The patent's inventors are Byrne, Mark E. (Auburn, AL); Venkatesh, Siddarth (Auburn, AL).
This patent was filed on February 3, 2006 and was cleared and issued on January 8, 2013.
From the background information supplied by the inventors, news correspondents obtained the following quote: "Delivering medications via contact lenses has been a prevailing notion since the inception of using hydrophilic, crosslinked polymer gels on the surface of the eye. In fact, the first patent in the field from Otto Wichterle in 1965 states that 'bacteriostatic, bacteriocidal or otherwise medicinally active substances such as antibiotics may be dissolved in the aqueous constituent of the hydrogels to provide medication over an extended period, via diffusion.' However, there is evidence that this notion of a dissolved component in an aqueous constituent has been around for a much longer period of time. Evidence exists that honey soaked linen was used in ancient Rome as an ophthalmic dressing in the treatment of disease.
"The biggest obstacle to using the fluid entrained in the aqueous portion of the polymer gel is maintaining a significant concentration of drug within the fluid to have a therapeutically relevant effect, which is ultimately limited by the solubility of the drug. This has been the primary reason why drug release from contact lenses has not become a clinical or commercial success. To an equivalent extent, the control over the drug delivery profile and an extended release profile is also important to therapeutic success and has not been demonstrated using these methods. Drug uptake and release by conventional (i.e., currently available) soft contact lenses can lead to a moderate intraocular concentration of drug for a very short period of time, but does not work very well due to a lack of sufficient drug loading and poor control of release. The use of soft, biomimetic contact lens carriers (i.e., recognitive polymeric hydrogels) described herein has the potential to greatly enhance ocular drug delivery by providing a significant designed and tailorable increase in drug loading within the carrier as well as prolonged and sustained release with increased bioavailability, less irritation to ocular tissue, as well as reduced ocular and systemic side effects.
"The ocular bioavailability of drugs applied to the eye is very poor (i.e., typically less than 1-7% of the applied drug results in absorption with the rest entering the systemic circulation). Factors such as ocular protective mechanisms, nasolacrimal drainage, spillage from the eye, lacrimation and tear turnover, metabolic degradation, and non-productive adsorption/absorption, etc., lead to poor drug absorption in the eye. Currently, more efficient ocular delivery rests on enhancing drug bioavailability by extending delivery and/or by increasing drug transport through ocular barriers (e.g., the cornea--a transparent, dome-shaped window covering the front of the eye; the sclera--the tough, opaque, white of the eye; and the conjunctiva--a mucous membrane of the eye with a highly vascularized stroma that covers the visible part of the sclera). A topically applied drug to the eye is dispersed in the tear film and can be removed by several mechanisms such as: (i) irritation caused by the topical application, delivery vehicle, or drug which induces lacrimation leading to dilution of drug, drainage, and drug loss via the nasolacrimal system into the nasopharynx and systemic circulation (e.g., the rate drainage increases with volume); (ii) normal lacrimation and lacrimal tear turnover (16% of tear volume per minute in humans under normal conditions); (iii) metabolic degradation of the drug in the tear film; (iv) corneal absorption of the drug and transport; (v) conjunctival absorption of the drug and scleral transport; (vi) conjunctival `non-productive` absorption via the highly vascularized stroma leading to the systemic circulation; and (vii) eyelid vessel absorption leading to systemic circulation. Therefore, due to these mechanisms, a relatively low proportion of the drug reaches anterior chamber ocular tissue via productive routes such as mechanisms (iv) and (v).
"For posterior eye tissue and back of the eye diseases (e.g., age-related macular degeneration, retinal degeneration, diabetic retinopathy, glaucoma, retinitis pigmentosa, etc.), the amount of drug delivered can be much less compared to front of the eye disease. To treat back of the eye disease, four approaches have typically been used, topical, oral (systemic delivery), intraocular, and periocular delivery.
"Topically applied drugs diffuse through the tear film, cornea/sclera, iris, ciliary body, and vitreous before reaching posterior tissues, but due to the added transport resistances do not typically lead to therapeutically relevant drug concentrations. However, researchers have shown that topically applied drugs do permeate through the sclera by blocking corneal absorption and transport. Intravitreal injections (injections into the eye) require repeated injections and have potential side effects (hemorrhage, retinal detachment, cataract, etc.) along with low patient compliance. Extended release devices have been used but require intraocular surgery and often have the same incidence of side effects. Periocular drug delivery is less invasive and also requires injections or implant placement for predominantly transscleral delivery.
