Patent Application
20100324645
The present invention is related to the delivery of drugs from an insertable medical device. More particularly, the present invention relates to a coated angioplasty balloon and the pharmacokinetic profile of the released drug from the tissue.
Atherosclerosis is a syndrome affecting arterial blood vessels. It is a chronic inflammatory response in the walls of arteries, in large part due to the accumulation of blood cells and promoted by low density lipoproteins and the formation of plaque on the arterial wall. Atherosclerosis is commonly referred to as hardening of the arteries. Angioplasty is a vascular interventional technique involving mechanically widening an obstructed blood vessel, typically caused by atherosclerosis.
During angioplasty, a catheter having a tightly folded balloon is inserted into the vasculature of the patient and is passed to the narrowed location of the blood vessel at which point the balloon is inflated to a fixed size using fluid pressures. Percutaneous coronary intervention (PCI), commonly known as coronary angioplasty, is a therapeutic procedure to treat the stenotic coronary arteries of the heart, often found in coronary heart disease.
Peripheral angioplasty, commonly known as percutaneous transluminal angioplasty (PTA), refers to the use of mechanical widening of blood vessels other than the coronary arteries. PTA is most commonly used to treat narrowing of the leg arteries, especially, the iliac, external iliac, superficial femoral and popliteal arteries. PTA can also treat narrowing of veins, and other blood vessels.
It was found that following angioplasty, although a blood vessel would be successfully widened, sometimes the treated wall of the blood vessel becomes weakened after balloon inflation or dilatation, causing the blood vessel to collapse after the balloon is deflated or later. Interventional cardiologists addressed this problem by stenting the blood vessel to prevent collapse. A stent is a device, typically a metal tube or scaffold, that was inserted into the blood vessel following angioplasty, in order to hold the blood vessel open.
While the advent of stents eliminated many of the complications of abrupt blood vessel collapse after angioplasty procedures, it was found that within about six months of stenting a re-narrowing of the blood vessel often persisted, a condition known as restenosis. Restenosis was discovered to be a “controlled injury” of the angioplasty procedure and was characterized by a growth of smooth muscle cells—analogous to a scar forming over an injury. It was thought that drug eluting stents were the answer to the reoccurrence of narrowing of blood vessels after stent implantation. A drug eluting stent is a metal stent that has been coated with a drug that is known to interfere with the process of re-narrowing of the blood vessel (restenosis).
One drawback of drug eluting stents is a condition known as late stent thrombosis, an event in which blood clots inside the stent. Thrombosis is fatal in over one-third of cases. Drug eluting balloons are believed to be a viable alternative to drug eluting stents in the treatment of atherosclerosis. In a study which evaluated restenosis and the rate of major adverse cardiac events such as heart attack, bypass, repeat stenosis, or death in patients treated with drug eluting balloons and drug eluting stents, the patients treated with drug eluting balloons experienced only 3.7 percent restenosis and 4.8% MACE as compared to patients treated with drug eluting stents, in which restenosis was 20.8 percent and 22.0 percent MACE rate. (See, PEPCAD II study, Rotenburg, Germany).
Although drug eluting balloons are a viable alternative and in some cases appear to have greater efficacy than drug eluting stents as suggested by the PEPCAD II study, drug eluting balloons present challenges due to the very short period of contact between the drug coated balloon surface and the blood vessel wall. In particular, a non-perfusion balloon can only be inflated for less than one minute, and is often inflated for only thirty seconds which would otherwise starve distal regions of oxygenated blood. Therefore, an efficacious, therapeutic amount of drug must be transferred to the vessel wall within a thirty second to one minute time period. Thus, there are challenges specific to drug delivery via a drug coated balloon because of the necessity of a short inflation time, and therefore time for drug or coating transfer—a challenge not presented by a drug eluting stent, which remains in the patient's vasculature once implanted.
Other considerations are the current theories about the mechanism by which a drug coated balloon transfers drug to the vessel wall. One theory, for example, is that upon balloon expansion, the drug composition mechanically fractures or dissolves from the coating, diffuses to the vessel wall and then permeates into the vessel wall. A second theory is that upon balloon expansion the balloon coating is transferred to the vessel wall, and then drug permeates into the vessel wall from the coating adhered to the vessel wall. Another theory is that the balloon expansion creates tears and microfissures in the vessel wall and portions of the coating insert into the tears and microfissures. The drug then permeates into the vessel wall from the coating within the tears and fissures. Yet another theory is that upon balloon expansion, a layer of dissolved drug and coating excipients is formed at a high concentration on the vessel wall as a boundary layer. The drug diffuses and permeates from this boundary layer into the vessel wall. In most of these theories, the drug transfers from the balloon to the circulation or the vascular wall tissue upon fracture of the coating due to inflation of the balloon and occurs within one minute, and preferably within 30 seconds. Once the diffused drug is within the vessel tissue, the initial high concentration of drug serves as a reservoir which diffuses into the other surrounding vessel tissue, thereby exhibiting a characteristic pharmacokinetic (PK) release profile. Therefore, a need exists for a drug coated balloon having efficient drug transfer to a vessel wall.
Various embodiments of DC balloons have been proposed, including balloons with a therapeutic agent disposed directly on the balloon surface and balloons having various protective sheaths. However, not all embodiments result in an efficacious response in reducing restenosis after balloon and bare metal stent trauma.
Therefore, a need exists for a drug eluting balloon and more particularly, a balloon coated with a cytostatic therapeutic agent, that provides for an effective pharmacokinetic (PK) profile of drug tissue concentration over time after delivery from this coated balloon.
The purpose and advantages of the disclosed subject matter will be set forth in and apparent from the description that follows, as well as will be learned by practice of the disclosed subject matter. Additional advantages of the invention will be realized and attained by the methods and systems particularly pointed out in the written description and claims hereof, as well as from the appended drawings.
In accordance with one embodiment of the present subject matter, a drug delivery balloon is provided comprising a balloon having a surface, and a coating disposed on at least a portion of the balloon surface, the coating including an cytostatic therapeutic agent, an excipient, and a plasticizer. In accordance with the present subject matter, at least 30% of the coating transfers from the balloon surface within two minutes after inflation of the balloon. Alternatively, at least 30% of the coating transfers from the balloon surface within two minutes after inflation. Preferably, however, at least 30% of the coating transfers from the balloon surface within two minutes after inflation.
