniques, in which the styrene copolymer and the additional
polymer are dissolved or dispersed in a solvent prior to layer
formation, are preferred.
[0059] Where solvent-based techniques are used, the solvent system
that is selected will contain one or more solvent species. The
solvent system preferably is a good solvent for the polymers and,
where included, for the therapeutic agent as well. The particular
solvent species that make up the solvent system may also be
selected based on other characteristics including drying rate and
surface tension.
[0060] Solvent species that can be used in connection with the
present invention include any combination of one or more of the
following: (a) water, (b) alkanes such as ethane, hexane, octane,
cyclohexane, heptane, isohexane, butane, pentane, isopentane,
2,2,4-trimethlypentane, nonane, decane, dodecane, hexadecane,
eicosane, methylcyclohexane, cis-decahydronaphthalene and
trans-decahydronaphthalene, (c) aromatic species such as benzene,
toluene, xylene(s), naphthalene, styrene, ethylbenzene,
1-methylnaphthalene, 1,3,5-trimethylbenzene, tetrahydronaphthalene,
diphenyl and 1,4-diethylbenzene, (d) halohydrocarbons including (i)
chlorohyhdrocarbons such as chloroform, methyl chloride,
dichloromethane, 1,1-dichloroethylene, ethylene dichloride,
ethylidene chloride, propyl chloride, cyclohexyl chloride,
1,1,1-trichloroethane, perchloroethylene, trichloroethylene, butyl
chloride, carbon tetrachloride, tetrachloroethylene, chlorobenzene,
o-dichlorobenzene, benzyl chloride, trichlorobiphenyl,
methylcyclohexane, 1,1,2,2-tetrachloroethane (ii) fluorinated
halogenated species such as chlorodiflouoromethane,
dichlorofluoromethane, dichlorodifluoromethane,
trichlorofluoromethane, 1,2-dichlorotetrafluoroethane,
1,1,2-trichlorotrifluoroethane, perfluor(methylcyclohexane),
perfluor(dimethylcyclohexane) and (iii) other halohydrocarbons such
as ethyl bromide, ethylidene bromide, ethylene dibromide,
tribromomethane, bromotrifluoromethane, 1,1,2,2-tetrabromoethane,
bromobenzene, bromochloromethane, 1-bromonaphthalene, methyl
iodide, methylene diiodide (e) acid aldehydes/anhydrides such as
acetaldehyde, furfural, butyraldehyde, benzaldehyde, acetyl
chloride, succinic anhydride and acetic anhydride, (f) alcohols
including (i) phenols such as phenol, 1,3-benzenediol, m-cresol,
o-methoxyphenol, methyl salicylate and nonylphenol, (ii) polyhydric
alcohols such as ethylene glycol, glycerol, propylene glycol,
1,3-butanediol, diethylene glycol, triethylene glycol, hexylene
glycol and dipropylene glycol, and (iii) other alcohols such as
methanol, ethanol, ethylene cyanohydrin, allyl alcohol, 1-propanol,
2-propanol, 3-chloropropanol, furfuryl alcohol, 1-butanol,
2-butanol, benzyl alcohol, isobutanol, cyclohexanol, 1-pentanol,
2-ethyl-1-butanol, diacetone alcohol, 1,3-dimethyl-1-butanol, ethyl
lactate, butyl lactate, ethylene glycol monomethyl ether, ethylene
glycol monoethyl ether, diethylene glycol monomethyl ether,
diethylene glycol monoethyl ether, ethylene glycol monobutyl ether,
2-ethyl-1-hexanol, 1-octanol, 2-octanol, diethylene glycol
monobutyl ether, 1-decanol, 1-tridecyl alcohol, nonyl-phenoxy
ethanol, oleyl alcohol, triethylene glycol mono-oleyl ether, (g)
ethers such as, epichlorohydrin, furan, 1,4-dioxane,
dimethoxymethane, diethyl ether, bis-(2-chloroethyl) ether,
anisole, di-(2-methoxyethyl)ether, dibenzyl ether,
di-(2-chloroisopropyl)ether, bis-(m-phenoxyphenol) ether, dimethyl
ether and tetrahydrofuran, (h) ketones, such as acetone,
cylohexanone, isophorone, diethyl ketone, mesityl oxide,
acetophenone, methyl ethyl ketone, methyl isoamyl ketone, methyl
isobutyl ketone, and methyl propyl ketone, (i) acids such as formic
acid, acetic acid, benzoic acid, butyric acid, octanoic acid, oleic
acid, stearic acid, (j) esters/acetates such as ethylene carbonate,
butyrolactone, propylene-1,2-carbonate, ethyl chloroformate, ethyl
acetate, trimethyl phosphate, diethyl carbonate, diethyl sulfate,
ethyl formate, methyl acetate, n-butyl acetate, isobutyl acetate,
