Immunohistochemical localisation of intravitreally injected bevacizumab at the posterior pole of the primate eye: implication for the treatment of retinal vein occlusion

Six-month sustained delivery of anti-VEGF from in-situ forming hydrogel in the suprachoroidal space

Patients with wet age-related macular degeneration (AMD) require intravitreal injections of bevacizumab (Bev) or other drugs, often on a monthly basis, which is a burden on the healthcare system. Here, we developed an in-situ forming hydrogel comprised of Bev and hyaluronic acid (HA) crosslinked with poly(ethylene glycol) diacrylate for slow release of Bev after injection into the suprachoroidal space (SCS) of the eye using a microneedle. Liquid Bev formulations were cleared from SCS within 5 days, even when formulated with high viscosity, unless Bev was conjugated to a high molecular-weight HA (2.6 MDa), which delayed clearance until 1 month. To extend release to 6 months, we synthesized in-situ forming Bev-HA hydrogel initially as a low-viscosity mixture suitable for injection and flow in the SCS to cover a large area extending to the posterior pole of the eye where the macula is located in humans. Within 1 h after injection, Bev and HA were crosslinked, which retained Bev for slow release as the hydrogel biodegraded. In vivo studies in the rabbit eye reported Bev release for >6 months, depending on gel formulation and Bev assay. The in-situ forming Bev-HA hydrogel was well tolerated, as assessed by clinical exam, fundus imaging, histological analysis, and intraocular pressure measurement. We conclude that Bev released from an in-situ forming hydrogel may enable long-acting treatments of AMD and other posterior ocular indications.

Ocular Barriers and Their Influence on Gene Therapy Products Delivery

The eye is formed by tissues and cavities that contain liquids whose compositions are highly regulated to ensure their optical properties and their immune and metabolic functions. The integrity of the ocular barriers, composed of different elements that work in a coordinated fashion, is essential to maintain the ocular homeostasis. Specialized junctions between the cells of different tissues have specific features which guarantee sealing properties and selectively control the passage of drugs from the circulation or the outside into the tissues and within the different ocular compartments. Tissues structure also constitute selective obstacles and pathways for various molecules. Specific transporters control the passage of water, ions, and macromolecules, whilst efflux pumps reject and eliminate toxins, metabolites, or drugs. Ocular barriers, thus, limit the bioavailability of gene therapy products in ocular tissues and cells depending on the route chosen for their administration. On the other hand, ocular barriers allow a real local treatment, with limited systemic side-effects. Understanding the different barriers that limit the accessibility of different types of gene therapy products to the different target cells is a prerequisite for the development of efficient gene delivery systems. This review summarizes actual knowledge on the different ocular barriers that limit the penetration and distribution of gene therapy products using different routes of administration, and it provides a general overview of various methods used to bypass the ocular barriers.

RANDOMIZED CONTROLLED STUDY OF INTRAVITREAL BEVACIZUMAB 0.16 MG INJECTED ONE DAY BEFORE SURGERY FOR PROLIFERATIVE DIABETIC RETINOPATHY

PURPOSE

To investigate the usefulness of 0.16 mg/0.05 mL intravitreal bevacizumab (IVB) injection 1 day before vitrectomy for proliferative diabetic retinopathy.

METHODS

Sixty-two patients with proliferative diabetic retinopathy (66 eyes) with an indication for primary vitrectomy were randomized to IVB group (34 eyes) or sham control group (32 eyes). Intravitreal bevacizumab group received intravitreal injection of 0.16 mg/0.05 mL bevacizumab, and sham control group received sham injection 1 day before vitrectomy. Vitreous fluid was sampled before vitrectomy was started.

RESULTS

Frequency of reoperation due to recurrent vitreous hemorrhage within 4 weeks after surgery was significantly lower (P = 0.033) in IVB group (3.1%, 1/32) than in sham control group (20.6%, 7/34). The number of intraoperative endodiathermy spots (0.63 ± 1.0 vs. 1.3 ± 1.4, P = 0.025) and frequency of postoperative recurrent vitreous hemorrhage (3.1%, 1/32 vs. 23.5%, 8/34, P = 0.017) were significantly lower in IVB group than in sham control group. Vitreous vascular endothelial growth factor concentrations were 1315.3 ± 1153.4 pg/mL in sham control group and 25.0 ± 13.6 pg/mL in IVB group (P < 0.0001).