In accordance with another embodiment, at least 50% of the coating transfers from the balloon surface within two minutes after inflation of the balloon. In accordance with yet another embodiment, at least 90% of the coating transfers from the balloon surface within two minutes after inflation of the balloon.
In accordance with the present subject matter, a sufficient drug concentration is deposited at the targeted tissue site of interest such that the resulting pharmacokinetic (pK) profile, or decline in tissue concentration with time, can provide the local drug concentration necessary to inhibit restenosis.
In accordance with a preferred embodiment, the cytostatic therapeutic agent includes macrolide immunosuppressive, macrolide antibiotics, rapamycin, protaxel, taxanes, docetaxel, zotaroliums, novolimus, zotarolimus, everolimus, sirolimus, biolimus, myolimus, deforolimus, tacrolimus, or temsirolimus compounds, structural derivatives and functional analogues of rapamycin, structural derivatives and functional analogues of everolimus, structural derivatives and functional analogues of zotarolimus, everolimus, sirolimus, biolimus, myolimus, deforolimus, tacrolimus, or temsirolimus compounds.
In accordance with a preferred embodiment of the invention, the excipient is biocompatible. For example, some non-limiting examples of suitable excipients include polyvinylpyrrolidone (PVP), polysorbates such as Tween 80 or Tween 20, polyethylene glycol or any combination thereof. In one embodiment, the PVP is preferably not substantially cross-linked and preferably is not a hydrogel. The plasticizer is preferably biocompatible. Some nonlimiting suitable plasticizers glycerol, ethanol, polyethylene glycol, propylene glycol, benzyl alcohol, N-methylpyrrolidone, Cremophor EL, dimethylsulfoxide, water, sucrose, sorbitol, or a blend thereof.
In accordance with the invention, a balloon catheter is provided for delivering a therapeutic agent to the vasculature of a patient and also other target tissues. The tissue can be a blood tissue, a blood vessel (such as a peripheral or coronary artery), or a blood vessel within an organ or a muscle.
In accordance with the invention, the coating of the drug delivery balloon is designed to produce a pK profile in the vasculature or target tissue that can provide controlled release of the cytostatic drug. Preferably, the pK profile provides for a local therapeutic agent concentration necessary to inhibit restenosis. In accordance with one embodiment of the invention, the coating achieves detectable amounts of the cytostatic drug in a tissue over a period of at least one week post delivery of the drug.
In accordance with a preferred embodiment, the coating of the drug delivery balloon produces a pK profile with a zotarolimus tissue concentration half life in the range of 24 to 96 hours. In accordance with yet another embodiment, the coating of the drug delivery balloon produces a pK profile with an everolimus tissue concentration half life in the range of 18 to 48 hours. Preferably, and in accordance with the invention, the desired pK profile produces an acute tissue concentration in the range of 10-1000 ng/mg.
In accordance with one aspect, the coating of the drug delivery balloon includes everolimus and the everolimus has a concentration between 88 to 1500 μg/cm2, preferably 500 to 1500 μg/cm2.
In accordance with another aspect, the coating of the drug delivery balloon includes zotarolimus and the zotarolimus has a concentration between 15 to 1500 ug/cm2, preferably 15 to 600 ug/cm2.
In accordance with one embodiment, the cytostatic concentration in the blood system increases as a function of time with Tmax ranging from 1 to 3 hours and Cmax ranging from 2 to 40 ng/mL or 0.02 to 0.05 ng/mL/ug as a function of coating formulation. In this regard, the zotarolimus concentration in the blood system does not exceed a Cmax 111 ng/ml 2 hours post balloon inflation when normalized to total dosage. In another embodiment, the cytostatic concentration normalized to a total dosage in a subject's blood does not exceed 0.1 ng/ml/ug 5 hours post inflation.
In accordance with a further embodiment, the drug delivery balloon is a perfusion balloon and includes a coating disposed on at least a portion of the surface of the perfusion balloon, wherein the coating includes having an cytostatic therapeutic agent, an excipient, and a plasticizer, and further wherein at least 30% of the coating transfers from the balloon surface within ten minutes after inflation of the balloon. In another embodiment, the drug delivery balloon can be mounted on a catheter with perfusion ports.
It is to be understood that both the foregoing description is exemplary and is intended to provide further explanation of the invention claimed to a person of ordinary skill in the art. The accompanying drawings are included to illustrate various embodiments of the invention to provide a further understanding of the invention. The exemplified embodiments of the invention are not intended to limit the scope of the claims.
The disclosed subject matter will now be described in conjunction with the accompanying drawings in which:
Reference will now be made in detail to the various aspects of the disclosed subject matter. The method and corresponding steps of the invention will be described in conjunction with the detailed description of the device, the figures and examples provided herein.
The devices and methods presented can be used for treating the lumen of a patient. In particular, the invention is particularly suited for treatment of the cardiovascular system of a patient, such as performance of angioplasty and delivery of a balloon expandable medical device, such as a stent, filter and coil.
In accordance with the invention, a balloon catheter is provided for delivering a therapeutic agent to the vasculature of a patient and also other target tissues. The balloon catheter has an elongate member having a proximal end, a distal end, and a lumen therebetween. An expandable balloon is disposed near the distal end of the elongate tubular member. A coating is applied to at least a portion of the balloon catheter, the coating including an cytostatic therapeutic agent, an excipient and a plasticizer. The term “cystostatic” as used herein refers to a drug or compound which possesses the dual properties of mitigating cell proliferation and allowing cell migration. The drug delivery balloon and its coating is configured so that at least 30% of the coating transfers from the balloon surface within two minutes after inflation of the balloon. Preferably, however, at least 90% of the coating transfers from the balloon surface within two minutes after inflation of the balloon and more preferably at least 50 to at least 75 percent of the coating transfers from the balloon surface within two minutes after inflation of the balloon.
