WO2012083594A1 - Biodegradable drug eluting stent and methodsof making the same. - Google Patents

Biodegradable drug eluting stent and methodsof making the same. Download PDF

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Publication number
WO2012083594A1
WO2012083594A1 PCT/CN2011/002168 CN2011002168W WO2012083594A1 WO 2012083594 A1 WO2012083594 A1 WO 2012083594A1 CN 2011002168 W CN2011002168 W CN 2011002168W WO 2012083594 A1 WO2012083594 A1 WO 2012083594A1
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Prior art keywords
stent
drug
polymer
agent
anti
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PCT/CN2011/002168
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French (fr)
Inventor
Tiangen WU
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Dongguan Tiantianxiangshang Medical Technology Co., Ltd
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Publication of WO2012083594A1 publication Critical patent/WO2012083594A1/en

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    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/82Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2210/00Particular material properties of prostheses classified in groups A61F2/00 - A61F2/26 or A61F2/82 or A61F9/00 or A61F11/00 or subgroups thereof
    • A61F2210/0004Particular material properties of prostheses classified in groups A61F2/00 - A61F2/26 or A61F2/82 or A61F9/00 or A61F11/00 or subgroups thereof bioabsorbable
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2250/00Special features of prostheses classified in groups A61F2/00 - A61F2/26 or A61F2/82 or A61F9/00 or A61F11/00 or subgroups thereof
    • A61F2250/0058Additional features; Implant or prostheses properties not otherwise provided for
    • A61F2250/0067Means for introducing or releasing pharmaceutical products into the body

Abstract

A sustained drug-delivery implantable device such as stent manufactured from polymers, and more particularly, biodegradable polymers including biodegradble polyesters is disclosed. The medical device includes at least one therapeutics agent encapsulated in at least one biodegradable polymer wherein at least a portion of the therapeutic agent is crystallize. The device and methods to encapsulate one or more therapeutic agents, where each therapeutics agent may be chosen from the following categories: immunosuppressant agents, anti-neoplastic agents and anti-flammatory agents are disclosed. Other embodiments include methods of fabricating drug-containing implantable medical device.

Description

BIODEGRADABLE DRUG ELUTING STENT AND METHODS OF MAKING THE SAME

CROSS-REFERENCE TO RELATED APPLICATIO S

[0001 ] This application claims the benefit of the U.S provisional application number 61 /427, 141 , fi led on Dec, 24, 2010. This application is also a continuation-in-part of the J .S patent application number 12/209, 1 04, filed on Sept I 1 , 2008, the U .S patent appl ication number 1 1 /843,528, filed on August 22, 2007 and U .S patent appl ication number 1 3/014750 filed on Jan, 27, 201 1 . The disclosures of all of which are hereby incorporated by reference in their entireties.

FIELD OF THE INVENTION

[0002] The present invention relates to a biodegradable drug-eluting stent comprising at least one therapeutic agent encapsulated inside at least one biodegradable polymer wherein the encapsulated therapeutic agent would be susta inably and control led released.

[0003] The present invention encompasses the discovery that at least one therapeutic agent can be encapsu lated into at least one biocompatible polymer through extrusion or injection molding process to form sol id tubu lar structure for subsequent drug-eluting stent fabrication, and at least a portion of the encapsulated therapeutic agent in such drug-containing polymeric tube is crystal l ine.

[0004] The present invention further provides the methods of fabricating drug-containing implantable biodegradable medical device such as stent that effectively controls sustained release of the anti-neoplastic agent and the immunosuppressant agent. The present invention also encompasses the finding that medical devices encapsu lated with such drug or a drug-combination are surprisingly effective in inhibiting, preventing, and/or delaying the onset of hyper prol iferative conditions such as restenosis in vivo. The present invention therefore provides, among other things, a drug-containing implantable medical device comprising an immunosuppressant agent, an anti-neoplastic agent encapsulated in at least one biocompatible polymers. The present invention further provides medical devices encapsulated with at least one therapeutic agent according to the invention and other drug del ivery or eluting systems and methods of their uses.

[0005] In one aspect, the present invention related to a drug-containing implantable medical device comprising at least one therapeutic agent were encapsulated inside at least one biocompatible polymer, wherein the drugs are characterized with sustained-release of the immunosuppressant agent, an anti-neoplastic agent, and an combination of both for at least about 4 weeks (e.g., at least 5 weeks, 6 weeks, 7 weeks, 8 weeks, 9 weeks, 1 0 weeks, 1 1 weeks, 12 weeks, or longer).

[0006] In some embodiments, suitable immunosuppressant agent is sirolimus or a prodrug or analog thereof. In some embodiments, suitable immunosuppressant agents are selected from zotarolimus, tacrolimus, everolimus, biolimus, pimecrolimus, supralimus, temsirol imus, TAFA 93, invamycin, neuroimmunophi lins, or combinations or ana logs thereof. In some embodiments, suitable anti-neoplastic agent is paclitaxel or a prodrug or analog thereof. In some embodiments, suitable anti-neoplastic agent is selected from carboplatin, vinorelbine, doxorubicin, gemcitabine, actinomycin-D, cisplatin, camptothecin, 5-fiuorouracil, cyclophosphamide,

I -β-D-arabinofuranosylcytosine, or combinations or analogs thereof.

[0007] I n some embodiments, therapeutic agent encapiisulated inside the biocompatible polymer in accordance with the invention further include one or more anti-thrombotic agents, anti-proliferative agents, anti-inflammatory agents, anti-m igratory agents, agents affecting extracellular matrix production and organization, anti-m itotic agents, anesthetic agents, anti-coagulant agents, vascular cell growth promoters, vascular cel l growth inh ibitors, cholesterol-lowering agents, vasodilating agents, and/or agents that interfere with endogenous vasoactive mechanisms. For example, in some embodiment, the combination of immunosuppressant and anti-neoplastic in a ratio, by weight, ranging from about 1 :99 to 99: 1 (e.g., 1 0:90, 20:80, 30:70, 40:60, 50:50, 60:40, 70:30, 80:20, 90: 1 0). In some embodiments, the anti-neoplastic agent and immunosuppressant agent are present in a ratio by weight of approximately 1 : 1 (i .e., 50:50). In some embodiments, the anti-neoplastic agent and

immunosuppressant agent are present in an amount ranging from about 0.1 μg/mm2 to about 5 .g/mm2 (e.g., 0.2, 0.4, 0.6, 0.8, 1 .0, 1 .2, 1 .4, 1 .6, 1 .8, 2.0, 2.2, 2.4, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6, 3.8, 4.0, 4.2, 4.4, 4.6, 4.8, μ¾/ιτιηι2). 10008] I n some embodiments, polymers suitable for the present invention contains a biodegradable polymer. In some embodiments, the biodegradable polymer is a polyester polymer. In some embodiments, suitable polyester polymer include, but are not limited to, poly(D,L-lactide-co-glycol ide) (PLGA), polylactide (PLA), poly(L-lactide) (PLLA), poly(D,L-lactide (PDLA), polyglycolides (PGA), poly(D,L-glycolide) (PLG), and combinations thereof. In some embodiments, polymer in accordance with the invention further contains a calcium phosphate. In some embodiments, suitable calcium phosphates include, but are not l imited to, amorphous calcium phosphate (ACP), dicalcium phosphate (DCP), tricalcium phosphate (TCP), pentacalcium hydroxyapatite (HAp), tetracalcium phosphate monoxide (TTCP), and combinations thereof. In some embodiments, the biodegradable polymer and calcium phosphate are presen in a ratio (by weight) of about 1 :99 to 99: 1 (e.g., 1 0:90, 20:80, 30:70, 40:60, 50:50, 60:40, 70:30, 80:20, 90: 1 0).

[0009] I n some embodiments, polymers suitable for the present invention include a nonbiodegradable polymer. In some embodiments, suitable nonbiodegradable polymers include, but are not limited to, poly-n-butyl methacrylate (PB A), polyethylene-co-vinyl acetate (PEVA), poly (styrene-b-isobutylene-b-styrene) (SI BS), and combinations thereof.

[001 0] In some embodiments, the immunosuppressant agent and anti-neoplastic agent and anti-throbotic are present in the same layer. In some embodiments, the immunosuppressant agent and anti-neoplastic agent and anl i-thrombotic agent are present in different layers.

100 1 1 ] I n another aspect, the present invention provides methods for fabricating drug-contain ing implantable medical device, more specifical ly, a drug-containing biodegradable drug-eluting stent, includ ing drug-polymeric composition compound ing, drug-containing polymeric composition tube forming, polymeric and drug molecu lar orientation, stent laser cutting etc. In some embodiments, the compoundable polymer and drugs are crystal lized by various nanotechnologies and the drug-containing tube is then extruded through an extruder or injection moldi ng with the drug-polymeric composition at the temperature of equal or above polymer melting point but below the encapsulated drug's melting point. In one embodiment, the iianoparticle sized polymer and drug are prem ixed before extrusion or molding and be extruded to solidified drug-containing tubular structure through extruder under the temperature between the polymer and drug's melting point. In another embodiment, ( he nanoparticle-sized/crystalized drugs are added to the molten polymer through a downstream feeder in an extruder. In an preferred embodiment, two or more therapeutic agents are be add in either the same layer of polymer or in the deferent layer of the tube through multiple layer extrusion technology.

[001 2] In some embod iment, the formed tubes are further deformed radial ly and axially to orientate both the polymer and drug molecule direction with the blow molding technology to increase the tube's mechanic strength and drug's crystalin ity. The deformed tubes are then subjected to laser cutting which is a know art according to the stent design pattern.

BACKGROUND OF THE INVENTION

100 1 3] Coronary Artery Disease (CAD) has been the number one kil ler in the United States since 1900 and sti ll remains the most common cause of death in the Western world despite therapeutic advances. Drug-Eluting Stent (DES) is currently the major therapy for CAD treatment. DES not only increases procedural success rates, but also increases the safety of procedures by decreasing the need for emergency coronary artery bypass graft surgery (CABG). As a result, stents are currently uti lized in over 85% of the two million Percutaneous Coronary

Intervention procedures (PCIs) in the US. The total direct cost for these life-saving procedures is over $2 bil lion annual ly. Despite the prevalent use of DES, there are significant drawbacks, including the need for cosily, long-term anti-platelet therapy, as well as the metal artifact remaining in the vessel. Coronary stents are only required to provide scaffolding for up to six months following the procedure, however, since the stent remains in the vessel, potential long term compl ications may arise. In addition, the remaining metal scaffolding precludes the vessel from returning to its natural state and prevents true endothelial repair and arterial remodel ing. Following are brief descriptions of the two major issues existing in current DESs.

