Drug Therapy Delivery Systems and Methods

Abstract

Ophthalmic drug delivery devices are disclosed. In various embodiments, the ophthalmic drug delivery devices include multiple microporous layers arranged together to form a microporous body configured to meter the distribution of the drug to surrounding tissue. In some embodiments, the ophthalmic drug delivery devices include one or more portions configured to resist tissue ingrowth and one or more portions configured to permit tissue ingrowth. In some embodiments, the ophthalmic drug delivery devices deliver one or more drugs useful for the treatment of glaucoma.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of Provisional Application No. 62 / 724,425, filed August 29, 2018, which is incorporated herein by reference in its entirety for all purposes. [Background technology]

[0002] background Aqueous humor is the fluid that fills the anterior chamber of the eye and contributes to intraocular pressure, or fluid pressure within the eye. Ocular hypertension is an eye condition in which the intraocular pressure, or fluid pressure within the eye, is elevated. Untreated ocular hypertension can lead to diseases, including glaucoma, which can result in gradual, sometimes permanent, loss of vision in the affected eye.

[0003] Many attempts have been made to treat ocular hypertension, particularly glaucoma. These attempts include surgical procedures, including the implantation of drainage devices designed to reduce intraocular pressure in the affected eye, as well as medications. The goal of these treatments is to improve quality of life and preserve visual function by reducing intraocular pressure.

[0004] Drug administration is typically in the form of eye drops that must be self-administered by the patient, although implantable long-term drug delivery devices may be used in certain cases. Implantable long-term drug delivery devices typically reside outside the eye (e.g., extraocular approach) or are implanted within the anterior chamber of the eye (intracameral approach).

[0005] Extraocular approaches to drug delivery present various challenges. To be effective, they require the transport of sufficient amounts of drug through the conjunctival layer of the eye into the anterior chamber via biological processes in the eye. Obvious natural mechanisms, such as the continuous flushing mechanism of the human tear film, as well as the natural barrier to the interior of the eye formed by the conjunctiva, complicate the effectiveness of extraocular approaches, resulting in suboptimal dose delivery over time. Therefore, extraocular approaches sometimes involve administering excessive amounts of drug to extend the effective period.

[0006] On the other hand, the intracameral approach is a more invasive approach that requires puncture through various tissue layers of the eye to gain access and placement of the device within the anterior chamber of the eye. The intracameral approach is further complicated when the drug is administered in conjunction with an absorbable (bioabsorbable) device because the degradability of the device can lead to the device becoming dislodged and floating within the anterior chamber. Furthermore, removal and replacement of the device requires trauma to the ocular tissue. Summary of the Invention

[0007] Abstract According to one example ("Example 1"), an implantable delivery device for distributing a drug includes a first microporous layer including a plurality of pores sized to permit tissue ingrowth, a second microporous layer including a plurality of pores sized to permit tissue ingrowth, a third microporous layer coupled to the first microporous layer including a plurality of pores sized to resist tissue ingrowth, and a reservoir for receiving a drug defined between the third microporous layer and the second microporous layer, the third microporous layer configured to meter the rate at which the drug is eluted from the reservoir when the delivery device is implanted.

[0008] According to another example ("Example 2"), in addition to Example 1, the implantable delivery device further includes a fourth microporous layer bonded to the second microporous layer such that the reservoir is defined between the third microporous layer and the fourth microporous layer.

[0009] According to another example ("Example 3"), in addition to Example 2, the fourth microporous layer comprises a plurality of pores sized to resist tissue ingrowth, and the fourth microporous layer is permeable to the drug.

[0010] According to another example ("Example 4"), in addition to Example 2, the fourth microporous layer is impermeable to the drug.

[0011] According to another example ("Example 5"), in addition to Example 4, the fourth layer includes an elastomer.

[0012] According to another example ("Example 6"), further to any of the above examples, the first microporous layer includes an aperture configured to expose the third microporous layer.

[0013] According to another example ("Example 7"), in addition to any of the above examples, the implantable delivery system includes one or more structural spacers disposed within the reservoir to maintain separation between the second microporous layer and the third microporous layer.

[0014] According to another example ("Example 8"), in addition to any of the examples above, the reservoir is configured to be refilled and emptied in situ.

[0015] According to another example ("Example 9"), further to any of the above examples, the reservoir is configured to expand to accommodate the agent therein.

[0016] According to another example ("Example 10"), in addition to any of the examples above, at least one of the first microporous layer and the second microporous layer comprises an expanded polytetrafluoroethylene (ePTFE) membrane.

[0017] According to another example ("Example 11"), in addition to any of the above examples, a first portion of the third microporous layer is impermeable to the drug and a second portion of the third microporous layer is permeable to the drug.

[0018] According to another example ("Example 12"), in addition to any of the examples above, the first portion of the third microporous layer includes an elastomer.

[0019] According to another example ("Example 13"), further to any of the examples above, the delivery device is implantable intraocularly.

[0020] According to another example ("Example 14"), in addition to Example 13, the medicament is an ophthalmic medicament for treating glaucoma.

[0021] According to another example ("Example 15"), an implantable delivery device for dispensing a drug includes a first microporous layer bonded to a second microporous layer to define a reservoir including a first inner surface and an opposing second inner surface, and a body having an outer surface, the first inner surface being separable from the second inner surface when the reservoir is filled with drug, the first inner surface being configured to meter the dispensing of drug over a predetermined period of time, the first inner surface being configured to resist tissue ingrowth, and the outer surface of the body being configured to permit tissue ingrowth.

[0022] According to another example ("Example 16"), in addition to Example 15, at least a portion of the first interior surface is permeable to the drug.

[0023] According to another example ("Example 17"), in addition to Examples 15-16, the second inner surface is impermeable to the drug.

[0024] According to another example ("Example 18"), in addition to Example 17, the second inner surface includes an elastomer.

[0025] According to another example ("Example 19"), further to examples 15-18, the reservoir is configured to be refilled and emptied in situ.

[0026] According to another example ("Example 20"), further to examples 15-19, the reservoir is configured to expand to accommodate the agent therein.

[0027] According to another example ("Example 21"), in addition to Examples 15-20, at least one of the first microporous layer and the second microporous layer comprises an expanded polytetrafluoroethylene (ePTFE) membrane.

[0028] According to another example ("Example 22"), further to examples 15-21, a first portion of the first inner surface is impermeable to the drug, and a second portion of the first inner surface is permeable to the drug.

[0029] According to another example ("Example 23"), in addition to Example 22, the first portion of the first inner layer includes an elastomer.

[0030] According to another example ("Example 24"), further to Examples 15-23, the delivery device is implantable intraocularly.

[0031] According to another example ("Example 25"), in addition to Examples 15 to 24, the medicament is an ophthalmic medicament for treating glaucoma.

[0032] According to another example ("Example 26"), a delivery device for distributing a drug comprises a microporous body including a first microporous layer, a second microporous layer, and a third microporous layer, wherein the first microporous layer is positioned between the second microporous layer and the third microporous layer, and the first microporous layer includes a plurality of pores sized to resist tissue ingrowth, and wherein the second microporous layer and the third microporous layer each include a plurality of pores sized to permit tissue ingrowth, and a drug reservoir disposed between the first microporous layer and the third microporous layer.

[0033] According to another example ("Example 27"), in addition to Example 26, the first microporous layer includes a metering portion for dispensing a drug over a period of time.

[0034] According to another example ("Example 28"), further to Examples 26-27, the second microporous layer and the third microporous layer define an exterior of the delivery device.

[0035] According to another example ("Example 29"), in addition to Examples 26-28, the first microporous layer is bonded to the second microporous layer.

[0036] According to another example ("Example 30"), further to example 29, the second microporous layer includes an aperture configured to expose the first microporous layer.

[0037] According to another example ("Example 31"), further to examples 26-30, the drug reservoir is configured to be refilled and emptied in situ.

[0038] According to another example ("Example 32"), further to examples 26-31, the drug reservoir is configured to expand to accommodate the drug therein.

[0039] According to another example ("Example 33"), in addition to Examples 26 to 32, at least one of the first microporous layer, the second microporous layer, and the third microporous layer comprises an expanded polytetrafluoroethylene (ePTFE) membrane.

[0040] According to another example ("Example 34"), in addition to Examples 26 to 33, the first microporous layer includes a first portion that is permeable to the drug and a second portion that is impermeable to the drug, and the second portion of the first microporous layer includes an elastomer.

[0041] According to another example ("Example 35"), further to Examples 26-34, the delivery device is implantable intraocularly.

[0042] According to another example ("Example 36"), in addition to Examples 27 to 35, the medicament is an ophthalmic medicament for treating glaucoma.

[0043] According to another example ("Example 37"), a drug metering device having an exterior surrounding an interior defining a drug reservoir, the device including: a first layer including a first microporous layer and a second microporous layer, wherein the first microporous layer is configured to resist tissue ingrowth and the second microporous layer is configured to allow tissue ingrowth, the first microporous layer defining a portion of the interior and the second microporous layer defining a portion of the exterior; and a second layer bonded to the first layer such that the drug reservoir is defined between the first and second layers, wherein a portion of the first microporous layer of the first layer is permeable to a drug disposable within the drug reservoir.

[0044] According to another example ("Example 38"), in addition to Example 37, the drug reservoir is defined between portions of the first layer and the second layer that are not bonded to each other so that the unbonded portions of the first layer and the second layer are free to flex relative to each other.

