Efficacy and safety of topical difluprednate in persistent diabetic macular edema

Retinal Diseases: The Next Frontier in Pharmacodelivery

The future continuous growth of the global older population augments the burden of retinal diseases worldwide. Retinal characteristics isolating and protecting the sensitive neuro-retina from the rest of the ocular tissues challenge drug delivery and promote research and development toward new horizons. In this review, we wish to describe the unmet medical needs, discuss the novel modes of delivery, and disclose to the reader a spectrum of older-to-novel drug delivery technologies, innovations, and the frontier of pharmacodelivery to the retina. Treating the main retinal diseases in the everlasting war against blindness and its associated morbidity has been growing steadily over the last two decades. Implants, new angiogenesis inhibitor agents, micro- and nano-carriers, and the anchored port delivery system are becoming new tools in this war. The revolution and evolution of new delivery methods might be just a few steps ahead, yet its assimilation in our daily clinical work may take time, due to medical, economical, and regulatory elements that need to be met in order to allow successful development and market utilization of new technologies. Therefore, further work is warranted, as detailed in this Pharmaceutics Special Issue.

Risk of Elevated Intraocular Pressure With Difluprednate in Patients With Non-Infectious Uveitis

PURPOSE

To evaluate the risk factors associated with clinically important intraocular pressure (IOP) elevation with topical difluprednate treatment in patients with non-infectious uveitis.

DESIGN

Retrospective cohort study.

METHODS

Fifty-four eyes of 54 patients with non-infectious uveitis treated with topical difluprednate at the current institution were included. Demographics and clinical characteristics of uveitis patients were collected. The main outcome measure was development of clinically important IOP elevation defined as IOP ≥21 mmHg and an increase of ≥10 mmHg from baseline.

RESULTS

A clinically important IOP elevation was observed in 17 patients (31.5%). The mean time to clinically important IOP elevation was 7.4±4.8 weeks (range 3-19). Statistically significant risk factors for incident clinically important IOP elevation were being a child (adjusted hazard ratio [aHR] 7.85 [95% CI 1.48-41.56], P = .02) and concurrent use of systemic steroids (aHR 5.31 [95% CI 1.18-24.00], P = .03). Patients with concurrent systemic corticosteroids developed clinically important IOP elevation earlier than those without systemic corticosteroid (mean 5.7±3.4 [range 3-14] vs 10.4±5.7 [range 4-19] weeks, P = .05). Incident IOP ≥30 mmHg occurred in 7 patients (13.0%). All patients responded well to the cessation of difluprednate and/or use of topical antiglaucomatous agents and no eyes required glaucoma surgery.

CONCLUSIONS

This study demonstrated that clinically important IOP elevation is common in uveitis patients with topical difluprednate treatment. Children and patients with concurrent systemic corticosteroids are at substantial risk of developing clinically important IOP elevation.

Topical treatment of diabetic retinopathy: a systematic review

Diabetic retinopathy (DR) is the most common microvascular complication in diabetes and may cause severe visual impairment. Until late stages of DR, treatment options are limited. The aim of the present review was to investigate whether changes of DR might be influenced by topical treatment with eye drops. This systematic review included both randomized and non-randomized human clinical studies on the subject. A systematic search of PubMed Medline, Embase and Scopus databases yielded 710 studies. No inclusion criteria regarding classification of DR were defined. Reference lists as well as first authors were screened for the inclusion of additional studies. Potential bias of the randomized studies was assessed using the Cochrane Risk of Bias tool. Nineteen studies suitable for inclusion were identified. Seven studies were randomized trials. These examined 11 different pharmacological groups of drugs in DR. A favourable effect of corticosteroid eye drops in diabetic macular oedema (DMO) was reported in four studies, and another study reported a positive trend. Eye drops with non-steroidal anti-inflammatory drugs were also reported to have a favourable effect in DMO, but not in non-center involving DMO. Application of neuroprotective agents was found effective in patients with pre-existing neurodegeneration in three studies. The remaining studies of DMO and DR were heterogeneous in both designs and results. Studies on treatment of DR with topical eye drops vary with regards to patient population, interventional drugs, study design, and outcome measures. Treatment of DR with eye drops was found effective in the aforementioned cases, but there is still a need for further investigations of long-term, randomized controlled trials in any of the reported pharmacological group.

Topical drug delivery to the retina: obstacles and routes to success

INTRODUCTION

Retinal diseases are one of the main reasons for vision loss where all available drug treatments are based on invasive drug administration such as intravitreal injections. Despite huge efforts and some promising results in animal models, almost all delivery technologies tested have failed in human trials. There are however examples of clinically effective topical delivery systems such as fast dissolving aqueous eye drop suspensions.

AREAS COVERED

Six obstacles to topical drug delivery to the eye have been identified and discussed in some details. These obstacles consist of static membrane barriers to drug permeation into the eye, dynamic barriers such as the lacrimal drainage and physiochemical barriers such as low thermodynamic activity. It is explained how and why these obstacles hamper drug permeation and how different technologies, both those that are applied in marketed drug products and those that are under investigation, have addressed these obstacles.

