Feasibility demonstration of a device for vitreous liquid biopsy incidental to intravitreal injection

PURPOSE

VitreoDx is an experimental device enabling push-button collection of a neat vitreous liquid biopsy incidental to an intravitreal injection. We explored the ability of the device to collect a sample usable for proteomic biomarker discovery and testing.

DESIGN

Pilot study using ex vivo human eyes.

METHODS

Non-vitrectomized, human eyes from nine donors 75-91 years of age were refrigerated in BSS and used within 5 days of death. Four VitreoDx devices fitted with 25G needles, and four staked needle insulin syringes with 30G needles, were inserted at equal intervals through the pars plana of each eye and held in place by a fixture. The sampling mode of each VitreoDx device was triggered to attempt to acquire a liquid biopsy up to 70 μL. The plunger of each insulin syringe was retracted to attempt to obtain a liquid biopsy with a maximum volume of 50 μL. Samples acquired with the VitreoDx were extracted to polypropylene cryovials, refrigerated to -80 ºC, and sent for offsite proteomic analysis by proximity extension assay with a focus on panels containing approved and pipelined drug targets for neovascular disease and inflammatory factors.

RESULTS

Of the attempted liquid biopsies with the novel 25G VitreoDx, 92% (66 of 72) resulted in successful acquisition (>25 μL) while 89% (64 of 72) attempted by a traditional 30G needle resulted in a successful acquisition. Sample volume sufficient for proteomics array analysis was acquired by the VitreoDx for every eye. Detectable protein was found for 151 of 166 unique proteins assayed in at least 25% of eyes sampled by VitreoDx.

CONCLUSIONS

The high acquisition rate achieved by the prototype was similar to that achieved in previous clinical studies where a standard syringe was used with a 25G needle to biopsy vitreous fluid directly prior to standard intravitreal injection. Successful aspiration rates were likewise high for 30G needles. Together, these suggest that it is possible to routinely acquire liquid vitreous biopsies from patients who typically receive intravitreal injections with an injection device using a standard size needle without a vitreous cutter. Protein analysis shows that proteins of interest survive the sampling mechanism and may have potential to direct care in the future.

Development of the Port Delivery System with ranibizumab for neovascular age-related macular degeneration

PURPOSE OF REVIEW

This review provides background on the remaining unmet needs with antivascular endothelial growth factor (VEGF) therapies for the treatment of neovascular age-related macular degeneration (nAMD). We also discuss the developmental story of the Port Delivery System with ranibizumab (PDS; SUSVIMO, Genentech, Inc., South San Francisco, CA, USA).

RECENT FINDINGS

Real-world studies have shown that undertreatment is a major reason for continued vision loss in the anti-VEGF era. As a result, there is a need for long-acting anti-VEGF treatment options for patients with nAMD, diabetic macular edema, and other retinal diseases. The PDS is a solid state, refillable, intraocular long-acting drug delivery system that continuously delivers a customized formulation of ranibizumab into the vitreous for 6 months. In a phase 3 trial, the PDS showed equivalent visual acuity improvements with monthly ranibizumab injections in patients with nAMD and adverse events associated with the PDS were well understood and manageable.

SUMMARY

The PDS is the first US Food and Drug Administration-approved treatment for nAMD that provides continuous delivery of an anti-VEGF molecule. The PDS offers a unique drug delivery system that has the potential to serve as a platform to be used with other molecules in the future.

Efficacy, durability, and safety of intravitreal faricimab with extended dosing up to every 16 weeks in patients with diabetic macular oedema (YOSEMITE and RHINE): two randomised, double-masked, phase 3 trials

BACKGROUND

To reduce treatment burden and optimise patient outcomes in diabetic macular oedema, we present 1-year results from two phase 3 trials of faricimab, a novel angiopoietin-2 and vascular endothelial growth factor-A bispecific antibody.

METHODS

YOSEMITE and RHINE were randomised, double-masked, non-inferiority trials across 353 sites worldwide. Adults with vision loss due to centre-involving diabetic macular oedema were randomly assigned (1:1:1) to intravitreal faricimab 6·0 mg every 8 weeks, faricimab 6·0 mg per personalised treatment interval (PTI), or aflibercept 2·0 mg every 8 weeks up to week 100. PTI dosing intervals were extended, maintained, or reduced (every 4 weeks up to every 16 weeks) based on disease activity at active dosing visits. The primary endpoint was mean change in best-corrected visual acuity at 1 year, averaged over weeks 48, 52, and 56. Efficacy analyses included the intention-to-treat population (non-inferiority margin 4 Early Treatment Diabetic Retinopathy Study [ETDRS] letters); safety analyses included patients with at least one dose of study treatment. These trials are registered with ClinicalTrials.gov (YOSEMITE NCT03622580 and RHINE NCT03622593).

FINDINGS

3247 patients were screened for eligibility in YOSEMITE (n=1532) and RHINE (n=1715). After exclusions, 940 patients were enrolled into YOSEMITE between Sept 5, 2018, and Sept 19, 2019, and 951 patients were enrolled into RHINE between Oct 9, 2018, and Sept 20, 2019. These 1891 patients were randomly assigned to faricimab every 8 weeks (YOSEMITE n=315, RHINE n=317), faricimab PTI (n=313, n=319), or aflibercept every 8 weeks (n=312, n=315). Non-inferiority for the primary endpoint was achieved with faricimab every 8 weeks (adjusted mean vs aflibercept every 8 weeks in YOSEMITE 10·7 ETDRS letters [97·52% CI 9·4 to 12·0] vs 10·9 ETDRS letters [9·6 to 12·2], difference -0·2 ETDRS letters [-2·0 to 1·6]; RHINE 11·8 ETDRS letters [10·6 to 13·0] vs 10·3 ETDRS letters [9·1 to 11·4] letters, difference 1·5 ETDRS letters [-0·1 to 3·2]) and faricimab PTI (YOSEMITE 11·6 ETDRS letters [10·3 to 12·9], difference 0·7 ETDRS letters [-1·1 to 2·5]; RHINE 10·8 ETDRS letters [9·6 to 11·9], difference 0·5 ETDRS letters [-1·1 to 2·1]). Incidence of ocular adverse events was comparable between faricimab every 8 weeks (YOSEMITE n=98 [31%], RHINE n=137 [43%]), faricimab PTI (n=106 [34%], n=119 [37%]), and aflibercept every 8 weeks (n=102 [33%], n=113 [36%]).

INTERPRETATION

Robust vision gains and anatomical improvements with faricimab were achieved with adjustable dosing up to every 16 weeks, demonstrating the potential for faricimab to extend the durability of treatment for patients with diabetic macular oedema.

FUNDING

F Hoffmann-La Roche.

Building on the success of anti-vascular endothelial growth factor therapy: a vision for the next decade

This article aims to identify key opportunities for improvement in the diagnosis and treatment of retinal disease, and describe recent innovations that will potentially facilitate improved outcomes with existing intravitreal vascular endothelial growth factor (VEGF) therapies and lay the groundwork for new treatment approaches. The review begins with a summary of the key discoveries that led to the development of anti-VEGF therapies and briefly reviews their impact on clinical practice. Opportunities for improvements in diagnosis, real-world outcomes with existing therapies, long-acting therapeutics and personalised health care are discussed, as well as the need to identify new targets for therapeutic intervention. Low-cost, remote patient screening and monitoring using artificial intelligence (AI)-based technologies can help improve diagnosis rates and enable remote disease monitoring with minimal patient burden. AI-based tools can be applied to generate patient-level prognostic data and predict individual treatment needs, reducing the time needed to optimise a patient’s treatment regimen. Long-acting therapeutics can help improve visual outcomes by reducing the treatment burden. When paired with AI-generated prognoses, long-acting therapeutics enable the possibility of vision loss prevention. Dual-acting drugs may help improve efficacy and/or durability beyond what is possible with anti-VEGF agents alone. Recent developments and ongoing innovations will help build upon the success of anti-VEGF therapies to further reduce vision loss owing to retinal disease while lowering the overall burden of care.

Deep Learning Predicts OCT Measures of Diabetic Macular Thickening From Color Fundus Photographs

Purpose

To develop deep learning (DL) models for the automatic detection of optical coherence tomography (OCT) measures of diabetic macular thickening (MT) from color fundus photographs (CFPs).

Methods

Retrospective analysis on 17,997 CFPs and their associated OCT measurements from the phase 3 RIDE/RISE diabetic macular edema (DME) studies. DL with transfer-learning cascade was applied on CFPs to predict time-domain OCT (TD-OCT)-equivalent measures of MT, including central subfield thickness (CST) and central foveal thickness (CFT). MT was defined by using two OCT cutoff points: 250 μm and 400 μm. A DL regression model was developed to directly quantify the actual CFT and CST from CFPs.

