Intravitreal injections: A review of pharmacological agents and techniques

Comprehensive Pharmacokinetic Evaluation of High Melanin Binder Levofloxacin in Rabbits Shows Potential of Topical Eye Drops for Posterior Segment Treatment

Purpose

The purpose of this work was to understand the impact of melanin binding on ocular pharmacokinetics after administration of a high-binder model drug via different administration routes.

Methods

We applied levofloxacin to pigmented and albino rabbits as eye drops (single and multiple), as well as by intravitreal and intravenous injections. Ocular tissues and plasma were analyzed for levofloxacin concentrations with liquid chromatography-mass spectrometry (LC-MS/MS), and pharmacokinetic parameters were calculated.

Results

The data show enrichment of levofloxacin and weeks-long retention in pigmented tissues. Upon intravitreal injection, the area under the curve (AUC) values in pigmented tissues were about 9 to 15 times higher than the respective values in the albino rabbits, but this difference expanded to 255- to 951-fold following topical eye drop administration. Multiple dosing of eye drops led to substantial accumulation of levofloxacin in the pigmented tissues: AUC values were 3 to 12 times higher than after intravitreal injection. The AUCs were much lower after single topical or intravenous drug administrations. High drug levels (0.1-35 µM) were always observed in the neural retinas of pigmented eyes; the highest exposure was seen after intravitreal administration followed by multiple doses of topical drops. Single topical instillation and intravenous injections to the albino rabbits resulted in vitreal bioavailability values of 0.009% and 0.003%, respectively.

Conclusions

Melanin binding can be used to achieve targeted drug delivery and extended retention in pigmented ocular tissues. The results from topical multiple dosing experiments suggest that eye drop treatment may yield drug exposures and responses comparable to intravitreal delivery, even in the retinal pigment epithelium and choroid.

Short-Term Effects of Brolucizumab in the Treatment of Wet Age-Related Macular Degeneration or Polypoidal Choroidopathy Refractory to Previous Anti-Vascular Endothelial Growth Factor Therapy

Background and objectives: To report the initial response to a single intravitreal brolucizumab (IVI-B) injection in wet age-related macular degeneration (wAMD) or polypoidal choroidopathy (PCV) complicated with either persistent subretinal fluid (SRF) or pigment epithelial detachment refractory to previous anti-vascular endothelial growth factor (anti-VEGF) therapy. Material and methods: In this retrospective study, all eyes received a single IVI-B (6 mg/0.05 mL) for wAMD or PCV with treatment-resistant SRF or PED. Outcome measures included assessment in central retinal thickness (CRT), visual acuity, and evaluation for changes in the SRF or PED on OCT. Follow-up was prior to the first brolucizumab injection, then at 1 week and 5 weeks afterwards. Results: In total, 10 eyes of 10 patients (6 women [60%]) were enrolled. Five patients had wAMD and five patients had PCV. Average age of participants was 67.6 years. All patients received one IVI-B. All patients were not treatment-naïve to anti-VEGF agents. At the first week and fifth week following the first IVI-B, seven out of seven patients (100%) had resolved SRF. However, seven out of nine patients (78%) had no improvement of their PED at 5 weeks follow-up. Mean PED height and width before the first IVI-B was 339.77 µm and 2233.44 µm, respectively. Mean PED height and width at the fifthweek following the first IVI-B was 328.125 µm and 2129.5 µm, respectively. Overall mean visual acuity before the first IVI-B was 0.224; and 5 weeks following the first IVI-B was 0.38. Conclusions: Treatment with brolucizumab resulted in anatomical improvement for all patients with persistent SRF. Limited efficacy was seen for persistent PED. Brolucizumab appears to be a safe and effective option for treatment-resistant SRF. Future multicenter collaborative studies are warranted.

