US20050287184A1

US20050287184A1 - Drug-delivery stent formulations for restenosis and vulnerable plaque

Info

Publication number: US20050287184A1
Application number: US10/881,540
Authority: US
Inventors: Syed Hossainy; Gordon Stewart; Deborah Kilpatrick; Jeffrey Ellis; Gene Park; Gina Zhang; Paul Consigny; Yiwen Tang
Original assignee: ADVANCED COARDIOVASCULAR SYSTEMS Inc
Current assignee: ADVANCED COARDIOVASCULAR SYSTEMS Inc
Priority date: 2004-06-29
Filing date: 2004-06-29
Publication date: 2005-12-29
Also published as: US20070269484A1; EP1765430A1; US8017140B2; WO2006004792A1; JP2008504890A

Abstract

Drug-delivery stents capable of providing release of two or more drugs such as everolimus and estradiol are provided. The stents can be used for treating a disease such as restenosis and vulnerable plaque.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
This invention relates to drug combinations, formulations, and methods of application for the treatment or prevention of vascular disorder such as restenosis and/or vulnerable plaque. More superficially, the invention relates to application of everolimus and estradiol such as by a stent.
2. Description of the Background
Plaques have been associated with stenosis and restenosis. While treatments of plaque-induced stenosis and restenosis have advanced significantly over the last few decades, the morbidity and mortality associated with vascular plaques have remained significant. Recent work suggests that plaques may generally fall into one of two different general types: standard stenotic plaques and vulnerable plaques. Stenotic plaque, which is sometimes referred to as thrombosis-resistant plaque, can generally be treated effectively by the known intravascular lumen opening techniques. Although the stenosis the plaques induce may require treatment, these atherosclerotic plaques themselves are often a benign and effectively treatable disease.
Unfortunately, as plaque matures, narrowing of a blood vessel by a proliferation of smooth muscle cells, matrix synthesis, and lipid accumulation may result in formation of a plaque which is quite different than a standard stenotic plaque. Such atherosclerotic plaque becomes thrombosis-prone, and can be highly dangerous. This thrombosis-prone or vulnerable plaque may be a frequent cause of an acute coronary syndrome.
Coronary heart disease is generally thought to be caused by the narrowing of coronary arteries by atherosclerosis, the buildup of fatty deposits in the lining of the arteries. The process that may lead to atherosclerosis begins with the accumulation of excess fats and cholesterol in the blood. These substances infiltrate the lining of arteries, gradually increasing in size to form deposits commonly referred to as plaque or atherosclerotic occlusions. Plaques narrow the arterial lumen and impede blood flow. Blood cells may collect around the plaque, eventually creating a blood clot that may block the artery completely.
The phenomenon of “vulnerable plaque” has created new challenges in recent years for the treatment of heart disease. Unlike occlusive plaques that impede blood flow, vulnerable plaque develops within the arterial walls, but it often does so without the characteristic substantial narrowing of the arterial lumen which produces symptoms. As such, conventional methods for detecting heart disease, such as an angiogram, may not detect vulnerable plaque growth into the arterial wall. After death, an autopsy can reveal the plaque congested in arterial wall that could not have been seen otherwise with currently available medical technology.
The intrinsic histological features that may characterize a vulnerable plaque include increased lipid content, increased macrophage, foam cell and T lymphocyte content, and reduced collagen and smooth muscle cell (SMC) content. This fibroatheroma type of vulnerable plaque is often referred to as “soft,” having a large lipid pool of lipoproteins surrounded by a fibrous cap. The fibrous cap contains mostly collagen, whose reduced concentration combined with macrophage derived enzyme degradations can cause the fibrous cap of these lesions to rupture under unpredictable circumstances. When ruptured, the lipid core contents, thought to include tissue factor, contact the arterial bloodstream, causing a blood clot to form that can completely block the artery resulting in an acute coronary syndrome (ACS) event. This type of atherosclerosis is coined “vulnerable” because of the unpredictable tendency of the plaque to rupture. It is thought that hemodynamic and cardiac forces, which yield circumferential stress, shear stress, and flexion stress, may cause disruption of a fibroatheroma type of vulnerable plaque. These forces may rise as the result of simple movements, such as getting out of bed in the morning, in addition to in vivo forces related to blood flow and the beating of the heart. It is thought that plaque vulnerability in fibroatheroma types is determined primarily by factors which include: (1) size and consistency of the lipid core; (2) thickness of the fibrous cap covering the lipid core; and (3) inflammation and repair within the fibrous cap.
While the known procedures for treating plaque have gained wide acceptance and shown good efficacy for treatment of standard stenotic plaques, they may be ineffective (and possibly dangerous) when thrombotic conditions are superimposed on atherosclerotic plaques. Specifically, mechanical stresses caused by primary treatments like percutaneous transluminal coronary intervention (PTCI), such as stenting, may actually trigger release of fluids and/or solids from a vulnerable plaque into the blood stream, thereby potentially causing a coronary thrombotic occlusion. For example, rupture of the fibrous cap that overlies the thrombogenic necrotic core is presently believed to play an important role in acute ischemic events, such as stroke, transient ischemic attack, myocardial infarction, and unstable angina (Virmani R, et al. Arterioscler Thromb Vasc Biol. 20: 1262-1275 (2000)). There is evidence that fibrous cap can be ruptured during stent deployment. Human data from various sources have indicated that lipid rich and/or positively remodeled and/or echolucent lesions in sysmptomatic coronary atherosclerosis have higher likelihood for restenosis (See, for example, J. Am. Coll. Cardiol. 21(2):298-307 (1993); Am. J. Cardiol. 89(5):505 (2002); Circ. 94(12):3098-102 (1996)). Therefore, there is a need for stabilization of thin fibrous cap by building-up additional fibrous mass in a controlled manner without triggering occlusive restenosis.
The drug formulations and delivery methods of the present invention address issues of restenosis, vulnerable plaque and other disorders.