[ 0014] In-Stent Restenosis (I SR): ISR is the re-narrowing of an opened artery after stenting due primari ly )o the prol iferative response of the intima, a layer of cells that line the lumen of the vessel, composed of connective tissue and smooth muscle cel ls (SMC). ISR has been the biggest problem in PCI unti l the recently successfu l development of DESs. Initially, the restenosis rate is as high as over 50% within six months post bal loon d i lation . Stenting lowers this number to 20-30%. DESs can significantly reduce the rate of restenosis to < 1 0%. However, I SR in patients with high risk such as smal l vessels, diabetes, and long diffusion diseased arteries stil l remains unacceptably high (30%-60% in bare metal stents and 6%- l 8% in DESs).

[00 1 5] Thrombosis: In spite of restenosis remaining a cl inical problem in approximately 10% with DES implantation, it can often be successful ly treated with repeated DES implantation. The greatest concern, however, has been of stent thrombosis which is associated with a high rate of myocardial infarction and death. The rate of early stent thrombosis (less than 30 days following implantation) appears simi lar in both bare metal stents ( BM S) and DESs, However, late stent thrombosis (LST) has been increasingly reported beyond 12 months fol lowing DES implantation, with the greatest risk occurring as a result of premature discontinuation of antiplatelet therapy. Although the precise mechanism of late stage stent thrombosis is unknown, it is generally bel ieved that the combination of delayed endothelialization due to antiproliferative therapy and persistence of the nonerodable polymer contribute to the hypersensitivity reaction, possibly with some residual active drug that may not be e luted.

[001 6] Therefore, the chal lenges faced by emerging technologies are to reduce restenosis in h igh-risk lesions without compromising heal ing in order to avoid late thrombotic compl ications, and to improve system del iverabi lity in order to allow the devices to treat more complex patients. Currently, a number of strategies are being uti lized to achieve these goals, through the development of novel stent platforms, coating with

biodegradable polymer or move away from polymers, and with new generations and/or combinations of biological agents that both inhibit proliferation and promote endothel ialization. With the recent positive data from Abbott's ABSORB trial, clinical consensus is building that fully biodegradable stents (BDS) represent the next generation in DBS.

[00 1 7] Bioabsorbable and biodegradable materials for manufacturing temporary stents present a number of advantages. The conventional bioabsorbable or bioresorbable materials of the stents are selected to absorb or degrade over time to al low for subsequent interventional procedures such as restenting of the original site if there is restenosis and insertion of a vascular graft. Further, bioabsorbable and biodegradable stents allow for vascular remodeling, which is not possible with metal stents that tethers the arterial wall to a fixed geometry. In add ition to the advantages of not having to surgically remove such stents, bioabsorbable and biodegradable materials tend to have excel lent biocompatibil ity characteristics, especially in comparison to most conventional ly used

biocompatible metals. Another advantage of bioabsorbable and biodegradable stents is that the mechanica l properties can be designed to substantially eliminate or reduce the stiffness and hardness that is often associated with metal stents, which can contribute to the propensity of a stent to damage a vessel or lumen. Examples of novel biodegradable stents incl ude those found in U.S. Pat. No. 5,957,975, and U .S. appl ication Ser. No.

1 0/508,739, which is herein incorporated by reference in its entirety.

j 00 1 8] However, in all current commercially available DESs and investigational biodegradable DESs, the drugs were coated on the stent surface in approximate l Oum th icknesses. These drug-containing polymeric compositions coated on stent surface are typically formed by dissolving one or more therapeutic agents and one or more biocompatible polymers in one or more solvents, fol lowed by removing the solvents to form a solid ified drug-containing polymeric composition. The solvent removal or solidification can be carried out using various techniques, including, but not limited to: spray drying (for preparation of coatings), solvent casting or spin coating (for preparation of thin fi lms or membranes), and spinning (for preparation of fibers).

j 001 9] The sol idified drug-containing coating compositions so formed typically contain the therapeutic agents in an amorphous phase. Amorphous therapeutic agents are very unstable, especially at temperatures that are above their glass transition temperatures. The amorphous therapeutic agents may gradually degrade over time, due to oxidation in the presence of oxygen. Such amorphous therapeutic agents can also become plasticized during device steril ization processes. Furthermore, therapeutic agent coated on the surface of medical device in this manner, are confined in or on the surface of the implantable medical devices amorphously by the biocompatible polymer and can be released into the surrounding environment in less than four weeks, As the restenosis forms in approximately 3 months and the impaired vascular remold process complete in approximately 6 months post stent implantation, the four weeks drug release period is theoretically neither longer enough for inhibiting restenosis formation nor for impaired vascular remolding, therefore there a need of a new drug-eluting stent with prolonged drug-release kinetics(at least over four wks) and improved drug-stability.

[0020] Therefore, the present invention provides a biodegradable drug-eluting stent system comprising at least one therapeutic agent encapsu lated inside biodegradable polymeric stent with controlled, sustainably release of therapeutic agent to the disease site. The invention also provide the methods of fabricating the stent.

SUMMARY OF THE INVENTION

[0021 ] In one aspect, the present invention include a bioabsorbable drug-eluting stent fabricated with a drug-containing polymeric composition wherein at least one therapeutic agent were encapsulated inside a least one biodegradable polymer, more specifically, biodegradable polyester polymer. Each encapsulated therapeutics agent is selected from the group consisting of immunosuppressant agents, anti-neoplastic agents and

anti-thrombotic agents, and at least a portion of those encapsulated therapeutic agent in this polymer is crystal l ine.

[0022 ] In one aspect, the present invention include a bioabsorbable drug-eluting stent fabricated with a drug-contain ing polymeric composition wherein two or more therapeutic agent were encapsulated inside at: least one biodegradable polymer, more specifically, biodegradable polyester polymer. Each encapsu lated therapeutics agent is selected from the group consisting of immunosuppressant agents, anti-neoplastic agents and

anti-thrombotic agents, and at least a portion of those encapsulated therapeutic agent in this polymer is crystal line.

[0023] In other aspect, the present invention include a bioabsorbable drug-delivery medical device fabricated with a drug-containing polymeric composition wherein two or more therapeutic agent were encapsulated inside at least one biodegradable polymer, more specifically, biodegradable polyester polymer. Each encapsulated therapeutics agent is selected from the group consisting of immunosuppressant agents, anti-neoplastic agents, anti-thrombotic agent, and antibiotic, and at least a portion of those encapsulated therapeutic agent in this polymer is crystal l ine.

[0024] In another aspect, the present invention includes a method of fabricating an implantable medical device with drug-containing polymeric composition. The method includes the operations of: drug and polymeric pre-crystall ization and drug-polymeric composition compounding, drug-containing polymeric composition tube forming, polymeric and drug molecular orientation, stent laser cutting etc. the therapeutic agent is selected from the group consisting of immunosuppressant agents, anti-neoplastic agents, anti-thrombotic agent, and antibiotic, and at least a portion of those encapsulated therapeutic agent in this polymer is crystalline.

[0025] I n another aspect, the present invention includes a method of fabricating a biodegradable drug eluting stent with drug-contain ing polymeric composition. The method includes the following processing operations: drug and polymer precrystal ization and drug-polymeric composition compounding with various nanotechnologies, drug-containing polymeric composition tube form ing, polymeric and drug molecular orientation, stent laser cutting etc. The therapeutic agent is selected from the group consisting of immunosuppressant agents, anti-neop!astic agents, anti-thrombotic agent, wherein the at least one therapeutic agent is amorphous; Deform ing the formed drug-containing tube would at least crystal line a portion of those encapsulated therapeutic agent in polymer.

10026] Preferably, at least 1 0% of the therapeutic agent in the fabricated medical device of the present invent ion is crystal l ine. More preferably, at least 50% of the therapeutic agent in the medical device of the present invention is crystal l ine. Most preferably, at least 90%, 95%, or 98% of the therapeutic agent in the medical device is crystal l ine.

BRI EF DESCRIPTIO OF THE DRAWING

[ 0027] Figure 1 i llustration of an exemplary biodegradable drug eluting stent of the invention

[0028] Figure 2 exemplary results illustrating an HPLC analysis of the residue level of sirolimus and pac!itaxel encapsulated in the invented biodegradable-drug eluting stent at Pre and Post extrusion. A: Pre-extruded drug-polymeric composition; B: Post-extrusion of drug-polymeric composition. Please note that both paclitaxel and sirol imus were detected at 254 nin post extrusion indicating that the both drug were not degraded during in vented extrusion process.

[0029] Figure 3 depicts exemplary results of restenosis different between drug encapsulated PLLA and PLLA/ACP stents in pig coronary artery at one month post implantation.

[0030] Figure 4 illustrates exemplary results of the histological changes (neointima and residual arterial lumen area) between drug encapsulated PLLA/ACP and PLLA stent groups at one month post implantation.

DEFINITIONS

1003 I ] Agent: as used herein, the term "agent" refers to any substance that can be del ivered to a tissue, cel l, vessel, or subcellular locale. In some embodiments, the agent to be delivered is a biologically active agent (bioactive agent), i.e., it has activity in a biological system and/or organism. For instance, a substance that, when introduced to an organism, has a biological effect on that organism, is considered to be biological ly active or bioactive. In some embodiments, an agent to be delivered is an agent that inhibit, reduce or delay cell prol iferation.

[0032] Animal : As used herein, the term "animal" refers to any member of the animal kingdom, in some embodiments, "animal" refers to humans, at any stage of development. In some embodiments, "animal" refers to non-human animals, at any stage of development. In certain embodiments, the non-human animal is a mammal (e.g., a rodent, a mouse, a rat, a rabbit, a monkey, a dog, a cat, a sheep, cattle, a primate, and/or a pig). In some embodiments, an imals include, but are not limited to, mammals, birds, repti les, amph ibians, fish, insects, and/or worms. In some embodiments, an animal may be a transgenic animal, genetical ly-engineered animal, and/or a clone.

[0033] Analogues or derivatives: As used herein, a derivative or an analogue refers to a compound can be formed from another compound. Typically, a derivative or an analogue of a compound is formed or can be formed by replacing at least one atom with another atom or a group of atoms. As used in connection with the present invention, a derivative or an analogue of a compound is a modified compound that shares one or more chemical characteristics or features that are responsible for the activity of the compound. In some embodiments, a derivative or an analogue of a compound has a pharmacophore structure of the compound as defined using standard methods known in the art. In some embodiments, a derivative or an analogue of a compound has a pharmacophore structure of the compound with at least one side chain or ring linked to the pharmacophore that is present in the original compound (e.g., a functional group). In some embodiments, a derivative or an analogue of a compound has a pharmacophore structure of the compound with side chains or rings linked to the pharmacophore substantial ly similar to those present in the original compound. As used herein, two chem ical structures are considered "substantially similar" if they share at least 50% (e.g., at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 98%, or at least 99%) identical l inkage bonds (e.g., rotatable linkage bonds). In some embodiments, two chemical structures are considered "substantially similar" if they share at least 50% (e.g., at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 98%, or at least 99%) identical atom coordinates defining the structures, or equivalent structures having a root mean square of deviation less than about 5.0 A (e.g., less than about 4.5 A, less than about 4.0 A, less than about 3.5 A, less than about 3.0 A, less than about 2.5 A, less than about 2.0 A, less than about 1 .5 A, or less than about 1 .0 A). In some embodiments, two chem ical structures are considered "substantially similar" if they share at least 50% (e.g., at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 98%, or at least 99%) identical atom coordinates defining surface-accessible features (e.g., hydrogen bond donors and acceptors, charged/ionizable groups, and/or hydrophobic patches), or equivalent features having a root mean square of deviation less than about 5.0 A (e.g., less than about 4.5 A, less than about 4.0 A, less than about 3.5 A, less than about 3.0 A, less than about 2.5 A, less than about 2.0 A, less than about 1 .5 A, or less than about 1 .0 A).

