Patent Application
20240307358
The contents of the electronic sequence listing (title: 702581.02185.xml; size: 1,744 bytes; date of creation: Jul. 8, 2022) is hereby incorporated by reference in its entirety.
Glaucoma is the leading cause of irreversible blindness, lacks a cure, and is currently estimated to affect 76 million people worldwide1. The prevalence of glaucoma continues to rise, with the number of individuals living with the disease projected to increase to ˜112 million people by 20401. The hallmark of glaucoma is elevated intraocular pressure ≥21 mm Hg)2, which progressively damages retinal ganglion cells3. Multiple lines of evidence demonstrate mechanical dysfunction in pressure-regulating tissues contribute to this increase in intraocular pressure4-13. In the eye, intraocular pressure is determined by the balance between the rate of aqueous humor production by the ciliary body, and the rate of aqueous humor outflow through tissues of the conventional14-17 and uveoscleral18-21 outflow pathways. Ocular hypertension results from increased resistance to aqueous humor outflow through the conventional outflow pathway22 that is positioned at the iridocorneal angle of the anterior segment and consists of the trabecular meshwork, Schlemm's canal, collector channels, intrascleral venous plexus and the aqueous veins. Decreased porosity4-8 of the Schlemm's canal endothelium contributes to the increase in outflow resistance in glaucoma, and these porosity changes arise from an increase in Schlemm's canal stiffness that impairs pore formation12. Most recently, it was demonstrated that the source of outflow resistance is localized to a region within 1 μm of the inner wall of the Schlemm's canal endothelial surface13.
Currently, first and second line glaucoma therapeutics decrease intraocular pressure by either (i) decreasing aqueous humor inflow, or (ii) driving a greater proportion of the aqueous humor outflow through the unconventional outflow pathway23. However, these treatments do not address the source of the increased outflow resistance that contributes to ocular hypertension23. Cell softening agents, such as actin depolymerizers and rho kinase inhibitors, improve aqueous humor outflow24-26 by directly addressing dysfunction in the conventional outflow pathway. Cell softening agents are approved for clinical use in the US (Netarsudil27-32) and abroad (Ripasudil33), but suffer from side effects, including conjunctival hyperemia, conjunctival hemorrhage, cornea verticillata, eye pruritus, reduced visual acuity, and blurred vision23. Targeted drug delivery vehicles may address these issues by directing cell softening agents to their site of action while minimizing adverse events arising from off-target effects.
Thus, there is a remaining need in the art for a system that can be used to selectively deliver cell softening agents to Schlemm's canal endothelial cells to treat glaucoma.
In a first aspect, the present invention provides systems for targeted delivery of a therapeutic agent to a cell, particularly a Schlemm's canal (SC) endothelial cell. The systems comprise: (a) a nanocarrier comprising a poly(ethylene glycol)-block-poly(propylene sulfide) (PEG-b-PPS) copolymer, (b) the therapeutic agent loaded in the nanocarrier; and (c) a targeting moiety that targets SC endothelial cells incorporated into the surface of the nanocarrier. The targeting moiety comprises: (i) a peptide that specifically binds to SC endothelial cells; (ii) a polyethylene glycol (PEG) spacer; and (iii) a hydrophobic anchor.
In a second aspect, the present invention provides pharmaceutical compositions comprising a system described herein and one or more pharmaceutically acceptable carriers.
In a third aspect, the present invention provides methods of reducing the intraocular pressure in a subject in need thereof. The methods comprise administering to the subject a therapeutically effective amount of a pharmaceutical composition comprising a system described herein.
In a fourth aspect, the present invention provides methods of treating glaucoma in a subject in need thereof. The methods comprise administering to the subject a therapeutically effective amount of a pharmaceutical composition comprising a system described herein.
The foregoing and other aspects and advantages of the invention will appear from the following description. In the description, reference is made to the accompanying drawings which form a part hereof, and in which there is shown by way of illustration a preferred embodiment of the invention. Such embodiment does not necessarily represent the full scope of the invention, however, and reference is made therefore to the claims and herein for interpreting the scope of the invention.
The present invention provides systems for targeted delivery of therapeutic agents to Schlemm's canal (SC) endothelial cells. Also provided are methods for using the systems to treat glaucoma or reduce intraocular pressure.
Primary open-angle glaucoma is associated with elevated intraocular pressure that damages the optic nerve and leads to gradual vision loss. One cause of this elevated intraocular pressure is increased stiffness of the SC endothelium in the aqueous humor outflow pathway. Several agents that relax this endothelium lower intraocular pressure in glaucoma patients and are approved for clinical use. However, these treatments have undesirable off-target effects and a lower than desired potency.
To address these issues, the present inventors developed a targeted self-assembled PEG-b-PPS micelle loaded with the cell softening agent latrunculin A (tLatA-MC). Their micelles are targeted to SC cells by a lipid-anchored targeting peptide that binds to the VEGFR3/FLT4 receptor, a lymphatic lineage marker that is highly expressed by SC cells relative to other ocular cells. In Example 1, the inventors demonstrate that increasing the targeting peptide surface density on the micelles increases their uptake by SC cells in vitro. They also demonstrate that tLatA-MC decrease SC cell stiffness in vitro and reduce intraocular pressure by 30-50% in a mouse model. In Example 2, the inventors confirm that VEGFR3/FLT4 receptors are a clinically relevant target that is present on SC cells from glaucoma patients and test several lipid-PEGx-peptide targeting constructs that differ in their number of PEG spacer units (x). They found that increasing the length of the PEG spacer in these constructs increased the accessibility of FLT4-binding peptides and enhanced nanocarrier uptake by SC cells. Further, they found that this enhanced targeting translates to intraocular pressure reductions in vivo that are sustained for a significantly longer time as compared to controls. Together, their results support the use of this cell-softening nanotherapy to selectively modulate the stiffness of SC cells for therapeutic reduction of intraocular pressure and treatment of glaucoma.
The present invention provides targeted delivery systems that can be utilized to deliver therapeutic agents to target cells in the eye of a subject to treat glaucoma. Specifically, in a first aspect, the present invention provides systems for targeted delivery of a therapeutic agent to a SC endothelial cell. The systems comprise: (a) a nanocarrier comprising a poly(ethylene glycol)-block-poly(propylene sulfide) (PEG-b-PPS) copolymer, (b) one or more therapeutic agent loaded in the nanocarrier; and (c) a targeting moiety that targets SC endothelial cells incorporated into the surface of the nanocarrier. The targeting moiety comprises: (i) a peptide that specifically binds to SC endothelial cells; (ii) a polyethylene glycol (PEG) spacer; and (iii) a hydrophobic anchor.
A “nanocarrier” is nanomaterial that comprises a complex or vesicular nanoarchitecture and is used as a transport module for a cargo, such as a drug. A nanocarrier may encapsulate the cargo or the cargo may be incorporated into the nanocarrier itself. Commonly used nanocarriers include polymeric nanoparticles, liposomes, polymeric micelles, carbon nanotubes, dendrimers, solid lipid nanoparticles, magnetic nanoparticles, and quantum dots. The nanocarriers of the present invention are used to deliver cargo to specific cells within a subject.
In preferred embodiments, the nanocarrier is a micelle. As used herein, the term “micelle” refers a nanocarrier having a PEG weight fraction above 0.38. Suitably, the micelle has a PEG weight fraction of about 0.38 to about 0.69. Micelle nanocarriers have a spherical morphology and are typically smaller (e.g., less than 50 nm) than polymersomes. Micelles have a hydrophobic/lipophilic core and a hydrophilic exterior. The hydrophobic core can be loaded with lipophilic cargo (e.g., a therapeutic agent). Micelles can be prepared using known methods, for example, those described by Karabin et al. (Nat Commun 9, 624, 2018), which is incorporated herein by reference.
In some embodiments, the nanocarrier has a diameter within the range of 100 nm to 300 nm, 110 nm to 290 nm, 120 nm to 280 nm, 130 nm to 270 nm, 140 nm to 260 nm, 150 nm to 250 nm, 160 nm to 280 nm, 170 nm to 270 nm, 180 nm to 260 nm, 190 nm to 250 nm, 200 nm to 240 nm, 210 nm to 230 nm, or 215 nm to 225 nm. In other embodiments, the nanocarrier has a diameter within the range of 5 nm to 60 nm, 8 nm to 57 nm, 11 nm to 54 nm, 14 nm to 51 nm, 17 nm to 48 nm, 20 nm to 45 nm, 23 nm to 42 nm, 26 nm to 39 nm, 29 nm to 36 nm, or 32 nm to 33 nm. In other embodiments, the nanocarrier has a diameter within the range of 10 nm to 20 nm, 11 nm to 19 nm, 12 nm to 18 nm, 13 nm to 17 nm, or 14 nm to 16 nm.
The nanocarrier used with the present invention comprises a poly(ethylene glycol)-block-poly(propylene sulfide) (PEG-b-PPS) copolymer. PEG-b-PPS nanocarrier systems offer several advantages, including rapid gram-scale fabrication, high stability, high loading efficiency for proteins (e.g., ˜70% for albumin) and small molecules (e.g., >90% for imiquimod derivatives), redox-sensitivity for intracellular delivery, and amenability to multimodal imaging. In the Examples the inventors utilized PEG45-b-PPS23. Thus, in some embodiments, the PEG-b-PPS copolymer is PEG45-b-PPS23. However, nearly any block lengths can be used. For example, in some embodiments, the PEG-b-PPS copolymer is PEGn-b-PPSm, wherein n can be any number ranging from 9 to 2300 and m can be any number ranging from 1 to 1000. Importantly, because polymer synthesis is inexact, there is a distribution of block lengths in any formulation. Thus, the numbers specified in these formulas merely represent the average block lengths.
PEG-b-PPS is an amphiphilic copolymer, i.e., a copolymer comprised of subunits or monomers that have different hydrophilic and hydrophobic characteristics. Typically, these subunits are present in groups of at least two and comprise blocks of a given character (e.g., a hydrophobic or hydrophilic block). Depending on the method of synthesis, these blocks may be comprised entirely of the same monomer or contain different monomer units dispersed throughout the block. These blocks can be arranged into a series of two blocks (diblock), three blocks (triblock), or more, forming the backbone of a block copolymer. Block units making up the copolymer can occur in regular intervals, or they can occur randomly. The ratio of hydrophobic to hydrophilic blocks in the copolymer is selected to achieve suitable aggregation for the desired architecture. PEG-b-PPS nanocarriers can be prepared via known methods. See, e.g., Du et al. (Nat Commun 29;11(1):48962019, 2020), Du et al. (J Control Release 282:90-100, 2018), and Yi et al. (ACS Nano 10(12):11290-11303, 2016) each of which are incorporated herein by reference in their entirety.