In accordance with a further embodiment, the coating of the drug balloon catheter produces a pharmacokinetic profile that provides the therapeutic agent to the vasculature or target tissue in a sufficient and effective concentration. This concentration is effective in preventing or inhibiting restenosis. Indeed, the resulting pK profile or decline in tissue concentration with time can provide the therapeutic agent at a concentration necessary to prevent or inhibit restenosis. Pharmacokinetics includes the study of the mechanisms of absorption and distribution of an administered drug, the rate at which a drug action begins and the duration of the effect, the chemical changes of the substance in the body (e.g. by enzymes) and the effects and routes of excretion of the metabolites of the drug. Pharmacokinetic analysis is performed by noncompartmental (model independent) or compartmental methods. Noncompartmental methods estimate the exposure to a drug by estimating the area under the curve of a concentration-time graph. Compartmental methods estimate the concentration-time graph using kinetic models. Compartment-free methods are often more versatile in that they do not assume any specific compartmental model and produce accurate results also acceptable for bioequivalence studies.
An exemplary embodiment of balloon catheter device in accordance with the present invention is shown schematically in
The elongated catheter shaft 12 comprises an outer tubular member 14 and an inner tubular member 16. The outer tubular member 14 defines an inflation lumen 20 that can be disposed between the proximal end portion and the distal end portion of the catheter shaft 12. Specifically, as illustrated in
In accordance with the invention, a drug delivery balloon having a coating including an cytostatic therapeutic agent, an excipient and a plasticizer is configured such that at least 30% of the coating transfers from the balloon surface within two minutes after inflation of the balloon. Furthermore, the drug delivery balloon of the present invention contains a coating and the resulting pK profile based upon the coating demonstrates that a sufficient therapeutic agent concentration is deposited at the tissue site of interest. The resulting PK profile itself, or decline in tissue concentration with time, provides the therapeutic agent at a concentration necessary to inhibit and/or prevent restenosis.
The coating of the drug delivery balloon of the present invention is configured such that at least 30% of the coating transfers from the balloon surface within two minutes after inflation of the balloon. In accordance with the invention, the coating can be applied to the medical device by processes such as dip-coating, pipette coating, syringe coating, air assisted spraying, electrostatic spraying, piezoelectric spraying, electrospinning, direct fluid application, or other means as known to those skilled in the art. The coating can be applied over at least a portion or the entirety of the balloon or medical device. By way of example, and not limitation, certain coating processes that can be used with the instant invention are described in U.S. Pat. No. 6,669,980 to Hansen; U.S. Pat. No. 7,241,344 to Worsham; and U.S. Publication No. 20040234748 to Stenzel, the entire disclosures of which are hereby incorporated by reference. In accordance with one embodiment of the invention, the medical device is a balloon catheter and the coating can be applied to either a folded or inflated balloon. Furthermore, the coating can be directly applied into the folds of the folded balloons. The coating characteristics are affected by process variables. For example, for dip-coating process, coating quality and thickness can vary as an effect of variables such as number, rate, and depth of dips along with drying time and temperature. In accordance with a preferred embodiment, the coating is applied via a Sonotek piezoelectric spray coater modified to fully inflate and rotate the angioplasty balloon subassemblies.
In accordance with a preferred embodiment, after coating, the subassembly is baked dry, and then tri-folded and heat set to a low profile of 0.053″ or less. An optional bare metal stent can then be crimped onto the balloon using an icy hot or other process. The balloon is then sheathed and a full-length catheter is heat or laser bonded before being packaged and either EtO or e-beam sterilized.
The coating is thus designed to wet and/or swell during folded balloon delivery and tracking. During one or more inflations, and contact with the vessel wall for less than two minutes, preferably less than one minute, depending on the particular type of cytostatic drug coated on the balloon surface, at least 30% of the coating transfers from the balloon surface. The fast dissolution of the coating results in effective release of the therapeutic agent to the vasculature or target tissue site of interest. Following delivery of the therapeutic agent to the site of interest, the balloon is rapidly deflated and removed.
In accordance with the invention, excipients are utilized together with the therapeutic agent in the coating at ratios ranging from 1:20 to 20:1 excipient:drug by weight, preferably from 1:10 to 2:1, more preferably from 1:3 to 1:1. The excipients provide improved release from the balloon, improved tissue uptake and retention, enhanced adhesion, and/or product stability and shelf life. In the absence of an excipient, a pure drug would be expected to produce the lowest coating profile or thickness at the same dosage and coating uniformity.
In accordance with a preferred embodiment, the excipients of the present invention are water soluble. The excipients can include non-ionic hydrophilic polymers. Non-ionic hydrophilic polymers include, but are not limited to, poly(vinyl pyrrolidone) (PVP, Plasdone, povidone), silk-elastin like polymer, poly(vinyl alcohol), poly(ethylene glycol) (PEG), pluronics (PEO-PPO-PEO), poly(vinyl acetate), poly(ethylene oxide) (PEO), PVP-vinyl acetate (copovidone), PEG phospholipids, and polysorbates such as polysorbate 20 (Tween 20). Preferably, the molecular weight of non-ionic hydrophilic polymers can be less than 50 kDa for fast solubility. The excipient can also include fatty acids. Further, the excipient can be a lubricious material which improves spreading and uniformity of coating.
In addition, a plasticizer can be added to the binder to keep it soft and pliable. Plasticizers can allow for greater coating flexibility and elongation to prevent coating cracking during inflation or brittleness. Plasticizers include, but are not limited to, glycerol, ethanol, dimethylsulfoxide, triethyl citrate, tributyl citrate, acetyl tributyl citrate, acetyl triethyl citrate, dibutyl phthalate, dibutyl sebacate, dimethyl phthalate, triacetin, polyethylene glycol, propylene glycol, 2-pyrridone, benzyl alcohol, N-methylpyrrolidone, Cremophor EL, sucrose, sorbitol, water, and combinations thereof. Preferably, a biocompatible plasticizer is used.
In accordance with yet another embodiment, anti-coagulants can be used as a binder for the particles. For example, heparin based polysaccharides can provide a minimally thrombogenic surface to prevent blood clotting on the balloon surface or minimize platelet activation induced by the procedure. Heparin based polysaccharides include, but are not limited to, heparin, heparin sulfate, heparin disaccharides, heparin fraction 1, heparin fraction 2, low molecular weight heparin, heparin ammonium, heparin calcium, heparin lithium, heparin lithium, and heparin zinc lithium. Low molecular weight heparin includes centaxarin, periodate-oxidized heparin, heparin sodium end-amidated, heparin sodium, and nitrous acid delaminated.
