Critical appraisal of the clinical utility of the dexamethasone intravitreal implant (Ozurdex) for the treatment of macular edema related to branch retinal vein occlusion or central retinal vein occlusion

Transscleral Delivery of Dexamethasone-Loaded Microparticles Using a Dissolving Microneedle Array

Microneedles (MNs) have attracted considerable interest as a means of ocular drug delivery, a challenging delivery route due to the limitations imposed by the various biological barriers associated with this organ. In this study, a novel ocular drug delivery system was developed by formulating a dissolvable MN array containing dexamethasone-loaded PLGA microparticles for scleral drug deposition. The microparticles serve as a drug reservoir for controlled transscleral delivery. The MNs displayed sufficient mechanical strength to penetrate the porcine sclera. Dexamethasone (Dex) scleral permeation was significantly higher than in topically instilled dosage forms. The MN system was able to distribute the drug through the ocular globe, with 19.2% of the administered Dex detected in the vitreous humour. Additionally, images of the sectioned sclera confirmed the diffusion of fluorescent-labelled microparticles within the scleral matrix. The system therefore represents a potential approach for minimally invasive Dex delivery to the posterior of the eye, which lends itself to self-administration and hence high patient convenience.

Considerations for Polymers Used in Ocular Drug Delivery

PURPOSE

Age-related eye diseases are becoming more prevalent. A notable increase has been seen in the most common causes including glaucoma, age-related macular degeneration (AMD), and cataract. Current clinical treatments vary from tissue replacement with polymers to topical eye drops and intravitreal injections. Research and development efforts have increased using polymers for sustained release to the eye to overcome treatment challenges, showing promise in improving drug release and delivery, patient experience, and treatment compliance. Polymers provide unique properties that allow for specific engineered devices to provide improved treatment options. Recent work has shown the utilization of synthetic and biopolymer derived biomaterials in various forms, with this review containing a focus on polymers Food and Drug Administration (FDA) approved for ocular use.

METHODS

This provides an overview of some prevalent synthetic polymers and biopolymers used in ocular delivery and their benefits, brief discussion of the various types and synthesis methods used, and administration techniques. Polymers approved by the FDA for different applications in the eye are listed and compared to new polymers being explored in the literature. This article summarizes research findings using polymers for ocular drug delivery from various stages: laboratory, preclinical studies, clinical trials, and currently approved. This review also focuses on some of the challenges to bringing these new innovations to the clinic, including limited selection of approved polymers.

RESULTS

Polymers help improve drug delivery by increasing solubility, controlling pharmacokinetics, and extending release. Several polymer classes including synthetic, biopolymer, and combinations were discussed along with the benefits and challenges of each class. The ways both polymer synthesis and processing techniques can influence drug release in the eye were discussed.

CONCLUSION

The use of biomaterials, specifically polymers, is a well-studied field for drug delivery, and polymers have been used as implants in the eye for over 75 years. Promising new ocular drug delivery systems are emerging using polymers an innovative option for treating ocular diseases because of their tunable properties. This review touches on important considerations and challenges of using polymers for sustained ocular drug delivery with the goal translating research to the clinic.

Biotechnology and Biomaterial-Based Therapeutic Strategies for Age-Related Macular Degeneration. Part I: Biomaterials-Based Drug Delivery Devices

Age-related Macular Degeneration (AMD) is an up-to-date untreatable chronic neurodegenerative eye disease of multifactorial origin, and the main causes of blindness in over 65 years old people. It is characterized by a slow progression and the presence of a multitude of factors, highlighting those related to diet, genetic heritage and environmental conditions, present throughout each of the stages of the illness. Current therapeutic approaches, mainly consisting of intraocular drug delivery, are only used for symptoms relief and/or to decelerate the progression of the disease. Furthermore, they are overly simplistic and ignore the complexity of the disease and the enormous differences in the symptomatology between patients. Due to the wide impact of the AMD and the up-to-date absence of clinical solutions, the development of biomaterials-based approaches for a personalized and controlled delivery of therapeutic drugs and biomolecules represents the main challenge for the defeat of this neurodegenerative disease. Here we present a critical review of the available and under development AMD therapeutic approaches, from a biomaterials and biotechnological point of view. We highlight benefits and limitations and we forecast forthcoming alternatives based on novel biomaterials and biotechnology methods. In the first part we expose the physiological and clinical aspects of the disease, focusing on the multiple factors that give origin to the disorder and highlighting the contribution of these factors to the triggering of each step of the disease. Then we analyze available and under development biomaterials-based drug-delivery devices (DDD), taking into account the anatomical and functional characteristics of the healthy and ill retinal tissue.