SUMMARY OF THE INVENTION

Described herein is a coating formulation for controlled release of two or more drugs for treating a medical condition. The coating is capable of a variety of combinations of release of the two or more drugs.
The release profiles of the drugs are tailored to meet various therapeutic needs. Therapeutic intervention of a drug may vary as a function of time because the mechanistic target of the drug may be a function of time. For example, anti-proliferative drugs may need to be released between 5 days to 30 days after implantation, and anti-inflammatory or antiplatelet drugs may need to be delivered acutely during the implantation procedure followed by a sustained release up to 2 months after implantation. Antimigratory drugs may need to be released within 1-4 weeks. The coating described herein, in one embodiment, is capable of providing a pulse or fast release of a first drug followed by a sustained release the first drug. The coating can further provide a fast release and/or followed by a sustained release of a second drug over a defined period.
A stent having a coating formulation defined herein can be used to treat or prevent a disorder such as atherosclerosis, thrombosis, restenosis, hemorrhage, vascular dissection or perforation, vascular aneurysm, vulnerable plaque, chronic total occlusion, claudication, anastomotic proliferation for vein and artificial grafts, bile duct obstruction, ureter obstruction, tumor obstruction, and combinations thereof.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows the in vivo percent release of everolimus and 17-beta-estradiol, further showing that it is possible to have a controlled release of everolimus and 17-beta-estradiol simultaneously (designated as “Combo”). For comparison, stents that elute only everolimus were formed to have a coating that includes an EVAL primer and a layer that includes 1:3 everolimus to EVAL polymer ratio (total solid 284 μg) (designated as “F1”).
FIG. 2 shows the comparative vascular response of the two systems, the F1 and the Combo systems, at 14 days post implant, based on analysis of histology slides. FIG. 3 shows the simultaneous release of everolimus and 17-beta-estradiol in phosphate-buffered saline (PBS)/Triton™ solution (polyoxyethylene octyl phenyl ether) (SPI Supplies, West Chester, Pa.).
FIG. 4 shows the percent lipid area, total fibrous cap thickness, and collagen type III percent area for the thin-cap fibroatheromas stented as indicated in an experimental animal model of atherosclerosis.
FIG. 5 shows the neointimal areas measured in cases of both fibrous cap rupture and intact fibrous cap for the thin-cap fibroatheromas stented as indicated in an experimental animal model of atherosclerosis.

