Potential penetration of topical ranibizumab (Lucentis) in the rabbit eye

Topical Solution for Retinal Delivery: Bevacizumab and Ranibizumab Eye Drops in Anti-Aggregation Formula (AAF) in Rabbits

PURPOSE

Wet age-related macular degeneration (AMD) is a blinding retinal disease. Monthly intravitreal anti-VEGF antibody injections of bevacizumab (off-label) and ranibizumab (FDA approved) are the standard of care. Antibody aggregation may interfere with ocular absorption/distribution. This study assessed topical delivery of dilute antibodies to the posterior segment of rabbit eyes using a novel anti-aggregation formula (AAF).

METHODS

Bevacizumab, or biosimilar ranibizumab was diluted to 5 mg/ml in AAF. All rabbits were dosed twice daily. Substudy 1 rabbits (bevacizumab, 100 µl eye drops): Group 1 (bevacizumab/AAF, n = 6); Group 2 (bevacizumab/PBS, n = 7) and Vehicle control (AAF, n = 1). Substudy 2 rabbits (ranibizumab biosimilar/AAF, 50 µl eye drops): (ranibizumab biosimilar/AAF, n = 8). At 14.5 days, serum was drawn from rabbits. Aqueous, vitreous and retina samples were recovered from eyes and placed into AAF aliquots. Tissue analyzed using AAF as diluent.

RESULTS

Bevacizumab in AAF permeated/accumulated in rabbit aqueous, vitreous and retina 10 times more, than when diluted in PBS. AAF/0.1% hyaluronic acid eye drops, dosed twice daily, provided mean tissue concentrations (ng/g) in retina (29.50), aqueous (12.34), vitreous (3.46), and serum (0.28 ng/ml). Additionally, the highest concentration (ng/g) of ranibizumab biosimilar was present in the retina (18.0), followed by aqueous (7.82) and vitreous (1.47). Serum concentration was negligible (< 0.04 ng/ml). No irritation was observed throughout the studies.

CONCLUSIONS

Bevacizumab and ranibizumab, in an AAF diluent eye drop, can be delivered to the retina, by the twice daily dosing of a low concentration mAb formulation. This may prove to be an adjunct to intravitreal injections.

Topical Ophthalmic Liposomes Dual-Modified with Penetratin and Hyaluronic Acid for the Noninvasive Treatment of Neovascular Age-Related Macular Degeneration

Introduction

Since intrinsic ocular barrier limits the intraocular penetration of therapeutic protein through eye drops, repeated intravitreal injections of anti-vascular endothelial growth factor (anti-VEGF) agents are the standard therapy for neovascular age-related macular degeneration (nAMD), which are highly invasive and may cause particular ocular complications, leading to poor patient compliance.

Methods

Using Penetratin (Pen) as the ocular penetration enhancer and hyaluronic acid (HA) as the retina-targeting ligand, a dual-modified ophthalmic liposome (Penetratin hyaluronic acid-liposome/Conbercept, PenHA-Lip/Conb) eye drop was designed to non-invasively penetrate the ocular barrier and deliver anti-VEGF therapeutic agents to the targeted intraocular tissue.

Results

PenHA-Lip effectively penetrates the ocular barrier and targets the retinal pigment epithelium via corneal and non-corneal pathways. After a single topical administration of conbercept-loaded PenHA-Lip (PenHA-Lip/Conb), the intraocular concentration of conbercept peaked at 18.74 ± 1.09 ng/mL at 4 h, which is 11.55-fold higher than unmodified conbercept. In a laser-induced choroidal neovascularization (CNV) mouse model, PenHA-Lip/Conb eye drops three times daily for seven days inhibited CNV formation and progression without any significant tissue toxicity and achieved an equivalent effect to a single intravitreal conbercept injection.

Conclusion

PenHA-Lip efficiently and safely delivered conbercept to the posterior eye segment and may be a promising noninvasive therapeutic option for nAMD.