Short- and Long-Term Visual Outcomes in Patients Receiving Intravitreal Injections: The Impact of the Coronavirus 2019 Disease (COVID-19)-Related Lockdown

Purpose: To investigate the short- and long-term impact of COVID-19—related lockdown on the vision of patients requiring intravitreal injections (IVI) for neovascular Age-related Macular degeneration (nvAMD), diabetic retinopathy (DR), central retinal vein occlusion (CRVO), or branch retinal vein occlusion (BRVO). Methods: This is a retrospective study from the Retina department of three Mass Eye and Ear centers. Charts of patients age of ≥ 18 years with any of the abovementioned diagnoses who had a scheduled appointment anytime between 17 March 2020 until 18 May 2020 (lockdown period in Boston, Massachusetts) were reviewed at baseline (up to 12 weeks before the lockdown), at first available follow-up (=actual f/u) during or after the lockdown period, at 3 months, 6 months, and at last available completed appointment of 2020. Results: A total of 1001 patients met the inclusion criteria. Of those patients, 479 (47.9%) completed their intended f/u appointment, while 522 missed it (canceled and “no show”). The delay in care of those who missed it was 59.15 days [standard deviation (SD) ± 49.6]. In these patients, significant loss of vision was noted at actual f/u [Best corrected visual acuity (BCVA) in LogMAR (Logarithm of the Minimum Angle of Resolution)—mean (±SD)—completed: 0.45 (±0.46), missed: 0.53 (±0.55); p = 0.01], which was more prominent in the DR group [Visual acuity (VA) change in LogMAR—mean (±SD); completed: 0.04 (±0.28), missed: 0.18 (±0.44); p = 0.02] and CRVO [completed: −0.06 (±0.27), missed: 0.11 (±0.35); p = <0.001] groups followed by nvAMD [completed: 0.006 (±0.16), missed: 0.06 (±0.27); p = 0.004] and BRVO [completed: −0.02 (±0.1), missed: 0.03 (±0.14); p = 0.02] ones. Overall, a higher percent of people who missed their intended f/u experienced vision loss of more than 15 letters at last f/u compared to those who completed it [missed vs. completed; 13.4% vs. 7.4% in nvAMD (p = 0.72), 7.8% vs. 6.3% in DR (0.84), 15.5% vs. 9.9% in CRVO (p < 0.001) and 9.6% vs. 2% in BRVO (p = 0.48)]. Conclusions: Delay in care of about 8.45 weeks can lead to loss of vision in patients who receive IVI with DR and CRVO patients being more vulnerable in the short-term, whereas in the long-term, CRVO patients followed by the nvAMD patients demonstrating the least vision recovery. BRVO patients were less likely to be affected by the delay in care. Adherence to treatment is key for maintaining and improving visual outcomes in patients who require IVI.

Magnetically Assisted Drug Delivery of Topical Eye Drops Maintains Retinal Function In Vivo in Mice

Barded-Biedl syndrome (BBS) is a rare genetic disorder with an unmet medical need for retinal degeneration. Small-molecule drugs were previously identified to slow down the apoptosis of photoreceptors in BBS mouse models. Clinical translation was not practical due to the necessity of repetitive invasive intravitreal injections for pediatric populations. Non-invasive methods of retinal drug targeting are a prerequisite for acceptable adaptation to the targeted pediatric patient population. Here, we present the development and functional testing of a non-invasive, topical, magnetically assisted delivery system, harnessing the ability of magnetic nanoparticles (MNPs) to cargo two drugs (guanabenz and valproic acid) with anti-unfolded protein response (UPR) properties towards the retina. Using magnetic resonance imaging (MRI), we showed the MNPs' presence in the retina of Bbs wild-type mice, and their photoreceptor localization was validated using transmission electron microscopy (TEM). Subsequent electroretinogram recordings (ERGs) demonstrated that we achieved beneficial biological effects with the magnetically assisted treatment translating the maintained light detection in Bbs^-/- mice (KO). To our knowledge, this is the first demonstration of efficient magnetic drug targeting in the photoreceptors in vivo after topical administration. This non-invasive, needle-free technology expands the application of SMDs for the treatment of a vast spectrum of retinal degenerations and other ocular diseases.