DETAILED DESCRIPTION

In one embodiment a drug release profile or drug formulation is disclosed for the treatment of vascular disorder or related disorder. More specifically, the vascular disorder is restenosis and/or vulnerable plaque. The term “treatment” includes prevention, reduction, delay or elimination of the referred to disorder. In some embodiments, treatment also includes repairing damage caused by the disorder or the mechanical intervention, e.g., stenting. The mode of deliver of any one or the combination of the drugs can be local or systemic. Local administration can be by a stent (e.g., coated stent or biodegradable or bioabsorbable stent), a drug delivery particle or other known methods of local drug delivery. Systemic administration can be accomplished orally or parenterally, including intravascularly. For example, in one embodiment, a first drug can be delivered by a stent and the other by a catheter at the site of treatment. The delivery can be simultaneous or in sequence. In one embodiment, one of the drugs can be delivered before the other while there is some or a significant overlap between the deliveries of both. Preferably, the drug treatment is via a stent.
Therapeutic intervention of a drug may vary as a function of time because the mechanistic target of the drug may be a function of time. For example, anti-proliferative drugs may need to be released within a period of time between 3 days to 30 days after implantation, and anti-inflammatory or antiplatelet drugs may need to be delivered acutely during the implantation procedure followed by a sustained release up to 2 months after implantation. Antimigratory drugs may need to be released within 1-4 weeks.
For stent applications, the release profiles of the drugs can be tailored by using different types of coating material in mixed, bonded, or layered format; modifying the coating material; or positioning of the coating layers on the stents. Coating layers can include any combinations of a primer layer, a reservoir layer, a topcoat layer and a finishing coat layer. Any of the layers can include a biocompatible polymer as described below. For example, any of the layers, such as the barrier polymer can be a biocompatible polymer capable of controlled release of a drug by virtue of very low equilibrium water uptake. The term “very low equilibrium water uptake” can be defined as having a water permeability of less than about 1 % by weight. Generally, a barrier formed of a hydrophobic biocompatible polymer would have a very low equilibrium water uptake. Polymers fall within this category include, for example, polystyrene, poly(butyl methacrylate) (PBMA), poly(D,L-lactic acid) (PDLLA), poly(L-lactic acid) (PLLA) or poly(D,L-lactic acid-co-glycolic acid) (PDLLAGA). In one embodiment, a layer, such as the barrier polymer, can be formed of a bioabsorable polymer such as polycaprolactone (PCL), poly(ester amides) (PEA), polyhydroxyalkanoate (PHA), or poly(3-hydroxybutyrate) (PHB), vinylidene fluoride based homopolymers such as polyvinylidene fluoride (PVDF) and copolymers such as poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP). Vinylidene fluoride based polymers are commercially available under the trade name Kynar™ and Solef™.
In one embodiment, the coating can have any one or combination of a pulse, burst or sustained release profile. For example, the coating can be made to have a pulse or burst release of a drug, followed by a sustained release of the same drug. The drug can be a bioactive agent as defined below. Preferably, the drug is an anti-proliferative 40-O-(2-hydroxy)ethyl-rapamycin (known by the trade name of everolimus, available from Novartis as Certican™), estradiol such as 17-beta-estradiol, other estrogen receptors, anti-proliferative drugs, immunosuppresant drugs, anti-inflammatory drugs, anti platelet drugs, antimigratory drugs, anti-thrombotic drugs, drugs that regress plaque such as high density lipoprotein (HDL)-mimetics, agents that promotes endothelial cell growth, prohealing drugs and combinations thereof.
As used herein, the term “pulse release” generally refers to a release profile of a drug that features a sudden surge of the release rate of the drug. The release rate surge of the drug would then disappear within a period. A more detailed definition of the term can be found in Encyclopedia of Controlled Drug Delivery, Edith Mathiowitz, Ed., Culinary and Hospitality Industry Publications Services.
In some embodiments, the term “fast release” refers to a release profile of a drug that features a release rate in the range between about 15 μg and about 40 μg per day (typically for one to three days) (or between about 45 μg and about 120 μg in three days) for a 18 mm stent, about 10 μg to about 27 μg per day (typically for one to three days) for a 13 mm stent, and about 6 (6.7) μg to about 17.2 μg per day (typically for one to three days) for a 8 mm stent. Equivalent profiles can be derived by one having ordinary skill in the art for stents having other sizes. The term “fast release” is used interchangeably with the term “burst release.”
As used herein, the term “sustained release” generally refers to a release profile of a drug that can include zero-order release, exponential decay, step-function release or other release profiles that carry over a period of time, for example, ranging from several days to several weeks or years. The terms “zero-order release”, “exponential decay” and “step-function release” as well as other sustained release profiles are well known in the art (see, for example, Encyclopedia of Controlled Drug Delivery, Edith Mathiowitz, Ed., Culinary and Hospitality Industry Publications Services). In some embodiments, sustained release refers to 2 to 15 μg per day for a selected number of days or weeks.
In another embodiment, the coating may include two or more drugs. One of the drugs or both drugs can have any one or combination of the pulsed, burst or sustained delivery profile. The coating can have a delivery profile that features a burst delivery of one or more drugs together with a sustained delivery of the one or more drugs. In one embodiment, the coating can be made to have a profile of a burst release of a first drug and sustained release of the first drug and a second drug. Alternatively, the coating can be made to have a burst release of a first and a second drug followed by a sustained release of the first and the second drug. The release rate of the drugs can be tailored by coating concentration of a drug and the equilibrium water uptake of the barrier if the barrier is formed of a hydrophobic, nonabsorable polymer or the absorption rate if the barrier is formed of an absorbable polymer.
For example, the coating can have a burst release in the first three days after implantation of an immunosuppresant, followed by a sustained release of the immunosuppresant thereafter or a sustained release of an anti-inflammatory drug or an antiplatelet drug over a period of two months.
In another embodiment of the present invention, a coating can be made to provide a release profile that includes a pulse release of one or more drugs and optionally a sustained release of the same or different drugs. The art of formulation to provide a pulsed release profile is well developed (see, for example, Encyclopedia of Controlled Drug Delivery, Edith Mathiowitz, Ed., Culinary and Hospitality Industry Publications Services). In one example, the upper most stent coating or surface thereof can be concentrated with the drug. In another example, a drug can be encapsulated within microcapsules. The degradation of the microcapsule wall can generate a pulsed release of the drug.