The PEG-b-PPS copolymer used in the systems of the present invention may also include chemical modifications or end caps including, but not limited to, thiol, benzyl, pyridyl disulfide, phthalimide, vinyl sulfone, aldehyde, acrylate, maleimide, and n-hydroxysuccinimide groups. The chemical modifications may add a charged residue to the polymer or may be used to otherwise functionalize the polymer. Chemical moieties may also be covalently attached or grafted to the copolymer backbone. The grafted side chains may be added at regular intervals along the polymer backbone or randomly.
The nanocarriers of the present invention are “loaded” with a therapeutic agent, meaning that either (1) a therapeutic agent is incorporated into the nanocarrier itself, or (2), a therapeutic agent is encapsulated by the nanoparticle. In the Examples, the inventors encapsulated a therapeutic agent via cosolvent evaporation, as described by Stack et al. (J Biomed Mater Res A 106 (7), 1771-1779, 2018), which is hereby incorporated by reference in its entirety. Other common methods for loading a nanocarrier with a therapeutic agent include, without limitaiton, nanoprecipitation, flash nanoprecipitation, thin film hydration, and microfluidics.
As used herein, the term “therapeutic agent” refers to a molecule or drug that can be used to treat a disease or condition. In preferred embodiments, the therapeutic agent is an agent that can be used to treat glaucoma or high intraocular pressure. In some embodiments, the therapeutic agent is a cell softening agent. Suitable cell softening agents include, without limitation, actin depolymerizers (e.g., latrunculin A), Rho kinase inhibitors (e.g., Rhopressa, Glanatec), and nitric oxide donating compounds (e.g., Vyzulta). In other embodiments, the therapeutic agent is a gene therapy agent (e.g., a viral vector, a CRISPR reagent), anti-inflammatory agent (e.g., rapamycin, celastrol, vitamin D/calcitriol), anti-cancer agent (e.g., doxorubicin, camptothecin), or diagnostic agent (e.g., fluorescein, BODIPY, ethyl eosin, pheophorbide A). In the Examples, the inventors use their targeted delivery systems to deliver the drug latrunculin A to SC endothelial cells in the eyes of mice. Thus, in preferred embodiments, the therapeutic agent is latrunculin A. Latrunculin is a well-known transient actin depolymerizing agent that mechanically softens cells and has been shown to significantly reduce intraocular pressure in animal studies.
“Loading efficiency” is defined as the ratio of the amount of therapeutic agent in the assembled nanocarrier to the total amount of therapeutic agent applied during formulation of the nanocarrier. In some embodiments, the nanocarrier has a loading efficiency of the therapeutic agent of from 0.01% to 100%. In some embodiments, the nanocarrier has a loading efficiency of the therapeutic agent of from 0.1% to 98%, from 1% to 95%, from 5% to 90%, from 10% to 85%, from 15% to 80%, from 20% to 75%, from 25% to 70%, from 30% to 65%, from 35% to 60%, from 40% to 55%, or from 45% to 50%. In some embodiments, the loading efficiency is from 55% to 65%, from 56% to 64%, from 57% to 63%, from 58% to 62%, or from 59% to 61%.
The systems of the present invention are used for targeted delivery of a therapeutic agent. As used herein, the term “targeted delivery” refers to the fact that the systems preferentially deliver the therapeutic agent to SC endothelial cells as compared to other ocular cells. The inventors have demonstrated that their nanocarriers are internalized by SC endothelial cells in significantly greater numbers than by human umbilical vein endothelial cells (see
The systems of the present invention target therapeutic agents to SC endothelial cells. Schlemm's canal (SC) is a unique, complex vascular structure responsible for maintaining fluid homeostasis within the anterior segment of the eye by draining the flow of aqueous humor. In glaucoma, the normal outflow of aqueous humor into SC is progressively hindered, leading to a gradual increase in outflow resistance, which gradually results in elevated intraocular pressure. An increase in SC stiffness and decreased porosity of the SC endothelium contribute to this increase in outflow resistance. Thus, targeting cell softening agents to SC endothelial cells is a promising means to treat glaucoma.
In the systems of the present invention, targeted delivery to SC endothelial cells is achieved by including a targeting moiety on the surface of the nanocarrier. A “targeting moiety that targets SC endothelial cells” is any moiety that preferentially binds to SC endothelial cells as compared to other ocular cells. In the Examples, the inventors used a targeting moiety that comprises (i) a peptide that specifically binds to SC endothelial cells; (ii) a polyethylene glycol (PEG) spacer; and (iii) a hydrophobic anchor.
As used herein, the term “peptide” refers to short polymer of amino acids linked together by peptide bonds. Peptides are typically shorter than other amino acid polymers (e.g., proteins, polypeptides), and are typically about 50 amino acids or less in length. A peptide may comprise natural amino acids, non-natural amino acids, amino acid analogs, and/or modified amino acids. A peptide may comprise a portion of a naturally occurring protein or may be artificial.
The peptides used in the systems of the present invention specifically bind to SC endothelial cells, meaning that they bind to a moiety that is preferentially found on the surface of SC endothelial cells as compared to other ocular cells. In the Examples, the inventors utilized the targeting peptide of SEQ ID NO:1 (WHWLPNLRHYAS), which binds the FLT4/VEGFR3 receptor. The VEGFR3/FLT4 receptor is a lymphatic lineage marker that is highly expressed by SC endothelial cells relative to other ocular cells. Thus, in some embodiments, the peptide binds to a FLT4/VEGFR3 receptor. In specific embodiments, the peptide has a sequence of SEQ ID NO:1 or a sequence having 95% sequence similarity to SEQ ID NO:1. In some embodiments, the peptide has a sequence having 97% sequence similarity to SEQ ID NO:1. In some embodiments, the peptide has a sequence having 99% sequence similarity to SEQ ID NO:1. Other peptides that can bind to the FLT4/VEGFR3 receptor are also contemplated.
“Percentage of sequence similarity”' is determined by comparing two optimally aligned sequences over a comparison window. The aligned sequences may comprise additions or deletions (i.e., gaps) relative to each other for optimal alignment. The percentage is calculated by determining the number of matched positions at which an identical nucleic acid base or amino acid residue occurs in both sequences, dividing the number of matched positions by the total number of positions in the window of comparison and multiplying the result by 100 to yield the percentage of sequence identity. Protein and nucleic acid sequence identities are evaluated using the Basic Local Alignment Search Tool (“BLAST”), which is well known in the art (Proc. Natl. Acad. Sci. USA (1990) 87: 2267-2268; Nucl. Acids Res. (1997) 25: 3389-3402). The BLAST programs identify homologous sequences by identifying similar segments, which are referred to herein as “high-scoring segment pairs”, between a query amino acid or nucleic acid sequence and a test sequence which is preferably obtained from a protein or nucleic acid sequence database. Preferably, the statistical significance of a high-scoring segment pair is evaluated using the statistical significance formula Proc. Natl. Acad. Sci. USA (1990) 87: 2267-2268), the disclosure of which is incorporated by reference in its entirety. The BLAST programs can be used with the default parameters or with modified parameters provided by the user.
The “incorporation efficiency” of the targeting moiety is defined as the ratio of the amount of targeting moiety in the assembled nanocarrier to the total amount of targeting moiety applied during formulation of the nanocarriers. In some embodiments, the nanocarrier has an incorporation efficiency of the targeting moiety of greater than 90%. In some embodiments, the incorporation efficiency of the targeting moiety is greater than 95%, greater than 97%, greater than 98%, or greater than 99%.
A “molar ratio” is the ratio between the amounts (in moles) of any two substances involved in a chemical reaction. In some embodiments of the present invention, the molar ratio of the targeting moiety to the PEG-b-PPS copolymer is from 1% to 5%. In some embodiments, the molar ratio of the targeting moiety to the PEG-b-PPS copolymer is 1%. In some embodiments, the molar ratio of the targeting moiety to the PEG-b-PPS copolymer is 3%. In some embodiments, the molar ratio of the targeting moiety to the PEG-b-PPS copolymer is 5%.
As used herein, a “polyethylene glycol (PEG) spacer” is a formulation of PEG that is used to link the peptide portion of the targeting moiety to the hydrophobic anchor. PEG is a polyether compound derived from petroleum. It is composed of repeating ethylene glycol units, i.e., —(O—CH2—CH2)—. In some embodiments, the PEG spacer has a formula “—HN—C(O)—CH2—(O—CH2—CH2)n—NH—C(O)—,” wherein one end is attached to the peptide and the other end is attached to the hydrophobic anchor. In some embodiments, the PEG spacer has from 6 to 48 units (i.e., the “n” in the formula is an integer of 6-48). In Example 2, the inventors compared the ability of targeting moieties comprising PEG spacers with 6, 24, and 48 units to increase nanocarrier uptake by SC cells. They found that the PEG spacer with 48 units (i.e., PG48) provides increased targeting peptide accessibility as compared to the shorter PEG spacers and produces the greatest enhancement of nanocarrier uptake (see
In the systems of the present invention, the targeting moiety is incorporated into the surface of the nanocarrier via a hydrophobic anchor. A “hydrophobic anchor” is a hydrophobic molecule that is attached to a moiety that one wishes to display on a membrane such that embedment of the hydrophobic molecule into the membrane anchors the moiety to the membrane. Suitable hydrophobic molecules for use as a hydrophobic anchor include, without limitation, lipids, cholesterol, hydrophobic polymers, and other lipophilic molecules that have a partition coefficient greater than 2. One example is a carboxylic acid hydrophobic anchor.In the Examples, the inventors included palmitoleic acid in their targeting moiety to facilitate insertion into the nanocarrier surface. Palmitoleic acid is an omega-7 monounsaturated fatty acid (16:1n-7) with the formula CH3(CH2)5CH=CH(CH2)7COOH. Thus, in some embodiments, the hydrophobic anchor is palmitoleic acid.
The systems disclosed herein may be incorporated into pharmaceutical compositions. Thus, in a second aspect, the present invention provides pharmaceutical compositions comprising a system described herein and one or more pharmaceutically acceptable carriers. The pharmaceutical compositions may be used in methods of treating glaucoma or reducing the intraocular pressure in a subject in need thereof.