Manufacturing of Dexamethasone-Poly(d,l-Lactide-co-Glycolide) Implants Using Hot-Melt Extrusion: Within- and Between-Batch Product Performance Comparisons

Purpose: Reliable drug therapy with injectable intravitreal implants requires implants of consistent quality. The purpose of this study was to prepare dexamethasone-poly(d,l-lactide-co-glycolide) (PLGA) biodegradable implants and assess implant quality within and between batches for different polymer compositions. Methods: Implants containing 20% w/w dexamethasone with 3 theoretical rates of release (fast, intermediate, and slow) were manufactured with decreasing proportion of acid-terminated PLGA (50:50) and increasing proportion of ester-terminated PLGA (50:50) in a batch process using hot-melt extrusion. The implants were manufactured without and with in-process modification of extrusion/conveyor speed in the late phase of each batch. Implant samples collected at early, middle, and late phases of each batch were analyzed for diameter, drug loading, mechanical properties (strength and toughness), and drug release. Results: With a fixed process, unlike a modified process with an increase in extrusion speed and reduction of conveyor speed in the late phase, all implant formulations tended to decrease in diameter and mechanical properties in the late phase. Drug release profiles for the intermediate and slow release compositions were similar with or without process modification, unlike the fast release composition. Addition of ester-terminated PLGA resulted in a slower drug release. When all formulations are grouped together, the implant diameter exhibited a moderate correlation with mechanical properties, but no correlation was observed with drug release. Conclusions: Within a hot-melt extrusion batch process, the dexamethasone-PLGA implant diameter and hence toughness and strength tend to decline in the latter phase. In-process adjustment of extrusion and conveyor speeds can improve batch consistency and, potentially, implant integrity or performance during or after injection. Process changes did not affect drug release for 2 of the 3 implant compositions.

Analysis of Morphologic and Functional Outcomes in Macular Edema due to Central Retinal Vein Occlusion Treated with Intravitreal Dexamethasone Implant

Purpose

To analyze anatomic and functional retinal changes and their correlation after intravitreal dexamethasone implant (DEX implant) in patients with central retinal vein occlusion- (CRVO-) related macular edema (ME) using optical coherence tomography and microperimetry.

Methods

Fifteen treatment-naïve patients with functional impairment due to CRVO-related ME were enrolled in this prospective interventional case series. Main outcomes were best-corrected visual acuity (BCVA), retinal sensitivity (RS), and central retinal thickness (CRT). Secondary outcomes were ellipsoid zone (EZ) status and fixation behaviour. All patients underwent DEX implant and were retreated according to predefined criteria. Data were prospectively recorded at baseline and at month 1, 3, 6, 9, and 12. Correlation between main outcomes was analyzed.

Results

Fifteen eyes of 15 patients (9 men, 6 women; mean age 61.8 ± 10.9 years) were included. BCVA and CRT significantly improved at all follow-up visits, while RS significantly improved at 3, 6, 9, and 12 months. EZ status and fixation behaviour did not change significantly. Baseline CRT had a significant negative correlation with BCVA and RS at different follow-up visits (r=−0.52  to −0.63, p ≤ 0.04; r=−0.52, p=0.04; resp.). At all time points, there was not a significant correlation between CRT and BCVA and RS, while RS and BCVA showed a significant correlation, increasing over time (r=−0.72  to −0.89; p < 0.001).

Conclusion

DEX implant led to a significant morphofunctional improvement. Baseline CRT is predictive of changes of functional outcomes whose correlation increases over time after treatment.

