Safety and pharmacodynamics of suprachoroidal injection of triamcinolone acetonide as a controlled ocular drug release model

Extracellular vesicle encapsulated nicotinamide delivered via a trans-scleral route provides retinal ganglion cell neuroprotection

The progressive and irreversible degeneration of retinal ganglion cells (RGCs) and their axons is the major characteristic of glaucoma, a leading cause of irreversible blindness worldwide. Nicotinamide adenine dinucleotide (NAD) is a cofactor and metabolite of redox reaction critical for neuronal survival. Supplementation with nicotinamide (NAM), a precursor of NAD, can confer neuroprotective effects against glaucomatous damage caused by an age-related decline of NAD or mitochondrial dysfunction, reflecting the high metabolic activity of RGCs. However, oral supplementation of drug is relatively less efficient in terms of transmissibility to RGCs compared to direct delivery methods such as intraocular injection or delivery using subconjunctival depots. Neither method is ideal, given the risks of infection and subconjunctival scarring without novel techniques. By contrast, extracellular vesicles (EVs) have advantages as a drug delivery system with low immunogeneity and tissue interactions. We have evaluated the EV delivery of NAM as an RGC protective agent using a quantitative assessment of dendritic integrity using DiOlistics, which is confirmed to be a more sensitive measure of neuronal health in our mouse glaucoma model than the evaluation of somatic loss via the immunostaining method. NAM or NAM-loaded EVs showed a significant neuroprotective effect in the mouse retinal explant model. Furthermore, NAM-loaded EVs can penetrate the sclera once deployed in the subconjunctival space. These results confirm the feasibility of using subconjunctival injection of EVs to deliver NAM to intraocular targets.

Effect of suprachoroidal triamcinolone on intraocular pressure: a systematic review and meta-analysis

Background

Triamcinolone acetonide is a synthetic corticosteroid with multiple ocular uses. Like other corticosteroids, it too is associated with ocular side effects such as increased intraocular pressure (IOP), glaucoma and cataracts. Suprachoroidal administration of triamcinolone is hoped to reduce the ocular side effects of the drug, especially rises in IOP. Our systematic review and meta-analysis aims to study this phenomenon.

Objectives

The purpose of this study was to evaluate the effect of suprachoroidal triamcinolone injections on IOP.

Design

Systematic review and meta-analysis.

Methods

We utilized the Medline, Scopus and Cochrane databases for this review. Studies published till June 2023, which fulfilled the eligibility criteria, were included. Studies in the English language with adult participants who were administered suprachoroidal triamcinolone without any concurrent intervention were included, whereas studies that did not report the mean and standard deviation for IOP were excluded. The outcome of interest was IOP at 1, 3 and 6 months post-suprachoroidal triamcinolone injection. IOP values from included studies were extracted onto Review Manager version 5.4 for analysis.

Results

Our search yielded 104 results, from which 22 papers were shortlisted for full-text screening. Finally, 12 studies were included in the analysis. Our analysis suggests a statistically significant increase in IOP in the first month after suprachoroidal triamcinolone injection but no significant differences at 3 and 6 months post-injection as compared to baseline.

Conclusion

Elevated IOP at 1 month post-injection must be considered when using suprachoroidal triamcinolone and adequate safety measures must be taken. However, the absence of a significant rise at 3 and 6 months post-injection indicates that this modality is safer than other existing drug delivery methods.

Trial registration

Registered with the Research Registry with the unique identifying number 'reviewregistry1656.' https://www.researchregistry.com/browse-the-registry#registryofsystematicreviewsmeta-analyses/registryofsystematicreviewsmeta-analysesdetails/648eefe65b6523002995eb21/.

Recent advances in uveitis therapy: focus on selected phase 2 and 3 clinical trials

INTRODUCTION

Uveitis is a heterogeneous group of ocular conditions characterized by inflammation of the uveal tract. It is a leading cause of blindness in developed countries and exerts significant psychological, social, and economic impact on both patients and the larger society. While there are numerous pharmacotherapy options, posterior segment noninfectious uveitis remains a significant challenge to treat due to its severity, chronicity, and high recurrence rates.

AREAS COVERED

The index review highlights the unmet needs of uveitis pharmacotherapy and its research and the shortcomings of existing ocular and systemic therapeutic options for noninfectious uveitis. The more promising novel ocular drug delivery methods and therapeutic targets/drugs are discussed, and evidence from the clinical trials is evaluated.

EXPERT OPINION

There has been incredible growth in the number of treatment options available to uveitis patients today, especially with the new generation of biologic drugs. Available evidence suggests that these newer options may be superior to conventional immunosuppressive therapies in terms of efficacy and side effect profiles. Further high-quality research and additional clinical trials will be needed to clarify their roles in the stepladder treatment approach of noninfectious uveitis.

Ocular pharmacokinetics and toxicity of nanoparticular acetazolamide: In vivo distribution and safety of PHBV-ACZ nanoparticle

Diabetic macular edema (DME) is defined as fluid accumulation in the macular region, between the retinal layers, due to many diseases, especially diabetes. DME is one of the major complications of diabetic retinopathy (DRP). Carbonic anhydrase inhibitors (CAI) are a pharmaceutical agent used in different fields, especially glaucoma treatment. Acetazolamide (ACZ), which is a CAI, is an active substance that has been used off-label for many years in the treatment of macular edema due to diabetes and many other diseases. The low solubility and bioavailability of ACZ limit its use in the treatment of DME. In this study, a nanoparticulate formulation was developed that would increase the solubility and bioavailability of ACZ and allow it to be administered intravitreally. ACZ was loaded on poly(3-hydroxybutyrate-co-3-Hydroxyvalerate) (PHBV) nanoparticles and the loading efficiency was 71.58 ± 1.22%. Toxicity of nanoparticles after intravitreal application was evaluated with anterior segment and posterior segment examination findings, intraocular pressure (IOP) measurements and electrophysiological tests. At the end of the 3-month follow-up, electroretinography (ERG) measurements demonstrated that ACZ loaded PHBV (PHBV-ACZ) nanoparticles did not cause loss of function in retinal cells. On histological examination, rare degenerative changes were observed in several cell groups. In addition, pharmacokinetic studies were performed to determine the tissue distribution of ACZ at various periods. ACZ was identified in vitreous humor and retina at the highest concentration. Based on our results, the prepared nanoparticle formulation can release long-term CAI for DRP therapy and accordingly can reduce the need for monthly intravitreal injections.

Suprachoroidal CLS-TA with and without Systemic Corticosteroid and/or Steroid-Sparing Therapy: A Post-Hoc Analysis of the Phase 3 PEACHTREE Clinical Trial

PURPOSE

To study the efficacy and safety of suprachoroidal CLS-TA (proprietary suspension of triamcinolone acetonide) in uveitic macular edema (UME) with and without concurrent systemic corticosteroid or steroid-sparing therapy (ST).

METHODS

Post hoc analysis of the PEACHTREE phase 3 randomized trial.

RESULTS

Among UME patients receiving no ST, at week 24, mean BCVA change was +15.6 letters in 68 CLS-TA patients versus +4.9 letters in 49 sham-control patients (p < .001), while mean CST change was -169.8 µm versus -10.3 µm, respectively (p < .001). Among patients receiving ST, at week 24, mean BCVA change was +9.4 letters in 28 CLS-TA patients versus -3.2 letters in 15 sham-control patients (p = .019), while mean CST change was -108.3 µm versus -43.5 µm, respectively (p = .190). No SAEs related to treatment were reported.

CONCLUSIONS

A clinically meaningful benefit of CLS-TA was noted in UME patients, regardless of concurrent ST usage.Abbreviation and AcronymsCST = central subfield thickness; BCVA = best corrected visual acuity; ME = macular edemaI; IVT = intravitreal; AE = adverse event; FA = fluocinolone acetonide; SD-OCT = spectral-domain optical coherence tomography; NIU = noninfectious uveitis; SAE = serious adverse event; TEAE = treatment emergent adverse event; ITT = intent to treat; CI = confidence interval.

