Sustained delivery of acriflavine from the suprachoroidal space provides long term suppression of choroidal neovascularization

Hypoxia-inducible factor-1 (HIF-1) has been implicated in the pathogenesis of choroidal neovascularization (NV) and is an appealing target because it increases multiple pro-angiogenic proteins and their receptors. Acriflavine (ACF) binds HIF-1α and HIF-2α preventing binding to HIF-1β and inhibiting transcriptional activity of HIF-1 and HIF-2. Delivery of ACF to the eye by multiple routes strongly, but transiently, suppresses choroidal NV. We overcame design challenges and loaded highly water soluble ACF into poly(lactic-co-glycolic acid) (PLGA) microparticles (PLGA-ACF MPs) that release ACF in vitro for up to 60 days. Intravitreous injection of PLGA-ACF MPs in mice suppressed choroidal NV for at least 9 weeks and suprachoroidal injection of PLGA-ACF in rats suppressed choroidal NV for at least 18 weeks. Intravitreous, but not suprachoroidal injection, of PLGA-ACF MPs containing 38 μg of ACF in rabbits resulted in modest reduction of full-field electroretinogram (ERG) function. Over the span of 28 days after suprachoroidal injection of PLGA-ACF MP, rabbits had normal appearing retinas on fundus photographs, normal electroretinogram scotopic a- and b-wave amplitudes, no increase in intraocular pressure, and normal retinal histology. The active component of ACF, trypaflavine, had steady-state levels in the low nM range in RPE/choroid > retina for at least 16 weeks with a gradient from the side of the eye where the injection was done to the opposite side. These data suggest that suprachoroidal injection of PLGA-ACF MPs has the potential to provide a durable new treatment for retinal and choroidal vascular diseases.

A Small-Molecule Pan-Id Antagonist Inhibits Pathologic Ocular Neovascularization

Id helix-loop-helix (HLH) proteins (Id1-4) bind E protein bHLH transcription factors, preventing them from forming active transcription complexes that drive changes in cell states. Id proteins are primarily expressed during development to inhibit differentiation, but they become re-expressed in adult tissues in diseases of the vasculature and cancer. We show that the genetic loss of Id1/Id3 reduces ocular neovascularization in mouse models of wet age-related macular degeneration (AMD) and retinopathy of prematurity (ROP). An in silico screen identifies AGX51, a small-molecule Id antagonist. AGX51 inhibits the Id1-E47 interaction, leading to ubiquitin-mediated degradation of Ids, cell growth arrest, and reduced viability. AGX51 is well-tolerated in mice and phenocopies the genetic loss of Id expression in AMD and ROP models by inhibiting retinal neovascularization. Thus, AGX51 is a first-in-class compound that antagonizes an interaction formerly considered undruggable and that may have utility in the management of multiple diseases.

AAV8-vectored suprachoroidal gene transfer produces widespread ocular transgene expression

There has been great progress in ocular gene therapy, but delivery of viral vectors to the retinal pigmented epithelium (RPE) and retina can be challenging. Subretinal injection, the preferred route of delivery for most applications, requires a surgical procedure that has risks. Herein we report a novel gene therapy delivery approach, suprachoroidal injection of AAV8 vectors, which is less invasive and could be done in an outpatient setting. Two weeks after suprachoroidal injection of AAV8.GFP in rats, GFP fluorescence covered 18.9% of RPE flat mounts and extended entirely around sagittal and transverse sections in RPE and photoreceptors. After 2 suprachoroidal injections of AAV8.GFP, GFP fluorescence covered 30.5% of RPE flat mounts. Similarly, widespread expression of GFP occurred in nonhuman primate and pig eyes after suprachoroidal injection of AAV8.GFP. Compared with subretinal injection in rats of RGX-314, an AAV8 vector expressing an anti-VEGF Fab, suprachoroidal injection of the same dose of RGX-314 resulted in similar expression of anti-VEGF Fab and similar suppression of VEGF-induced vascular leakage. Suprachoroidal AAV8 vector injection provides a noninvasive outpatient procedure to obtain widespread transgene expression in retina and RPE.