[0034] Anti-neoplastic agent: As used herein, the term "anti-neoplastic agent" (also refer to as

anti-prol iferative agent) refers to an agent that inhibits and/or stops growth and/or proliferation of cel ls. An anti-neoplastic agent may display activity in vitro (e.g., when contacted with cells in culture), in vivo (e.g., when administered to a subject at risk of or suffering from hypei proliferation), or both. Exemplary ant i-neoplastic agents include, but are not limited to, paclitaxel, enoxaprin, angiopeptin, carboplatin, vinorelbine, doxorubicin, gemcitabine, actinomycin-D, cisplatin, camptothecin, 5-fluorouraci l, cyclophosphamide,

Ι -β-D-arabinofuranosylcytosine, or monoclonal antibodies capable of blocking smooth muscle cell proliferation, hirudin, and acetyl sal icy l ie acid, amlodipine and doxazosin.

[0035] Approximately: As used herein, the term "approximately" or "about," as applied to one or more values of interest, refers to a value that is simi lar to a stated reference value. In certain embodiments, the term

"approximately" or "about" refers to a range of values that fall within 25%, 20%, 19%, 1 8%, 1 7%, 16%, 1 5%, 14%, 13%, 12%, 1 1 %, 1 0%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1 %, or less in either direction (greater than or less than ) of the stated reference value un less otherwise stated or otherwise evident from the context (except where such number would exceed 1 00% of a possible value).

[0036] Combination therapy: The term "combination therapy", as used herein, refers to those situations in which two or more different pharmaceutical agents are administered in overlapping regimens so that the subject is simultaneously exposed to both agents.

[0037] Control: As used herein, the term "control" has its art-understood meaning of being a standard against which results are compared. Typically, controls are used to augment integrity in experiments by isolating variables in order to make a conclusion about such variables. In some embodiments, a control is a reaction or assay that is performed simu ltaneously with a test reaction or assay to provide a comparator. [0038] Hyperprol iferative condition: As used herein, the term "hyperproliferative condition" refers to undesirable cell growth. In some embodiments, hyperproliferative condition is associated with atherosclerosis, restenosis, proliferative vitreoretinopathy and psoriasis. The term is not intended to include cellular

hyperprol iteration associated with cancerous conditions. In some embodiments, undesirable cel l growth refers to unregu lated cel l division associated with smooth muscle cel ls and/or fibroblasts. In some embod iments, undesirable cel l growth is restenosis, which typical ly refers to the re-narrowing of opened artery after a surgical procedure such as stenting or PTCA procedure. Restenosis is typically due to a prol iferative response of the intima, a layer of cells that line the lumen of the vessel, composed of connective tissue and smooth muscle cells (SMC).

[0039] Immunosuppressant agent: As used herein, the term "immunosuppressant agent" refers to any agent that reduces, inhibits or delays an immuno-reaction such as an inflammatory reaction. Exemplary

immunosuppressants include, but are not l imited to, sirolimus (RAPAMYCIN), tacrol imus, everol imus.

dexamethasone, zotarol imus, tacrol imus, everol imus, biol imus, pimecrol imus, supral imus, temsirolimus, TA FA 93, invamycin and neuroimmunophi l ins.

[0040] In vitro: As used herein, the term "in vitro" refers to events that occur in an artificial environment, e.g., in a test tube or reaction vessel, in cel l culture, etc., rather than within a multi-cellular organism.

[004 1 I In vivo: As used herein, the term "in vivo" refers to events that occur within a multi-cellu lar organism such as a non-human an imal .

[0042] Polymer: As used herein, the term "polymer" refers to any long-chain molecules contain ing smal l repeating units.

10043] Prodrug: As used herein, the term "prodrug" refers to a pharmacological substance (drug) that is adm inistered or delivered in an inactive (or significantly less active) form. Typically, once admin istered, the prodrug is metabol ised in vivo into an active metabolite. The advantages of using prodrugs include better absorption, biocompatibil ity, distribution, metabolism, and excretion (ADM E) optim ization. Sometime, the use of a prodrug strategy increases the selectivity of the drug for its intended target.

[0044] Subject: As used herein, the term "subject" or "patient" refers to any organism to which systems, compositions or devices in accordance with the invention may be delivered or administered, e.g., for experimental, diagnostic, prophylactic, and/or therapeutic purposes. Typical subjects include animals (e.g., mammals such as m ice, rats, rabbits, non-human primates, and humans; etc.). j 0045] Substantial ly: As used herein, the term "substantially" refers to the qualitative condition of exh ibiting total or near-total extent or degree of a characteristic or property of interest. One of ordinary ski l l in the biological arts will understand that biological and chemical phenomena rarely, if ever, go to completion and/or proceed to completeness or ach ieve or avoid an absolute result. The term "substantially" is therefore used herein to capture the potential lack of completeness inherent in many biological and chemical phenomena.

[0045] Suffering from: An individual who is "suffering from" a disease, disorder, and/or condition has been diagnosed with or displays one or more symptoms of the disease, disorder, and/or condition.

[0046] Susceptible to: An individual who is "susceptible to" a disease, disorder, and/or cond ition has not been diagnosed with the disease, disorder, and/or condition. In some embodiments, an individual who is susceptible to a disease, disorder, and/or condition may not exhibit symptoms of the disease, disorder, and/or condition , i n some embodiments, an individual who is susceptible to a disease, disorder, and/or condition wi ll develop the disease, disorder, and/or condition. In some embodiments, an individual who is susceptible to a disease, disorder, and/or condition wi l l not develop the disease, disorder, and/or condition.

[0047] Sustained-release: As used herein, the term "sustained-release" refers to releasing (typically slowly) a drug over time. Typical ly, sustained-release formulations can keep steadier levels of the drug in the bloodstream. Typically, sustained-release coatings are formulated so that the bioactive agent is embedded in a matrix of polymers such that the dissolving agent has to find its way out through the holes in the matrix. In some embodiments, sustained-release coatings include several layers of polymers. In some embod iments,

sustained-release coating matrix can physically swell up to form a gel, so that the drug has first to dissolve in matrix, then exit through the outer surface. As used herein, the terms of "sustained-release," "extended-release," "time-release" or "timed-release," "control led-release," or "continuous-release" are used inter-changeably.

[0048] Therapeutically effective amount: As used herein, the terms "therapeutically effective amount" or "effective amount" of a therapeutic or bioactive agent refer to an amount that is sufficient, when admin istered to a subject suffering from or susceptible to a disease, disorder, and/or condition, to treat, diagnose, prevent, and/or delay the onset of the symptom(s) of the disease, disorder, and/or condition. In some embod iments, an effective amount refers to the amount necessary or sufficient to inhibit the undesirable cell growth. The effective amount can vary depending on factors know to those of skill in the art, such as the type of cell growth, the mode and the regimen of administration, the size of the subject, the severity of the cell growth, etc.

[0049] Therapeutic agent: As used herein, the phrase "therapeutic agent" refers to any agent that, when administered to a subject, has a therapeutic effect and/or elicits a desired biological and/or pharmacological effect.

[0050] Treating: As used herein, the term "treat," "treatment," or "treating" refers to any method used to partially or completely al leviate, ameliorate, rel ieve, inhibit, prevent, delay onset of, reduce severity of and/or reduce incidence of one or more symptoms or features of a particular disease, disorder, and/or cond ition (e.g., hyperprol iferation such as restenosis). Treatment may be administered to a subject who does not exhibit signs of a disease and/or exhibits only early signs of the disease for the purpose of decreasing the risk of developing pathology associated with the disease.

[005 1 ] Nanoparticle: The term "nano-particles" or "micro-particles" is used throughout the present invention to denote carrier structures that are biocompatible and have sufficient resistance to chemical and/or physical destruction by the environment of use such that a suffic ient amount of the nano-particles and/or micro-particles remain substantially intact after injection into a target site in the arterial wall. Typically, the nano-particles of the present invention have sizes ranging from about 1 nm to about 1000 nm, with sizes from about 1 00 nm to about 500 nm being more preferred. The micro-particles of the present invention have sizes ranging from about 1 .mu.in to about 1000 .mu.m, with sizes from about 10 .mu.m to about 200 .mu.m being more preferred. The

pharmacologically active agent as described hereinabove is loaded within and/or on the surfaces of the nano-particles and/or m icro-particles.

DETAILED DESCRIPTION OF THE INVENTION

Restenosis

[0052] Restenosis, e.g., In-Stent Restenosis (ISR), formation is a multi-factorial, sequential process. For example, it is generally believed that three stages are involved in the ISR process: 1 ) Thrombotic Phase (day 0-3 after stent implantation). This phase is the initial response of artery tissue to stent implantation characterized with rapid activation, adhesion, aggregation and deposition of platelets and neutrophils to form a thrombus in the inj ured site. 2) Recruitment Phase. This phase occurs between day 3 to 8 characterized with an intensive inflammation cell infiltration. I n this phase, the inflammation cells including leukocyte, monocytes, and macrophages were activated and infi ltrated into the injured vessel wal l. Subsequently, the recruited

inflammation cells in the injured vessel wall provide the key stimulus for subsequent smooth muscle cell (SMC) prol iferation and migration. In add ition, the release and expression of adhesion cel ls, cytokines, chemokines, and growth factors by platelets, monocytes, and SMCs contribute to the further recruitment, infiltration at the site of inj ury, and further proliferation/migration of SMCs from media to neointima in the days after injuries. Anti-inflammation drugs (e.g., dexamethasone) and immunosuppressant drugs (e.g., sirolimus) are thought to delay or inhibit this phase. 3) Proliferate Phase. This phase last 1 to 3 months depending on the thickness of the residual thrombus and the rate of growth. At this stage, inflammation cells colonize the residual thrombus, forming a "cap" across the mural thrombus. The cells progressively proliferate, resorbing residual thrombus unti l al l thrombus is gone and is replaced by the neointima tissue. These processes are induced by the early-phase events and also the exposure to circulatory mitogens (e.g., angiotensin I I, plasmin). Vascular SMCs, otherwise in the quiescent phase of the cell cycle, are now triggered by early gene expression to undergo proli feration and migration with subsequent synthesis of extra cellular matrix and collagen, resulting in neointima formation. The process of neointimal growth, which consists of SMC, extracellular matrix, and macrophages recruited over a period of several weeks, is similar to the process of tumor tissue growth. This pathologic sim i larity between tumor cel l growth and benign neointimal formation has led to the discovery of anti-tumor drugs as effective agents for the treatment of ISR.