Refractory post-surgical cystoid macular edema managed following suprachoroidal microcatheterization and delivery of triamcinolone

BACKGROUND

Post-surgical macular edema (ME) is a common cause of prolonged visual impairment. Here we report on the feasibility and clinical outcomes from the use of a novel suprachoroidal microcatheter to treat post-surgical chronic ME by the posterior suprachoroidal placement of a triamcinolone acetonide (TA) suspension.

METHODS

Two patients were catheterized with the Oxulumis suprachoroidal delivery system on two separate occasions starting 5 and 10 mm posterior to the limbus. The catheter only remains in the suprachoroidal space for the time of the drug administration. Visual acuity and spectral domain optical coherence tomography (SD-OCT) changes were followed over several weeks to months to determine the duration of ME resolution.

RESULTS

Suprachoroidal microcatheterization for posterior delivery of triamcinolone was possible in all attempts using the illuminated Oxulumis catheter. No reflux, scleral or choroidal trauma was observed. There was no intraocular pressure rise during the follow-up period. The triamcinolone deposit was visible on infrared imaging and on SD-OCT a choroidal elevation was visible. Both progressively disappeared over time. A rapid resolution of ME associated with improved vision was observed following each injection for 3 to 7 months with a TA dose of 2.4 mg or 4 mg.

CONCLUSIONS

In these patients with poorly responsive ME, posterior suprachoroidal TA led to a visible suprachoroidal drug deposit and prolonged visual improvement. The Oxulumis microcatheterization device performed as expected and was not associated with any complications.

Suprachoroidal Injection: A Novel Approach for Targeted Drug Delivery

Treating posterior segment and retinal diseases poses challenges due to the complex structures in the eye that act as robust barriers, limiting medication delivery and bioavailability. This necessitates frequent dosing, typically via eye drops or intravitreal injections, to manage diseases, often leading to side effects with long-term use. Suprachoroidal injection is a novel approach for targeted drug delivery to the posterior segment. The suprachoroidal space is the region between the sclera and the choroid and provides a potential route for minimally invasive medication delivery. Through a more targeted delivery to the posterior segment, this method offers advantages over other routes of administration, such as higher drug concentrations, increased bioavailability, and prolonged duration of action. Additionally, this approach minimizes the risk of corticosteroid-related adverse events such as cataracts and intraocular pressure elevation via compartmentalization. This review focuses on preclinical and clinical studies published between 2019 and 2023, highlighting the potential of suprachoroidal injection in treating a variety of posterior segment diseases. However, to fully harness its potential, more research is needed to address current challenges and limitations, such as the need for technological advancements, refinement of injection techniques, and consideration of cost and accessibility factors. Future studies exploring its use in conjunction with biotech products, gene therapies, and cell-based therapies can lead to personalized treatments that can revolutionize the field of ophthalmology.

Alternative application of an iTrack microcatheter and canaloplasty: case report and literature review

INTRODUCTION

Glaucoma is the leading cause of irreversible blindness worldwide. Schlemm's canal surgery using an iTrack flexible microcatheter has become popular because of its high quality-of-life issues and the growing demand for less invasive but effective procedures. The unique design of the microcatheter makes it a multimodal tool, which can be used not only in the field of antiglaucoma surgery but also as a drug delivery system to treat various conditions.

AREAS COVERED

This review presents an update on the selected aspects of a drug delivery system using the iTrack microcatheter, including glaucoma gene therapy and posterior-segment diseases, both in animal models and human patients. The authors also report the case of a patient with branch retinal vein occlusion treated with suprachoroidal bevacizumab in the submacular region administered with the iTrack catheter.

EXPERT OPINION

The findings presented in this study may indicate that the application of a microcatheter in open-angle glaucoma gene therapy is reasonable and can be combined with full or partial surgical canaloplasty procedures. Translation of this potential into a treatment modality would require overcoming multiple barriers.

A Novel Device for Suprachoroidal Drug Delivery to Retina: Evaluation in Nonhuman Primates

Purpose

Evaluation of distribution and tolerance of suprachoroidal injection of indocyanine green (ICG) in nonhuman primates (NHPs) using a novel suprachoroidal (SC) delivery technology.

Methods

Three live and three euthanized African green monkeys were injected with 150 or 200 µL ICG/eye into the SC space of both eyes, 2.5 mm posterior to the limbus in the inferior quadrant, utilizing a novel SC injector. Eyes were analyzed by imaging of scleral flatmounts. Live animals were observed for 24 hours for general health. Ophthalmic evaluation included slit-lamp biomicroscopy, tonometry, fundus imaging, confocal laser ophthalmoscopy, and spectral-domain optical coherence tomography (SD-OCT) before and at 10 minutes and 1, 3, and 24 hours post-injection.

Results

SC dosing was successfully performed in all eyes. Infrared fundus imaging demonstrated ICG distribution throughout the posterior segment, reaching the macula within 24 hours post-injection. No inflammation, intravitreal penetration, SC blebs, retinal detachment, or hemorrhages were detected. No significant changes were observed in retinal thickness by SD-OCT (P = 0.267, ANOVA). A mild, statistically insignificant elevation in intraocular pressure was observed within 10 minutes post-injection (mean ± standard error: 7.28 ± 5.09 mmHg; P = 0.061) and was spontaneously resolved within the first hour after dosing.

Conclusions

Suprachoroidal injection of 150 to 200 µL ICG dye was successfully performed and well tolerated in NHP eyes, with rapid distribution into the macular region and throughout the posterior pole.

Translational Relevance

This novel SC drug delivery system may potentially provide safe and effective delivery of therapeutics to the posterior pole region in humans.

Ocular immunosuppressive microenvironment and novel drug delivery for control of uveitis

Ocular immune privilege is a phenomenon described by Peter Medawar in relation to the indefinite survival of the placement of foreign tissue grafts into the eye. Several mechanisms have been described that contribute to ocular immune privilege, such as a blood-ocular barrier and lack of lymphatics in the eye, the production of immune-suppressing molecules inside the ocular microenvironment, and the induction of systemic regulatory immunity against antigens found in the eye. Because ocular immune privilege is not absolute, failure of it can result in uveitis. Uveitis is a group of inflammatory disorders that can lead to vision loss if not treated properly. The current uveitis treatments involve the use of immunosuppressive and anti-inflammatory medications. Researching mechanisms of ocular immune privilege and the development of novel treatments for uveitis is ongoing. This review discusses mechanisms of ocular immune privilege, followed by an overview of uveitis treatments and ongoing clinical trials.

Triamcinolone Acetonide Suprachoroidal Injectable Suspension for Uveitic Macular Edema: Integrated Analysis of Two Phase 3 Studies

INTRODUCTION

Macular edema, a common complication of uveitis, may result in vision loss. The aim of this analysis was to report integrated phase 3 trial data for triamcinolone acetonide injectable suspension for suprachoroidal use (SCS-TA) in the treatment of macular edema secondary to noninfectious uveitis using strict inclusion criteria.

METHODS

This analysis included patients with central subfield thickness (CST) ≥ 300 µm and best-corrected visual acuity (BCVA) of ≥ 5 and ≤ 70 Early Treatment Diabetic Retinopathy Study (ETDRS) letters at both screening and baseline who received ≥ 1 study treatment in either PEACHTREE (randomized, double-masked SCS-TA or sham control) or AZALEA (open-label SCS-TA). Patients received SCS-TA 4.0 mg (0.1 ml of 40 mg/ml) or control at baseline and week 12.