[0045] According to another example ("Example 39"), further to Examples 37-38, the second layer includes a third microporous layer and a fourth microporous layer, the third microporous layer of the second layer configured to resist tissue ingrowth and the fourth microporous layer of the second layer configured to permit tissue ingrowth, the third microporous layer of the second layer defining a portion of the interior, and the fourth microporous layer defining a portion of the exterior.

[0046] According to another example ("Example 40"), in addition to Examples 37 to 39, the first microporous layer and the second microporous layer of the first layer comprise expanded polytetrafluoroethylene (ePTFE).

[0047] According to another example ("Example 41"), further to Examples 37-40, the first microporous layer of the first layer includes a plurality of pores sized to resist tissue ingrowth, and the second microporous layer of the first layer includes a plurality of pores sized to permit tissue ingrowth.

[0048] According to another example ("Example 42"), further to Examples 39-41, the third microporous layer of the second layer comprises a plurality of pores sized to resist tissue ingrowth, and the fourth microporous layer of the second layer comprises a plurality of pores sized to permit tissue ingrowth.

[0049] According to another example ("Example 43"), in addition to Examples 39-42, the third microporous layer of the second layer comprises an elastomer such that the third microporous layer of the second layer is impermeable to a drug.

[0050] According to another example ("Example 44"), in addition to Examples 37 to 43, the first microporous layer of the first layer comprises a first portion that is permeable to a drug and a second portion that is impermeable to a drug, and the second portion of the first microporous layer of the first layer comprises an elastomer.

[0051] According to another example ("Example 45"), further to Examples 37-44, the delivery device is implantable intraocularly.

[0052] According to another example ("Example 46"), in addition to Example 45, the medicament is an ophthalmic medicament for treating glaucoma.

[0053] According to another example ("Example 47"), in addition to any of the above examples, the agent is contained within a fluid suspension of particles.

[0054] According to another example ("Example 48"), further to Example 47, the first microporous layer of the first layer includes a plurality of pores sized to prevent particles from passing through the first microporous layer. [Brief explanation of the drawings]

[0055] BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings are included to provide a further understanding of embodiments of the present disclosure, and are incorporated into and constitute a part of this specification, illustrating examples and, together with the description, serving to explain the principles of the present disclosure.

[0056] [Figure 1A] FIG. 1A is a diagram of a drug delivery system implanted in the eye, according to some embodiments.

[0057] [Figure 1B] FIG. 1B is a detailed view of FIG. 1A showing a drug delivery system implanted in the eye, according to some embodiments.

[0058] [Figure 2] FIG. 2 is a cross-sectional view of the drug delivery system shown in FIG. 4 in an expanded state taken along line 2-2, according to some embodiments.

[0059] [Figure 3] FIG. 3 is a cross-sectional view of the drug delivery system shown in FIG. 4 in a contracted state taken along line 2-2, according to some embodiments.

[0060] [Figure 4] FIG. 4 is a front view of a drug delivery system according to some embodiments.

[0061] [Figure 5] FIG. 5 is a cross-sectional view of a drug delivery system according to some embodiments.

[0062] [Figure 6] FIG. 6 is a cross-sectional view of a drug delivery system according to some embodiments.

[0063] [Figure 7] FIG. 7 is a cross-sectional view of the drug delivery system shown in FIG. 6 taken along line 7-7, according to some embodiments.

[0064] [Figure 8] FIG. 8 is a cross-sectional view of a drug delivery system according to some embodiments.

[0065] [Figure 9] FIG. 9 is a cross-sectional view of the drug delivery system shown in FIG. 8 taken along line 9-9, according to some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0066] Detailed Description Those skilled in the art will readily appreciate that the various embodiments of the inventive concepts provided in this disclosure may be implemented by any number of methods and apparatuses configured to perform their intended functions. It should also be noted that the accompanying drawings referred to herein are not necessarily drawn to scale and may be exaggerated to illustrate various aspects of the present disclosure, and in that regard, the drawings should not be construed as limiting.

[0067] The present disclosure relates to systems, devices, and methods for delivering a drug to a patient's eye. In various embodiments, the drug is an ophthalmic drug configured to treat ocular hypertension and / or glaucoma, for example, by lowering intraocular pressure from undesirably high levels that can cause gradual, sometimes permanent, loss of vision in the affected eye. In various embodiments, a drug delivery system according to the present disclosure can be configured to measure the drug release rate of one or more different drugs and thus provide multiple different release rates, including multiple different release rates of multiple drugs. Some examples of suitable ophthalmic drugs include therapeutic agents such as prostaglandin analogs (PGAs) (e.g., latanoprost) or other drug classes, including beta-blockers such as timolol, alpha-2 agonists such as brimonidine tartrate, or carbonic anhydrase inhibitors such as dorzolamide, carbonic anhydrase inhibitor and beta-blocker compounds, and alpha-agonist and beta-blocker compounds, which can be administered in combination with PGAs.

[0068] In some embodiments, such drug delivery systems are configured to be implanted and minimally invasively refillable in situ one or more times without requiring removal of the drug delivery system from the implantation site. Given the size and target implant location under the conjunctiva, the implantation procedure can be performed outside of an operating room where needle punctures and small incisions are typically performed. Furthermore, some example systems include features to help reduce micromotion between the drug delivery system and the tissue into which it is implanted. Micromotion is known to sometimes cause irritation of surrounding tissue, which can lead to a foreign body tissue reaction, excessive scarring, eventual erosion of the implanted device, and / or site infection.

[0069] A drug delivery system 1000 according to some embodiments is shown in FIG. 1A. As shown, the drug delivery system 1000 is implanted within the eye 5000 between the conjunctiva 5002 and the sclera 5004 of the eye 5000. The anterior chamber 5006 is also shown. The drug delivery system 1000 generally includes one or more portions configured to meter drug release from the drug delivery system 1000 and one or more portions configured to promote or allow cell infiltration and / or tissue adhesion. The drug can include a single therapeutic agent (e.g., a drug) or can include multiple therapeutic agents. The drug delivery system 1000 can be configured to measure drug release rates of multiple different drugs at multiple different release rates.

[0070] FIG. 1B is a detailed view of region 1B of FIG. 1A, showing the drug delivery system 1000 implanted within the subconjunctival space 5008. As shown, the subconjunctival space 5008 is a pocket formed between the conjunctiva 5002 and the sclera 5004 of the eye 5000. The subconjunctival space 5008 shown in FIGS. 1A and 1B can be formed according to known methods. In some embodiments, the drug delivery system 1000 can be implanted externally (e.g., from outside the eye), such as through a conjunctival incision. In some embodiments, a radial conjunctival incision is made near the limbal junction, and blunt dissection of the conjunctiva is performed to expose the sclera and form a subconjunctival pocket for placement of the drug delivery system 1000. In other embodiments, the drug delivery system 1000 is implanted internally (e.g., from inside the eye), such as through a clear corneal incision, and placed through the sclera 5004 into the incised subconjunctival space 5008.

[0071] In some embodiments, the drug delivery system 1000 can be further secured to the sclera 5004 or other surrounding tissue by suturing, adhesives, etc., or according to other known methods. While the drug delivery system 1000 can be permanently or semi-permanently secured at the time of the implantation procedure, the drug delivery system 1000 can also be initially temporarily secured (or initially not secured at all) and subsequently secured to the sclera 5004 or other surrounding tissue by one or more portions of the drug delivery system 1000 configured to promote or allow cell infiltration and tissue attachment.

[0072] 1A and 1B, drug delivery system 1000 includes at least a first layer 1100 and a second layer 1200. First layer 1100 and second layer 1200 are generally coupled together to provide a drug reservoir 1300 defined between first layer 1100 and second layer 1200, as shown in FIG. 1B. Drug reservoir 1300 is generally an enclosed space in which a drug can be deposited for subsequent delivery by drug delivery system 1000. Generally, drug delivery system 1000 is configured to measure the release rate of a drug disposed in drug reservoir 1300 over a specified period of time. For example, a drug can be disposed or deposited in drug reservoir 1300, and drug delivery system 1000 can be configured to release the drug according to a predetermined treatment regimen for treating one or more ocular defects or conditions.

[0073] Additionally, the drug delivery system 1000 may be refillable and / or emptied in situ (e.g., without first having to remove the drug delivery system 1000 from the implantation site) in a minimally invasive manner. In some such embodiments, one or more of the first and second layers 1100 and 1200 are configured to be repeatedly pierced with a cannula during drug reservoir refill or emptying operations without significantly compromising the integrity of the first and / or second layers 1100. In some embodiments, this integrity may be achieved by coating or imbibing the first and / or second layers 1100 and 1200 with an elastomeric material.

[0074] Referring now to Figures 2-4, a drug delivery system 1000 is shown. Figure 2 is a cross-sectional view of the drug delivery system 1000 shown in an expanded state (i.e., the drug reservoir 1300 is expanded such that a separation is defined between the first and second layers 1100 and 1200) taken along line 2-2 of the drug delivery system shown in Figure 4. In some embodiments, the expanded state corresponds to the presence of a drug in the drug reservoir 1300. Figure 3 is a cross-sectional view of the drug delivery system 1000 taken along line 2-2 of the drug delivery system shown in Figure 4 shown in a deflated state, such as when the drug reservoir 1300 is empty or lacks a sufficient amount of drug to cause a separation between the first and second layers 1100 and 1200. Figure 4 is a front view of the drug delivery system 1000.

[0075] 2 , the first and second layers 1100 and 1200 are bonded together along one or more portions of the first and second layers 1100 and 1200, while one or more other portions of the first and second layers 1100 and 1200 remain unbonded. The unbonded portions of the first and second layers 1100 and 1200 remain freely separated from one another. In various embodiments, the unbonded portions of the first and second layers 1100 and 1200 are operable to separate from one another to define a drug reservoir 1300.