Results

The best DL model was able to predict CST ≥ 250 μm and CFT ≥ 250 μm with an area under the curve (AUC) of 0.97 (95% confidence interval [CI], 0.89-1.00) and 0.91 (95% CI, 0.76-0.99), respectively. To predict CST ≥ 400 μm and CFT ≥ 400 μm, the best DL model had an AUC of 0.94 (95% CI, 0.82-1.00) and 0.96 (95% CI, 0.88-1.00), respectively. The best deep convolutional neural network regression model to quantify CST and CFT had an R2 of 0.74 (95% CI, 0.49-0.91) and 0.54 (95% CI, 0.20-0.87), respectively. The performance of the DL models declined when the CFPs were of poor quality or contained laser scars.

Conclusions

DL is capable of predicting key quantitative TD-OCT measurements related to MT from CFPs. The DL models presented here could enhance the efficiency of DME diagnosis in tele-ophthalmology programs, promoting better visual outcomes. Future research is needed to validate DL algorithms for MT in the real-world.

The Port Delivery System with Ranibizumab for Neovascular Age-Related Macular Degeneration: Results from the Randomized Phase 2 Ladder Clinical Trial

PURPOSE

To evaluate the safety and efficacy of the Port Delivery System with ranibizumab (PDS) for neovascular age-related macular degeneration (nAMD) treatment.

DESIGN

Phase 2, multicenter, randomized, active treatment-controlled clinical trial.

PARTICIPANTS

Patients diagnosed with nAMD within 9 months who had received 2 or more prior anti-vascular endothelial growth factor intravitreal injections and were responsive to treatment.

METHODS

Patients were randomized 3:3:3:2 to receive the PDS filled with ranibizumab 10 mg/ml, 40 mg/ml, 100 mg/ml, or monthly intravitreal ranibizumab 0.5-mg injections.

MAIN OUTCOME MEASURES

Time to first implant refill assessed when the last enrolled patient completed the month 9 visit (primary efficacy end point), improvement in best-corrected visual acuity (BCVA) and central foveal thickness (CFT), and safety.

RESULTS

The primary analysis population was 220 patients, with 58, 62, 59, and 41 patients in the PDS 10-mg/ml, PDS 40-mg/ml, PDS 100-mg/ml, and monthly intravitreal ranibizumab 0.5-mg arms, respectively. Median time to first implant refill was 8.7, 13.0, and 15.0 months in the PDS 10-mg/ml, PDS 40-mg/ml, and PDS 100-mg/ml arms, respectively. At month 9, the adjusted mean BCVA change from baseline was ‒3.2 Early Treatment Diabetic Retinopathy Study (ETDRS) letters, ‒0.5 ETDRS letters, +5.0 ETDRS letters, and +3.9 ETDRS letters in the PDS 10-mg/ml, PDS 40-mg/ml, PDS 100-mg/ml, and monthly intravitreal ranibizumab 0.5-mg arms, respectively. At month 9, the adjusted mean CFT change from baseline was similar in the PDS 100-mg/ml and monthly intravitreal ranibizumab 0.5-mg arms. The optimized PDS implant insertion and refill procedures were generally well tolerated. After surgical procedure optimization, postoperative vitreous hemorrhage rate was 4.5% (7/157; 1 event classified as serious). There was no evidence of implant clogging.

CONCLUSIONS

In the phase 2 Ladder trial, the PDS was generally well tolerated and demonstrated a dose response across multiple end points in patients with nAMD. The PDS 100-mg/ml arm showed visual and anatomic outcomes comparable with monthly intravitreal ranibizumab 0.5-mg injections but with a reduced total number of ranibizumab treatments. The PDS has the potential to reduce treatment burden in nAMD while maintaining vision.

Ten years of anti-vascular endothelial growth factor therapy

The targeting of vascular endothelial growth factor A (VEGFA), a crucial regulator of both normal and pathological angiogenesis, has revealed innovative therapeutic approaches in oncology and ophthalmology. The first VEGFA inhibitor, bevacizumab, was approved by the US Food and Drug Administration in 2004 for the first-line treatment of metastatic colorectal cancer, and the first VEGFA inhibitors in ophthalmology, pegaptanib and ranibizumab, were approved in 2004 and 2006, respectively. To mark this tenth anniversary of anti-VEGFA therapy, we discuss the discovery of VEGFA, the successes and challenges in the development of VEGFA inhibitors and the impact of these agents on the treatment of cancers and ophthalmic diseases.

Ocular Angiogenesis: Vascular Endothelial Growth Factor and Other Factors

Systematic study of the mechanisms underlying pathological ocular neovascularization has yielded a wealth of knowledge about pro- and anti-angiogenic factors that modulate diseases such as neovascular age-related macular degeneration. The evidence implicating vascular endothelial growth factor (VEGF) in particular has led to the development of a number of approved anti-VEGF therapies. Additional proangiogenic targets that have emerged as potential mediators of ocular neovascularization include hypoxia-inducible factor-1, angiopoietin-2, platelet-derived growth factor-B and components of the alternative complement pathway. As for VEGF, knowledge of these factors has led to a product pipeline of many more novel agents that are in various stages of clinical development in the setting of ocular neovascularization. These agents are represented by a range of drug classes and, in addition to novel small- and large-molecule VEGF inhibitors, include gene therapies, small interfering RNA agents and tyrosine kinase inhibitors. In addition, combination therapy is beginning to emerge as a strategy to improve the efficacy of individual therapies. Thus, a variety of agents, whether administered alone or as adjunctive therapy with agents targeting VEGF, offer the promise of expanding the range of treatments for ocular neovascular diseases.

Spontaneous CNV in a novel mutant mouse is associated with early VEGF-A-driven angiogenesis and late-stage focal edema, neural cell loss, and dysfunction

PURPOSE

Characterization of a mouse model of spontaneous choroidal neovascularization (sCNV) and its effect on retinal architecture and function.

METHODS

The sCNV mouse phenotype was characterized by using fundus photography, fluorescein angiography, confocal scanning laser ophthalmoscopy (SLO), optical coherence tomography (OCT), ERG, immunostaining, biochemistry, and electron microscopy. A role for VEGF-A signaling in sCNV was investigated by using neutralizing antibodies and a role for macrophages explored by cell-depletion studies.

RESULTS

The sCNV starts between postnatal day 10 and 15 (P10-P15), increasing in number and severity causing RPE disruption and dysfunction. Various morphological methods confirmed the choroidal origin and subretinal position of the angiogenic vessels. At approximately P25, vessels were present in the outer retina with instances of anastomosis of some sCNV lesions with the retinal vasculature. The number of CNV lesions was significantly decreased by systemic blockade of the VEGF-A pathway. Choroidal neovascularization size also was significantly modulated by reducing the number of lesion-associated macrophages. Later stages of sCNV were associated with edema, neuronal loss, and dysfunction.

CONCLUSIONS

The sCNV mouse is a new model for the study of both early and late events associated with choroidal neovascularization. Pharmacological reduction in sCNV with VEGF-A antagonists and an anti-inflammatory strategy suggests the model may be useful for investigating novel targets for treating human ocular neovascular disease.

Long-term outcomes of ranibizumab therapy for diabetic macular edema: the 36-month results from two phase III trials: RISE and RIDE

PURPOSE

To report 36-month outcomes of RIDE (NCT00473382) and RISE (NCT00473330), trials of ranibizumab in diabetic macular edema (DME).

DESIGN

Phase III, randomized, multicenter, double-masked, 3-year trials, sham injection-controlled for 2 years.

PARTICIPANTS

Adults with DME (n=759), baseline best-corrected visual acuity (BCVA) 20/40 to 20/320 Snellen equivalent, and central foveal thickness (CFT) ≥ 275 μm on optical coherence tomography.

METHODS

Patients were randomized equally (1 eye per patient) to monthly 0.5 mg or 0.3 mg ranibizumab or sham injection. In the third year, sham patients, while still masked, were eligible to cross over to monthly 0.5 mg ranibizumab. Macular laser was available to all patients starting at month 3; panretinal laser was available as necessary.

MAIN OUTCOME MEASURES

The proportion of patients gaining ≥15 Early Treatment Diabetic Retinopathy Study letters in BCVA from baseline at month 24.

RESULTS

Visual acuity (VA) outcomes seen at month 24 in ranibizumab groups were consistent through month 36; the proportions of patients who gained ≥15 letters from baseline at month 36 in the sham/0.5 mg, 0.3 mg, and 0.5 mg ranibizumab groups were 19.2%, 36.8%, and 40.2%, respectively, in RIDE and 22.0%, 51.2%, and 41.6%, respectively, in RISE. In the ranibizumab arms, reductions in CFT seen at 24 months were, on average, sustained through month 36. After crossover to 1 year of treatment with ranibizumab, average VA gains in the sham/0.5 mg group were lower compared with gains seen in the ranibizumab patients after 1 year of treatment (2.8 vs. 10.6 and 11.1 letters). Per-injection rates of endophthalmitis remained low over time (∼0.06% per injection). The incidence of serious adverse events potentially related to systemic vascular endothelial growth factor inhibition was 19.7% in patients who received 0.5 mg ranibizumab compared with 16.8% in the 0.3 mg group.