Sustained Drug Delivery Systems

[0053] A typical drug delivery system (also referred to as drug eluting system) for treating, preventing, inhibiting, or delaying the onset of retenosis include an implantable or insertable medical device (e.g., stent), coating or coating matrix, and bioactive agents. Implantable or insertable medical devices such as a stent prov ide a basic platform to deliver sufficient drug to the diseased arteries. Coating or coating matrix provides a reservoir for sustained delivery of bioactive agents. Typically, achieving compatibility between the implantable or insertable medical device, coating matrix, drugs and vessel wall is central for successful development of a drug delivery system.

Implantable or Insertable Medical Devices

[0054] A typical platform for delivery of anti-restenosis drugs to an diseased arterial wall is an implantable or insertable medical device. A desirable drug-delivery platform typical ly has a larger surface area, minimal gaps between endothelial cells so as to m inimize plaque prolapsed (displacement) in areas of large plaque burden, and min imal deformation (adaptation in shape or form) after implantation. Exemplary implantable or insertable medical devices suitable for the present invention include, but are not limited to, catheters, guide wires, balloons, filters, stents, stent grafts, vascular grafts, vascular patchs or shunts.

[ 0055] In some embodiments, med ical devices suitable for the invention are stents. Stents suitable for the present invention include any stent for medical purposes, which are known to the skilled artisans. Exemplary stents include, but are not lim ited to, vascular stents such as self-expanding stents and balloon expandable stents. Examples of self-expand ing stents useful in the present invention are illustrated in U.S. Pat. Nos. 4,655,77 1 and 4 ,954, 1 26 issued to Wallsten and U.S. Pat. No. 5,061 ,275 issued to Wallsten et al . Examples of appropriate bal loon-expandable stents are shown in U.S. Pat. No. 5,449,373 issued to Pinchasik et al.

[0056] Suitable stents can be metal or non-metal stents. Exemplary biocompatible non-toxic metal stents include, but not limited to, stents made of stainless steel, nitinol, tantalum, platinum, cobalt al loy, titanium, gold, a biocompatible metal al loy, iridium, silver, tungsten, or combinations thereof. Exemplary biocompatible non-metal stents include, but not limited to, stents made from carbon, carbon fiber, cellulose acetate, cellulose n itrate, si l icone, polyethylene teraphthalate, polyurethane, polyamide, polyester, polyorthoester, polyanhydride, polyether sulfone, polycarbonate, polypropylene, polyethylene, polytetrafluoroethylene, polylactic acid, poiyglycol ic acid, a polyanhydride, polycaprolactone, polyhydroxybutyrate, or combinations thereof. Other polymers su itable for non-metal stents are shape-memory polymers, as described for example by Froix, U .S. patent No. 5 163952. which is incorporated by reference herein. Stents formed of shape-memory polymers, wh ich include methacylate-containg and acrylate-containing polymers, readily expand to assume a memory condit ion to expand and press against the lumen walls of a target vessel, as described by Phan, U.S. Patent No. 5603722, which is incorporated by reference in its entirety.

[0057] Typically, implantable or insertable medical devices are adapted to serve as a structural support to carry a polymer based coating as described herein. For example, a polymer-based, drug containing fiber can be threaded through a metal stent aperture. The metal stent typically provides the mechanical support in the vessel after deployment for maintaining vessel patency, and the polymer thread provides a control led release of bioactive agents. Another example is a drug-loaded polymer sheath encompassing a stent, as described in U .S. patent No. 5 83928(Scott, et al). Yet another example is a polymer stent which coexpand with a metal stent when placed in the target vessel, as described in U.S. patent No. 5674242(Pham, et al).

[0058] The various embodiments of the present invention include implantable medical devices, such as stents, manufactured from polymers, more particularly, biodegradable polymers such as, without l imitation,

biodegradable polyesters, polyanhydrides, or poly(ether-esters). The polymer may be a biostable polymer, a biodegradable polymer, or a blend of a bjostable polymer and a biodegradable polymer. As noted above, processing of a polymer, such as, without limitation, poly(L-lactide) (PLLA), results in the polymer being exposed to elevated temperatures, moisture, viscous shear, and other potential sources of degradation, such as metals and - metal catalysts. Certain embodiments of the present invention involve the addition of one or more therapeutic agent to the polymer before and/or during the manufacturing process.

[0059] A stent may include a pattern or network of interconnecting structural elements or struts. FIG. 1 depicts an example of a three-dimensional view of a stent. The stent may have a pattern that includes a number of interconnecting elements or struts 1 . The embodiments disclosed herein are not limited to stents or to the stent pattern i llustrated in FIG. 1 .

[0060] Although the discussion that follows focuses on a stent as an example of an implantable medical device, the embodiments described herein are easily applicable to other implantable medical devices, including, but not l imited to self-expandable stents, balloon-expandable stents, stent-grafts, and grafts. The embodiments described herein are easi ly applicable to patterns other than that depicted in FIG. 1 . The structural pattern of the device can be of virtually any design . The variations in the structure of patterns are virtually unl imited.

1 . Polymers

[006 1 ] Polymers suitable for the drug— incorporation of the present invention include any polymers that are biologically inert and not induce further inflammation (e.g., biocompatible and avoids irritation to body tissue). In some embod iments, suitable polymers are non-biodegradable. Exemplary non-biodegradable polymers include, but are not l im ited to, poly-n-butyl methacrylate (PBMA), polyethylene-co-vinyl acetate (PEVA), poly(sty rene-b-isobutylene-b-styrene (SIBS), and combinations or analogues thereof.

[0062] Other non-biodegradable polymers that are suitable for use in this invention include polymers such as polyurethane, si licones, polyesters, polyolefins, polyamides, polycaprolactam, polyimide, polyvinyl chloride, polyvinyl methyl ether, polyvinyl alcohol, acrylic polymers and copolymers, polyacrylonitrile, polystyrene copolymers of vinyl monomers with olefins (such as styrene acrylonitrile copolymers, ethylene methyl methacry late copolymers, ethylene vinyl acetate), polyethers, rayons, cellulosics (such as cellulose acetate, cellulose nitrate, cel lulose propionate, etc.), parylene and derivatives thereof; and mixtures and copolymers of ( he foregoing.

[0063] In some embodiments, a suitable biodegradable polymer is a polyester. Exemplary polyester polymers su itable for the invention incl ude, but are not limited to, poly(L-lactide), poly (D,L-lactide),

poly(L-lactide-co-D,L-lactide), poly(L-lactide-co-glycol ide), poly(D,L-!actide-co-glycolide),

poly(L-lactide-co-caprolactone), poly(glycol ide-co-caprolactone), poly(D,L-lactide-co-capro!actone) and blends of the aforementioned. PLA and PGA are desirable for medical applications because they have lactic acid and glycol ic acid as their degradation products, respectively. These natural metabolites are ultimately converted to water and carbon dioxide through the action of enzymes in the tricarboxylic acid cycle and are excreted via the respiratory system. In addition, PGA is also partly broken down through the activity of esterases and excreted in the urine. Along with its superior hydrophobicity, PLA is more resistant to hydrolytic attack than PGA, making an increase of the PLA:PGA ratio in a PLGA copolymer result in delayed degradabi lity.

[0064] Thus, although the invention can be practiced by using a single type of polymer, it is desirable to use various combinations of polymers. The appropriate mixture of polymers can be coordinated with biological ly active materials of interest to produce desired effects in accordance with the invention.

[0065] In some embodiments, polymers suitable for the invention include calcium phosphates. In some embod iments, calcium phosphates are used in combination with biodegradable polymers. Without wishing to be bound to a particular theory, it is bel ieved that combining calcium phosphate material with biodegradable polymers may buffer the acidic materials released by biodegradation, and therefore provide the polymer thai wi l l induce less inflammation. I n some embodiments, the ratio of the polyester polymer and the calcium phosphate ranges from about 99: 1 to 1 :99 (e.g., 1 0:90, 20:80, 30:70, 40:60, 50:50, 60:40, 70:30, 80:20, 90: 1 0).

Exemplary calcium phosphates that may be used in the current invention include, but not limited to, amorphous calcium phosphate (ACP), dicalcium phosphate (DCP), tricalcium phosphate (TCP), pentacalcium hydroxy! Apatite(HAp), tetracalcium phosphate monoxide(TTCP) and combinations or analogues thereof.

[0066] For example, ACP is an important intermediate product for in vitro and in vivo apatite formation with high solubi lity and better biodegradability. It was mainly used in the form of particles or powders, as an inorgan ic component incorporated into biopolymers, to adj ust the mechanical properties, biodegradabi l ity, and bioactivity of the resulting composites. Based on the similarity of ACP to the inorganic component of the bone, ACP is particular useful as a bioactive additive in medical devices to improve remineralization. Based on its solubi lity, coatings containing ACP may release ions into aqueous media, forming a favorable super saturation level of Ca + and PCv " ions for the formation of apatite. The ion release may neutral ize the acidity resulted from polymer biodegradation, retarding bioresorptive rate and eliminating inflammation occurrence.

2. Therapeutic Agent

[0067] The current invention provides encapsulating at least an anti-neoplastic agent and/or an

immunosuppressant agent in to a polymer. In some embodiments, an anti-neoplastic agent su itable for the invention is paclitaxel, or a prodrug or analog thereof. In some embodiments, anti-neoplastic agents su itable for the invention is selected from carboplatin, vinorelbine, doxorubicin, gemcitabine, actinomycin-D, cisplatin, camptothecin, 5-fluorouracil, cyclophosphamide, 1 -β-D-arabinofuranosylcytosine, or a combination or analogs thereof. In some embod iments, an immunosuppressant agent suitable for the invention is sirol imus, or a prodrug or analog thereof. In some embodiments, immunosuppressant agents suitable for the invention is selected from zotarolimus, tacrol imus, everolimus, biolimus, pimecrol imus, supralimus, temsirol imus, TAFA 93, invamycin or neuroimmunophi lins, or a combination or analogs thereof.

[0068] Paclitaxel, an extract from the bark of the Pacific yew tree Taxus brevifolia, has a melting point of 220 degree C. The anti-prol iferative activity of paclitaxel is a result of concentration-dependent and reversible binding to m icrotubules, specifically to the β-subun it of tubulin at the "N-terminal domain. This binding promotes polymerization of tubulin to form stable microtubules by reducing the critical concentration of tubul in required for 'polymerization and preventing depolymerization of the microtubules; the structure of the m icrotubules is stabil ized by the formation of bundles and multiple asters.