Clinical and Histopathological Effects of Intracameral Ranibizumab in Experimental Trabeculectomy

Post-surgical scarring is a known cause of trabeculectomy failure. The aim of this study was to investigate the effectiveness of ranibizumab as an adjuvant anti-scarring agent in experimental trabeculectomy. Forty New Zealand white rabbits were randomised into four eye treatment groups: groups A (control), B (ranibizumab 0.5 mg/mL), C (mitomycin C [MMC] 0.4 mg/mL), and D (ranibizumab 0.5 mg/mL and MMC 0.4 mg/mL). Modified trabeculectomy was performed. Clinical parameters were assessed on post-operative days 1, 2, 3, 7, 14, and 21. Twenty rabbits were euthanised on day 7, and the other twenty were euthanised on day 21. Eye tissue samples were obtained from the rabbits and stained with haematoxylin and eosin (H&E). All treatment groups showed a significant difference in IOP reduction compared with group A (p < 0.05). Groups C and D showed a significant difference in bleb status on days 7 (p = 0.001) and 21 (p = 0.002) relative to group A. H&E staining showed significantly low fibrotic activity (p < 0.001) in group C on both days and inflammatory cell grade in group B on day 7 (p < 0.001). The grade for new vessel formation was significantly low in groups B and D on day 7 (p < 0.001) and in group D on day 21 (p = 0.007). Ranibizumab plays a role in reducing scarring, and a single application of the ranibizumab-MMC combination showed a moderate wound-modulating effect in the early post-operative phase.

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

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

Potential of subconjunctival aflibercept in treating choroidal neovascularization

The study aimed to evaluate the intraocular pharmacokinetics and efficacy of aflibercept after subconjunctival injection in animal models for treating choroidal neovascularization (CNV) associated with Age-Related Macular Degeneration (AMD). New Zealand albino rabbits received aflibercept (2000 μg/50 μl) in one eye, and the other eye was used as control. At 7, 14, 21 and 28 days, the animals were sacrificed to dissect the ocular tissues, and serum was collected at 1hr, 3 h, 1, 7, 14, 21 and 28 days. The concentration of aflibercept in various ocular tissues and serum were measured using the immunoassay technique. The concentration maximum (C_max) at the Retinal Pigment Epithelium (RPE)-choroid complex and retina in treated eyes was 261.55 and 33.83 ng/gm, respectively. The area under the curve (AUC_0-last) for RPE-Choroid and retina were 2094.02 and 290.33 days. ng/gm respectively. The time maximum (T_max) for the ocular tissues was reached on day 7. In the vitreous humour, a lower level of aflibercept was retrieved. The C_max (1766.84 ng/mL) in the serum was reached on day 1, followed by a decline in the concentration till the end of the study period. In treated eyes, the levels of aflibercept in most of the ocular tissues were maintained for at least 21 days above the invitro IC₅₀ concentration. The results of the efficacy study show that subconjunctival aflibercept could reach the therapeutic target to inhibit CNV. The subconjunctival aflibercept could be a less invasive route for treating CNV with AMD.

Intraocular Pharmacokinetics of 10-fold Intravitreal Ranibizumab Injection Dose in Rabbits

Purpose

To investigate intraocular pharmacokinetics of 10-fold dose of intravitreally injected ranibizumab compared with the conventional dose in an experimental model.

Methods

Ranibizumab 30 µL at 10 mg/mL (conventional) and 100 mg/mL (10-fold) doses was injected separately into each eye of 28 rabbits. Ranibizumab concentrations in the aqueous humor, vitreous, and retina were estimated at each time period after injection, using enzyme-linked immunosorbent assay. The pharmacokinetic properties of ranibizumab were determined using a one-compartment model in all three ocular tissues. The time–concentration profile and predictive trends were plotted to determine drug efficacy in the retina.

Results

Maximum concentrations after conventional and 10-fold dosing were observed in the retina at 1 and 4 days after injection, respectively. The half-life of ranibizumab after conventional and 10-fold dosing did not differ in the anterior chamber and vitreous, whereas the half-life was prolonged approximately twice with the 10-fold dose in the retina (36.74 h vs. 76.85 h) and serum (91.93 h vs. 179.01 h). Similarly, the estimated time for ranibizumab concentration in the retina over 27 ng/mL (minimum effective concentration of ranibizumab) was prolonged approximately twice with the 10-fold dose (1315 h [55 days] vs. 2393 h [100 days]). No adverse effects were observed in either group.