[0076] In some embodiments, the first and second layers 1100 and 1200 may be bonded together around the peripheral edge 1002 of the drug delivery system 1000, as shown in FIG. 2 . However, it should be understood that the first and second layers 1100 and 1200 may additionally or alternatively be bonded in other areas, including one or more areas within the peripheral edge 1002. The peripheral edge 1002 is generally a rim extending around the periphery of the drug delivery system 1000. The peripheral edge 1002 can be uniform, non-uniform, continuous, or discontinuous. For example, in some embodiments, the peripheral edge 1002 may include one or more radially extending tabs or petals (e.g., the drug delivery system 1000 may include a scalloped peripheral edge). In some embodiments, these tabs or petals may act as bonding areas for bonding the drug delivery system 1000 to surrounding tissue, such as the sclera 5004.

[0077] As shown in FIG. 2 , the first and second layers 1100 and 1200 are bonded together at the peripheral edge 1002 and / or along a region just radially inward of the peripheral edge 1002 to form a bonded region extending adjacent the peripheral edge 1002. The bonded region is annular in shape and can extend radially inward from the peripheral edge 1002 as desired. As shown in FIG. 2 , the drug reservoir 1300 is defined between the first and second layers 1100 and 1200, where the first and second layers 1100 and 1200 remain unbonded. It will be understood that the first and second layers 1100 and 1200 can be further bonded together at multiple distinct locations or regions, including one or more locations or regions radially inward of the peripheral edge 1002 of the drug delivery system 1000. Bonding one or more additional regions inside the peripheral edge can help control the expansion profile of the drug delivery system 1000.

[0078] One or more of the first and second layers 1100 and 1200 can be configured to deform elastically or plastically when the drug reservoir 1300 is expanded. Additionally, in some embodiments, one of the first and second layers 1100 and 1200 can be inelastic, which can help control the expansion profile of the drug delivery system 1000.

[0079] In various embodiments, one or both of the first and second layers 1100 and 1200 include one or more regions configured to meter the release of the agent. These metering regions can be in the form of membranes, layers, or films, or coatings. In some embodiments, one or more of the first and second layers 1100 and 1200 include one or more regions configured to allow or promote cell infiltration or tissue ingrowth and attachment. Cell infiltration and tissue attachment generally occur when a material is sufficiently porous to allow fibroblast infiltration. Thus, the drug delivery system 1000 can include membranes, layers, films, and / or coatings configured to allow tissue ingrowth and attachment.

[0080] In at least one embodiment, the first layer and / or the second layer 1100 and 1200 can be formed from multiple membrane layers. For example, as shown in Figures 2 and 3, the first layer 1100 can include a first membrane layer 1110 and a second membrane layer 1120. The first membrane layer and the second membrane layers 1110 and 1120 of the first layer 1100 collectively define the first layer 1100. The layer 1100 can include membrane layers in addition to the first membrane layer and the second membrane layers 1110 and 1120.

[0081] In some embodiments, one or more of the first and second membrane layers 1110 and 1120 can include a microporous microstructure. For example, one or more of the first and second membrane layers 1110 and 1120 can include a biocompatible material such as expanded polytetrafluoroethylene (ePTFE). Additionally, one or more of the first and second membrane layers 1110 and 1120 of the first layer 1100 can be formed from other biocompatible materials, including biocompatible polymers that may or may not be microporous, including, but not limited to, polyurethane, silicone, polysulfone, polyvinylidene fluoride (PVDF), polyhexafluoropropylene (PHFP), perfluoroalkoxy polymers (PFA), polyolefins, fluorinated ethylene propylene (FEP), acrylic copolymers, and polytetrafluoroethylene (PTFE).

[0082] The first and / or second membrane layers can be in the form of one or more sheets or films, including knit, woven, and / or nonwoven fabrics containing individual or multi-filament strands. In some embodiments, the first and / or second membrane layers 1110 and 1120 can be formed from multiple sheets or films of polymeric material. In some embodiments, the sheets or films can be laminated or otherwise mechanically bonded to form the first and / or second membrane layers 1110 and 1120 of the first layer 1100. Bonding of the sheets or films can be achieved by various mechanisms, including heat treatment, high pressure compression, one or more bonding agents such as adhesives, lamination, or other suitable methods known to those skilled in the art.

[0083] In some embodiments, adjacently disposed membrane layers (e.g., first and second membrane layers 1110 and 1120) and / or layers of material forming such membrane layers can be partially or fully bonded via thermal methods, in which the respective polymers forming the materials are brought above their melting temperatures. In some embodiments, such thermal processes promote the formation of adhesive or cohesive bonds between the materials or layers of materials. In some embodiments, adjacently disposed membrane layers and / or layers of material forming such membrane layers can be partially or fully bonded via thermal methods, in which at least one of the materials is brought above its melting temperature. Such thermal processes can promote the formation of adhesive or cohesive bonds between the materials or layers of materials. In some embodiments, one or more suitable adhesives are utilized to provide a well-bonded interface. Adjacently disposed membrane layers and / or layers of material forming such membrane layers can be bonded together at one or more distinct locations to form a stabilized structure extending through the resulting structure.

[0084] In some embodiments, the first layer 1100 and / or the first and second membrane layers 1110 and 1120, and / or the sheet or film from which the first and second membrane layers 1110 and 1120 are formed, can be subjected to one or more processes to modify their microstructure. In some embodiments, such processes include, but are not limited to, a material coating process, a surface preconditioning process, and / or a perforation process. A material coating process can be used to apply one or more drug or antimicrobial coatings to the polymeric material (such as metal salts (e.g., silver carbonate) and organic compounds (e.g., chlorhexidine diacetate)). Hydrophilic coatings to enable wetting, including immediate wetting of the polymer matrix, can also be applied when the polymer surface is generally hydrophobic. A surface coating containing an antimicrobial component can additionally or alternatively be applied to reduce the body's naturally occurring inflammatory response during post-surgical wound healing. The material surface can additionally or alternatively be modified with antiproliferative compounds (eg, mitomycin C, 5-fluoracil) to mitigate surrounding tissue reaction.

[0085] In some embodiments, one or more surface preconditioning processes can be utilized to create layers exhibiting exemplary microstructures (e.g., wrinkles, folds, or other geometric out-of-plane structures), as described in U.S. Patent No. 9,849,629 to Zaggl. Such surface preconditioning can promote a more aggressive initial inflammatory phase after surgery and provide an initial, stable interface between the porous device and tissue. In some embodiments, a heparin coating can additionally or alternatively be applied to help minimize cell formation, including fibrinogen accumulation, after a surgical implant procedure.

[0086] In some embodiments, one or more perforation processes can be utilized to form multiple perforations or pores in one or more of the first and second membrane layers 1110 and 1120 of the first layer 1100 to achieve a desired porosity, i.e., in addition to relying on any interstices, pores (voids between the fibrils and nodes that make up the microstructure), and / or channels that occur naturally within the polymer material.

[0087] It is understood that the first and second membrane layers 1110 and 1120 of the first layer 1100 may be treated in different ways to achieve membrane layers with different material properties, such as different porosities and / or different cell infiltration potentials, etc. In some embodiments, the first and second membrane layers 1110 and 1120 of the first layer may not be subjected to any treatment steps.

[0088] In some embodiments, the first membrane layer 1110 (also referred to herein as a drug-metering membrane layer) is configured to meter the rate at which a drug passes through the first membrane layer 1110, and thus the rate at which the drug is released by the drug delivery system 1000. In various embodiments, the first membrane layer 1110 is also configured to resist cell infiltration and adhesion. In some embodiments, the first membrane layer 1110 includes gaps, perforations, pores, channels, or combinations thereof, sized and shaped to resist, impede, or otherwise minimize cell infiltration while remaining permeable to one or more drugs. The gaps, perforations, pores, or channels in the first membrane layer 1110 of the first layer 1100 can be smaller (or have an average size smaller than), for example, about 1 to about 2 microns, although various dimensions can be selected depending on the application. By being resistant to cellular ingrowth and attachment, the first membrane layer 1110 of the first layer 1100 operates to maintain separation between the drug disposed within the drug reservoir 1300 and the tissue surrounding the drug delivery system 1000. This separation operates to maintain a controlled and steady rate at which the drug is released by the drug delivery system 1000.

[0089] The second membrane layer 1120 (also referred to herein as an ingrowth membrane layer) is configured to promote or allow cell infiltration and attachment. Accordingly, the second membrane layer 1120 generally includes gaps, perforations, pores, channels, or combinations thereof, sized and shaped to promote or allow cell infiltration. Accordingly, the second membrane layer 1120 generally includes gaps, perforations, pores, channels, or combinations thereof having an average size that exceeds the average size of the gaps, perforations, pores, or channels of the first membrane layer 1110 of the first layer 1100. In some embodiments, the second membrane layer 1120 can include gaps, perforations, pores, or channels ranging in size (or average size) from 20 microns to 100 microns, although various dimensions are contemplated. For example, in other embodiments, the size (or average size) of the gaps, perforations, pores, or channels can be greater than 150 microns. Thus, the first membrane layer 1110 operates to meter and maintain a controlled and steady rate at which the drug is released by the drug delivery system 1000, while the second membrane layer 1120 helps promote biointegration of the drug delivery system 1000 by allowing cellular ingrowth and tissue attachment, which helps minimize micromotion.