CONCLUSIONS

The strong VA gains and improvement in retinal anatomy achieved with ranibizumab at month 24 were sustained through month 36. Delayed treatment in patients receiving sham treatment did not seem to result in the same extent of VA improvement observed in patients originally randomized to ranibizumab. Ocular and systemic safety was generally consistent with the results seen at month 24.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

Preclinical evaluation of the novel small-molecule integrin alpha5beta1 inhibitor JSM6427 in monkey and rabbit models of choroidal neovascularization

OBJECTIVE

To evaluate the pharmacologic activity and tolerability of JSM6427, a potent and first selective small-molecule inhibitor of integrin alpha5beta1, in monkey and rabbit models of choroidal neovascularization (CNV).

METHODS

JSM6427 selectivity for alpha5beta1 was evaluated by in vitro binding assays while the ability of JSM6427 to inhibit CNV was investigated in a laser-induced monkey model and a growth factor-induced rabbit model. Intravitreal injections of JSM6427 (100, 300, or 1000 microg) or vehicle were administered immediately after the CNV induction procedure and at weekly intervals for 4 weeks. Fluorescein angiography was performed weekly. Ocular tolerability was evaluated ophthalmoscopically and histologically in both models; additional assessments in monkeys included electroretinography, biomicroscopy, pathological examination, and analysis of JSM6427 pharmacokinetics.

RESULTS

JSM6427 was highly selective for the alpha5beta1-fibronectin interaction. Weekly intravitreal injections of JSM6427 resulted in a statistically significant dose-dependent inhibition of CNV in laser-induced and growth factor-induced models without any ocular JSM6427-related adverse effects. JSM6427 was cleared through the systemic circulation with no evidence of systemic accumulation.

CONCLUSIONS

Intravitreal JSM6427 provided dose-dependent inhibition of CNV in monkey and rabbit experimental models.

CLINICAL RELEVANCE

JSM6427 may provide a new approach for the treatment of ocular neovascular diseases such as age-related macular degeneration in humans.

Pegaptanib sodium for macular edema secondary to central retinal vein occlusion

OBJECTIVES

To assess the safety and efficacy of intravitreous pegaptanib sodium for the treatment of macular edema following central retinal vein occlusion (CRVO).

DESIGN

This dose-ranging, double-masked, multicenter, phase 2 trial included subjects with CRVO for 6 months' or less duration randomly assigned (1:1:1) to receive pegaptanib sodium or sham injections every 6 weeks for 24 weeks (0.3 mg and 1 mg, n=33; sham, n=32).

MAIN OUTCOME MEASURE

Visual acuity at week 30.

RESULTS

In the primary analysis at week 30, 12 of 33 (36%) subjects treated with 0.3 mg of pegaptanib sodium and 13 of 33 (39%) treated with 1 mg gained 15 or more letters from baseline vs 9 of 32 (28%) sham-treated subjects (P= .48 for 0.3 mg and P= .35 for 1 mg of pegaptanib sodium vs sham). In secondary analyses, subjects treated with pegaptanib sodium were less likely to lose 15 or more letters (9% and 6%; 0.3-mg and 1-mg pegaptanib sodium groups, respectively) compared with sham-treated eyes (31%; P= .03 for 0.3 mg and P= .01 for 1 mg of pegaptanib sodium vs sham) and showed greater improvement in mean visual acuity (+7.1 and +9.9, respectively, vs -3.2 letters with sham; P= .09 for 0.3 mg and P= .02 for 1 mg of pegaptanib sodium vs sham). By week 1, the mean central retinal thickness decreased in the 0.3-mg and 1-mg pegaptanib sodium groups by 269 microm and 210 microm, respectively, vs 5 microm with sham (P< .001).

CONCLUSIONS

Based on this 30-week study, intravitreous pegaptanib sodium appears to provide visual and anatomical benefits in the treatment of macular edema following CRVO.

APPLICATION TO CLINICAL PRACTICE

Benefits accrued with intravitreous pegaptanib sodium treatment of macular edema following CRVO suggest a role for vascular endothelial growth factor in the pathogenesis of this condition.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00088283.

Pegaptanib sodium for neovascular age-related macular degeneration: third-year safety results of the VEGF Inhibition Study in Ocular Neovascularisation (VISION) trial

Aims:

To evaluate the safety of up to 3 years of pegaptanib sodium therapy in the treatment of neovascular age-related macular degeneration (NV-AMD).

Methods:

Two concurrent, prospective, multicentre, double-masked studies randomised subjects with all angiographic lesion compositions of NV-AMD to receive intravitreous pegaptanib sodium (0.3, 1 and 3 mg) or sham injections every 6 weeks for 54 weeks. Those initially assigned to pegaptanib were rerandomised to continue or discontinue therapy for 48 more weeks; sham-treated subjects continued sham, discontinued or received pegaptanib. At 102 weeks, subjects receiving pegaptanib 0.3 mg or 1 mg in years 1 or 2 continued; those receiving pegaptanib 3 mg or who did not receive treatment in years 1 and 2 were rerandomised to 0.3 mg or 1 mg for year 3.

Results:

As in years 1 and 2, pegaptanib was well tolerated in year 3. Adverse events were mainly ocular in nature, mild, transient and injection-related. Serious adverse events were rare. No evidence of systemic safety signals attributed to vascular endothelial growth factor inhibition arose in year 3. There were no findings in relation to vital signs or electrocardiogram results suggesting a relationship to pegaptanib treatment.

Conclusion:

The 3-year safety profile of pegaptanib sodium was favourable in patients with NV-AMD.

Cost-effectiveness model for neovascular age-related macular degeneration: comparing early and late treatment with pegaptanib sodium based on visual acuity

OBJECTIVE

To compare the cost-effectiveness of pegaptanib and usual care within three distinct cohorts of subfoveal neovascular age-related macular degeneration (NV-AMD) patients, that is, those with early, moderate, and late disease, using a comprehensive economic model.

METHODS

A Markov framework was used to model lifetime movement of a subfoveal NV-AMD cohort through health states based on visual acuity. The model takes a US payer perspective of patients over the age of 65 years. Clinical efficacy was based on published results for the 0.3 mg pegaptanib and usual care groups. Expert interviews were conducted to determine adverse event treatment patterns and vision rehabilitation resource use. Incidence and costs of comorbidities such as depression and fractures associated with the effects of declining visual acuity were based on our previously published analysis of Medicare data. Transition probabilities were derived from published clinical trial data for each 3-month cycle. Utilities were derived from published sources. Three runs of the model were conducted with cohorts of newly diagnosed patients. Patients were classified as having early, moderate, or late NV-AMD defined as visual acuity in the better-seeing eye of 20/40 to more than 20/80, 20/80 to more than 20/200, and 20/200 to more than 20/400, respectively. Costs and outcomes were discounted 3.0% per annum.

RESULTS

Incremental costs per vision-year gained and per quality-adjusted life-year (QALY) gained for early NV-AMD patients were approximately one-third those of patients with late disease ($15,279 vs. $57,230 and $36,282 vs. $132,381, respectively). On average, patients treated early with either pegaptanib or usual care incurred lower lifetime total direct costs than those treated later. Sensitivity analysis showed that base-case incremental costs per QALY gained for pegaptanib versus usual care were relatively robust.

CONCLUSIONS

For patients with subfoveal NV-AMD, treatment with pegaptanib should be started as early as possible to maximize the clinical and economic benefits.

Immunological mechanisms in the pathogenesis of diabetic retinopathy

There is an accumulating body of evidence that immunological mechanisms play a prominent role in the pathogenesis of diabetic retinopathy (DR), which is characterized by many features typical of inflammation. The upregulation of cytokines and other inflammatory mediators leading to persistent low-grade inflammation and an influx of leukocytes, is believed to contribute actively to DR-associated damage to the retinal vasculature and retinal neovascularization. This review will describe preclinical and clinical studies that document an inflammatory basis for DR and that support the use of nonsteroidal anti-inflammatory drugs, corticosteroids, and anti-vascular endothelial growth factor agents in its treatment. In addition, emerging therapeutic approaches based on ongoing investigations will be discussed, including those involving blockade of angiotensin receptors and other molecular targets such as tumor necrosis factor-alpha.

Simultaneous but not prior inhibition of VEGF165 enhances the efficacy of photodynamic therapy in multiple models of ocular neovascularization

PURPOSE

To investigate the effect of the combined treatment of photodynamic therapy and specific VEGF165 inhibition with pegaptanib sodium (Macugen; Eyetech Pharmaceuticals, Lexington, MA) on ocular neovascularization.

METHODS

Photodynamic therapy's (PDT's) effects on the integrity of pegaptanib sodium were analyzed by HPLC, a VEGF165-binding assay, and a VEGF165-induced tissue factor gene expression assay. The effects of mono- or combined treatment on vessel growth and regression were determined in a murine corneal neovascularization model. The effects of combined treatment on vessel growth were also determined in a murine choroidal neovascularization model.