In accordance with a preferred embodiment of the invention, the excipient possesses a mucoadhesive property. This mucoadhesive property of the binder will lead to longer drug retention within the coating adhered to the vessel wall. In particular, charged excipients such as chitosan, polyacrylic acid, polyglutamic acid, some polysaccharides (e.g. carboxymethylcellulose (CMC), sodium hyaluronate, sodium alginate) and some non-ionic hydrophilic polymers exhibit mucoadhesive properties. Any above carboxylated materials can also be lightly activated with esters such as nitrophenolate or NHS-esters (N-hydroxy succinimide) for increased mucoadhesiveness. Alternatively, any above materials can be lightly thiolated for increased mucoadhesiveness and continued solubility.
Additionally or alternatively, the excipient is or includes a contrast agent, including but not limited to, Iopromide (Ultravist), Ioxaglate (Hexabrix), Ioversol (Optiray), Iopamidol (Isovue), Diatrixoate (Conray), Iodixanol (Visipque), and Iotrolan. At an intermediate coating thickness, a lower molecular weight (<1 kDa) hydrophilic contrast agent such as Iopromide (Ultravist) would enable faster therapeutic release and a slightly higher viscous coating of the vessel wall as compared with drug alone.
In accordance with one embodiment, polyvinylpyrrolidone (PVP) having a MW of 100 kDa or less would be expected to provide a means of faster coating release and increased mucoadhesiveness against the vessel wall. The swellable nature of this non-ionic hydrophilic polymer when hydrated and especially when plasticized with glycerol produces a thicker and toughened coating.
The cytostatic therapeutic agent is present in the coating in a therapeutic amount. Some non-limiting examples of cytostatic therapeutic agents include marcrolide immunosuppressive drugs, macrolide antibiotics, rapamycin, protaxel, taxanes, docetaxel, everolimus, zotaroliums, sirolimus, biolimus, myolimus, deforolimus, tacrolimus, or temsirolimus, structural derivatives and functional analogues of rapamycin, structural derivatives and functional analogues of everolimus, structural derivatives and functional analogues of zotarolimus, sirolimus, bicytostatic, mycytostatic, deforcytostatic, or temsirolimus compounds.
For example and not limitation, the coating can include a therapeutic agent in addition to the cytostatic drug. In this regard, the therapeutic agent can include anti-proliferative, anti-inflammatory, antineoplastic, antiplatelet, anti-coagulant, anti-fibrin, antithrombotic, antimitotic, antibiotic, antiallergic and antioxidant compounds, HMG-CoA reductase inhibitors, and peroxisome proliferator-activated receptor α (PPAR α) agonists such as fenofibrates (clofibrate, ciprofibrate, benzafibrate, and Tricor and Trilipix ABT-335). Thus, the therapeutic agent can be, again without limitation, a synthetic inorganic or organic compound, a protein, a peptide, a polysaccharides and other sugars, a lipid, DNA and RNA nucleic acid sequences, an antisense oligonucleotide, an antibodies, a receptor ligands, an enzyme, an adhesion peptide, a blood clot agent including streptokinase and tissue plasminogen activator, an antigen, a hormone, a growth factor, a ribozyme, and a retroviral vector.
As illustrated in Example 2, described in detail below, balloons coated with everolimus formulations were evaluated. The three formulations are summarized in Table 1 and the experimental procedures and details are described in Example 2, below. In brief, balloon expansion was performed in healthy domestic porcine coronary arteries. The balloons were maintained expanded in position for 30 seconds. The animals were sacrificed after 24 hours and 72 hours after balloon dilation and drug delivery after which the concentration of the everolimus in the arterial tissue at the expansion sites was measured.
As illustrated in
The equation for the exponential decay model is:
C
T
=C
0 exp−kT (EQ. 1)
where CT is the concentration at time T, C0 is the concentration at time zero, and k is the decay constant. The results of the pK data assuming a one component model with an exponential decay are summarized in Table 2.
In Table 2, the initial concentration (C0) values of everolimus concentration in the tissue are indicative of the concentrations at T=0. However, the actual C0 tissue concentrations are higher. This is because at short times the transferred coating system is heterogeneous and the entire drug has not actually or totally dissolved into the tissue. Indeed, some of the drug is still present as films or particulates pressed onto or into the vessel wall. The maximum tissue concentrations appear to be more a function of the amount of drug on the balloon rather than which of these three formulations was used. As illustrated in Table 2 above, the decay constants (k) are quite similar, thus indicating that the decrease in drug concentration over time was not dependent on which of the three formulations was used. This indicates that once the drug has dissolved into the tissue, the pharmokinetic profile property of the drug is primarily dependent on the chemical characteristics of the drug itself.
For comparative purposes, Table 3 tabulates the concentration of everolimus in tissue using either the everolimus eluting stent system (XIENCE) and the everolimus eluting balloon of the present invention. The results from the pharmacokinetic studies for both the everolimus eluting stent system and everolimus eluting balloon of the present invention are presented as tissue concentrations in Table 3.
At the 1 day and 3 day time-points, the drug-coated balloon tissue concentrations are 10-80 times higher than those seen with drug-eluting stent. However, it is not precisely known how the drug tissue concentration profile relates to efficacy against restenosis in the clinic. Certainly, however, if the tissue concentrations match, or are greater than the drug-eluting stent at time-points out to 7, 14, and perhaps 28 days, then it is reasonable to state that the drug-coated balloon is as effective in reducing restenosis.
In accordance with a further embodiment, tissue concentrations for the drug-coated balloon were extrapolated out to longer time points with the simple exponential model. Although the exponential model is a substantial oversimplification, it can provide order of magnitude estimates. The results of extrapolation to longer time points are summarized in Table 4.
As illustrated in Table 4, the tissue concentrations for the everolimus coated balloons are all equal to or greater than the tissue concentrations from the everolimus drug-eluting sent (XIENCE) out to 7 days. However, according to the model, after seven days, the tissue concentrations drop below the drug-eluting stent. However, based on various trials which have indicated that a fast drug release is highly effective, it is reasoned that an effective tissue concentration out to seven days should be adequate in inhibiting restenosis. The trials which have indicated that a fast drug release is highly effective include, but are not limited to, the sirolimus-eluting stent (Cypher FIM trial), where the quick drug release arm was highly effective. The sirolimus eluting stent had roughly 89% drug release at four days with 98% release at 15 days and was highly effective.