"To overcome most of these protective mechanisms, topical formulations have remained effective by the administration of very high concentrations of drug multiple times on a daily basis. For a number of drugs high concentrations can lead to negative effects such as burning, itching sensations, gritty feelings, etc., upon exposure of the medication to the surface of the eye as well as increased toxicity and increased ocular and systemic side effects. However, traditional ophthalmic dosage forms such as solutions, suspensions, and ointments account for 90% of commercially available formulations on the market today. Solutions and suspensions (for less water soluble drugs) are most commonly used due to the ease of production and the ability to filter and easily sterilize. Ointments are used to much lesser extent due to vision blurring, difficulty in applying to the ocular surface, and greasiness. The term 'eye drops' herein is meant to refer to all topological medications administered to a surface of the eye including but not limited to solutions, suspensions, ointments and combination thereof. In addition to the aforementioned problems, drug delivery through the use of eye drops does not provide for controlled time release of the drug. Eye drops medications typically have a low residence time of the drug on the surface of the eye.
"The efficacy of topical solutions has been improved by viscosity enhancers that increase the residence time of drugs on the surface of the eye, which ultimately lead to increased bioavailability as well as more comfortable formulations. Also, inclusion complexes have been used for poorly soluble drugs, which increase solubility without affecting permeation.
"Other recent delivery methods have included in situ gel-forming systems, corneal penetration or permeation enhancers, conjunctival muco-adhesive polymers, liposomes, and ocular inserts.
"Ocular inserts, in some cases, achieve a relatively stable or constant, extended release of drug. For example, ocular inserts such as Ocusert.RTM. (Alza Corp., FDA approved in 1974) consist of a small wafer of drug reservoir enclosed by two ethylene-vinyl acetate copolymer membranes, which is placed in the corner of the eye and provides extended release of a therapeutic agent for approximately 7 days (i.e., pilocarpine HCL, for glaucoma treatment reducing intraocular pressure of the eye by increasing fluid drainage). Lacrisert (Merck) is a cellulose based polymer insert used to treat dry eyes. However, inserts have not found widespread use due to occasional noticed or unnoticed expulsion from the eye, membrane rupture (with a burst of drug being released), increased price over conventional treatments, etc.
"Mucoadhesive systems and in-situ forming polymers typically have problems involving the anchorage of the carrier as well as ocular irritation resulting in blinking and tear production. Penentration enhancers may cause transient irritation, alter normal protection mechanisms of the eye, and some agents can cause irreversible damage to the cornea.
"The novel soft, biomimetic contact lens carriers proposed in this work will provide a significant increase in drug loading within the gel as well as prolonged and sustained release. This will lead to prolonged drug activity and increased bioavailability, reduced systemic absorption, reduced ocular and systemic side effects, and increased patient compliance due to reduced frequency of medication and reduced irregularity of administration (i.e., eye drop volume depends on angle, squeeze force, etc., and has been experimentally verified to be highly variable). They will also be able to be positioned easily as well as easily removed with or without use to correct vision impairment. Since they will be positioned on the cornea, this will lead to enhanced corneal permeability as well."
Supplementing the background information on this patent, NewsRx reporters also obtained the inventors' summary information for this patent: "The present invention is directed to a drug delivery methods and systems. The drug delivery system includes a recognitive polymeric hydrogel through which a drug is delivered by contacting biological tissue. The recognitive polymeric hydrogel is formed using a bio-template, which is a drug or is structurally similar to the drug, functionalized monomers, preferably having complexing sites, and cross-linking monomers, which are copolymerized using a suitable initiator, such as described in detail below. The complexing sites of the recognitive polymeric hydrogel that is formed preferably mimics receptor sites of a target biological tissue, biological recognition, or biological mechanism of action. The system unitizes what is referred to herein as a biomimetic recognitive polymeric hydrogel.
"The system in accordance with an embodiment, the system is an ophthalmic drug system. The ophthalmic drug system includes soft contact lenses formed from the biomimetic recognitive polymeric hydrogel and that are impregnated with a drug that can be release over a duration of time while in contact with eyes. The invention is directed to both corrective or refractive contact lenses and non-corrective or non-refractive contact lenses. While the invention as described herein refers primarily to ophthalmic drug systems, it is understood that the present invention has applications in a number of different contact drug delivery systems. For example, the biomimetic recognitive polymeric hydrogel can be used in bandages, dressings, and patch-type drug delivery systems to name a few.