[0090] In some embodiments, the interface between the first membrane layer 1100 and the second membrane layers 1110 and 1120 acts as a boundary against cellular infiltration into the first membrane layer 1110. That is, in some embodiments, the first layer 1100 is configured such that cellular infiltration and proliferation is confined to the second membrane layer 1120 and does not enter the first membrane layer 1110. Thus, in various embodiments, cellular infiltration and proliferation within the second membrane layer 1120 can generally propagate to the boundary between the first membrane layer and the second membrane layers 1110 and 1120. In some embodiments, the first layer 1100 can be configured to prevent or minimize the possibility of cellular infiltration and proliferation across the boundary between the first membrane layer 1100 and the second membrane layers 1110 and 1120.

[0091] It should also be understood that although the first layer 1100 (and the corresponding first and second membrane layers 1110 and 1120 of the first layer 1100) of the drug delivery system 1000 shown in the accompanying drawings are oval-shaped, the first and second membrane layers 1110 and 1120, and therefore the first layer 1100, can be formed from other shapes and / or sizes so long as the drug delivery system 1000 effectively achieves its intended purpose of being implantable within tissue such as a subconjunctival pocket and is operable to cause the release of a drug disposed within the drug reservoir 1300 of the drug delivery system 1000 into one or more areas of the tissue surrounding the drug delivery system 1000. For example, the first and second membrane layers 1110 and 1120, and therefore the first layer 1100, can be square, rectangular, trapezoidal, or any other polygonal or non-polygonal shape (e.g., bean-shaped), as desired, so long as the shape does not interfere with the implant procedure or prevent the drug reservoir 1300 from dispensing the drug.

[0092] 2 and 3 , the second layer 1200 of the drug delivery system 1000 includes a first membrane layer 1210 and a second membrane layer 1220. The first membrane layer 1210 of the second layer 1200 is similar to the first membrane layer 1110 of the first layer 1100 in that the first membrane layer 1210 of the second layer 1200 is configured to meter the rate at which the drug passes through the first membrane layer 1210 and, therefore, the rate at which the drug is released by the drug delivery system 1000. In various embodiments, the first membrane layer 1210 is also configured to resist cell infiltration and adhesion. Thus, the first membrane layer 1210 generally includes gaps, perforations, pores, channels, or combinations thereof consistent with those discussed above for the first membrane layer 1110 of the first layer 1100.

[0093] The second membrane layer 1220 of the second layer 1200 is similar to the second membrane layer 1120 of the first layer 1100 in that the second membrane layer 1220 of the second layer 1200 is configured to promote or allow cell infiltration and attachment. Accordingly, the second membrane layer 1220 generally includes interstices, perforations, pores, channels, or combinations thereof consistent with those discussed above for the second membrane layer 1120 of the first layer 1100. Accordingly, in various embodiments, the drug delivery system 1000 includes a second layer 1200 formed from a first membrane layer 1210 and a second membrane layer 1220, where the first membrane layer 1210 is permeable to the drug and configured to resist cell infiltration and tissue attachment, and the second membrane layer 1220 is permeable to the drug and configured to promote or allow cell infiltration and tissue attachment.

[0094] In some embodiments, the interface between the first and second membrane layers 1210 and 1220 of the second layer 1200 acts as a boundary against cellular infiltration into the first membrane layer 1210. That is, in some embodiments, the second layer 1200 is configured to restrict cellular infiltration and proliferation to the second membrane layer 1220 and prevent it from entering the first membrane layer 1210. Thus, in various embodiments, cellular infiltration and proliferation within the second membrane layer 1220 can generally propagate up to, but not through, the boundary between the first and second membrane layers 1210 and 1220. In some embodiments, the second layer 1200 can be configured to prevent or minimize the possibility of cellular infiltration and proliferation crossing the boundary between the first and second membrane layers 1210 and 1220 of the second layer 1200. It should be understood that the second layer 1200 can include membrane layers in addition to the first and second membrane layers 1210 and 1220.

[0095] Similar to the first layer 1100 described above, the second layer 1200 may be formed from shapes and / or sizes other than those shown in the accompanying figures (e.g., square, rectangular, trapezoidal, bean-shaped, or any other polygonal or non-polygonal shape), provided that the drug delivery system 1000 effectively achieves its intended purpose of being implantable within tissue and operable to release drug disposed within the drug reservoir 1300 into one or more regions of tissue surrounding the drug delivery system 1000.

[0096] 2 and 3 , the first layer 1100 is oriented such that the first membrane layer 1110 is positioned adjacent to the second layer 1200 (particularly the first membrane layer 1210 of the second layer 1200) and includes or is otherwise exposed a first surface 1102 that faces the second layer 1200 (particularly the first membrane layer 1210 of the second layer 1200). That is, in some embodiments, the first membrane layer 1100 is positioned such that the first membrane layer 1110 is positioned between the second membrane layer 1120 and the second layer 1200. Such a configuration provides that the first membrane layer 1110 of the first layer 1100 at least partially defines the drug reservoir 1300. That is, in various embodiments, the drug reservoir 1300 is at least partially defined by one or more drug-metering membrane layers (e.g., the first membrane layer 1110) configured to meter the rate at which the drug is released from the drug reservoir 1300. Such a configuration also provides that the second membrane layer 1120 of the first layer 1100 includes a second surface 1104 opposite the first surface 1102 and partially defines the exterior of the drug delivery system 1000. That is, in various embodiments, the exterior of the drug delivery system 1000 is at least partially defined by one or more tissue ingrowth membrane layers (e.g., the second membrane layer 1120), which are configured to promote or allow cell infiltration and tissue attachment, as described above. Promoting or allowing tissue ingrowth and attachment along one or more outer surfaces of the drug delivery system 1000 helps minimize micromotion between the drug delivery system 1000 and the surrounding tissue with which it interfaces.

[0097] 2 and 3, the second layer 1200 is oriented such that the first membrane layer 1210 of the second layer 1200 is located adjacent to the first layer 1100 (particularly the first membrane layer 1110 of the first layer 1100) and includes or is otherwise exposed a first surface 1202 that faces the first layer 1100 (particularly the first surface 1102 of the first membrane layer 1210 of the first layer 1100). That is, in some embodiments, the second layer 1200 is positioned such that the first membrane layer 1210 is located between the second membrane layer 1220 and the first layer 1100. Such a configuration also provides that the first membrane layer 1210 of the second layer 1200 at least partially defines the drug delivery reservoir 1300. Such a configuration also provides that the second membrane layer 1220 of the second layer 1200 includes a second surface 1204 opposite the first surface 1202 and partially defines an exterior of the drug delivery system 1000. Thus, as shown in Figures 2 and 3, the exterior of the drug delivery system 1000 is at least partially defined by the second membrane layers 1120 and 1220 of the first and second layers 1100 and 1200, respectively. Furthermore, as shown in Figures 2 and 3, the drug reservoir 1300 is partially defined by the first membrane layers 1110 and 1210 of the first and second layers 1100 and 1200, respectively. As shown, the drug reservoir 1300 is defined by portions of the first membrane layers 1110 and 1210 of the first and second layers 1100 and 1200 that remain unbonded or are otherwise not bonded to one another and are located radially inward of the portions of the first membrane layers 1110 and 1210 of the first and second layers 1100 and 1200 that are bonded together.

[0098] In various embodiments, the first and second layers 1100 and 1200 (including their various membrane layers) may be connected or bonded to one another according to known methods, such as heat treatment, high pressure compression, bonding agents such as one or more adhesives, combinations thereof, or other techniques known to those skilled in the art.

[0099] In some embodiments, the first surfaces 1102 and 1202 of the first and second layers 1100 and 1200, respectively, are bonded along the peripheral edge 1002 of the drug delivery system 1000 such that one or more portions of the first surfaces 1102 and 1202 of the first and second layers 1100 and 1200 remain unbonded to one another. In some embodiments, such unbonded areas are free to slide, translate, actuate, separate, or otherwise move relative to one another. This relative movement between the unbonded or unattached portions of the first and second layers 1100 and 1200 provides that the volume of the drug reservoir 1300 can change depending on the amount of drug present in the drug reservoir 1300. For example, the drug delivery system 1000 can be transitionable between states or configurations including a first configuration in which the drug reservoir 1300 has a first volume and a second configuration in which the drug reservoir 1300 has a second volume that is greater than the first volume.

[0100] FIG. 3 illustrates the drug delivery system 1000 in a first configuration in which the drug reservoir 1300 is deflated (e.g., devoid of or containing a negligible amount of drug), while FIG. 2 illustrates the drug delivery system 1000 in a second configuration in which the drug reservoir 1300 is inflated (e.g., completely or at least partially filled with drug). In some embodiments, the drug delivery system 1000 adopts a relatively flat profile (e.g., a relatively uniform cross-section) in the deflated state compared to the profile of the drug delivery system 1000 in the inflated state. For example, as shown in FIG. 4, the drug delivery system 1000 can adopt the shape of a blister or pillow in the inflated state. However, the drug delivery system 1000 can be configured to adopt any desired shape or size when empty and / or loaded with drug.

[0101] It is understood that the drug delivery system 1000 is configured to deliver a drug, and that the drug delivery system 1000 can be refilled or emptied on-site, such that the drug delivery system 1000 can be transitioned between a first configuration and a second configuration on-site.

[0102] Additionally, the drug reservoir 1300 can be accessed in situ via a cannula, needle, or other suitable device or method to add or remove drugs from the drug reservoir 1300 .

