Intravitreal injection of therapeutic agents

A First-Passage Model of Intravitreal Drug Delivery and Residence Time-Influence of Ocular Geometry, Individual Variability, and Injection Location

Purpose

Standard of care for various retinal diseases involves recurrent intravitreal injections. This motivates mathematical modeling efforts to identify influential factors for ocular drug residence time, aiming to minimize administration frequency. We sought to describe the vitreal diffusion of therapeutics in nonclinical species frequently used during drug development assessments. In human eyes, we investigated the impact of variability in vitreous cavity size and eccentricity, and in injection location, on drug disposition.

Methods

Using a first-passage time approach, we modeled the transport-controlled distribution of two standard therapeutic protein formats (Fab and IgG) and elimination through anterior and posterior pathways. Anatomical three-dimensional geometries of mouse, rat, rabbit, cynomolgus monkey, and human eyes were constructed using ocular images and biometry datasets. A scaling relationship was derived for comparison with experimental ocular half-lives.

Results

Model simulations revealed a dependence of residence time on ocular size and injection location. Delivery to the posterior vitreous resulted in increased vitreal half-life and retinal permeation. Interindividual variability in human eyes had a significant influence on residence time (half-life range of 5-7 days), showing a strong correlation to axial length and vitreal volume. Anterior exit was the predominant route of drug elimination. Contribution of the posterior pathway displayed a 3% difference between protein formats but varied between species (10%-30%).

Conclusions

The modeling results suggest that experimental variability in ocular half-life is partially attributed to anatomical differences and injection site location. Simulations further suggest a potential role of the posterior pathway permeability in determining species differences in ocular pharmacokinetics.

Mathematical Models of Ocular Drug Delivery

Drug delivery is an important factor for the success of ocular drug treatment. However, several physical, biochemical, and flow-related barriers limit drug exposure of anterior and posterior ocular target tissues during drug treatment via topical, subconjunctival, intravitreal, or systemic routes. Mathematical models encompass various barriers so that their joint influence on pharmacokinetics (PKs) can be simulated in an integrated fashion. The models are useful in predicting PKs and even pharmacodynamics (PDs) of administered drugs thereby fostering development of new drug molecules and drug delivery systems. Furthermore, the models are potentially useful in interspecies translation and probing of disease effects on PKs. In this review article, we introduce current modeling methods (noncompartmental analyses, compartmental and physiologically based PK models, and finite element models) in ocular PKs and related drug delivery. The roles of top-down models and bottom-up simulations are discussed. Furthermore, we present some future challenges, such as modeling of intra-tissue distribution, prediction of drug responses, quantitative systems pharmacology, and possibilities of artificial intelligence.

Evaluation of Dose-Response Relationship in Novel Extended Release of Targeted Nucleic Acid Nanocarriers to Treat Secondary Cataracts

Purpose: The present study aimed to determine the dose-response relationship between targeted nanocarriers released from a novel, sustained release formulation and their ability to specifically deplete cells responsible for the development of posterior capsular opacification (PCO) in month-long, dynamic cell cultures. Methods: Injectable, thermosensitive poly(D,L-lactic-co-glycolic acid)-b-poly(ethylene glycol)-b-poly(D,L-lactic-co-glycolic acid) triblock copolymer hydrogels were loaded with either a low or a high dose of doxorubicin-loaded antibody-targeted nanocarriers (G8:3DNA:Dox). Human rhabdomyosarcoma cells, selected for their expression of PCO marker brain-specific angiogenesis inhibitor 1 (BAI1), were kept under dynamic media flow and received either a low or high dose of nanocarriers. Cells were fixed and stained at predetermined time points to evaluate targeted depletion of BAI1+ cells. Results: A lower dose of nanocarriers in hydrogel depleted BAI1+ cells at a slower rate than the higher dose, whereas both reached over 90% BAI1+ cellular nonviability at 28 days. Both treatment groups also significantly lowered the relative abundance of BAI1+ cells in the population compared with the control group. Conclusions: Controlled release of a lower dose of nanocarriers can still achieve therapeutically relevant effects in the prevention of PCO, while avoiding potential secondary effects associated with the administration of a higher dose.

Anterior Segment Complications Following Intravitreal Injection

Intravitreal injections (IVI s) have gained increased popularity in the past decades and are used to treat a multitude of ailments. In 2010, the total number of IVI s surpassed the number of cataract surgeries performed, making it the most common procedure in ophthalmology. As the number of injections increases, so does the number of injected-related complications. While complications in the posterior segment, such as retinal detachment or endophthalmitis, are detrimental to visual function and have therefore been well documented, IVI s can also lead to complications in the anterior segment. These include hyphema, inflammation of the sterile anterior segment (incidence rate of 0.05 to 1.1% depending on the drug), implant migration with corneal decompensation (incidence rate of 0.43%), iatrogenic lens damage (incidence rate of 0.07%), accelerated cataract formation (up to 50% for steroids and 10.9% for anti-VEGF), and an increased complication rate during subsequent cataract surgery (up to 4% per IVI). Most of these complications occur immediately and have a good prognosis if treated correctly. However, the increased risk of complications during subsequent surgery demonstrates that IVI s can also have long-term complications, a topic that needs to be explored further in future research projects.

Utilizing extracellular vesicles as a drug delivery system in glaucoma and RGC degeneration

Retinal diseases are the leading cause of blindness, resulting in irreversible degeneration and death of retinal neurons. One such cell type, the retinal ganglion cell (RGC), is responsible for connecting the retina to the rest of the brain through its axons that make up the optic nerve and is the primary cell lost in glaucoma and traumatic optic neuropathy. To date, different therapeutic strategies have been investigated to protect RGCs from death and preserve vision, yet currently available strategies are restricted to treating neuron loss by reducing intraocular pressure. A major barrier identified by these studies is drug delivery to RGCs, which is in large part due to drug stability, short duration time at target, low delivery efficiency, and undesired off-target effects. Therefore, a delivery system to deal with these problems is needed to ensure maximum benefit from the candidate therapeutic material. Extracellular vesicles (EV), nanocarriers released by all cells, are lipid membranes encapsulating RNAs, proteins, and lipids. As they naturally shuttle these encapsulated compounds between cells for communicative purposes, they may be exploitable and offer opportunities to overcome hurdles in retinal drug delivery, including drug stability, drug molecular weight, barriers in the retina, and drug adverse effects. Here, we summarize the potential of an EV drug delivery system, discussing their superiorities and potential application to target RGCs.

Cationic-motif-modified exosomes for mRNA delivery to retinal photoreceptors

Topical treatment of vitreoretinal diseases remains a challenge due to slow corneal uptake and systemic clearance. Exosomes are emerging nanocarriers for drug delivery due to biocompatibility and cellular targeting properties. To apply them for retinal targeting via the topical route, exosomes must traverse various ocular barriers including the cornea, lens, vitreous humor (VH), and the retina itself. Here we engineered high-purity milk-derived exosomes by anchoring arginine-rich cationic motifs via PEG2000 lipid insertion on their surface. Modification enabled exosomes to use weak-reversible electrostatic interactions with anionic glycosaminoglycan (GAG) and water content of the tissue to enhance their transport rate and retention. Addition of cationic motifs neutralized the anionic surface charge of exosomes (-24 to -2 mV) without impacting size or morphology. Cationic-motif-modified exosomes exhibited two-fold faster steady state diffusivity through bovine corneas compared to unmodified exosomes. Fluorescence recovery after photobleaching confirmed that cationic-motif-modified exosomes can diffuse through VH without steric hindrance. In healthy VH, cationic-motif-modified exosomes demonstrated stronger binding resulting in three-fold lower average diffusivity that enhanced by six-fold in 50% GAG-depleted VH recapitulating advanced liquefaction. Cationic-motif-modified exosomes penetrated through the full-thickness of porcine retinal explants resulting in ten-fold higher uptake in photoreceptors and three-fold greater transfection with encapsulated eGFP mRNA compared to unmodified exosomes. Cationic-motif-modified exosomes are safe to use as they did not adversely affect the mechanical swelling properties of the cornea or lens nor impact retinal cell viability. Cationic-motif-modified exosomes, therefore, offer themselves as a cell-free nanocarrier platform for gene delivery to retinal photoreceptors potentially via the topical route.