RESULTS

In the SCS-TA group (n = 95), 47.4% of patients gained ≥ 15 ETDRS letters from baseline to week 24 versus 16.7% of patients in the control group (n = 60; P < 0.001). Mean change in BCVA in the SCS-TA group was 9.6 letters at week 4 and 13.9 letters at week 24. CST also improved rapidly in the SCS-TA group (mean change: - 158.4 µm at week 4), with sustained reduction throughout the study (mean change: - 163.9 µm at week 24 versus - 19.3 µm in the control group; P < 0.001). No treatment-related serious adverse events (AEs) were reported. Incidence of AEs pertaining to elevated intraocular pressure was 12.6% and 15.0% in the SCS-TA and control groups, respectively; incidence of cataract formation/worsening AEs was 7.4% and 6.7%, respectively.

CONCLUSION

In this integrated analysis utilizing strict inclusion criteria, SCS-TA was found effective in the treatment of patients with macular edema associated with noninfectious uveitis and was generally well tolerated.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT02595398, NCT03097315.

Suprachoroidal injection of triamcinolone acetonide plus intravitreal bevacizumab in diabetic macular edema: a randomized pilot trial

BACKGROUND

To investigate the efficacy of injecting suprachoroidal triamcinolone acetonide (SCTA) plus intravitreal bevacizumab (IVB) into patients with center-involving diabetic macular edema (CI-DME).

METHODS

In this phase 2/3 randomized controlled pilot trial, sixty-six eyes with CI-DME and best-corrected visual acuity (BCVA) of at most 20/50 Snellen chart were randomly assigned into two groups. Monotherapy arm received sham injection plus 3 monthly IVB doses and combination arm received a single dose of SCTA and 3 monthly IVB doses. The mean improvements in BCVA and Central subfield thickness (CST), over the three-month was considered the main efficacy outcomes.

RESULTS

The mean BCVA improvements were obtained respectively as - 0.20 ± 0.20 log [minimum angle of resolution (MAR)] (P = 0.004) and 0.37 ± 0.24 log MAR (P < 0.001) in monotherapy and combination arms [between-group analysis (P = 0.014)]. Significant improvements were also observed in CST (P = 0.019) in the combination arm compared to the other. No adverse events (elevated intraocular pressure, cataract) were observed in any of the study arms.

CONCLUSION

Significant improvements in BCVA and retinal anatomical outcomes demonstrated the additive effects of SCTA to those of anti-vascular endothelial growth factors with no short-term side effects and this combination appears to be a promising option in the management of patients with CI-DME.

TRIAL REGISTRATION

The trial was registered in Iranian Registry of Clinical Trials (IRCT20200314046761N1).

Single Low-dose Suprachoroidal Triamcinolone Acetonide Injection in Macular Edema Secondary to Noninfectious Posterior Uveitis

PURPOSE

The purpose was to study the anatomical and functional outcome following single low-dose suprachoroidal triamcinolone acetonide (LD-SCTA) (2 mg) injection in noninfectious posterior uveitis.

METHODS

Eleven patients with macular edema (ME) more than 280 μ secondary to noninfectious uveitis were included in the study. A single LD-SCTA (0.5 ml) injection was performed in the study eye with the help of a novel suprachoroidal microneedle (Pricon, Iscon Surgicals, Jodhpur, Rajasthan, India). The study parameters were noted at 4 and 12 weeks post LD-SCTA injection.

RESULTS

Ten of 11 patients had a significant decrease in central macular thickness (CMT). The mean CMT measurement at baseline was 513.6 ± 191.73 μm for the 10 patients who responded to the treatment, which reduced significantly to 265.1 ± 34.72 μm (P < 0.003) and 260.6 ± 34.72 μm (P < 0.002) at 4 and 12 weeks, respectively. The mean best-corrected visual acuity (BCVA) at baseline was 0.84 ± 0.41 logMAR unit which improved to 0.52 ± 0.33 (P < 0.001) and 0.25 ± 0.22 (P < 0.000) at weeks 4 and 12, respectively. The mean intraocular pressure at baseline recorded was 16.36 ± 2.97 mmHg, 19.45 ± 4.80 mmHg (P = 0.06) at 4 weeks, and 17.27 ± 2.53 mmHg (P = 0.35) at 12 weeks. One eye which did not respond to LD-SCTA was a case of recurrent Vogt-Koyanagi-Harada disease.

CONCLUSION

Single LD-SCTA injection is efficacious in reducing CMT in ME, improving BCVA, and controlling the inflammation in noninfectious posterior uveitis. LD-SCTA can be used as a first-line therapy in noninfectious uveitis over other routes of steroid administration with a favorable outcome and safety profile.

Triamcinolone acetonide injectable suspension for suprachoroidal use in the treatment of macular edema associated with uveitis

Introduction

Macular edema due to noninfectious uveitis is a sight-threatening complication that is routinely treated with corticosteroids. Triamcinolone acetonide injectable suspension for suprachoroidal use (Xipere™) is an alternative treatment option for patients with non-infectious uveitis associated macular edema.

Areas covered

This review describes the recently FDA approved triamcinolone acetonide injectable suspension that can be injected into the suprachoroidal space. This physiological space is between the sclera and choroid. This allows for therapeutic targeting of the retina and choroid. This review highlights published clinical trials for this novel drug preparation.

Expert opinion

Suprachoroidal administration of triamcinolone acetonide has shown improvement in vision and inflammation in studies with non-infectious uveitis associated macular edema. This unique delivery method suggests the potential to decrease side effects of anterior segment exposure such as glaucoma and cataract, but head-to-head trials are needed for further study of safety and efficacy. Additionally, there are promising prospective studies underway for utilization of the suprachoroidal space for other diseases including macular degeneration, diabetic macular edema, and ocular tumors.

Progress in the pharmacotherapy of uveitis: the art of personalized care

INTRODUCTION

Uveitis is a heterogeneous group of inflammatory intraocular disorders which can lead to blindness, but prompt diagnosis and management can improve visual outcomes and reduce treatment burden.

AREAS COVERED

In this review, the authors provide an overview of commonly used treatments of the management of non-infectious uveitis.

EXPERT OPINION

Initially, the treatment of non-infectious uveitis was limited to corticosteroids which have a broad range of adverse ocular and systemic effects. Now new options, such as biological response modulators, are a novel yet exciting addition to this armory and have the potential to change the course of treatment as well as prognostic outcomes for uveitis patients. Additionally, further research is needed to evaluate the efficacy of this novel class of immunomodulators in uveitis therapy.

Suprachoroidal injection of triamcinolone acetonide using a custom-made needle to treat diabetic macular edema post pars plana vitrectomy: a case series

Objective

Diabetic macular edema (DME), the most common cause of diabetes-related visual impairment, may occur following pars plana vitrectomy (PPV) to manage proliferative diabetic retinopathy complications. This retrospective single-centre case series evaluated the efficacy and safety of injecting 4 mg/0.1 ml triamcinolone into the suprachoroidal space using a custom-made needle to treat DME post PPV.

Methods

Data regarding central macular thickness (CMT) using spectral domain-optical coherence tomography and best-corrected visual acuity (by Snellen chart) at baseline (pre-injection), and at 1, 4, and 8 weeks following injection were analysed, along with intraocular pressure (IOP), cataract progression, and ocular safety.

Results

Eleven eyes in 10 patients received 11 suprachoroidal injections. Vision improvement was noted (0.75 log minimum angle of resolution (MAR) at baseline to 0.40 log MAR after treatment). CMT reduced significantly from 456.45 ± 113.42 μm at baseline to 247.63 ± 53.40 μm at 8 weeks following injection. No rise in IOP, or cataract development in the single treated phakic eye, was observed during 8 weeks of follow-up.

Conclusion

Suprachoroidal injection of triamcinolone using a custom-made needle to treat DME post PPV shows promising results with acceptable safety outcomes. Large clinical trials with longer follow-up are needed to evaluate this treatment option for countries with limited health-care resources.

Safety and efficacy of suprachoroidal triamcinolone acetonide for the management of serous choroidal detachment prior to rhegmatogenous retinal detachment surgery: A Pilot study

Purpose

To study the safety and efficacy of pre-operative suprachoroidal triamcinolone acetonide (SCTA) for achieving reduction/resolution of serous choroidal detachment (CD) associated with rhegmatogenous retinal detachment (RRD).