[0103] 2 is configured such that a drug is metered and dispensable from the drug delivery system 1000 through both the first and second layers 1100 and 1200. That is, in some embodiments, the drug delivery system 1000 includes first and second layers 1100 and 1200 that are permeable to the drug. In particular, in some embodiments, the drug is released from the drug delivery system 1000 by passing through the first membrane layers 1110 and 1210 of the first and second layers 1100 and 1200, respectively, and through the second membrane layers 1120 and 1220 of the first and second layers 1100 and 1200, respectively.

[0104] However, in other embodiments, the drug delivery system may be configured such that the drug is metered and dispensed from the drug delivery system through one or the other of the first and second layers, but not both. That is, in some embodiments, the drug delivery system may be configured such that the first of the first and second layers is permeable to the drug and the other of the first and second layers is impermeable to the drug. For example, referring now to FIG. 5, drug delivery system 2000 is shown and includes a drug-permeable first layer 2100 and a drug-impermeable second layer 2200. 5 includes a first membrane layer 2110 (similar to first membrane layer 1110) and a second membrane layer 2120 (similar to second membrane layer 1120), where first membrane layer 2110 is permeable to a drug and configured to meter the release rate of a drug disposed in drug reservoir 2300 over a specified period of time and configured to resist cellular infiltration and tissue adhesion, and second membrane layer 2120 is permeable to a drug and configured to promote or allow cellular infiltration and tissue adhesion, similar to first layer 1100 shown in FIGS. 2-4. Like first layer 1100 of drug delivery system 1000 described above, first layer 2100 of drug delivery system 2000 includes a first surface 2102 and a second surface 2104.

[0105] The second layer 2200 of the drug delivery system 2000 shown in FIG. 5 includes a first surface 2202 and a second surface 2204 and is formed from a first membrane layer 2210 and a second membrane layer 2220, where the first membrane layer 2210 is impermeable to a drug. The second membrane layer 2220 of the drug delivery system 2000 shown in FIG. 5 is similar to the second membrane layer 1220 shown in FIGS. 2-4 in that the second membrane layer 2220 shown in FIG. 5 is configured to promote or allow cell infiltration and tissue adhesion. However, unlike the previous example, the first membrane layer 2210 is impermeable to a drug disposed within the drug reservoir 2300. Alternatively, the drug delivery system 2000 can be configured such that the first layer 2100 is drug impermeable, but the second layer 2200 is drug permeable. The drug-permeable layer (e.g., first layer or second layer 2100 or 2200) can include a first drug-permeable membrane layer configured to resist cell infiltration and tissue adhesion, and / or a second drug-permeable membrane layer configured to promote or allow cell infiltration and tissue adhesion. The drug-impermeable layer (e.g., first layer or second layer 2100 or 2200) can then include a first drug-impermeable membrane layer configured to resist cell infiltration and tissue adhesion, and / or a second drug-impermeable membrane layer configured to promote or allow cell infiltration and tissue adhesion.

[0106] With continued reference to FIG. 5 , the second membrane layer 2220 can be formed from any biocompatible material discussed herein, e.g., a biocompatible polymer, which can be further combined with an elastomer or elastomeric material to form a composite material that is impermeable to drugs. For example, the second membrane layer 2220 can include a composite material including a microporous polymer membrane having nodes and fibrils, where the pores are spaces within a matrix of fibrils (e.g., ePTFE), and a sealing material, such as an elastomeric material, present therein. In some embodiments, the sealing material can be imbibed into the polymer membrane to form a drug-impermeable membrane layer. It should be understood that multiple types of fluoropolymer (and non-fluoropolymer) membranes and multiple types of elastomeric materials can be combined to form composite materials within the scope of the present disclosure. It should also be understood that the elastomeric material can include multiple elastomers and multiple types of non-elastomeric components, such as inorganic fillers, therapeutic agents, radiopaque markers, etc., within the scope of the present disclosure.

[0107] In some embodiments, the various membrane layers are formed from expanded polytetrafluoroethylene (ePTFE), although other biocompatible polymers suitable for use in forming drug-impermeable membrane layers can be used, including, but not limited to, urethanes, silicones (organopolysiloxanes), silicone-urethane copolymers, styrene / isobutylene copolymers, polyisobutylene, polyethylene-co-poly(vinyl acetate), polyester copolymers, nylon copolymers, fluorinated hydrocarbon polymers and copolymers, or mixtures of any of the foregoing.

[0108] In various embodiments, the elastomer or elastomeric material can include perfluoromethyl vinyl ether and tetrafluoroethylene, (per)fluoroalkyl vinyl ether (PAVE), copolymers of tetrafluoroethylene and perfluoromethyl vinyl ether, silicone, fluoroelastomer, urethane, or TFE / PMVE copolymer.

[0109] 5 , by including a drug-permeable first layer 2100 and a drug-impermeable second layer 2200, the drug delivery system 2000 can be configured to unidirectionally meter and dispense a drug disposed within the drug reservoir 2300. That is, in some embodiments, the drug delivery system 2000 can be configured such that a drug is metered and released through one of the first and second layers 2100 and 2200, but not through the other of the first and second layers 2100 and 2200. Thus, in these embodiments, the drug delivery system 2000 can be configured to release a drug in a first direction (e.g., through the first layer 2100) without releasing a drug in a second direction (e.g., through the second layer 2200). Providing this type of controlled release helps direct the distribution of the drug to a designated tissue. For example, a drug may be released in a direction toward the scleral tissue while minimizing drug release toward the conjunctival tissue, which may be useful for treating conditions inside the eye. Alternatively, a drug may be released in a direction toward the conjunctival tissue while minimizing drug release toward the scleral tissue, which may be useful for treating other ocular conditions, such as conditions affecting the exterior of the eye (e.g., dry eye). Releasing a drug toward the conjunctival tissue may be used to treat other areas or regions of the body, as drug distributed to the conjunctiva may be absorbed by the surrounding vasculature and transported to other areas of the patient's anatomy. It should be understood that when used herein with respect to the first and second layers 2100 and 2200, the terms first and second are general identifiers, and thus the layers 2100 and 2200 may be referred to in conjunction with alternative general identifiers, such as top, bottom, lower, side, etc. Thus, while layer 2100 is referred to above in conjunction with the term "first" and layer 2200 is referred to above in conjunction with the term "second," it should be understood that layers 2100 and 2200 may alternatively be referred to as first layer 2200 and second layer 2100.That is, the terms “first” and “second” should not be understood to represent anything more than general identifiers for layers 2100 and 2200 .

[0110] In some embodiments, one or more of the first layer and second layer can be configured to include one or more drug-permeable portions and one or more drug-impermeable portions. Turning now to FIGS. 6 and 7, a drug delivery system 3000 is shown, including a first layer 3100 and a second layer 3200. The second layer 3200 is consistent in form and structure with the second layer 2200 of the drug delivery system 2000 shown in FIG. 5 and described above, including a first membrane layer 3210, a second membrane layer 3220, a first surface 3202, and a second surface 3204. However, the first layer 3100 differs from the previous first layer example in that the first layer 3100 shown in FIGS. 6 and 7 includes a first membrane layer 3110 having a first portion 3112 that is permeable to the drug and a second portion 3114 that is impermeable to the drug. The first membrane layer 3110 is configured to measure the release rate of a drug disposed within the drug reservoir 1300 over a specified period of time. The second membrane layer 3120 is similar to the second membrane layer 3120 of the drug delivery system 1000 shown in Figure 5 above.

[0111] In various embodiments, the first portion 3112 of the first membrane layer 3110 generally includes gaps, perforations, pores, channels, or other release features that are sized and shaped such that a drug disposed in the drug reservoir 3300 can be released through the first portion 3112. In some embodiments, the metering of the release of a drug disposed in the drug reservoir 3300 by the first layer 3100 can be adjusted or otherwise controlled by increasing (or alternatively decreasing) the surface area of the metering first portion 3112 of the first membrane layer 3110. In some embodiments, increasing the surface area of the metering first portion 3112 from a first surface area to a second, larger surface area is associated with an increase in the amount of drug released by the drug delivery system 3000 per unit time. Similarly, decreasing the surface area of the metering first portion 3112 from a first surface area to a second, smaller surface area is associated with a decrease in the amount of drug released by the drug delivery system 3000 per unit time.

[0112] For example, if a drug delivery system includes a drug reservoir having a first size (e.g., volume) and a first drug metering membrane layer having a first surface area and comprising a first material having a first release rate per unit area, the drug delivery system is associated with a first drug release rate per unit time and metering of drug release for a first period of time. It should be understood that if the size of the drug reservoir is increased from the first size to a second, larger size while maintaining the first surface area and first material of the metering membrane layer, the drug delivery system is operable to meter release of drug for a second period of time that is longer than the first period of time. On the other hand, if the first material of the metering membrane layer and the first size of the drug reservoir are maintained, but the first surface area of the metering membrane layer is reduced to a second, reduced surface area, the drug delivery system is operable to meter release of drug for a third period of time that is longer than the first period of time. It should further be understood that if the first size of the drug reservoir and the first material of the metering membrane layer are maintained, while the first material of the metering membrane layer is changed to a second material having a second, reduced release rate per unit area, the drug delivery system can operate to meter the release of the drug over a fourth period of time that is longer than the first period of time. Combinations of the above concepts can be utilized to maintain the drug release period while increasing the amount of drug released per unit time. For example, it should be understood that if the size of the drug reservoir is increased from a first size to a second, larger size, combined with increasing the surface area of the metering membrane layer from the first surface area to a second, increased surface area, while maintaining the first material of the metering membrane layer, the drug delivery system can operate to increase the amount of drug released during the first period of time.