Conclusions

The retinal half-life and concentration of ranibizumab in rabbit eyes were increased approximately twice after a 10-fold dose compared with the conventional dose. This finding indicates a possibility to lengthen the injection interval to improve the efficacy of ranibizumab in human eyes.

Translational Relevance

Our results highlight the potential for clinical application of a high-dose (10-fold) of anti-VEGF agents to prolong the intravitreal injection intervals, simultaneously improving the drug efficacy.

Safety Assessment of Formulation Vehicles Following Intravitreal Administration in Rabbits

PURPOSE

Evaluate 21 formulation vehicles administered to rabbits after intravitreal injection for tolerability and safety.

METHODS

Forty-two Dutch Belted rabbits were anesthetized, and the eyes received a single intravitreal injection of the excipient formulation. Clinical signs and ocular irritation responses were recorded twice daily for 7 days and microscopic evaluation of the eyes, optic nerve, and eyelids was completed at 1-week post treatment.

RESULTS

Saline (≥ 300 mOsm and ≤ 592 mOsm at pH 7.0 or 300 mOsm at pH 8.0) and 10 formulation excipients; (10% w/v PEG 3350 at pH 7.4, 1% polysorbate 21 at pH 7.4, PVA at pH 7.0, 0.2% polysorbate 80 at pH 7.2, 0.2% Pluronic F108® at pH 7.3, 2%, 100 mM sodium sulfate at pH 3.2, 2 mM sodium glycocholate at pH 7.4, and 275 mM D-mannitol pH 7.0 in sterile water, and 100 mM sodium phosphate in combination with 0.9% NaCl 300 mOsm and 0.01% or 0.05% polysorbate 80 at pH 7.4) considered as formulation vehicles for intravitreal injectables, were well-tolerated in rabbits. Clinical signs were transient and microscopic changes were not observed.

CONCLUSIONS

Of the 21 formulation vehicles evaluated, 10 formulation vehicles were well-tolerated in rabbits and feasible candidates for future investigations.

Intraocular Penetration of a vNAR: In Vivo and In Vitro VEGF165 Neutralization

Variable new antigen receptor domain (vNAR) antibodies are novel, naturally occurring antibodies that can be isolated from naïve, immune or synthetic shark libraries. These molecules are very interesting to the biotechnology and pharmaceutical industries because of their unique characteristics related to size and tissue penetrability. There have been some approved anti-angiogenic therapies for ophthalmic conditions, not related to vNAR. This includes biologics and chimeric proteins that neutralize vascular endothelial growth factor (VEGF)₁₆₅, which are injected intravitreal, causing discomfort and increasing the possibility of infection. In this paper, we present a vNAR antibody against human recombinant VEGF₁₆₅ (rhVEGF₁₆₅) that was isolated from an immunized Heterodontus francisci shark. A vNAR called V13, neutralizes VEGF₁₆₅ cytokine starting at 75 μg/mL in an in vitro assay based on co-culture of normal human dermal fibroblasts (NHDFs) and green fluorescence protein (GFP)-labeled human umbilical vein endothelial cells (HUVECs) cells. In the oxygen-induced retinopathy model in C57BL/6:Hsd mice, we demonstrate an endothelial cell count decrease. Further, we demonstrate the intraocular penetration after topical administration of 0.1 μg/mL of vNAR V13 by its detection in aqueous humor in New Zealand rabbits with healthy eyes after 3 h of application. These findings demonstrate the potential of topical application of vNAR V13 as a possible new drug candidate for vascular eye diseases.