Efficient retinal ganglion cells transduction by retro-orbital venous sinus injection of AAV-PHP.eB in mature mice

Gene therapy is one of the strategies that may reduce or reverse progressive neurodegeneration in retinal neurodegenerative diseases. However, efficiently delivering transgenes to retinal ganglion cells (RGCs) remains hard to achieve. In this study, we innovatively investigated transduction efficiency of adeno-associated virus (AAV)-PHP.eB in murine RGCs by retro-orbital venous sinus injection. Five doses of AAV-PHP.eB-EGFP were retro-orbitally injected in venous sinus in adult C57/BL6J mice. Two weeks after administration, RGCs transduction efficiency was quantified by retinal flat-mounts and frozen section co-labeling with RGCs marker Rbpms. In addition, safety of this method was evaluated by RGCs survival rate and retinal morphology. To conform efficacy of this new method, AAV-PHP.eB-CNTF was administrated into mature mice through single retro-orbital venous injection after optic nerve crush injury to evaluate axonal elongation. Results indicated that AAV- PHP.eB readily crossed the blood-retina barrier and was able to transduce more than 90% of RGCs when total dose of virus reached 5 × 1010 vector genomes (vg). Moreover, this technique did not affect RGCs survival rate and retinal morphology. Furthermore, retro-orbital venous delivery of AAV-PHP.eB-CNTF effectively transduced RGCs, robustly promoted axonal regeneration after optic nerve crush injury. Thus, novel AAV-PHP.eB retro-orbital injection provides a minimally invasive and efficient route for transgene delivery in treatment of retinal neurodegenerative diseases.

Clinical features, management, and outcomes of patients with sterile endophthalmitis associated with intravitreal bevacizumab injection: retrospective case series

PURPOSE

To evaluate clinical features, treatment protocol, outcomes, and complications that developed in this case series of 24 patients who had consecutive sterile endophthalmitis after intravitreal bevacizumab (IVB) injection.

METHODS

In this retrospective case series, IVB was repackaged in individual aliquots from the three batches that were used on the same day. IVB was injected into 26 eyes of 26 patients due to diabetic macular edema, age-related macular degeneration, and branch retinal vein occlusion. All patients had intraocular inflammation. Patients were divided into two groups severe and moderate inflammation according to the intraocular inflammation. The medical records of all patients were reviewed. At each follow-up visit, the complete ophthalmologic examination was performed, including best corrected visual acuity (BCVA), intraocular pressure, biomicroscopy, and posterior fundus examination.

RESULTS

Twenty-four of 26 patients were included in the study. Two patients were excluded from this study since they didn't come to follow-up visits. The mean BCVA was 1.00 ± 0.52 Log MAR units before IVB. At the final visit, the BCVA was 1.04 ± 0.47 Log MAR units. These differences were not significant (p = 0.58). Of the 24 eyes, 16 eyes had severe, and 8 eyes had moderate intraocular inflammation. Eleven eyes in the severe inflammation group underwent pars plana vitrectomy due to intense vitreous opacity. Smear, culture results, and polymerase chain reaction results were negative.

CONCLUSION

Sterile endophthalmitis may occur after IVB injection. Differential diagnosis of sterile endophthalmitis from infective endophthalmitis is crucial to adjust the appropriate treatment and prevent long-term complications due to unnecessary treatment.

Focused Ultrasound as a Novel Non-Invasive Method for the Delivery of Gold Nanoparticles to Retinal Ganglion Cells

Purpose

The blood-retinal barrier (BRB) restricts the delivery of intravenous therapeutics to the retina, necessitating innovative approaches for treating retinal disorders. This study sought to explore the potential of focused ultrasound (FUS) to non-invasively deliver intravenously administered gold nanoparticles (AuNPs) across the BRB. FUS-BRB modulation can offer a novel method for targeted retinal therapy.

Methods

AuNPs of different sizes and shapes were characterized, and FUS parameters were optimized to permeate the BRB without causing retinal damage in a rodent model. The delivery of 70-kDa dextran and AuNPs to the retinal ganglion cell (RGC) layer was visualized using confocal and two-photon microscopy, respectively. Histological and statistical analyses were conducted to assess the effectiveness and safety of the procedure.

Results

FUS-BRB modulation resulted in the delivery of dextran and AuNPs to the RGC and inner nuclear layer. Smaller AuNPs reached the retinal layers to a greater extent than larger ones. The delivery of dextran and AuNPs across the BRB with FUS was achieved without significant retinal damage.

Conclusions

This investigation provides the first evidence, to our knowledge, of FUS-mediated AuNP delivery across the BRB, establishing a foundation for a targeted and non-invasive approach to retinal treatment. The results contribute to developing promising non-invasive therapeutic strategies in ophthalmology to treat retinal diseases.

Translational Relevance

Modifying the BRB with ultrasound offers a targeted and non-invasive delivery strategy of intravenous therapeutics to the retina.

Acute Noninfectious Anterior Ocular Inflammation Following Ranibizumab Biosimilar Intravitreal Injection in a Patient With Recent COVID-19 Vaccination

Even in the post-coronavirus disease 2019 (COVID-19) era, it is prudent to exercise caution regarding the timing between intravitreal anti-vascular endothelial growth factor (VEGF) injections and COVID-19 vaccinations, as ocular inflammation can occur following both procedures. However, this perspective has not been sufficiently discussed thus far. Herein, we report a case of acute noninfectious anterior ocular inflammation following an intravitreal injection of ranibizumab biosimilar (RBZ BS, Senju Pharmaceuticals, Japan) in a patient recently vaccinated against COVID-19. A 74-year-old male with myopic choroidal neovascularization (CNV) in the left eye was treated with RBZ BS intravitreal injection. He received his fourth COVID-19 vaccination with messenger ribonucleic acid (mRNA)-1273 (Moderna) two days prior to his second RBZ BS intravitreal injection. He reported no systemic symptoms associated with the fourth COVID-19 vaccination. The second RBZ BS intravitreal injection was safely performed without complications. However, a few hours later, he experienced blurred vision without ocular pain in his left eye, a symptom not observed after the first injection. He visited a local ophthalmologic clinic the following day and was subsequently referred to our hospital due to anterior ocular inflammation in the left eye. His vision in the left eye was 0.3 decimal best-corrected visual acuity. Examination revealed non-granulomatous anterior ocular inflammation with 3+ cells and 2+ flare in the left eye. Anterior vitreous inflammation, keratic precipitates, or conjunctivitis was absent. Fundus examination also showed no signs of posterior inflammation. Both fluorescence angiography and indocyanine green angiography revealed staining corresponding to CNV without retinal vasculature leakage. There is nothing abnormal with the right eye based on the examination. Given that the noninfectious ocular inflammation was likely, based on the acute onset of symptoms within less than 24 hours following the RBZ BS intravitreal injection, and the presence of non-granulomatous inflammation only in the anterior segment without ocular pain, betamethasone eye drops four times daily was initiated in the left eye on the first day following the second RBZ BS intravitreal injection. Then, his ocular inflammation improved to mild by the fourth day post-injection. His eye eventually cleared, with no cells or flare in the anterior chamber at five months. Eventually, given the clinical course of good response to only topical steroid therapy, the diagnosis of noninfectious anterior ocular inflammation following RBZ BS in the case of a recent episode of COVID-19 vaccination was retrospectively confirmed. Although this case represents one of the initial instances of noninfectious ocular inflammation following RBZ BS (Senju Pharmaceuticals) administration, sterile ocular inflammation after other intravitreal anti-VEGF therapy has already been well-reported. In addition, given the recent COVID-19 vaccination, the ocular inflammation might be influenced by the vaccination, synergistically leading to vaccine-associated uveitis with similar signs and symptoms. In conclusion, to prevent such a complex situation, it is advisable to consider an adequate interval between COVID-19 vaccination and intravitreal anti-VEGF injections.

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.

Dose-Related Side Effects of Intravitreal Injections of Humanized Anti-Vascular Endothelial Growth Factor in Rats: Glial Cell Reactivity and Retinal Ganglion Cell Loss

Purpose

In a previous study, we documented that the Intravitreal injections (IVIs) of bevacizumab in rats caused a retinal inflammatory response. We now study whether the IVI of other humanized anti-VEGF: ranibizumab and aflibercept also cause an inflammatory reaction in the rat retina and if it depends on the dose administered. Finally, we study whether this reaction affects retinal ganglion cell (RGC) survival.

Methods

Albino Sprague-Dawley rats received a single IVI of 5 µL of PBS or ranibizumab or aflibercept at the concentration used in clinical practice (10 µg/µL or 40 µg/µL) or at a lower concentration (0.38 µg/µL and 1.5 µg/µL) calculated to obtain within the rat eye the same concentration as in the human eye in clinical practice. Others received a single 5 µL IVI of a polyclonal goat anti-rat VEGF (0.015 µg/µL) or of vehicle (PBS). Animals were processed 7 days or 1 month later. Retinal whole mounts were immunolabeled for the detection of microglial, macroglial, RGCs, and intrinsically photosensitive RGCs (ipRGCs). Fluorescence and confocal microscopy were used to examine retinal changes, and RGCs and ipRGCs were quantified automatically or semiautomatically, respectively.