Methods

This was a prospective, noncomparative, interventional pilot study. All consecutive patients presenting with RD and coexisting CD underwent transconjunctival injection of SCTA before proceeding with vitrectomy/scleral buckle surgery. Sequential ultrasound B scans were performed for assessing the change in height of the CD.

Results

The mean age of the cohort was 53.8 ± 10.8 years (range: 39-72 years). The CD was present in a median of 3 quadrants; the cumulative mean CD height was 5.59 mm (range: 2.02-9.42 mm). Following SCTA, a successful response (>50% reduction) was seen in five eyes by day 3 and in two eyes by day 5. Three eyes failed to respond to SCTA and required surgical drainage before proceeding with vitrectomy. No intraprocedural injection-related complications were noted. A transient rise in the intraocular pressure (30 mmHg) was seen in one eye following vitrectomy and was managed successfully with topical antiglaucoma medications.

Conclusion

Suprachoroidal administration of triamcinolone appears to be a safe and effective technique to achieve CD resolution in eyes with RRD.

Suprachoroidal versus Intravitreal Triamcinolone Acetonide for the Treatment of Diabetic Macular Edema

Purpose

This article aims to compare between intravitreal (IV) and suprachoroidal (SC) triamcinolone acetonide (TA) injection for the treatment of diabetic macular edema (DME) in terms of improvement in both best-corrected visual acuity (BCVA) and central macular thickness (CMT), and development of complications (intraocular pressure (IOP) rise and cataract progression), and to identify the efficient dose of TA using the SC route.

Patients and Methods

This prospective interventional randomized comparative study included 45 eyes of 32 patients, randomly divided into three groups, group I received 4 mg/0.1 mL intravitreal TA (IVTA), group II received 4 mg/0.1 mL suprachoroidal TA (SCTA), and group III received 2mg/0.1 mL SCTA. Patients were followed up for 6 months.

Results

At 1 month, a maximum reduction in CMT (147.33 ± 110.97 µm, 160.80 ± 98.25 µm and 65.64 ± 46.19 µm in groups I, II, and III, respectively) was observed, which was associated with the greatest improvement of BCVA (0.09 ± 0.09, 0.19 ± 0.10 and 0.10 ± 0.09 logMAR lines) in groups I, II, and III, respectively. At 3 months, CMT started to increase, and reduction was not statistically significant compared to baseline, except in group II (4 mg SCTA group) (149.80 ± 106.57 µm with P-value = 0.013). At 6 months, CMT and BCVA returned close to baseline except for group II which had a sustained reduction of 60.16 µm from baseline. Regarding steroid-related complications, IOP elevation of 10 mmHg or more was noted in 1 eye (6.7%), 2 eyes (13.3%), and 1 eye in groups I, II, and III, respectively. Three phakic eyes per group showed cataract progression.

Conclusion

SCTA is a safe and effective route for the treatment of DME, which has comparable effects to IVTA, and may even last longer.

Microneedle scleral patch for minimally invasive delivery of triamcinolone to the posterior segment of eye

The delivery of therapeutics to the posterior segment of the eye is achieved by invasive procedures, including intravitreal injections and implants. The topically applied formulations would not permeate through different tissue barriers of the eye to reach the posterior segment. Here, we demonstrate the effectiveness of microneedle scleral patch in delivering the model molecule, triamcinolone acetonide, to the posterior segment of the eye. Microneedle scleral patch (MSP) and microneedle corneal patch (MCP) were fabricated through the micromolding technique using rapidly dissolvable polyvinylpyrrolidone. The patches containing 25 microneedles were characterized for physical and mechanical properties, drug loading and release behavior in vitro and ex vivo porcine eye globe model. The distribution of TA administered using MSP and MCP in different ocular tissues was evaluated in the rabbit eye model. The results showed that microneedles with 545 ± 8 µm length and 279 ± 26 µm width at the base in MSP penetrate the scleral membrane with the application of 0.35 ± 0.06 N force. The needles dissolved within 60 s after insertion in the corneal and scleral tissue. The 5 min application of MSP showed a significantly (p < 0.05) greater TA disposition in the vitreous humor and choroid-retinal complex in excised porcine eye globe compared with MCP and TA nanosuspension eye drops. In rabbit model studies, the TA concentration was greatest in the choroid-retinal complex and sclera after administration through intravitreal injection and MSP, respectively. The TA disposition in the sclera was significantly (p < 0.05) greater after MSP application compared with intravitreal injection and MCP application for up to 24 h. MSP application provided a greater safety score compared with intravitreal injection. In conclusion, MSP can be developed as a minimally invasive drug delivery system to target the posterior segment of the eye.

Safety and Efficacy of Suprachoroidal Injection of Triamcinolone in Treating Macular Edema Secondary to Noninfectious Uveitis

Introduction 

One of the leading causes of blindness throughout the world is uveitis, which predominantly results in the feared complication of macular edema. We report the safety and efficacy of suprachoroidal injection of triamcinolone acetonide in the treatment of macular edema secondary to noninfectious uveitis. 

Methodology 

This prospective, nonrandomized interventional study was conducted at Layton Rahmatullah Benevolent Trust (LRBT) Eye Hospital, Lahore, from August 2019 till July 2020. All individuals older than 18 years, nonpregnant females with a central macular thickness of >320 µm were included. Those patients with uncontrolled diabetes, immunodeficiency, or any other disease mandating systemic corticosteroid use were excluded. All patients had a detailed ocular exam one week before the treatment, and 0.1 ml of triamcinolone acetonide 40 mg/ml was injected using a 30-G hollow needle into the suprachoroidal space. After the injection, an eye patch was applied and the patient was observed for three hours. All data were documented in a preformed proforma. 

Results

A total of 30 patients were included in the study with a mean age of 38.1 ± 9.48 years. Statistically significant differences were found between central macular thickness at presentation and at one and three months of the procedure, i.e., 569.60 ± 170.396, 266.77 ± 73.127, and 208.27 ± 37.292 µm, respectively. A similar difference was observed when comparing visual acuity at baseline to visual acuity at one and three months of the procedure (p < 0.001). 

Conclusion 

The current study indicates that a single dose of suprachoroidal injection of triamcinolone acetonide for the treatment of macular edema secondary to uveitis is safe and efficacious. No rise in intraocular pressure (IOP) was observed during the study period. Significant improvements in central macular thickness and visual acuity as well as tolerability and safety of the treatment were seen in our study. Further larger-scale studies are needed to ascertain the long-term benefits of the suprachoroidal triamcinolone acetonide.

Metal‐HisTag Coordination for Remote Loading of Very Small Quantities of Biomacromolecules into PLGA Microspheres

Challenges to discovery and preclinical development of long‐acting release systems for protein therapeutics include protein instability, use of organic solvents during encapsulation, specialized equipment and personnel, and high costs of proteins. We sought to overcome these issues by combining remote‐loading self‐healing encapsulation with binding HisTag protein to transition metal ions. Porous, drug‐free self‐healing microspheres of copolymers of lactic and glycolic acids with high molecular weight dextran sulfate and immobilized divalent transition metal (M²⁺) ions were placed in the presence of proteins with or without HisTags to bind the protein in the pores of the polymer before healing the surface pores with modest temperature. Using human serum albumin, insulin‐like growth factor 1, and granulocyte‐macrophage colony‐stimulating factor (GM‐CSF), encapsulated efficiencies of immunoreactive protein relative to nonencapsulation protein solutions increased from ~41%, ~23%, and ~9%, respectively, without Zn²⁺ and HisTags to ~100%, ~83%, and ~75% with Zn²⁺ and HisTags. These three proteins were continuously released in immunoreactive form over seven to ten weeks to 73%–100% complete release, and GM‐CSF showed bioactivity >95% relative to immunoreactive protein throughout the release interval. Increased encapsulation efficiencies were also found with other divalent transition metals ions (Co²⁺, Cu²⁺, Ni²⁺, and Zn²⁺), but not with Ca²⁺. Ethylenediaminetetraacetic acid was found to interfere with this process, reverting encapsulation efficiency back to Zn²⁺‐free levels. These results indicate that M²⁺‐immobilized self‐healing microspheres can be prepared for simple and efficient encapsulation by simple mixing in aqueous solutions. These formulations provide slow and continuous release of immunoreactive proteins of diverse types by using a amount of protein (e.g., <10 μg), which may be highly useful in the discovery and early preclinical development phase of new protein active pharmaceutical ingredients, allowing for improved translation to further development of potent proteins for local delivery.