"In accordance with the embodiments of the invention a hydrogel matrix that is formed from silicon-based cross-linking monomers, carbon based or organic-based monomers, macromers or a combination thereof. Suitable cross-linking monomers include but are not limited to Polyethylene glycol (200) dimethacrylate (PEG200DMA), ethylene glycol dimethacrylate (EGDMA), tetraethyleneglycol dimethacrylate (TEGDMA), N,N'-Methylene-bis-acrylamide and polyethylene glycol (600) dimethacrylate (PEG600DMA). Suitable silicon-based cross-linking monomers can include tris(trimethylsiloxy)silyl propyl methacrylate (TRIS) and hydrophilic TRIS derivatives such as tris(trimethylsiloxy)silyl propyl vinyl carbamate (TPVC), tris(trimethylsiloxy)silyl propyl glycerol methacrylate (SIGMA), tris(trimethylsiloxy)silyl propyl methacryloxyethylcarbamate (TSMC); polydimethylsiloxane (PDMS) and PDMS derivatives, such as methacrylate end-capped fluoro-grafted PDMS crosslinker, a methacrylate end-capped urethane-siloxane copolymer crosslinker, a styrene-capped siloxane polymer containing polyethylene oxide and polypropylene oxide blocks; and siloxanes containing hydrophilic grafts or amino acid residue grafts, and siloxanes containing hydrophilic blocks or containing amino acid residue grafts. The molecular structure of these monomers can be altered chemically to contain moieties that match amino acid residues or other biological molecules. In cases where the above monomers, when polymerized with hydrophilic monomers, a solubilizing cosolvent may be used such as dimethylsulfoxide (DMSO), isopropanol, etc. or a protecting/deprotecting group strategy.
"Crosslinking monomer amounts can be from (0.1 to 40%, moles crosslinking monomer/moles all monomers); Functional monomers, 99.9% to 60% (moles functional monomer/moles all monomers) with varying relative portions of multiple functional monomers; initiator concentration ranging from 0.1 to 30 wt %; solvent concentration ranging from 0% to 50 wt % (but no solvent is preferred); monomer to bio-template ratio (M/T) ranging from 0.1 to 5,000, preferably 200 to 1,000, with 950 preferred for the ketotifen polymers presented herein, under an nitrogen or air environment (in air, the wt % of initiator should be increased above 10 wt %.
"The ophthalmic drug delivery system also includes a bio-template, that is drug molecules, prodrugs, protein, amino acid, proteinic drug, oligopeptide, polypeptide, oligonucleotide, ribonucleic acid, deoxyribonucleic acid, antibody, vitamin, or other biologically active compound. This also includes a drug with an attached bio-template. The bio-template is preferably bound to the hydrogel matrix through one or more of electrostatic interactions, hydrogen bonding, hydrophobic interactions, coordination complexation, and Van der Waals forces.
"Bio-templates are preferably weakly bound to a hydrogel matrix through functionalized monomer units, macromer units or oligomer units that are co-polymerized into the hydrogel matrix to form receptor locations within the hydrogel matrix that resemble or mimic the receptor sites or molecules associated with the biological target tissue to be treated with the drug or the biological mechanism of action
"In accordance with the embodiments of the invention, a portion of the bio-template can be washed out from the recognitive hydrogel polymer, loaded with a drug. The polymerization reaction forms a contact lens. For example, the gel is polymerized in a mold or compression casting. After contact lenses are formed they can be used to administer the drug through contact with eyes. Alternatively, the recognitive hydrogel polymer can be formed into contact lenses, washed to remove a portion of the bio-template and then loaded with the drug. Where the bio-template is the drug, the washing step can be illuminated or truncated. In formulations where the bio-template is a drug, the free base form of the drug or hydrochloride salt of the drug can be used.
"In accordance with the method of the present invention, a biomimetic recognitive polymeric hydrogel is formed by making a mixture or solution that includes amounts of a bio-template or drug, functionalized monomer or monomers, cross-linking monomer or monomers and polymerization initiator in a suitable solvent or without solvent. Suitable initiators include water and non-water soluble initiators, but are not limited to azobisisobutyronitrile (AIBN), 2,2-dimethoxy-2-phenyl acetophenone (DMPA), 1-hydroxycyclohexyl phenyl ketone (Irgacure.RTM. 184), 2,2-dimethoxy-1,2-diphenylethan-1-one (Irgacure 651), ammonium persulfate, iniferter such as tetraethylthiuram disulfide, or combinations thereof. The polymerization can be photo-initiated, thermally-initiated, redox-initiated or a combinations thereof.