The term “pharmaceutically acceptable carrier” refers to any carrier, diluent, or excipient that is compatible with the other ingredients of a composition and is not deleterious to the recipient. Pharmaceutically acceptable carriers are known in the art and include, but are not limited to, diluents (e.g., Tris-HCl, acetate, phosphate), preservatives (e.g., thimerosal, benzyl alcohol, parabens), solubilizing agents (e.g., glycerol, polyethylene glycerol), emulsifiers, liposomes, nanoparticles, and adjuvants. Pharmaceutically acceptable carriers may be aqueous or non-aqueous solutions, suspensions, or emulsions. Examples of nonaqueous solvents are propylene glycol, polyethylene glycol, vegetable oils (e.g., olive oil), and injectable organic esters (e.g., ethyl oleate). Aqueous carriers include isotonic solutions, alcoholic/aqueous solutions, emulsions, and suspensions, including saline and buffered media.
The pharmaceutical compositions of the present invention may further include additives such as albumin or gelatin to prevent absorption to surfaces, detergents (e.g., Tween 20, Tween 80, Pluronic F68, bile acid salts), antioxidants (e.g., ascorbic acid, sodium metabisulfite), bulking substances or tonicity modifiers (e.g., lactose, mannitol).
The pharmaceutical compositions may be formulated into dosage forms according to standard practices in the field of pharmaceutical preparations. See, e.g., Alphonso Gennaro, ed., Remington's Pharmaceutical Sciences, 18th Ed., (1990) Mack Publishing Co., Easton, Pa.
In a third aspect, the present invention provides methods of reducing the intraocular pressure in a subject in need thereof. The methods comprise administering to the subject a therapeutically effective amount of a pharmaceutical composition comprising a system described herein.
As used herein, the term “intraocular pressure” refers to the fluid pressure inside the eye. Intraocular pressure is typically determined by tonometry.
The present methods reduce intraocular pressure in a subject, meaning that the intraocular pressure in the eyes of the subject is lower after the method has been performed than it was before the method was performed. In some embodiments, the intraocular pressure is reduced by at least 35% after 24 hours from the administration. In some embodiments, the intraocular pressure is reduced by at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, or at least 95% after 24 hours from the administration.
In a fourth aspect, the present invention provides methods of treating glaucoma in a subject in need thereof. The methods comprise administering to the subject a therapeutically effective amount of a pharmaceutical composition comprising a system described herein.
As used herein, the term “glaucoma” refers to a neurodegenerative disease characterized by damage to the optic nerve, usually due to excessively high intraocular pressure. Glaucoma is the leading cause of irreversible blindness.
As used herein, “treating” describes the management and care of a subject for the purpose of combating glaucoma. Treating includes the administration of a system or pharmaceutical composition described herein to prevent the onset of the symptoms or complications, to alleviate the symptoms or complications, to prevent the progression of symptoms or complications, or to eliminate the glaucoma. For example, treatment with the systems of the present invention may result in a stabilization of intraocular pressure, a reduction in intraocular pressure, or a reduction in one or more other symptom or condition associated with glaucoma (e.g., blurred vision, halos around lights, eye redness, eye pain, headaches, loss of vision, patchy blind spots in your side or central vision, tunnel vision, among others).
Accordingly, as used herein, the term “therapeutically effective amount” refers to an amount sufficient to achieve one or more of the outcomes listed above. For any active agent, a therapeutically effective amount can be estimated initially in cell culture assays or in as animal model. An appropriate amount of the system or pharmaceutical composition to be administered is dependent on a variety of factors, including the severity of the condition, the body weight and age of the subject, the frequency of administration, the duration of treatment, and the like. The disclosed compositions may be administered at any suitable dosage, frequency, and for any suitable duration necessary to achieve the desired therapeutic effect, i.e., to treat glaucoma or reduce intraocular pressure.
In the Examples, the inventors demonstrated that nanocarriers comprising the cell softening therapeutic agent latrunculin A can be used to reduce intraocular pressure in a mouse model of glaucoma. Thus, in some embodiments, the therapeutic agent is latrunculin A. In some embodiments, the concentration of latrunculin A in the pharmaceutical composition is 0.05 μM-20 μM. In some embodiments, the concentration of latrunculin A in the pharmaceutical composition is 0.1 μM-19 μM, 0.3 μM-18 μM, 0.5 μM-17 μM, 1 μM-15 μM, 2 μM-13 μM, 4 μM-11 μM, 6 μM-9 μM, or 7 μM-8 μM.
As used herein, the term “administering” refers to the introduction of a substance into a subject's body. Suitable modes of administration include, without limitation, ocular administration, topical administration, and extended release from a depot placed in the anterior chamber or in the vitreous chamber of the eye, among others.
The “subject” to which the methods are applied may be a mammal or a non-mammalian animal, such as a bird. Suitable mammals include, but are not limited to, humans, cows, horses, sheep, pigs, goats, rabbits, dogs, cats, bats, mice, and rats. In certain embodiments, the methods may be performed on lab animals (e.g., mice and rats) for research purposes. In other embodiments, the methods are used to treat commercially important farm animals (e.g., cows, horses, pigs, rabbits, goats, sheep, and chickens) or companion animals (e.g., cats and dogs). In a preferred embodiment, the subject is a human. In some embodiments, the subject is in need of reduction of intraocular pressure or is having one or more symptom of glaucoma.
The use herein of the terms “including,” “comprising,” or “having,” and variations thereof, is meant to encompass the elements listed thereafter and equivalents thereof as well as additional elements. Embodiments recited as “including,” “comprising” or “having” certain elements are also contemplated as “consisting essentially of” and “consisting of” those certain elements.
As used herein, “about” means within 5-10% of a stated concentration range or within 5-10% of a stated number.
It should be apparent to those skilled in the art that many additional modifications beside those already described are possible without departing from the inventive concepts. In interpreting this disclosure, all terms should be interpreted in the broadest possible manner consistent with the context. Variations of the term “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, so the referenced elements, components, or steps may be combined with other elements, components, or steps that are not expressly referenced. Embodiments referenced as “comprising” certain elements are also contemplated as “consisting essentially of” and “consisting of” those elements. The term “consisting essentially of” and “consisting of” should be interpreted in line with the MPEP and relevant Federal Circuit's interpretation. The transitional phrase “consisting essentially of” limits the scope of a claim to the specified materials or steps “and those that do not materially affect the basic and novel characteristic(s)” of the claimed invention. “Consisting of” is a closed term that excludes any element, step or ingredient not specified in the claim. The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with “and/or” should be construed in the same fashion, i.e., “one or more” of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the “and/or” clause, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, a reference to “A and/or B”, when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A only (optionally including elements other than B); in another embodiment, to B only (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.
As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and/or” as defined above. For example, when separating items in a list, “or” or “and/or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of”or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e., “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of”
The present invention has been described in terms of one or more preferred embodiments, and it should be appreciated that many equivalents, alternatives, variations, and modifications, aside from those expressly stated, are possible and within the scope of the invention.
The following Examples are offered for illustrative purposes only and are not intended to limit the scope of the present invention in any way. Indeed, various modifications of the invention in addition to those shown and described herein will become apparent to those skilled in the art from the foregoing description and the following examples and fall within the scope of the appended claims.
In view of the adverse off-target effects of glaucoma drugs, we sought to develop and optimize a nanocarrier platform employing a targeting moiety for selective intracellular delivery to Schlemm's canal (SC) cells as a glaucoma treatment strategy. Nanomaterials have been shown to be advantageous drug delivery platforms that are well-suited for targeting specific cells and tissues[8,9]. Enhanced targeting and cell specificity allows for less off-target drug delivery and a lower potential for side effects[10]. Targeted nanomaterials have been shown to lower the therapeutic threshold concentration for certain drugs after encapsulation as well as reduce cytotoxicity and other unwanted effects in many cell types including SC cells[11-13].
Latrunculin is a well-known transient actin depolymerizing agent that mechanically softens cells[14] and has been shown to significantly reduce IOP in animal studies[5,15]. A phase I clinical trial, at concentrations previously found to be effective in primates, found a modest reduction of IOP with side effects that included mild redness, irritation, and a transient increase in central corneal thickness[16]. We speculated that targeted delivery of latrunculin to SC cells would provide increased bioavailability while minimizing side effects. Self-assembled poly (ethylene glycol)-b-poly(propylene sulfide) (PEG-b-PPS) block co-polymers have been used as versatile nanocarriers in a wide range of applications[12,17-23]. Depending on the morphology employed, PEG-b-PPS nanocarriers can retain both hydrophobic and hydrophilic payloads respectively in their cores or aqueous interior compartments[20,21,24-26] and are highly customizable through control of charge, size, and targeting moieties on their surfaces[8,27]. Nanomaterials provide a wide range of options for sustained drug and gene delivery[19,22,28], and the development of SC targeted nanocarriers will thus provide versatile options for the long term delivery of glaucoma therapeutics following a single intracameral injection.
In the following Example, we describe the design and development of a PEG-b-PPS controlled delivery system for delivery of latrunculin A to SC cells. SC cells express the lymphatic lineage receptor VEGFR3/FLT4 at moderately high levels as compared with blood vascular cells, which lack this receptor[29]. Thus, PEG-b-PPS micellar nanocarriers decorated with a FLT4-specific targeting peptide and loaded with latrunculin A were generated. The targeting and functional efficacy of this formulation was assessed in vitro in SC cells using uptake assays and atomic force microscopy (AFM). In vivo efficacy was evaluated using a C57BL/6J mouse model by measuring changes in IOP over multiple days after administering targeted nanocarriers intracamerally. Results show that the targeted nanocarriers were highly selective for SC cells in comparison with blood vascular cells, and that targeted latrunculin-loaded micelles (tLatA-MC) significantly lowered IOP in mouse eyes, as compared to control eyes treated with non-targeted latrunculin-loaded micelles (ntLatA-MC).