Results

All the injected substances including the PBS induced detectable side effects, namely, retinal microglial cell activation and retinal astrocyte hypertrophy. However, there was a greater microglial and macroglial response when the higher concentrations of ranibizumab and aflibercept were injected than when PBS, the antibody anti-rat VEGF and the lower concentrations of ranibizumab or aflibercept were injected. The higher concentration of ranibizumab and aflibercept resulted also in significant RGC death, but did not cause appreciable ipRGC death.

Conclusions

The IVI of all the substances had some retinal inflammatory effects. The IVI of humanized anti-VEGF to rats at high doses cause important side effects: severe inflammation and RGC death, but not ipRGC death.

Injectable, Antioxidative, and Tissue-Adhesive Nanocomposite Hydrogel as a Potential Treatment for Inner Retina Injuries

Reactive oxygen species (ROS) have been recognized as prevalent contributors to the development of inner retinal injuries including optic neuropathies such as glaucoma, non-arteritic anterior ischemic optic neuropathy, traumatic optic neuropathy, and Leber hereditary optic neuropathy, among others. This underscores the pivotal significance of oxidative stress in the damage inflicted upon retinal tissue. To combat ROS-related challenges, this study focuses on creating an injectable and tissue-adhesive hydrogel with tailored antioxidant properties for retinal applications. GelCA, a gelatin-modified hydrogel with photo-crosslinkable and injectable properties, is developed. To enhance its antioxidant capabilities, curcumin-loaded polydopamine nanoparticles (Cur@PDA NPs) are incorporated into the GelCA matrix, resulting in a multifunctional nanocomposite hydrogel referred to as Cur@PDA@GelCA. This hydrogel exhibits excellent biocompatibility in both in vitro and in vivo assessments, along with enhanced tissue adhesion facilitated by NPs in an in vivo model. Importantly, Cur@PDA@GelCA demonstrates the potential to mitigate oxidative stress when administered via intravitreal injection in retinal injury models such as the optic nerve crush model. These findings underscore its promise in advancing retinal tissue engineering and providing an innovative strategy for acute neuroprotection in the context of inner retinal injuries.

Disease quiescence in endophthalmitis patients treated with anti-VEGF injections for retinal pathologies

BACKGROUND

The most feared complication of intravitreal injections is the development of endophthalmitis, which could lead to irreversible visual loss. The aim of this study was to characterize the clinical profiles, causative pathogens, and clinical outcome of patients post-endophthalmitis.

METHODS

Retrospective, single center case series study. Clinical records, causative pathogens and management of all cases of endophthalmitis post intravitreal anti-vascular endothelial growth factor (VEGF) injections recorded between January 1st, 2006 and May 30th, 2022; were retrieved. The visual and anatomic changes prior to the episode of endophthalmitis and up to 2 years post-treatment were compared.

RESULTS

Eleven post-injection endophthalmitis eyes of 10 patients (n = 3 females; 30%) were recruited at mean age of 64.5 ± 20.4 years. The median last recorded BCVA, up to 3 months prior to the episode of endophthalmitis was 60 (Interquartile range (IQR) 55-75) ETDRS letters. Then, it dropped to 30 (IQR 0-57.5), 35 (IQR 0-52.5) and 35 (IQR 0-57.5) ETDRS letters at presentation, 6- and 12-months follow-up; respectively (p = 0.027, p = 0.017 and p = 0.012). However, at 24 months, the median BCVA returned to similar baseline values prior to the episode of endophthalmitis; BCVA 50 (IQR 0-60) ETDRS letters, p = 0.062. Interestingly, two eyes with neovascular age-related macular degeneration (NVAMD), 1 with myopic choroidal neovascularization (CNV) and 1 with retinal vein occlusion (RVO), experienced disease quiescence and did not require additional anti-VEGF injections up to 2 years of follow-up.

CONCLUSION

This study demonstrates long-term recovery of vision loss due to endophthalmitis post anti-VEGF injections, regained up to 2 years later. It also indicates that disease quiescence post endophthalmitis may not only occur in eyes treated for NVAMD, but also with myopic CNV and RVO.

Neurogenic dry eye associated with intravitreal injection of anti-VEGF agents

PURPOSE

To report a case of neurogenic dry eye (NDE) that developed after intravitreal ranibizumab injection (IVR).

CASE REPORT

A 71-year-old woman had a history of cataract phacoemulsification and intraocular lens (IOL) implantation, Nd:YAG laser posterior capsulotomy and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK). Aneurysmal dilatation of the inferior temporal retina was found in the left fundus, which was diagnosed as retinal aneurysm, and intravitreal ranibizumab injection was administered. Dry eye was found in the left eye after the first injection. After the second injection, the patient developed severe dry eye with left eye dryness, photophobia, irritation, and blurred vision. The tear film breakup time (TBUT) value was 3 s, the Schirmer test value was 2 mm/5 min, corneal fluorescein staining (CFS) showed diffuse patellar staining of the corneal epithelium with a staining area of >50% and irregular staining at the edge of the corneal flap, and the corneal touch threshold value in the filament length was 1.5 cm in the left eye.

CONCLUSIONS

Patients with a history of intraocular lens implantation, Nd:YAG laser posterior capsulotomy, and femtosecond laser-assisted laser in situ keratomileusis surgery may have increased drug permeability due to an increased concentration of anti-VEGF drugs in the aqueous layer and thinning of the stromal layer of the cornea. The corneal subepithelial nerve repair mechanism was destroyed, causing neurogenic dry eye.

Pain control and subconjunctival haemorrhage after intravitreal injection using cooled anaesthetic eyedrops and antiseptics: A prospective, double-blind, randomized controlled trial

PURPOSE

To evaluate whether cooled anaesthetic eyedrops and antiseptics alleviate pain and minimise subconjunctival haemorrhage following intravitreal injection.

METHODS

A prospective, double-masked, randomised controlled trial of 100 participants receiving either cooled (n = 50) or room temperature (n = 50) topical anaesthetic eyedrops and antiseptics before receiving an injection of bevacizumab. Baseline tolerability was estimated using a self-reported pain sensitivity questionnaire.

RESULTS

Overall tolerability was comparable between the study group and the control group (0.75 ± 0.13 vs. 0.74 ± 0.14, respectively, p = 0.99). Subconjunctival haemorrhage incidence was similar in both groups (80% vs. 86%, respectively, p = 0.113), as was subconjunctival haemorrhage size (2.75 ± 5.51 mm2 vs. 5.53 ± 10.72 mm2 , respectively, p = 0.11). Sub-group analysis demonstrated that the participants taking daily ocular eyedrops who received cooled anaesthetic eyedrops and antiseptics reported less pain at 10 min and less burning sensation at 24 h compared with matched controls (0.67 ± 1.50 vs. 2.50 ± 3.03, respectively, p = 0.040 and 0.00 ± 0.00 vs. 1.44 ± 2.96, respectively, p = 0.045). Participants who received cooled eyedrops and did not use antithrombotic therapy had smaller-sized subconjunctival haemorrhages compared with matched controls (1.55 ± 1.87 mm2 vs. 8.29 ± 14.61 mm2 , respectively, p = 0.038). Participants with hypertension who received cooled eyedrops had smaller-sized subconjunctival haemorrhage compared with matched controls (2.33 ± 4.99 mm2 vs. 6.89 ± 12.41 mm2 , respectively, p = 0.045).

CONCLUSION

The benefit of using cooled anaesthetic eyedrops and antiseptics to alleviate pain and minimise subconjunctival haemorrhage following intravitreal injection was not proven in the general population. It may be beneficial in part for some patients, such as those who regularly use eyedrops, patients with hypertension or those not on antithrombotic therapy.

Quantitative intravitreal pharmacokinetics in mouse as a step towards inter-species translation

Although mouse models are widely used in retinal drug development, pharmacokinetics in mouse eye is poorly understood. In this study, we applied non-invasive in vivo fluorophotometry to study pharmacokinetics of intravitreal fluorescein sodium (molecular weight 0.38 kDa) and fluorescein isothiocyanate-dextran (FD-150; molecular weight 150 kDa) in mice. Intravitreal half-lives of fluorescein and FD-150 in mouse eyes were 0.53 ± 0.06 h and 2.61 ± 0.86 h, respectively. These values are 8-230 times shorter than the elimination half-lives of similar compounds in the human vitreous. The apparent volumes of distribution in the mouse vitreous were close to the anatomical volume of the mouse vitreous (FD-150, 5.1 μl; fluorescein, 9.6 μl). Dose scaling factors were calculated from mouse to rat, rabbit, monkey and human translation. Based on pharmacokinetic modelling and compound concentrations in the vitreous and anterior chamber, fluorescein is mainly eliminated posteriorly across blood-retina barrier, but FD-150 is cleared via aqueous humour outflow. The results of this study improve the knowledge of intravitreal pharmacokinetics in mouse and facilitate inter-species scaling in ocular drug development.

