A pilot study of topical treatment with an alpha2-agonist in patients with retinal dystrophies

Progression Rate of Visual Function and Affecting Factors at Different Stages of Retinitis Pigmentosa

We reviewed medical records of 121 patients/235 eyes of typical retinitis pigmentosa (RP) patients who could be followed up for at least 5 years with the aim of investigating the long-term course of visual function progression at each RP stage and appropriate assessment methods. Patients were classified into three groups: mild RP ( $\text{baseline}\text{mean}\text{deviation}\left(\text{MD}\right)\ge -5$ ), moderate RP ( $-25<\text{baseline}\text{MD}<-5$ ), and late RP ( $\text{baseline}\text{MD}\le -25$ ). Linear mixed-effect models were used to follow MD, the average retinal sensitivity of the central four points of the Humphrey field analyzer 10-2 program (S4), and visual acuity (VA) with increasing time. The associations among factors (baseline MD group, sex, hereditary form) and the interaction between each factor and time were also investigated. The mean reduction of the MD, S4, and VA for all patients was -0.37 dB/year, -0.25 dB/year, and 0.018/year, respectively. The moderate RP group had a faster progression than other groups in MD (-0.43 dB/year, $p<0.05$ ). The moderate (-0.31 dB/year, $p=0.01$ ) and late RP groups (-0.25 dB/year, $p<0.01$ ) had faster progression than the mild RP group in S4. The late RP group had faster progression in VA than the other groups (0.03/year, $p<0.05$ ). Females had a slower progression of the S4 (-0.15 dB/year, $p=0.02$ ) and VA (0.01/year, $p<0.001$ ) than males. The autosomal dominant group had a slower progression than the sporadic group in MD (-0.22 dB/year, $p=0.02$ ); the autosomal dominant and autosomal recessive groups had a slower VA decline than the sporadic group (0.01/year, $p=0.03$ ; 0.01/year, $p=0.04$ ). Because the progression rates of VA and visual field test differed as per the RP stage, S4 and VA can also be useful assessment methods depending on the stage. Inheritance form and sex may affect the progression rate.

Ocular Pharmacokinetics of Brimonidine Drug Delivery System in Monkeys and Translational Modeling for Selection of Dose and Frequency in Clinical Trials

Brimonidine, a selective α ₂-adrenoceptor agonist, displays putative retinal cyto- and neuroprotective activity in vitro and in vivo. An intravitreal sustained-release brimonidine implant, Brimonidine Posterior Segment Drug Delivery System (brimonidine DDS), allowing targeted drug delivery to the retina has been developed for potential clinical application. This study evaluates the in vivo posterior segment pharmacokinetics of brimonidine DDS implant in the monkey eye and applies translational pharmacokinetic modeling to predict tissue exposure in the human eye. Anesthetized cynomolgus monkeys received a single intravitreal injection of brimonidine DDS 400 µg implant before removal of study eyes at days 7, 30, 60, 92, 120, and 150 postimplant (three to four animals per time point) for assay of brimonidine in aqueous humor, vitreous, and retina samples. Brimonidine concentrations in the human eye were modeled using a linear, three-compartment model assuming bidirectional distribution to/from the aqueous humor and retina and elimination from the aqueous humor. Monkey tissue volumes were scaled up to human values; intercompartmental and elimination rate constants were assumed to be identical in the two species. Modeling and simulations were performed using NONMEM v. 7.3, R 3.5.1. Brimonidine exposure was highest in the monkey vitreous and retina; concentrations in the central (macula) and peripheral retina were maintained at high levels (>100 ng/g) for 3 to 4 months. Simulated brimonidine concentration-time profiles in human macula indicated that brimonidine DDS 400 µg implant would deliver effective drug concentrations (20.7‒82.2 ng/g, based on animal pharmacology) for approximately 3 months. Accordingly, administration of the 400 µg implant at 3-month intervals is recommended. SIGNIFICANCE STATEMENT: Brimonidine, an α ₂-adrenoceptor agonist, is cyto- and neuroprotective in animal models of retinal/optic nerve injury. Brimonidine Posterior Segment Drug Delivery System (brimonidine DDS) is an intravitreal sustained-release implant with potential ophthalmological applications. This study explores the pharmacokinetics of brimonidine DDS 400 µg implant in the monkey eye and uses compartmental modeling to predict human ocular tissue exposure. Targeted retinal brimonidine delivery from vitreous was demonstrated in monkeys. Simulated tissue concentration-time profiles indicated persistence of pharmacologically effective brimonidine concentrations for ≈3 months in human retina.