In one embodiment, a coating providing a pulse release profile can be made from nano or microparticulate drug loaded particles (DrugP) formed of a drug encapsulated within a degradable polymer. The drugP can be nanoparticles or microparticles of the drugP having a size ranging for example, from about 0.5 nm to about 1000 nm, or from about 1 μm to about 100 μm. Representative drug particles can have a size of about 0.5 nm, about 2 nm, about 5 nm, about 10 nm, about 20 nm, about 50 nm, about 75 nm, about 100 nm, about 200 nm, about 500 nm, about 750 nm, about 1000 nm, about 2 μm, about 5 μm, about 10 μm, about 20 μm, about 50 μm, about 75 μm, or about 100 μm.
The drugs forming the drugP can be any one or more bioactive agents described below. Representative drugs can be anti-proliferative everolimus, estradiol (e.g., 17-beta-estradiol), other estrogen receptors, anti-proliferative drugs, immunosuppresant drugs, anti-inflammatory drugs, anti platelet drugs, antimigratory drugs, anti-thrombotic drugs, agents that promotes endothelial cell growth, drugs that regress plaque such as high density lipoprotein (HDL)-mimetics, prohealing drugs and combinations thereof. The encapsulating polymer can be any degradable biocompatible polymer having a range of hydrolysis rate. Representative polymers include, but are not limited to, poly(glycolic acid) (PGA), poly(D,L-lactic acid) (DLPLA), polyhydroxyalkanoates (PHA), poly(ester amides) (PEA), and polyether esters such as poly(butylene terephthalate)/poly(ethylene glycol) (PBT/PEG). The drugP can be formed by emulsion methods known in the art (see, for example, Hans Mollet, Formulation Technology: Emulsions, Suspensions, Solid Forms, Wiley-VCH, 2001). The drugP can be suspended in a solution of a polymer and optionally the drug forming the drugP particles and then sprayed on the stent. Hydrolysis of the encapsulating polymer will allow the drug to be released from the drugP. The drugP having a size ranging from about 0.5 nm to 2 nm or from about 1 μm to 4 μm would favor surface degradation over bulk degradation. A population distribution of drugP can result in the drug release in the coating matrix at times that appear as a pulsed dosing from the coating matrix impressed on a background release of the same drug or a different drug if a drug is optionally included in the coating solution in which the drugP is suspended. The background release can be the same drug, a different drug or no drug at all. The background release of drug can be tailored to have a different profile as well. In one embodiment, the background release is sustained release.
In a further aspect of the present invention, the coating can be made to simultaneously release an agent that reduces smooth muscle cell migration and/or proliferation and an agent that promotes endothelial cell growth. Simultaneous delivery means that there is at least some overlap in the release of the drug. Under this embodiment, at least one of the drugs can be released first such as by pulsed, burst, or sustained delivery so long as there is an overlap in delivery with the second drug. Smooth muscle cell proliferation has been identified as a cause of restenosis, and endothelial cell growth contributes to vessel healing (see, for example, Chandrasekar, et al., J. Am. Coll..Cardiol. 38: 1570-6 (2001)). A combination of an anti-proliferative agent and an agent that promotes endothelial cell growth allows one to treat restenosis through different channels and may have a synergistic effect on ameliorating restenosis.
Coatings capable of simultaneously releasing an anti-proliferative agent and an agent that promotes endothelial cell growth can have a variety of configurations. For example, the coating can have a layer that comprises a mixture of the two agents or have two layers, each of which comprises a polymer and either the anti-proliferative agent or the agent that promotes endothelial cell growth.
In one embodiment, a composition containing a drug such as drugP particles described above can be formed from a polymer and one of the anti-proliferative agent and the agent that promotes endothelial cell growth. The composition such as the drugP particles can be suspended in a solution of the polymer and the other agent of the anti-proliferative agent or the agent that promotes endothelial cell growth and then coated on to a stent. The resultant coating would provide a pulsed release of one agent and a background release of the other agent.
The ani-proliferative agent useful for forming the various formulations described herein includes any anti-proliferative agents that reduce smooth muscle cell migration and/or proliferation. In one embodiment, the ani-proliferative agent is rapamycin, rapamycin derivatives, paclitaxel, docetaxel, 40-O-(3-hydroxy)propyl-rapamycin, 40-O-[2-(2-hydroxy)ethoxy]ethyl-rapamycin, and 40-O-tetrazole-rapamycin, ABT-578, everolimus and combinations thereof.
The agent that promotes endothelial cell growth useful for forming the various formulations described herein can be any agent that provides beneficial effect on endothelial cell growth. Exemplary agents promoting endothelial cell growth include, for example, vascular endothelial growth factor (VEGF), estradiol such as 17-beta-estradiol, agents that do not inhibit endothelial cell growth, and combinations thereof. Preferably, the endothelial cell growth promoting agent is estradiol, more preferably 17-beta-estradiol.
In one embodiment, the ani-proliferative agent is everolimus and the endothelial cell growth promoting agent is 17-beta-estradiol, and the simultaneous release of everolimus and 17-beta-estradiol can be achieved by three-layer coating on a stent. The first layer can be only a primer layer, the second layer can include a blend of everolimus and a polymer such as an EVAL polymer, and the third layer can have a blend of 17-beta-estradiol and a polymer such as an EVAL polymer.
In a further embodiment, a coating can be formed to include (1) a first drug that can be one of rapamycin, rapamycine derivatives, paclitaxel, docetaxel, 40-O-(3-hydroxy)propyl-rapamycin, 40-O-[2-(2-hydroxy)ethoxy]ethyl-rapamycin, and 40-O-tetrazole-rapamycin, ABT-578, everolimus and combinations thereof, (2) a second drug that can be one of vascular endothelial growth factor (VEGF), estradiol such as 17-beta-estradiol, agents that do not inhibit endothelial cell growth, and combinations thereof. The first and second drugs can have any of the aforementioned release profiles such as the first drug can have a pulse, burst and/or sustained release profile, and the second drug can-have a pulse, burst and/or sustained release profile. The first drug can have a burst release followed by sustained release while the second drug has a sustained release. Alternatively, the second drug can have a burst release followed by sustained release while the first drug has a sustained release. Preferably, the first drug is everolimus and the second drug is 17-beta-estradiol.
The coating can have different constructs. For example, the coating can have a first layer that comprises a first drug and a first polymer, and a second layer that comprises a second drug and a second polymer. The first polymer and the second polymer can be same or different. In addition, the first layer and the second layer can have a drug/polymer ratio between 1/99 and 99/1, e.g., a ratio between 10/90 and 90/10.