Peptide lipid constructs can be attached to PEG-b-PPS micelles for intracellular delivery to SC endothelial cells with high efficiency and do not influence micelle structure. VEGFR3/FLT4 is a lymphatic marker that is expressed at the surface of SC endothelial cells[30,31]. We hypothesized that displaying a ligand for this receptor at the micelle surface would enhance micelle uptake selectively by SC cells as compared with other ocular cells, particularly blood vascular cells. We examined expression of FLT4 in human SC cells and human umbilical vein endothelial cells (HUVEC; used as a generic blood vascular cell control). Schlemm's cells were isolated as previously described[32] and HUVEC were obtained from Lonza (Basel, Switzerland). Cells were prepared as described in the methods and labeled with anti-FLT4 antibody. FLT4 expression was evaluated using laser scanning confocal microscopy, widefield fluorescence microscopy, and flow cytometry. As expected, FLT4 was present on the SC cell surface at significantly higher abundance than the HUVEC cell surface (
Targeted micelles were developed that incorporated an FLT4-targeting ligand (tBL-MC, and tLatA-MC; (BL=blank, t=peptide target) (
We next evaluated the tLatA-MC formulations for peptide incorporation using fluorescence spectroscopy. The tryptophan residues on the FLT4 targeting peptide grant the construct an intrinsic fluorescence that can be measured against a standard curve to determine peptide concentrations within the micelles (
tLatA-MC demonstrated significantly greater uptake by SC cells and cell softening compared to non-targeted micelles in vitro. To evaluate the targeting efficacy of the FLT4 binding peptide, we examined the uptake of micelles. SC cells and HUVEC were incubated with 0.5 mg/mL Alexa 555 labeled micelles incorporated with various molar ratios (1%, 3%, 5%) of peptide to micelle for 1 hour at 37° C. Afterwards, cells were washed, harvested, and evaluated for particle uptake and cytotoxicity by flow cytometry. Flow cytometric analysis demonstrated that 5% peptide incorporation into targeted blank micelles (tBL-MC) modestly increased the number of particles internalized by SC cells as compared to ntBL-MC and 1% tBL-MC (
When latrunculin A was loaded into micelles, the uptake by both cell types was altered. The decrease in uptake of targeted micelles (tBL-MC) by HUVECs, as compared with blank micelles (BL-MC), is no longer observed with latrunculin-loaded targeted micelles (tLatA-MC) (
To evaluate the functional effects of tLatA-MC on cultured human SC cells, we used atomic force microscopy (AFM) to assess changes in cell stiffness and morphology (
tLatA-MC reduces IOP in C57B16 mice. We next evaluated the efficacy of our tLatA-MC formulation in vivo. Two different in vivo trials were performed (
We further evaluated the in vivo efficacy of tLatA-MC in a second trial designed to include non-targeted latrunculin A-loaded micelles, ntLatA-MC (
In collaboration with Duke University, our group repeated our prior delivery of nanocarriers to the eyes of live mice with newly prepared micelle formulations to confirm the performance of targeted micelles in lowering intraocular pressure in mice. This study included the following treatment groups, which we administered to the eyes of mice: (i) latrunculin A-loaded micelles that displayed the original targeting peptide construct (“targeted latrunculin A micelles”), (ii) latrunculin A-loaded micelles that do not display peptide (“latrunculin A micelles”), and (iii) micelles that do not encapsulate latrunculin A and do not display the original peptide construct (“Blank MCs”). The significant results were as follows. The targeted latrunculin A micelles reduced intraocular pressure by 5.6±2.0 mmHg after 1 day compared to Blank micelles, and by 5.4±1.9 mmHg compared to latrunculin A micelles. The latrunculin A micelles and Blank micelles were not significantly different. These differences were statistically significant (*p<0.05). Collectively, these results demonstrate that the targeted latrunculin A micelles significantly reduce IOP in mice after 24 h, and this effect is dependent on the presence of the targeting peptide. At 30 h, the targeted latrunculin A micelles reduced 4.0±1.6 mmHg compared to the blank MC control. This result was significant (*p<0.05). At this 30 h timepoint, no other comparisons between treatment groups were statistically significant.
The lack of effect of ntLatA-MC alone was unexpected but could be due to increased uptake in trabecular meshwork cells of ntLatA-MC that leads to a lower than threshold dose of LatA to be delivered to SC cells. Additionally, SC cells are only moderately phagocytic[11], and the targeting peptide may be required to reach intracellular threshold concentrations necessary for therapeutic effect.
In conclusion, we have successfully developed a targeted PEG-b-PPS nanocarrier system loaded with actin depolymerizing/cell softening agent latrunculin A (tLatA-MC). These micellar nanocarriers were designed with an FLT4-binding peptide to target SC cells in the eye. This system can load a variety of hydrophobic drug payloads and targeting moieties. Interestingly, the tBL-MC showed a decrease in HUVEC uptake although tLatA-MC did not. This is to our knowledge a previously unreported phenomenon and suggest that we not only can target the SC cells, but greatly reduce non-specific binding. Further work also must be undertaken to determine if this phenomenon is limited to HUVECs.
The data indicating tLatA-MC reduced IOP in two sets of mouse trials demonstrates the potential clinical significance of this delivery platform. Further studies will be necessary to demonstrate that use of these targeted nanocarriers reduce off-target effects, as our data suggests, and to investigate use of this delivery platform in other settings, particularly those requiring targeted delivery of hydrophobic drugs.
Synthesis of PEG-b-PPS block co-polymer. Nanocarriers were fabricated from a PEG-b-PPS copolymer which self assembles into various morphologies in a controllable way based on the molecular weight ratio of the hydrophilic PEG block to the hydrophobic PPS block. Block copolymers, PEG45-b-PPS23, were synthesized as previously described[17-18]. Briefly, PEG thioacetate was deprotected using sodium methoxide and subsequently used to initiate anionic ring opening polymerization of propylene sulfide. The reaction was allowed to run to completion and the resulting poly-propylene sulfide was end-capped using bromo benzene. The resulting polymer was precipitated twice in methanol for purification and then its structure was evaluated using 1 H NMR (CDCL3) and gel permeation chromatography (Thermo Fisher Scientific) using a Waters Styragel column with refractive index and UV-Vis detectors in a tetrahydrofuran mobile phase.
Synthesis of FLT4 targeting peptide constructs. FLT4 peptide (WHWLPNLRHYAS (SEQ ID NO: 1)) was synthesized on a 0.5 mmol scale on Wang Resin (EMD Millipore) using standard Fmoc solid phase peptide synthesis (SPPS) and FastMoc chemistry (Applied Biosystems). Resins were swelled in N-methyl-2-pyrrolidinon (NMP) for 2 hours and Fmoc moieties were deprotected using 20% piperidine in NMP for 20 minutes. Fmoc protected amino acids (2.5-3.5 eq.) were added stepwise with 2-(1H-Benzotriazol-1-ly)-1,1,3,3,-tetramthyluronium hexafluorophosphate (HBTU, 2.5-3.5 eq) and N, N-diisopropylethyleamine (DIPEA, 4 eq) as a solvent by shaking for 3 hours at room temperature. After the final fmoc peptide was added and deprotected, Fmoc protected PEG spacer (Fmoc-PEG6-COOH, 2 eq) was added to couple with the free peptide amine group (HBTU, 2.5eq, DIPEA, 4 eq) and allowed to shake for 4 hours. The PEG spacer was then deprotected using 20% piperidine and coupled with 3 eq of palmitoleic acid (HBTU, 2.5 eq, DIPEA, 4eq) and allowed to react overnight while shaking. Coupling and deprotection of each amino acid and PEG spacer was verified by Ninhydrin test (Sigma). Deprotection of side chains and cleavage from the resin was done using Fmoc cleavage cocktail TFA/phenol/water/triisopropylsilane (TIPS) (88/5/5/2) twice for 2 hours each. Unpurified products were isolated by double precipitation in ice cold diethyl ether and subsequently purified at the Simpson Querrey Institute (SQI) peptide synthesis core by using RP-HPLC (Water-acetonitrile gradient, C18 column). Purified peptide construct was mixed with α-cyano-4-hydroxycinnamic acid (CHCA) prepared with acetonitrile/water (50:50, v/v) with 0.1% trifluoroacetic acid and molecular weight was determined by MALDI-TOF on a Bruker Autoflex III Smartbeam Spectometer (Bruker).
Assembly and loading of PEG-b-PPS micelles. Micelles were assembled from PEG-b-PPS block copolymer by a previously described cosolvent method[11-35]. PEG45-b-PP S23 block copolymer, 10 μg latrunculin A (Cayman Chemical), and 6 μL DiI (Thermo Fisher Scientific) were dissolved in 1 mL dichloromethane (DCM). The resulting DCM solution was added dropwise to a scintillation vial containing 1 mL sterile PBS stirred vigorously. DCM was allowed to evaporate for 2 hours. The resulting micelle suspensions were then prepared for addition of peptide or set aside for later purification. To achieve precise control of the peptide density on the surface of the micelle, FLT4/PEG/Palmitoleic acid constructs were added to already formed micelles at the desired molar ratio (1%, 3%, 5%). The appropriate amount of peptide construct was dissolved in DMSO, added to the micelles, and allowed to shake overnight. Resulting micelle formulations were then purified by gravity column chromatography using a Sephadex LH-20 column (Sigma-Aldrich) with a PBS mobile phase. Gravity column filtered micelles were then further purified and concentrated using 10 k MWCO Zebaspin desalting columns (Thermo Fisher).
Size and charge of micelle formulations. Size distribution, and polydispersity index (PDI) of the micelle formulations were analyzed by Zetasizer Nano (Malvern Instruments) using a 4mW He-Ne 633 nm laser at 1 mg/mL in PBS. PDI was determined using a two-parameter fit to the DLS correlation data. The number average nanoparticle diameter was calculated in MATLAB (MathWorks; version R2018a).
Scanning transmission electron microscopy (STEM). Micelle samples were diluted in ultrapure water to a polymer concentration of 5 mg/mL. Carbon-coated copper grids (400 mesh; Electron Microscopy Sciences) were glow discharged (25 W, 10 s) and the micelle formulation was applied subsequently. Micelles were negatively stained using uranyl formate (1.0% prepared in ultrapure water; pH adjusted to 4.5 via addition of 10 N KOH). In this procedure, sample-loaded grids are blotted with Whatman filter paper to remove excess sample and are subjected to two passages through water followed by two passages through 1.0% UF stain. This procedure results in ˜0.5 μl stain left on the grid, with an activity of 2.55×10−5 μKi/grid. Electron micrographs of negatively stained specimens were acquired on a Hitachi HD-2300 Dual EDS Cryo STEM operating at 200 kV (field emission gun) and Gatan DigitalMicrograph Software. Unless otherwise indicated, images were obtained at a magnification of 200,000×. All .dm3 files were processed in ImageJ software with basic, routine adjustment for figure preparation (overall brightness level and gamma adjustment).
Small angle x-ray scattering (SAXS) using synchrotron radiation. SAXS was performed at the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) beamline at the Advanced Photon Source at Argonne National Laboratory (Argonne, IL, USA), using a 7.5 m sample-to-detector distance, 10 keV (λ=1.24 Å) collimated x-rays, and an exposure time of 3 s. Scattering was analyzed in the q-range of 0.001-0.5 Å−1, calibrated using silver behenate diffraction patterns. Eq. 1 defines the momentum transfer vector (q), where θ is the scattering angle:
The obtained data was reduced in PRIMUS software (version 2.8.3.) and model fitting was performed using SasView (version 5.0) software. A core shell sphere model was fit to micelle scattering profiles:
Where F is the structure factor, q is the momentum transfer vector (Eq. 1), Vs is the particle volume (Å3), Vc is the particle core volume (Å3), ρc is the core scattering length density (10−6 Å−2), ρs is the shell scattering length density (10−6 Å−2), ρsolv is the solvent scattering length density (10−6 Å−2), rc is the core radius (Å). The shell thickness (rt; in Å) is determined from the radius of the total particle (rs; in Å) from Eq. 3:
Prior to performing more extensive parameter fitting procedures, the number-average micelle diameter determined by DLS was used to select initial core radius and shell thickness parameter values. Optimal model parameters were iteratively fit using the Levenberg-Marquardt algorithm in a chi square (X2) minimization procedure. For core shell sphere models, a good model fit is indicated by X2<1.0. For all models presented in this study, X2<0.1 was obtained for the final model fit.
