NA3 glycan: a potential therapy for retinal pigment epithelial deficiency.

Atrophic age-related macular degeneration (AMD) is the most common type of AMD, yet there is no United States Food and Drug Administration (FDA)-approved therapy. This disease is characterized by retinal pigment epithelial (RPE) insufficiency, primarily in the macula, which affects the structure and physiology of photoreceptors and ultimately, visual function. In this study, we evaluated the protective effects of a naturally derived small molecule glycan therapeutic-asialo-, tri-antennary complex-type N-glycan (NA3)-in two distinct preclinical models of atrophic AMD. In RPE-deprived Xenopus laevis tadpole eyes, NA3 supported normal retinal ultrastructure. In RCS rats, NA3 supported fully functioning visual integrity. Furthermore, structural analyses revealed that NA3 prevented photoreceptor outer segment degeneration, pyknosis of the outer nuclear layer, and reactive gliosis of Müller cells (MCs). It also promoted maturation of adherens junctions between MC and photoreceptors. Our results demonstrate the neuroprotective effects of a naturally derived small molecular glycan therapeutic-NA3-in two unique preclinical models with RPE insufficiency. These data suggest that NA3 glycan therapy may provide a new therapeutic avenue in the prevention and/or treatment of retinal diseases such as atrophic AMD.

Poly(ortho ester) nanoparticles targeted for chronic intraocular diseases: ocular safety and localization after intravitreal injection.

Treatment of posterior eye diseases is more challenging than the anterior segment ailments due to a series of anatomical barriers and physiological constraints confronted by drug delivery to the back of the eye. In recent years, concerted efforts in drug delivery have been made to prolong the residence time of drugs injected in the vitreous humor of the eye. Our previous studies demonstrated that poly(ortho ester) (POE) nanoparticles were biodegradable/biocompatible and were capable of long-term sustained release. The objective of the present study was to investigate the safety and localization of POE nanoparticles in New Zealand white rabbits and C57BL/6 mice after intravitreal administration for the treatment of chronic posterior ocular diseases. Two concentration levels of POE nanoparticles solution were chosen for intravitreal injection: 1.5 mg/ml and 10 mg/ml. Our results demonstrate that POE nanoparticles were distributed throughout the vitreous cavity by optical coherence tomography (OCT) examination 14 days post-intravitreal injection. Intraocular pressure was not changed from baseline. Inflammatory or adverse effects were undetectable by slit lamp biomicroscopy. Furthermore, we demonstrate that POE nanoparticles have negligible toxicity assessed at the cellular level evidenced by a lack of glia activation or apoptosis estimation after intravitreal injection. Collectively, POE nanoparticles are a novel and nontoxic as an ocular drug delivery system for the treatment of posterior ocular diseases.

Novel endogenous glycan therapy for retinal diseases: safety, in vitro stability, ocular pharmacokinetic modeling, and biodistribution.

Asialo, tri-antennary oligosaccharide (NA3 glycan) is an endogenous compound, which supports proper folding of outer segment membranes, promotes normal ultrastructure, and maintains protein expression patterns of photoreceptors and Müller cells in the absence of retinal pigment epithelium support. It is a potential new therapeutic for atrophic age-related macular degeneration (AMD) and other retinal degenerative disorders. Herein, we evaluate the safety, in vitro stability, ocular pharmacokinetics and biodistribution of NA3. NA3 was injected into the vitreous of New Zealand white rabbits at two concentrations viz. 1 nM (minimum effective concentration (MEC)) and 100 nM (100XMEC) at three time points. Safety was evaluated using routine clinical and laboratory tests. Ocular pharmacokinetics and biodistribution of [(3)H]NA3 were estimated using scintillation counting in various parts of the eye, multiple peripheral organs, and plasma. Pharmacokinetic parameters were estimated by non-compartmental modeling. A 2-aminobenzamide labeling and hydrophilic interaction liquid interaction chromatography were used to assess plasma and vitreous stability. NA3 was well tolerated by the eye. The concentration of NA3 in eye tissues was in the order: vitreous > retina > sclera/choroid > aqueous humor > cornea > lens. Area under the curve (0 to infinity) (AUC∞) was the highest in the vitreous thereby providing a positive concentration gradient for NA3 to reach the retina. Half-lives in critical eye tissues ranged between 40 and 60 h. NA3 concentrations were negligible in peripheral organs. Radioactivity from [(3)H]NA3 was excreted via urine and feces. NA3 was stable at 37°C in vitreous over a minimum of 6 days, while it degraded rapidly in plasma. Collectively, these results document that NA3 shows a good safety profile and favorable ocular pharmacokinetics.

Synthesis, characterization and in vitro studies of celecoxib-loaded poly(ortho ester) nanoparticles targeted for intraocular drug delivery.

The present investigation is aimed at improving the ocular bioavailability of a poorly water soluble drug, celecoxib, to offer new options in the treatment of chronic eye diseases, such as age-related macular degeneration and diabetic retinopathy. To do so, we developed a novel formulation of drug-loaded poly(ortho ester) nanoparticles (NPs). We characterized the NPs in terms of size, morphology, controlled-release, degradation and cytocompatibity. Stable and transparent NP emulsions were prepared following a double emulsion solvent diffusion method employing poloxamer 188 as a stabilizer. Physical properties showed a narrow range size distribution of 151-164nm with spherical morphology, negative zeta potentials and remarkably high celecoxib encapsulation efficiency (98%) and loading (64%) of poly(ortho ester) NPs. Drug release followed a zero-order release by a surface erosion-controlled mechanism without any burst effect. Degradation of poly(ortho ester) NPs was observed by measuring the concentration of initial degradation product such as, lactic acid. MTT studies revealed minimal toxicity of NPs (up to 1mg/ml) toward HEK 293 cells. Poly(ortho ester) NPs were not internalized by either Müller or HEK 293 cells, which is highly desirable for a drug carrier to deliver the drugs for prolonged periods to the back of eye. These features have the potential to decrease the number of intraocular injections required to treat chronic eye diseases.

Poly(ortho ester) nanoparticle-based targeted intraocular therapy for controlled release of hydrophilic molecules.

Development of an efficient intraocular drug delivery nanosystem remains the most difficult challenge to attain a prolonged therapeutic effect at the site of drug action. The purpose of this work was to develop a biodegradable, long-term sustained release, and biocompatible nanoparticulate system to treat various intraocular diseases. To attain the objectives, poly(ortho ester) (POE), a hydrophobic, surface erodible, and nontoxic polymer, was selected for fabrication of nanoparticles for the first time using a double emulsion solvent evaporation method. The influence of POE molecular weight on particle size, polydispersity index, zeta potential, drug content, in vitro release, degradation, in vitro cytotoxicity, and cell uptake studies was investigated. Drug-loaded nanoparticles had a spherical shape with an average particle diameter from 241 to 298 nm and zeta potential values from -8 to -11 mV. Encapsulation efficiency ranged between 21 and 63%, depending on the type of the water-soluble molecule used. Approximately 20-30% of the loaded drug was released over a period of 14 weeks. The drug release and degradation profiles of nanoparticles followed perfect zero-order kinetics confirming the POE-surface erosion mechanism. In vitro cytotoxicity and cell uptake studies revealed the cyto-compatible nature and nonendocytic behavior of POE nanoparticles. Collectively, POE nanoparticles are a very promising vehicle for sustained delivery of therapeutics to the back of the eye.