Principles of pharmacology in the eye

The eye is a highly specialized organ that is subject to a huge range of pathology. Both local and systemic disease may affect different anatomical regions of the eye. The least invasive routes for ocular drug administration are topical (e.g. eye drops) and systemic (e.g. tablets) formulations. Barriers that subserve as protection against pathogen entry also restrict drug permeation. Topically administered drugs often display limited bioavailability due to many physical and biochemical barriers including the pre-corneal tear film, the structure and biophysiological properties of the cornea, the limited volume that can be accommodated by the cul-de-sac, the lacrimal drainage system and reflex tearing. The tissue layers of the cornea and conjunctiva are further key factors that act to restrict drug delivery. Using carriers that enhance viscosity or bind to the ocular surface increases bioavailability. Matching the pH and polarity of drug molecules to the tissue layers allows greater penetration. Drug delivery to the posterior segment is a greater challenge and, currently, the standard route is via intravitreal injection, notwithstanding the risks of endophthalmitis and retinal detachment with frequent injections. Intraocular implants that allow sustained drug release are at different stages of development. Novel exciting therapeutic approaches include methods for promoting transscleral delivery, sustained release devices, nanotechnology and gene therapy.

Recent perspectives on the delivery of biologics to back of the eye

INTRODUCTION

Biologics are generally macromolecules, large in size with poor stability in biological environments. Delivery of biologics to tissues at the back of the eye remains a challenge. To overcome these challenges and treat posterior ocular diseases, several novel approaches have been developed. Nanotechnology-based delivery systems, like drug encapsulation technology, macromolecule implants and gene delivery are under investigation. We provide an overview of emerging technologies for biologics delivery to back of the eye tissues. Moreover, new biologic drugs currently in clinical trials for ocular neovascular diseases have been discussed. Areas covered: Anatomy of the eye, posterior segment disease and diagnosis, barriers to biologic delivery, ocular pharmacokinetic, novel biologic delivery system Expert opinion: Anti-VEGF therapy represents a significant advance in developing biologics for the treatment of ocular neovascular diseases. Various strategies for biologic delivery to posterior ocular tissues are under development with some in early or late stages of clinical trials. Despite significant progress in the delivery of biologics, there is unmet need to develop sustained delivery of biologics with nearly zero-order release kinetics to the back of the eye tissues. In addition, elevated intraocular pressure associated with frequent intravitreal injections of macromolecules is another concern that needs to be addressed.

Retinal Gene Therapy: Surgical Vector Delivery in the Translation to Clinical Trials

An exceptionally high number of monogenic disorders lead to incurable blindness, making them targets for the development of gene-therapy. In order to successfully apply therapeutic vector systems in vivo, the heterogeneity of the disease phenotype needs to be considered. This necessitates tailored approaches such as subretinal or intravitreal injections with the aim to maximize transduction of target cell populations, while minimizing off-target effects and surgical complications. Strategic decisions on parameters of the application are crucial to obtain the best treatment outcomes and patient safety. While most of the current retinal gene therapy trials utilize a subretinal approach, a deeper understanding of the numerous factors and considerations in choosing one delivery approach over the other for various ocular pathologies could lead to an improved safety and treatment efficacy. In this review we survey different vector injection techniques and parameters applied in recent retinal (pre-)clinical trials. We explore the advantages and shortcomings of each delivery strategy in the setting of different underlying ocular pathologies and other relevant factors. We highlight the potential benefits for patient safety and efficacy in applying those considerations in the decision making process.

Drug delivery to the eye: what benefits do nanocarriers offer?

Ocular drug delivery has seen several advances in the past few decades, with respect to new drugs, improved formulations, targeted delivery, as well as exploration of new routes of drug administration. New materials have been explored for encasing existing drugs, which can enhance treatment by increasing bioavailability, decreasing toxicity, providing better tissue adherence, targeted delivery as well as increased duration of action. The challenges and requirements are different for the anterior and posterior ocular segments. This review summarizes the recent advances in sustained ocular therapy, both to the anterior and posterior segments, which have been made possible, thanks to nanotechnology. We also discuss the distribution and fate of these nanocarriers themselves, postadministration, as well as clearance from ocular tissues.

Efficacy of Antibody Delivery to the Retina and Optic Nerve by Topical Administration

PURPOSE

The purpose of this study was to determine whether nonspecific and ICAM-1-specific IgG1 antibodies can accumulate in the rat retina following topical application, and to develop a model system to show that antibodies that reach the posterior segment retain their pharmacological properties.