[0113] It should also be appreciated that different materials may have different flow rates per unit area, for example, based on different microstructures (e.g., increased amounts and / or sizes of gaps, perforations, pores, channels, or other release features present in the microstructures). Accordingly, different materials may additionally or alternatively be selected to adjust or control the degree or amount of metered release of the agent disposed within the agent reservoir.

[0114] Thus, the various drug delivery systems discussed herein provide configurations that include relatively large drug reservoirs without inherently high drug release rates due to the associated large drug metering surface area, or relatively small drug reservoirs without inherently low drug release rates due to the associated low drug metering surface area. A relatively large drug reservoir combined with a low release rate provides a drug delivery system 1000 that can be implanted for extended periods of time (e.g., weeks, months, a year or more) without requiring intervention to replenish the drug. Conversely, a relatively small drug reservoir combined with a high release rate provides a drug delivery system that can be implanted and dispensed at a high rate without being oversized and interfering with normal ocular functions (e.g., blinking and eye movement).

[0115] Furthermore, it should be understood that drugs having a coarser molecular structure generally require the drug delivery system to include a microstructure with interstices, pores, channels, and / or other release features corresponding in size to allow the drug to pass through the material of the drug-metering membrane layer. Accordingly, it should be understood that different drug delivery systems can be selected for use in administering different drugs.

[0116] 6 and 7 , the first membrane layer 3110 of the first layer 3100 can be formed from one or more materials, such as a sheet or film of any of the biocompatible materials discussed herein, where the sheet or film of the one or more materials is further combined with a sealing material, such as an elastomer or elastomeric material, in the drug-impermeable second portion 3114. Thus, in some embodiments, the drug-impermeable second portion 3114 of the first membrane layer 3110 of the first layer 3100 can comprise a composite structure. In some embodiments, the drug-impermeable second portion 3114 of the first membrane layer 3110 of the first layer 3100 can correspond to a portion of the first membrane layer 3110 of the first layer 3100 that is selectively imbibed and / or coated with a sealing material. That is, in various embodiments, the first membrane layer 3110 of the first layer 3100 can be configured such that one or more portions of the first membrane layer 3110 include a sealing material, and one or more other portions of the first membrane layer 3110 do not include a sealing material, the portions of the first membrane layer 3110 including the sealing material corresponding to the drug-impermeable second portion 3114, and the portions of the first membrane layer 3110 not including the sealing material corresponding to the drug-measuring first portion 3112.

[0117] 6 and 7 includes an oval-shaped drug-measuring first portion 3112, which may be formed from other shapes and / or sizes (e.g., square, rectangular, trapezoidal, bean-shaped, or any other polygonal or non-polygonal shape) other than those shown in the accompanying figures, so long as the drug-measuring first portion 3112 effectively achieves its intended purpose of metering the release of the drug. Accordingly, it should be understood that the boundary defined between the drug-measuring first portion 3112 and the drug-impermeable second portion 3114 may define any suitable shape consistent with the above.

[0118] It should also be understood that while the drug delivery system 3000 shown in Figure 7 includes only a single, centrally located drug dosage first portion 3112, the first membrane layer 3110 of the first layer 3100 can include multiple distinct drug dosage first portions 3112. Likewise, it should be understood that the drug dosage first portion 3112 of the first membrane layer 3110 of the first layer 3100 need not be centrally located, but instead can be located at a position offset from the central location.

[0119] In various embodiments, a drug delivery system can be configured such that one or more of the drug-metering membrane layers discussed herein can be exposed to a tissue surface of a patient's anatomy. For example, turning now to FIGS. 8 and 9, a drug delivery system 4000 is shown that includes a first layer 4100 and a second layer 4200. The second layer 4200 is similar to the second layer 2200 of the drug delivery system 2000 shown in FIG. 5 and discussed above, in that the second layer 4200 is impermeable to the drug and includes a drug-impermeable first membrane layer 4210 and a second membrane layer 4220 configured to promote or allow cell infiltration and tissue adhesion. Like the drug delivery system 2000 shown in FIG. 5, the second layer 4200 includes a first surface 4202 and a second surface 4204.

[0120] The first layer 4100 shown in FIGS. 8 and 9, however, differs from the previous first layer examples in that the first layer 4100 shown in FIGS. 8 and 9 includes an aperture or relief that exposes a portion of the first membrane layer 4110. The first membrane layer 4110 is configured to measure the release rate of a drug disposed within the drug reservoir 4300 over a specified period of time. In particular, as shown in FIGS. 8 and 9, the second membrane layer 4120 includes an aperture 4124 formed in the body 4122 of the second membrane layer 4120, the aperture 4124 in the second membrane layer 4120 of the first layer 4100 acting to expose the first membrane layer 4110. When implanted, one or more portions of the first membrane layer 4110 of the first layer 4100 are directly exposed to tissue, while the second membrane layer 4120 acts to maintain separation between the first membrane layer 4110 and the tissue surface.

[0121] Direct exposure of first membrane layer 4110 of first layer 4100 helps enable more effective and efficient drug delivery to the tissue. Maintaining separation between first membrane layer 4110 and the tissue surface helps minimize micromotion between first membrane layer 4110 and the tissue. As discussed above, minimizing micromotion helps minimize microirritation.

[0122] Thus, in various embodiments, the drug delivery system 4000 includes a drug-permeable first layer 4100 and a drug-impermeable second layer 4200, the first layer 4100 including a first membrane layer 4110 and a second membrane layer 4120, the first membrane layer 4110 being permeable to the drug and configured to resist cell infiltration and tissue adhesion, the second membrane layer 4120 being permeable to the drug and configured to promote or allow cell infiltration and tissue adhesion, and the second membrane layer 4120 being configured such that, when implanted, one or more portions of the first membrane layer 4110 are exposed to the tissue, while during implantation, the second membrane layer 4120 is positioned between the tissue and one or more other portions of the first membrane layer 4110.

[0123] In some embodiments, the various drug delivery systems discussed herein are configured as thin, puck-shaped members. The drug delivery system can include a thickness between the exterior-facing surfaces (e.g., the distance measured between the second surface 1104 of the first layer 1100 and the second surface 1204 of the second layer 1200) of 0.5 millimeters (0.5 mm) or less, e.g., 0.1 millimeters (0.1 mm) to 0.5 millimeters (0.5 mm), although various dimensions are contemplated. For example, given different anatomical structures of the human body, the drug delivery system can exceed 0.5 millimeters (0.5 mm) without departing from the spirit or scope of the present disclosure, as long as the thickness does not substantially interfere with normal ocular functions (e.g., turning and blinking).

[0124] In some embodiments, the various drug delivery systems disclosed herein can have a diameter (or width across its major axis) ranging from 5 millimeters to 15 millimeters. In certain embodiments, the drug delivery systems disclosed herein can have a diameter (or width across its major axis) of 10 millimeters. In embodiments in which the drug delivery system is ovoid, the drug delivery system can include a (e.g., elliptical) major dimension of up to about 30 millimeters and a corresponding minor dimension of up to about 10 millimeters. However, as discussed above, given the different anatomical structures of the human body, drug delivery systems can exceed such dimensions (e.g., 15, 10, and 30 millimeters) without departing from the spirit or scope of the present disclosure, so long as the size does not substantially interfere with normal ocular function (e.g., turning and blinking). Similarly, the drug delivery systems disclosed herein can include a diameter (or width across its major axis) of less than 5 millimeters without departing from the spirit or scope of the present disclosure, so long as the drug delivery system is operable to elute a sufficient amount of drug for absorption by surrounding tissue. The shapes and sizes discussed herein should not be seen as limiting.

[0125] Additionally, while the above drug delivery systems are described as including a single drug reservoir, it should be understood that any of the above drug delivery systems can include multiple reservoirs. These reservoirs can be fluidly coupled or separated from one another. In some embodiments, each reservoir can be configured to contain the same or a different drug. Thus, in some embodiments, the drug delivery systems discussed herein can be configured to deliver multiple different drugs, either from the same reservoir or from multiple different reservoirs.

[0126] It should further be understood that in various embodiments, the drug may be loaded onto or otherwise incorporated within bioabsorbable particles, which helps aid in metering of the drug. In some embodiments, the particles may be sized to be dispersed and injected or otherwise delivered in situ into the drug reservoir (e.g., while the drug delivery system is implanted in the patient's eye). That is, in some instances, the drug may be contained in a fluid suspension of particles. In various embodiments, a filled or partially filled drug microporous reservoir may be accessed in situ (e.g., via a syringe or other suitable means), and the reservoir contents (e.g., particles) may be removed and / or reloaded with fresh particles to maintain constant drug delivery over time. In various embodiments, placement of the fluid suspension of particles within the drug reservoir may be accomplished via a syringe or other suitable delivery means.

[0127] In some embodiments, the drug delivery systems discussed herein are configured such that the drug microporous reservoir retains particles within the drug reservoir and allows a dispersed carrier fluid (e.g., water) to exit the reservoir through one or more layers of the drug delivery system. For example, in some embodiments, the material defining the drug reservoir (e.g., one or more of the first, second, third, or fourth microporous layers) can include a microstructure configured to prevent particles of a fluid suspension from passing through the material. For example, the first microporous layer can be configured to resist tissue ingrowth and can include gaps, perforations, pores, channels, or combinations thereof that prevent particles of a fluid suspension from passing through the material. In some embodiments, the particles are configured to degrade or disintegrate over time so that the drug (alone or in solution with a fluid) can permeate, diffuse, or otherwise pass through one or more layers of the microporous reservoir from the interior of the drug reservoir to the exterior of the drug delivery system for absorption by the body. In some embodiments, the concentration of the dispersed carrier fluid and the solution of particles changes or can be changed over time. For example, particles can be added (e.g., in situ) to a dispersion carrier fluid to increase the concentration of particles in the reservoir. Additionally or alternatively, dispersion carrier fluid can be added to decrease the concentration of particles in the reservoir.