Suprachoroidal CLS-TA versus Rescue Therapies for the Treatment of Uveitic Macular Edema: A Post Hoc Analysis of PEACHTREE

Background

This post hoc analysis compared the efficacy and safety of suprachoroidally administered triamcinolone acetonide (CLS‐TA) to other commonly available treatments for non‐infectious uveitis.

Methods

Results from the PEACHTREE study were compared between subjects randomised to CLS‐TA not requiring rescue therapy and those subjects randomised to control, who subsequently required rescue therapy. Endpoints included best corrected visual acuity (BCVA), central subfield thickness (CST), treatment emergent adverse events and intraocular pressure (IOP) related safety findings.

Results

In this analysis, there were 83 unrescued CLS‐TA subjects and 46 rescued control subjects. At Week 24, 51.9% of the unrescued CLS‐TA subjects gained ≥15 letters in BCVA, compared to 37.0% of the rescued control subjects (p = 0.115). Unrescued CLS‐TA subjects showed a mean gain of 15.7 versus 10.9 letters in rescued control subjects (p = 0.080). A significantly greater mean reduction in CST was observed for unrescued CLS‐TA subjects versus rescued control subjects (174.0 and 148.5 μm; p = 0.040). Of unrescued CLS‐TA subjects, 4.9% experienced IOP elevations ≥30 mm Hg at any visit versus 10.9% of rescued control subjects. Further, use of IOP‐lowering medications appeared lower in unrescued CLS‐TA subjects versus rescued control subjects (7.2% vs. 13.0%). There were no IOP‐lowering surgical interventions in either group.

Conclusion

CLS‐TA subjects experienced significantly greater reduction in CST and tended towards greater improvement in BCVA, compared with rescued control subjects. Suprachoroidally administered CLS‐TA showed a lower incidence of IOP‐related safety findings.

A Review of Ocular Drug Delivery Platforms and Drugs for Infectious and Noninfectious Uveitis: The Past, Present, and Future

Uveitis refers to a broad group of inflammatory disorders of the eye that often require medical and surgical management to improve or stabilize vision and prevent vision-threatening pathological changes to the eye. Drug delivery to the eye to combat inflammation and subsequent complications from uveitic conditions is complex as there are multiple barriers to absorption limiting availability of the needed drug in the affected tissues. As such, there has been substantial interest in developing new drugs and drug delivery platforms to help reduce intraocular inflammation and its complications. In this review, we discuss the challenges of drug delivery, novel technologies recently approved for uveitis patient care and promising drug delivery platforms for uveitis and sequelae of ocular inflammation.

Drug Delivery via the Suprachoroidal Space for the Treatment of Retinal Diseases

The suprachoroidal space (SCS), a potential space between the sclera and choroid, is becoming an applicable method to deliver therapeutics to the back of the eye. In recent years, a vast amount of research in the field has been carried out, with new discoveries in different areas of interest, such as imaging, drug delivery methods, pharmacokinetics, pharmacotherapies in preclinical and clinical trials and advanced therapies. The SCS can be visualized via advanced techniques of optical coherence tomography (OCT) in eyes with different pathologies, and even in healthy eyes. Drugs can be delivered easily and safely via hollow microneedles fitted to the length of the approximate thickness of the sclera. SCS injections were found to reach greater baseline concentrations in the target layers compared to intravitreal (IVT) injection, while agent clearance was faster with highly aqueous soluble molecules. Clinical trials with SCS injection of triamcinolone acetonide (TA) were executed with promising findings for patients with noninfectious uveitis (NIU), NIU implicated with macular edema and diabetic macular edema (DME). Gene therapy is evolving rapidly with viral and non-viral vectors that were found to be safe and efficient in preclinical trials. Here, we review these novel different aspects and new developments in clinical treatment of the posterior segment of the eye.

Modified inexpensive needle for suprachoroidal triamcinolone acetonide injections in pseudophakic cystoid macular edema

Pseudophakic cystoid macular edema (PCME) is one of the leading causes of reduced vision, after cataract surgery. Topical steroids and nonsteroidal anti-inflammatory drops are frequently used in the management; however, intravitreal injections may be required for chronic cases. Suprachoroidal injection of preservative free Triamcinolone acetonide is a recent addition to the therapeutic armamentarium of ophthalmologists for treatment of cystoid macular edema of varied etiology. Though the drug is commercially available at a reasonable cost, the microneedle is not commonly available. We modified a 26 G needle for safe and cost-effective delivery of preservative-free suprachoroidal triamcinolone acetonide (SCT). In the current series of three patients with non-resolving PCME, macular edema resolved and vision improved over 3 months.

Efficacy and safety of suprachoroidal triamcinolone injection in horses with poorly responsive equine recurrent uveitis

OBJECTIVE

Equine recurrent uveitis (ERU), a chronic, immune-mediated intraocular inflammatory disease, is a common cause of blindness in horses. The severity and recurrent nature of ERU makes it difficult to treat with current therapeutics leading to a poor visual prognosis. The suprachoroidal space (SCS), a potential space between the choroid and sclera surrounding the ocular posterior segment, offers a promising alternative site for drug application to the eye. Corticosteroid administration within this space is hypothesized to be safe and effective at controlling intraocular inflammation, especially in horses with poorly responsive ERU.

ANIMAL STUDIED

Horses with active, poorly responsive ERU.

PROCEDURE(S)

A retrospective study was performed with 29 horses (36 total eyes) that received SCS injection of triamcinolone acetonide (TA) with ERU not well controlled with standard uveitis treatment. A standardized ocular inflammation score (OIS) was used to assess inflammation at the time of injection and at follow-ups.

RESULTS

Standardized OIS revealed a significant decrease in ocular inflammation over time after SCS TA administration (p < .004). Adverse effects after injections occurred in <20% of the horses at follow-up, but some of these effects were attributed to chronic inflammation prior to effective treatment, long-term topical corticosteroid use, or complications from hospitalization rather than the SCS injections. Most horses (86.7%) in this study remained visual greater than 3 months after SCS injection.

CONCLUSIONS

Based on these results, SCS TA injections appear to be a safe and possible effective treatment modality for managing poorly responsive ERU; further clinical study is warranted.

Extension study of the safety and efficacy of CLS-TA for treatment of macular oedema associated with non-infectious uveitis (MAGNOLIA)

PURPOSE

To assess the extended efficacy and safety of suprachoroidal triamcinolone acetonide injectable suspension (CLS-TA) among patients with macular oedema (ME) secondary to non-infectious uveitis (NIU).

METHODS

Patients with uveitic ME were treated with suprachoroidal CLS-TA at baseline and week 12 of the Efficacy and Safety of Suprachoroidal CLS-TA for Macular Edema Secondary to Noninfectious Uveitis: Phase 3 Randomized Trial (PEACHTREE) study. Time to rescue was evaluated over 24 additional weeks for MAGNOLIA. Safety data, visual acuity and retinal central subfield thickness (CST) reduction were also evaluated. Of the 53 eligible patients (46 CLS-TA and 7 control), 33 patients were enrolled (28 CLS-TA and 5 control).