"The functionalized monomer or monomers complex with the bio-template and copolymerize with cross-linking monomer or monomers to form a biomimetic recognitive polymeric hydrogel, such as described above. Functional or reactive monomers useful herein are those which possess chemical or thermodynamic compatibility with a desired bio-template. As used herein, the term functional monomer includes moieties or chemical compounds in which there is at least one double bond group that can be incorporated into a growing polymer chain by chemical reaction and one end that has functionality that will interact with the bio-template through one or more of electrostatic interactions, hydrogen bonding, hydrophobic interactions, coordination complexation, and Van der Waals forces. Functional monomers includes macromers, oligomers, and polymer chains with pendent functionality and which have the capability of being crosslinked to create the recognitive hydrogel. Crosslinking monomer includes chemicals with multiple double bond functionality that can be polymerized into a polymer network. Examples of functionalized monomers include, but are not limited to, 2-hydroxyethylmethacrylate (HEMA), Acrylic Acid (AA), Acrylamide (AM), N-vinyl 2-pyrrolidone (NVP), 1-vinyl-2-pyrrolidone (VP), methyl methacrylate (MMA), methacrylic acid (MAA), acetone acrylamide, 2-ethyl-2-(hydroxymethyl)-1,3-propanediol trimethacrylate, N-(1,1-dimethyl-3-oxobutyl)acrylamide, 2-ethyl-2-(hydroxymethyl)-1,3-propanediol trimethacrylate, 2,3-dihydroxypropyl methacrylate, allyl methacrylate, 3-[3,3,5,5,5-pentamethyl-1,1-bis[pentamethyldisiloxanyl)oxy]trisiloxanyl]- propyl methacrylate, 3-[3,3,3-trimethyl-1,1-bis(trimethylsiloxy)disiloxanyl]propyl methacrylate (TRIS), N-(1,1-dimethyl-3-oxybutyl)acrylamide, dimethyl itaconate, 2,2,2,-trifluoro-1-(trifluoromethyl)ethyl methacrylate, 2,2,2-trifluroethyl methacrylate, methacryloxypropylbis(trimethylsiloxy)methylsilane, methacryloxypropylpentamethyldisiloxane, (3-methacryloxy-2-hydroxypropyloxy)propylbis(trimethylsiloxy)methylsilane- , 4-t-butyl-2-hydroxycyclohexyl methacrylate, dimethylacrylamide and glycerol methacrylate.
"Once formed the biomimetic recognitive polymeric hydrogel can be formed into contact lenses or as described above the polymerization reaction forms the contact lenses.
"In accordance with further embodiments of the invention, functionalized monomers are synthesized or selected by identifying receptor sites or molecules associated with the target biological tissue to be treated by the drug or that are associated with metabolizing the drug. Then functionalized portions of the functionalized monomers are synthesized to chemically and/or structurally resemble or mimic the receptor sites or molecules that are associated with the biological mechanism of action of the drug. These functionalized monomers are then copolymerized with the cross-linking monomer or monomers used to form the hydrogel matrix, such as described above.
"After the drug has been depleted from the contact lenses through the eyes, the contact lenses can be re-loaded with the drug by soaking the contact lenses in the reconstituting drug solution. While the contact lense have been described in detail as being used to deliver antihistamines and other allergy drugs, ophthalmic drug delivery systems and methods of the present invention can be used to deliver any number of drugs through contact on the eye and/or systemically.
"Drugs that can be delivered by the system and method of the present invention include, but are not limited to, Anti-bacterials Anti-infectives and Anti-microbial Agents (genteelly referred to as antibiotics) such as Penicillins (including Aminopenicillins and/or penicillinas in conjunction with penicillinase inhibitor), Cephalosporins (and the closely related cephamycins and carbapenems), Fluoroquinolones, Tetracyclines, Macrolides, Aminoglycosides. Specific examples include, but are not limited to, erythromycin, bacitracin zinc, polymyxin, polymyxin B sulfates, neomycin, gentamycin, tobramycin, gramicidin, ciprofloxacin, trimethoprim, ofloxacin, levofloxacin, gatifloxacin, moxifloxacin, norfloxacin, sodium sulfacetamide, chloramphenicol, tetracycline, azithromycin, clarithyromycin, trimethoprim sulfate and bacitracin.
"The ophthalmic drug delivery system and method of the present invention can also be used to deliver Non-steroidal (NSAIDs) and Steroidal Anti-inflammatory Agents (genteelly referred to as anti-inflammatory agents) including both COX-1 and COX-2 inhibitors. Examples include, but are not limited to, corticosteroids, medrysone, prednisolone, prednisolone acetate, prednisolone sodium phosphate, fluormetholone, dexamethasone, dexamethasone sodium phosphate, betamethasone, fluoromethasone, antazoline, fluorometholone acetate, rimexolone, loteprednol etabonate, diclofenac (diclofenac sodium), ketorolac, ketorolac tromethamine, hydrocortisone, bromfenac, flurbiprofen, antazoline and xylometazoline.