Intravitreal therapeutic agents in noninfectious uveitic macular edema

The management of uveitis is challenging for most treating ophthalmologists. The treatment of uveitis often requires the use of high dose of systemic corticosteroid and immunosuppressive agents, which are almost always associated with potential side effects. Intravitreal medications have become a popular mode of drug administration in uveitis patients as they provide high volume of drug to the target tissues, eliminating the risk of systemic toxicity. There has been tremendous development in the intravitreal therapeutics over the last few years. With the advent of sustained-release technique, increasing patient compliance, biodegradable nature of the implant, and introduction of newer agents with better safety profile, the intravitreal medications have become more popular in recent years. This review presents evidence in the scientific literature supporting the use of intravitreal medications for the management of uveitis and its complications.

Drug-resistant coagulase-negative staphylococcal endophthalmitis following dexamethasone intravitreal implant

A 60-year-old female came to our hospital with defective vision due to persistent diabetic macular edema and was treated with intravitreal ozurdex implant in the right eye. Three days later, the patient presented with diminution of vision, ocular pain, congestion, and hypopyon with no fundus view. B-scan ultrasonography showed vitritis, and diagnosis of endophthalmitis was made. Subsequently, 25-gauge pars plana vitrectomy was performed along with intravitreal vancomycin and amikacin and removal of implant. On culture, there was growth of coagulase-negative staphylococcus which was resistant to ofloxacin antibiotic. A week following treatment, there was significant improvement in the patient's sign and symptoms with improvement in vision. Our case demonstrated that acute endophthalmitis can occur following dexamethasone intravitreal implant.

The clinical outcomes of surgical management of anterior chamber migration of a dexamethasone implant (Ozurdex®)

PURPOSE

Our purpose was to describe the clinical course, and individualized management approaches, of patients with migration of a dexamethasone implant into the anterior chamber.

METHODS

This was a retrospective review of four patients with seven episodes of anterior chamber migration of a dexamethasone implant.

RESULTS

After 924 intravitreal dexamethasone injections, anterior migration of the implant occurred in four eyes of four patients (0.43%). All four eyes were pseudophakic: one eye had a posterior chamber intraocular lens in the capsular bag but in a post-laser posterior capsulotomy state, two eyes had a sulcus intraocular lens (IOL), and one eye had an iris-fixated retropupillary IOL. All eyes had a prior vitrectomy and no lens capsule. The time interval from injection to detection of the implant migration ranged from 2 to 6 weeks. Of the four eyes with corneal edema, only one eye required a corneal transplantation, although it was unclear whether the implant migration was the direct cause of the corneal decompensation because the patient had a history of bullous keratopathy resulting from an extended history of uveitis. All patients underwent surgical intervention: two patients with a repositioning procedure, and the other two patients with removal due to repeated episodes, although surgical removal was not always necessary to reverse the corneal complications.

CONCLUSIONS

In our study, not all patients required surgical removal of the implants. Repositioning the implant back into the vitreous cavity may be considered as an option in cases involving the first episode with no significant corneal endothelial decompensation. Considering potential anterior segment complications and the loss of drug effectiveness together, an individualized approach is recommended to obtain the best treatment outcomes and to minimize the risk of corneal complications.

New Drugs and New Posterior Delivery Methods in CME

PURPOSE

To discuss the characteristics, indications and adverse events (AEs) of sustained-release corticosteroid devices for the treatment of cystoid macular edema (CME).

RECENT FINDINGS

Ozurdex® is approved for the treatment of diabetic macular edema (DME), retinal vein occlusion related-CME and noninfectious posterior uveitis (NIPU). It releases dexamethasone over a maximum period of 6 months making repeated intravitreal injections necessary for recurrent CME. Iluvien® releases fluocinolone for up to 36 months and is effective for the treatment of chronic DME. Retisert® (Bausch & Lomb, Rochester, NY) also releases fluocinolone, and is approved for chronic NIPU. Both Iluvien® and Retisert® are non-biodegradable devices and are highly associated with cataract and glaucoma.

SUMMARY

Long-acting intraocular corticosteroid formulations offer a more predictable drug-release profile and reduced dosing frequency in comparison to conventional formulations of the same compounds but the risk-benefit ratio must be taken into consideration previous to the implantation of those devices.