RESULTS

Over the entire 48-week period for PEACHTREE and MAGNOLIA, the median time to rescue therapy was 257 days versus 55.5 days for the CLS-TA and sham-control arms, respectively. Of 28 CLS-TA treated patients who participated in MAGNOLIA, 14 (50%) did not require rescue therapy through approximately 9 months after the second treatment. Among CLS-TA patients not requiring rescue, there was a mean gain of 12.1 letters and mean CST reduction of 174.5 µm at week 48. No serious adverse events related to study treatment were observed.

CONCLUSION

Approximately 50% of patients did not require additional treatment for up to 9 months following the last CLS-TA administration.

Suprachoroidal Delivery of Small Molecules, Nanoparticles, Gene and Cell Therapies for Ocular Diseases

Suprachoroidal drug delivery technology has advanced rapidly and emerged as a promising administration route for a variety of therapeutic candidates, in order to target multiple ocular diseases, ranging from neovascular age-related macular degeneration to choroidal melanoma. This review summarizes the latest preclinical and clinical progress in suprachoroidal delivery of therapeutic agents, including small molecule suspensions, polymeric entrapped small molecules, gene therapy (viral and nonviral nanoparticles), viral nanoparticle conjugates (VNCs), and cell therapy. Formulation customization is critical in achieving favorable pharmacokinetics, and sustained drug release profiles have been repeatedly observed for multiple small molecule suspensions and polymeric formulations. Novel therapeutic agents such as viral and nonviral gene therapy, as well as VNCs, have demonstrated promise in animal studies. Several of these suprachoroidally-administered therapies have been assessed in clinical trials, including small molecule suspensions of triamcinolone acetonide and axitinib, viral vector RGX-314 for gene therapy, and VNC AU-011. With continued drug delivery research and optimization, coupled with customized drug formulations, suprachoroidal drug delivery may address large unmet therapeutic needs in ophthalmology, targeting affected tissues with novel therapies for efficacy benefits, compartmentalizing therapies away from unaffected tissues for safety benefits, and achieving durability to relieve the treatment burden noted with current agents.

Ocular Drug Delivery to the Retina: Current Innovations and Future Perspectives

Treatment options for retinal diseases, such as neovascular age-related macular degeneration, diabetic retinopathy, and retinal vascular disorders, have markedly expanded following the development of anti-vascular endothelial growth factor intravitreal injection methods. However, because intravitreal treatment requires monthly or bimonthly repeat injections to achieve optimal efficacy, recent investigations have focused on extended drug delivery systems to lengthen the treatment intervals in the long term. Dose escalation and increasing molecular weight of drugs, intravitreal implants and nanoparticles, hydrogels, combined systems, and port delivery systems are presently under preclinical and clinical investigations. In addition, less invasive techniques rather than intravitreal administration routes, such as topical, subconjunctival, suprachoroidal, subretinal, and trans-scleral, have been evaluated to reduce the treatment burden. Despite the latest advancements in the field of ophthalmic pharmacology, enhancing drug efficacy with high ocular bioavailability while avoiding systemic and local adverse effects is quite challenging. Consequently, despite the performance of numerous in vitro studies, only a few techniques have translated to clinical trials. This review discusses the recent developments in ocular drug delivery to the retina, the pharmacokinetics of intravitreal drugs, efforts to extend drug efficacy in the intraocular space, minimally invasive techniques for drug delivery to the retina, and future perspectives in this field.

Creating an Ocular Biofactory: Surgical Approaches in Gene Therapy for Acquired Retinal Diseases

ABSTRACT

Gene therapy offers the potential to treat inherited retinal disorders and deliver sustained therapy for acquired retinal diseases. In the latter case, host cells can be harnessed to produce non-native proteins that have beneficial properties, such as antivascular endothelial growth factor activity, transforming the eye into an ocular "biofactory." Several gene therapy programs have entered clinical testing for delivery to the vitreous, subretinal, and suprachoroidal space. Improved viral vectors and refined surgical techniques are critical to successful delivery of therapeutic products to the target tissue. In this review, we discuss the development of gene therapy products aimed at acquired retinal diseases and the surgical techniques utilized to achieve targeted delivery.

Biomechanics of suprachoroidal drug delivery: From benchtop to clinical investigation in ocular therapies

INTRODUCTION

As research in suprachoroidal drug delivery advances, and therapeutic candidates, ranging from small molecule suspensions to gene therapy, progress through clinical trials, an understanding of  suprachoroidal space (SCS) biomechanics assumes increasing importance.Areas covered:Numerous anatomic features play an important role in therapeutic access to the SCS. Methods of access include a catheter, a standard hypodermic needle, and a microinjector with microneedle. Physical and fluidic properties of injectates into the SCS, such as volume, viscosity, particle size, osmotic pressure, and ionic charge of formulation can impact the spread and extent of opening of the SCS. Pharmacokinetic data of several small molecule suspensions yielded favorable ocular distribution and pharmacokinetic profiles. Phase 2 and 3 clinical trials have been completed with a suprachoroidally injected corticosteroid; results and information on procedural details with the microinjector are discussed.

EXPERT OPINION

Suprachoroidal drug delivery has been demonstrated to be a reliable and consistent drug delivery method for targeted treatment of retinal and choroidal disorders to potentially maximize efficacy, while compartmentalizing therapies away from the unaffected tissues to potentially enhance safety. These delivery attributes, along with fluid transport properties and formula customization for pharmacological agents, may allow for more tailored treatment of diseases affecting chorio-retinal tissues.

Drug-Free, Nonsurgical Reduction of Intraocular Pressure for Four Months after Suprachoroidal Injection of Hyaluronic Acid Hydrogel

Glaucoma is the leading cause of irreversible blindness. Current treatments use drugs or surgery to reduce intraocular pressure (IOP). In this study, a drug-free, nonsurgical method is developed that lowers IOP for 4 months without requiring daily patient adherence. The approach involves expanding the suprachoroidal space (SCS) of the eye with an in situ-forming hydrogel injected using a microneedle. This study tests the hypothesis that SCS expansion increases the drainage of aqueous humor from the eye via the unconventional pathway, which thereby lowers IOP. SCS injection of a commercial hyaluronic acid (HA) hydrogel reduces the IOP of normotensive rabbits for more than 1 month and an optimized HA hydrogel formulation enables IOP reduction for 4 months. Safety assessment by clinical ophthalmic examinations indicate the treatment is well tolerated. Histopathology shows minor hemorrhage and fibrosis at the site of injection. Further analysis by ultrasound biomicroscopy demonstrates a strong correlation of IOP reduction with SCS expansion. Outflow facility measurements show no difference in pressure-dependent outflow by the conventional pathway between treated and untreated eyes, supporting the hypothesis. In conclusion, SCS expansion with an in situ-forming hydrogel can enable extended IOP reduction for treating ocular hypertension and glaucoma without drugs or surgery.

Dexamethasone delivery to the ocular posterior segment by sustained-release Laponite formulation

This paper presents a novel nanoformulation for sustained-release delivery of dexamethasone (DEX) to the ocular posterior segment using a Laponite (LAP) carrier-DEX/LAP 1:10 w w^-1 formulation; 10 mg ml^-1. In vivo ocular feasibility and pharmacokinetics after intravitreal (IV) and suprachoroidal (SC) administration in rabbit eyes are compared against IV administration of a DEX solution (1 mg ml^-1). Thirty rabbit eyes were injected with the DEX/LAP formulation (15 suprachoroid/15 intravitreous). Ophthalmological signs were monitored at day 1 and at weeks 1-4-12-24 post-administration. Three eyes per sample time point were used to quantify DEX concentration using high-performance liquid chromatography-mass spectrometry. The ocular tissues' pharmacokinetic parameters (lens, vitreous humour, choroid-retina unit and sclera) were studied. DEX/LAP was well tolerated under both administration methods. Peak intraocular DEX levels from the DEX/LAP were detected in the vitreous humour after both deliveries soon after administration. The vitreous area under the curve was significantly greater after both DEX/LAP deliveries (IV: 205 968.47; SC: 11 442.22 ng g^-1 d^-1) than after IV administration of the DEX solution (317.17 ng g^-1 d^-1). Intravitreal DEX/LAP delivery extended higher vitreous DEX levels up to week 24 (466.32 ± 311.15 ng g^-1). With SC delivery, DEX levels were detectable in the choroid-retina unit (12.04 ± 20.85 ng g^-1) and sclera (25.46 ± 44.09 ng g^-1) up to week 24. This study demonstrated the intraocular feasibility of both SC and IV administration of the DEX/LAP formulation. The LAP increased the intraocular retention time of DEX when compared with conventional solutions. DEX/LAP could be considered a biocompatible and useful sustained-release formulation for treating posterior-pole eye diseases.