Drug loading characterization. Latrunculin A encapsulation efficiency was determined using a previously described method[11] in which 100 μL of concentrated and purified micelles were frozen at −80° C. and then lyophilized overnight. Latrunculin A was then extracted from the resulting lyophilized cake using methanol. After 1 h of extraction, the resulting suspension was centrifuged for 5 min at 4000×g and the supernatant latrunculin A content was evaluated by high performance liquid chromatography (HPLC). A static Methanol:Water (95:5) mobile phase was used on an Agilent C18 XDB-Eclipse column with absorption (235 nm) used to evaluate latrunculin A concentration. Standard curves were generated through serial dilution of latrunculin A with each of the resulting latrunculin A standards undergoing the same lyophilization and methanol extraction procedure described above.
Quantification of embedded targeting peptide. Peptide incorporation into the micelle was determined using fluorescence spectroscopy (SpectraMax M3; Molecular Devices). 100 μL of purified and concentrated micelles containing peptide were added to a black clear bottom 96 well plate in triplicate and tryptophan fluorescence at 270/350 nm (Ex/Em) was measured and compared to a standard curve to determine peptide incorporation. Blank micelle baseline was subtracted from raw values obtained for micelles displaying peptide. A standard curve was generated through serial dilution of DMSO-dissolved peptide in PBS of a paired peptide solution for each specific micelle batch. The final standard curve was prepared by background subtracting PBS.
Cell culture. Normal SC cells (SC71) were obtained from the lab of Dr. Dan Stamer. The protocol for extraction and isolation of these cells is described in detail elsewhere[32]. Extracted cells were shipped overnight in T25 cell culture flasks filled with low glucose DMEM (Life Technologies)+10% fetal bovine serum (Atlanta Biologicals) and 1% penicillin/streptomycin (Life technologies). Immediately upon arrival, cells media was refreshed and cells were stored at 37° C. and 5% CO2 until 80% confluent. Cells were passaged using a standard trypsinization procedure and were split at a 1:3 ratio when 80% confluent. SC cells were used at passage 4 and 5 in all experiments. Human Umbilical Vein Endothelial Cells (HUVEC) were cultured in Endothelial Growth Media (Lonza). Cells were passaged at a 1:3 ratio using trypsinization when 75-80% confluent.
In vitro cell uptake assay. SC cells and/or HUVECs adhered to 24 well tissue culture treated polystyrene plates (Falcon), were treated with DiI (Thermo) loaded micelles with or without latrunculin A and with or without FLT4 targeting peptide (1%, 3%, 5%) were added to each well for 2 hours at 37° C. After incubation, cells were washed with PBS and harvested using trypsinization. Cells were stained with Zombie Aqua cell viability dye and then washed and fixed with IC cell fixation buffer (BioLegend). Flow cytometry was performed using FACS diva on a BD Aria flow cytometer (BD biosciences). Untreated cells of both types were used to subtract out background fluorescence and flow data were analyzed using Cytobank software (Cytobank).
Atomic force microscopy on cultured Schlemm's canal cells. SC cells were grown in 60 mm petri-dishes (VWR) for 48 hours prior to experiment and were 80% confluent at the time of measurement. AFM measurements were made using a BioScope II with NanoscopeV controller (Bruker) coupled to an inverted fluorescent microscope with 10× (NA=0.3), 20× (NA=0.8) objective lens. Spherical polystyrene probes with a diameter of 10 1 μm (Novascan Technologies) mounted on silicon nitride cantilever with nominal spring constant of 0.01 N/m. The cantilever spring constant was calibrated prior to measurement using the Thermal Tune module of the Nanoscope. Throughout the duration of the experiment, SC cells were maintained with previously described cell culture media in an incubator at 37° C. To avoid substrate effects, indentation depth was restricted to 400 nm or less and the tip velocity was set to 800 nm/s to avoid viscous effects. Force measurements were performed at regions away from the nucleus and cell periphery to avoid confounding effects from either. Each cell was only probed one time and a minimum of 15 measurements was made for each sample group. Data from these AFM measurements were used to extract force versus indentation curves and the Hertz model was then utilized to calculate the Young's Modulus of the cells as we have previously described[11,36].
Confocal microscopy. SC cells were seeded in sterile 8 well confocal chamber slides (Thermo) and were allowed to grow in media for 24 hours prior to treatment. On the day of the experiment, fresh culture media was added containing anti-FLT4 PE conjugated antibody (Biolegend) and allowed to incubate with cells for 2 hours. Chamber slides were then washed with PBS and fixed using 4% paraformaldehyde (Electron Microscopy Sciences, Hatfield, PA) for 10 minutes at room temperature. Fixed cells were rinsed with PBS twice and then stained with Hoechst 33342 (1:10000) (Thermo) for 10 minutes. After rinsing 2 more times with PBS, fixed cells were imaged using a Zeiss 510 LSM inverted confocal microscope. Additionally, the same procedure was followed to examine Prox1 expression on SC cells as another possible targeting marker. SC cells were permeabilized using 100% methanol and subsequently stained with rabbit anti-PROX1 antibody (Abcam) along with a goat anti-rabbit IgG H&L (HRP) secondary antibody (Abcam). Proxl was not expressed on the surface of SC cells (
Widefield fluorescence microscopy on live cells. HUVECs and SC cells were plated at a density of 20,000 cells/well in glass-bottom 96-well plates (Greiner) and were allowed to adhere for 24 h prior to analysis. Cells were treated with anti-CD16/32 to block non-specific Fc receptor binding and were subsequently stained using anti-human VEGFR3/F1t4-APC antibody (BioLegend) per manufacturer recommendation. Cells were washed and stained with NucBlue (Hoechst 33342; cell permeable nuclear stain) prior to imaging. Widefield fluorescence microscopy images were obtained on ImageXpress High Content Imaging Robotic Platform (Molecular Devices). Images were acquired using the brightfield, DAPI, and Cy5 channels (magnification=40,000×). FLT4 was not expressed by HUVECs but was detectable on the surface of the SC cells (
Flow cytometric characterization of FLT4 expression. SC cells and HUVECs were seeded in tissue culture treated 12 well polystyrene plates and maintained in their respective cell culture media at 37° C. until 80% confluent at which point they were harvested by trypsinization and transferred to flow tubes. Cells were spun down at 400×g for 5 minutes and supernatant was removed. Cells were then incubated with Zombie Aqua cell fixability dye (1:100) (Thermo) for 15 minutes and then Anti-FLT PE antibody was added and allowed to incubate for 30 minutes. Cells were then spun down and fixed using IC fixation buffer (Biolegend). After fixation, flow cytometry was performed using FAC Sdiva on a FACS Aria flow cytometer (BD biosciences). PE median fluorescence intensity for live cells was determined using Cytobank software (Cytobank).
Animals. C57BL/6 (C57) mice were purchased from the Jackson Laboratory, bred/housed in clear cages, and kept in housing rooms at 21° C. with a 12 h:12 h light:dark cycle.
Intraocular pressure measurements. The mice were anesthetized with ketamine (60 mg/kg) and xylazine (6 mg/kg). IOP was measured immediately upon cessation of movement (i.e., in light sleep) using rebound tonometry (TonoLab; Icare). Each recorded IOP was the average of six measurements, giving a total of 36 rebounds from the same eye per recorded IOP value. IOP was conducted prior and post 24, 30 and 48 h nanoparticle injection.
Nanoparticles (NPs) injection. Three-month-old male C57 mice were randomly selected into three groups (A, B and C, 5 mice/group). The mice were anesthetized with an intraperitoneal injection of ketamine (100 mg/kg) and xylazine (10 mg/kg). A drop of 0.5% proparacaine, a topical anesthetic, was applied to the injection eye. A pulled microglass needle filled with NPs (labeled with A, B or C) and connected to a pump was inserted in one of the mouse anterior chambers (another non-treated eye was used as the contralateral control). Two microliters of the nanoparticles were infused in the mouse anterior chamber at a rate of 0.67 μl/min. After infusion, the needle was withdrawn, and topical erythromycin antibiotic ointment was applied to the infused eye. All the mice were maintained on a warm water-circulating blanket until they had recovered from the anesthesia and then returned to the animal housing rack.
Statistical analysis. All statistical analyses were performed using GraphPad Prism software (GraphPad Software; version 8.4.1). Each figure notes the specific type of statistical test utilized to determine statistical significance.
a)The number average diameter is presented.
Reference is made to Stack et al., “Targeted Delivery of Cell Softening Micelles to Schlemm's Canal Endothelial Cells for Treatment of Glaucoma”, Small 2020, 16, 43, 2004205, the content of which his incorporated by reference in entirety.
In Example 1, we developed a lipid-anchored targeting peptide that binds to FLT4/VEGFR3 receptors to target the delivery of cell softening agents to Schlemm's canal cells. FLT4 receptors are enriched on the Schlemm's canal endothelium in animal models35, cultured Schlemm's canal cells derived from healthy human donors34, and in human donor eyes by single cell RNA sequencing36,37. Despite this early work, multiple uncertainties remain regarding the use of a FLT4-targeting strategy. One uncertainty pertains to clinical utility and whether FLT4 receptors are expressed on the Schlemm's canal surface in the eyes of glaucoma patients to permit the targeted delivery of cell softening drugs. Second, to maximize the efficacy and minimize the side effects of these agents, it is important that the engineered vehicles optimally deliver drug payloads to Schlemm's canal cells instead of off-target endothelial cell types, in particular the corneal endothelium. Regarding our initial Schlemm's canal-targeting approach, steric considerations involving the PEG chains of the drug delivery vehicle chassis and their potential for obstructing receptor access to the peptide ligand motivated us to rationally design alternative ligand structures to improve performance. Suboptimal receptor binding is a general problem with targeted drug delivery systems38, and it is often left unresolved due to a lack of methods for optimizing ligand interactions at the nanocarrier surface. While useful insights into the role of ligand length on organ-level nanocarrier accumulation are available in the literature39, empirical relationships between ligand steric effects at nanocarrier surfaces and their consequences on multiscale targeting performance and impact on clinically-relevant outcomes remains unestablished.