10069] Paclitaxel produces distinct dose-dependent effects within the cell : at low doses it causes G | arrest during interphase by inducing p53 and p21 tumor suppression genes, resulting in cytostasis. At high doses, the drug is thought to affect the G2-M phase of the cell cycle. Since the microtubules must be disassembled for transition from the G2 to the M phase to take place, and paclitaxel stabilizes the m icrotubule structure, mitotic arrest occurs in the presence of paclitaxel. Alternatively, high doses may affect the M-÷G i phase causing post-m itotic arrest and possibly apoptosis. In addition to these actions, activation of some protein kinases and serine protein phosphorylation are associated with depolymerization of microtubules, and are therefore inhibited by pacl itaxel. Thus, any paclitaxel analogs that retain or improve the cell cycle inhibitory function of pacl itaxel as described herein can be used in accordance with the invention.

[0070] S irol imus (rapamycin), a natural macrolide antibiotic with potent immunosuppressant properties, has a melt ing point of 1 80 degree C. Sirolimus was first approved by the FDA in 1999 for use as an anti-rejection agent fol lowing organ transplantation. Its use in intracoronary stenting was based on the premise that the

anti-prol iferative properties of the drug would inh ibit the neointimal hyperplasia ( I H) associated with restenosis following stent implantation. An important mechanism of Sirol imus action is entry into target cells and binding to the cytosolic immunophi l in FK-binding protein- 12 (FKBP- 12) to form a Sirol imus: FKBP-1 2 complex that interrupts signal transduction, selectively interfering with protein synthesis. After binding with FK-binding protein-12 (FKBP- 12), Sirol imus inh ibits the activity of the mammal ian target of Rapamycin (mTOR) and eventua l ly the activity of the cyclin-dependent kinase (cdk)/cyclin complexes, as well as the phosphorylation of retinoblastoma protein, thereby preventing advancement of the cel l cycle from G 1 to S phase. Thus, any Sirol imus analogs that retain or improve the cel l cycle inhibitory function of Sirolimus as described herein can be used in accordance with the invention.

[007 1 ] In preferred embodiments, the present invention provides drug-containing polymeric compositions containing a combination of an anti-neoplastic agent (such as paclitaxel or its prodrug or anologs) and an immunosuppressant agent (such as sirolimus or its prodrug or anologs).

[0072] Several combination therapies have been investigated previously in the treatment of in-stent restenosis. However, all those investigations involved the combination of anti-plastic (Paclitaxol) or immunosuppressant drug (S irolimus) with anti-thrombotic agents such as Glycoprotein ΠΒ/Ι Ι ΙΑ inhibitor or heparin) ( Leon M B and Bakhai Ameet, "Drug releasing stent and glycoprotein I lb/IIIA inh ibitor: combination therapy for the future," Am Heart J 2003 ; 146:S 13-7) or nitric oxide (Lin-Chiaen, and Delano Yang et al. "Combination of paclitaxel and nitric oxide as a novel treatment for the reduction of restenosis," J. Med. Chem. 2004; 47: 2276-2282). The purpose of adding anti-thrombotic drugs to coated stent is to prevent thrombosis. However, the efficacies of these combinations in inhibition of neointimal hyperplasia after stent implantation are limited. The one possible reason for the limited effects of these combinations is the pliysiochemical incompatibi l ity among combined drugs. Local drugs that are retained within the blood vessel are more effective than those are not. Both heparin and nitric oxide compounds are so soluble and diffusible that they simply cannot stay in the artery for more than a few m inutes after release. U S patent application to Hsu Li-Ch ien (US-2004/0037886: Drug Eluting Stent for Medical Implant) had disclosed a modified coating system to increase the compatibi lity among combined drugs (hydrophilic and hydrophobic drugs). However, as discussed below, the combination used in the modi fied coating system in Hsu's patent application is completely different from the combination therapies contemplated in the present application.

[0073] Drug-Containing polymeric composition of the present invention is developed to harness synergistic effects between an anti-neoplastic agent and an immunosuppressant agent. For example, contrary to the above-described hydrophilic and hydrophobic drug combinations, both sirolimus and pacl itaxel are hydrophobic, and retained well in blood vessel wall for up to three days through specifically binding to their individual binding proteins (Levin, A. D. et al ., "Edelman Specific binding to intracellular proteins determ ines arterial transport properties for rapamycin and paclitaxel," PN AS 2004; 1 0 1 (25):9463-67) after releasing from stent. Therefore, it is contemplated that a combination of these two drugs in a coating according to the invention may work synergisl ical ly to inh ibit restenosis including neointimal hyperplasia. Medical devices encapsu lated with a combination of bioactive agents would require lower doses of each agent to achieve the same or even greater anti-restenosis effects with less side-effects compared to otherwise identical medical devices coated with individual agent alone. The detail compositions combining anti-neoplastic agents and an immunosuppressant agents such as sirol imus and pacl itaxel or prodrugs or analogs thereof, are described in the U .S. application no. 1 1 / 144,91 7. Additional coating formulations containing anti-neoplastic agents and an immunosuppressant agents such as sirol imus and paclitaxel or prodrugs or analogs thereof, and biodegradable polymers are described in US patent application no. 1 1 /843,528.

[0074] the present invention further demonstrated that both sirol imus and pacl itaxel can be incorporated into polymeric stent strut through extrusion process and released in a control led manner. As shown Figure 2, combined drug (sirol imus and paclitaxel) in a biodegradable polymeric drug eluting stent survived the elevated extrusion temperature and are stable inside the stent strut. Therefore, the present invention provides new and powerfu l drug-eluting system for treatment of restenosis and an extrusion process for making the same.

[0075] Bioactive agents suitable for the invention may also include anti-thrombogenic agents such as heparin, heparin derivatives, urokinase, and PPack (dextrophenylalanine proline arginine chloromethylketone);

anti-inflammatory agents such as glucocorticoids, betamethasone, dexamethasone, prednisolone, cort icosterone, budesonide, estrogen, sulfasalazine, and mesalamine; other antineoplastic/antiprol iferative/anti-m iotic agents such as 5-fluorouracil, cisplatin, vinblastine, vincristine, epoth ilones, methotrexate, azath ioprine, halofuginone, adriamycin, actinomycin and mutamycin; endostatin, angiostatin and thymidine kinase inhibitors, and its analogs or derivatives; anesthetic agents such as lidocaine, bupivacaine, and ropivacaine; anti-coagulants such as

D -Phe-Pro-Arg chloromethyl keton, an GD peptide-containing compound, heparin, antithrombin compounds, platelet receptor antagonists, anti-thrombin anticodies, anti-platelet receptor antibodies, aspirin (aspirin is also classified as an analgesic, antipyretic and anti-inflammatory drug), dipyridamole, protamine, h irudin,

prostaglandin inhibitors, platelet inhibitors and tick antiplatelet peptides; vascular cell growth promoters such as growth factors, Vascular Endothelial Growth Factors (FEGF, all types including VEGF-2), growth factor receptors, transcriptional activators, and translational promoters; vascular cell growth inhibitors such as antiproliferative agents, growth factor inhibitors, growth factor receptor antagonists, transcriptional repressors, translational repressors, replication inhibitors, inhibitory antibodies, antibodies directed against growth factors, Afunctional molecules including a growth factor and a cytotoxin, Afunctional molecules including an antibody and a cytotoxin; cholesterol-lowering agents; vasodilating agents; and agents which interfere with endogenous vasoactive mechan isms; anti-oxidants, such as probucol; antibiotic agents, such as penicillin, cefoxitin, oxaci l l in, tobranycin angiogenic substances, such as acidic and basic fibrobrast growth factors, estrogen including estradiol (E2), estriol (E3) and 1 7-Beta Estradiol; and drugs for heart failure, such as digoxin, beta-blockers,

angiotensin-converting enzyme (ACE) inhibitors including captopril and enalopril.

[0076] In addition, bioactive agents suitable for the present invention include nitric oxide adducts, wh ich prevent and/or treat adverse effects associated with use of a medical device in a patient, such as restenosis and damaged blood vessel surface. Typical nitric oxide adducts include, but are not limited to, nitroglycerin, sodium nitroprusside. S-n itroso-proteins, S-nitroso-thiols, long carbon-chain lipoph i lic S-nitrosothiols, S-n itrosodithiols, iron-n itrosyl compounds, thion itrates, thion itrites, sydnonimines, furoxans, organic n itrates, and nitrosated amino acids, preferably mono-or poly-nitrosylated proteins, particularly polynitrosated albumin or polymers or aggregates thereof. The album in is preferably human or bovine, including human ized bovine serum album in. Such n itric ox ide adducts are d isclosed in U.S. Pat. No. 6,087,479 to Stamler et al . wh ich is incorporated herein by reference.

[0077] Bioactive agents may be encapsulated in micro or nano-capsules by the known methods.

[0078] B ioactive agents can be used with (a) biologically non-active material(s) including a carrier or an excipient, such as sucrose acetate isobutyrate (SABER™ commercial ly available from SBS) ethanol, n-methyl pymolidone, dimethyl sulfoxide, benzyl benxoate, benzyl acetate, albutnine, carbohydrate, and polysacharide. Also, nanoparticles of the biologically active materials and non-active materials are useful for the coating formulation of the present invention.

[0079] Bioactive agents includ ing anti-neoplastic agents and immunosuppressant agents may be present in one single layer. Alternatively, individual agents (such as anti-neoplastic agents and immunosuppressant agents) may be present in separate layers. In some embodiments, a drug-free polymer layer (also refered to as cap layer) can be coated over a layer or layers containing an anti-neoplastic agent and/or immunosuppressant agent to act as a diffusion barrier.

Crystall ized Polymeric and Drug Nanoparticle Preparation

[0080] The at least one biocompatible polymer of the present invention may form polymeric part icles with the at least one therapeutic agent encapsulated therein. The polymeric particles may have any suitable sizes (e.g., from about I nm to about 1 mm in average diameter) and shapes (e.g., sphere, el lipsoid, etc.). Preferably, but not necessarily, the at least one biocompatible polymer of the present invention forms nano- and/or micro-particles that are suitable for injection. The term "nano-particles" or "micro-particles" is used throughout the present invention to denote carrier structures that are biocompatible and have sufficient resistance to chemical and/or physical destruction by the environment of use such that a sufficient amount of the nano-particles and/or micro-particles remain substantially intact after injection into a target site in the arterial wall. Typically, the nano-particles of the present invention have sizes ranging from about 1 nm to about 1 000 nm, with sizes from about 1 00 nm to about 500 nm being more preferred. The micro-particles of the present invention have sizes ranging from about 1 .mu.m to about 1 000 .mu.m, with sizes from about 1 0 .mu.m to about 200 .mu.m be ing more preferred. The pharmacologically active agent as described hereinabove is loaded within and/or on the surfaces of the nano-particles and/or m icro-particles.