EXPERT OPINION

The reason that most topical drug delivery systems have failed to deliver therapeutic drug concentrations to the retina is that they do not address physiochemical barriers such as the thermodynamic activity of the permeating drug molecules. Topical drug delivery to the retina has only been successful when the static, dynamic, and physiochemical barriers are addressed simultaneously.

The Emerging Role of Topical Ocular Drugs to Target the Posterior Eye

The prevalence of chronic fundus diseases is increasing with the aging of the general population. The treatment of these intraocular diseases relies on invasive drug delivery because of the globular structure and multiple barriers of the eye. Frequent intraocular injections bring heavy burdens to the medical care system and patients. The use of topical drugs to treat retinal diseases has always been an attractive solution. The fast development of new materials and technologies brings the possibility to develop innovative topical formulations. This article reviews anatomical and physiological barriers of the eye which affect the bioavailability of topical drugs. In addition, we summarize innovative topical formulations which enhance the permeability of drugs through the ocular surface and/or extend the drug retention time in the eye. This article also reviews the differences of eyes between different laboratory animals to address the translational challenges of preclinical models. The fast development of in vitro eye models may provide more tools to increase the clinical translationality of topical formulations for intraocular diseases. Clinical successes of topical formulations rely on continuous and collaborative efforts between different disciplines.

Recent trends in drug-delivery systems for the treatment of diabetic retinopathy and associated fibrosis

Diabetic retinopathy is a frequent microvascular complication of diabetes and a major cause of visual impairment. In advanced stages, the abnormal neovascularization can lead to fibrosis and subsequent tractional retinal detachment and blindness. The low bioavailability of the drugs at the target site imposed by the anatomic and physiologic barriers within the eye, requires long term treatments with frequent injections that often compromise patient's compliance and increase the risk of developing more complications. In recent years, much effort has been put towards the development of new drug delivery platforms aiming to enhance their permeation, to prolong their retention time at the target site and to provide a sustained release with reduced toxicity and improved efficacy. This review provides an overview of the etiology and pathophysiology of diabetic retinopathy and current treatments. It addresses the specific challenges associated to the different ocular delivery routes and provides a critical review of the most recent developments made in the drug delivery field.

The Evolving Treatment of Diabetic Retinopathy

Purpose

To review the current therapeutic options for the management of diabetic retinopathy (DR) and diabetic macular edema (DME) and examine the evidence for integration of laser and pharmacotherapy.

Methods

A review of the PubMed database was performed using the search terms diabetic retinopathy, diabetic macular edema, neovascularization, laser photocoagulation, intravitreal injection, vascular endothelial growth factor (VEGF), vitrectomy, pars plana vitreous surgery, antiangiogenic therapy. With additional cross-referencing, this yielded 835 publications of which 301 were selected based on content and relevance.

Results

Many recent studies have evaluated the pharmacological, laser and surgical therapeutic strategies for the treatment and prevention of DR and DME. Several newer diagnostic systems such as optical coherence tomography (OCT), microperimetry, and multifocal electroretinography (mfERG) are also assisting in further refinements in the staging and classification of DR and DME. Pharmacological therapies for both DR and DME include both systemic and ocular agents. Systemic agents that promote intensive glycemic control, control of dyslipidemia and antagonists of the renin-angiotensin system demonstrate beneficial effects for both DR and DME. Ocular therapies include anti-VEGF agents, corticosteroids and nonsteroidal anti-inflammatory drugs. Laser therapy, both as panretinal and focal or grid applications continue to be employed in management of DR and DME. Refinements in laser devices have yielded more tissue-sparing (subthreshold) modes in which many of the benefits of conventional continuous wave (CW) lasers can be obtained without the adverse side effects. Recent attempts to lessen the burden of anti-VEGF injections by integrating laser therapy have met with mixed results. Increasingly, vitreoretinal surgical techniques are employed for less advanced stages of DR and DME. The development and use of smaller gauge instrumentation and advanced anesthesia agents have been associated with a trend toward earlier surgical intervention for diabetic retinopathy. Several novel drug delivery strategies are currently being examined with the goal of decreasing the therapeutic burden of monthly intravitreal injections. These fall into one of the five categories: non-biodegradable polymeric drug delivery systems, biodegradable polymeric drug delivery systems, nanoparticle-based drug delivery systems, ocular injection devices and with sustained release refillable devices. At present, there remains no one single strategy for the management of the particular stages of DR and DME as there are many options that have not been rigorously tested through large, randomized, controlled clinical trials.

Conclusion

Pharmacotherapy, both ocular and systemic, will be the primary mode of intervention in the management of DR and DME in many cases when cost and treatment burden are less constrained. Conventional laser therapy has become a secondary intervention in these instances, but remains a first-line option when cost and treatment burden are more constrained. Results with subthreshold laser appear promising but will require more rigorous study to establish its role as adjunctive therapy. Evidence to support an optimal integration of the various treatment options is lacking. Central to the widespread adoption of any therapeutic regimen for DR and DME is substantiation of safety, efficacy, and cost-effectiveness by a body of sound clinical trials.