Solid implantable devices for sustained drug delivery

Implantable drug delivery systems (IDDS) are an attractive alternative to conventional drug administration routes. Oral and injectable drug administration are the most common routes for drug delivery providing peaks of drug concentrations in blood after administration followed by concentration decay after a few hours. Therefore, constant drug administration is required to keep drug levels within the therapeutic window of the drug. Moreover, oral drug delivery presents alternative challenges due to drug degradation within the gastrointestinal tract or first pass metabolism. IDDS can be used to provide sustained drug delivery for prolonged periods of time. The use of this type of systems is especially interesting for the treatment of chronic conditions where patient adherence to conventional treatments can be challenging. These systems are normally used for systemic drug delivery. However, IDDS can be used for localised administration to maximise the amount of drug delivered within the active site while reducing systemic exposure. This review will cover current applications of IDDS focusing on the materials used to prepare this type of systems and the main therapeutic areas of application.

Randomized Controlled Study of Cooled vs Room-Temperature Artificial Tears for Reducing Ocular Surface Irritation After Intravitreal Injection

Purpose: To evaluate the efficacy of cooled vs room-temperature artificial tears in reducing ocular discomfort after intravitreal injections (IVIs). Methods: Patients receiving a standard intravitreal injection in the retina clinic who met the eligibility criteria and provided informed consented were enrolled in the study. Patients were randomized to the cooled tears or room-temperature tears intervention group. Both groups rated their ocular discomfort following IVI after cooled or room-temperature tears were administered. Results: The cooled group comprised 48 patients and the room-temperature group, 61 patients. There was no significant difference in the reduction of ocular discomfort between the cooled vs room-temperature artificial tears groups (P = .387). In addition, there was a similar level of reduction in ocular discomfort after either intervention (P = .681) regardless of whether or not the patients routinely used artificial tears after previous IVIs. Conclusions: Cooled tears provided no additional benefit in reducing ocular discomfort post-IVI compared with room-temperature tears. Baseline tear use after an IVI may have no true benefit other than a potential placebo effect, recall bias, or both.

Novel oral medications for retinal disease: an update on clinical development

PURPOSE OF REVIEW

Intravitreal and periocular injections for retinal disease provide a targeted delivery of medication to the eye. However, given risks of injections, including endophthalmitis, pain and treatment burden for both patients and retina specialists, there has been significant interest and effort in developing oral medications for the management of retinal disease. This article provides clinical and preclinical details of new oral medications in the pipeline for management of retinal disease.

RECENT FINDINGS

Several new oral medications show clinical and preclinical promise for the management of retinal disease, including macular degeneration, diabetic retinopathy and Stargardt disease.

SUMMARY

Oral medications provide promise for treating retinal disease, possibly increasing compliance, and reducing side effects of intravitreal or periocular injections. However, difficulties in this approach include systemic side effects and efficacy targeting the eye. There are multiple medications that are currently under investigation with the potential to act as stand-alone treatment or as an adjunct treatment for management of retinal diseases such as diabetic retinopathy, macular degeneration and Stargardt disease.

Emerging strategies of engineering retinal organoids and organoid-on-a-chip in modeling intraocular drug delivery: current progress and future perspectives

Retinal diseases are a rising concern as major causes of blindness in an aging society; therapeutic options are limited, and the precise pathogenesis of these diseases remains largely unknown. Intraocular drug delivery and nanomedicines offering targeted, sustained, and controllable delivery are the most challenging and popular topics in ocular drug development and toxicological evaluation. Retinal organoids (ROs) and organoid-on-a-chip (ROoC) are both emerging as promising in-vitro models to faithfully recapitulate human eyes for retinal research in the replacement of experimental animals and primary cells. In this study, we review the generation and application of ROs resembling the human retina in cell subtypes and laminated structures and introduce the emerging engineered ROoC as a technological opportunity to address critical issues. On-chip vascularization, perfusion, and close inter-tissue interactions recreate physiological environments in vitro, whilst integrating with biosensors facilitates real-time analysis and monitoring during organogenesis of the retina representing engineering efforts in ROoC models. We also emphasize that ROs and ROoCs hold the potential for applications in modeling intraocular drug delivery in vitro and developing next-generation retinal drug delivery strategies.

Systemic Outcomes of Intravitreal Injections of Dexamethasone and Anti-Vascular Endothelial Growth Factor

INTRODUCTION

Intravitreal dexamethasone and anti-vascular endothelial growth factor (anti-VEGF) medications have revolutionized ocular disease management and favorable ocular safety profiles, but few studies have compared their systemic adverse events (SAEs). This study investigated the SAEs of intravitreal dexamethasone and anti-VEGFs by using real-world data.

METHODS

This retrospective cohort study sourced medical records from the largest multi-institutional database in Taiwan. Patients who received intravitreal dexamethasone (n = 137) or anti-VEGFs (n = 10,345) between 2014 and 2019 were enrolled. Propensity score matching was performed to achieve homogeneity between the two groups. Subdistribution hazard ratios (SHRs) and 95% confidence intervals (CIs) were calculated using the Fine-Gray model. Systemic as well as ocular clinical events and systemic biomarkers after 1-year follow-up were compared.

RESULTS

Both groups demonstrated comparable risks of major cardiac adverse events (SHR 1.57, 95% CI 0.29-8.55), heart failure (SHR 0.62, 95% CI 0.07-5.33), major bleeding (SHR 0.23, 95% CI 0.03-1.77), all-cause admission (SHR 0.73, 95% CI 0.41-1.30), and all-cause death (SHR 2.11, 95% CI 0.35-12.71). There were no significant differences in longitudinal changes in systolic and diastolic blood pressure, glycated hemoglobin, low-density lipoprotein, estimated glomerular filtration rate, or alanine aminotransferase between the groups. Both groups had a similar incidence of cataract surgery. Although the dexamethasone group exhibited a relatively high prevalence of antiglaucomatous medication use, there was not a significantly higher incidence of glaucoma surgery.

CONCLUSION

Intravitreal dexamethasone and anti-VEGF medications had comparable systemic safety profiles in our study. Both drugs represent efficacious and safe therapies for ocular diseases.

Intravitreal Fluocinolone Acetonide Implant (ILUVIEN®) for the Treatment of Retinal Conditions. A Review of Clinical Studies

Fluocinolone acetonide (FAc) intravitreal implant (Iluvien®) is a corticosteroid implant indicated for the treatment of diabetic macular oedema (DMO) in patients who have previously received conventional treatment without good response, non-infectious posterior uveitis, and as an off-label treatment of the macular oedema secondary to retinal vein occlusion. FAc is a non-biodegradable 0.19 mg intravitreal implant which is designed to release FAc over 3 years at a rate of approximately 0.2 mcg per day. The aim of this review is to describe the special pharmacological properties of Iluvien and display the outcomes of the most important clinical trials and real-world studies regarding its efficacy and safety for the management of the above retinal disorders.

Pulsed Ultrasound-Mediated Enhancement on Transscleral and Transconjunctival Fluorescein Sodium Delivery to Rabbit Eye In Vivo

Purpose: To investigate the efficacy and safety of pulsed ultrasound (PUS) in enhancing fluorescein sodium (NaF) transport to the rabbit eye through the transscleral and transconjunctival routes in vivo. Methods: PUS and NaF were applied onto the supratemporal sclera/conjunctiva of healthy rabbit eyes. PUS (1 MHz, 2.37 W/cm2, 30% duty cycle, 5-min application time) was performed 3 times with a 5-min interval. In the same process, NaF was administered to the eye without PUS in the control. NaF concentrations in the vitreous and retina-choroid were determined by fluorescence measurement. The safety of PUS application was assessed based on temperature and intraocular pressure measurements, clinical observations, electroretinography, histology, and Terminal Deoxynucleotidyl Transferase dUTP Nick End Labeling assay. Results: In comparison to the control, higher NaF concentrations were found in the retina-choroid following transscleral (2.45-fold) and transconjunctival (2.97-fold) PUS applications (P < 0.05). NaF concentrations in the vitreous were 3.15 and 5.86 times greater in transscleral and transconjunctival PUS applications, respectively, compared with those obtained without PUS application (P < 0.05), and NaF level in the vitreous after transconjunctival PUS application was 2.61 times that of transscleral PUS application (P < 0.05). Ocular findings were transient and mild conjunctival injection, with no other structural and functional changes in PUS-treated eyes. Conclusions: PUS treatment can improve transscleral and transconjunctival delivery of NaF efficiently and safely. Transscleral and transconjunctival PUS applications offer potential clinical benefit in increasing drug penetration to the posterior segments of the eye for the noninvasive treatment of ocular diseases.