Three-Dimensional Transport Model for Intravitreal and Suprachoroidal Drug Injection

Purpose

Quantitative understanding of the transport of therapeutic macromolecules following intraocular injections is critical for the design of efficient strategies in treating eye diseases, such as neovascular (wet) age-related macular degeneration (AMD) and macular edema (ME). Antiangiogenic treatments, such as neutralizing antibodies against VEGF or recently characterized antiangiogenic peptides, have shown promise in slowing disease progression.

Methods

We developed a comprehensive three-dimensional (3D) transport model for intraocular injections using published data on drug distribution in rabbit eyes following intravitreal and suprachoroidal (SC) injection of sodium fluorescein (SF), bevacizumab, and ranibizumab. The model then was applied to evaluate the distribution of small molecules and antiangiogenic proteins following intravitreal and SC injections in human eyes.

Results

The model predicts that intravitreally administered molecules are substantially mixed within the vitreous following injection, and that the long-term behavior of the injected drug does not depend on the initial mixing. Ocular pharmacokinetics of different drugs is sensitive to different clearance mechanisms. Effective retinal drug delivery is impacted by RPE permeability. For VEGF antibody, intravitreal injection provides sustained delivery to the retina, whereas SC injection provides more efficient, but short-lived, retinal delivery for smaller-sized molecules. Long-term suppression of neovascularization through SC administration of antiangiogenic drugs necessitates frequent injection or sustained delivery, such as microparticle-based delivery of antiangiogenic peptides.

Conclusions

A comprehensive 3D model for intravitreal and SC drug injection is developed to provide a framework and platform for testing drug delivery routes and sustained delivery devices for new and existing drugs.

Tyrosine kinase blocking collagen IV-derived peptide suppresses ocular neovascularization and vascular leakage

Vascular endothelial growth factor (VEGF)-neutralizing proteins provide benefit in several retinal and choroidal vascular diseases, but some patients still experience suboptimal outcomes, and the need for frequent intraocular injections is a barrier to good outcomes. A mimetic peptide derived from collagen IV, AXT107, suppressed subretinal neovascularization (NV) in two mouse models predictive of effects in neovascular age-related macular degeneration (NVAMD) and inhibited retinal NV in a model predictive of effects in ischemic retinopathies. A combination of AXT107 and the current treatment aflibercept suppressed subretinal NV better than either agent alone. Furthermore, AXT107 caused regression of choroidal NV. AXT107 reduced the VEGF-induced vascular leakage that underlies macular edema in ischemic retinopathies and NVAMD. In rabbit eyes, which are closer to the size of human eyes, intraocular injection of AXT107 significantly reduced VEGF-induced vascular leakage by 86% at 1 month and 70% at 2 months; aflibercept significantly reduced leakage by 69% at 1 month and did not reduce leakage at 2 months, demonstrating the longer effectiveness of AXT107. AXT107 reduced ligand-induced phosphorylation of multiple receptors: VEGFR2, c-Met, and PDGFRβ. Optimal signaling through these receptors requires complex formation with β₃ integrin, which was reduced by AXT107 binding to α_vβ₃ AXT107 also reduced total VEGFR2 levels by increasing internalization, ubiquitination, and degradation. This biomimetic peptide is a sustained, multitargeted therapy that may provide advantages over intraocular injections of specific VEGF-neutralizing proteins.