METHODS

Eye drops containing mouse IgG1 or anti-ICAM-1 and the permeation enhancer saponin were topically applied to the eyes of Lewis rats. Concentrations were determined in the retina and optic nerve up to 30 min later using ELISA assays. We also developed an in vitro model to assess the pharmacologic activity of topically delivered antibodies in the retina based on the requirement of human umbilical vein endothelial cells (HUVECs) for vascular endothelial growth factor (VEGF) for growth. Rat eyes were treated with anti-VEGF antibody in the same manner as above; their retinas, harvested shortly thereafter, were added to HUVECs cultured in VEGF-containing media. The effect of these retinal homogenates on HUVEC proliferation was then assessed.

RESULTS

Significant concentrations of IgG1 were detected in the optic nerve (P < 0.001) and retina (P < 0.0001) following topical application. Anti-ICAM-1 antibody also accumulated in the retina after topical application, though levels were less than those seen with IgG1 probably owing to a lower starting concentration. Retinal homogenates from eyes treated with anti-VEGF antibody significantly suppressed HUVEC proliferation (P < 0.0001).

CONCLUSIONS

Our data support the contention that topically applied antibodies can accumulate in the posterior segment, and suggest they retain their pharmacological properties.

A Comparative Study of Topical Mitomycin C, Cyclosporine, and Bevacizumab after Primary Pterygium Surgery

PURPOSE

To compare the recurrence rates and complications associated with instillation of topical mitomycin C, cyclosporine, and bevacizumab after primary pterygium surgery.

METHODS

Between July 2013 and June 2014, we performed surgery using the bare sclera method on 132 eyes (132 patients) with primary pterygium. We randomly selected 33 eyes (33 patients) and treated them with artificial tears four times a day for three months, 29 eyes (29 patients) were treated with topical 0.02% mitomycin C four times a day for five days, 34 eyes (34 patients) were treated with topical 0.05% cyclosporine four times a day for three months, and 36 eyes (36 patients) were treated with topical 2.5% bevacizumab four times a day for three months after surgery. We prospectively determined the recurrence rates of pterygium and complications at the six-month follow-up examination.

RESULTS

At six months after surgery, the recurrence rates in each group were as follows: 45.5% (15 eyes) in the control group, 10.3% (three eyes) in the mitomycin C group, 20.6% (seven eyes) in the cyclosporine group, and 41.7% (15 eyes) in the bevacizumab group (p = 0.004). No serious complications, except subconjunctival hemorrhages, were observed in any group.

CONCLUSIONS

Groups receiving topical 0.02% mitomycin C and 0.05% cyclosporine after surgery showed lower recurrence rates than the control group; however, no difference in recurrence rate was observed between the control group and the group receiving topical 2.5% bevacizumab after surgery.

A comparative study of different concentrations of topical bevacizumab on the recurrence rate of excised primary pterygium: a short-term follow-up study

The present study was undertaken to compare the pterygium recurrence rates after treatment with two different concentrations of topical bevacizumab in those who had undergone a primary pterygium excision. The 90 patients who underwent pterygium excision were enrolled in this prospective, placebo-controlled double-blinded interventional case series. The participants were randomly categorized into 3 groups each consisting of 30 subjects. 24 h after surgery, Group II and Group III received a total of 5 and 10 mg/mL dose of topical bevacizumab, respectively; whereas patients in Group I were administered only a placebo starting a day after surgery. Participants were instructed to instill their topical medicines 4 times a day for 1 week. The patients were examined for pterygium recurrence and complications at postoperative 1, 7, and 14 days as well as each month during the following year. Pterygia recurred in 14 patients (46.7 %) in Group I and in 4 patients (13.3 %) in Group II. No recurrence was observed in Group III during the follow-up period. The Kaplan-Meier survival analysis disclosed a significantly better outcome for those who had been treated with 10 mg/mL concentrations of bevacizumab (Mantel-Cox log rank analysis, P < 0.001). The mean recurrence time was not significantly different between Group I and Group II. No ocular or systemic complication developed till the end of follow-up. Thus, 10 mg/mL concentration of topical bevacizumab was more efficacious than 5 mg/mL dose in preventing pterygium recurrence.