RESULTS

PDT did not affect the chemical composition of pegaptanib sodium nor the efficacy of pegaptanib sodium in the inhibition of VEGF165 binding to Flt-1 and VEGF165-induced gene expression. In an animal model of effects on existing ocular neovascular lesions (corneal neovascularization), PDT monotherapy yielded an initial regression of these vessels, but there followed a rapid regrowth. In contrast, pegaptanib sodium monotherapy yielded little regression but potently abrogated further vessel growth. The combination of pegaptanib sodium and PDT resulted in the regression of the neovascular lesions, as observed with PDT alone, but also prevented significant vessel regrowth, leading to a significantly greater reduction in lesion size than did each monotherapy. In addition, there was a significantly greater effect of the combination of pegaptanib sodium and PDT on lesion size in choroidal neovascularization than with each monotherapy. Pretreatment with pegaptanib sodium appeared to decrease the efficacy of PDT-induced vessel regression in corneal neovascularization, and as such the enhanced efficacy over monotherapy when the agents were delivered simultaneously was not observed.

CONCLUSIONS

Although the combined simultaneous treatment of ocular neovascularization with PDT and pegaptanib sodium may provide a more effective approach for the regression and overall treatment of CNV associated with AMD, the order of addition of these treatments may play a role in achieving optimal efficacy.

Vascular endothelial growth factor-A is a survival factor for retinal neurons and a critical neuroprotectant during the adaptive response to ischemic injury

Vascular endothelial growth factor-A (VEGF-A) has recently been recognized as an important neuroprotectant in the central nervous system. Given its position as an anti-angiogenic target in the treatment of human diseases, understanding the extent of VEGF's role in neural cell survival is paramount. Here, we used a model of ischemia-reperfusion injury and found that VEGF-A exposure resulted in a dose-dependent reduction in retinal neuron apoptosis. Although mechanistic studies suggested that VEGF-A-induced volumetric blood flow to the retina may be partially responsible for the neuroprotection, ex vivo retinal culture demonstrated a direct neuroprotective effect for VEGF-A. VEGF receptor-2 (VEGFR2) expression was detected in several neuronal cell layers of the retina, and functional analyses showed that VEGFR2 was involved in retinal neuroprotection. VEGF-A was also shown to be involved in the adaptive response to retinal ischemia. Ischemic preconditioning 24 hours before ischemia-reperfusion injury increased VEGF-A levels and substantially decreased the number of apoptotic retinal cells. The protective effect of ischemic preconditioning was reversed after VEGF-A inhibition. Finally, chronic inhibition of VEGF-A function in normal adult animals led to a significant loss of retinal ganglion cells yet had no observable effect on several vascular parameters. These findings have implications for both neural pathologies and ocular vascular diseases, such as diabetic retinopathy and age-related macular degeneration.

Pegaptanib 1-year systemic safety results from a safety-pharmacokinetic trial in patients with neovascular age-related macular degeneration

OBJECTIVE

To characterize the safety, tolerability, and pharmacokinetics of the pegylated anti-vascular endothelial growth factor (VEGF) aptamer pegaptanib sodium in subfoveal choroidal neovascularization secondary to age-related macular degeneration (AMD).

DESIGN

Prospective 2-cohort study: (1) open-label cohort and (2) randomized, double-masked, uncontrolled multicenter trial.

PARTICIPANTS

In the combined cohorts, 147 subjects with any angiographic subtype of subfoveal choroidal neovascularization secondary to AMD and best-corrected visual acuities (VAs) in the study eye of 20/40 to 20/320 and in the fellow eye of 20/800 or better received pegaptanib sodium.

INTERVENTION

Subjects were randomized to receive intravitreous pegaptanib sodium (1 mg or 3 mg [3- and 10-fold higher than the 0.3-mg approved dose]) every 6 weeks for 54 weeks.

MAIN OUTCOME MEASURES

Safety assessments included blood chemistries, urinalyses, vital signs, electrocardiograms, serum antipegaptanib antibody assays, adverse events, VAs, and intraocular pressures. After the first, fourth, and eighth injections, serial blood samples were obtained for quantification of pegaptanib plasma concentrations.

RESULTS

No antipegaptanib immunoglobulin G (IgG) or IgM antibodies were detected. Few systemic adverse events were noted. Mild or moderate ocular adverse events related to the injection procedure were reported in most patients. Pegaptanib did not accumulate in plasma after multiple doses; systemic exposures were similar after the first, fourth, and eighth doses. The mean apparent terminal half-life was 10 days. Evaluation of blood pressure (BP) and urine protein, both of which are known to be affected by systemic VEGF inhibition, indicated no evidence of a pegaptanib treatment effect on these parameters. Mean BP at the end of year 1 remained below 140 mmHg (systolic) and 90 mmHg (diastolic), levels considered hypertension by the American College of Cardiology.

CONCLUSIONS

At doses up to 10-fold higher than the 0.3-mg dose approved for the treatment of AMD, pegaptanib sodium was well tolerated, with no detectable clinical evidence of systemic VEGF inhibition (i.e., no clinically meaningful changes in proteinuria or mean BP) and no clinically relevant ocular inflammation. Most ocular adverse events were related to the injection procedure itself and were mild or moderate in severity.

Anti-VEGF aptamer (pegaptanib) therapy for ocular vascular diseases

Vascular endothelial growth factor (VEGF) is a central regulator of both physiological and pathological angiogenesis. Pegaptanib, a 28-nucleotide RNA aptamer specific for the VEGF(165) isoform, binds to it in the extracellular space, leaving other isoforms unaffected, and inhibits such key VEGF actions as promotion of endothelial cell proliferation and survival, and vascular permeability. Pegaptanib already has been examined as a treatment for two diseases associated with ocular neovascularization, age-related macular degeneration (AMD) and diabetic macular edema (DME). Preclinical studies have shown that VEGF(165) alone mediates pathological ocular neovascularization and that its inactivation by pegaptanib inhibits the choroidal neovascularization observed in patients with neovascular AMD. In contrast, physiological vascularization, which is supported by the VEGF(121) isoform, is unaffected by this inactivation of VEGF(165). In addition, animal model studies have shown that intravitreous injection of pegaptanib can inhibit the breakdown of the blood-retinal barrier characteristic of diabetes and even can reverse this damage to some degree. These preclinical findings formed the basis for randomized controlled trials examining the efficacy of pegaptanib as a therapy for AMD and DME. The VEGF Inhibition Study in Ocular Neovascularization (VISION) trial comprising two replicate, pivotal phase 3 studies, demonstrated that intravitreous injection of pegaptanib resulted in significant clinical benefit, compared with sham injection, for all prespecified clinical end points, irrespective of patient demographics or angiographic subtype, and led to pegaptanib's approval as a treatment for AMD. A phase 2 trial has provided support for the efficacy of intravitreous pegaptanib in the treatment of DME.

Erythropoietin promotes survival of retinal ganglion cells in DBA/2J glaucoma mice

PURPOSE

Retinal ganglion cell (RGC) loss occurs in response to increased intraocular pressure (IOP) and/or retinal ischemia in glaucoma and leads to impairment of vision. This study was undertaken to test the efficacy of erythropoietin (EPO) in providing neuroprotection to RGCs in vivo.

METHODS

The neuroprotective effects of EPO were studied in the DBA/2J mouse model of glaucoma. Mice were intraperitoneally injected with control substances or various doses of EPO, starting at the age of 6 months and continuing for an additional 2, 4, or 6 months. RGCs were labeled retrogradely by a gold tracer. IOP was measured with a microelectric-mechanical system, and EPO receptor (EPOR) expression was detected by immunohistochemistry. Axonal death in the optic nerve was quantified by para-phenylenediamine staining, and a complete blood count system was used to measure the number of erythrocytes.

RESULTS

In DBA/2J mice, the average number of viable RGCs significantly decreased from 4 months to 10 months, with an inverse correlation between the number of dead optic nerve axons and viable RGCs. Treatment with EPO at doses of 3000, 6000, and 12,000 U/kg body weight per week all prevented significant RGC loss, compared with untreated DBA/2J control animals. EPO effects were similar to those of memantine, a known neuroprotective agent. IOP, in contrast, was unchanged by both EPO and memantine. Finally, EPOR was expressed in the RGC layer in both DBA/2J and C57BL/6J mice.

CONCLUSIONS

EPO promoted RGC survival in DBA/2J glaucomatous mice without affecting IOP. These results suggest that EPO may be a potential therapeutic neuroprotectant in glaucoma.

Inhibition of diabetic leukostasis and blood-retinal barrier breakdown with a soluble form of a receptor for advanced glycation end products

PURPOSE

The interaction of advanced glycation end products (AGEs) with their receptors is hypothesized to be involved in the development of diabetic retinopathy. In the present study, the role of an AGE receptor, RAGE, was investigated in the development of diabetic retinopathy in vivo.