Innovation in the Development of Synthetic and Natural Ocular Drug Delivery Systems for Eye Diseases Treatment: Focusing on Drug-Loaded Ocular Inserts, Contacts, and Intraocular Lenses

Nowadays, ocular drug delivery still remains a challenge, since the conventional dosage forms used for anterior and posterior ocular disease treatments, such as topical, systemic, and intraocular administration methods, present important limitations mainly related to the anatomical complexity of the eye. In particular, the blood-ocular barrier along with the corneal barrier, ocular surface, and lacrimal fluid secretion reduce the availability of the administered active compounds and their efficacy. These limitations have increased the need to develop safe and effective ocular delivery systems able to sustain the drug release in the interested ocular segment over time. In the last few years, thanks to the innovations in the materials and technologies employed, different ocular drug delivery systems have been developed. Therefore, this review aims to summarize the synthetic and natural drug-loaded ocular inserts, contacts, and intraocular lenses that have been recently developed, emphasizing the characteristics that make them promising for future ocular clinical applications.

Targeted Nanotherapies for the Posterior Segment of the Eye: An Integrative Review on Recent Advancements and Challenges

The eye is a one-of-a-kind sensory organ with intricate anatomy and physiology. It is protected by a variety of barriers, ranging from static barriers to dynamic barriers. Although these barriers are very effective at protecting the eye from exogenous substances and external stress, they are highly compromised by various vision-impairing diseases of both the anterior and the posterior segment of the eye. Due to ocular elimination systems and intricate obstacles that selectively limit drug entry into the eye, effective drug delivery to the posterior segment of the eye (PSE) continues to be a challenge in ophthalmology. Since more than half of the most debilitating eye illnesses are thought to originate in the posterior segment (PS), understanding the physiology and clearance mechanism of the eye could help design improved formulations that could be noninvasive and intended for targeted posterior segment therapeutics. Moreover, the major drawback associated with the conventional drug delivery system to PSE is minimal therapeutic drug concentration in the desired ocular tissue and life-threatening ophthalmic complications. One possible approach that can be implemented to overcome these ocular barriers for efficient ocular therapy, non-invasive and targeted drug action to the posterior tissues is by designing nanomedicines. This review summarizes the recent non-invasive and patient compliant advances in designing nanomedicines targeting PSE. The various routes and pathways of drug administration to the ocular tissue are also summarized.

Received anti-VEGF therapy in a patient with CRAO sparing the CLRA with subretinal fluid: A case report

RATIONALE

Central retinal artery occlusion (CRAO) sparing the cilioretinal artery (CLRA) with severe subretinal fluid and non-characteristic cherry-red spot is uncommon. In the present case, the patient received an intravitreal injection of anti- vascular endothelial growth factor, which is very rare.

PATIENT CONCERNS

A 59-year-old man underwent vitrectomy of the left eye for diabetic retinopathy and vitreous hemorrhage. Six months after the operation, the patient presented with sudden painless visual-acuity decline in his left eye and was diagnosed with CRAO; his best corrected visual acuity was weak light perception. Whole retinal edema was seen on the fundus, and macular gray retinal opacification was present without a characteristic cherry-red spot. Optical coherence tomography revealed subretinal fluid (SRF) in the papillomacular bundle and inner retinal thickening. Fundus fluorescein angiography confirmed that the central retinal artery was not filled at 40 seconds and that the CLRA supplied a part of the macular area. Eight months after the second intravitreal injection of ranibizumab, Optical coherence tomography showed a significant reduction in inner retinal hyperreflectivity and the thickness of the nasal macular retina. The SRF was clearly absorbed, and the visual acuity improved to 1.1 logMAR units.

DIAGNOSIS

Atypical CRAO.

INTERVENTIONS

The patient was treated with intravitreal injection of anti-VEGF in his left eye. The thickness of the nasal macular retina decreased.

OUTCOMES

The SRF was clearly absorbed, and the patient's visual acuity significantly improved.

LESSONS

When CRAO occurs in patients with diabetic retinopathy sparing the CLRA, the non-characteristic cherry-red spot may be due to macular inner retinal edema, SRF and other factors. According to the patient's condition, anti-vascular endothelial growth factor can be administered as appropriate to inhibit choroidal neovascularization, reduce SRF in the macular retina, and save some vision.

Newly-established in vitro inner BRB spheroids to elucidate retinal Ang2-linked substance transfer

Conjugation of angiopep-2 (Ang2) with drugs/compounds is known to increase plasma membrane permeability across endothelial barriers. The inner blood-retinal barrier (BRB) regulates retinal drug distribution and is formed by retinal capillary endothelial cells, supported by Müller cells and retinal pericytes. To elucidate the potential of Ang2 conjugation in promoting retinal drug distribution after peripheral administration across the inner BRB, an in vivo administration study and in vitro transport experiments using newly developed multicellular inner BRB spheroids were performed. After intravenous administration of Ang2-linked green fluorescence protein (GFP-Ang2) in mice, GFP-derived signals were observed in the neural retina. In contrast, GFP-derived signals were not observed after intravenous GFP administration, suggesting the promotion of the retinal distribution of substances by Ang2 conjugation. To overcome the limitations of in vitro studies using cells cultured on dishes, inner BRB spheroids were established using conditionally immortalized rat retinal capillary endothelial cells, Müller cells, and retinal pericytes. Immunocytochemistry of marker molecules suggests that the central part of the spheroids is occupied by Müller cells, and encapsulated by retinal pericytes and capillary endothelial cells. Studies on the expression and functions of tight junctions suggest that tight junctions are formed on the surface of the inner BRB spheroids by retinal capillary endothelial cells. The functional expression of drug transporters, such as P-glycoprotein, was observed in the spheroids, implying that the inner side of the spheroids reflects the retinal side of the inner BRB. In the inner BRB spheroids, energy-dependent accumulation of GFP-Ang2 and Ang2-linked 5(6)-carboxyfluorescein (FAM-Ang2) was observed. Moreover, an endocytic inhibition study revealed that clathrin-dependent endocytosis/transcytosis was involved in the transcellular transport of Ang2-conjugated drugs/compounds across the inner BRB. Consequently, it is suggested that the Ang2 linkage is useful for promoting retinal drug distribution via clathrin-dependent transcytosis at the inner BRB.

Advances in biomaterials for the treatment of retinoblastoma

Retinoblastoma is the most common primary intraocular malignancy in children. Although traditional chemotherapy has shown some success in retinoblastoma management, there are several shortcomings to this approach, including inadequate pharmacokinetic parameters, multidrug resistance, low therapeutic efficiency, nonspecific targeting, and the need for adjuvant therapy, among others. The revolutionary developments in biomaterials for drug delivery have enabled breakthroughs in cancer management. Today, biomaterials are playing a crucial role in developing more efficacious retinoblastoma treatments. The key goal in the evolution of drug delivery biomaterials for retinoblastoma therapy is to resolve delivery-associated obstacles and lower nonlocal exposure while ameliorating certain adverse effects. In this review, we will first delve into the historical perspective of retinoblastoma with a focus on the classical treatments currently used in clinics to enhance patients' quality of life and survival rate. As we move along, we will discuss biomaterials for drug delivery applications. Various aspects of biomaterials for drug delivery will be dissected, including their features and recent advances. In accordance with the current advances in biomaterials, we will deliver a synopsis on the novel chemotherapeutic drug delivery strategies and evaluate these approaches to gain new insights into retinoblastoma treatment.

Long-acting injectable formulation technologies: Challenges and opportunities for the delivery of fragile molecules

INTRODUCTION

The development of long acting injectables (LAIs) for protein and peptide therapeutics has been a key challenge over the last 20 years. If these molecules offer advantages due to their high specificity and selectivity, their controlled release may confer several additional benefits in terms of extended half-life, local delivery, and patient compliance.

AREA COVERED

This manuscript aims to give an overview of peptide and protein based LAIs from an industrial perspective, describing both approved and promising technologies (with exceptions of protein engineering strategies and devices), their advantages and potential improvements to aid their access to the market.

EXPERT OPINION

Many LAIs have been developed for peptides, with formulations on the market for several decades. On the contrary, LAIs for proteins are still far from the market and issues related to manufacturing and sterilization of these products still need to be overcome. In situ forming depots (ISFDs), whose simple manufacturing conditions and easy administration procedures (without reconstitution) are strong advantages, appear as one of the most promising technologies for the delivery of these molecules. In this regard, the approval of ELIGARD® in the early 2000's (which still requires a complex reconstitution process), paved the way for the development of second-generation, ready-to-use ISFD technologies like BEPO® and FluidCrystal®.