Suprachoroidal CLS-TA plus Intravitreal Aflibercept for Diabetic Macular Edema: A Randomized, Double-Masked, Parallel-Design, Controlled Study

PURPOSE

This study evaluated the potential safety, efficacy, and durability advantages of investigational triamcinolone acetonide suspension (CLS-TA; Clearside Biomedical, Alpharetta, GA) administered suprachoroidally in conjunction with intravitreal aflibercept compared with aflibercept monotherapy for treatment of diabetic macular edema (DME).

DESIGN

TYBEE was a prospective, controlled, double-masked study. Patients were randomized 1:1 to CLS-TA and aflibercept (active) or aflibercept monotherapy (control), and assessed over 24 weeks.

PARTICIPANTS

Treatment-naive DME patients with best-corrected visual acuity (BCVA) of 20 to 70 letters and central subfield retinal thickness (CST) of more than 300 μm.

METHODS

Patients in the active group (n = 36) received CLS-TA and aflibercept at baseline and week 12. Patients in the control group (n = 35) received aflibercept at baseline, week 4, week 8, and week 12. To mask both groups, sham suprachoroidal and intravitreal injections were utilized. All patients were eligible to receive aflibercept as needed at weeks 4, 8, 16, and 20 per prespecified criteria.

MAIN OUTCOME MEASURE

Mean change in BCVA from baseline. Treatment differences were assessed with a 2-sided significance level of 0.10.

RESULTS

Mean BCVA changes from baseline to week 24 were not statistically different in the active and control groups (intention-to-treat [ITT] population: +11.4 letters and +13.8 letters [P = 0.288]; per protocol [PP] population: +12.3 letters and +13.5 letters [P = 0.664]; respectively). Greater improvement in CST was seen in the active versus control group (ITT population: -212.1 μm and -178.6 μm [P = 0.089]; PP population: -226.5 μm and -176.1 μm [P = 0.035]; respectively). Compared with the control group, eyes in the active group received fewer treatments (scheduled plus as-needed treatments averaging 4.6 versus 2.6, respectively). No treatment-related serious adverse events were observed. Ocular adverse events were low for both arms. Cataract events, all assessed as unrelated to treatment, and events of elevated intraocular pressure trended higher in the active group.

CONCLUSIONS

CLS-TA administered suprachoroidally in conjunction with intravitreal aflibercept for treatment of DME provides simliar visual benefit at 24 weeks' follow-up compared with aflibercept monotherapy, is well tolerated and shows modest anatomic benefit with potential to reduce treatment burden.

Suprachoroidal gene transfer with nonviral nanoparticles

Subretinal injections of viral vectors provide great benefits but have limited cargo capacity; they induce innate and adaptive immune responses, which may cause damage and preclude repeated injections; and they pose administration risks. As a new biotechnology, suprachoroidal injections of biodegradable nanoparticles (NPs) containing a reporter plasmid induce reporter expression in rat photoreceptors and RPE throughout the entire eye and maintain expression for at least 8 months. Multiple injections markedly increase expression. Suprachoroidal injection of NPs containing a VEGF expression plasmid caused severe subretinal neovascularization progressing to subretinal fibrosis, similar to what occurs in untreated patients with neovascular age-related macular degeneration, providing a new model and proof of concept for level and duration of expression. Suprachoroidal injection of NPs containing a VEGF-binding protein expression plasmid significantly suppressed VEGF-induced vascular leakage and neovascularization demonstrating therapeutic potential. These data suggest that nonviral NP suprachoroidal gene transfer may provide a noninvasive, repeatable alternative to subretinal injection of viral vectors.

Suprachoroidal Delivery of Viral and Nonviral Gene Therapy for Retinal Diseases

Retinal gene therapy is a rapidly growing field with numerous clinical trials underway, and route of delivery is a critical contributor to its success. Subretinal administration, which involves pars plana vitrectomy in the operating room, offers targeted delivery to retinal-pigment epithelium cells and photoreceptors. Due to the immune-privileged nature of the subretinal space, the risk of an immune reaction against viral capsid antigens is minimized, an advantage of subretinal administration in patients with preexisting neutralizing antibodies. Intravitreal administration, with fewer procedure-related complications, is challenged by potential immune response and incomplete vector penetration through the internal limiting membrane. However, novel vectors, optimized by "directed evolution" may address these issues. Nonsurgical in-office suprachoroidal gene delivery offers the potential for greater surface-area coverage of the posterior segment compared to focal subretinal injection, and is not hindered by the internal limiting membrane. However, the vector must pass through multiple layers to reach the targeted retinal layers, and there is a risk of immune response. This review highlights recent developments, challenges, and future opportunities associated with viral and nonviral suprachoroidal gene delivery for the treatment of chorioretinal diseases. While ocular tolerability and short-term effectiveness of suprachoroidal gene delivery have been demonstrated in preclinical models, durability of gene expression, long-term safety, potential systemic exposure, and effective delivery to the macula require further exploration. Although the safety and efficacy of suprachoroidal gene delivery are yet to be proven in clinical trials, further optimization could facilitate nonsurgical in-office suprachoroidal gene therapy.

Efficacy and Safety of Suprachoroidal CLS-TA for Macular Edema Secondary to Noninfectious Uveitis: Phase 3 Randomized Trial

PURPOSE

Injection of pharmacotherapy into the suprachoroidal space, between the sclera and choroid, is an alternative delivery technique developed with the rationale of providing higher drug concentrations to posterior ocular structures compared with other intraocular and periocular injection procedures. This study was conducted to evaluate the safety and efficacy of suprachoroidally injected triamcinolone acetonide formulation (CLS-TA), a suspension of triamcinolone acetonide, in improving vision among patients with noninfectious uveitis complicated by macular edema (ME).

DESIGN

Phase 3 masked, randomized trial.

PARTICIPANTS

One hundred sixty patients with ME secondary to noninfectious uveitis. Patients were required to have a best-corrected visual acuity (BCVA) of 5 or more Early Treatment Diabetic Retinopathy Study (ETDRS) letters (Snellen equivalent, 20/800) and 70 or fewer ETDRS letters read (Snellen equivalent, 20/40) in the study eye.

METHODS

Patients were randomized 3:2 to suprachoroidally injected CLS-TA or sham treatment, with administrations at day 0 and week 12.

MAIN OUTCOME MEASURES

The primary end point was improvement from baseline of 15 or more ETDRS letters in BCVA at week 24. The secondary end point was reduction from baseline in central subfield thickness (CST) at week 24.

RESULTS

In the CLS-TA arm, 47% of patients gained 15 or more ETDRS letters in BCVA versus 16% in the control arm (P < 0.001), meeting the primary end point. Mean reductions in CST from baseline were 153 μm versus 18 μm (P < 0.001). No serious adverse events (AEs) related to treatment were reported. Corticosteroid-associated AEs of elevated intraocular pressure occurred in 11.5% and 15.6% of the CLS-TA and control groups, respectively. Cataract AE rates were comparable (7.3% and 6.3%, respectively).

CONCLUSIONS

Patients in the CLS-TA study arm experienced clinically significant improvement in vision relative to the sham procedure, demonstrating the efficacy of suprachoroidal injection of CLS-TA for the treatment of ME in a vision-threatening disorder.