METHODS

C57/BJ6 and RAGE-transgenic mice that carried human RAGE genetic DNA under the control of the murine flk-1 promoter were made diabetic with streptozocin. Three months after the onset of diabetes, the soluble form of RAGE (sRAGE) or mouse serum albumin was injected intraperitoneally at 100 mug/d for 14 consecutive days. After the final injection, blood-retinal barrier breakdown, retinal leukostasis, expression of VEGF and ICAM-1, and expression of RAGE in the retina were investigated.

RESULTS

Blood-retinal barrier breakdown and increased leukostasis were associated with the experimental diabetes in the C57/BJ6 mice. These changes were significantly augmented in RAGE-transgenic mice. The blood-retinal barrier breakdown and leukostasis in the diabetic C57/BJ6 and RAGE-transgenic mice were accompanied by increased expression of VEGF and ICAM-1 in the retina. The systemic administration of sRAGE significantly inhibited blood-retinal barrier breakdown, leukostasis, and expression of ICAM-1 in the retina in both the diabetic C57/BJ6 and RAGE-transgenic mice. The expression of RAGE was slightly increased in the retinal vessels in diabetic or RAGE-transgenic mice. Furthermore, a strong induction of RAGE was observed in the retinal vessels of diabetic RAGE-transgenic mice.

CONCLUSIONS

This study further demonstrates the role of the AGEs and RAGE axis in blood-retinal barrier breakdown and the retinal leukostasis, which are characteristic clinical symptoms of diabetic retinopathy. Furthermore, these data demonstrate that blocking AGE bioactivity may be effective for the treatment of diabetic retinopathy.

Vascular endothelial growth factor and the potential therapeutic use of pegaptanib (macugen) in diabetic retinopathy

Both clinical and preclinical findings have implicated vascular endothelial growth factor (VEGF) in the pathophysiology of diabetic macular edema (DME). VEGF is both a potent enhancer of vascular permeability and a key inducer of angiogenesis. VEGF levels are elevated in the eyes of patients with DME, and in animal models of diabetes this elevation coincides with the breakdown of the blood-retinal barrier. Moreover, injection of VEGF (the VEGF165 isoform in particular) into healthy eyes of animals can induce diabetes-associated ocular pathologies.Pegaptanib, a novel RNA aptamer currently used in the treatment of agerelated macular degeneration, binds and inactivates VEGF165 and has been shown in animal models to reverse the blood-retinal barrier breakdown associated with diabetes. These findings formed the basis of a phase II trial involving 172 patients with DME, in which intravitreous pegaptanib (0.3 mg, 1 mg, 3 mg) or sham injections were administered every 6 weeks for 12 weeks, with the option of continuing for 18 more weeks or undergoing laser treatment. Compared to sham, patients receiving 0.3 mg displayed superior visual acuity (p = 0.04) as well as a reduction in retinal thickness of 68 micrometers compared to a slight increase under sham treatment (p = 0.021). These data support the use of pegaptanib in the treatment of DME.

Molecular biology of choroidal neovascularization

VEGF plays a pivotal role in the neovascularization of the choroid in AMD. Anti-VEGF agents have been developed to target VEGF itself or its receptor signal transduction pathway, and have shown promising results in clinical trials. The combination of anti-VEGF strategies with established treatment modalities may have additional efficacy. Safe and effective drug-delivery systems are also required for the successful anti-VEGF therapies for AMD and other ocular diseases with CNV.

Inhibitory effect of an antibody to cryptic collagen type IV epitopes on choroidal neovascularization

PURPOSE

The wet form of age-related macular degeneration (AMD) occurs as a consequence of abnormal blood vessel growth from the choroid into the retina. Pathological angiogenesis during tumor growth and ocular disease has been associated with specific exposure of cryptic extracellular matrix epitopes. We investigated the presence of cryptic collagen IV epitopes in a murine model of choroidal neovascularization (CNV), and tested the effect on blood vessel growth of H8, a humanized antibody directed against a cryptic collagen type IV epitope.

METHODS

To induce experimental CNV in adult C57BL/6 mice, Bruch's membrane was ruptured using a diode laser. Subsequently, mice were treated with daily intraperitoneal (i.p.) injections of either H8 (10 mg/kg or 30 mg/kg) or an isotype-matched antibody control. Two weeks postinjection, choroidal flat mounts were immunostained with the blood vessel marker platelet/endothelial cell adhesion molecule-1 (PECAM-1) and H8. CNV was visualized using fluorescence microscopy and the CNV lesion area measured using Open Lab software.

RESULTS

Collagen type IV and the cryptic epitope were observed at the site of laser-induced lesions. Staining with H8 was first observed three days post injury, two days after MMP2 expression in CNV lesions, becoming most intense five days following laser injury and extending beyond the area of neovascularization. At 14 days post injury, H8 staining was reduced in intensity, colocalized with the area of CNV, and was nearly absent from the underlying choroidal vessels. In addition, mice treated with H8 had a significant dose-dependent decrease in the area of CNV as compared to isotype-matched antibody controls.

CONCLUSIONS

Results suggest that exposure of cryptic collagen type IV epitopes is associated with the incidence of CNV and that the humanized antibody H8 may provide a new treatment for CNV.

Targeting angiogenesis, the underlying disorder in neovascular age-related macular degeneration

Angiogenesis has a causal role in many diseases, including neovascular age-related macular degeneration (AMD). Identification of key regulators of angiogenesis, including vascular endothelial growth factor (VEGF), fibroblast growth factor 2, pigment epithelium-derived growth factor, angiopoietins and extracellular matrix molecules, has facilitated the development of novel therapeutic agents that target the underlying pathological angiogenic process. Among these, VEGF serves as a "master switch" for many ocular neovascular conditions through its promotion of endothelial cell proliferation and survival, vascular permeability and ocular inflammation. Two anti-VEGF agents are now clinically available: bevacizumab, an antibody for metastatic colorectal cancer, and pegaptanib sodium, an aptamer for neovascular AMD. Unlike bevacizumab, which binds all VEGF isoforms, pegaptanib targets only VEGF165, the isoform responsible for pathological ocular neovascularization and thus an ideal target for treatment of AMD. Although other therapies targeting angiogenesis in AMD are in clinical development, to date, pegaptanib is the only therapy approved by the Food and Drug Administration of the United States for the treatment of all neovascular AMD and represents a valuable addition to the hitherto limited options available for patients.

Year 2 efficacy results of 2 randomized controlled clinical trials of pegaptanib for neovascular age-related macular degeneration

OBJECTIVE

To evaluate the efficacy of a second year of pegaptanib sodium therapy in patients with neovascular age-related macular degeneration (AMD).

DESIGN

Two concurrent, multicenter, randomized, double-masked, sham-controlled studies (V.I.S.I.O.N. [Vascular Endothelial Growth Factor Inhibition Study in Ocular Neovascularization] trials).

PARTICIPANTS

Patients with all angiographic neovascular lesion compositions of AMD were enrolled. In combined analyses, 88% (1053/1190) were re-randomized at week 54, and 89% (941/1053) were assessed at week 102.

INTERVENTIONS

At week 54, those initially assigned to pegaptanib were re-randomized (1:1) to continue or discontinue therapy for 48 more weeks (8 injections). Those initially assigned to sham were re-randomized to continue sham, discontinue sham, or receive 1 of 3 pegaptanib doses.

MAIN OUTCOME MEASURES

Mean change in visual acuity (VA) over time and mean change in the standardized area under the curve of VA and proportions of patients experiencing a loss of > or =15 letters from week 54 to week 102; losing <15 letters (responders) from baseline to week 102; gaining > or =0, > or =1, > or =2, and > or =3 lines of VA; and progressing to legal blindness (20/200 or worse).

RESULTS

In combined analysis, mean VA was maintained in patients continuing with 0.3-mg pegaptanib compared with those discontinuing therapy or receiving usual care. In patients who continued pegaptanib, the proportion who lost >15 letters from baseline in the period from week 54 to week 102 was half (7%) that of patients who discontinued pegaptanib or remained on usual care (14% for each). Kaplan-Meier analysis showed that patients continuing 0.3-mg pegaptanib for a second year were less likely to lose > or =15 letters than those re-randomized to discontinue after 1 year (P<0.05). The proportion of patients gaining vision was higher for those assigned to 2 years of 0.3-mg pegaptanib than receiving usual care. Progression to legal blindness was reduced for patients continuing 0.3-mg pegaptanib for 2 years.

CONCLUSIONS

Continuing visual benefit was observed in patients who were randomized to receive therapy with pegaptanib in year 2 of the V.I.S.I.O.N. trials when compared with 2 years' usual care or cessation of therapy at year 1.