[0128] In some embodiments, the various drug delivery systems disclosed herein can additionally or alternatively include one or more structural spacers, such as one or more stents, struts, and / or reinforcing elements. The one or more structural spacers can be incorporated into, integrated with, bonded to, or otherwise disposed within the reservoirs to maintain separation between the microporous layers forming the reservoirs. Such structural spacers can be formed from any suitable biocompatible material discussed herein (e.g., natural materials or synthetic materials such as metals and polymers).

[0129] The scope of the present invention of this application has been described above both generally and with reference to specific embodiments and examples. It will be apparent to those skilled in the art that various modifications and variations can be made in the embodiments and examples without departing from the scope of the present disclosure. Similarly, various components discussed in the embodiments and examples discussed herein can be combined. Therefore, the embodiments and examples are intended to cover modifications and variations within the scope of the present invention. (Aspect) (Aspect 1) 1. An implantable delivery device for dispensing a drug, comprising: a first microporous layer comprising a plurality of pores sized to permit tissue ingrowth; a second microporous layer comprising a plurality of pores sized to permit tissue ingrowth; a third microporous layer bonded to the first microporous layer, the third microporous layer including a plurality of pores sized to resist tissue ingrowth; and a reservoir defined between the third microporous layer and the second microporous layer for receiving a drug; Including, The third microporous layer is configured to meter the rate at which the drug is eluted from the reservoir when the delivery device is implanted. (Aspect 2) 2. The device of embodiment 1, further comprising a fourth microporous layer coupled to the second microporous layer such that the reservoir is defined between the third microporous layer and the fourth microporous layer. (Aspect 3) 3. The device of embodiment 2, wherein the fourth microporous layer comprises a plurality of pores sized to resist tissue ingrowth, and wherein the fourth microporous layer is permeable to the agent. (Aspect 4) The device of embodiment 2, wherein the fourth microporous layer is impermeable to the agent. (Aspect 5) 5. The device of embodiment 4, wherein the fourth layer comprises an elastomer. (Aspect 6) The device of any one of embodiments 1-5, wherein the first microporous layer comprises an aperture configured to expose the third microporous layer. (Aspect 7)

[0023] The device of any one of embodiments 1-6, further comprising one or more structural spacers disposed within the reservoir to maintain separation between the second microporous layer and the third microporous layer. (Aspect 8)

[0023] Aspect 8. The device of any one of aspects 1-7, wherein the reservoir is configured to be refilled and emptied in situ. (Aspect 9)

[0023] Aspect 9. The device of any one of aspects 1-8, wherein the reservoir is configured to expand to accommodate the agent therein. (Aspect 10)

[0023] Embodiment 10. The device of any one of embodiments 1-9, wherein at least one of the first microporous layer and the second microporous layer comprises an expanded polytetrafluoroethylene (ePTFE) membrane. (Aspect 11) 11. The device of any one of embodiments 1-10, wherein a first portion of the third microporous layer is impermeable to the drug and a second portion of the third microporous layer is permeable to the drug. (Aspect 12) 12. The device of embodiment 11, wherein the first portion of the third microporous layer comprises an elastomer. (Aspect 13) The device of any one of embodiments 1 to 12, wherein the delivery device is implantable intraocularly. (Aspect 14) The device of embodiment 13, wherein the medication is an ophthalmic medication for treating glaucoma. (Aspect 15) 1. An implantable delivery device for dispensing a drug, comprising: a first microporous layer bonded to a second microporous layer to define a reservoir including a first inner surface and an opposing second inner surface; and a body having an outer surface; Including, the first inner surface is separable from the second inner surface when the reservoir is filled with a drug; the first inner surface is configured to meter the delivery of an agent over a predetermined period of time, the first inner surface is configured to resist tissue ingrowth; and A device wherein the exterior surface of the body is configured to allow tissue ingrowth. (Aspect 16) 16. The device of embodiment 15, wherein at least a portion of the first interior surface is permeable to the agent. (Aspect 17) The device of embodiment 15 or embodiment 16, wherein the second inner surface is impermeable to the agent. (Aspect 18) 18. The device of embodiment 17, wherein the second inner surface comprises an elastomer. (Aspect 19) 19. The device of any one of embodiments 15-18, wherein the reservoir is configured to be refilled and emptied in situ. (Aspect 20) Aspect 20. The device of any one of aspects 15-19, wherein the reservoir is configured to expand to accommodate the agent therein. (Aspect 21) 21. The device of any one of embodiments 15-20, wherein at least one of the first microporous layer and the second microporous layer comprises an expanded polytetrafluoroethylene (ePTFE) membrane. (Aspect 22) 22. The device of any one of embodiments 15-21, wherein a first portion of the first inner surface is impermeable to the drug and a second portion of the first inner surface is permeable to the drug. (Aspect 23) 23. The device of embodiment 22, wherein the first portion of the first inner layer comprises an elastomer. (Aspect 24) The device of any one of embodiments 15 to 23, wherein the delivery device is implantable intraocularly. (Aspect 25) The device according to any one of aspects 15 to 24, wherein the medication is an ophthalmic medication for treating glaucoma. (Aspect 26) 1. A delivery device for dispensing a medication, comprising: a microporous body including a first microporous layer, a second microporous layer, and a third microporous layer; and a drug reservoir disposed between the first microporous layer and the third microporous layer; Including, The device, wherein the first microporous layer is positioned between the second microporous layer and the third microporous layer, the first microporous layer comprising a plurality of pores sized to resist tissue ingrowth, and the second microporous layer and the third microporous layer each comprising a plurality of pores sized to permit tissue ingrowth. (Aspect 27) 27. The device of embodiment 26, wherein the first microporous layer comprises a metering portion for dispensing the agent over a period of time. (Aspect 28) The device of embodiment 26 or embodiment 27, wherein the second microporous layer and the third microporous layer define an exterior of the delivery device. (Aspect 29) 29. The device of any one of embodiments 26-28, wherein the first microporous layer is bonded to the second microporous layer. (Aspect 30) 30. The device of embodiment 29, wherein the second microporous layer comprises an aperture configured to expose the first microporous layer. (Aspect 31) Aspect 31. The device of any one of aspects 26-30, wherein the drug reservoir is configured to be refilled and emptied in situ. (Aspect 32) Aspect 32. The device of any one of aspects 26-31, wherein the drug reservoir is configured to expand to accommodate the drug therein. (Aspect 33) The device of any one of aspects 26 to 32, wherein at least one of the first microporous layer, the second microporous layer, and the third microporous layer comprises an expanded polytetrafluoroethylene (ePTFE) membrane. (Aspect 34) 34. The device of any one of aspects 26 to 33, wherein the first microporous layer comprises a first portion that is permeable to the drug and a second portion that is impermeable to the drug, the second portion of the first microporous layer comprising an elastomer. (Aspect 35) The device of any one of embodiments 26 to 34, wherein the delivery device is implantable intraocularly. (Aspect 36) The device of any one of aspects 27 to 35, wherein the medicament is an ophthalmic medication for treating glaucoma. (Aspect 37) 1. A drug metering device having an exterior surrounding an interior defining a drug reservoir, a first layer comprising a first microporous layer and a second microporous layer; and a second layer coupled to the first layer such that the drug reservoir is defined between the first and second layers; Including, A device, wherein a first microporous layer is configured to resist tissue ingrowth and the second microporous layer is configured to permit tissue ingrowth, the first microporous layer defining a portion of the interior and the second microporous layer defining a portion of the exterior, the portion of the first microporous layer of the first layer being permeable to a drug disposable within the drug reservoir. (Aspect 38) 38. The device of claim 37, wherein the drug reservoir is defined between portions of the first layer and the second layer that are not bonded to one another so that the unbonded portions of the first layer and the second layer are free to flex relative to one another. (Aspect 39) The device of aspect 37 or aspect 38, wherein the second layer includes a third microporous layer and a fourth microporous layer, the third microporous layer of the second layer configured to resist tissue ingrowth and the fourth microporous layer of the second layer configured to allow tissue ingrowth, the third microporous layer of the second layer defining a portion of the interior, and the fourth microporous layer defining a portion of the exterior. (Aspect 40)

[0039] 40. The device of any one of embodiments 37-39, wherein the first microporous layer and the second microporous layer of the first layer comprise expanded polytetrafluoroethylene (ePTFE). (Aspect 41) 41. The device of any one of aspects 37 to 40, wherein the first microporous layer of the first layer comprises a plurality of pores sized to resist tissue ingrowth, and the second microporous layer of the first layer comprises a plurality of pores sized to permit tissue ingrowth. (Aspect 42) 42. The device of any one of aspects 39 to 41, wherein the third microporous layer of the second layer comprises a plurality of pores sized to resist tissue ingrowth, and the fourth microporous layer of the second layer comprises a plurality of pores sized to permit tissue ingrowth. (Aspect 43) 43. The device of any one of aspects 39 to 42, wherein the third microporous layer of the second layer comprises an elastomer such that the third microporous layer of the second layer is impermeable to a drug. (Aspect 44) 44. The device of any one of aspects 37 to 43, wherein the first microporous layer of the first layer comprises a first portion that is permeable to the drug and a second portion that is impermeable to the drug, and the second portion of the first microporous layer of the first layer comprises an elastomer. (Aspect 45) The device of any one of embodiments 37 to 44, wherein the delivery device is implantable intraocularly. (Aspect 46) 46. The device of embodiment 45, wherein the medication is an ophthalmic medication for treating glaucoma. (Aspect 47) 46. The device of embodiment 45, wherein the agent is contained within a fluid suspension of particles. (Aspect 48) 48. The device of embodiment 47, wherein the first microporous layer of the first layer comprises a plurality of pores sized to prevent particles from passing through the first microporous layer.