Simultaneous Release of Aflibercept and Dexamethasone from an Ocular Drug Delivery System

PURPOSE

Intravitreal injections of anti-vascular endothelial growth factors (anti-VEGF) are the current standard of care for patients with choroidal neovascularization (CNV) secondary to age-related macular degeneration (AMD). There is a growing subset of patients that does not respond to anti-VEGF monotherapy treatment. Some patients, however, do respond to combination therapy of corticosteroids and anti-VEGF. This treatment requires monthly/bimonthly injections of anti-VEGF and semi-annual injections of corticosteroid. A drug delivery system (DDS) that simultaneously releases multiple drugs could benefit these patients by reducing the number of injections. The purpose of this study was to characterize the simultaneous release of aflibercept and dexamethasone from a biodegradable microparticle- and nanoparticle-hydrogel DDS.

METHODS

Dexamethasone-loaded nanoparticles and aflibercept-loaded microparticles were created using modified single- and double-emulsion techniques, respectively. Then, microparticles and nanoparticles were embedded into a thermoresponsive, biodegradable poly(ethylene glycol)-co-(L-lactic acid) diacrylate (PEG-PLLA-DA)-N-isopropylacrylamide (NIPAAm) hydrogel DDS. Drug release studies and characterization of DDS were conducted with varying doses of microparticles and nanoparticles.

RESULTS

The combination aflibercept-loaded microparticle- and dexamethasone-loaded nanoparticle- hydrogel (Combo-DDS) achieved a total release time of 224 days. Small decreases were seen in swelling ratio and equilibrium water content for Combo-DDS compared to monotherapy aflibercept-loaded microparticle-hydrogel DDS (AFL-DDS) and monotherapy dexamethasone-loaded nanoparticle-hydrogel DDS (DEX-DDS). Bioactivity of aflibercept was maintained in Combo-DDS compared to AFL-DDS.

CONCLUSIONS

The Combo-DDS was able to extend and control the release of both aflibercept and dexamethasone simultaneously from a single DDS. This may eliminate the need for separate dosing regiments of anti-VEGF and corticosteroids for wet AMD patients.

Molecular Mechanisms Underlying the Therapeutic Role of Vitamin E in Age-Related Macular Degeneration

The eye is particularly susceptible to oxidative stress and disruption of the delicate balance between oxygen-derived free radicals and antioxidants leading to many degenerative diseases. Attention has been called to all isoforms of vitamin E, with α-tocopherol being the most common form. Though similar in structure, each is diverse in antioxidant activity. Preclinical reports highlight vitamin E’s influence on cell physiology and survival through several signaling pathways by activating kinases and transcription factors relevant for uptake, transport, metabolism, and cellular action to promote neuroprotective effects. In the clinical setting, population-based studies on vitamin E supplementation have been inconsistent at times and follow-up studies are needed. Nonetheless, vitamin E’s health benefits outweigh the controversies. The goal of this review is to recognize the importance of vitamin E’s role in guarding against gradual central vision loss observed in age-related macular degeneration (AMD). The therapeutic role and molecular mechanisms of vitamin E’s function in the retina, clinical implications, and possible toxicity are collectively described in the present review.

Targeting Ocular Drug Delivery: An Examination of Local Anatomy and Current Approaches

Ocular drug delivery remains the focus of much modern research. Primary routes of administration include the surface, the intravitreal space, the subretinal space, and the subconjunctival space, each with its own series of unique challenges, limitations, and advantages. Each of these approaches requires careful consideration of the local anatomy, physical barriers, and key cells as well as the interface between the anatomy and the drug or drug system being delivered. While least invasive, the topical route poses a challenge with the many physical barriers that prevent drug penetration into the eye; while injection into the intravitreal, subretinal, and subconjunctival spaces are direct and targeted but limited due to the many internal clearance mechanisms and potential for damage to the eye. Polymeric-based, sustained-release drug delivery systems have been identified as a potential solution to many of these challenges; however, the design and successful implementation of a sustained-release system that is well-tolerated, bioactive, biocompatible, and degradable remains, in many cases, only in the early stages. The drugs and biomaterials in question also require special attention as small chemical changes could result in vastly different outcomes. This paper explores the anatomy and key cells of these four primary drug delivery routes as well as the interface between drug and drug delivery systems and the anatomy, reviewing the recent developments and current state of research in each area. Finally, this paper also examines the frequently used drugs and biomaterials found in ocular drug delivery and summarizes the primary interactions observed.

Non-human primates in the PKPD evaluation of biologics: Needs and options to reduce, refine, and replace. A BioSafe White Paper

Monoclonal antibodies (mAbs) deliver great benefits to patients with chronic and/or severe diseases thanks to their strong specificity to the therapeutic target. As a result of this specificity, non-human primates (NHP) are often the only preclinical species in which therapeutic antibodies cross-react with the target. Here, we highlight the value and limitations that NHP studies bring to the design of safe and efficient early clinical trials. Indeed, data generated in NHPs are integrated with in vitro information to predict the concentration/effect relationship in human, and therefore the doses to be tested in first-in-human trials. The similarities and differences in the systems defining the pharmacokinetics and pharmacodynamics (PKPD) of mAbs in NHP and human define the nature and the potential of the preclinical investigations performed in NHPs. Examples have been collated where the use of NHP was either pivotal to the design of the first-in-human trial or, inversely, led to the termination of a project prior to clinical development. The potential impact of immunogenicity on the results generated in NHPs is discussed. Strategies to optimize the use of NHPs for PKPD purposes include the addition of PD endpoints in safety assessment studies and the potential re-use of NHPs after non-terminal studies or cassette dosing several therapeutic agents of interest. Efforts are also made to reduce the use of NHPs in the industry through the use of in vitro systems, alternative in vivo models, and in silico approaches. In the case of prediction of ocular PK, the body of evidence gathered over the last two decades renders the use of NHPs obsolete. Expert perspectives, advantages, and pitfalls with these alternative approaches are shared in this review.

Anterior Chamber Paracentesis Offers a Less Painful Experience During Intravitreal Anti-vascular Endothelial Growth Factor Administration: An Intraindividual Study

Introduction: In order to improve comfort and compliance to treatment of the patient during the intravitreal injections (IVIs), relieving pain may help and provide getting better results. The purpose of the study was to evaluate the efficacy of anterior chamber paracentesis on pain perception and the factors related to pain perception during intravitreal injection procedures.

Material and methods: This prospective randomized study includes 212 eyes of 106 patients scheduled for bilateral IVI of ranibizumab 0.5 mg/0.05 cc under topical anesthesia. All patients underwent full ophthalmologic examination, including intraocular pressure (IOP), anterior chamber depth (ACD), and axial length (AL) measurements. Group 1 received IVI following anterior chamber paracentesis (ACP) and group 2 received IVI without ACP. Intraocular pressure was measured five minutes and 30 minutes after the procedure. Pain perception was assessed by visual analogue scale (VAS) grading from 0 to 10.

Results: Mean VAS score for groups 1 and 2 was recorded as 0.51±1.00 and 1.32±1.50, respectively. Correlation analysis revealed a positive correlation between VAS score and history of previous IVI, preinjection IOP values, and an inverse correlation with the presence of reflux in both groups, in addition to inverse correlation with ACD in group 2.

Conclusions: ACP may offer a comfortable, effective, and less painful alternative to prevent the acute rise in IOP after IVI, especially in patients with small anterior chambers, small vitreous volumes, with a history of multiple injections, and in patients with advanced glaucomatous optic neuropathy.

Recent advances in ophthalmic preparations: Ocular barriers, dosage forms and routes of administration

The human eye is a complex organ with unique anatomy and physiology that restricts the delivery of drugs to target ocular tissues/sites. Recent advances in the field of pharmacy, biotechnology and material science have led to development of novel ophthalmic dosage forms which can provide sustained drug delivery, reduce dosing frequency and improve the ocular bioavailability of drugs. This review highlights the different anatomical and physiological factors which affect ocular bioavailability of drugs and explores advancements from 2016 to 2020 in various ophthalmic preparations. Different routes of drug administration such as topical, intravitreal, intraocular, juxtascleral, subconjunctival, intracameral and retrobulbar are discussed with their advances and limitations.

Acute Retinal Necrosis in an Immunocompetent Patient Treated With Intravitreal Ganciclovir

Acute retinal necrosis (ARN) is an inflammatory syndrome of high clinical concern; untreated or misdiagnosed cases may progress to optic neuropathy or retinal detachment, leading to irreversible blindness. ARN affects men and women equally and is often seen in immunocompromised patients but is also known to present in immunocompetent patients. It is usually due to systemic viral infection with secondary vitreoretinal inflammation. Most commonly, the first-line management of ARN is oral or intravenous antiviral therapy. Here, we report the case of an immunocompetent patient presenting with necrotizing retinopathy secondary to ARN. This patient was treated with oral valacyclovir and then intravenous acyclovir with no improvement. However, intravitreal injection of ganciclovir successfully halted the progression of ARN and led to the preservation of vision in the patient.