TOXIC POSTERIOR SEGMENT SYNDROME AFTER DROPLESS CATARACT SURGERY WITH COMPOUNDED TRIAMCINOLONE-MOXIFLOXACIN

PURPOSE

To report toxic posterior segment syndrome after dropless cataract surgery using locally compounded triamcinolone-moxifloxacin.

METHODS

A retrospective case review of 7 patients presenting with a decrease in visual acuity after dropless cataract surgery.

RESULTS

All patients experienced significant reductions in best-corrected visual acuity of the postoperative eye ranging from 20/40 to count finger at 4 feet (average best-corrected visual acuity 20/220) immediately after surgery. The presenting symptoms included flashes, floaters, photophobia, glare, halos, visual distortions, and problems assessing colors. In three cases, foveal retinal pigment epithelium changes were noted on dilated fundus exam (DFE). Ellipsoid zone loss was noted on ocular coherence tomography in five of the seven affected eyes. Electrophysiology testing in five of the seven affected eyes demonstrated large decreases in full-field electroretinogram amplitude, oscillatory potentials, multifocal electroretinogram, and visual evoked potential, along with a negative electroretinogram. One patient was treated with a dexamethasone implant, but no improvement in visual acuity was noted.

CONCLUSION

This is the first case series of toxic posterior segment syndrome occurring secondary to intracameral compounded triamcinolone-moxifloxacin in dropless cataract surgery. The FDA has attributed the toxicity to abnormally high levels of the binding agent poloxamer 407 in the compounded medication. Clinicians should be aware of this phenomenon and exhibit caution when using compounded medications.

Novel Needle for Intravitreal Drug Delivery: Comparative Study of Needle Tip Aspirates, Injection Stream and Penetration Forces

Purpose

To study the efficacy of a novel needle for intravitreal injection (IVI) in comparison to the conventional needle under experimental conditions.

Methods

The newly designed 30-gauge (G) needle (NDN) (EP 18158 542.3, patent pending) with occluded outer orifice and a side port for drug delivery was compared to the conventional standard hypodermic 30 G needle for IVI (SHN). An animal study to obtain needle tip aspirates was performed on 10 albino rat eyes. During IVIs, cellular content, which was cut by the needle tip, was aspirated. Cellular material was studied in regard to cell types and their quantity. The injection stream was studied using trypan blue dye in vitro and pig cadaver eyes. The penetration force was tested on polyurethane Testing Foil Strips PU 04 (Melab, Leonberg, Germany) by applying a velocity of 100 mm/min. The results were analyzed using descriptive statistics, correlation matrices and t-test methods with p<0.05 as statistically significant.

Results

Cytological analysis of the needle aspirates showed the presence of cellular content in each case. The amount of conjunctival, ciliary body epithelial cells and granulated basophilic protein sediments (sign of cellular damage) in the case of the NDN tips was significantly lower compared to the SHN. The average penetration force of the NDN was 0.791 N, and in the case of the SHN was 0.566 N. The injection stream study revealed a difference in the initial injection phase between the two needle types, although the diffuse filling of the vitreous area which surrounded the needle tip appeared to be similar.

Discussion

The NDN demonstrated superior performance with regard to a significantly reduced number of cells being captured by the needle tip. Delivery of the injected fluid into the vitreous cavity was comparable. In order to investigate superior properties of the NDN needle design, further studies with improved prototypes would be necessary.

