Is monthly retreatment with intravitreal bevacizumab (Avastin) necessary in neovascular age-related macular degeneration?

Affinity-controlled release of rod-derived cone viability factor enhances cone photoreceptor survival

Retinitis pigmentosa (RP) is a group of genetic diseases that results in rod photoreceptor cell degeneration, which subsequently leads to cone photoreceptor cell death, impaired vision and eventual blindness. Rod-derived cone viability factor (RdCVF) is a protein which has two isoforms: a short form (RdCVF) and a long form (RdCVFL) which act on cone photoreceptors in the retina. RdCVFL protects photoreceptors by reducing hyperoxia in the retina; however, sustained delivery of RdCVFL remains challenging. We developed an affinity-controlled release strategy for RdCVFL. An injectable physical blend of hyaluronan and methylcellulose (HAMC) was covalently modified with a peptide binding partner of the Src homology 3 (SH3) domain. This domain was expressed as a fusion protein with RdCVFL, thereby enabling its controlled release from HAMC-binding peptide. Sustained release of RdCVFL was demonstrated for the first time as RdCVFL-SH3 from HAMC-binding peptide for 7 d in vitro. To assess bioactivity, chick retinal dissociates were harvested and treated with the affinity-released recombinant protein from the HAMC-binding peptide vehicle. After 6 d in culture, cone cell viability was greater when cultured with released RdCVFL-SH3 relative to controls. We utilized computational fluid dynamics to model release of RdCVFL-SH3 from our delivery vehicle in the vitreous of the human eye. We demonstrate that our delivery vehicle can prolong the bioavailability of RdCVFL-SH3 in the retina, potentially enhancing its therapeutic effects. Our affinity-based system constitutes a versatile delivery platform for ultimate intraocular injection in the treatment of retinal degenerative diseases. STATEMENT OF SIGNIFICANCE: Retinitis pigmentosa (RP) is the leading cause of inherited blindness in the world. Rod-derived cone viability factor (RdCVF), a novel protein paracrine factor, is effective in preclinical models of RP. To extend its therapeutic effects, we developed an affinity-controlled release strategy for the long form of RdCVF, RdCVFL. We expressed RdCVFL as a fusion protein with an Src homology 3 domain (SH3). We then utilized a hydrogel composed of hyaluronan and methylcellulose (HAMC) and modified it with SH3 binding peptides to investigate its release in vitro. Furthermore, we designed a mathematical model of the human eye to investigate delivery of the protein from the delivery vehicle. This work paves the way for future investigation of controlled release RdCVF.

6-weekly bevacizumab versus 4-weekly ranibizumab for neovascular age-related macular degeneration: a 2-year outcome

AIM

To compare visual acuity and central macular thickness (CMT) changes in neovascular age related macular degeneration patients treated with either 6 weekly bevacizumab regimen or 4 weekly ranibizumab on an as required basis.

METHODS

Patients made an informed choice between bevacizumab 1.25 mg or ranibizumab 0.5 mg. The selected treatment was administered in the first 3 visits. Bevacizumab patients were followed-up 6 weekly and ranibizumab 4 weekly. Retreatment criteria was based on the reduction of >5 letters in the best-corrected visual acuity (BCVA), the presence of retinal fluid on optical coherence tomography (OCT) or new retinal haemorrhage.

RESULTS

Visual acuity at 2y bevacizumab patients gained 7.0 letters and ranibizumab 9.2 (P=0.31, 95% CI -6.4 to 2.0). At 2y 86% of bevacizumab and 94% ranibizumab patients had not lost 15 letters or more (P=0.13). Mean CMT decreased at 2y bevacizumab by 146 µm, ranibizumab 160 µm (P=0.72). Mean number of injections was at 2y bevacizumzb 11.9, ranibizumab 10.3 (P=0.023).

CONCLUSION

Bevacizumab 6 weekly on an as required basis was not demonstrably non-inferior to ranibizumab 4 weekly pro re nata (prn) in terms of BCVA and change in CMT. In the bevacizumab group, one more injection was required in the second year compared to the ranibizumab group.

Comparative safety profiles of intravitreal bevacizumab, ranibizumab and pegaptanib: the analysis of the WHO database of adverse drug reactions

PURPOSE

The purpose of this study is to conduct a comparative analysis of the suspected adverse drug reactions (ADRs) associated with intravitreal bevacizumab, ranibizumab and pegaptanib in the WHO database in order to have a real-life information on these drugs, which now is only based on data coming from clinical trials.

METHODS

ADR reports for intravitreal use of bevacizumab, ranibizumab and pegaptanib from January 2002 to December 2012 were selected from the WHO-VigiBase. Reporting odds ratio (ROR) with confidence interval of 95 % and p value was calculated. The analysis was performed for drug-reaction pairs. The Medical Dictionary for Regulatory Activities (MedDRA) terminology for ADRs was used.