Collagenase injection into the suprachoroidal space of the eye to expand drug delivery coverage and increase posterior drug targeting

Injection into the suprachoroidal space (SCS) allows drug delivery targeted to sclera, choroid, and retina. Here, we studied SCS injection formulated with collagenase to expand drug delivery coverage and increase posterior drug targeting within SCS by breaking down collagen fibrils that link sclera and choroid in the SCS. When 1 μm latex microparticles were injected with a collagenase formulation using microneedles into the SCS of rabbit eyes ex vivo and incubated at 37 °C for 4 h, microparticle delivery coverage increased from 20% to 45% and enhanced posterior drug targeting. Collagenase concentration was optimized to 0.5 mg/mL to maximize expanded posterior delivery and minimize tissue damage. Effects of collagenase injection within SCS increased and then plateaued 4 h after injection. Simultaneous injection of collagenase and microparticles had a greater effect on expanded delivery in the SCS compared to sequential injection. Collagenase injection into the SCS of rabbit eyes in vivo was also effective to expand delivery and was generally well-tolerated, showing transiently lowered IOP, but no apparent lasting adverse effects on ocular tissues such as sclera, choroid, and retina, as determined by analyzing histology, sclera tensile strength, and fundus imaging. We conclude that addition of collagenase during SCS injection can expand drug delivery coverage and increase posterior drug targeting.

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.

A resistance-sensing mechanical injector for the precise delivery of liquids to target tissue

The precision of the delivery of therapeutics to the desired injection site by using syringes and hollow needles typically depends on the operator. Here, we introduce a highly sensitive, completely mechanical and cost-effective injector for targeting tissue reliably and precisely. As the operator pushes on the syringe plunger, the injector senses the loss-of-resistance on encountering a softer tissue or a cavity, stops advancing the needle, and delivers the payload. We demonstrate that the injector can reliably deliver liquids to the suprachoroidal space — a challenging injection site that provides access to the back of the eye — for a wide range of eye sizes, scleral thicknesses and intraocular pressures, and to target sites relevant for epidural injections, subcutaneous injections and intraperitoneal access. The design of this simple and effective injector can be adapted for a broad variety of clinical applications.

Targeting drug delivery within the suprachoroidal space

The suprachoroidal space (SCS), a potential anatomical space between the sclera and choroid, is a novel route for drug delivery targeting the chorioretinal layers of the eye. The safety and efficacy of SCS drug delivery have been shown in multiple clinical trials. Recent studies have developed methods for more precise targeting within the SCS at sites of action at the posterior pole (e.g., macula), near the limbus (e.g., ciliary body), and throughout the SCS using iontophoresis, swollen hydrogels, high-density particle emulsions, highly viscous and non-Newtonian fluids, and microstents. Here, we review novel technologies targeting the posterior, anterior, or entire SCS.

Suprachoroidally injected pharmacological agents for the treatment of chorio-retinal diseases: a targeted approach

Delivery of pharmaceuticals to the posterior segment presents challenges that arise from the anatomy and clearance pharmacokinetics of the eye. Systemic and several local administration options [topical, periocular, intravitreal (IVT) and subretinal] are in clinical use, each with a unique benefit to risk profile shaped by factors including the administered agent, frequency of dosing, achievable pharmaceutical concentrations within posterior segment structures versus elsewhere in the eye or the body, invasiveness of the procedure and the inherent challenges with some administration methods. The use of the suprachoroidal space (SCS), which is the region between the sclera and the choroid, is being explored as a potential approach to target pharmacotherapies to the posterior segment via a minimally invasive injection procedure. Preclinical data on agents such as vascular endothelial growth factor inhibitors and triamcinolone acetonide (TA) indicate that administration via suprachoroidal injection results in more posterior distribution of the pharmacologic agent, with higher exposure to the sclera, choroid, retinal pigment epithelium cells and retina, and lesser exposure to the anterior segment, than observed with IVT administration. Based in part on these findings, clinical trials have explored the efficacy and safety of suprachoroidal administration of pharmacologic therapies in conditions affecting the posterior segment. Data on a proprietary formulation of TA administered by suprachoroidal injection show improvement in anatomic and visual outcomes in subjects with noninfectious uveitis, with the potential to mitigate the known risks of cataract and increased intraocular pressure (IOP) associated with the use of intraocular corticosteroids. Suprachoroidal administration appears to be a promising treatment modality and is also in the early stages of investigation for other possible applications, such as injection of antiglaucoma agents into the anterior SCS for long-lasting control of elevated IOP, and as a mode of delivery for gene- or cell-based therapies for retinal disorders.

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.

Suprachoroidal Space Alterations Following Delivery of Triamcinolone Acetonide: Post-Hoc Analysis of the Phase 1/2 HULK Study of Patients With Diabetic Macular Edema

BACKGROUND AND OBJECTIVE

To study anatomic changes in the suprachoroidal space (SCS) following suprachoroidal injection of CLS-TA, triamcinolone acetonide injectable suspension.

PATIENTS AND METHODS

Eyes with diabetic macular edema receiving CLS-TA were imaged serially using anterior segment spectral-domain optical coherence tomography to examine the SCS.

RESULTS

At the final imaging session, the SCS was not significantly different in study eyes (n = 14; 8.4 μm) compared to fellow eyes (n = 10; 8.1 μm; P = .698). Two eyes were imaged immediately before and 30 minutes after suprachoroidal injections; in these eyes, mean suprachoroidal width increased significantly following CLS-TA injection, 9.9 μm to 75.1 μm (P < .001), and subsequently returned to 14.9 μm 1 month after the final injection (P = .221).

CONCLUSION

Suprachoroidal CLS-TA injection caused a measurable increase in the SCS, which returned to preinjection levels by 1 month following injection with no apparent lasting impact on SCS anatomy. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:692-697.].

Ocular drug delivery targeted by iontophoresis in the suprachoroidal space using a microneedle

Treatment of many posterior-segment ocular indications would benefit from improved targeting of drug delivery to the back of the eye. Here, we propose the use of iontophoresis to direct delivery of negatively charged nanoparticles through the suprachoroidal space (SCS) toward the posterior pole of the eye. Injection of nanoparticles into the SCS of the rabbit eye ex vivo without iontophoresis led to a nanoparticle distribution mostly localized at the site of injection near the limbus and <15% of nanoparticles delivered to the most posterior region of SCS (>9 mm from the limbus). Iontophoresis using a novel microneedle-based device increased posterior targeting with >30% of nanoparticles in the most posterior region of SCS. Posterior targeting increased with increasing iontophoresis current and increasing application time up to 3 min, but further increasing to 5 min was not better, probably due to the observed collapse of the SCS within 5 min after injection ex vivo. Reversing the direction of iontophoretic flow inhibited posterior targeting, with just ~5% of nanoparticles reaching the most posterior region of SCS. In the rabbit eye in vivo, iontophoresis at 0.14 mA for 3 min after injection of a 100 μL suspension of nanoparticles resulted in ~30% of nanoparticles delivered to the most posterior region of the SCS, which was consistent with ex vivo findings. The procedure was well tolerated, with only mild, transient tissue effects at the site of injection. We conclude that iontophoresis in the SCS using a microneedle has promise as a method to target ocular drug delivery within the eye, especially toward the posterior pole.

The suprachoroidal space as a route of administration to the posterior segment of the eye

The suprachoroidal space (SCS) is a potential space between the sclera and choroid that traverses the circumference of the posterior segment of the eye. The SCS is an attractive site for drug delivery because it targets the choroid, retinal pigment epithelium, and retina with high bioavailability, while maintaining low levels elsewhere in the eye. Indeed, phase III clinical trials are investigating the safety and efficacy of SCS drug delivery. Here, we review the anatomy and physiology of the SCS; methods to access the SCS; kinetics of SCS drug delivery; strategies to target within the SCS; current and potential clinical indications; and the safety and efficacy of this approach in preclinical animal studies and clinical trials.