CONCLUSION

Intravitreal injection of 0.16 mg/0.05 mL bevacizumab 1 day before vitrectomy blocked vascular endothelial growth factor production in vitreous and significantly reduced the incidence of reoperation due to early postoperative recurrent vitreous hemorrhage.

Intravitreal Bevacizumab in Central Retinal Vein Occlusion: 18-month Results of a Prospective Clinical Trial

Purpose.

To evaluate the long-term visual results in central retinal vein occlusion (CRVO) following repeated intravitreal injections of bevacizumab (IVB).

Methods.

Thirteen patients (aged 34 to 79 years) with a duration of CRVO of 2 weeks to 6 months (mean 2.5 months) had a best-corrected visual acuity (BCVA) 0.05 to 0.4 (mean 0.13) as determined by Early Treatment Diabetic Retinopathy Study (ETDRS) chart. Clinical examination was carried out at baseline and every 6 to 8 weeks. Intravitreal bevacizumab (1.25 mg) was given every 6 weeks during the first 6 months, and after that at the discretion of the attending physician.

Results.

In total, 96 IVB (average 7.4/patient) were given: 50 IVB during the first 6 months, 28 from 6 to 12 months, and 18 from 12 to 18 months. Average BCVA had improved 15 ETDRS letters at 3 months, 24 letters at 6 months, 24 letters at 12 months, and 18 letters at 18 months (p<0.05). Eight patients (62%) had gained >15 ETDRS letters at 12 months, and 7 subjects (54%) >15 ETDRS letters at 18 months. Foveal thickness decreased from 596 μm at baseline to 294 μm at 18 months (p<0.05) and mean IOP from 15.2 mmHg to 15.8 mmHg. No serious adverse events occurred.

Conclusions.

Following repeated IVB, there was a significant gain of BCVA during the follow-up of 18 months. To maintain visual gain, regular ophthalmologic examinations and repeated injections seem to be necessary as long as the disease is active.

Macular infarction following intravitreal bevacizumab for treatment of central retinal vein occlusion

Bevacizumab, a monoclonal antibody against vascular endothelial growth factor (VEGF), is widely used for the treatment of macular edema associated with central retinal vein occlusion (CRVO). The authors present a series of three patients with CRVO who suffered apparent macular infarction within weeks of intravitreal administration of bevacizumab. Of the nearly 200 patients undergoing intravitreal injections of bevacizumab for this indication over a surveillance period of 3 years, this event occurred in three patients. This has not been described in the natural history of the disease and is associated with poor visual outcomes.

Ranibizumab for eyes previously treated with pegaptanib or bevacizumab without clinical response

BACKGROUND AND OBJECTIVE

To assess the safety and efficacy of ranibizumab in patients who had inadequate response to pegaptanib or bevacizumab.

PATIENTS AND METHODS

In this single-center study, 19 patients with subfoveal choroidal neovascularization secondary to age-related macular degeneration (AMD) previously treated with pegaptanib (n = 1), bevacizumab (n = 13), or both (n = 5) received 12 monthly ranibizumab injections (0.5 mg). Outcomes were measured from start of previous therapy (baseline) to start of ranibizumab treatment (day 0) through 12 months.

RESULTS

No drug- or injection-related adverse events and no serious adverse events were reported. At 6 and 12 months, 4 and 5 patients gained 3 or more lines of VA, respectively; 3 patients lost less than 3 lines of VA at 6 months, and 6 patients lost less than 3 lines at 12 months. At 6 and 12 months, VA increased by a mean (± standard error of the mean) of 2.06 ± 1.23 and 1.17 ± 0.62 lines, respectively. Central retinal thickness decreased by a mean of 62.65 ± 22.46 and 62.16 ± 29.20 μm at months 6 and 12, respectively. When stratified by pigment epithelial detachment (PED) status, patients without PED had better visual and anatomical outcomes than patients with PED.

CONCLUSION

Ranibizumab has favorable safety and efficacy profiles for patients with AMD without previous response to pegaptanib or bevacizumab.

Injection site and pharmacokinetics after intravitreal injection of immunoglobulin G

PURPOSE

The aim of this study was to investigate whether the pharmacokinetics differ after immunoglobulin G (IgG) intravitreal injections are done in the different sites of the vitreous cavity of rabbit eyes.