Based on the input parameters in Table 5 below, a pK mathematical fit was performed to further extrapolate information from the pK porcine data. This elimination model assumed that mass of drug was eliminated as a function of disintegration and dissolution and written mathematically as
Where m=mass, K1 and K21 are constants, A=surface area, and initial boundary conditions of m (t=0)=rM0. Interpretations on normalizing pK data as a function of balloon dose are illustrated in
In comparing the results from the mathematical fit model of Equation 2, as summarized in Table 5, the drug delivery balloon of the present invention having a coating including an cytostatic therapeutic agent and excipient provides for an effective transfer of coating from the balloon surface within a short time period. As illustrated in Table 5, the rate constants (K1, K21) for elimination by physical dislodgement and by dissolution/diffusion is similar among different formulations. Furthermore, the thinner and higher concentration coating may have a more effective initial drug uptake. Indeed, the initial mass transfer into the vessel wall is dependent on the coating thickness (0.18, 0.22, 0.31). A brittle coating will have less initial mass transfer to the wall due to greater sensitivity to mechanical perturbation (0.2 vs. 0.3). The everolimus-PVP coating increases toughness and hence obtains higher initial transfer to the tissue when compared to the everolimus-Ultravist coating. According to results of mathematical fit, the thicker coatings may have higher variability in tissue uptake. Further, a coating with a therapeutic agent only behaves similar to coating including both a therapeutic agent and an excipient in both mechanical integrity and local pK.
In accordance with the invention, the everolimus has a concentration between 88 to 1500 ug/cm2 balloon. In accordance with the invention, the released concentration of everolimus in the tissue decreases by more than 50% after about 72 hours post inflation of the balloon. In accordance with yet another embodiment, the released concentration of everolimus in the tissue decreases by more than 90% after about 72 hours post inflation of the balloon. Preferably, the everolimus concentration in the blood system does not exceed 250 ng/ml 24 hours post balloon inflation. In accordance with the invention, the everolimus concentration in the blood system does not exceed 179 ng/ml 24 hours post balloon inflation.
As illustrated in Example 3, described in detail below, balloons coated with zotarolimus formulations were evaluated. The six formulations are summarized in Table 6 and the experimental procedures and details are described in Example 3, below. In brief, balloon expansion was performed in healthy domestic porcine coronary arteries. The balloons were maintained expanded in position for 30 seconds. The animals were sacrificed after 30 minutes, 1 day (zotarolimus alone), and 7 days after delivery and the concentration of the zotarolimus in the arterial tissue at the expansion sites was measured.
Blood zotarolimus concentrations increased as a function of time with Tmax ranging from 1-3 hours and Cmax from 2.1-39.4 ng/mL as a function of coating formulation as summarized in Table 7. The blood concentrations appeared to exist more as a function of dose than excipient once the values were normalized. This trend indicates that excipients may serve more as both a binder and hydrophilic spacer than drug solubilizer.
The data of zotarolimus concentration in the arterial tissue can be further modeled using a pK deconvolution/convolution model to predict blood concentration as function of total dose per each formulation as shown in
For comparative purposes, Table 8 tabulates the concentration of zotarolimus in tissue using either the zotarolimus eluting stent system (Endeavor) and the zotarolimus eluting balloon of the present invention. The results from the pharmacokinetic studies for both the zotarolimus eluting stent system and zotarolimus eluting balloon of the present invention are presented as tissue concentrations in Table 8.
At the 1 day timepoint, the drug-coated balloon tissue concentrations are 1-40 times higher than those seen with drug-eluting stent. However, it is not precisely known how the drug tissue concentration profile relates to efficacy against restenosis in the clinic. Certainly, however, if the tissue concentrations match, or are greater than the drug-eluting stent at time-points out to 7 and perhaps 14 days, then it is reasonable to state that the drug-coated balloon is as effective.
Assuming a one component model with an exponential decay, tissue half lives for the drug can be calculated using the zotarolimus tissue concentration depicted in
This fit provides an estimate for the tissue half-life to be in the range of 31 to 75 hours. The tissue half-life is probably dose dependent but the doses of interest for drug coated balloons lie largely in the range of 88 to 570 ug/cm2. In Table 9, the initial concentration (C0) values of zotarolimus concentration in the tissue are indicative of the concentrations at T=0. However, the calculated value of C0 is much lower than the concentration measured at 30 minutes, therefore, indicating the lack of fit and possible presence of solid drug at short time points.
In accordance with a further embodiment, tissue concentrations for the drug-coated balloon were extrapolated out to longer time points with a non-linear fit model:
Although the non-linear fit model is a substantial oversimplification, it can provide order of magnitude estimates. The results of extrapolation of zotarolimus tissue concentrations to longer time points are summarized in Table 10.
As illustrated in Table 10, the tissue concentrations for the zotarolimus coated balloons are all equal to or greater than the tissue concentrations from the zotarolimus drug-eluting sent (Endeavor) out to 7 days. However, according to the parametric model, after seven days, the tissue concentrations drop below the drug-eluting stent. However, based on various trials which have indicated that a fast drug release is highly effective, it is reasoned that an effective tissue concentration out to seven days should be adequate. The trials which have indicated that a fast drug release is highly effective include, but are not limited to, the sirolimus-eluting stent (Cypher FIM trial), where the quick drug release arm was highly effective. The sirolimus eluting stent had roughly 89% drug release at four days with 98% release at 15 days and was highly effective.
In accordance with the invention, the zotarolimus has a concentration between 15 to 600 ug/cm2. In accordance with the invention, the released concentration of zotarolimus in the tissue decreases by more than 50% after about 72 hours post inflation of the balloon. In accordance with yet another embodiment, the released concentration of zotarolimus in the tissue decreases by more than 90% after about 72 hours post inflation of the balloon. Preferably, the zotarolimus concentration in the blood system does not exceed 232 ng/ml 5 hours post balloon inflation. In accordance with the invention, the zotarolimus concentration in the blood system does not exceed 111 ng/ml 2 hours post balloon inflation.