t-butyl acetate, 2-ethoxyethyl acetate, isoamyl acetate, dimethyl
phthalate, ethyl cinnamate, triethyl phosphate, diethyl phosphate,
butyl benzyl phthalate, dibutyl phthalate, diethyl phthalate,
tricrysyl phosphate, tributyl phosphate, dibutyl sebacate, methyl
oleate, dioctyl phthalate, dibutyl stearate isopropyl acetate,
isobutyl isobutyrate, n-propyl acetate and n-butyl propionate, (k)
nitrogen compounds such as acetonitrile, acrylonitrile,
propionitrile, butyronitrile, nitromethane, nitroethane,
2-nitropropane, nitrobenzene, ethanolamine, ethylenediamine,
1,1-dimethylhydrazine, 2-pyrrolidone, pyridine, propylamine,
morpholine, analine, n-methyl-2-pyrrolidone, butylamine,
diethylamine, cyclohexylamine, quinoline, dipropylamine, formamide,
n,n-dimethylformamide, n,n-dimethylacetamide, tetramethylurea,
hexamethyl phosphoramide, diethylenetriamine, triethylamine and
triethanolamine, and (l) sulfur compounds such as carbon disulfide,
dimethylsulfoxide, ethanethiol, dimethyl sulfone and diethyl
sulfide.
[0061] Preferred solvent-based techniques include, but are not
limited to, solvent casting techniques, spin coating techniques,
web coating techniques, solvent spraying techniques, dipping
techniques, techniques involving coating via mechanical suspension,
including air suspension, ink jet techniques, electrostatic
techniques, and combinations of these processes. Typically, a
solution containing solvent and polymers (and, in some cases, a
therapeutic agent) is applied to a substrate to form a release
layer (e.g., a carrier layer or barrier layer). The substrate is
typically all or a portion of an implantable or insertable medical
device, to which the release layer is applied.
[0062] Where appropriate, techniques such as those listed above can
be repeated or combined to build up a release layer to a desired
thickness. The thickness of the release layer can be varied in
other ways as well. For example, in one preferred process, solvent
spraying, coating thickness can be increased by modification of
coating process parameters, including increasing spray flow rate,
slowing the movement between the substrate to be coated and the
spray nozzle, providing repeated passes and so forth.
[0063] In the case of a carrier layer, for example, a therapeutic
agent can be included in the above-described polymer solution if
desired, and hence co-established with the carrier layer. In other
embodiments, on the other hand, the therapeutic agent can be
dissolved or dispersed within a solvent, and the resulting solution
contacted with a previously formed layer, for example, using one or
more of the solvent based application techniques described above
(e.g., dipping, spraying, etc.).
[0064] Barrier layers, on the other hand, are formed over a
therapeutic-agent-containing region. In some embodiments, however,
the therapeutic-agent-containing region comprises one or more
polymers, which can be selected, for example, from the polymers
listed above. As such, the therapeutic-agent-containing region can
also be established using solvent-based techniques (e.g., dipping,
spraying, etc.) such as those discussed above. In other
embodiments, the therapeutic-agent-containing region beneath the
barrier layer is established without an associated polymer. For
example, the therapeutic agent can simply be dissolved or dispersed
in a liquid, and the resulting solution/dispersion contacted with a
substrate, for instance, using one or more of the above-described
application techniques.
[0065] Where the release layer is formed using a solvent based
technique, it is preferably dried after application to remove the
solvents. The release layer typically further conforms to the
underlying surface during the drying process.
[0066] The invention is further described with reference to the
following non-limiting Examples.
Example 1
[0067] A solution is provided that contains 25 weight %
tetrahydrofuran (THF), 74 wt % toluene, 0.25 wt % paclitaxel and
0.75 wt % of a polymer composition or blend.