RESULTS

The analysis was performed on 3180 reports corresponding to 7753 drug-reaction pairs. Significant RORs for endophthalmitis and uveitis (1.90, 95 % confidence interval (CI) 1.48-2.43, and 10.62, 6.62-17.05, respectively) were retrieved for bevacizumab, and cerebrovascular accident and myocardial infarction produced significant ROR (1.54, 1.14-2.10 and 1.73, 1.18-2.53, respectively) for ranibizumab. Pegaptanib was significantly associated with visual impairment (1.98, 1.12-3.5, p = 0.02), nausea (3.29, 1.57-6.86, p < 0.001), vomiting (2.91, 1.2-7.07, p = 0.01) and drug hypersensitivity (8.75, 3.1-24.66, p < 0.001).

CONCLUSIONS

Our data showed an elevated disproportionality for cardiovascular ADRs in patients treated with ranibizumab and for infective ocular reactions in those treated with bevacizumab. No relevant safety issues were identified for pegaptanib. These findings suggest bevacizumab as a suitable choice for AMD therapy due to its effectiveness similar to that of ranibizumab, its favourable safety profile and for its lower cost.

Intravitreal bevacizumab as a primary treatment for idiopathic choroidal neovascularization

PURPOSE

To report long-term outcomes of the use of intravitreal bevacizumab in subjects with idiopathic choroidal neovascularization (ICNV).

MATERIALS AND METHODS

Six consecutive subjects with ICNV were included in this prospective study. All subjects received 1.25 mg intravitreal bevacizumab at diagnosis. A decrease in best corrected visual acuity (BCVA), presence of increased retinal edema or hemorrhage, increased retinal thickness on optical coherence tomography (OCT) or increased leakage documented by fluorescein angiography prompted further injections of bevacizumab.

RESULTS

The study cohort was comprised of 3 males and 3 females with a mean age of 31.17 years. Mean follow-up was 13.8 months (range, 8 months to 20 months). Following intravitreal bevacizumab injection, vision improved in 3 subjects, remained stable in 3 subjects and no patient lost visual acuity. The mean BCVA improved to logMAR 0.20 at final follow-up from baseline at 0.950 logMAR (P=0.031). The mean central macular thickness and central foveal thickness at the last postoperative visits were reduced from pre-treatment levels of 374.33 ± 146.52 and 347.16 ± 213.97 to 251.20±35.36 and 215.33 ± 43.94 μm, respectively. (P = 0.99 and P = 0.16, respectively). Four subjects required repeat treatments. The total number of repeat treatments was 4. Two subjects required no repeat injections, 3 subjects had 1 retreatment and one subject required 2 additional treatments. The injections were well tolerated by all the subjects, with no ocular or systemic adverse events.

CONCLUSION

Intravitreal injection of 1.25 mg bevacizumab in patients with ICNV is effective in improving and stabilizing vision. Additional studies, particularly determination of optimal protocol for timing of re-injection are required to assess long-term effects.

Detection of heat shock protein 70 in choroidal neovascular membranes secondary to age related macular degeneration

Background

Heat shock proteins are acute phase proteins that are upregulated in inflammation or following thermal stress. We analyzed the presence of the heat shock protein 70 (Hsp 70) in choroidal neovascular (CNV) membranes secondary to AMD after treatment with verteporphin photodynamic therapy (PDT) or transpupillary thermo therapy (TTT) to determine whether treatment correlated with the presence of Hsp70.

Results

CNV membranes were removed by pars plana vitrectomy (ppV) and subretinal extraction. The membranes were analysed by light microscopy and the presence of Hsp 70 was examined using histochemistry. HeLa Cells served as controls.

Of the 14 membranes analysed 11 were Hsp70 positive and 3 negative. In the no pre-treatment group of 8 membranes 6 were Hsp70 positive and 2 negative; in the PTD group all 4 membranes were positive and in the TTT group 1 membrane was positive and 1 membrane was negative for Hsp70.

Conclusion

Hsp70 is present in the most CNV membranes secondary to AMD. Pre-treatment of the membrane with PTD or TTT does not appear to influence the expression of Hsp70.

Bevasiranib for the treatment of wet, age-related macular degeneration

Age- related Macular Degeneration (AMD) is the leading cause of severe visual impairment in people 65 years and older in industrialized nations. Exudative, or “wet”, AMD is a late form of AMD (as distinguished from atrophic, so-called dry, AMD) and is responsible for over 60% of all cases of blindness due to AMD. It is widely accepted that vascular endothelial growth factor (VEGF) is a key component in the pathogenesis of choroidal neo-vascularization (CNV), which is a precursor to wet AMD. The current gold-standard for treating wet AMD is the monoclonal antibody fragment ranibizumab (trade name Lucentis), which targets VEGF. Other agents used to treat wet AMD include pegaptanib (Macugen), bevacizumab (Avastin; off-label use), and several other experimental agents. The advent of small interfering RNA (siRNA) has presented a whole new approach to inhibiting VEGF. This article reviews the status of a novel siRNA-based therapeutic, bevasiranib, for the treatment of wet AMD. Bevasiranib is believed to work by down regulating VEGF production in the retina. Studies in human cell-lines and animal models have shown that VEGF siRNAs are effective in inhibiting VEGF production. Although there is a lack of sufficient published data on human studies supporting the use of bevasiranib for wet AMD, available data indicates that due to its unique mechanism of action, bevasiranib might hold some promise as a primary or adjunct treatment for wet AMD.