Age-related ocular conditions: Current treatments and role of cyclodextrin-based nanotherapies

Age-related eye disorders are chronic diseases that affect millions of people worldwide. They cause visual impairment and, in some cases, irreversible blindness. Drug targeting to the retina is still a challenge due to the difficulties with drug distribution, crossing eye barriers, and reaching intraocular tissues in an effective therapeutic concentration. Although intravitreal injections can directly deliver drugs to the posterior segment of the eye, it remains an invasive technique and leads to several side effects. Conventional formulations such as emulsions, suspensions, or ointments have been related to frequent instillation and inability to reach intraocular tissues. New drug delivery systems and medical devices have also been designed. Nevertheless, these treatments are not always effective and sometimes require the presence of a specialist for the administration of the dose. Therefore, treatments for age-related ocular diseases remain as one of the major unmet clinical needs to manage these widespread eye conditions. Nanotechnology may become the adequate tool for developing effective and non-invasive therapies suitable for self-administration. In this review, we discuss emerging therapeutic options based on nanoengineering of cyclodextrin nanocarriers for the treatment of age-related eye disorders, including their pathophysiology, pharmacological options, and feasibility of clinical translation.

Mechanisms of sterile inflammation after intravitreal injection of antiangiogenic drugs: a narrative review

BACKGROUND

Intraocular inflammation is an uncommon but potentially vision-threatening adverse event related to anti-VEGF therapy. This is of increasing importance given both the volume of injections performed, as well as the increased prevalence of inflammation seen with newer anti-VEGF agents. Brolucizumab, the newest anti-VEGF agent, has been associated with an inflammatory retinal vasculitis and the underlying mechanism is unclear. Reviewing potential mechanisms and clinical differences of intraocular inflammation may assist clinicians and scientists in reducing the risk of these events in the future.

OBSERVATIONS

Two types of inflammation are seen with intravitreal injections, acute onset sterile inflammation and delayed onset inflammatory vasculitis. Acute onset inflammation can be subcategorized into subclinical anterior chamber inflammation and sterile uveitis/endophthalmitis. Subclinical anterior chamber inflammation can occur at rates as high as 19% after intravitreal anti-VEGF injection. Rates of sterile uveitis/endophthalmitis range from 0.05% to 4.4% depending on the anti-VEGF agent. Inflammatory vasculitis is only associated with brolucizumab and occurred in 3.3% of injections according to the post hoc review of the HAWK/HARRIER data. In addition, silicone oil from syringes can induce immunogenic protein aggregates. Agitation of the syringe, freeze thawing, shipping and improper storage prior to injection may increase the amount of silicone oil released from the syringe.

CONCLUSION

The main factors which play a role in intraocular inflammation after anti-VEGF injection can be divided into three causes: patient-specific, medication-specific and delivery-specific. The majority of clinically significant inflammation seen after intravitreal injection is an acute onset inflammatory response with most patients recovering baseline VA in 3-5 weeks. The presence of pain, hypopyon, severe anterior chamber reaction, hyperemia and significant vision loss may help distinguish infectious from non-infectious etiologies of post injection inflammation. Avoiding temperature fluctuation, mechanical shock, agitation during transport and handling of syringes/drugs, and the use of SO-free syringes may help minimize intraocular inflammation. While a definitive mechanism has not yet been established, current knowledge of the clinical presentation and vitreous histopathology of brolucizumab-retinal vasculitis favors an auto-immune type IV hypersensitivity reaction.

Intravitreal injection of povidone-iodine for the treatment of vancomycin-resistant Enterococcus faecalis endophthalmitis in rabbit eyes

The aim of this study was to investigate the efficacy of intravitreal povidone-iodine (PI) in the treatment of vancomycin-resistant Enterococcus faecalis (VRE) endophthalmitis. Fifty New Zealand white rabbits were divided into 5 groups (n = 10 in each group). After the induction of endophthalmitis using VRE (minimum inhibitory concentration [MIC] ≥ 40 μg/mL) in the right eye, Group A, B, C, and D received intravitreal injections of 0.1% PI, 0.3% PI, 0.05% vancomycin, and 0.5% vancomycin, respectively. Eyes in Group E were used as controls. Fundus photography, vitreous culture, electroretinography (ERG), and histologic examinations of the retina were conducted on day 14. A marked improvement in endophthalmitis was observed in Group A, B, C and D, compared to Group E. Fundus photographs showed mild vitreous opacities in Group A and B, and moderate vitreous opacity in Group C. All eyes in Group D had a clear vitreous. In vitreous culture, bacterial growth was found in 6 eyes (100, 200, 200, 400, 500, and 500 colony-forming units) in Group C, but not in Groups A, B, or D. ERG and histological examination also indicated intraocular damage in Group C. Our results show that intravitreal injection of PI, even at low concentrations, was effective for treatment of VRE endophthalmitis, although some vitreous opacity remained. Intravitreal vancomycin injection was also useful to treat resistant strains, if used at a higher concentration within the safety threshold.

SELF-DESIGNATION OF THE TREATED EYE BEFORE INTRAVITREAL INJECTIONS: Prevalence and Predictors of Incorrect Calling

PURPOSE

To identify risk factors for incorrect self-identification of the treatment eye before intravitreal injections.

METHODS

This prospective study included consecutive patients who were asked to designate the eye for which the intravitreal injection was intended and were subsequently divided into two groups according to whether or not they identified the correct eye.

RESULTS

Overall, 349 eyes (n = 349) were included, and 8.6% (n = 30) designated the incorrect eye or did not know which eye was intended for treatment. Incorrect designation was associated with diabetic macular edema (odds ratio [OR] = 0.33 [0.15-0.75]), first injection in the intended eye or ≥1 year since previous injection (OR = 0.34 [0.14-0.87]), Arabic native tongue (OR = 0.48 [0.22-1.01]), previous injection to the fellow eye (OR = 0.26 [0.10-0.64]), and concurrent treatment of both eyes (OR = 0.35 [0.16-0.74]). Multivariate analysis showed the first injection or ≥1 year since last injection in the treatment eye (R2 = 2.24%, P = 0.004, OR = 0.20 [0.07-0.57]) and previous injection in the fellow eye (R2 = 6.55%, P < 0.001, OR = 0.20 [0.07-0.52]) as significant independent predictors of incorrect identification.

CONCLUSION

Several factors are associated with a greater probability for incorrect patient's self-identification of the eye laterality intended for intravitreal injections. These findings may help identify patients with a higher risk of such potential errors.

Effect of Penetration Angle and Velocity During Intravitreal Injection on Pain

Purpose: To evaluate the effect of velocity and angle of the intravitreal injection of anti-vascular endothelial growth factors on pain sensation.Methods: Patients were randomly assigned to one of four injection methods: straight and fast, straight and slow, tunneled and fast, and tunneled and slow. Later, they graded their pain sensation on a Visual Analog Scale (range 0-10).Results: The cohort included 180 patients. Mean pain score was 2.81 ± 2.34. There was no statistically significant difference in mean pain score among the four groups (p = .858); between the slow-injection (straight and tunneled) and fast-injection groups (p = .514); and between the straight-injection (fast and slow) and tunneled-injection groups (p = .992), nor other background variables.Conclusion: Velocity and angle of intravitreal injections are unrelated to the pain sensation. Therefore, the method may be left to the clinician's discretion. This implies that the sensation is mostly subjective.

The influence of dead spaces and the designs of injectors on the amount of drug dose in intra-vitreal injection

AIM

To evaluate the dead spaces resulting from different designs of the insulin injectors used for intravitreal injections and the amounts of drug doses.

METHODS

In the study, five different brands of sterile insulin injectors of 1 mL were used for the test. The weight of the injectors was determined before and after filling the injectors with 0.05 and 0.1 mL distilled water. The weight of the injectors was measured with and without the needle after the water within the injectors had been taken out and weight differences were measured. The difference between the intended amount of fluid to be thrown out and the weight of the fluid remaining in the injector was calculated as percent error.

RESULTS

After throwing out 0.05 mL distilled water from the injector, weights of the Beybi^®, Traf^®, Becton Dickinson^®, Ayset^®, and Setojet^® brands of injectors with 30 G needle were detected to increase the mean 0.0220 ± 0.006 g, 0.0208 ± 0.008 g, 0.0355 ± 0.016 g, 0.0219 ± 0.017 g, and 0.0150 ± 0.007 g, respectively compared to the weights of the dry injectors. The 0.1 mL injector group was found to be mean 0.0350 ± 0.014 g, 0.0264 ± 0.008 g, 0.0405 ± 0.015 g, 0.0272 ± 0.013 g, and 0.0245 ± 0.014 g, respectively. The maximum increase due to the dead spaces in the injectors was found in the Becton Dickinson^® injector, both in the 0.05 mL and the 0.1 mL groups (p < 0.000).