[0068] One control solution is prepared by mixing 0.75 wt % of the
block copolymer polystyrene-polyisobutylene-polystyrene block
copolymer (SIBS) with the solvents and paclitaxel. The SIBS
copolymer is synthesized using known techniques such as those
described in U.S. Pat. No. 5,741,331, U.S. Pat. No. 4,946,899 and
U.S. Ser. No. 09/734,639.
[0069] A first corresponding test solution contains 0.65 wt % of
the SIBS copolymer and 0.10 wt % of a random copolymer of styrene
and maleic anhydride containing approximately 14 wt % maleic
anhydride (SMA14). The SMA14 copolymer is purchased from
Sigma-Aldrich, or is available from Nova Chemical as Dylark
332.
[0070] Another control solution is prepared by mixing 0.75 wt % of
the homopolymer poly(butyl methacrylate) (BMA) with the solvents
and paclitaxel. BMA may be purchased from Sigma-Aldrich at a
molecular weight of 337,000.
[0071] A second test solution containing 0.65 wt % of the BMA
homopolymer and 0.10 wt % of SMA14 copolymer in prepared.
[0072] A third control solution is prepared with 0.75 wt % of a
polystyrene-b-poly(ethylene-r-butylene)-b-polystyrene block
copolymer (SEBS). The SEBS copolymer is obtained from
Sigma-Aldrich, but is also known by the trade name Kraton.TM..
[0073] A third test solution is prepared using 0.65 wt % of the
SEBS copolymer and 0.10 wt % of the SMA14 copolymer.
[0074] All solutions are prepared by (1) mixing the paclitaxel and
tetrahydrofuran, (2) adding the copolymer or copolymers, (3) adding
the toluene, (4) thoroughly mixing (e.g., overnight), and (5)
filtering.
[0075] The solution is then placed in a syringe pump and fed to a
spray nozzle. A stent is mounted onto a holding device parallel to
the nozzle and, if desired, rotated to ensure uniform coverage.
Depending on the spray equipment used, either the component or
spray nozzle can be moved while spraying such that the nozzle moves
along the component while spraying for one or more passes. After a
carrier coating is formed in this fashion, the stent is dried, for
example, by placing it in a preheated oven for 30 minutes at
65.degree. C., followed by 3 hours at 70.degree. C.
[0076] Three stents are formed in this manner for each of the
various polymeric solutions. Paclitaxel release is then measured as
a function of time in PBS with 0.5 wt % Tween.RTM. 20
(polyoxyethylene(20) sorbitan monolaurate) available from
Sigma-Aldrich. The results, presented as the cumulative release of
paclitaxel as a function of time, are graphically illustrated in
FIG. 1.
[0077] These results indicate that the release rate of a
therapeutic agent from various polymeric carrier layers can be
modulated by the addition of random copolymer containing styrene
and maleic anhydride.
Example 2
[0078] A series of solutions are prepared in a procedure similar to
the procedure used in Example 1. All solutions contain the
following: 25 wt % tetrahydrofuran (THF), 74 wt % toluene, 0.25 wt
% paclitaxel and 0.75 wt % of a polymer composition or blend.
[0079] The control solutions are prepared by mixing 0.75 wt % the
SIBS copolymer (see Example 1) or 0.75 wt % of the SMA14 copolymer
(see Example 1) with the solvents and paclitaxel.
[0080] Test solutions are made containing the following polymeric
constituents: (a) 0.5 wt % SMA14 and 0.25 wt % SIBS, (b) 0.3 wt %
SMA14 and 0.45 wt % SIBS, (c) 0.2 wt % SMA14 and 0.55 wt % SIBS,
(d) 0.1 wt % SMA14 and 0.55 wt % SIBS, (e) 0.15 wt % SMA14 and 0.60
wt % SIBS, (f) 0.1 wt % SMA14 and 0.65 wt % SIBS (two data sets),
and (g) 0.05 wt % SMA14 and 0.7 wt % SIBS.
[0081] The solutions are applied to stents and dried according to
the procedures of Example 1. Three stents are coated using each of
the above solutions. The cumulative release of paclitaxel as a
function of time is then measured as in Example 1. The results are
graphically illustrated in FIGS. 2A and 2B.
[0082] These results indicate that the release rate of a
therapeutic agent from a carrier layer comprising a polymeric
carrier can be modulated by the addition of a random copolymer
containing styrene and maleic anhydride in various proportions.