[0081 ] In a particularly preferred embodiment of the present invention, the at least one therapeutic agent are first formed into crystal l ine particles of desired sizes, and are then encapsulated into the at least one biocompatible polymer through extrusion or injection molding process. Preferably, but not necessarily, the crystal line particles of the therapeutic agent have an average particle size ranging from about 50 nm to about 50 .mu.m, and more preferably from about 1 00 nm to about 200 nm.

[0082] In order to retain the physical properties of the drug-containing devices (polymer film or coating integrity, etc), it may be necessary to reduce the particle size of the therapeutic agents. Smaller drug partic le size wi l l also provide d ifferent drug formulation and processing options, without affecting the processing efficiency. Crystall ine drug particles with the desired particle sizes can be readily formed by several different processes, as described hereinafter.

[0083] Nanotechnology provides new and enhanced particle formulation processes and offers a wide range of options for achieving drug particles in the micro- and nano-size range. Some of the new developments in nanotechnology have successful ly achieved particle engineering by using molecular scaffolds like dendrimers (polyvalent molecules) and ful lerenes (i .e., C-60 "bucky balls"). The smal l-size drug particles that can be formed by using nanotechnology are particularly useful for formulating poorly soluble drugs, since the reduced drug particle sizes significantly improve the bioavailability of such drugs, by providing higher surface area and accelerating dissolution and absorption of such drugs by the body.

[0084] Further, conventional techniques, such as m ill ing (either dry or wet), supercritical extraction, spray drying, precipitation, and recrystal lization, can also be used to prepare micro- and nano-size drug particles.

[0085] Mil ling is a well-established micronization technique for obtaining desired micro- and nano-size drug particles (either dry or suspended in liquid) with well controlled size distribution.

[0086] Dry mi ll ing can be used to obtain particle size below about 50 microns. Various dry milling methods, such as jet mi ll ing, high-speed mixer milling, planetary mil ling, fluid energy jet m il l ing, and bal l mi l ling, can be used to grind drug particles to about 1 micron. Mi lling is a relatively less expensive, faster, and easily scalable method, in comparison with other methods. M icronization occurs by particle collision (e.g., particle-particle or coll isions among the particles and the grinding media l ike bal ls, pins, or beads) in various vessel con figurations that may be stationary or shaken, rol led, or spun. These processes may involve compressed steam, compressed n itrogen, or compressed air. Process variables include air pressure used for grinding, time in the grinding zone and the feed rate.

[0087] Wet m i ll ing can be used to form solid drug particles below 1 micron to 80- 1 50 nm with wel l defined size distribution. Bead mi l l ing uses rotating agitator disks to move microsized grinding beads (50 microns to 3.0 mm) in an enclosed grinding chamber to produce particles as small as 0.1 micron. Another wet-mi l l ing system

(NanoCrystal.TM. System developed by Elan Drug Delivery) used for poorly water-soluble drugs generates particles sized in the 1 00-200 nm range.

[0088] Supercritical flu ids (SCF) can also be used to form small-size drug particles, by extracting solvents from d issolved drugs whi le drug-containing droplets are sprayed out of a nozzle. The anti-solvent used for extraction is typical ly supercritical carbon d ioxide, and the solvent(s) is typically water, ethanol, methanol, or isopropyl a lcohol. No solvent is used if the drug is read ily soluble in compressed carbon dioxide. In th is event, the drug-contain ing supercritical carbon dioxide simply is sprayed into a depressurized vessel. The particle-formation rate can be controlled by changing the pressure, temperature, and spray rate. The particle size is determined mainly by the size of the droplet and the choice of the SCF. Dissolving the same drug into two different solvents may resu lt in two different particle sizes. Particle sizes ranges typically in the range of about 100 nm. Crystal l ine morphology of the drug particles is retained by careful control over the smal l period of time when a drug comes out of solution and forms the particles.

[0089] Spray-drying technology is sim ilar to the SCF approach, except that instead of using a SCF to remove the solvent(s), the solvent(s) is removed by a controlled drying process. A drug and excipient formulation is d issolved in a solvent or a mixture of two or more solvents. The solution is then sprayed through a nozzle, forming very fine droplets, which are passed down a drying chamber at either elevated or reduced temperatures. A drying gas, such as nitrogen, causes the solvent(s) to precipitate from the droplets, resulting in dry drug particles. One particularly preferred spray-drying method uses a multichamber spray dryer to produce porous microspheres. The chambers are arranged in series, so that the particles can be dried sequentially at different temperatures. The crystall in ity of the drug particles is retained by controlling the chamber temperatures and the drying conditions.

[0090] Spray drying can generate particles with mean size ranges from 700 nm to 2-3 microns. Spray drying can be used with either water-soluble or insoluble drugs.

[0091 ] Precipitation is another technique that can be used to form small-sized drug particles from solution. One precipitation technique specifically uses low-frequency sonication to speed up the precipitation process, by producing a homogenous shear field inside the vessel. A drug-containing solution is introduced into a vessel sitting on a magnetic plate oscillating at frequencies typically around 60 Hz. The frequency facilitates the precipitation of the drug particles, which can then be dried or filtered. Precipitation can also be achieved by pH shift, by using a different solvent, or by changing the temperature. The oscillation frequency, the volume, and the manner in which the precipitation is achieved can be readily adjusted to form drug particles of the desired particle sizes. The particle size achieved by precipitation is typically in the range of 400 to 600 nm.

[0092] If the particle sizes of the crystalline drug particles as provided are already suitable for forming a polymeric composition that can be subsequently used to form a drug-eluting implantable medical device, then such crystalline drug particles can be directly used for forming the polymeric composition. However, if the particle sizes of the crystalline drug particles as provided are too large, the above-described methods can be readily used, either separately or in combination, to reduce the particles size down to a desired size range.

[0093] The drug-containing polymeric composition of the present invention can be formed by various methods that effectively encapsulate the small-size crystalline drug particles, as described hereinabove, into at least one biocompatible polymer as described hereinabove, provided that during and after the processing steps of such methods, at least a portion of the crystalline particles remain crystalline. Preferably more than 50%, more preferably more than 75%, and most preferably more than 90% of the crystalline particles remain crystalline during and after the processing steps of such methods.

Fabrication of Drug Eluting Stent

[0094] A stent such as stent 1 may be fabricated from a polymeric tube or a sheet by rolling and bonding the sheet to form the tube. A tube or sheet can be formed by extrusion or injection molding. A stent pattern, such as the one pictured in FIG . 1 , can be formed in a tube or sheet with a technique such as laser cutting, mach in ing or chem ical etch ing. The stent can then be crimped on to a bal loon or catheter for delivery into a bodi ly lumen.

[0095] The elevated temperatures, exposure to shear, exposure to moisture and exposure to radiation that is encountered in polymer processing may lead to degradation of both the polymer and the drugs. Such degradation may lead to a decrease in polymer molecular weight, drug stabi lity. In addition, polymer and drug degradation can result in formation of oligomers, cyclic dimers, and monomers, with or without a significant decrease in molecular weight, which can alter the polymer and drug properties and degradation behavior.

[0096] Some of the process operations involved in fabricating a drug-delivery stent may include:

(1 ) form ing a drug-contain ing polymeric tube using extrusion;

(2) radial ly deform ing the formed drug-containing tube by appl ication of heat and/or pressure;

(3) forming a stent from the deformed tube by cutting a stent pattern in the deformed tube;

(5) crimping the stent on a support element, such as a balloon on a delivery catheter;

(6) packaging the crimped stent/catheter assembly; and

(7) steril izing the stent assembly.

Extrusion/Injection Molding

[0097] The initial step in the manufacture of a drug-delivery stent is to obtain a drug-containing polymer t ube or sheet. The polymer tube or sheet may be formed using various types of forming methods, including, but not l im ited to, extrusion or injection molding. A polymer sheet may be rol led and bonded to form a polymer tube. Representative examples of extruders include, but are not l imited to, single screw extruders, intermesh ing co-rotating and counter-rotating twin-screw extruders and other multiple screw masticating extruders.

[0098] Both extrusion and injection molding expose the drug-polymer composition to elevated temperatures and shear. In extrusion, a drug-polymer composition melt is conveyed through an extruder and forced through a die as a fi lm in the shape of a tube. Depending upon the type of extrusion and the molecular weight of the polymer, the polymer may be close to, at, or above its melting point. Specifically, the melt viscosity is desirably in a particular range to faci litate the extrusion process. I n general, as the molecular weight increases, higher processing temperatures may be needed to achieve a melt viscosity that allows for processing. For example, for a

biodegradable polyester such as poly(L-lactide), the temperature range may be in the range of about I SO. legree. C. to 220. degree. C. for a melt extrusion operation. The residence time in the extruder may be about 5 m inutes to about 30 m inutes. These h igh temperatures, combined with the shear, moisture, residual catalyst, and other metals υ to which the drug-polymer matrix is exposed during extrusion, may lead to polymer degradation and drug decomposition.

[0099] The extrusion process can be used in the present invention to form drug-containing polymeric tube of desired drug release profile (e.g., either an immediate release profile or a controlled release profi le), depending on the polymer used. Further, each polymeric can contain two or more active drugs. A lternatively, two or more active ingredients that may potentially interact with one another in an undesired manner (i.e., incompatible) can be encapsulated into separate layer by multiple extrusion technology.

[0 1 00] Specifical ly, a biocompatible polymer, which has a lower melting temperature than the therapeutic agent to be encapsu lated, is melted, and the melted polymer is then mixed with the crystall ine particle of the therapeutic agent to form a molten mixture. Since the therapeutic agent has a higher melting temperature than the polymer, the crystallin ity of the therapeutic particles is not affected by mixing with the melted polymer. Subsequently, the molten mixture is extruded into a tube, and then cooled to below the melting temperature of the biocompatible polymer, thereby form ing a sol idified tubular structure that comprises a substantial ly continuous polymeric matrix with the crystal line particles of the therapeutic agent encapsulated therein. The sol idified tube structure can be treated by various techniques, such as, annealing, deforming, and laser cutting etc.

[0 1 01 ] Any biocompatible polymer or polymer blends that has a melting temperature lower than that of the therapeutic agent can be used in the above-described melt compounding process. For example,

poly(lactide-co-glycol ide), wh ich has a processing temperature of about 1 50. degree. C, can be used for melt compound ing with both rapamycin (i.e., sirol imus), which has a melting temperature of about 1 80. degree. C. and pacl itaxel which has a melting temperature of 220degree c. while PLLA, which has a processing temperature of about 1 80 to 1 90.degree. C, can be used for melt compounding with paclitaxel only. For another example, Poly(glycol ide-caprolactone) copolymer (65/35), wh ich has a processing temperature of about 120. degree. C, can be used for melt compounding with cladribine, which has a melting temperature of about 220. degree. C.