In the following Example, we address these issues by developing a novel assay to measure peptide accessibility to proteolysis, which enabled us to quantify the availability of ligands for binding events. We were particularly interested in determining whether lipid-anchored targeting constructs can be optimized to maximize binding to FLT4 receptors, and whether differences in receptor engagement produced measurable differences in drug delivery vehicle performance in a clinically relevant setting. Using a multidisciplinary approach that included molecular characterization, in vitro targeting studies and direct evaluation in a murine model, we examined the potential for these optimized nanotherapeutics to target a cell softening agent to Schlemm's canal in vivo and lower IOP. C57BL/6J mice were used as an animal model in these studies due to their similar conventional outflow pathway anatomy, physiology, and pharmacologic responses to humans40-42. This work holds important clinical implications for the use of cell softening nanotherapies as safe and efficacious tools for managing glaucoma. Furthermore, the rational design principles established herein, as well as the empirical evidence supporting their utility, can be harnessed to meet diverse challenges in drug delivery.
Target validation: glaucomatous Schlemm's canal endothelial cells highly express FLT4/VEGFR3 receptors. The Schlemm's canal endothelium is somewhat unique in that it expresses both blood vascular and lymphatic characteristics50. FLT4 receptors are a lymphatic marker expressed by Schlemm's canal cells35. Developing strategies to promote nanocarrier interactions with FLT4 receptors offers a potential strategy for increasing their uptake by Schlemm's canal endothelial cells relative to blood vascular cells of the iris and ciliary body. While past studies detected FLT4 receptors on the surface of Schlemm's canal cells derived from normal human patients34, it is unclear whether glaucoma alters the expression of these receptors. To determine whether FLT4 is a viable cell surface marker for targeting Schlemm's canal cells in patients with glaucoma, FLT4 expression was examined in two normal and two glaucomatous Schlemm's canal cell strains from human donors (
Schlemm's canal cells expressed FLT4 at significantly greater levels than human umbilical vein endothelial cells (HUVECs), a representative model of blood vascular endothelial cells, in both the normal and glaucomatous cell strains examined (
†NA = Information not available
††Dex (dexamethasone) test. A negative Dex Test indicates a lack of myocilin induction upon treatment with dexamethasone, which is a response that is expected of SC cells and is used to distinguish isolated SC cells from the major possible contaminant, trabecular meshwork (TM) cells (a positive Dex Test is expected for TM cells).
Development of Schlemm's canal-targeted PEG-b-PPS micelles displaying optimized FLT4-binding peptides. The drug delivery vehicles developed in this work are polymeric micelles (MCs) self-assembled from oxidation-sensitive, amphiphilic poly(ethylene glycol)-b-poly(propylene sulfide) (PEG45-b-PPS23) diblock copolymers that employ a methoxy (—OCH3) group at the terminus of the PEG hydrophilic block (
†Hydrophilic weight fraction of polymer.
†All peptide constructs are of the form [Lipid]-[PEGX spacer]-[Peptide].
††Palmitoleic acid (PA).
†††The spacer length is presented as the number of PEG units.
‡The peptide construct with a 48-unit PEG spacer was synthesized using Fmoc-PEG24x2.
‡‡Peptide primary structure is listed N-terminus to C-terminus.
Peptides were embedded into PEG45-b-PPS23 MC nanocarriers at 1% or 5% molar ratios (peptide:polymer) and were purified through a lipophilic Sephadex column to remove any unembedded peptide. The resulting micelle formulations were monodisperse (PDI<0.1) with an average diameter of ˜21-23 nm (Table 5). Electrophoretic light scattering (ELS) analysis demonstrate a zeta potential indicative of a neutrally charged surface for all nanocarriers in the presence and absence or peptide (Table 5). Peptide incorporation into micelles was verified by Fourier transform infrared spectroscopy (FTIR;
The incorporation of peptide did not disrupt the spherical morphology expected for PEG-b-PPS micelles, as demonstrated by morphological analysis using cryogenic transmission electron microscopy (Cryo-TEM;
Micelle total diameter measurements obtained by SAXS was generally in agreement with the orthogonal analysis by DLS (Table 5). However, the higher resolution information obtained by probing the nanocarrier suspensions with high intensity x-rays did shed light on various structural details. Core shell models were fit to the data with high confidence, further supporting the micelle morphology was unperturbed by the presence of peptide at 1% (
†Number average hydrodynamic diameter (DTotal) and polydispersity index (PDI) measured by dynamic light scattering (DLS).
††Small angle x-ray scattering (SAXS) performed using synchrotron radiation at Argonne National Laboratory. The fit values for the total diameter (DTotal), thickness of the shell, and radius of the core (RCore) are displayed together with the chi squared (□2) value for the final model fit.
‡Mean zeta potential ± s.d. (n = 3) measured by electrophoretic light scattering (ELS).
While the shell thickness of micelles displaying PG48 at 1% or 5% molar ratio is greater than that of micelles displaying PG6 or PG24 at equivalent molar density, the shell thickness of PG48 formulations matched that of the blank micelles (Table 5). We attribute this observation to the greater continuity of the PEG corona in micelles prepared without peptide (blank micelles) and those displaying PG48, which scatter x-rays more consistently. The PG6 and PG24 constructs have fewer hydrophilic units than the 45-unit PEG block (PEG45) of the polymer (this is depicted in the
Evaluation of peptide biochemical accessibility and targeting Schlemm's canal cells in vitro. We hypothesized that targeting peptides designed with longer PEG spacers would minimize ligand obstruction by the micelle PEG corona to biomolecules in the surrounding environment, and that these accessibility enhancements would improve peptide binding with FLT4 receptors (
When presented on micelles in the PG48 form, the FLT4-binding peptide substrate was cleaved to completion almost immediately, whereas buried PG6 and PG24 constructs were cleaved at much slower rates (
To examine whether these differences in ligand accessibility translate into greater interactions with the Schlemm's canal cells, we performed nanocarrier uptake studies with cultured Schlemm's canal cells from normal human donors (target cell type) and HUVECs (vascular endothelial cell model; off-target cell type) (
For micelles displaying the PG6 or PG24 constructs, the use of shorter PEG spacers together with the 12 amino acid FLT4-binding peptide obstructs biochemical access to the ligand (
Performance evaluation of PG48 versus PG6 on enhancing the micellar delivery of IOP-reducing agents in vivo. As our goal was to develop nanocarriers capable of targeting Schlemm's canal cells and delivering payloads that lower IOP, we sought to determine if the optimized nanocarriers displaying the FLT4-binding peptide above the surface would outperform our original, buried peptide construct (PG6) in a more clinically relevant setting. We were particularly interested in evaluating the performance of the original PG6 construct34 against the more highly-targeted PG48 construct in the delivery of the IOP-reducing agent latrunculin A (LatA) in vivo. LatA is a 16-membered macrolide53 that acts by blocking the incorporation of actin monomers into actin filaments and thereby depolymerizing actin and lowering cell stiffness34,45. We executed a longitudinal assessment of IOP in C57BL/6J mice receiving LatA MC displaying either PG6 or PG48 in contralateral eyes. Aside from the introduction of the optimized targeting construct, this study incorporated a paired design and greater statistical power than our previous analysis34.
The baseline IOP was measured by tonometry prior to treatment. Significant differences were not found in the contralateral IOP measured at baseline (OS: 19.9±0.1 mmHg; OD: 19.9±0.2 mmHg;
However, a notable divergence in the efficacy of the two competing formulations was observed after 24 h (
From these results, we conclude the targeting performance of micelles displaying the PG48 FLT4-binding peptide is superior to that of micelles displaying the PG6 variant. This improved ability to target cell softening agent delivery to the Schlemm's canal endothelium enhanced efficacy by achieving a prolonged reduction in IOP that was statistically significant through 48 h after a single injection.
Localization of the optimal SC-targeting nanocarriers in the murine conventional outflow pathway. We next examined the localization of micelles displaying the PG48 peptide within the murine conventional outflow pathway (
We examined tissue sections prepared from the anterior segments of the negative control and nanocarrier-receiving eyes (
Glaucoma is a progressive disease that, if untreated, slowly but relentlessly destroys ganglion cells and robs vision. The lowering of IOP is the only treatment for glaucoma that is proven to decrease disease progression. Agents such as actin depolymerizers and Rho kinase inhibitors reduce cell stiffness and have been shown to lower the IOP when delivered to the aqueous humor outflow pathway. However, these agents have significant side effects that are associated with off-target vasodilation of ocular surface vessels. Using optimized nanocarriers loaded with an actin depolymerizing agent, LatA, we demonstrate here that we can target Schlemm's canal cells in a highly specific fashion using versatile nanocarriers and that these nanocarriers when loaded with a cell softening agent significantly lower IOP in murine eyes for an extended period of time.
As the goal was to develop a nanocarrier that selectively targeted Schlemm's canal cells, it was necessary to demonstrate that the target, FLT4, is expressed at high levels not only on normal, but also glaucomatous Schlemm's canal cells (
The overarching goal of the present work was to develop an improved nanotechnology platform for targeting the delivery of cell softening agents to the Schlemm's canal endothelium in order to lower IOP. Previous studies of LatA demonstrated promise in reducing the IOP25,26 but did not lead to the development of a clinical product. Our previous biomechanical analyses using atomic force microscopy (AFM) demonstrated that untargeted micellar delivery of LatA softens Schlemm's canal cells in vitro45, thereby confirming the successful lysosomal escape of an actin depolymerizing agent following cellular internalization and validated PEG-b-PPS nanocarriers as appropriate vehicles for delivering cell softening agents. In a separate set of studies we demonstrated that the targeted micellar delivery of LatA (LatA MC +PG6) at a low concentration of 50 nM is sufficient to significantly reduce Schlemm's canal cell stiffness compared to control in vitro34, and the targeted micellar delivery of 15.5-17 μM LatA using PG6 led to significant reductions in murine IOP for up to 24 h in vivo following intracameral injection34.
To improve the efficacy of cell softening agents delivered by Schlemm's canal-targeting micelles, we rationally designed variants of our modular lipid-anchored FLT4-binding peptide to achieve a greater influx of drug-loaded nanocarriers into the Schlemm's canal cells. We began this design process with the observation that our original Schlemm's canal-targeting construct34, denoted in the present work as “PG6”, was likely buried beneath the micelle surface where it is less accessible to FLT4 receptors. This design consideration is fairly unique to lipid-anchored targeting peptides embedded in amphiphilic nanocarriers, since materials are more commonly prepared for targeting via the direct conjugation of ligand to the surface55—a strategy that can encounter issues with a lack of modularity, usage of harsh chemical conditions, control over display density, among others56,57.