Difluprednate for the Treatment of Uveitic Cystoid Macular Edema

PURPOSE

To describe clinical outcomes associated with the use of topical difluprednate in treating uveitic cystoid macular edema.

DESIGN

Retrospective, interventional case series.

METHODS

Setting: Medical record review in a tertiary care uveitis center.

PATIENT POPULATION

Fifty-eight patients (72 eyes) with uveitic cystoid macular edema (CME) treated with difluprednate 0.05% ophthalmic solution between June 2012 and May 2016.

MAIN OUTCOME MEASURES

Macular central subfield thickness (CST) determined by optical coherence tomography, improvement of CME (≥20% reduction in CST or resolution), and resolution of CME (CST ≤ 320 μm with no cysts) at 30 days after starting treatment. Outcomes were assessed up to 90 days.

RESULTS

CST on average decreased by 17% (95% CI: -33%, -7%) for eyes using only difluprednate (n = 43) and by 6% (95% CI: -17%, -2%) for eyes in patients using concomitant systemic immunosuppressive therapy (n = 29) at 30 days, a 12% difference between groups (95% CI: 2%, 21%, P = .02). Of eyes on difluprednate alone, 76% had improvement and 48% had resolution of CME. In patients using systemic therapy, 37% of eyes had improvement and 17% had resolution. Eight eyes (11%) had an intraocular pressure (IOP) > 24 mm Hg within the first 30 days. By 90 days, CME had improved in 69% of all eyes and resolved in 43% of eyes, with only 9 patients starting or increasing systemic immunosuppressive medications and 2 patients receiving periocular corticosteroid injections.

CONCLUSIONS

Difluprednate was associated with an improvement in uveitic CME and could be a reasonable first-line therapy. IOP should be closely monitored.

RESOLUTION OF NONINFECTIOUS UVEITIC CYSTOID MACULAR EDEMA WITH TOPICAL DIFLUPREDNATE

PURPOSE

To evaluate the short-term safety and efficacy of topical difluprednate (0.05%) for the treatment of noninfectious uveitic cystoid macular edema.

METHODS

Twenty-seven patients (35 eyes) undergoing treatment with difluprednate 4 times daily for 3 weeks for noninfectious uveitic cystoid macular edema were reviewed for visual acuity, intraocular pressure, optical coherence tomography, and fluorescein angiography results. A mixed model analysis was fit with each measure as the outcome, visit as the primary predictor, and patient and eye as random effects.

RESULTS

Mean central foveal thickness decreased by 117 μm (P < 0.001) at 30 ± 15 days, 124 μm (P < 0.001) at 60 ± 15 days, and 152 μm (P < 0.001) at 180 ± 30 days. Complete resolution of intraretinal fluid was observed in 15 of 34 (44%) eyes at 30 ± 15 days, 11 of 21 (52%) eyes at 60 ± 15 days, and 9 of 12 (75%) eyes at 180 ± 30 days. Improvement in fluorescein leakage was noted in 7 of 8 eyes (88%). Visual acuity improved by a mean of 5 letters (P = 0.001) at 30 ± 15 days, 5.5 letters (P = 0.007) at 60 ± 15 days, and 7 letters (P = 0.032) at 180 ± 30 days. Mean increase in intraocular pressure was 1.48 mmHg at 30 ± 15 days (P = 0.080), 1.92 mmHg at 60 ± 15 days (P = 0.110), and 6.18 mmHg (P = 0.001) at 180 ± 30 days.

CONCLUSION

Topical difluprednate is a well-tolerated and effective treatment for noninfectious uveitic cystoid macular edema with decreased central foveal thickness, mild improvement in visual acuity, and elevation of intraocular pressure observed in a few patients.

Clinical biomarkers and molecular basis for optimized treatment of diabetic retinopathy: current status and future prospects

Diabetic retinopathy is a highly specific microvascular complication of diabetes and a leading cause of blindness worldwide. It is triggered by hyperglycemia which causes increased oxidative stress leading to an adaptive inflammatory assault to the neuroretinal tissue and microvasculature. Prolonged hyperglycemia causes increased polyol pathway flux, increased formation of advanced glycation end-products, abnormal activation of signaling cascades such as activation of protein kinase C (PKC) pathway, increased hexosamine pathway flux, and peripheral nerve damage. All these changes lead to increased oxidative stress and inflammatory assault to the retina resulting in structural and functional changes. In addition, neuroretinal alterations affect diabetes progression. The most effective way to manage diabetic retinopathy is by primary prevention such as hyperglycemia control. While the current mainstay for the management of severe and proliferative diabetic retinopathy is laser photocoagulation, its role is diminishing with the development of newer drugs including corticosteroids, antioxidants, and antiangiogenic and anti-VEGF agents which work as an adjunct to laser therapy or independently. The current pharmacotherapy of diabetic retinopathy is incomplete as a sole treatment option in view of limited efficacy and short-term effect. There is a definite clinical need to develop new pharmacological therapies for diabetic retinopathy, particularly ones which would be effective through the oral route and help recover lost vision. The increasing understanding of the mechanisms of diabetic retinopathy and its biomarkers is likely to help generate better and more effective medications.