Intraocular pressure elevation after intravitreal triamcinolone acetonide injection: a Meta-analysis

AIM

To report on intraocular pressure (IOP) after intravitreal injections of triamcinolone acetonide.

METHODS

Systematic literature review of studies that investigated the effects of an injection of triamcinolone intravitreal triamcinolone acetonide on IOP was conducted according to the Cochrane Collaboration methodology and the reported effects have been analyzed with Meta-analysis.

RESULTS

We found that the IOP follows an inverted-U shape pattern over time starting with an average value of 14.81±1.22 mm Hg before the injection, rising to a maximum of 19.48±2.15 mm Hg after one month of injection and falling down to 16.16±1.92 mm Hg after 6mo. Moreover, country of study, age, previous history of glaucoma and gender compositions matter for cross-study were different in reported IOP changes.

CONCLUSION

Our findings may be helpful in determining pressure elevation risk of intravitreal triamcinolone acetonide therapy as well as comparing it with those of more recent therapies such as the anti-vascular endothelial growth factor agents.

Nanoengineering of therapeutics for retinal vascular disease

Retinal vascular diseases, including diabetic retinopathy, neovascular age related macular degeneration, and retinal vein occlusion, are leading causes of blindness in the Western world. These diseases share several common disease mechanisms, including vascular endothelial growth factor (VEGF) signaling, hypoxia, and inflammation, which provide opportunities for common therapeutic strategies. Treatment of these diseases using laser therapy, anti-VEGF injections, and/or steroids has significantly improved clinical outcomes. However, these strategies do not address the underlying root causes of pathology, and may have deleterious side effects. Furthermore, many patients continue to progress toward legal blindness despite receiving regular therapy. Nanomedicine, the engineering of therapeutics at the 1-100 nm scale, is a promising approach for improving clinical management of retinal vascular diseases. Nanomedicine-based technologies have the potential to revolutionize the treatment of ophthalmology, through enabling sustained release of drugs over several months, reducing side effects due to specific targeting of dysfunctional cells, and interfacing with currently "undruggable" targets. We will discuss emerging nanomedicine-based applications for the treatment of complications associated with retinal vascular diseases, including angiogenesis and inflammation.

Sustained-release corticosteroid options

Sustained-release corticosteroid treatment has shown to be a promising strategy for macular edema due to retinovascular disease (i.e., diabetes and retinal vein occlusion) and for the treatment of noninfectious posterior uveitis. Clinicians now have the option of three sustained-release corticosteroid implants: Ozurdex (Allergan Inc., Irvine, CA) which releases dexamethasone and two devices that release fluocinolone acetonide, Retisert (Bausch & Lomb, Rochester, NY), and Iluvien (Alimera Science, Alpharetta, GA). Each has different physical characteristics and duration effect and has been approved for different indications. Herein we provide a summary of the current clinical knowledge regarding these implants.

Intravitreal bevacizumab (Avastin) versus triamcinolone (Volon A) for treatment of diabetic macular edema: one-year results

PURPOSE

The objective was to compare retinal morphology and function following intravitreal injections of bevacizumab (Avastin) or triamcinolone (Volon A) in patients with early diabetic macular edema (DME).

PATIENTS AND METHODS

The study was planned as a randomized, prospective, interventional clinical trial. A total of 30 diabetic patients with treatment-naïve, clinically significant macular edema were included in this study and randomized to two equal groups. One group initially received three injections of 2.5 mg bevacizumab in monthly intervals. The second group received a single injection of 8 mg triamcinolone, followed by two sham interventions. Functional and anatomic results were evaluated monthly using ETDRS vision charts and spectral-domain optical coherence tomography. According to the study protocol, retreatment after 3 months was dependent on functional and anatomic outcome in a PRN regimen.