Understanding the relationship between the biochemical access of a lipid-anchored ligand and targeting performance became a focus of the present work, since the use of targeting moieties to direct vehicles to the intended location requires (i) successful ligand docking with the cognate receptor, which is enabled by the specific arrangement of functional groups of the ligand with those of the receptor binding pocket, but also (ii) a lack of obstruction that hinders formation of the ligand-receptor complex. The latter consideration permits successful binding events to occur with a greater frequency. Whereas the first requirement is fulfilled by the WHWLPNLRHYAS (SEQ ID NO: 1) peptide that was developed by phage display to specifically bind FLT4 receptors, the second requirement was not fully met, since the use of the six-unit PEG spacer left the lipid-anchored peptide shrouded within the 45-unit PEG corona of the micelles self-assembling from PEG45-b-PPS19 polymer.
These considerations prompted our rational design of optimized targeting peptide constructs that differed in their PEG linker lengths and display depth on micelles (
These considerations inspired our development of a novel method that uses trypsin as a biochemical probe. Trypsin acts on each peptide molecule only once, since the peptide contains one arginine residue and lysine is absent. Cleavage of the peptide by trypsin produces irreversible mass shifts, and the proteolysis kinetics are monitored to quantify differences in the accessibility of lipid-anchored targeting peptides displayed on amphiphilic nanocarriers (
In agreement with our hypothesis, the protease protection kinetic assay developed herein demonstrated that the use of 6-, 24-, or 48-unit PEG spacers achieves significant differences in biomolecular access to the peptide ligand (
Our paired longitudinal IOP studies demonstrated that LatA-loaded micelles displaying the biochemically enhanced PG48 construct led to a 7.5 mmHg reduction in IOP, on average, after 24 h compared to 7.1 mmHg achieved by treatment with the LatA MC+PG6 formulation (
Enhancing the biochemical access to the FLT4 binding peptide leads to a greater accumulation of cell softening agents within the Schlemm's canal endothelium. Higher drug concentrations at the target site resulted in longer lasting improvements in outflow facility to yield an IOP reduction that is sustained for a longer period of time. We further conclude that micelles displaying the PG48 construct are the highest performing nanocarrier chassis for delivering IOP-lowering cell softening agents to Schlemm's canal. PEG-b-PPS micelles efficiently load diverse hydrophobic small molecules 44,58 and will accommodate a wide variety of new and currently available therapeutics59.
Looking ahead, there remains the practical challenges of how the therapeutic effect of softening Schlemm's canal cells can be sustained for a longer period of time. As the corneal endothelium is permeable only to molecules with molecular weights less than approximately 500 Da60,61, nanoparticles cannot be delivered to the anterior segment topically. Instead, these agents need to be either (i) injected to the anterior segment or retro-injected into the aqueous veins62, or (ii) released continuously from a long-term depot/device placed in the eye. While injection is plausible for targeted-nanocarriers carrying gene therapy to Schlemm's canal, long term release is required for pharmacological treatments such as LatA carrying micelles as frequent intraocular injections would not be tolerated.
Aside from the more conventional delivery of pharmacological payloads, our Schlemm's canal targeting strategy can be extended to the development of gene delivery technologies63. Glaucoma is an attractive target for gene therapy64,65 and modulating the expression of genes that regulate the stiffness of Schlemm's canal endothelial cells may hold the key to producing more permanent enhancements in outflow facility without stents or surgery. The lipid-anchored FLT4-binding peptides are modular, and readily incorporate into alternative PEG-b-PPS morphologies, such as vesicular polymersomes48,56,58,66,67 or bicontinuous nanospheres68-70, which are capable of encapsulating the hydrophilic cargoes necessary for genetic intervention. This includes regulatory RNAs for the transient modulation of gene expression, or CRISPR/Cas9 components for stable genome editing.
In closing, we demonstrate that steric effects between surface-displayed ligands and PEG coronas significantly impact targeting performance across multiple biological scales. Our work holds general implications for the rational design of receptor-targeted nanocarriers and also addresses challenges that are unique to the display of modular ligands anchored to vehicles bearing a common hydrophilic corona (here, PEG2k). We further demonstrate that the assessment of differential proteolysis kinetics provides a powerful tool for quantifying the relative biochemical access of targeting ligand prototypes displayed on nanocarrier surfaces. The biochemical access of a targeting ligand is an engineerable property that can be leveraged to control nanocarrier engagement with receptors on the target cell type over a continuous domain. When applied to the development of glaucoma nanotherapies using our FLT4-targeting approach, improving the biochemical access of peptide ligands increased drug delivery to Schlemm's canal endothelial cells while minimizing off-target interactions with vascular endothelial cells. These performance improvements at the molecular and cellular levels translated to efficacy enhancements in a paired, longitudinal IOP study in vivo, thereby demonstrating the potential utility of our methods in clinically relevant settings. The technologies developed herein show promise for improving the potency and specificity of cell softening agents used to manage ocular hypertension. More generally, our rational design principles and methodology can be extended to the development of other targeted nanotherapies to solve diverse challenges in drug delivery.
Chemicals. Unless otherwise stated, all chemical reagents were purchased from the Sigma Aldrich Chemical Company.
Solid phase peptide synthesis. Fmoc-N-amido-dPEG6-acid, Fmoc-N-amido-dPEG24-acid, and Fmoc-N-amido-dPEG24-amido-dPEG24-acid (Quanta Biodesign) were purchased for use in the synthesis of the PG6, PG24, and PG48 peptide constructs. Standard Fmoc solid phase peptide synthesis was performed to synthesize PG6, PG24, and PG24×2 (PG48) peptides on a 0.125 mmol scale. Information regarding each synthesized peptide is presented in Table 4. The chemical structure of each peptide is presented in
Preparation of PEG-b-PPS micelle formulations. PEG45-b-PPS23 polymer was synthesized using established procedures43,44 (Table 3). Briefly, sodium methoxide was used to deprotect PEG thioacetate. This deprotected PEG thioacetate is then used to initiate the polymerization of propylene sulfide through an anionic ring opening polymerization reaction. MC nanocarriers were self-assembled from PEG45-b-PPS23 polymer43,44 via cosolvent evaporation using established protocols45. For uptake studies in vitro, MCs were prepared to load DiI hydrophobic dye (Invitrogen), whereas formulations intended for IOP studies in vivo were prepared to co-load latrunculin A (LatA; Cayman Chemical Company) and DiI. The formed MCs were split into aliquots of equal volume prior to the addition of peptide. PG6, PG24, or PG48 targeting peptides were dissolved in DMSO and were added to the specified MC aliquots at either a 1% or 5% molar ratio (peptide:polymer). Blank MC controls (lacking peptide) were included in cellular uptake studies. All formulations were prepared under sterile conditions and were filtered using a Sephadex LH-20 column.
Determination of peptide concentration. Peptide concentration in purified MCs was determined by measuring tryptophan fluorescence (λEx=270 nm, λEm=350 nm), calibrated against a peptide concentration series, using a SpectraMax M3 microplate reader (Molecular Devices, LLC). The peptide is readily detectable using these parameters (
Small angle x-ray scattering (SAXS). SAXS was performed using synchrotron radiation at the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) beamline at the Advanced Photon Source at Argonne National Laboratory (Argonne, IL, USA). A 7.5 m sample-to-detector distance, 10 keV (λ=1.24 Å) collimated x-rays, and 3 second exposure time was used in all SAXS experiments. The q-range of 0.001-0.5 Å−1 was used to analyze scattering, and silver behenate diffraction patterns were used for calibration. The momentum transfer vector (q) is defined in Equation 1, 0 denotes the scattering angle:
PRIMUS software (version 3.0.3) was used for data reduction. SasView (version 5.0) software was used for model fitting. A core shell sphere model (Equation 2) was fit to the scattering profiles of blank micelles (prepared without peptide), as well as micelles displaying PG6, PG24, or PG48 peptides at 1% or 5% molar ratios (peptide:polymer):
Where F is the structure factor, q is the momentum transfer vector (Equation 1), Vs is the particle volume (Å3), Vc is the particle core volume (Å3), ρc is the core scattering length density (10−6 Å−2), ρs is the shell scattering length density (10−6 Å−2), ρsolv is the solvent scattering length density (10−6 Å−2), rc is the core radius (Å). The radius of the total particle (rs; units: Å) is used to determine the shell thickness (rt; units: Å), as described by Equation 3:
Micelle diameter values determined from DLS (Table 5) were used to select initial values for the core radius and shell thickness prior to parameter fitting. An iterative chi square (χ2) minimization procedure using the Levenberg-Marquardt algorithm was used to fit optimal model parameters. A good core shell model fit is indicated by χ2<1.0. In all cases, χ2<<0.1 was obtained for final fit models.
Quantification of loaded drug concentration. Aliquots of purified LatA-loaded MC formulations were frozen at −80° C. and were lyophilized overnight. The resulting powder was resuspended in methanol and was placed at −20° C. for 1 h. Samples were centrifuged at 4,000×g for 5 min to sediment the polymer. After this extraction procedure, the supernatant (containing drug) was collected for further analysis. The concentration of LatA was determined using high performance liquid chromatography (HPLC) calibrated against a concentration series of LatA prepared in methanol (
Protease protection assay for examining the biochemical accessibility of targeting peptides. PEG-b-PPS micelle nanocarriers displaying PG6, PG24, or PG48 at 5% molar ratio were incubated with trypsin gold protease (Promega) at 37° C., 80 rpm for 10 h. A peptide concentration of 40 nM and enzyme concentration of 800 nM (1:20 ratio) was used in these experiments. Reaction aliquots were quenched in 2% formic acid at the specified timepoints. Quenched reaction aliquots were mixed 1:1 with 50:50 methanol/acetonitrile with 0.1% trifloroacetic acid (TFA), and a saturating quantity of α-Cyano-4-hydroxycinnamic acid (Sigma) matrix. Samples were applied to 384-spot polished stainless-steel plates and were dried under hot air using a heat gun. Data was acquired using matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF) using a Bruker rapifleX MALDI Tissuetyper TOF MS instrument.
Primary cell culture. Normal and glaucomatous Schlemm's canal endothelial cells were isolated from post-mortem human eyes obtained from BioSight (Table 2) and were cultured using established procedures46,47. Human umbilical vein endothelial cells (HUVECs) from pooled donors were purchased from Lonza, Ltd. The passage number of all primary cells used in these studies was less than six. Schlemm's canal cells were cultured in low glucose DMEM (Gibco) supplemented with 10% fetal bovine serum and 1×penicillin-streptomycin-glutamine (Gibco). HUVECs were cultured in endothelial cell growth basal medium-2 (EBM-2; Lonza) supplemented with FBS and an EGM-2 BulletKit (Lonza) optimized for HUVEC culture. All cells were cultured at 37° C., 5% CO2 in T25 or T75 flasks.