Treatments for dry age-related macular degeneration: therapeutic avenues, clinical trials and future directions

Age-related macular degeneration (AMD) is the leading cause of irreversible blindness in the developed world. The identification of the central role of vascular endothelial growth factor (VEGF) in the pathogenesis of neovascular AMD and the introduction of anti-VEGF agents as gold-standard treatment, have drastically changed its prognosis-something yet to be seen in dry AMD. Several therapeutic avenues with a wide variability of targets are currently being investigated in dry AMD. The approaches being investigated to reduce the rate of disease progression include, (1) drugs with antioxidative properties, (2) inhibitors of the complement cascade, (3) neuroprotective agents, (4) visual cycle inhibitors, (5) gene therapy and (6) cell-based therapies. A number of early phase clinical trials have provided promising results, with many more ongoing and anticipated in the near future. In this review, we aim to provide an update of the interventional trials to date and future prospects for the treatment of dry AMD.

The Role of Adrenoceptors in the Retina

The retina is a part of the central nervous system, a thin multilayer with neuronal lamination, responsible for detecting, preprocessing, and sending visual information to the brain. Many retinal diseases are characterized by hemodynamic perturbations and neurodegeneration leading to vision loss and reduced quality of life. Since catecholamines and respective bindings sites have been characterized in the retina, we systematically reviewed the literature with regard to retinal expression, distribution and function of alpha₁ (α₁)-, alpha₂ (α₂)-, and beta (β)-adrenoceptors (ARs). Moreover, we discuss the role of the individual adrenoceptors as targets for the treatment of retinal diseases.

Emerging Drug Therapies for Inherited Retinal Dystrophies

Worldwide, 1 in 2000 people suffer from inherited retinal dystrophies (IRD). Individuals with IRD typically present with progressive vision loss that ultimately results in blindness. Unfortunately, effective treatment options are not widely available due to the genetic and clinical heterogeneity of these diseases. There are multiple gene, cell, and drug-based therapies in various phases of clinical trials for IRD. This mini-review documents current progress made in drug-based clinical trials for treating IRD.

Systematic Review of Randomized Clinical Trials on Safety and Efficacy of Pharmacological and Nonpharmacological Treatments for Retinitis Pigmentosa

Aims. Several treatments have been proposed to slow down progression of Retinitis pigmentosa (RP), a hereditary retinal degenerative condition leading to severe visual impairment. The aim of this study is to systematically review data from randomized clinical trials (RCTs) evaluating safety and efficacy of medical interventions for the treatment of RP. Methods. Randomized clinical trials on medical treatments for syndromic and nonsyndromic RP published up to December 2014 were included in the review. Visual acuity, visual field, electroretinogram, and adverse events were used as outcome measures. Results. The 19 RCTs included in this systematic review included trials on hyperbaric oxygen delivery, topical brimonidine tartrate, vitamins, docosahexaenoic acid, gangliosides, lutein, oral nilvadipine, ciliary neurotrophic factor, and valproic acid. All treatments proved safe but did not show significant benefit on visual function. Long term supplementation with vitamin A showed a significantly slower decline rate in electroretinogram amplitude. Conclusions. Although all medical treatments for RP appear safe, evidence emerging from RCTs is limited since they do not present comparable results suitable for quantitative statistical analysis. The limited number of RCTs, the poor clinical results, and the heterogeneity among studies negatively influence the strength of recommendations for the long term management of RP patients.