METHODS

To examine the pharmacokinetics in the vitreous and the retina/choroid, fluorescein isothiocyanate-labeled IgG (5  μg/50  μL) was injected from the superior pars plana into the vitreous cavity of rabbit eyes. An original intravitreal injection guide was used to fix the tip of the injection needle, with the tip fixed in either the superior-anterior vitreous (superior group) or in the posterior vitreous (posterior group). At 1  h, 1, 4, and 7 days after injection, the eyes were enucleated and frozen. The vitreous was cut into superior, inferior, and posterior vitreous sections, whereas the retina/choroid was cut into superior, inferior, and posterior retina/choroid sections. The IgG concentrations in the vitreous and the retina/choroid sections were then determined.

RESULTS

In the posterior vitreous, the IgG concentration in the posterior group was significantly higher than that in the superior group at 1  h after injection (P < 0.05). However, 1 day after injection, no significant differences were noted between the 2 groups. At 4 days after injection, the drug was diffusely spread in both groups. In the posterior retina/choroid, the IgG concentration was essentially the same regardless of the injection site or the amount of time after injection. The IgG concentration in the superior retina/choroid was significantly higher in the superior group than in the posterior group at 1  h and 1 day after injection (P < 0.05). There were no differences noted between the 2 groups for the IgG concentrations in the 3 sections at 4 and 7 days after injection.

CONCLUSIONS

Intravitreally injected IgG remains in the area of the injection, with more than 1 day required for it to spread diffusely within the vitreous. In the posterior retina/choroid, results suggested that the concentration of IgG may be equal regardless of the injection site. In the superior retina/choroid area that was near the site of the injection, the concentration of drug tended to be higher.

Visual improvement in central retinal vein occlusion (CRVO) following intravitreal injections of bevacizumab (Avastin(®) )

PURPOSE

To perform a prospective study on central retinal vein occlusion (CRVO) to evaluate whether visual acuity can be improved and macular oedema reduced in response to intravitreal injections of bevacizumab.

METHODS

The case material comprised 13 patients (aged 34-79 years), duration of CRVO was 2 weeks to 6 months, baseline ETDRS visual acuity 0.06-0.4 (mean Snellen 0.13, derived from logMAR value) and intraocular pressure (IOP) 12-20 (mean 15.2) mmHg. Clinical examination, including optical coherence tomography (OCT), was carried out at baseline and every 6 weeks, digital fluorescein angiography at baseline, at 3 months and 6 months. Intravitreal injections of bevacizumab (1.25 mg) were given under microscopic control at baseline and every 6 weeks during the 6-month follow-up.

RESULTS

Following one intravitreal injection of bevacizumab, average visual acuity improved by 13 ETDRS letters at 1 month (p < 0.05) and in response to 4 injections by 24 letters (logMAR 0.48) at 6 months (p < 0.05). Foveal thickness as measured by OCT decreased from 596 μm at baseline to 288 μm at 6 months (p < 0.05) concomitant with resorption of intra- and subretinal fluid. IOP ranged from 10 to 24 (17.3) mmHg at 6-month follow-up. No adverse events occurred.

CONCLUSIONS

  In response to four intravitreal injections of bevacizumab during 6 months, a substantial improvement in visual acuity and reduction in central retinal thickness were achieved. A randomized clinical trial is warranted to further evaluate the efficacy and safety of this treatment modality.

Histopathology of neovascular tissue from eyes with proliferative diabetic retinopathy after intravitreal bevacizumab injection

PURPOSE

To examine the histopathologic effect of a single intravitreal injection of bevacizumab on newly formed vessels in eyes with proliferative diabetic retinopathy (PDR).

DESIGN

Interventional case series and laboratory investigation.

METHODS

Two days after intravitreal injection of bevacizumab (1.25 mg/eye), pars plana vitrectomy or trabeculectomy was performed for the treatment of PDR or neovascular glaucoma (NVG) associated with PDR. Ten surgically removed preretinal proliferative tissues and 6 deep scleral flaps containing trabecular meshwork were fixed in 2% glutaraldehyde or 4% paraformaldehyde and were subjected to transmission electron microscopic analysis, immunohistochemical analysis, and terminal deoxyuridiine triphosphate (dUTP) nick-end labeling staining. Two surgically removed preretinal proliferative tissues and 2 deep scleral flaps from patients with PDR and NVG, but without preoperative intravitreal injection of bevacizumab (IVB), served as controls.