Inhibition of platelet-derived growth factor B signaling enhances the efficacy of anti-vascular endothelial growth factor therapy in multiple models of ocular neovascularization

'Vascular endothelial growth factor-A (VEGF-A) blockade has been recently validated as an effective strategy for the inhibition of new blood vessel growth in cancer and ocular pathologies. However, several studies have also shown that anti-VEGF therapy may not be as effective in the treatment of established unwanted blood vessels, suggesting they may become less dependent on VEGF-A for survival. The VEGF-A dependence of vessels may be related to the presence of vascular mural cells (pericytes or smooth muscle cells). Mural cell recruitment to the growing endothelial tube is regulated by platelet-derived growth factor-B (PDGF-B) signaling, and interference with this pathway causes disruption of endothelial cell-mural cell interactions and loss of mural cells. We have investigated the basis of blood vessel dependence on VEGF-A in models of corneal and choroidal neovascularization using a combination of reagents (an anti-VEGF aptamer and an anti-PDGFR-beta antibody) to inhibit both the VEGF-A and PDGF-B signaling pathways. We demonstrate that neovessels become refractory to VEGF-A deprivation over time. We also show that inhibition of both VEGF-A and PDGF-B signaling is more effective than blocking VEGF-A alone at causing vessel regression in multiple models of neovascular growth. These findings provide insight into blood vessel growth factor dependency and validate a combination therapy strategy for enhancing the current treatments for ocular angiogenic disease.

Proceedings of the Third International Symposium on Retinopathy of Prematurity: an update on ROP from the lab to the nursery (November 2003, Anaheim, California)

The Third International Symposium on Retinopathy of Prematurity (ROP) was convened with the aim of cross fertilizing the horizons of basic and clinical scientists with an interest in the pathogenesis and management of infants with ROP. Ten speakers in the clinical sciences and ten speakers in the basic sciences were recruited on the basis of their research to provide state of the art talks. The meeting was held November 9, 2003 immediately prior to the American Academy of Ophthalmology meeting; scholarships were provided for outreach to developing countries and young investigators. This review contain the summaries of the 20 platform presentations prepared by the authors and the abstracts of presented posters. Each author was asked to encapsulate the current state of understanding, identify areas of controversy, and make recommendations for future research. The basic science presentations included insights into the development of the human retinal vasculature, animal models for ROP, growth factors that affect normal development and ROP, and promising new therapeutic approaches to treating ROP like VEGF targeting, inhibition of proteases, stem cells, ribozymes to silence genes, and gene therapy to deliver antiangiogenic agents. The clinical presentations included new insights into oxygen management, updates on the CRYO-ROP and ETROP studies, visual function in childhood following ROP, the neural retina in ROP, screening for ROP, management of stage 3 and 4 ROP, ROP in the third world, and the complications of ROP in adult life. The meeting resulted in a penetrating exchange between clinicians and basic scientists, which provided great insights for conference attendees. The effect of preterm delivery on the normal cross-talk of neuroretinal and retinal vascular development is a fertile ground for discovering new understanding of the processes involved both in normal development and in retinal neovascular disorders. The meeting also suggested promising potential therapeutic interventions on the horizon for ROP.

Pegaptanib sodium for neovascular age-related macular degeneration: two-year safety results of the two prospective, multicenter, controlled clinical trials

OBJECTIVE

To evaluate the safety of pegaptanib sodium injection, a specific vascular endothelial growth factor (VEGF) antagonist, in the treatment of neovascular age-related macular degeneration (AMD) during 2 years of therapy.

DESIGN

Two concurrent, prospective, randomized, multicenter, double-masked, sham-controlled studies.

METHODS

Patients with all angiographic choroidal neovascularization lesion compositions of AMD received either intravitreous pegaptanib sodium (0.3 mg, 1 mg, 3 mg) or sham injections every 6 weeks for 54 weeks. Those initially assigned to pegaptanib were re-randomized (1:1) to continue or discontinue therapy for 48 more weeks; sham-treated patients were re-randomized (1:1:1:1:1) to continue sham, discontinue, or receive one of the pegaptanib doses.

MAIN OUTCOME MEASURES

All reported adverse events, serious adverse events, and deaths.

PARTICIPANTS

In year 1, 1190 subjects received at least one study treatment (0.3 mg, n = 295; 1 mg, n = 301; 3 mg, n = 296; sham, n = 298); 7545 intravitreous injections of pegaptanib were administered. In year 2, 425 subjects (0.3 mg, n = 128; 1 mg, n = 126; 3 mg, n = 120; sham, n = 51) continued the same masked treatment as in year 1 and received at least one study treatment in year 2; 2663 intravitreous injections of pegaptanib were administered in these subjects.

RESULTS

All doses of pegaptanib were well tolerated. The most common ocular adverse events were transient, mild to moderate in intensity, and attributed to the injection preparation and procedure. There was no evidence of an increase in deaths, in events associated with systemic VEGF inhibition (e.g., hypertension, thromboembolic events, serious hemorrhagic events), or in severe ocular inflammation, cataract progression, or glaucoma in pegaptanib-treated patients relative to sham-treated patients. In year 1, serious injection-related complications included endophthalmitis (12 events, 0.16%/injection), retinal detachment (RD) (6 events [4 rhegmatogenous, 2 exudative], 0.08%/injection), and traumatic cataract (5 events, 0.07%/injection). Most cases of endophthalmitis followed violations of the injection preparation protocol. In patients receiving pegaptanib for >1 year, there were no reports of endophthalmitis or traumatic cataract in year 2; RD was reported in 4 patients (all rhegmatogenous, 0.15%/injection).

CONCLUSION

The 2-year safety profile of pegaptanib sodium is favorable in patients with exudative AMD.

Pegaptanib, a targeted anti-VEGF aptamer for ocular vascular disease

Aptamers are oligonucleotide ligands that are selected for high-affinity binding to molecular targets. Pegaptanib sodium (Macugen; Eyetech Pharmaceuticals/Pfizer) is an RNA aptamer directed against vascular endothelial growth factor (VEGF)-165, the VEGF isoform primarily responsible for pathological ocular neovascularization and vascular permeability. After nearly a decade of preclinical development to optimize and characterize its biological effects, pegaptanib was shown in clinical trials to be effective in treating choroidal neovascularization associated with age-related macular degeneration. Pegaptanib therefore has the notable distinction of being the first aptamer therapeutic approved for use in humans, paving the way for future aptamer applications.

Changes in retinal neovascularization after pegaptanib (Macugen) therapy in diabetic individuals

OBJECTIVE

To study effects of intravitreal pegaptanib (Macugen) on retinal neovascularization.

DESIGN

Retrospective analysis of a randomized clinical trial. PARTICIPANTS, INTERVENTION, AND MAIN OUTCOME MEASURES: Individuals with retinal neovascularization identified from a multicenter, randomized, controlled trial evaluating pegaptanib for treatment of diabetic macular edema, with a best-corrected visual acuity letter score between 68 and 25 (approximate Snellen equivalent between 20/50 and 20/320) and receiving a sham injection or intravitreal pegaptanib (0.3 mg, 1 mg, 3 mg) administered at study entry, week 6, and week 12, with additional injections and/or focal photocoagulation as needed during the ensuing 18 weeks, up to a maximum of 6 pegaptanib/sham therapies, were evaluated. Scatter panretinal photocoagulation before study enrollment was permitted, but not within 6 months of randomization and study entry. Changes in retinal neovascularization were assessed on fundus photographs and fluorescein angiograms graded at a reading center in a masked fashion.

RESULTS

Of 172 participants, 19 had retinal neovascularization in the study eye at baseline. Excluding 1 who had scatter photocoagulation 13 days before randomization and 2 with no follow-up photographs, 1 of the remaining 16 subjects had panretinal photocoagulation during study follow-up. Of these 16 subjects, 8 of 13 (62%) in a pegaptanib treatment group (including the one receiving panretinal photocoagulation), 0 of 3 in the sham group, and 0 of 4 fellow (nonstudy) eyes showed either regression of neovascularization on fundus photographs or regression or absence of fluorescein leakage from neovascularization (or both) at 36 weeks. In 3 of 8 with regression, neovascularization progressed at week 52 after cessation of pegaptanib at week 30.

CONCLUSIONS

Most subjects with retinal neovascularization at baseline assigned to pegaptanib showed regression of neovascularization by week 36. These findings suggest a direct effect of pegaptanib upon retinal neovascularization in patients with diabetes mellitus.

A phase II randomized double-masked trial of pegaptanib, an anti-vascular endothelial growth factor aptamer, for diabetic macular edema

OBJECTIVE

To evaluate the safety and efficacy of pegaptanib sodium injection (pegaptanib) in the treatment of diabetic macular edema (DME).

DESIGN

Randomized, double-masked, multicenter, dose-ranging, controlled trial.

PARTICIPANTS

Individuals with a best-corrected visual acuity (VA) between 20/50 and 20/320 in the study eye and DME involving the center of the macula for whom the investigator judged photocoagulation could be safely withheld for 16 weeks.

INTERVENTION

Intravitreous pegaptanib (0.3 mg, 1 mg, 3 mg) or sham injections at study entry, week 6, and week 12 with additional injections and/or focal photocoagulation as needed for another 18 weeks. Final assessments were conducted at week 36.