Recombinant non-collagenous domain of alpha2(IV) collagen causes involution of choroidal neovascularization by inducing apoptosis

Vascular endothelial cells receive proangiogenic or antiangiogenic signals from components of extracellular matrix (ECM) depending upon the situation and many molecular signals can have opposite effects in different vascular beds. Tissue inhibitor of metalloproteinase 1 is antiangiogenic in several tissues, but promotes retinal neovascularization. When cleaved from native collagens, several of the non-collagenous domains (NC1) of basement membrane collagens have antiangiogenic effects in some tissues, but this is context dependent for the NC1 of the alpha 1 chain of collagen IV. It is critical to examine effects in several well-defined model systems before assuming that an ECM component is universally antiangiogenic. In this study, we examined the effects of a recombinant fragment of NC1 of the alpha 2 chain of type IV collagen (alpha2(IV)NC1) in a well-characterized model of ocular neovascularization. Intravitreous or periocular injections of alpha2(IV)NC1 caused selective apoptosis of endothelial cells participating in neovascularization resulting in suppression of neovascularization when the peptide was given prior to onset of new vessel sprouting. Importantly, when the peptide was given after neovascularization had already developed, it caused the new vessels to regress. This suggests that alpha2(IV)NC1, which has previously been shown to suppress tumor angiogenesis in xenograft models, is also a strong antiangiogenic agent in the choroid and is a therapeutic candidate for treatment of neovascular age-related macular degeneration.

Intraocular injection of an aptamer that binds PDGF-B: a potential treatment for proliferative retinopathies

Platelet-derived growth factor-B (PDGF-B) has been implicated in the pathogenesis of proliferative retinopathies and other scarring disorders in the eye. In this study, we sought to test the therapeutic potential of an aptamer that selectively binds PDGF-B, ARC126, and its PEGylated derivative, ARC127. Both ARC126 and ARC127 blocked PDGF-B-induced proliferation of cultured fibroblasts with an IC50 of 4 nM. Pharmacokinetic studies in rabbits showed similar peak vitreous concentrations of approximately 110 microM after intravitreous injection of 1 mg of either ARC126 or ARC127, but the terminal half-life was longer for ARC127 (98 versus 43 h). Efficacy was tested in rho/PDGF-B transgenic mice that express PDGF-B in photoreceptors and develop severe proliferative retinopathy resulting in retinal detachment. Compared to eyes injected with 20 microg of scrambled aptamer in which five of six developed detachments (three total and two partial), eyes injected with ARC126 (no detachment in five of six and one partial detachment), or ARC127 (no detachment in six of six) had significantly fewer retinal detachments. They also showed a significant reduction in epiretinal membrane formation. These data demonstrate that a single intravitreous injection of an aptamer that specifically binds PDGF-B is able to significantly reduce epiretinal membrane formation and retinal detachment in rho/PDGF-B mice. These striking effects in an aggressive model of proliferative retinopathy suggest that ARC126 and ARC127 should be considered for treatment of diseases in which PDGF-B has been implicated, including ischemic retinopathies such as proliferative diabetic retinopathy, proliferative vitreoretinopathy (PVR), and choroidal neovascularization.

Vascular Targeting of Ocular Neovascularization with a Vascular Endothelial Growth Factor121/Gelonin Chimeric Protein

Tumors provide an extremely abnormal microenvironment that stimulates neovascularization from surrounding vessels and causes altered gene expression within vascular cells. Up-regulation of vascular endothelial growth factor (VEGF) receptors has allowed selective destruction of tumor vessels by administration of a chimeric protein consisting of VEGF121 coupled to the toxin gelonin (VEGF/rGel). We sought to determine whether there is sufficient up-regulation of VEGF receptors in endothelial cells participating in ocular neovascularization to permit a similar strategy. After intravenous injection of 45 mg/kg VEGF/rGel, but not uncoupled recombinant gelonin (rGel), there was immunofluorescent staining for rGel within choroidal neovascularization in mice and regression of the neovascularization occurred, demonstrating successful vascular targeting via the systemic circulation. Intraocular injection of 5 ng of VEGF/rGel also caused significant regression of choroidal neovascularization and regression of retinal neovascularization in two models, transgenic mice with expression of VEGF in photoreceptors and mice with ischemic retinopathy, whereas injection of 5 ng of rGel had no effect. These data suggest that the strategy of vascular targeting can be applied to nonmalignant neovascular diseases and could serve as the basis of a new treatment to reduce established ocular neovascularization.