CONCLUSION

The injector designs may affect the dose of IVI required to be given. More correct amounts of drugs may be administered via the intra-vitreal route through designs that reduce the dead spaces at the end part of the injector and between the inner wall and the plunger.

Formulation of nanoliposome-encapsulated bevacizumab (Avastin): Statistical optimization for enhanced drug encapsulation and properties evaluation

Bevacizumab (Avastin®), an anti-vascular endothelial growth factor, is one of the most effective drugs widely used to inhibit ocular angiogenesis. Nanoliposomes were recruited to improve the accessibility of bevacizumab (BVZ) during treatment. To optimize drug entrapment efficiency (DEE %), the effect of some independent variables was evaluated utilizing response surface methodology. The optimized formulation containing BVZ (NLP-BVZ) was characterized, and its safety was assessed. Employingarising retinalpigment epithelial (ARPE) cells, the permeability of the nanoliposome was analyzed. Structural stability and integrity of NLP-BVZ were also estimated with different methods. Optimal condition for the maximum DEE (39.9%) was obtained with cholesterol/DPPC (1,2-Dipalimitoyl-Sn-glycero-3-phosphocholine) (%w/w) 13.64, BVZ/DPPC (%w/w) 83.78 and 9 freeze-thaw cycles. Neutral fabricated NLP-BVZ with an average size of 141.5 ± 45.8 nm showed a smooth spherical structure and released the drug in a slow and sustained fashion. The formulation exhibited no obvious effect against human umbilical vein endothelial cells (HUVECs) and ARPEs. Additionally, the pattern of the circular dichroism (CD) and intrinsic fluorescence spectra confirmed the structural integrity of protein remained conserved after encapsulation. Taken together, the analysis indicated that the process of entrapment into nanoliposome meaningfully made the drug safer, more stable, and, therefore, appropriate for treating ocular disorders.

Regulation of the Ocular Cell/Tissue Response by Implantable Biomaterials and Drug Delivery Systems

Therapeutic advancements in the treatment of various ocular diseases is often linked to the development of efficient drug delivery systems (DDSs), which would allow a sustained release while maintaining therapeutic drug levels in the target tissues. In this way, ocular tissue/cell response can be properly modulated and designed in order to produce a therapeutic effect. An ideal ocular DDS should encapsulate and release the appropriate drug concentration to the target tissue (therapeutic but non-toxic level) while preserving drug functionality. Furthermore, a constant release is usually preferred, keeping the initial burst to a minimum. Different materials are used, modified, and combined in order to achieve a sustained drug release in both the anterior and posterior segments of the eye. After giving a picture of the different strategies adopted for ocular drug release, this review article provides an overview of the biomaterials that are used as drug carriers in the eye, including micro- and nanospheres, liposomes, hydrogels, and multi-material implants; the advantages and limitations of these DDSs are discussed in reference to the major ocular applications.

Intravitreal injection of resveratrol inhibits laser-induced murine choroidal neovascularization

AIM

To determine the effects of intravitreal resveratrol (RSV) on murine laser-induced choroidal neovascularization (CNV).

METHODS

The toxicity of RSV to choroidal endothelial cell (CEC) was measured using thiazolyl blue tetrazolium bromide (MTT) assay. Effects of RSV on choroidal endothelial cell (CEC) migration were evaluated with a modified Boyden chamber assay, while tube formation was evaluated in a 2-D gel assay. CNV was induced by laser photocoagulation in mice. The effects of intravitreal injection of RSV on CNV development were evaluated by fluorescein angiography (FA), confocal analysis of isolectin B4 labeled choroidal flat mounts, and histologic examination of CNV membranes. Immunostaining was used to analyze the expression and phosphorylation of vascular endothelial growth factor receptor 2 (VEGFR2).

RESULTS

No significant cell toxicity was observed in CEC if the concentration of RSV was less than 200 µmol/L (P>0.05). RSV inhibited vascular endothelial growth factor (VEGF)-induced CEC migration (P<0.05) and tube formation (P<0.05) in vitro. Furthermore, intravitreal injection of RSV significantly inhibited laser induced CNV formation in mice. The FA leakage, CNV volume and CNV area analysis revealed that there were 41%, 45%, and 58% reduction in RSV-treated eyes (1.691±0.1032, 178 163±78 623 µm³ and 6508±619.0 µm², respectively) compared with those in control (2.724±0.08447, 379 676±98 382 µm³ and 16 576±2646 µm², respectively; P<0.05). Phospho-VEGFR2 expression was much weaker in the sections of CNV lesions in RSV injected mice compared with that in control (P<0.05).

CONCLUSION

Intravitreal injection of RSV exerts an inhibitory effect on CNV, which may through suppressing endothelial cell migration, tube formation and VEGFR2 phosphorylation.

Focused ultrasound as a novel strategy for noninvasive gene delivery to retinal Müller glia

Müller glia are specialized retinal cells with stem cell properties in fish and frogs but not in mammals. Current efforts to develop gene therapies to activate mammalian Müller glia for retinal repair will require safe and effective delivery strategies for recombinant adeno-associated viruses (AAVs), vectors of choice for clinical translation. Intravitreal and subretinal injections are currently used for AAV gene delivery in the eye, but less invasive methods efficiently targeting Müller glia have yet to be developed. Methods: As gene delivery strategies have been more extensively studied in the brain, to validate our vectors, we initially compared the glial tropism of AAV-PHP.eB, an AAV9 that crosses the blood-brain and blood-retinal barriers, for its ability to drive fluorescent protein expression in glial cells in both the brain and retina. We then tested the glial transduction of AAV2/8-GFAP-mCherry, a virus that does not cross blood-brain and blood-retinal barriers, for its effectiveness in transducing Müller glia in murine retinal explants ex vivo. For in vivo assays we used larger rat eyes, performing invasive intravitreal injections, and non-invasive intravenous delivery using focused ultrasound (FUS) (pressure amplitude: 0.360 - 0.84 MPa) and microbubbles (Definity, 0.2 ml/kg). Results: We showed that AAV-PHP.eB carrying a ubiquitous promoter (CAG) and green fluorescent protein (GFP) reporter, readily crossed the blood-brain and blood-retinal barriers after intravenous delivery in mice. However, murine Müller glia did not express GFP, suggesting that they were not transduced by AAV-PHP.eB. We thus tested an AAV2/8 variant, which was selected based on its safety record in multiple clinical trials, adding a glial fibrillary acidic protein (GFAP) promoter and mCherry (red fluorescent protein) reporter. We confirmed the glial specificity of AAV2/8-GFAP-mCherry, showing effective expression of mCherry in astrocytes after intracranial injection in the mouse brain, and of Müller glia in murine retinal explants. For in vivo experiments we switched to rats because of their larger size, injecting AAV2/8-GFAP-mCherry intravitreally, an invasive procedure, demonstrating passage across the inner limiting membrane, leading to Müller glia transduction. We then tested an alternative non-invasive delivery approach targeting a different barrier - the inner blood-retinal-barrier, applying focused ultrasound (FUS) to the retina after intravenous injection of AAV2/8 and microbubbles in rats, using magnetic resonance imaging (MRI) for FUS targeting. FUS permeabilized the rat blood-retinal-barrier and allowed the passage of macromolecules to the retina (Evans blue, IgG, IgM), with minimal extravasation of platelets and red blood cells. Intravenous injection of microbubbles and AAV2/8-GFAP-mCherry followed by FUS resulted in mCherry expression in rat Müller glia. However, systemic delivery of AAV2/8 also had off-target effects, transducing several murine peripheral organs, particularly the liver. Conclusions: Retinal permeabilisation via FUS in the presence of microbubbles is effective for delivering AAV2/8 across the inner blood-retinal-barrier, targeting Müller glia, which is less invasive than intravitreal injections that bypass the inner limiting membrane. However, implementing FUS in the clinic will require a comprehensive consideration of any off-target tropism of the AAV in peripheral organs, combined ideally, with the development of Müller glia-specific promoters.

Intravitreal Injections with Vascular Endothelial Growth Factor Inhibitors: A Practical Approach

Intravitreal injections with vascular endothelial growth factor inhibitors constitute the most prevalent ophthalmic procedure in developed countries. Historically, there has been steady growth in the number of treatments performed of this kind, and projection studies estimate further growth in such treatments in the future. We provide a practical approach to intravitreal injections and discuss important aspects relating to the setting, the patient, the procedure, and the information given to the patient.