MAIN OUTCOME MEASURES

Best-corrected VA, central retinal thickness at the center point of the central subfield as assessed by optical coherence tomography measurement, and additional therapy with photocoagulation between weeks 12 and 36.

RESULTS

One hundred seventy-two patients appeared balanced for baseline demographic and ocular characteristics. Median VA was better at week 36 with 0.3 mg (20/50), as compared with sham (20/63) (P = 0.04). A larger proportion of those receiving 0.3 mg gained VAs of > or =10 letters (approximately 2 lines) (34% vs. 10%, P = 0.003) and > or =15 letters (18% vs. 7%, P = 0.12). Mean central retinal thickness decreased by 68 microm with 0.3 mg, versus an increase of 4 microm with sham (P = 0.02). Larger proportions of those receiving 0.3 mg had an absolute decrease of both > or =100 microm (42% vs. 16%, P = 0.02) and > or =75 microm (49% vs. 19%, P = 0.008). Photocoagulation was deemed necessary in fewer subjects in each pegaptanib arm (0.3 mg vs. sham, 25% vs. 48%; P = 0.04). All pegaptanib doses were well tolerated. Endophthalmitis occurred in 1 of 652 injections (0.15%/injection; i.e., 1/130 [0.8%] pegaptanib subjects) and was not associated with severe visual loss.

CONCLUSIONS

In this phase II trial, subjects assigned to pegaptanib had better VA outcomes, were more likely to show reduction in central retinal thickness, and were deemed less likely to need additional therapy with photocoagulation at follow-up.

The role of vascular endothelial growth factor in ocular health and disease

The leading causes of blindness are retinal and choroidal diseases manifesting abnormal vessel permeability and growth. Scientists have sought to understand the mechanisms underlying these pathologic conditions with the hope of developing directed and effective pharmacologic therapies. Research has yielded important new mechanistic data, making possible the development of new drugs. One of the most important targets to have emerged is a secreted protein named vascular endothelial growth factor. This review will summarize the current state of our knowledge regarding this growth factor and outline some important questions that remain to be answered.

Pegaptanib for neovascular age-related macular degeneration

BACKGROUND

Pegaptanib, an anti-vascular endothelial growth factor therapy, was evaluated in the treatment of neovascular age-related macular degeneration.

METHODS

We conducted two concurrent, prospective, randomized, double-blind, multicenter, dose-ranging, controlled clinical trials using broad entry criteria. Intravitreous injection into one eye per patient of pegaptanib (at a dose of 0.3 mg, 1.0 mg, or 3.0 mg) or sham injections were administered every 6 weeks over a period of 48 weeks. The primary end point was the proportion of patients who had lost fewer than 15 letters of visual acuity at 54 weeks.

RESULTS

In the combined analysis of the primary end point (for a total of 1186 patients), efficacy was demonstrated, without a dose-response relationship, for all three doses of pegaptanib (P<0.001 for the comparison of 0.3 mg with sham injection; P<0.001 for the comparison of 1.0 mg with sham injection; and P=0.03 for the comparison of 3.0 mg with sham injection). In the group given pegaptanib at 0.3 mg, 70 percent of patients lost fewer than 15 letters of visual acuity, as compared with 55 percent among the controls (P<0.001). The risk of severe loss of visual acuity (loss of 30 letters or more) was reduced from 22 percent in the sham-injection group to 10 percent in the group receiving 0.3 mg of pegaptanib (P<0.001). More patients receiving pegaptanib (0.3 mg), as compared with sham injection, maintained their visual acuity or gained acuity (33 percent vs. 23 percent; P=0.003). As early as six weeks after beginning therapy with the study drug, and at all subsequent points, the mean visual acuity among patients receiving 0.3 mg of pegaptanib was better than in those receiving sham injections (P<0.002). Among the adverse events that occurred, endophthalmitis (in 1.3 percent of patients), traumatic injury to the lens (in 0.7 percent), and retinal detachment (in 0.6 percent) were the most serious and required vigilance. These events were associated with a severe loss of visual acuity in 0.1 percent of patients.

CONCLUSIONS

Pegaptanib appears to be an effective therapy for neovascular age-related macular degeneration. Its long-term safety is not known.

Insulin-like growth factor-I plays a pathogenetic role in diabetic retinopathy

Diabetic retinopathy is a leading cause of blindness in the Western world. Aberrant intercellular adhesion molecule-1 expression and leukocyte adhesion have been implicated in its pathogenesis, raising the possibility of an underlying chronic inflammatory mechanism. In the current study, the role of insulin-like growth factor (IGF)-I in these processes was investigated. We found that systemic inhibition of IGF-I signaling with a receptor-neutralizing antibody, or with inhibitors of PI-3 kinase (PI-3K), c-Jun kinase (JNK), or Akt, suppressed retinal Akt, JNK, HIF-1alpha, nuclear factor (NF)-kappaB, and AP-1 activity, vascular endothelial growth factor (VEGF) expression, as well as intercellular adhesion molecule-1 levels, leukostasis, and blood-retinal barrier breakdown, in a relevant animal model. Intravitreous administration of IGF-I increased retinal Akt, JNK, HIF-1alpha, NF-kappaB, and AP-1 activity, and VEGF levels. IGF-I stimulated VEGF promoter activity in vitro, mainly via HIF-1alpha, and secondarily via NF-kappaB and AP-1. In conclusion, IGF-I participates in the pathophysiology of diabetic retinopathy by inducing retinal VEGF expression via PI-3K/Akt, HIF-1alpha, NF-kappaB, and secondarily, JNK/AP-1 activation. Taken together, these in vitro and in vivo signaling studies thus identify potential targets for pharmacological intervention to preserve vision in patients with diabetes.

A central role for inflammation in the pathogenesis of diabetic retinopathy

Diabetic retinopathy is a leading cause of adult vision loss and blindness. Much of the retinal damage that characterizes the disease results from retinal vascular leakage and nonperfusion. Diabetic retinal vascular leakage, capillary nonperfusion, and endothelial cell damage are temporary and spatially associated with retinal leukocyte stasis in early experimental diabetes. Retinal leukostasis increases within days of developing diabetes and correlates with the increased expression of retinal intercellular adhesion molecule-1 (ICAM-1) and CD18. Mice deficient in the genes encoding for the leukocyte adhesion molecules CD18 and ICAM-1 were studied in two models of diabetic retinopathy with respect to the long-term development of retinal vascular lesions. CD18-/- and ICAM-1-/- mice demonstrate significantly fewer adherent leukocytes in the retinal vasculature at 11 and 15 months after induction of diabetes with STZ. This condition is associated with fewer damaged endothelial cells and lesser vascular leakage. Galactosemia of up to 24 months causes pericyte and endothelial cell loss and formation of acellular capillaries. These changes are significantly reduced in CD18- and ICAM-1-deficient mice. Basement membrane thickening of the retinal vessels is increased in long-term galactosemic animals independent of the genetic strain. Here we show that chronic, low-grade subclinical inflammation is responsible for many of the signature vascular lesions of diabetic retinopathy. These data highlight the central and causal role of adherent leukocytes in the pathogenesis of diabetic retinopathy. They also underscore the potential utility of anti-inflammatory treatment in diabetic retinopathy.

VEGF164(165) as the pathological isoform: differential leukocyte and endothelial responses through VEGFR1 and VEGFR2

PURPOSE

Vascular endothelial growth factor (VEGF) induces angiogenesis and vascular permeability and is thought to be operative in several ocular vascular diseases. The VEGF isoforms are highly conserved among species; however, little is known about their differential biological functions in adult tissue. In the current study, the inflammatory potential of two prevalent VEGF isoform splice variants, VEGF(120(121)) and VEGF(164(165)), was studied in the transparent and avascular adult mouse cornea.

METHODS

Controlled-release pellets containing equimolar amounts of VEGF(120) and VEGF(164) were implanted in corneas. The mechanisms underlying this differential response of VEGF isoforms were explored. The response of VEGF in cultured endothelial cells was determined by Western blot analysis. The response of VEGF isoforms in leukocytes was also investigated.

RESULTS

VEGF(164) was found to be significantly more potent at inducing inflammation. In vivo blockade of VEGF receptor (VEGFR)-1 significantly suppressed VEGF(164)-induced corneal inflammation. In vitro, VEGF(165) more potently stimulated intracellular adhesion molecule (ICAM)-1 expression on endothelial cells, an effect that was mediated by VEGFR2. VEGF(164) was also more potent at inducing the chemotaxis of monocytes, an effect that was mediated by VEGFR1. In an immortalized human leukocyte cell line, VEGF(165) was found to induce tyrosine phosphorylation of VEGFR1 more efficiently.

CONCLUSIONS

Taken together, these data identify VEGF(164(165)) as a proinflammatory isoform and identify multiple mechanisms underlying its proinflammatory biology.