Example 3
[0083] A series of solutions are prepared in a procedure similar to
the procedure used in Example 1. All solutions contain the
following: 25 wt % tetrahydrofuran (THF), 74 wt % toluene, 0.25 wt
% paclitaxel and 0.75 wt % of a polymer or blend.
[0084] The control solution (two data sets) is prepared by mixing
0.75 wt % of the SIBS copolymer (see Example 1) with the solvents
and paclitaxel.
[0085] Test solutions are made containing the following polymeric
constituents: (a) 0.3 wt % styrene-co-acrylonitrile random
copolymer containing approximately 25 wt % acrylonitrile (SAN25)
and 0.45 wt % SIBS, (b) 0.10 wt % SAN25 and 0.65 wt % SIBS. SAN25
may be purchased from Sigma-Aldrich at a molecular weight of
165,000.
[0086] The solutions are applied to stents and dried according to
the procedures of Example 1. Three stents are coated using each of
the above solutions. The cumulative release of paclitaxel as a
function of time is then measured as in Example 1. The results are
graphically illustrated in FIG. 3.
[0087] These results indicate that the release rate of a
therapeutic agent from a carrier layer comprising a polymeric
carrier can be modulated by the addition of a copolymer of styrene
and acrylonitrile in various proportions.
Example 4
[0088] A series of solutions are prepared in a procedure like that
used in Example 1. All solutions contain the following: 25 wt %
tetrahydrofuran (THF), 74 wt % toluene, 0.25 wt % paclitaxel and
0.75 wt % polymer.
[0089] A control solution is prepared using 0.75 wt % of the SIBS
copolymer (see Example 1).
[0090] A first test solution is prepared using 0.1% SMA14, a random
copolymer of styrene and maleic anhydride containing approx. 14 wt
% maleic anhydride (see Example 1) and 0.65% SIBS.
[0091] A second test solution is prepared using 0.722 wt % SIBS
copolymer and 0.028 wt % of an alternating copolymer of styrene and
maleic anhydride (SMA50) having a molecular weight of approximately
50,000, purchased from Scientific Polymer Products, Inc.
[0092] A third test solution is prepared using 0.722 wt % SIBS
copolymer and 0.028 wt % of an alternating copolymer of styrene and
maleic anhydride (SMA50) having a molecular weight of approximately
1700, also purchased from Scientific Polymer Products, Inc.
[0093] Note that the maleic anhydride (MA) content is the same for
all test solutions.
SMA14: 14% MA.times.10% SMA=1.4% MA total SMA50: 50% MA.times.2.8%
SMA=1.4% MA total
[0094] The solutions are applied to stents and dried according to
the procedures of Example 1. Three stents are coated from each of
the above solutions. The cumulative release of paclitaxel as a
function of time is then measured as in Example 1. The results are
graphically illustrated in FIG. 4.
[0095] These results indicate that the release rate of a
therapeutic agent from a carrier layer comprising a copolymer of
maleic anhydride and styrene can be modulated by varying the
molecular weight of the copolymer in the carrier layer.
Example 5
[0096] A series of solutions are prepared in a procedure like that
used in Example 1. All solutions contain the following: 25 wt %
tetrahydrofuran (THF), 74 wt % toluene, 0.25 wt % paclitaxel and
0.75 wt % polymer.
[0097] A control solution is prepared using 0.75 wt % of the SIBS
copolymer (see Example 1).
[0098] A first test solution is prepared using 0.1% SMA14, a random
copolymer of styrene and maleic anhydride containing approx 14 wt %
maleic anhydride (see Example 1) and 0.65% SIBS.
[0099] A second test solution is prepared using 0.1 wt % SMA7, a
random copolymer of styrene and maleic anhydride containing
approximately 7 wt % maleic anhydride, and 0.65% SIBS.
[0100] The solutions are applied to stents and dried according to
the procedures of Example 1. Three stents are coated from each of
the above solutions. The cumulative release of paclitaxel as a
function of time is then measured as in Example 1. The results are
graphically illustrated in FIG. 5.
[0101] These results indicate that the release rate of a
therapeutic agent from a carrier layer containing a copolymer of
maleic anhydride and styrene can be increased by varying the
relative amounts of maleic anhydride monomer and styrene monomer in
the copolymer.
[0102] Although various embodiments are specifically illustrated
and described herein, it will be appreciated that modifications and
variations of the present invention are covered by the above
teachings and are within the purview of the appended claims without
departing from the spirit and intended scope of the invention.
* * * * *