Poly(caprolactone-dioxanone) copolymer (95/5), which has a processing temperature of about 80 to 1 00. degree. C, can be used for melt compounding with sabeluzole, which has a melting temperature of about 1 1 0. degree. C.

[01 02] Therefore, in one aspect of the present invention is to provide methods to maintain drug-contain ing tube, or at least a portion thereof, in the more stable crystalline phase. Preferably, but not necessarily, the

drug-containing polymeric tube of the present invention contain little or no amorphous therapeutic agents, i.e., a major portion (i.e., >50%) of the therapeutic agents contained in such compositions are in the stable crysta l l ine phase. For example, the drug-containing polymeric tube of the present invention each comprises at least one therapeutic agent encapsulated in at least one biocompatible polymer, while more than 75% of the therapeutic agent in the composition is crystalline. More preferably, more than 90% or more than 95% of the therapeutic agent in the composition is crystalline. Most preferably, the composition is essentially free of amorphous therapeutic agent.

Polymeric and Drug Molecular Orientation

[01 03] General ly, application of strain radically and axially can induce both the polymer and drug molecular orientation along the d irection of strain which can increase the strength and modulus along the direction of strain. 101 04] A technique for the radial axial deformation of a tube is blow molding. The polymeric tube is placed in a mold, and applied strain axial ly. The tube is deformed in the both radial and axial direction by appl ication of a pressure from a air. The pressure expands the tube such that it contacts the walls of the mold, the strain strength the tube axially. The mold may act to l imit the radial deformation of the polymeric tube to a particular diameter, the inside diameter of mold. And the axially expansion was controlled by the weight appl ied to the tube.

[0 i 05] During the blow molding, the polymer tube may be heated by a heated gas or fluid or water, or the mold may be heated, thus heating the polymer tube within. After the tube has been blow molded to a particular d iameter, the tube can be maintained under the elevated pressure and temperature for a period of time. The period of time may be between about one minute and about one hour, or more narrowly, between about two m inutes and about ten minutes. This is referred to as "heat setting."

[01 06] As polymer chains have greater mobil ity above T.sub.g, maintain ing the polymer tube in a deformed state at a temperature above the T.sub.g, that is heat setting the tube, allows the chains to rearrange closer to a thermodynam ically equilibrium condition. Also, for polymers that are capable of crystallization, crystal lization occurs at temperatures between the glass transition temperature and the melting temperature.

[ 1 07] Thus, during radial and axial expansion the tube may be at a temperature between the glass transition temperature and the melting temperature. After expansion, the tube may remain in the mold for a period of time at the elevated temperature of expansion. As an example, the polymer may be exposed to a temperature of about 80. degree. C. to 160.degree. C. for the duration of processing, about 3- 1 5 minutes, and optionally heat set afterwards.

Stent Cutting

[01 08] Once the polymeric tube has been formed, and optionally radially expanded, a stent pattern is cut into .

tlie tube. The stent pattern may be formed by any number of methods including chemical etching, mach in ing, and laser cutting. Laser cutting general ly results in a heat affected zone (HAZ). A HAZ refers to a portion of a target substrate that is not removed, but is still exposed to energy from the laser beam, either directly or indirectly.

Direct exposure may be due to exposure to the substrate from a section of the beam with an intensity that is not great enough to remove substrate material through either a thermal or nonthermal mechan ism. A substrate can also be exposed to energy indirectly due to thermal conduction and scattered radiation. The exposure to increased temperature in a HAZ may lead to polymer degradation.

[0 1 09] In some embodiments, the extent of a HAZ may be decreased by the use of an ultrashort-pulse laser. This is primari ly due to the increase in laser intensity associated with the ultrashort pulse. The increased intensity results in greater local absorption. "U ltrashort-pulse lasers" refer to lasers having pulses with durations shorter than about a picosecond (= I O.sup.- l 2), and includes both picosecond and femtosecond (= 1 0.sup.- l 5) lasers. Other embodiments include laser machining a stent pattern with a conventional continuous wave or long-pulse laser (nanosecond ( 10. sup. -9) laser) which has significantly longer pulses than utlrashort pulse lasers. There is a larger HAZ for a continuous or long-pulse laser as compared to an ultrashort pulse laser, and therefore the extent of polymer degradation is higher.

[01 1 ] Further embodiments can include fabricating a stent delivery device by crimping the stent on a support element such as a catheter bal loon, such that the temperature of the stent during crimping is above an ambient temperature. Heating a stent during crimping can reduce or el iminate radially outward recoiling of a crimped stent which can result in an unacceptable profile for delivery. Crimping may also occur at an ambient temperature. Thus, crimping may occur at a temperature ranging from 30. degree. C. to 60. degree. C. for a duration ranging from about 60 seconds to about 5 minutes.

[01 1 1 ] Once the stent has been crimped onto a support element, such as without limitation, a catheter bal loon, the stent delivery device is packaged and then sterilized. Ethylene oxide steril ization, or irradiation, either gamma irradiation or electron beam irradiation (e-beam irradiation), are typical ly used for terminal steri lization of medical devices. For ethylene oxide steril ization, the medical device is exposed to liquid or gas ethylene oxide that steri lizes through an alkal ization reaction that prevents organisms from reproducing. Ethylene oxide penetrates the device, and then the device is aerated to assure very low residual levels of ethylene oxide because it is high ly tox ic. Thus, the ethylene oxide steri l ization is often performed at elevated temperatures to speed up the process.

Moisture is also added as it increases the effectiveness of ethylene oxide in elim inating microorgan isms. Polymer degradation may occur due to the ethylene oxide itself interacting chemically with the polymer, as well as result from higher temperatures and the plasticization of the polymer resulting from absorption of ethylene oxide. More importantly, polymer degradation can occur from the combination of heat and moisture.

[01 12] Alternatively, irradiation may be used for terminal sterilization. It is known that radiation can alter the properties of the polymers being treated by the radiation. High-energy radiation tends to produce ionization and excitation in polymer molecules. These energy-rich species undergo d issociation, subtraction, and addition reactions in a sequence leading to chemical stability. The degradation process can occur during, immed iately after, or even days, weeks, or months after irradiation which often results in physical and chemical cross-l inking or chain scission. Resultant physical changes can include embrittlement, discoloration, odor generation, stiffening, and softening, among others.

[01 13] In particular, the deterioration of the performance of polymers due to e-beam radiation sterilization has been associated with free radical formation during radiation exposure and by reaction with other parts of the polymer chains. The reaction is dependent on e-beam dose, temperature, and atmosphere present. Additiona lly, exposure to radiation, such as e-beam, can cause a rise in temperature of an irradiated polymer sample. The rise in temperature is dependent on the level of exposure. In particular, the effect of radiation on mechanical properties may become more pronounced as the temperature approaches and surpasses the glass transition temperature, T.sub.g. The deterioration of mechanical properties may result from the effect of the temperature on polymer morphology, but also from increased degradation resulting in a decrease in molecular weight. As noted above, degradation may increase above the glass transition temperature due to the greater polymer chain mobi lity.

[0 1 14] Thus, in some embodiments sterilization by irradiation, such as with an electron beam, may be performed at a temperature below ambient temperature. As an example, without limitation, steri lization may occur at a temperature in the range of about -30. degree. C. to about 0. degree. C. Alternatively, the stent may be cooled to a temperature in the range of about -30.degree. C. to about 0. degree. C, and then steri l ized by e-beam irrad iation. The steril ization may occur in multiple passes through the electron beam. In other embod iments, steri l ization by irradiation, such as with an electron beam, may occur at ambient temperature.

[01 1 5] As outl ined above, the manufacturing process results in the polymer and drug's exposure to high temperatures and other potential sources of degradation, such as without limitation, irradiation, moisture, and exposure to solvents. In addition, residual catalysts in the polymer raw material, and other metals, such as from processing equipment, may catalyze degradation reactions. The polymer and drug are also exposed to shear stress, particularly during extrusion. Thus, there are a number of sources of potential polymer and drug degradation .

[01 16] Polymer molecular weight may significantly decrease during the processing operations used in the manufacture of a stent. A non-limiting example is the use of a PLLA polymer to manufacture a stent. The stent manufacturing process involves extruding a polymer tube, radially expanding the polymer tube, laser cutting a stent pattern into the tube to form a stent, crimping the stent onto a bal loon catheter, and sterilizing the crimped stent. The entire process results in a decrease of the weight average molecular weight from about 550 kg/mol to about 1 90 kg/mol. Extrusion of the polymer tube results in a decreases to about 380 Kg/mol from the in itial 550 kg/mol. The molecular weight is further decreased to about 280 kg/mol after radial expansion and laser cutting. After steri lization by electron beam irradiation (25 KGy), the molecular weight (weight average) is about 1 90 kg/mol.

[01 1 7] In general, the decomposition of a polymer, for example a biodegradable polyester such as, without limitation, PLLA, is due to exposure to heat, light, radiation, moisture, or other factors. As a result, a series of byproducts such as lactide monomers, cyclic oligomers and shorter polymer chains appear once the formed free rad icals attack the polymer chain. In addition, decomposition may be catalyzed by the presence of oxygen, water, or residual metal such as from a catalyst. More specifically the polyester poly(L-lactide) is subject to thermal degradation at elevated temperatures, with sign ificant degradation (measured as weight loss) occurring at about 1 50. degree. C. and higher temperatures. The polymer is subject to random chain scission. To explain the presence of lactide at higher temperatures, some have postulated the existence of an equilibrium between the lactide monomer and the polymer chain. In addition to lactide, the degradation products also include aldehydes, and other cyclic ol igomers. Although the degradation mechanisms of PLLA are not fully understood, a free radical chain process can be involved in the degradation. Other mechanisms include depolymerization due to attack by the hydroxy! groups at the chain ends, ester hydrolysis occurring anywhere on the polymer due to water, and thermally driven depolymerization occurring anywhere along the polymer chain. In the cases of depolymerization occurring by backbiting from the terminal hydroxy! groups or thermally driven along the polymer backbone, these process may be especially accelerated by the presence of polymerization catalysts, metal ions, and Lewis acid species.

[01 1 8] In some embodiments, the fabrication of the implantable medical device may include at least one melt processing operation, while others may include at least two operations where the processing temperature is above the glass transition temperature of the polymer. In some embodiments, the fabrication of the implantable medical device may include at least one melt processing operation and at least one additional operation where the processing temperature is above the glass transition temperature of the polymer. The various processing operations may occur at a temperature of at least 160.degree. C, at least 1 80.degree. C, at least 200.degree. C, or at least 21 0. degree. C.

10 1 1 9] In some embodiments, the fabrication of the implantable medical device may include any of the processing operations previously discussed above. These processing operations include forming a drug-containing polymeric tube using extrusion, radially deforming the formed tube, forming a stent from the deformed tube, crimping the stent, and steril izing the stent wherein the order of the steps is as presented except that steril ization could be carried out at any earlier point in the process. The various embodiments encompass al l of the variations in the processing operations discussed above.