In accordance with the drug delivery device of the present invention, the use of zotarolimus coated balloons configured to transfer at least 30% of the coating from the balloon surface within two minutes after inflation of the balloon is effective. In accordance with the present invention, tissue concentrations and blood concentrations increased as a function of larger zotarolimus dosage. Furthermore, excipients, such as Ultravist and PVP-glycerol, increased acute drug uptake and tissue concentrations compared with zotarolimus only coatings in conjunction with bare metal stent implantation. In fact, less acute drug uptake resulted from a drug-coated balloon only versus a drug-coated balloon and bare metal stent system.
In accordance with the present invention, the cytostatic coating provides a pharmacokinetic profile post bolus delivery from a drug coated balloon that result in an efficacious response in reduction of restenosis after balloon and bare metal stent trauma. The drug delivery balloon of the present invention having a coating including an cytostatic therapeutic agent and an excipient provides for a bolus release of the cytostatic therapeutic agent with an inflation time of two minutes or less. At least thirty percent of the coating transfers from the balloon surface within two minutes after inflation of the balloon.
In accordance with one embodiment, Cmax, or the maximum tissue concentration, occurs in the time frame of 1-60 minutes, preferably between 10-2000 ng/mg [ng drug/mg tissue], and more preferably between 10-250 ng/mg [ng drug/mg tissue]. In accordance with the invention, in order to achieve the desired pK profile, this Cmax must be at least 10 ng/mg. Preferably, the concentration of cytostatic drugs in the blood system does not exceed 232 ng/ml 5 hours post inflation. More preferably, however, the concentration of cytostatic drugs does not exceed 111 ng/ml 2 hours post inflation.
In a further embodiment, the drug delivery balloon produces a pK profile with a drug tissue concentration half life in the range of about 10 to about 100 hours. However, depending on the drug used the half life can range from about 18 to about 48 hours or about 24 to 96 hours. Furthermore, this desired pK profile should be such that at one day, the tissue concentration of the therapeutic agent is in the range of 10-1000 ng/mg, preferably from 10-250 ng/mg and the seven day tissue concentration of the therapeutic agent is greater than 29 nM.
In accordance with the present invention, the coating provides a controlled release of the cytostatic drug over a period of at least 72 hours post inflation of the balloon. However, in a preferred embodiment, the coating provides a controlled release of the cytostatic drug over a period of at least one week. Moreover, the coating can provide a controlled release of the cytostatic drug over a period of at least two weeks.
The drug delivery balloon of the present invention is effective in that the therapeutic agent is retained in the vessel wall due to the permeation/uptake of drug. When compared to the drug-eluting stent, the drug delivery balloon of the present invention occupies at least 75% of the arterial wall area. Hence the drug tissue concentration, on the average, is three times more uniform with respect to the arterial surface with a drug-coated balloon than with a drug-eluting stent. Furthermore, the pK profile of the cytostatic coating of the present invention within arterial tissue over an efficacious time period eliminates the need for a controlled release polymer coating and therefore can result in decreased polymer-induced inflammation, late stent thrombosis and other improved safety criteria.
In accordance with a further embodiment, tissue uptake of everolimus at distal region, 10-15 mm away from stenting segment, indicates that the drug coated balloon of the present invention may be beneficial for coronary artery diseases with multiple site lesions (site and regional therapy).
In accordance with a further embodiment, the drug delivery balloon is a perfusion balloon and includes a coating disposed on at least a portion of the surface of the perfusion balloon, wherein the coating includes having an cytostatic therapeutic agent, a excipient, and a plasticizer, and further wherein at least 30% of the coating transfers from the balloon surface within ten minutes after inflation of the balloon. Perfusion balloons are described in detail in U.S. Pat. No. 5,951,514 to Sahota, U.S. Pat. No. 5,370,617 to Sahota, U.S. Pat. No. 5,542,925 to Orth, U.S. Pat. No. 5,989,218 to Wasicek, the disclosures of which are incorporated by reference in their entirety herein. In another embodiment, the drug delivery balloon can be mounted on a catheter with perfusion ports as described in U.S. Pat. No. 5,370,617 to Sahota, U.S. Pat. No. 5,542,925 to Orth, and U.S. Pat. No. 5,989,218 to Wasicek, the disclosures of which are incorporated by reference in their entirety herein. Alternatively, the inflation time is 5 minutes or less or the inflation time is 2 minutes or less.
In accordance with the invention, in addition to the relatively long duration effect postulated above, a separate mechanism may be operating with the use of cytostatic type drugs. Indeed, the initial high dose delivered to the tissue may interdict pathways normally below the activity threshold of cytostatic drugs delivered from drug eluting stents. For example, with initial tissue drug concentrations in the 100+μM range, normally inefficient cytokine blockade processes for cytostatic drugs such as blocking monocyte production of TNF-α or IL-6 can occur. This would result in reduction in neointimal formation and inflammation.
In accordance with the invention the balloon is made of a polymeric material. For example, the polymeric material utilized to form the balloon body may be may be compliant, non-compliant or semi-compliant polymeric material or polymeric blends.
In one embodiment, the polymeric material is compliant such as but not limited to a polyamide/polyether block copolymer (commonly referred to as PEBA or polyether-block-amide). Preferably, the polyamide and polyether segments of the block copolymers may be linked through amide or ester linkages. The polyamide block may be selected from various aliphatic or aromatic polyamides known in the art. Preferably, the polyamide is aliphatic. Some non-limiting examples include nylon 12, nylon 11, nylon 9, nylon 6, nylon 6/12, nylon 6/11, nylon 6/9, and nylon 6/6. Preferably, the polyamide is nylon 12. The polyether block may be selected from various polyethers known in the art. Some non-limiting examples of polyether segments include poly(tetramethylene ether), tetramethylene ether, polyethylene glycol, polypropylene glycol, poly(pentamethylene ether) and poly(hexamethylene ether). Commercially available PEBA material may also be utilized such as for example, PEBAX® materials supplied by Arkema (France). Various techniques for forming a balloon from polyamide/polyether block copolymer are known in the art. One such example is disclosed in U.S. Pat. No. 6,406,457 to Wang, the disclosure of which is incorporated by reference.