RESULTS

In control tissues, vascular endothelial cells possessed many fenestrations and were accompanied by pericytes. Apoptotic vascular endothelial cells frequently were observed in tissue after intravitreal injection of bevacizumab, whereas they were not observed in control tissues. Additionally, no apparent fenestration was observed in newly formed vessels from either proliferative tissue or trabecular meshwork after intravitreal injection of bevacizumab. In both PDR and NVG tissues after intravitreal injection of bevacizumab, overexpression of smooth muscle actin was observed in newly formed vessels, suggesting that the treatment may have increased pericytes on the vasculature as compared with control tissue.

CONCLUSIONS

Intravitreal injection of bevacizumab may induce changes in immature, newly formed vessels of PDR or NVG tissue, leading to endothelial apoptosis with vascular regression, while inducing normalization of premature vessels by increasing pericyte coverage and reducing vessel fenestration.

Protein delivery for retinal diseases: from basic considerations to clinical applications

Because the eye is protected by ocular barriers but is also easily accessible, direct intravitreous injections of therapeutic proteins allow for specific and targeted treatment of retinal diseases. Low doses of proteins are required in this confined environment and a long time of residency in the vitreous is expected, making the eye the ideal organ for local proteic therapies. Monthly intravitreous injection of Ranibizumab, an anti-VEGF Fab has become the standard of care for patients presenting wet AMD. It has brought the proof of concept that administering proteins into the physiologically low proteic concentration vitreous can be performed safely. Other antibodies, Fab, peptides and growth factors have been shown to exert beneficial effects on animal models when administered within the therapeutic and safe window. To extend the use of such biomolecules in the ophthalmology practice, optimization of treatment regimens and efficacy is required. Basic knowledge remains to be increased on how different proteins/peptides penetrate into the eye and the ocular tissues, distribute in the vitreous, penetrate into the retinal layers and/or cells, are eliminated from the eye or metabolized. This should serve as a basis for designing novel drug delivery systems. The later should be non-or minimally invasive and should allow for a controlled, scalable and sustained release of the therapeutic proteins in the ocular media. This paper reviews the actual knowledge regarding protein delivery for eye diseases and describes novel non-viral gene therapy technologies particularly adapted for this purpose.

Neurotrophic effect of a novel TrkB agonist on retinal ganglion cells

PURPOSE

Retinal ganglion cells (RGCs) die in glaucoma and virtually all optic neuropathies. Recently, novel tropomyosin-related kinase B (TrkB) monoclonal antibodies have been shown to activate TrkB receptors and exert neuroprotective and neurotrophic effects. In the present study, the authors examined the ability of one of them, 29D7, to elicit RGC survival and neurite growth both in culture and in vivo.

METHODS

RGCs from postnatal day (P)3 to P4 Sprague-Dawley rats were isolated by sequential immunopanning using a monoclonal antibody to Thy1. RGCs were cultured in serum-free defined medium in 96-well plates. RGC viability was assessed after 1 to 3 days by MTT assay. Activation of TrkB and downstream signaling molecules was confirmed by Western blot analysis. Intravitreal injections of 29D7 were performed after optic nerve axotomy, and subsequent RGC survival was quantified using beta-III tubulin immunostaining. Regeneration was assessed using retrograde fluorogold tracing in an optic nerve-peripheral nerve graft model.

RESULTS

Similar to brain-derived neurotrophic factor (BDNF), the 29D7 antibody strongly promoted RGC survival and neurite growth in vitro compared with medium alone or control IgG. Forskolin, which weakly supported RGC survival on its own, potentiated the effect of 29D7. Intravitreal injection of 29D7 enhanced RGC survival but not regeneration in vivo 2 weeks after optic nerve injury.

CONCLUSIONS

Together, these findings demonstrate the potential for antibody-mediated TrkB agonism as a potential therapeutic approach to enhance RGC survival after optic nerve injury. Further studies are needed to elucidate the mechanistic differences between this TrkB agonist and BDNF.