"The ophthalmic drug delivery system and method of the present invention can also be used to deliver Anti-histamines, Mast cell stabilizers, and Anti-allergy Agents (generally referred to as anti-histamines). Examples include, but are not limited, cromolyn sodium, lodoxamide tromethamine, olopatadine HCl, nedocromil sodium, ketotifen fumurate, levocabastine HCL, azelastine HCL, pemirolast (pemirolast potassium), epinastine HCL, naphazoline HCL, emedastine, antazoline, pheniramine, sodium cromoglycate, N-acetyl-aspartyl glutamic acid and amlexanox.
"In yet further embodiments of the invention the ophthalmic drug delivery system and method are used to deliver Anti-viral Agents including, but not limited to, trifluridine and vidarabine; Anti-Cancer Therapeutics including, but not limited to, dexamethasone and 5-fluorouracil (5FU); Local Anesthetics including, but are not limited to, tetracaine, proparacaine HCL and benoxinate HCL; Cycloplegics and Mydriatics including, but not limited to, Atropine sulfate, phenylephrine HCL, Cyclopentolate HCL, scopolamine HBr, homatropine HBr, tropicamide and hydroxyamphetamine Hbr; Comfort Molecules or Molecules (generally referred as lubricating agents) to treat Keratoconjunctivitis Sicca (Dry Eye) including, but not limited to, Hyaluronic acid or hyaluronan (of varying Molecular Weight, MW), hydroxypropyl cellulose (of varying MW), gefarnate, hydroxyeicosatetranenoic acid (15-(S)-HETE), phospholipid-HETE derivatives, phoshoroylcholine or other polar lipids, carboxymethyl cellulose (of varying MW), polyethylene glycol (of varying MW), polyvinyl alcohol (of varying MW), rebamipide, pimecrolimus, ecabet sodium and hydrophilic polymers; Immuno-suppressive and Immuno-modulating Agents including, but not limited to, Cyclosporine, tacrolimus, anti-IgE and cytokine antagonists; and Anti-Glaucoma Agents including beta blockers, pilocarpine, direct-acting miotics, prostagladins, alpha adrenergic agonists, carbonic anhydrase inhibitors including, but not limited to betaxolol HCL, levobunolol HCL, metipranolol HCL, timolol maleate or hemihydrate, carteolol HCL, carbachol, pilocarpine HCL, latanoprost, bimatoprost, travoprost, brimonidine tartrate, apraclonidine HCL, brinzolamide and dorzolamide HCL; decongestants, vasodilaters vasoconstrictors including, but not limited to epinephrine and pseudoephedrine
BRIEF DESCRIPTION OF THE DRAWINGS
"FIG. 1 is a block diagram showing the steps for making contact lenses, in accordance with the embodiments of the invention.
"FIG. 2 illustrates the formation of a recognitive polymeric hydrogel, in accordance with the embodiments of the invention.
"FIG. 3 illustrates a block diagram outlining steps for making funtionalized monomer used in the synthesis of recognitive polymeric hydrogels, in accordance with the embodiments of the invention.
"FIGS. 4A-C illustrate examples of sets of molecules that match, resemble or mimic each other.
"FIGS. 5A-B are graphs that compare Ketotifen equilibrium isotherms in water for a recognitive polymeric hydrogel and a control hydrogel.
"FIG. 5C graphs drug loading for recognitive polymeric hydrogels of the present invention against control hydrogels to show the enhanced drug loading for recognitive polymeric hydrogels of the present invention.
"FIG. 6 shows a graph of drug release profiles for therapeutic contact lenses, in accordance with the embodiments of the invention.
"FIG. 7A-B show graphs of drug release profiles for recognitive polymeric hydrogels, in accordance with the embodiments of the invention"
For the URL and additional information on this patent, see: Byrne, Mark E.; Venkatesh, Siddarth. Contact Drug Delivery System. U.S. Patent Number 8349351, filed February 3, 2006, and issued January 8, 2013. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser'Sect1=PTO2&Sect2=HITOFF&p=83&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=4133&f=G&l=50&co1=AND&d=PTXT&s1=20130108.PD.&OS=ISD/20130108&RS=ISD/20130108
Keywords for this news article include: Drugs, Alkenes, Therapy, Alcohols, Hormones, Hydrogel, Peptides, Polyenes, Proteins, Chemistry, Acrylamides, Amino Acids, Biomimetics, Pilocarpine, Hydrocarbons, Legal Issues, Prednisolone, Dexamethasone, Methacrylates, Bioengineering, Topical Agents, Glucocorticoids, Carboxylic Acids, Sodium Phosphate, Auburn University.
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