FIGS. 1 and 2 show an embodiment of the coatings described herein, which allows simultaneous release of both everolimus and 17-beta-estradiol. FIG. 1 shows porcine in vivo release profile of everolimus and 17-beta-estradiol in which “Combo” describes the stents that simultaneously release everolimus and 17-beta-estradiol and “F1” describes the stents that release only everolimus. The Combo stents include an EVAL primer layer and a layer of mixture of 1:3 everolimus to EVAL polymer ratio (total solid 284 μg) under a layer of mixture of 1:3 17-beta-estradiol to EVAL polymer ratio (total solid 372 μg). The F1 stents include an EVAL primer layer under a layer of a mixture of 1:3 everolimus to EVAL polymer ratio (total solid 284 μg). Vascular responses to the implants of F1 and Combo stents are shown in FIG. 2, which shows that the stent that simultaneously releases everolimus and 17-beta-estradiol can result in lower chances of peristrut thrombosis and higher chances of re-endothelialization as compared to the stent that releases only everolimus. Foreign body response (FBR) and inflammation were generally the same.
FIG. 3 shows another embodiment of the present invention, which is simultaneous fractional release of everolimus and 17-beta-estradiol in Solef™ in phosphate-buffered saline (PBS)/Triton™ solution (polyoxyethylene octyl phenyl ether) (SPI Supplies, West Chester, Pa.). The stents have a PBMA primer layer and a layer of everolimus in PVDF under a layer of 17-beta-estradiol in PVDF. The designation of “Design 1” and that of “Design 2” in FIG. 3 correspond to two different stents of the same configuration with different polymer/drug ratios.
The coatings described above can be designed to have a topcoat or a finish coat that is capable of promoting accelerated-healing. This topcoat or finish coat can be made non-inflammatory and/or non-fouling. Non-inflammatory is defined as preventing inflammation or reducing inflammation to an acceptable degree. Non-fouling or anti-fouling is defined as preventing, delaying or reducing the amount of formation of protein build-up caused by the body's reaction to foreign material. The topcoat or finish coat can be combined with a tailored release of a drug or drugs at the finalcoat and/or the drug reservoir layers to further modulate the plaque stabilization and controlled healing. The accelerated-healing topcoat can be formed of one of polyester amide, Silk-elastin, elastin-epitoped supramolecular assembly of peptide amiphile or combinations thereof. The accelerated-healing topcoat can be made non-inflammatory, non-fouling by including a non-inflammatory, non-fouling material such as PolyActive™, PEG, hyaluronic acid and its derivatives, and heparin and its derivatives that can be a fragment heparin such as pentasaccharide, a derivative heparin or a complexed heparin. Heparin derivatives can be any functional or structural variation of heparin. Representative variations include alkali metal or alkaline—earth metal salts of heparin, such as sodium heparin (e.g., hepsal or pularin), potassium heparin (e.g., clarin), lithium heparin, calcium heparin (e.g., calciparine), magnesium heparin (e.g., cutheparine), low molecular weight heparin (e.g., ardeparin sodium) with a molecular weight of from about 4,000 to about 5,000 Daltons and high affinity heparin (see, e.g., Scully, et al., Biochem. J. 262:651-658 (1989)). Other examples include heparin sulfate, heparinoids, heparin based compounds and heparin having a hydrophobic counter-ion such as tridodecylmethylammonium and benzalkonium.
The coatings described herein can optionally have one or more bioactive agents, which may be the same or different from the drugs described in the above. Examples of such agents include synthetic inorganic and organic compounds, proteins and peptides, polysaccharides and other sugars, lipids, and DNA and RNA nucleic acid sequences having therapeutic, prophylactic or diagnostic activities. Nucleic acid sequences include genes, antisense molecules which bind to complementary DNA to inhibit transcription, and ribozymes. Other examples of drugs include antibodies, receptor ligands, and enzymes, adhesion peptides, oligosaccharides, blood clotting factors, inhibitors or clot dissolving agents such as streptokinase and tissue plasminogen activator, antigens for immunization, hormones and growth factors, oligonucleotides such as antisense oligonucleotides and ribozymes and retroviral vectors for use in gene therapy. Such agents can also include a prohealing drug that imparts a benign neointimal response characterized by controlled proliferation of smooth muscle cells and controlled deposition of extracellular matrix with complete luminal coverage by phenotypically functional (similar to uninjured, healthy intima) and morphologically normal (similar to uninjured, healthy intima) endothelial cells. Such agents can also fall under the genus of antineoplastic, cytostatic, anti-inflammatory, antiplatelet, anticoagulant, antifibrin, antithrombin, antimitotic, antibiotic, antiallergic and antioxidant substances. Examples of such antineoplastics and/or antimitotics include paclitaxel (e.g. TAXOL® by Bristol-Myers Squibb Co., Stamford, Conn.), docetaxel (e.g. Taxotere®, from Aventis S. A., Frankfurt, Germany) methotrexate, azathioprine, vincristine, vinblastine, fluorouracil, doxorubicin hydrochloride (e.g. Adriamycin® from Pharmacia & Upjohn, Peapack N.J.), and mitomycin (e.g. Mutamycin® from Bristol-Myers Squibb Co., Stamford, Conn.). Examples of such antiplatelets, anticoagulants, antifibrin, and antithrombins include heparinoids, hirudin, recombinant hirudin, argatroban, forskolin, vapiprost, prostacyclin and prostacyclin analogues, dextran, D-phe-pro-arg-chloromethylketone (synthetic antithrombin), dipyridamole, glycoprotein IIb/IIIa platelet membrane receptor antagonist, antibody, and thrombin inhibitors such as Angiomax ä (Biogen, Inc., Cambridge, Mass.). Examples of cytostatic agents include angiopeptin, angiotensin converting enzyme inhibitors such as captopril (e.g. Capoten® and Capozide® from Bristol-Myers Squibb Co., Stamford, Conn.), cilazapril or lisinopril (e.g. Prinivil® and Prinzide® from Merck & Co., Inc., Whitehouse Station, N.J.), actinomycin D, or derivatives and analogs thereof (manufactured by Sigma-Aldrich 1001 West Saint Paul Avenue, Milwaukee, Wis. 53233; or COSMEGEN available from Merck). Synonyms of actinomycin D include dactinomycin, actinomycin IV, actinomycin I₁, actinomycin X₁, and actinomycin C₁. Other drugs include calcium channel blockers (such as nifedipine), colchicine, fibroblast growth factor (FGF) antagonists, fish oil (omega 3-fatty acid), histamine antagonists, lovastatin (an inhibitor of HMG-CoA reductase, a cholesterol lowering drug, brand name Mevacor® from Merck & Co., Inc., Whitehouse Station, N.J.), monoclonal antibodies (such as those specific for Platelet-Derived Growth Factor (PDGF) receptors), nitroprusside, phosphodiesterase inhibitors, prostaglandin inhibitors, suramin, serotonin blockers, steroids, thioprotease inhibitors, triazolopyrimidine (a PDGF antagonist), and nitric oxide. An example of an antiallergic agent is permirolast potassium.
Other therapeutic substances or agents which may be appropriate include alpha-interferon, genetically engineered epithelial cells, antibodies such as CD-34 antibody, abciximab (REOPRO), and progenitor cell capturing antibody, prohealing drugs that promotes controlled proliferation of muscle cells with a normal and physiologically benign composition and synthesis products, enzymes, anti-inflammatory agents, antivirals, anticancer drugs, anticoagulant agents, free radical scavengers, steroidal anti-inflammatory agents, non-steroidal anti-inflammatory agents, antibiotics, nitric oxide donors, super oxide dismutases, super oxide dismutases mimics, 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl (4-amino-TEMPO), dexamethasone, clobetasol, aspirin, pro-drugs thereof, co-drugs thereof, and a combination thereof. The foregoing substances are listed by way of example and are not meant to be limiting. Other active agents which are currently available or that may be developed in the future are equally applicable.