Quantification of FLT4/VEGFR3 expression by flow cytometry. Schlemm's canal (SC) cells, glaucomatous Schlemm's canal cells (SCg), or HUVECs (n=3) were seeded in 24-well plates at a density of 100,000 cells per well. Cells were cultured in their appropriate media types (described elsewhere in this methods section) and were allowed to adhere overnight at 37° C., 5% CO2. On the following day, media was aspirated, cells were washed with PBS, and single cell suspensions were prepared following established procedures34,48. Cell pellets were resuspended in cell staining buffer with zombie aqua cell viability stain (BioLegend), were incubated at 4° C. for 15 minutes, and were washed with cell staining buffer. After a subsequent blocking step, cells were incubated with an APC-conjugated anti-human VEGFR3 (FLT4) antibody (BioLegend) for 20 minutes at 4° C. and were then subjected to two iterative rounds of washing (and centrifugation) per manufacturer recommendations. Cells were fixed using a paraformaldehyde cell-fixation buffer (BioLegend). Flow cytometry was performed using a BD LSRFortessa Flow Cytometer. Cytobank software49 was used to analyze the acquired data.
Live cell imaging by high-throughput widefield fluorescence microscopy. Schlemm's canal (SC) cells, glaucomatous Schlemm's canal (SCg) cells, or HUVECs (n=3) were seeded in glass-bottom 96-well plates (Greiner) at a seeding density of 25,000 cells/well, and were placed at 37° C., 5% CO2 overnight. Cells were washed, blocked, and were then placed in media containing APC-conjugated anti-human FLT4/VEGFR3 antibody (BioLegend) for 30 minutes at 37° C. Afterwards, the media was removed by aspiration and cells were gently washed twice with fresh media. After the final wash step, cells were treated with media supplemented with cell-permeant NucBlue (Hoechst 33342) counterstain to visualize cell nuclei. High-throughput widefield fluorescence microscopy was performed using an ImageXpress High Content Imager (Molecular Devices). Images of live cells were acquired at 40× magnification in brightfield, DAPI, and Cy5 channels.
Nanocarrier uptake studies. Schlemm's canal cells or HUVECs were seeded at a density of 100,000 cells/well in 48-well plates and were allowed to adhere overnight at 37° C., 5% CO2. Cells were treated with the specified DiI-loaded MC formulations (0.5 mg/mL polymer) for 2 h at 37° C., 5% CO2. All experiments included untreated cells and a PBS-treatment group, as well as three biological replicates per treatment group (n=3). MC uptake was quantified by flow cytometry using a BD LSRFortessa Flow Cytometer and the acquired data was analyzed using Cytobank software49. The median fluorescence intensity (MFI) above PBS-treated background was calculated to remove cellular autofluorescence contributions to the measured values.
Longitudinal evaluation of intraocular pressure (IOP) in vivo. The mice were anesthetized with ketamine (60 mg/kg) and xylazine (6 mg/kg). IOP was measured using rebound tonometry (TonoLab; Icare) immediately upon cessation of movement (i.e., in light sleep). Each recorded IOP was the average of six measurements, giving a total of 36 rebounds from the same eye per recorded IOP value. IOP was measured three times prior to nanocarrier treatment and 24, 30, 48, 72, and 96 h following nanoparticle injection. A total of nine mice were used for the 0-48 h timepoints. Four mice and three mice were carried through the 72 h and 96 h timepoints, respectively.
Intracameral injection of nanocarrier formulations. For IOP studies, three-month-old female C57 mice were anesthetized with an intraperitoneal injection of ketamine (100 mg/kg) and xylazine (10 mg/kg). A drop of 0.5% proparacaine, a topical anesthetic, was applied to both eyes. Two pulled microglass needles filled with nanocarrier formulation (labeled “A” or “B”) and connected to a pump were alternatively inserted into both mouse anterior chambers. A volume of 2 μL of nanocarrier formulation “A” or “B” containing 18 μM LatA was infused into the anterior chamber of contralateral mouse eyes at a rate of 0.67 μL/min. Thus, this procedure delivered 15.2 ng of LatA per eye. After infusion, the needles were withdrawn, and topical erythromycin antibiotic ointment was applied to both eyes. All the mice were maintained on a warm water-circulating blanket until they had recovered from the anesthesia and the animals were subsequently returned to the animal housing rack. Unmasking of treatment identity occurred after all IOP measurements were recorded.
Confocal microscopy. Mouse eyes were dissected into 8 radial wedges. Each wedge was immersed in Vectashield® mounting media containing DAPI (Vector Laboratories) in a glass-bottom dish and were imaged along one of the two sagittal planes using a Zeiss LSM 700 confocal microscope (Carl Zeiss). The uninjected contralateral eyes were used as negative control. Single images and tiles images were acquired using a 20×objective to capture either Schlemm's canal and its surrounding structures or the entire sagittal plane, using the ZEN2010 operating software (Carl Zeiss).
Statistical analysis. Statistical analyses were performed using Prism software (version 9.0.0; GraphPad Prism Software, LLC). Details of each statistical analysis are provided in the Brief Description of the Drawings.
Dynamic light scattering (DLS) and electrophoretic light scattering (ELS). The number average diameter and polydispersity index (PDI) of nanocarriers was determined by DLS using a Zetasizer Nano instrument (Malvern Instruments). The number average PDI was calculated using a custom MATLAB script (version R2019a). ELS was performed to determine zeta potential.
Cryogenic transmission electron microscopy (Cryo-TEM). Copper grids (200 mesh) with a lacey carbon membrane (EMS Cat #LC200-Cu-100) were glow-discharged in a Pelco easiGlow™ Glow Discharge Cleaning System (Ted Pella). This procedure used an atmosphere plasma generated at 15 mA for 15 seconds and a pressure of 0.24 mbar. A sample volume of 4 μL was applied to the grid. The grid was blotted for 5 seconds with a blot offset of +0.5 mm and was subsequently plunged into liquid ethane within a FEI Vitrobot Mark III plunge freezing instrument (Thermo Fisher Scientific). Specimens were imaged using a JEOL JEM1230 LaB6 emission TEM (JEOL USA) operating at 100 keV. The plunge-frozen grids were kept vitreous at −180° C. in a Gatan Cryo Transfer Holder (Model 626.6) during imaging. Images were acquired using a Gatan Orius SC1000 CCD camera (Model 831).
Fourier transform infrared (FTIR) spectroscopy. FTIR spectroscopy was performed using a Nicolet™ i S50 FTIR Spectrometer (Thermo Scientific). The background spectra for air were collected prior to obtaining measurements for the experimental samples. Spectra were obtained from liquid samples of purified PEG-b-PPS micelle formulations prepared with and without the specified targeting peptide construct (PG6, PG24, or PG48) displayed at a 5% molar ratio (peptide:polymer). Measurements were obtained in the wavenumber range of 2000-600 cm−1 and 64 scans were collected per sample. The presence of peptide bonds was detected by analyzing the 1700-1600 cm−1 (amide I) and 1590-1520 cm−1 (amide II) bands.
Animals. All experiments that used animals were completed in compliance with The Association for Research in Vision and Ophthalmology (ARVO) “Statement for the Use of Animals in Ophthalmic and Vision Research”. For IOP studies, mice were handled in accordance with a protocol (A001-19-01) approved by the Institutional Animal Care and Use Committee of Duke University. For confocal microscopy studies (see below) at Boston University, local Institutional Animal Care and Use Committee (IACUC) approval was obtained.
C57BL/6 (C57) mice were purchased from The Jackson Laboratory. Mice were housed and bred in clear cages and were maintained in housing rooms at 21° C. with a 12 h:12 h light:dark cycle. At Boston University, mice were housed in the Animal Science Center of Boston University Medical Campus, with a 12-hour light/12-hour dark cycle and access to food and water ad libitum. Upon arrival, mice were examined to confirm a normal appearance, i.e., free of any signs of ocular disease, and allowed to acclimatize for at least three days before experiments.
Confocal microscopy of ocular tissues. Mice (n=2) were anesthetized with 87.5 mg/kg ketamine (Henry Schein Inc.) and 12.5 mg/kg xylazine (Henry Schein Inc.) administered by intraperitoneal injection. One eye of each mouse was then injected with nanocarriers using an adapted protocol based on published procedures' for the administration of 20 nm fluorescent tracers (carboxylate-modified FluoSpheres; Invitrogen). Briefly, a 10-μL Hamilton microsyringe (Nanofil; World Precision Instruments) was loaded with 1μL solution of nanocarriers (20 mg/mL polymer concentration), as well as 2 μL modified 4% paraformaldehyde (PFA) separated by a 0.2 μL air bubble. A 35G needle (NF35BL-2; World Precision Instruments) connected to this syringe was then inserted in the central region of the anterior chamber to uniformly distribute the injected nanocarriers. The nanocarrier injection volume was delivered at a rate of 4 nL/s using a microprocessor-based microsyringe pump controller (Micro4; World Precision Instruments). The 12 o'clock position of the eye was marked using Tissue Marking Dye (TMD; Triangle Biomedical Sciences) to provide orientation information. The nanocarriers were allowed to migrate through the anterior chamber, penetrate the trabecular meshwork, and reach Schlemm's canal for a period of 45 minutes while the needle remained in the eye. During this time, artificial tears (Henry Schein Inc.) were applied to the cornea of both eyes to prevent dehydration. A 2 μL volume of 4% paraformaldehyde (PFA) was subsequently injected into the anterior chamber while additional fixative was simultaneously applied to the exterior of the eye. After 30 minutes of fixation, both eyes were enucleated after euthanizing the mouse. The enucleated eyes were immersion-fixed in 4% PFA at 4° C. overnight, transferred to PBS, and then stored at 4° C. for further processing.
(24) Kaufman, P. L.; Bill, A.; Bárány, E. H. Effect of Cytochalasin B on Conventional Drainage of Aqueous Humor in the Cynomolgus Monkey. Exp. Eye Res. 1977, 25 Suppl, 411-414.
This application claims priority to U.S. Provisional Application No. 63/203,128 filed on Jul. 9, 2021, the contents of which are incorporated by reference in their entireties.
This invention was made with government support under grant numbers EY019696 and HL132390 awarded by the National Institutes of Health.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US22/73598 | 7/11/2022 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63203128 | Jul 2021 | US |