In another embodiment, the balloon material is formed from polyamides. Preferably, the polyamide has substantial tensile strength, be resistant to pin-holing even after folding and unfolding, and be generally scratch resistant, such as those disclosed in U.S. Pat. No. 6,500,148 to Pinchuk, the disclosure of which is incorporated herein by reference. Some non-limiting examples of polyamide materials suitable for the balloon include nylon 12, nylon 11, nylon 9, nylon 69 and nylon 66. Preferably, the polyamide is nylon 12.
In another embodiment, the balloon may be formed a polyurethane material, such as TECOTHANE® (Thermedics). TECOTHANE® is a thermoplastic, aromatic, polyether polyurethane synthesized from methylene disocyanate (MDI), polytetramethylene ether glycol (PTMEG) and 1,4 butanediol chain extender. TECOTHANE® grade 1065D is presently preferred, and has a Shore durometer of 65D, an elongation at break of about 300%, and a high tensile strength at yield of about 10,000 psi. However, other suitable grades may be used, including TECOTHANE® 1075D, having a Shore D of 75. Other suitable compliant polymeric materials include ENGAGE® (DuPont Dow Elastomers (an ethylene alpha-olefin polymer) and EXACT® (Exxon Chemical), both of which are thermoplastic polymers. Other suitable compliant materials include, but are not limited to, elastomeric silicones, latexes, and urethanes.
The compliant material may be cross linked or uncrosslinked, depending upon the balloon material and characteristics required for a particular application. The presently preferred polyurethane balloon materials are not crosslinked. However, other suitable materials, such as the polyolefinic polymers ENGAGE® and EXACT®, are preferably crosslinked. By crosslinking the balloon compliant material, the final inflated balloon size can be controlled. Conventional crosslinking techniques can be used including thermal treatment and E-beam exposure. After crosslinking, initial pressurization, expansion, and preshrinking, the balloon will thereafter expand in a controlled manner to a reproducible diameter in response to a given inflation pressure, and thereby avoid overexpanding the stent (when used in a stent delivery system) to an undesirably large diameter.
In one embodiment, the balloon is formed from a low tensile set polymer such as a silicone-polyurethane copolymer. Preferably, the silicone-polyurethane is an ether urethane and more specifically an aliphatic ether urethane such as PURSIL AL 575A and PURSIL AL10, (Polymer Technology Group), and ELAST-EON 3-70A, (Elastomedics), which are silicone polyether urethane copolymers, and more specifically, aliphatic ether urethane cosiloxanes. In an alternative embodiment, the low tensile set polymer is a diene polymer. A variety of suitable diene polymers can be used such as but not limited to an isoprene such as an AB and ABA poly(styrene-block-isoprene), a neoprene, an AB and ABA poly(styrene-block-butadiene) such as styrene butadiene styrene (SBS) and styrene butadiene rubber (SBR), and 1,4-polybutadiene. Preferably, the diene polymer is an isoprene including isoprene copolymers and isoprene block copolymers such as poly(styrene-block-isoprene). A presently preferred isoprene is a styrene-isoprene-styrene block copolymer, such as Kraton 1161K available from Kraton, Inc. However, a variety of suitable isoprenes can be used including HT 200 available from Apex Medical, Kraton R 310 available from Kraton, and isoprene (i.e., 2-methyl-1,3-butadiene) available from Dupont Elastomers. Neoprene grades useful in the invention include HT 501 available from Apex Medical, and neoprene (i.e., polychloroprene) available from Dupont Elastomers, including Neoprene G, W, T and A types available from Dupont Elastomers.
In accordance with another aspect of the invention, the outer surface of the balloon is modified. In this regard, the balloon surface may include a textured surface, roughened surface, voids, spines, channels, dimples, pores, or microcapsules or a combination thereof, as will be described below.
In one embodiment of the invention, the balloon is formed of a porous elastomeric material having at least one void formed in the wall of the balloon surface. For example, the entire cross section of the balloon may contain a plurality of voids. Alternatively, the plurality of void may be distributed along select portions of the balloon outer surface. For example and not limitation, the plurality of voids can be distributed only along only the working section of the balloon. The voids define an open space within the outer surface of the balloon. Preferably, the therapeutic agent is dispersed within the space defined by the plurality of voids across the cross section of the balloon outer surface.
In operation, the therapeutic agent is released or is expelled from the pores upon inflation of the balloon. In this regard, the durometer of the polymeric material of the balloon surface and in particular the depression of the void is sufficiently flexible to allow for expulsion of the therapeutic agent and/or coating contained within the plurality of voids upon inflation of the balloon. The expelled coating with therapeutic agent is released into the vessel lumen or into the tissue surrounding and contacting the inflated balloon.
In another embodiment, the balloon includes protrusions configured to contact or penetrate the arterial wall of a vessel upon inflation of the balloon. A coating containing therapeutic agent is disposed on the protrusions and when inflated the coating and/or therapeutic agent coats the tissue of the arterial wall. Alternatively, the balloon may include two concentric balloons in a nesting configuration. The coating with therapeutic agent is disposed between the two concentric balloons. Thus, the space between the two concentric balloons; one being an interior balloon and the other being an exterior balloon, acts as a reservoir. In this regard, the protrusions may include apertures for expulsion of the coating and/or therapeutic agent upon inflation of the interior and exterior concentric balloons. For example, as described in U.S. Pat. No. 6,991,617 to Hektner, the disclosure of which is incorporated herein by reference thereto. In another embodiment, the balloon may include longitudinal protrusions configured to form ridges on the balloon surface. As described in U.S. Pat. No. 7,273,417 to Wang, the entire disclosure of which is incorporated herein by reference, the ridges can be formed of filaments spaced equidistantly apart around the circumference of the balloon. However, a larger or smaller number of ridges can alternatively be used. The longitudinal ridges can be fully or partially enveloped by the polymeric material of the balloon.
In yet another embodiment of the invention, the balloon may include microcapsules on its outer surface. In this regard, the microcapsules are configured to encompass the coating and/or therapeutic agent. Upon inflation of the balloon the microcapsules located on the surface of the balloon contact the tissue of the arterial wall. Alternatively, the microcapsules may be formed in the wall of the balloon surface. The coating and/or therapeutic agent may be released from the microcapsules by fracturing of the microcapsules and/or diffusion from the microcapsule into the arterial wall. The microcapsules may be fabricated in accordance with the methods disclosed in U.S. Pat. No. 5,1023,402 to Dror or U.S. Pat. No. 6,129,705 to Grantz and the patents referenced therein, each of which is incorporated herein by reference in its entirety.