The stent coating formulation provided herein can include any biocompatible polymer. Representative examples of polymers that can be used to coat an implantable device in accordance with the present invention include, but are not limited to, poly(ester amide), polyhydroxyalkanoates (PHA) such as poly(3-hydroxyalkanoates), e.g., poly(3-hydroxypropanoate), poly(3-hydroxybutyrate), poly(3-hydroxyvalerate), poly(3-hydroxyhexanoate), poly(3-hydroxyheptanoate) or poly(3-hydroxyoctanoate), poly(4-hydroxyalknaote), e.g., poly(4-hydroxybutyrate), poly(4-hydroxyvalerate), poly(4-hydroxyhexanote), poly(4-hydroxyheptanoate), poly(4-hydroxyoctanoate) and copolymers including any of the 3-hydroxyalkanoate or 4-hydroxyalkanoate monomers described herein or blends thereof, polyesters, poly(D,L-lactide), poly(L-lactide), polyglycolide, poly(D,L-lactide-co-glycolide), poly(L-lactide-co-glycolide), polycaprolactone, poly(lactide-co-caprolactone), poly(glycolide-co-caprolactone), poly(dioxanone), poly(ortho esters), poly(anhydrides), poly(tyrosine carbonates) and derivatives thereof, poly(tyrosine ester) and derivatives thereof, poly(imino carbonates), poly(glycolic acid-co-trimethylene carbonate), polyphosphoester, polyphosphoester urethane, poly(amino acids), polycyanoacrylates, poly(trimethylene carbonate), poly(iminocarbonate), polyurethanes, polyphosphazenes, silicones, polyesters, polyolefins, polyisobutylene and ethylene-alphaolefin copolymers, acrylic polymers and copolymers, vinyl halide polymers and copolymers, such as polyvinyl chloride, polyvinyl ethers, such as polyvinyl methyl ether, polyvinylidene halides, such as vinylidene fluoride based homopolymer (PVDF) and copolymers such as poly(yinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) known as Solef™ or Kynar™ polymers and polyvinylidene chloride, polyfluoroalkenes such as tetrafluoroethylene (Teflon™), polyacrylonitrile, polyvinyl ketones, polyvinyl aromatics, such as polystyrene, polyvinyl esters, such as polyvinyl acetate, copolymers of vinyl monomers with each other and olefins, such as ethylene-methyl methacrylate copolymers, acrylonitrile-styrene copolymers, ABS resins, and ethylene-vinyl acetate copolymers, polyamides, such as Nylon 66 and polycaprolactam, alkyd resins, polycarbonates, polyoxymethylenes, polyimides, polyethers, poly(glyceryl sebacate), poly(propylene fumarate), epoxy resins, polyurethanes, rayon, rayon-triacetate, cellulose acetate, cellulose butyrate, cellulose acetate butyrate, cellophane, cellulose nitrate, cellulose propionate, cellulose ethers, carboxymethyl cellulose, polyethers such as poly(ethylene glycol) (PEG), copoly(ether esters) (e.g. PEO/PLA); polyalkylene oxides such as poly(ethylene oxide), poly(propylene oxide), polyalkylene oxalates, polyphosphazenes, phosphoryl choline, choline, poly(aspirin), polymers and co-polymers of hydroxyl bearing monomers such as 2-hydroxyethyl methacrylate (HEMA), hydroxypropyl methacrylate (HPMA), hydroxypropylmethacrylamide, PEG acrylate (PEGA), PEG methacrylate, 2-methacryloyloxyethylphosphorylcholine (MPC) and n-vinyl pyrrolidone (VP), carboxylic acid bearing monomers such as methacrylic acid (MA), acrylic acid (AA), alkoxymethacrylate, alkoxyacrylate, and 3-trimethylsilylpropyl methacrylate (TMSPMA), poly(styrene-isoprene-styrene)-PEG (SIS-PEG), polystyrene-PEG, polyisobutylene-PEG, polycaprolactone-PEG (PCL-PEG), PLA-PEG, poly(methyl methacrylate)-PEG (PMMA-PEG), polydimethylsiloxane-co-PEG (PDMS-PEG), poly(vinylidene fluoride)-PEG (PVDF-PEG), PLURONIC™ surfactants (polypropylene oxide-co-polyethylene glycol), poly(tetramethylene glycol), hydroxy functional poly(vinyl pyrrolidone), biomolecules such as collagen, chitosan, alginate, fibrin, fibrinogen, starch, collagen, dextran, dextrin, fragments and derivatives of hyaluronic acid, heparin, fragments and derivatives of heparin, glycosamino glycan (GAG), GAG derivatives, polysaccharide, elastin, alginate, and combinations thereof.
As used herein, the terms poly(D,L-lactide) (PDLL), poly(L-lactide) (PLL), poly(D,L-lactide-co-glycolide) (PDLLG), and poly(L-lactide-co-glycolide) (PLLG) are used interchangeably with the terms poly(D,L-lactic acid) (PDLLA), poly(L-lactic acid) (PLLA), poly(D,L-lactic acid-co-glycolic acid) (PDLLAGA), and poly(L-lactic acid-co-glycolic acid) (PLLAGA), respectively.
Although embodiments of local drug delivery has been described in reference to a stent (balloon or self expandable), other medical substrates that can be implanted in a human or veterinary patient are also applicable with the embodiments of the invention. Examples of such implantable devices include stent-grafts, grafts (e.g., aortic grafts), artificial heart valves, cerebrospinal fluid shunts, pacemaker electrodes, and endocardial leads (e.g., FINELINE and ENDOTAK, available from Guidant Corporation, Santa Clara, Calif.). The underlying structure of the device can be of virtually any design. The device can be made of a metallic material or an alloy such as, but not limited to, cobalt chromium alloy (ELGILOY), stainless steel (316L), high nitrogen stainless steel, e.g., BIODUR 108, cobalt chrome alloy L-605, “MP35N,” “MP20N,” ELASTINITE (Nitinol), tantalum, nickel-titanium alloy, platinum-iridium alloy, gold, magnesium, or combinations thereof. “MP35N” and “MP20N” are trade names for alloys of cobalt, nickel, chromium and molybdenum available from Standard Press Steel Co., Jenkintown, Pa. “MP35N” consists of 35% cobalt, 35% nickel, 20% chromium, and 10% molybdenum. “MP20N” consists of 50% cobalt, 20% nickel, 20% chromium, and 10% molybdenum. Devices made from bioabsorbable or biostable polymers could-also be used with the embodiments of the present invention.
In accordance with embodiments of the invention, a coating of the various described embodiments can be formed on an implantable device or prosthesis, e.g., a stent. For coatings including one or more active agents, the agent will retain on the medical device such as a stent during delivery and expansion of the device, and released at a desired rate and for a predetermined duration of time at the site of implantation. Preferably, the medical device is a stent. A stent having the above-described coating is useful for a variety of medical procedures, including, by way of example, treatment of obstructions caused by tumors in bile ducts, esophagus, trachea/bronchi and other biological passageways. A stent having the above-described coating is particularly useful for treating atherosclerosis, thrombosis, restenosis, hemorrhage, vascular dissection or perforation, vascular aneurysm, vulnerable plaque, chronic total occlusion, claudication, anastomotic proliferation for vein and artificial grafts, bile duct obstruction, ureter obstruction, tumor obstruction, and combinations thereof. Stents may be placed in a wide array of blood vessels, both arteries and veins. Representative examples of sites include the iliac, renal, and coronary arteries.
For implantation of a stent, an angiogram is first performed to determine the appropriate positioning for stent therapy. An angiogram is typically accomplished by injecting a radiopaque contrasting agent through a catheter inserted into an artery or vein as an x-ray is taken. A guidewire is then advanced through the lesion or proposed site of treatment. Over the guidewire is passed a delivery catheter which allows a stent in its collapsed configuration to be inserted into the passageway. The delivery catheter is inserted either percutaneously or by surgery into the femoral artery, brachial artery, femoral vein, or brachial vein, and advanced into the appropriate blood vessel by steering the catheter through the vascular system under fluoroscopic guidance. A stent having the above-described coating may then be expanded at the desired area of treatment. A post-insertion angiogram may also be utilized to confirm appropriate positioning.