Claims

1. 1. An implantable delivery device for dispensing a drug, comprising: a first microporous layer comprising a plurality of pores sized to permit tissue ingrowth; a second microporous layer comprising a plurality of pores sized to permit tissue ingrowth; a third microporous layer overlying and bonded to the first microporous layer, the third microporous layer including a plurality of pores sized to resist tissue ingrowth; and a reservoir defined between the third microporous layer and the second microporous layer for receiving a drug; Including, the first microporous layer, the second microporous layer, and the third microporous layer are formed of a microporous material; the reservoir is expandable to an expanded state when the reservoir is filled with the agent and collapsible toward a contracted state as the agent is emptied from the reservoir; The third microporous layer is configured to meter the rate at which the drug is eluted from the reservoir based on the plurality of pores when the delivery device is implanted.

2. The device of claim 1 , further comprising a fourth microporous layer laminated and bonded to the second microporous layer such that the reservoir is defined between the third and fourth microporous layers.

3. The device of claim 2 , wherein the fourth microporous layer comprises a plurality of pores sized to resist tissue ingrowth, and the fourth microporous layer is permeable to the agent.

4. The device of claim 2 , wherein the fourth microporous layer is impermeable to the drug.

5. The device of claim 4 , wherein the fourth microporous layer comprises an elastomer.

6. The device of any one of claims 1 to 5, wherein the first microporous layer includes an aperture configured to expose the third microporous layer.

7. The device of any one of claims 1 to 6, further comprising one or more structural spacers disposed within the reservoir to maintain separation between the second microporous layer and the third microporous layer.

8. The device of any one of claims 1 to 7, wherein the reservoir is configured to be refilled and emptied in situ.

9. The device of any preceding claim, wherein the reservoir is configured to expand to accommodate the agent therein.

10. The device of any one of claims 1 to 9, wherein at least one of the first microporous layer and the second microporous layer comprises an expanded polytetrafluoroethylene (ePTFE) membrane.

11. The device of any one of claims 1 to 10, wherein a first portion of the third microporous layer is impermeable to the drug and a second portion of the third microporous layer is permeable to the drug.

12. The device of claim 11 , wherein the first portion of the third microporous layer comprises an elastomer.

13. The device of any one of claims 1 to 12, wherein the delivery device is implantable within the eye.

14. The device of claim 13 , wherein the medication is an ophthalmic medication for treating glaucoma.

15. 1. An implantable delivery device for dispensing a drug, comprising: a first microporous layer joined at a peripheral edge to a second microporous layer to define a reservoir including a first inner surface and an opposing second inner surface; and a body having an outer surface; Including, each of the first inner surface, the second inner surface, and the outer surface is formed of a microporous material; the first inner surface is separable from the second inner surface when the reservoir is filled with a drug and is collapsible toward the second inner surface as the reservoir is emptied of the drug; the first inner surface is configured to meter the delivery of an agent over a predetermined period of time, the first inner surface is configured to resist tissue ingrowth; and A device wherein the exterior surface of the body is configured to allow tissue ingrowth.

16. 16. The device of claim 15, wherein at least a portion of the first inner surface is permeable to the agent.

17. 17. The device of claim 15 or claim 16, wherein the second inner surface is impermeable to the drug.

18. The device of claim 17 , wherein the second inner surface comprises an elastomer.

19. A device according to any one of claims 15 to 18, wherein the reservoir is adapted to be refilled and emptied in situ.

20. The device of any one of claims 15 to 19, wherein the reservoir is configured to expand to accommodate the agent therein.

21. The device of any one of claims 15 to 20, wherein at least one of the first microporous layer and the second microporous layer comprises an expanded polytetrafluoroethylene (ePTFE) membrane.

22. The device of any one of claims 15 to 21, wherein a first portion of the first inner surface is impermeable to the drug and a second portion of the first inner surface is permeable to the drug.

23. The device of claim 22 , wherein the first portion of the first inner surface comprises an elastomer.

24. The device of any one of claims 15 to 23, wherein the delivery device is implantable within the eye.

25. The device of any one of claims 15 to 24, wherein the drug is an ophthalmic drug for treating glaucoma.

26. 1. A delivery device for dispensing a medication, comprising: a microporous body including a first microporous layer, a second microporous layer, and a third microporous layer; and a drug reservoir disposed between the first microporous layer and the third microporous layer; Including, the first microporous layer is positioned between the second microporous layer and the third microporous layer, the first microporous layer comprising a plurality of pores sized to resist tissue ingrowth, and the second microporous layer and the third microporous layer each comprising a plurality of pores sized to permit tissue ingrowth; the first microporous layer, the second microporous layer, and the third microporous layer are formed of a microporous material; the drug reservoir is operable to transition between an expanded state and a collapsed state; The device, wherein the plurality of pores in the third microporous layer are configured to correspondingly measure the rate at which the drug elutes from the drug reservoir.

27. 27. The device of claim 26, wherein the first microporous layer includes a metering portion for dispensing a drug over a period of time.

28. 28. The device of claim 26 or claim 27, wherein the second microporous layer and the third microporous layer define an exterior of the delivery device.

29. The device of any one of claims 26 to 28, wherein the first microporous layer is laminated and bonded to the second microporous layer.

30. 30. The device of claim 29, wherein the second microporous layer includes an aperture configured to expose the first microporous layer.

31. A device according to any one of claims 26 to 30, wherein the drug reservoir is adapted to be refilled and emptied in situ.

32. The device of any one of claims 26 to 31, wherein the drug reservoir is configured to expand to accommodate the drug therein.

33. 33. The device of any one of claims 26-32, wherein at least one of the first microporous layer, the second microporous layer, and the third microporous layer comprises an expanded polytetrafluoroethylene (ePTFE) membrane.

34. 34. The device of any one of claims 26 to 33, wherein the first microporous layer comprises a first portion that is permeable to the drug and a second portion that is impermeable to the drug, the second portion of the first microporous layer comprising an elastomer.

35. The device of any one of claims 26 to 34, wherein the delivery device is implantable within the eye.

36. The device of any one of claims 27 to 35, wherein the drug is an ophthalmic drug for treating glaucoma.

37. 1. A drug metering device having an exterior surrounding an interior defining a drug reservoir, a first layer comprising a first microporous layer and a second microporous layer; and a second layer joined to the first layer at a peripheral edge such that the drug reservoir is defined between the first and second layers; Including, the first microporous layer and the second microporous layer comprise a microporous microstructure; a first microporous layer configured to resist tissue ingrowth and the second microporous layer configured to permit tissue ingrowth, the first microporous layer defining a portion of the interior and the second microporous layer defining a portion of the exterior, the portion of the first microporous layer of the first layer being permeable to a disposable agent within the drug reservoir, whereby the first layer is configured to measure a rate at which the agent elutes from the drug reservoir; The device, wherein the drug reservoir is operable to transition between an expanded state and a collapsed state.

38. 38. The device of claim 37, wherein the drug reservoir is defined between portions of the first and second layers that are not bonded to one another such that portions of the first and second layers other than those bonded at the peripheral edges are free to flex relative to one another.

39. 39. The device of claim 37 or claim 38, wherein the second layer comprises a third microporous layer and a fourth microporous layer, the third microporous layer of the second layer configured to resist tissue ingrowth and the fourth microporous layer of the second layer configured to permit tissue ingrowth, the third microporous layer of the second layer defining a portion of the interior and the fourth microporous layer defining a portion of the exterior.

40. 40. The device of any one of claims 37-39, wherein the first microporous layer and the second microporous layer of the first layer comprise expanded polytetrafluoroethylene (ePTFE).

41. 41. The device of any one of claims 37 to 40, wherein the first microporous layer of the first layer comprises a plurality of pores sized to resist tissue ingrowth and the second microporous layer of the first layer comprises a plurality of pores sized to permit tissue ingrowth.

42. 40. The device of claim 39, wherein the third microporous layer of the second layer comprises a plurality of pores sized to resist tissue ingrowth and the fourth microporous layer of the second layer comprises a plurality of pores sized to permit tissue ingrowth.

43. 43. The device of claim 39 or 42, wherein the third microporous layer of the second layer comprises an elastomer such that the third microporous layer of the second layer is impermeable to a drug.

44. 44. The device of any one of claims 37 to 43, wherein the first microporous layer of the first layer comprises a first portion that is permeable to the drug and a second portion that is impermeable to the drug, and the second portion of the first microporous layer of the first layer comprises an elastomer.

45. The device of any one of claims 37 to 44, wherein the device is implantable within the eye.

46. The device of any one of claims 37 to 45, wherein the drug is an ophthalmic drug for treating glaucoma.

47. A device according to any one of claims 37 to 46, wherein the agent is contained within a fluid suspension of particles.

48. 48. The device of any one of claims 37 to 47, wherein the first microporous layer of the first layer comprises a plurality of pores sized to prevent particles from passing through the first microporous layer.

49. 16. The device of claim 15, wherein the first inner surface has a first permeability and the second inner surface has a second permeability different from the first permeability.

50. 50. The device of claim 49, wherein the second permeability is less than the first permeability.

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