In accordance with another aspect of the invention, if desired, a protective sheath may be utilized to protect the coating from being rubbed off of the balloon during the movement of the coated balloon through the body lumen. The sheath is preferably made from an elastic and resilient material which conforms to the shape of the balloon and in particular is capable of expanding upon inflation of the balloon. The sheath preferably includes apertures along a portion thereof. In operation, the inflation of the balloon causes the apertures of the sheath to widen for release of the coating and/or therapeutic agent to the tissue of the arterial wall. Preferably, the sheath has a thickness less than 10 mils. However, other thicknesses are possible.
In another embodiment, the sheath has at least one longitudinal line of weakness allowing the sheath to rupture upon inflation of the balloon and the release of the coating and/or therapeutic agent onto the tissue of the arterial wall of the vessel. Preferably, the sheath is formed from polymeric material known to be suitable for use in balloon catheters. Preferably, the sheath material is an elastomeric material which will also spring back when it splits to expose more of the body lumen to the coating. The line of weakness could be provided by various techniques known in the art. However, one non-limiting examples include perforating the sheath material. In operation, the sheath is placed over the coated balloon while in the deflated state. When the coated balloon inflated, the sheath is expanded to the extent that it exceeds its elastic limit at the line of weakness and bursts to expose and therefore release the coating and/or therapeutic agent to the tissue of the arterial wall or vessel lumen. For example, see U.S. Pat. No. 5,370,614 to Amundson, the entire disclosure of which is incorporated by reference.
The present application is further described by means of the examples, presented below. The use of such examples is illustrative only and in no way limits the scope and meaning of the invention or of any exemplified term.
Zotarolimus was coated onto deflated 17×3.0 mm angioplasty balloons by syringing a solution of the drug dissolved in a mixture of Ultravist contrast agent, acetone, and ethanol onto the balloon surface. The average amount of zotarolimus coated was 662 μg per balloon. Balloon expansion was performed at 20% overstretch in porcine coronary arteries. The balloons were maintained expanded in position for 1 minute. Animals were sacrificed after 20 minutes, and the concentration of zotarolimus in the arterial tissue at the expansion sites was measured. The mean dose delivered was 6% of the total, which corresponded to a local concentration of 800 μM, at this early time point.
Everolimus was coated onto inflated 3.0 mm×21 mm diameter Pebax angioplasty balloons using a custom designed Sonotek ultrasonic balloon coater. Three coating formulations were evaluated including 1) everolimus alone (1025 μg/balloon); 2) everolimus with hydrophilic Ultravist contrast agent at a 1:1 (w/w) ratio; and 3) everolimus with hydrophilic non-ionic polyvinylpyrrolidone polymer (Povidone C-30) and glycerol plasticizer at a 1:1:0.4 (w/w) ratio. The dosage of therapeutic agent coated on the balloons are 1) everolimus alone (1600 μg/balloon); 2) everolimus with hydrophilic Ultravist contrast agent at a 1:1 (w/w) ratio (1250 μg/balloon); and 3) everolimus with hydrophilic non-ionic polyvinylpyrrolidone polymer (Povidone C-30) at a 1:1 (w/w) ratio (1025 μg/balloon).
The coatings were sprayed and baked dry followed by balloon folding, 3.0 mm×18 mm Vision stent crimping, sheath placement, heat bonding to a full length catheter and hypotube seal, packaging, and ethylene oxide sterilization. Stents were delivered to either porcine LAD, LCX, or RCA coronary arteries with 30 seconds inflation times and 20% overstretch as measured by angiography. At 24 hours and 72 hours after delivery, animals were sacrificed and the artery regions from proximal, stented, distal#1, and distal#2 (15 mm away from stented region) were explanted and submitted for everolimus content measurement by HPLC or LC/MS (liquid chromatography/mass spectrometry) after tissue homogenization and extraction. The tissues were briefly homogenized in a dilution solution. After centrifugation, an aliquot of supernatant was injected onto the LC/MS column. A mobile phase gradient containing formic acid and ammonium acetate was used to elute everolimus. The everolimus concentration in tissue was then determined by the total amount in dilution solution divided by tissue weight. The limit of quantification of the method is 0.5 ng/mL. For blood, an internal standard (IS)/precipitation solution was added into a whole blood sample. After vortexing and centrifugation, supernatant from the mixture was analyzed by a HPLC column.
Tissue concentrations from the stented artery region are illustrated in
a illustrates tissue concentration of everoliumus at 24 hours and
In the following experiments, zotarolimus formulations were coated onto inflated 3.0 mm×12 mm Vision RX angioplasty balloons by air assisted spray atomization (zotarolimus only coatings at 88 ug/cm2 or 570 ug/cm2) or direct fluid volume application (zotarolimus:excipient coatings) of a solution of the drug dissolved neat in solvent or in a mixture of drug and excipient. The excipient formulations evaluated were zotarolimus-Ultravist 1.95-1 and zotarolimus-PVP-glycerol 2-1-0.4 with and without a bare metal stent and at either 88 ug/cm2 or 15 ug/cm2 zotarolimus dosages. Balloon expansion was performed at 20% overstretch in healthy domestic porcine coronary and/or mammary arteries. The balloons were maintained expanded in position for 30 seconds. Following balloon angioplasty, the animals were sacrificed after 30 minutes, 1 day (zotarolimus only), and 7 days and the concentration of zotarolimus in the arterial tissue at the expansion sites was measured via HPLC/LC-MS after tissue homogenization and extraction.
Treated region of interest tissue concentrations from the zotarolimus only coating porcine pK study are shown in
As illustrated in
Treated region of interest tissue concentrations at 30 minutes and 7 days post delivery from the zotarolimus:excipient coatings porcine PK study are shown in
In
Blood zotarolimus concentrations increased as a function of time with Tmax ranging from 1-3 hours and Cmax from 2.1-39.4 ng/mL as a function of coating formulation as illustrated in