EXAMPLES

The embodiments of the present invention will be illustrated by the following set forth examples. All parameters and data are not to be construed to unduly limit the scope of the embodiments of the invention.

Examples 1-2

Drug-Eluting Coatings Having a Fast and Slow Release of Estradiol from 13 mm Penta™ Stents

Penta™ stents (available from Guidant) can be coated according to the configurations defined in Table 1 to provide a fast release or a slow release of estradiol.

TABLE 1


Coating configurations of Penta ™ stents for delivery of estradiol

Reservoir

Topcoat

Primer

Drug

Solid

Topcoat

Release

Polymer

Primer

Polymer

Content

Target

Polymer

Target

1

Fast

EVAL

40 μg

A

EVAL

300 μg

600 mg

B

EVAL

100

μg

C

2

Slow

EVAL

40 μg

A

EVAL

300 μg

600 mg

B

PBMA

40

μg

D

A: 3% EVAL/72% DMAC/25% ethanol.

B: 2% EVAL/1% Estradiol/77% DMAC/20% pentane.

C: 4% EVAL/76% DMAC/20% pentane.

D: 1% PBMA/43% Techspray ™/6% acetone/50% xylene.

Examples 3-4

Drug-Eluting Coatings Having a Fast and Slow Release of Everolimus

Penta™ stents can be coated according to the configurations defined in Table 2 to provide a fast release or a slow release of everolimus.

TABLE 2


Coating configurations of Penta ™ stents for delivery of everolimus

Reservoir

Topcoat

Primer

Drug

Solid

Topcoat

Release

Polymer

Primer

Polymer

Content

Target

Polymer

Target

3

Fast

EVAL

40 μg

A

EVAL

385 mg

615 μg

B

EVAL

40

μg

C

4

Slow

EVAL

40 μg

A

EVAL

273 mg

478 μg

B

PBMA

189

μg

C

A: 3% EVAL/72% DMAC/25% ethanol.

B: 2% EVAL/1% everolimus/77% DMAC/20% pentane.

C: 4% EVAL/76% DMAC/20% pentane

Example 5

Preclinical Study of Drug-Delivery Implants

The following preclinical data are representative results from the drug-eluting stent (DES) implants of everolimus and 17-beta-estradiol in a hypercholesterolemic rabbit model of human thin-cap fibroatheroma (TCFA). The MULTI-LINK Penta™ 13 mm was the platform for all DES and metallic stents. Both a slow release and fast release formulation of each drug were tested and the results were evaluated at 28 days. In both FIGS. 4 and 5, the test results concerning the slow release formulation were labeled with “s”, the test results concerning the fast release formulation were labeled with “f”, and the test results data concerning a formulation having both a slow and a fast release of an agent are labeled with “s+f.”
As shown in FIG. 4, compared to the unstented (de novo) TCFAs, both formulations of beta estradiol reduced the percent lipid area and increased the total fibrous cap thickness. Compared to TCFAs treated with metallic stents, both formulations of beta estradiol reduced the percent lipid area and decreased the total fibrous cap thickness. The slow release formulation resulted in a smaller total fibrous cap thickness but with a larger percent lipid area compared to the fast release formulation. Compared to the metallic stents, both formulations of everolimus reduced the percent lipid area and decreased the total fibrous cap thickness. As with the beta-estradiol, the slow release formulation of everolimus yielded a smaller total fibrous cap thickness but with a larger percent lipid area compared to the fast release formulation. Together, these results illustrate that on de novo TCFAs, both beta-estradiol and everolimus drug-delivery stent reduce percent lipid area and increase total cap thickness. The increase in cap thickness in the drug-delivery stent arms was more controlled than the increase observed with the metallic stents. In particular, the slow release formulations may be effective at stabilizing TCFA by reducing percent lipid area while reducing the chance of restenosis as a result of the attenuated fibrous cap thicknening. The increased expression of newer collagen type III suggests a reparative process post-stenting, such that the overall increase in interstitial collagen imparts increased structural integrity to the fibrous cap, thereby providing a possible mechanism for stabilizing the TCFA. In this respect, both drug-delivery stent arms were as effective as metallic stents in this animal model of atherosclerosis.
FIG. 5 shows the neointimal areas measured in cases of both fibrous cap rupture and intact fibrous cap for all stent arms in this animal model. These preclinical results have clinical significance in that with current interventional devices and procedures, the fibrous cap is likely to be ruptured during stent deployment. In each stent arm, rupture of the fibrous cap (hatched areas) by stent struts resulted in increased neointimal formation as compared to sections where the fibrous cap remained intact (solid areas). This response of increased neointimal formation in the case of fibrous cap rupture was attenuated, but not completely eliminated, by drug-delivery stent at 28 days. The lowest neointimal areas were obtained in the everolimus arms. For the full range of intact and ruptured fibrous caps, the slow release everolimus yielded similar results as compared to the fast release everolimus.

Example 6

Simultaneous Release of Everolimus and 17-beta-estradiol

Onto Vision 12 mm small stents (available from Guidant) can be coated according to the following configurations. An auto coater can be used to coat the abluminal surface of the stent.
Configuration A
Drug coating: coating with 200 μg of poly(D,L-lactic acid) (PDLLA)/estradiol, from 4.8% poly(D,L-lactic acid) (PDLLA), 4.8% estradiol, and 90.4% acetone, by 3 passes, drying at 35° C. for 8 hours, and then coating with 200 μg of DL-PLA/everolimus, from 4.8% DL-PLA, 4.8% everolimus, and 90.4% acetone, coating by 3 passes, drying at 35° C. for 8 hours.
Configuration B
Primer: coating with 80 μg PDLLA, using one pass coating, from 9.6% DL-PLA in acetone solution, baking at 120° C. for 1 hr; and
Drug coating: coating with 200 μg of PDLLA/estradiol, from 4.8% PDLLA, 4.8% estradiol, and 90.4% acetone, by 3 passes, drying at 35° C. for 8 hours, and then coating with 200 μg of PDLLA/everolimus, from 4.8% PDLLA, 4.8% everolimus, and 90.4% acetone, by 3 passes, drying at 35° C. for 8 hours.
Configuration C
Primer: coating with 80 μg PDLLA, using one pass coating, from 9.6% PDLLA in acetone solution, baking at 120° C. for 1 hr;
Drug: coating with 200 μg of estradiol, from 5% estradiol solution in acetone, using 3 pass coating;
Inter coat: coating with 80 μg PDLLA, using one pass coating, from 9.6% PDLLA in acetone solution, baking at 35° C. for 1 hr; and
Drug coat: coating with 200 μg of PDLLA/everolimus, from 4.8% PDLLA, 4.8% everolimus, and 90.4% acetone, by 3 passes, drying at 35° C. for 8 hours.
Configuration D
Primer: coated with 80 μg PDLLA, using one pass coating, from 9.6% PDLLA in acetone solution, baking at 120° C. for 1 hr;
PDLLA/drug: coating with 300 μg of PDLLA/estradiol, from 4.8% PDLLA, 4.8% estradiol, and 90.4% acetone, by 4 passes, drying at 35° C. for 8 hours;
Pure everolimus: coating with 100 μg everolimus, from 10% drug solution in MEK (methylethylketone), by 2 passes, baking at 50° C. for 1 hr; and
Top coat: coating with 100 μg Polyactive™, using one pass coating, from a 5% solution of 5% Polyactive™, 76% chloroform, and 19% 1,1,2-trichloroethane.
Configuration E
Primer: coating with 80 μg PDLLA, using one pass coating, from 9.6% PDLLA in acetone solution, and baking at 120° C. for 1 hr;
Poly(ester amide) (PEA)/estradiol: coating with 200 μg of PEA/estradiol, from 5% PEA, 5% estradiol, 72% chloroform, and 18% 1,1,2-trichloroethane, by 3 passes, drying at 35° C. for 8 hours;
PEA/everolimus: coating with 200 μg of PEA/everolimus, from a solution that includes 5% PEA, 5% everolimus, 72% chloroform, and 18% 1,1,2-trichloroethane, by 3 passes, and drying at 35° C. for 8 hours; and
Top coat: coating with 100 μg Polyactive™, using one pass coating, from a 5% solution of 5% Polyactive™ in 76% chloroform, and 19% 1,1,2-trichloroethane.
While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications can be made without departing from this invention in its broader aspects. Therefore, the appended claims are to encompass within their scope all such changes and modifications as fall within the true spirit and scope of this invention.