Effect of short-term oral valproic Acid on vision and visual field in retinitis pigmentosa

Introduction

The aim of this study was to evaluate the effect of short-term oral valproic acid (VPA) on the vision and visual fields of patients with retinitis pigmentosa (RP).

Methods

In this prospective, nonrandomized trial, 10 patients (20 eyes) with established RP were treated with oral VPA 500 mg/day for 3 months. Visual acuity was monitored using the Snellen chart and values were converted into Early Treatment Diabetic Retinopathy Study chart and logarithm of the minimum angle of resolution (logMAR) equivalents. Visual field changes were evaluated using the Humphrey visual field analyzer (30-2 SITA standard test protocol).

Results

Mean visual acuity was significantly improved from a pretreatment value of 20/72 (logMAR 0.560 ± 0.488) to 20/65 (logMAR 0.513 ± 0.422) after 3 months of treatment (P = 0.006). Vision improved by at least one line or more than one line in 10 eyes, and remained stable in the other 10 eyes. Visual field improvement was noted in nine eyes (P < 0.05, χ² test), nine showing no significant field change and in two visual fields could not be recorded due to poor vision.

Conclusion

Short-term (3-month) treatment with VPA improves the vision and visual field of patients with RP.

Nidek MP1 is able to detect subtle decline in function in inherited and age-related atrophic macular disease with stable visual acuity

PURPOSE

To investigate whether the Nidek MP1 microperimeter (NAVIS software Version 1.7; Nidek Technologies, Padua, Italy) can detect functional decline in progressive atrophic macular disease with stable visual acuity.

METHODS

Nine eyes of nine patients with stable acuity but progressive inherited or age-related atrophic macular disease evident on fundus autofluorescence imaging were reviewed. Each patient underwent 3 consecutive microperimetry tests at baseline, 6 months, and 12 months. Acuity, fixation, and microperimetry tests were performed at each visit. Changes in acuity, fixation stability, and macular sensitivity were analyzed. To detect regional change in retinal sensitivity, the test grid was divided into clusters based on either topographical or functional features. The mean sensitivities within each zone were also compared across the three visits.

RESULTS

In this cohort, there was no significant change in visual acuity, fixation stability, and macular sensitivity over 1 year. However, significant decline in mean sensitivity within the central macula and test loci adjacent to dense scotoma was found (P = 0.004 and 0.002, respectively). In contrast, mean sensitivity elsewhere remained stable.

CONCLUSION

The MP1 can detect significant change in regional retinal sensitivity within 12 months in patients with progressive atrophic macular disease and stable acuity. Individualized analysis of regional sensitivity may be a useful method for quantifying microperimetry.

The effect of brimonidine on transepithelial resistance in a human retinal pigment epithelial cell line

PURPOSE

To investigate the effects of brimonidine, an alpha-2-adrenergic agonist, on barrier function in ARPE-19 cells by measuring transepithelial resistance (TER).

METHODS

ARPE-19 cells were cultured into a confluent monolayer on a microporous filter. Brimonidine was added to the apical medium, and the barrier function of the cells was evaluated by measuring TER. A subset of cells was treated under hypoxic conditions, and the TER changes observed upon administration of brimonidine were compared to those observed in cells in normoxic conditions.

RESULTS

The ARPE cell membrane reached a peak resistance of 29.1+/-7.97 Omegacm(2) after four weeks of culture. The TER of the cells treated under normoxic conditions increased with brimonidine treatment; however, the TER of the cells treated under hypoxic conditions did not change following the administration of brimonidine.

CONCLUSIONS

Barrier function in ARPE-19 cells increased with brimonidine treatment. Understanding the exact mechanism of this barrier function change requires further investigation.