RESULTS

Baseline best corrected visual acuity (BCVA) was 0.30 logMAR and central retinal subfield thickness (CSRT) was 505 μm in the bevacizumab group and 0.32 logMAR and 490 μm CSRT in the triamcinolone group. After 3 months, BCVA improved to 0.23 logMAR (bevacizumab) and 358 μm CRST and 0.26 logMAR (triamcinolone) and 308 μm CSRT. After 12 months, BCVA further recovered in the bevacizumab group (0.18 logMAR) but slightly decreased in the triamcinolone group (0.36 logMAR).

CONCLUSION

Intravitreal bevacizumab and triamcinolone are both equally effective in reducing CSRT in early DME. After 6 months, rehabilitation of vision was comparable in both treatment arms, whereas at the final follow-up at month 12, BCVA was superior in the bevacizumab than in the triamcinolone sample. This may be related to cataract development following steroid treatment, as well as to substance-specific mechanisms within the angiogenic versus the inflammatory cascade.

Acute-Onset Endophthalmitis Caused by Alloiococcus otitidis following a Dexamethasone Intravitreal Implant

PURPOSE

To report the first case of acute endophthalmitis caused by Alloiococcus otitidis after a dexamethasone intravitreal implant.

METHODS

A 74-year-old female was treated with intravitreal Ozurdex(®) in her left eye for central retinal vein occlusion (CRVO). Best-corrected visual acuity (BCVA) in the eye was 4/20. Intravitreal injection was uneventful. At 48 h after injection, she developed ocular pain and visual acuity had dropped to light perception. Endophthalmitis associated with intravitreal injection was suspected.

RESULTS

The patient did not show a favorable clinical response following systemic, intravitreal, and topical fortified antibiotics. We then performed a vitreous biopsy and removed the Ozurdex implant by pars plana vitrectomy. A vitreous culture was positive for A. otitidis. At the 2-month follow up, no inflammation was observed, but due to CRVO and probably aggravated by endophthalmitis, the fundus showed macular fibrosis. The final BCVA was finger counting at 30 cm in her left eye.

CONCLUSIONS

In cases of an intravitreal implant associated with endophthalmitis, we recommend removal of the device because it may act as a permanent reservoir of organisms if it remains in the vitreous cavity.

Therapeutic potential of intravitreal pharmacotherapy in retinal vein occlusion

Retinal vein occlusion (RVO) is the most common visually disabling disease affecting the retina after diabetic retinopathy. Although the disease entity has long been known, its management is still controversial. Macular edema is the main reason for decreased visual acuity (VA) in this retinal vascular disorder. Recently the vitreous cavity has increasingly been used as a reservoir of drugs for the direct treatment of macular edema through intravitreal injection route. The most widely injected drugs so far have been triamcinolone acetonide (TA) and bevacizumab. The objective of this review is to evaluate the evidence and discuss the rationale behind the recent suggestions that intravitreal pharmacotherapy by corticosteroids and anti-vascular endothelial growth factors may be useful in the treatment of retinal vein occlusion.

Long-term evaluation of patients treated with dexamethasone intravitreal implant for macular edema due to retinal vein occlusion

PURPOSE

To evaluate the long-term visual prognosis and complications of patients who received intravitreal Ozurdex injections for the treatment of macular edema (ME) due to retinal vein occlusion (RVO).

METHODS

A total of 17 patients who received Ozurdex injections in our institution as part of the GENEVA study were recalled for examination. Recorded parameters included final visual acuity (VA), final retinal thickness by optical coherence tomography, persistence of ME, and the occurrence of any complications.

RESULTS

Mean follow-up time was 50.5 months. Patients with branch RVO (BRVO) had a more favorable prognosis than central RVO (CRVO), and their mean VA had improved significantly, whereas the mean VA for the patients with CRVO did not improve significantly. Retinal thickness had reduced significantly in the whole group and in each subgroup separately. Complications included 10 patients with cataract progression, 1 with elevated intraocular pressure, and 1 with neovascularization and vitreous hemorrhage.

CONCLUSIONS

This is the first reported long-term evaluation of patients treated with Ozurdex. Our results indicate that it has favorable long-term safety profile, and may have a beneficial effect on the visual prognosis in BRVO even in the absence of continuous treatment. Further research is required to establish the optimal retreatment schedule for Ozurdex.