EXA M PLES

[0 1 20] Example 1 : Biodegradable Polyester polymer (PLLA) and Drug Crystall ine

PLLA ( melting point 1 50- 1 80 degree c. ) with pel let size of approximately 2mm were first grinded own to less than 500um with a dry m il l and then further grind it down to less than l OOnm using a jet mi l l. The drug Sirol imus and Paclitaxe! powder were grinded directly in to less than l OOnm using a jet m ill . Premixing the polymer and drugs in a mixer with the polymer to drug ration of 98:2 (by weight), wherein the sirolimus and pacl itaxe! ration is 1 : 1 by weight.

Examples 2: Pacl itaxe! and Sirolimus Containing-Biodegradable Tube Extrusion

[0 1 2 1 ] 200g of premixed drug-polymeric composition prepared in example 1 were dried overnight at 45 degree C. The extrusion temperature was set at 160 degree C with the screw speed of 20RPM . The extruded paclitaxe! and sirol imus-contain ing biodegradable tube have outside diameter of 1 .8mm, wal l thickness of I 50um. The fina l tube contain, by weight, one percent sirolimus and one percent of pacl itaxel in at least a portion of crystal l ine structure.

Examples 3 : Polymer and Drug Molecular Orientation

[0122] The paclitaxel and sirolimus-contain ing tube formed in the example 2 was further deformed by using a blow molding technique. In the study, the tube was put through a metal mold with an inside diameter of 2. Omni and pressurized with air at 1 0PS1. Heat the metal mold to 60 degrees ( 1 0 degree above PLLA's glass transition temperature), hold the tube inside the mold for 30 seconds and then cool the tube quickly to room temperature. Both the drug and polymer's molecules were orientated in both radial and axial direction. Example 4: Laser Cutting the Drug-Containing Biodegradable Tube

[01 23] The drug-containing biodegradable tube deformed in example 3, were further cut with a femtosecond u ltra-pulse laser according to the design specification. Figure 1 is the image of cut stent with the invented drug-polymer tube.

Example 5 : H PLC Analysis of Sirolimus and Paclitaxel in the Formed Tube

[() 1 24] To determine the stability of sirolimus and paclitaxel in the formed drug-containing biodegradable tube, 1 Omg of drug-polymer composition mixture and one stent were placed in 1 ml extracting solution (50% ethanol and 50% methanol) and continuously shaken at room temperature overnight. The 1 0 μΙ extracting solutions were further analyzed by HPLC ( HP1 6 series 1 090, Hewlett-Packard Co. Palo Alto, CA). The samples were analyzed on a C I 8-reverse phase column (HP: 4.6 X 100mm RP1 8) using a mobile phase consisting of 0.005% TFA buffer (0.05ml Trifluoroacetic acid in 1 000ml acetonitrile) delivered at a flow rate of 1 .0 mL/min. Paclitaxel and Sirolimus peaks were detected by UV between 21 8nm and 280nm in both premixed drug-polymer composition and stent. Figure 2 depicts the HPLC analysis of Sirolimus and Paclitaxel in both pre-extrusion (A) and stent (B) Example 6: Drug Violability Investigation

[0125] To further investigate the violability of drugs encapsulated inside the stent, both tubes, 5g in each, extruded from the PLLA-only and drug-polymer composition were put into 50ml drug releasing med ia ( 1 X cel l culture media(M B 752/1 , GI BCO) for 4weeks at 37 degree C. At four weeks, the media was steri l ized and further used to culturing the smooth muscle cells (cell type) for one week. After one week, the total cell number in the drug-PLLA group is significantly less than that in PLLA group indicating that the drug are viable and can effectively inhibit smal l muscle prol iferation.

Example 7: Drug-containing Polymeric Stent In Vivo Performance and Safety

[0126] To further investigate the in vivo performance and safety of the invented drug-containing polymeric stent, twelve drug-containing polymeric stents, six from PLLA and six from PLLA blended with ACP polymer (both stents were encapsu lated with sirolimus and paclitaxel as described in the invention) were implanted into pig coronary artery for one month. In the study, all twelve stents were successfully implanted into twelve pig's coronary artery without any difficulties. All animal survived one month study period. At one post implantation, all stented coronary artery remain patency, no any thrombus was found in all twelve animals. The percentage of in-stent restenosis in PLLA/ACP stent group were significantly lower than that in PLLA only group (PLLA/ACP vs. PLLA: 50% vs.71 %, P<0.005). PLLA/ACP made stent have significantly larger residual arterial lumen that thai in the PLLA stent group indicating the PLLA/ACP stent have better radial strength than that PLLA on ly stent, Figure 3 depicts the restenosis different between drug encapsulated PLLA and PLLA/ACP stents in pig coronary artery at one month post implantation. Figure 4 are the h istological images shown the different of neointima and residual arterial lumen area between two groups.

Claims

1 . A bioabsorbable drug-eluting stent, the stent comprising: a stent body fabricated from a biodegradable polyester polymer and at least one therapeutic agent encapsulated inside the biodegradable polymer stent body, wherein the at least a port of the therapeutic agent is crystal lize. The therapeutic agent is selected from the groups consisting of immunosuppressant agent.
2. The stent of claim 1 , wherein said immunosuppressant agent is sirol imus or a prodrug or analog thereof.
3. The stent of claim 2, wherein said sirolimus analog and /or prodrug is selected from the group consisting of zotarolimus, tacrol imus, everol imus, biolimus, pimecrolimus, supralimus, temsiroi imus, TAFA 93, invamycin and neuroimmunophi lins, and combinations or analogs thereof.
4. The stent of cla im 1 , wherein said biodegradable polyester polymer is selected from the group consisting of PLGA, PLDLA, PLLA, PLA, PGA etc, wherein the selected polymer has a melting point is lower than that in therapeutic agent's as stated in the claim 2 and 3.
5. The stent of claim 1 , wherein the ratio between said immunosuppressant agent and polyester polymer ranges from 1 :99 to 30:70, by weight.
6. A bioabsorbable drug-eluting stent, the stent comprising: a stent body fabricated from a biodegradable polyester polymer and at least one therapeutic agent encapsulated inside the biodegradable polymer stent body, wherein the at least a port of the therapeutic agent is crystal lize. The therapeutic agent is selected from the groups consisting of anti-neoplastic agent.
7. The stent of claim 6, wherein said anti-neoplastic agent is paclitaxel or a prodrug or analog thereof.
8. The stent of claim 7, wherein said anti-neoplastic agent is selected from the group consisting of carboplatin. vinorelbine, doxorubicin, gemcirabine, actinomycin-D, cisplatin, camptothecin, 5-fluorouraci l, cyclophospham ide, 1 -β-D-arabinofuranosylcytosine, and combinations or analogs thereof.
9. The stent of claim 6, wherein said biodegradable polyester polymer is selected from the group consisting of PLLA. PDLA, PLA, PGA, and PLGA etc, wherein the selected polymer has a melting point is lower than that in encapsu lated anti-neoplastic agent's as stated in the claim 7 and 8.
10. The stent of claim 6, wherein the ratio between said anti-neoplastic agent and polyester polymer ranges from 1 : :99 to 30:70, by weight.
1 1 . A bioabsorbable drug-eluting stent, the stent comprising: a stent body fabricated from a biodegradable polyester and two or more therapeutic agent encapsulated inside the biodegradable polymer stent body, wherein the at least a port of the therapeutic agent is crystall ize. The therapeutic agent is selected from the groups consisting of anti-neoplastic, and immunosuppressant agent and anti-inflammatory agent.
1 2. A stent of claim 1 1 , wherein the said therapeutic agent is the combination of immunosuppressive and neoplastic agent in the ratio of, by weight, ranging from 99: 1 to 1 :99.
1 3. The stent of claim 12, wherein said immunosuppressant agent is sirolimus or a prodrug or analog thereof.
1 4. The stent of claim 1 3, wherein said sirol imus analog and /or prodrug is selected from the group consisting of zotarolimus, tacrol imus, everol imus, biol imus, pimecrolimus, supral imus, temsirolimus, TAFA 93, invamycin and neuroimmunoph i l ins, and combinations or analogs thereof.
1 5. A stent of claim 1 1 , wherein said wherein said anti-neoplastic agent is pacl itaxel or a prodrug or analog thereof.
1 6. The stent of claim 1 5, wherein said anti-neoplastic agent is selected from the group consisting of carboplatin, vinorelbine, doxorubicin, gemcitabine, actinomycin-D, cisplatin, camptothecin, 5-fluorouracil, cyclophosphamide. 1 -β-D-arabinofuranosylcytosine, and combinations or analogs thereof.
1 7. A stent of claim 1 1 , wherein said anti-inflammatory agent is dexamethasone.
1 8. A stent of claim 1 1 , wherein said biodegradable polyester polymer is selected from the group consist i ng of PLG A, PLLA, PLDLA, PLA and PGA etc , wherein the selected polymer has a melting point is lower than that in encapsulated immunosuppressant agent, neoplastic agent and anti-inflammatory agent as stated in the claim 14, and 1 5 and 16 and 1 7.
19. A method of fabricating an drug-containing biodegradable drug-eluting stent, the method comprising:
selecting compoiindable drug-polymer composition, pre-crystallizing both the polymer and therapeutic agent through various nanotechnologies, extruding drug-containing polymeric/drug composition through extrusion or injection molding process, orientating both polymer and drug molecular weight through blow molding technique, and final ly cutting the stent according to the stent design pattern with ultra-pulse laser technology.
20. The method of claim 19, wherein the therapeutic agent must have a higher melting point than that of the biodegradable polymer of which the therapeutic agent needed to be encapsulated.
2 1 . The method of claim 1 9, wherein the polymer and therapeutic agent are pre-crystal l ized by various nanotechnologies.
22. The method of claim 1 9, wherein the drug-containing tube or sheet are extruded or injecting molded at the temperature higher than polymer's melting point, but lower than the encapsulated drug's melting point.
23. The method of claim 22, wherein the pre-crystallized drug and polymer are premixed and extruded or injection molded.
24. The method of claim 22, wherein the pre-crystallized drug are added to the melted polymer separately through a downstream feeder in an extruder.
25. The method of claim 19, the formed drug-containing tube are deformed axially and radially by using a blow molding techn iques at the temperature of 1 0 degree c above the polymer's glass transition point (Tg).
26. The method of claim 19, the deformed drug-containing tube is cut with ultra short pulse laser to deigned stent specification.
27. The method of claim ! 9, further comprising crimping the stent onto a support member after coating the stent and prior to sterilizing the stent.
PCT/CN2011/002168 2010-12-24 2011-12-23 Biodegradable drug eluting stent and methodsof making the same. WO2012083594A1 (en)

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