Claims

1. A drug-delivery system, comprising an effective amount of everolimus, or derivatives thereof, and an effective amount of estradiol for the treatment or prevention of a vascular disorder or a related disorder.

2. The drug-delivery system of claim 1, wherein estradiol is 17-beta-estradiol.

3. The drug-delivery system of claim 1, wherein the system is a stent.

4. The drug-delivery system of claim 1, wherein the disorder is restenosis.

5. The drug-delivery system of claim 1, wherein the disorder is vulnerable plaque.

6. The drug-delivery system of claim 1, wherein the system is a polymer or a polymeric coating.

7. A method of treating restenosis of a blood vessel comprising administering to a patient an effective amount of everolimus, rapamycin, or derivatives of everolimus or rapamycin and an effective amount of estradiol, wherein the combination is for treatment or prevention of the vascular disorder.

8. The method of claim 7, wherein estradiol is 17-beta-estradiol.

9. The method of claim 7, wherein the combination of the drugs are administered by a drug-delivery stent.

10. A method of treating vulnerable plaque of a blood vessel comprising administering to a patient an effective amount of everolimus, rapamycin, or derivatives of everolimus or rapamycin and an effective amount of estradiol, wherein the combination is for treatment or prevention of the vascular disorder.

11. The method of claim 10, wherein estradiol is 17-beta-estradiol.

12. The method of claim 10, wherein the combination of the drugs are administered by a drug-delivery stent.

13. A drug-delivery stent comprising at least a drug selected from the group consisting of anti-proliferative drugs, immunosuppresant drugs, anti-inflammatory drugs, anti platelet drugs, antimigratory drugs, anti-thrombotic drugs, drugs that regress plaque, high density lipoprotein (HDL)-mimetics, prohealing drugs and combinations thereof; wherein the stent has a release profile that includes one or a combination of pulsed, burst and sustained release profile.

14. The drug-delivery stent of claim 13,

wherein the anti-proliferative drugs have a sustained release over a period up to 30 days;

wherein the anti-inflammatory drugs and the anti platelet drugs have a sustained release over a period up to 2 months; and

wherein the antimigratory drugs have a sustained release over a period up to 4 weeks.

15. The drug-delivery stent of claim 13, wherein a combination of the anti-proliferative and anti-inflammatory is used.

16. The drug-delivery stent of claim 13, further comprising an additional drug selected from the group consisting of estradiol, idoxifene, and a combination thereof.

17. The drug-delivery stent of claim 13, wherein the anti-proliferative is everolimus.

18. The drug-delivery stent of claim 17, wherein everolimus is released at a rate of about 6 to 40 μg per day for at least one day after implantation and a rate of about 2 to 15 μg per day thereafter for a selected number of days.

19. The drug-delivery stent of claim 17, wherein everolimus is released at a rate of about 45 μg to 120 μg within the first 3 days after implantation followed by a release at a rate of about 2 to 15 μg per day for a selected number of days.

20. A drug-delivery stent comprising a first drug that reduces smooth muscle cell proliferation and a second drug that promotes endothelial cell growth, wherein the drug-delivery stent is capable of simultaneously releasing the first drug and the second drug.

21. The drug-delivery stent of claim 20, wherein the first drug is everolimus and the second drug is estradiol, 17-beta-estradiol or idoxifene.

22. The drug-delivery stent of claim 20, comprising:

a first layer that comprises the first drug and a first polymer, and a second layer that comprises the second drug and a second polymer, wherein the first polymer and the second polymer can be the same or different.

23. A method of treating a disorder in a patient comprising implanting in the patient the stent of claim 13, wherein the disorder is selected from the group consisting of atherosclerosis, thrombosis, restenosis, hemorrhage, vascular dissection or perforation, vascular aneurysm, vulnerable plaque, chronic total occlusion, claudication, anastomotic proliferation for vein and artificial grafts, bile duct obstruction, ureter obstruction, tumor obstruction, and combinations thereof.

24. A method of treating a disorder in a patient comprising administering to the patient a formulation of claim 20, wherein the disorder is selected from the group consisting of atherosclerosis, thrombosis, restenosis, hemorrhage, vascular dissection or perforation, vascular aneurysm, vulnerable plaque, chronic total occlusion, claudication, anastomotic proliferation for vein and artificial grafts, bile duct obstruction, ureter obstruction, tumor obstruction, and combinations thereof.

25. A method of treating a disorder in a patient comprising administering to the patient a formulation of claim 21, wherein the disorder is selected from the group consisting of atherosclerosis, thrombosis, restenosis, hemorrhage, vascular dissection or perforation, vascular aneurysm, vulnerable plaque, chronic total occlusion, claudication, anastomotic proliferation for vein and artificial grafts, bile duct obstruction, ureter obstruction, tumor obstruction, and combinations thereof.