Retinal photoreceptors targeting SA-g-AA coated multilamellar liposomes carrier system for cytotoxicity and cellular uptake evaluation

Here, the retinal targeting SA-g-AA coated multilamellar liposomes carrier synthesized to deliver the bioactive agents into the retinal region of the eye. The multilayered targeting macromolecules of liposomes prepared using a layer-by-layer assembly. The curcumin (CUR) and Rhodamine B (RhB) dyes loaded in a multilamellar vesicle (MLV) were synthesised by the lipid film hydration method. The sodium alginate grafted acrylic acid (SA-g-AA) conjugated with riboflavin (RB) was coated over MLV by O/W emulsion method followed by ionotropic gelation. FT-IR and ¹H NMR spectroscopy techniques used to analyse the structural features of the MLV-SA-g-AA-RB. The results of DLS and TEM revealed that the carrier could be of uniform spheres, with a low polydispersity index, and outstanding performance in phrases of dye encapsulation and extended-release ability. An MTT assay investigated cell viability against Fibroblast WS1, and human embryonic stem cells-derived retinal pigment epithelial cells (hESC-RPE) implied that the carrier is of excellent biocompatibility. Retina targeting nature of the system confirmed via cellular uptake results revealed that the increases the dye concentration in the cells. Overall, the outcomes suggested that carriers could lead to the improvement of a feasible two photoreceptors targeting drug carriers, and it has the potential to deliver the multidrug in the retinal region of the eye.

Drug Delivery to the Posterior Segment of the Eye: Biopharmaceutic and Pharmacokinetic Considerations

The treatment of the posterior-segment ocular diseases, such as age-related eye diseases (AMD) or diabetic retinopathy (DR), present a challenge for ophthalmologists due to the complex anatomy and physiology of the eye. This specialized organ is composed of various static and dynamic barriers that restrict drug delivery into the target site of action. Despite numerous efforts, effective intraocular drug delivery remains unresolved and, therefore, it is highly desirable to improve the current treatments of diseases affecting the posterior cavity. This review article gives an overview of pharmacokinetic and biopharmaceutics aspects for the most commonly-used ocular administration routes (intravitreal, topical, systemic, and periocular), including information of the absorption, distribution, and elimination, as well as the benefits and limitations of each one. This article also encompasses different conventional and novel drug delivery systems designed and developed to improve drug pharmacokinetics intended for the posterior ocular segment treatment.

Göttingen Minipigs in Ocular Research

Since their development in the 1960s, Göttingen minipigs have become a popular nonrodent animal model in biomedical research, especially for ocular studies, because of their ease of handling, size, well-monitored genetics, and ocular anatomy that is similar to humans. The purpose of this mini-review is to introduce the reader to the various ways in which this animal model is currently being utilized in ocular research and to provide an overview of the diagnostic modalities that aid in this research. To date, the Göttingen minipig has been used for a variety of ocular research endeavors, including studies evaluating the safety and efficacy of ocular therapeutics, glaucoma etiopathogenesis and treatment, novel biomaterials, surgical procedures, and implantable materials/devices. In addition to histopathologic evaluation of enucleated globes, the majority of these studies make use of advanced in vivo diagnostic techniques, including electroretinography, optical coherence tomography, fundoscopic imaging, and fluorescein angiography.

Intravitreal, Subretinal, and Suprachoroidal Injections: Evolution of Microneedles for Drug Delivery

Even though the very thought of an injection into the eye may be frightening, an estimated 6 million intravitreal (IVT) injections were made in the USA during 2016. With the introduction of new therapeutic agents, this number is expected to increase. In addition, drug products that are injectable in ocular compartments other than the vitreous humor are expected to enter the back of the eye market in the not so distant future. Besides the IVT route, some of the most actively investigated routes of invasive administration to the eye include periocular, subretinal, and suprachoroidal (SC) routes. While clinical efficacy is the driving force behind new injectable drug product development for the eye, safety is also being improved with time. In the case of IVT injections, the procedural guidelines have evolved over the years to improve patient comfort and reduce injection-related injury and infection. Similar advances are anticipated for other routes of administration of injectable products to the eye. In addition to procedural improvements, the design of needles, particularly those with smaller diameters, length, and controlled bevel angles are expected to improve overall safety and acceptance of injected ophthalmic drug products. A key development in this area is the introduction of microneedles of a length less than a millimeter that can target the SC space. In the future, needles with smaller diameters and lengths, potentially approaching nanodimensions, are expected to revolutionize ophthalmic disease management.