Angiogenesis and ophthalmic disease

Ocular angiogenesis is responsible for the majority of irreversible blindness in the developed world [1]. This debilitating complication affects all age groups and characterizes such diverse and widespread diseases as trachoma, retinopathy of prematurity, diabetic retinopathy, neovascular glaucoma and age-related macular degeneration. Although numerous relatively rare conditions also exhibit ocular angiogenesis, the aim of this review will be to briefly summarize our current knowledge regarding the clinical and laboratory findings of the most epidemiologically significant diseases. We will also describe current concepts regarding the pathogenesis of ocular angiogenesis. In this review the term 'neovascularization', which is more prevalent in the ophthalmic literature, will be used to describe the development of pathological new vessels and should be considered synonymous with 'angiogenesis'.

The role of advanced glycation end products in retinal microvascular leukostasis

PURPOSE

A critical event in the pathogenesis of diabetic retinopathy is the inappropriate adherence of leukocytes to the retinal capillaries. Advanced glycation end-products (AGEs) are known to play a role in chronic inflammatory processes, and the authors postulated that these adducts may play a role in promoting pathogenic increases in proinflammatory pathways within the retinal microvasculature.

METHODS

Retinal microvascular endothelial cells (RMECs) were treated with glycoaldehyde-modified albumin (AGE-Alb) or unmodified albumin (Alb). NFkappaB DNA binding was measured by electromobility shift assay (EMSA) and quantified with an ELISA: In addition, the effect of AGEs on leukocyte adhesion to endothelial cell monolayers was investigated. Further studies were performed in an attempt to confirm that this was AGE-induced adhesion by co-incubation of AGE-treated cells with soluble receptor for AGE (sRAGE). Parallel in vivo studies of nondiabetic mice assessed the effect of intraperitoneal delivery of AGE-Alb on ICAM-1 mRNA expression, NFkappaB DNA-binding activity, leukostasis, and blood-retinal barrier breakdown.

RESULTS

Treatment with AGE-Alb significantly enhanced the DNA-binding activity of NFkappaB (P = 0.0045) in retinal endothelial cells (RMECs) and increased the adhesion of leukocytes to RMEC monolayers (P = 0.04). The latter was significantly reduced by co-incubation with sRAGE (P < 0.01). Mice infused with AGE-Alb demonstrated a 1.8-fold increase in ICAM-1 mRNA when compared with control animals (P < 0.001, n = 20) as early as 48 hours, and this response remained for 7 days of treatment. Quantification of retinal NFkappaB demonstrated a threefold increase with AGE-Alb infusion in comparison to control levels (AGE Alb versus Alb, 0.23 vs. 0.076, P < 0.001, n = 10 mice). AGE-Alb treatment of mice also caused a significant increase in leukostasis in the retina (AGE-Alb versus Alb, 6.89 vs. 2.53, n = 12, P < 0.05) and a statistically significant increase in breakdown of the blood-retinal barrier (AGE Alb versus Alb, 8.2 vs. 1.6 n = 10, P < 0.001).

CONCLUSIONS

AGEs caused upregulation of NFkappaB in the retinal microvascular endothelium and an AGE-specific increase in leukocyte adhesion in vitro was also observed. In addition, increased leukocyte adherence in vivo was demonstrated that was accompanied by blood-retinal barrier dysfunction. These findings add further evidence to the thinking that AGEs may play an important role in the pathogenesis of diabetic retinopathy.

VEGF164-mediated inflammation is required for pathological, but not physiological, ischemia-induced retinal neovascularization

Hypoxia-induced VEGF governs both physiological retinal vascular development and pathological retinal neovascularization. In the current paper, the mechanisms of physiological and pathological neovascularization are compared and contrasted. During pathological neovascularization, both the absolute and relative expression levels for VEGF164 increased to a greater degree than during physiological neovascularization. Furthermore, extensive leukocyte adhesion was observed at the leading edge of pathological, but not physiological, neovascularization. When a VEGF164-specific neutralizing aptamer was administered, it potently suppressed the leukocyte adhesion and pathological neovascularization, whereas it had little or no effect on physiological neovascularization. In parallel experiments, genetically altered VEGF164-deficient (VEGF120/188) mice exhibited no difference in physiological neovascularization when compared with wild-type (VEGF+/+) controls. In contrast, administration of a VEGFR-1/Fc fusion protein, which blocks all VEGF isoforms, led to significant suppression of both pathological and physiological neovascularization. In addition, the targeted inactivation of monocyte lineage cells with clodronate-liposomes led to the suppression of pathological neovascularization. Conversely, the blockade of T lymphocyte-mediated immune responses with an anti-CD2 antibody exacerbated pathological neovascularization. These data highlight important molecular and cellular differences between physiological and pathological retinal neovascularization. During pathological neovascularization, VEGF164 selectively induces inflammation and cellular immunity. These processes provide positive and negative angiogenic regulation, respectively. Together, new therapeutic approaches for selectively targeting pathological, but not physiological, retinal neovascularization are outlined.

Platelets accumulate in the diabetic retinal vasculature following endothelial death and suppress blood-retinal barrier breakdown

Platelet microthrombi are present in the diabetic retinal vasculature of humans and rodents; however, the mechanisms and consequences of their presence have not been defined. The current study demonstrates that platelet containing microthrombi accumulate in the retinal vasculature of the rat within 2 weeks of experimental diabetes, a timepoint at which leukocyte-mediated endothelial cell injury and death are known to occur. Platelet accumulation increased with the duration of diabetes, and crossover experiments revealed that maximal platelet accumulation required both diabetic platelets and a diabetic endothelium. Platelet accumulation also coincided with the expression of Fas and FasL in the diabetic retina. When endothelial cell apoptosis was inhibited with an anti-FasL neutralizing antibody, platelet accumulation was effectively suppressed. When platelets were depleted from the systemic circulation with an anti-platelet antibody, blood-retinal barrier breakdown worsened in the diabetic animals. These findings suggest that platelet accumulation in the diabetic retinal vasculature is secondary to endothelial cell death and serves, in part, to suppress blood-retinal barrier breakdown.

Inhibition of corneal neovascularization by genetic ablation of CCR2

PURPOSE

To determine if genetic ablation of the chemokine receptor CCR2 (involved in leukocyte and endothelial chemotaxis) inhibits the development of corneal neovascularization.

METHODS

Wild-type C57BL/6J mice, as well as species-specific counterparts with targeted homozygous disruption of the CCR2, underwent chemical and mechanical denudation of corneal and limbal epithelium. Corneas were harvested 2 weeks after injury. Neovascularization was quantified by CD31 immunostaining.

RESULTS

The mean percentages of neovascularized corneal area in control mice and CCR2-deficient mice 2 weeks after denudation were 58.3% and 38.8% (P = 0.047), respectively.

CONCLUSIONS

Development of corneal neovascularization is inhibited in CCR2-deficient mice.

Targeted disruption of the CD18 or ICAM-1 gene inhibits choroidal neovascularization

PURPOSE

To investigate the role of the leukocyte adhesion molecules CD18 and intercellular adhesion molecule (ICAM)-1 in the development of choroidal neovascularization (CNV).

METHODS

Laser photocoagulation was used to induce CNV in wild-type C57BL/6J mice and species-specific counterparts with targeted homozygous disruption of the CD18 or ICAM-1 gene. Expression of CD18 and ICAM-1 after laser injury was assessed by immunostaining. CNV responses were compared on the basis of en masse volumetric measurements obtained by confocal microscopy 2 weeks after laser injury and by determination of fluorescein angiographic leakage at 1, 2, and 4 weeks after laser injury.

RESULTS

The site of laser injury showed upregulation of ICAM-1 and invasion by CD18-positive leukocytes within 1 day of laser injury. Significantly fewer lesions exhibited fluorescein leakage defined to be pathologically significant in CD18-deficient mice at weeks 1, 2, and 4 weeks and in ICAM-1-deficient mice at 1 and 4 weeks, compared with the control. There were a significantly greater number of lesions without fluorescein leakage in CD18-deficient mice than in the other two groups at all time points. The volume of CNV in CD18- and ICAM-1-deficient mice was significantly less than in wild type.

CONCLUSIONS

These data suggest a nonredundant role for leukocyte adhesion to vascular endothelium in the development of laser-induced choroidal neovascularization.

Leukocytes mediate retinal vascular remodeling during development and vaso-obliteration in disease

Retinal ischemia can cause vision-threatening pathological neovascularization. The mechanisms of retinal ischemia are not fully understood, however. Here we have shown that leukocytes prune the retinal vasculature during normal development and obliterate it in disease. Beginning at postnatal day 5 (P5) in the normal rat, vascular pruning began centrally and extended peripherally, leaving behind a less dense, smaller-caliber vasculature. The pruning was correlated with retinal vascular expression of intercellular adhesion molecule-1 (ICAM-1) and coincided with an outward-moving wave of adherent leukocytes composed in part of cytotoxic T lymphocytes. The leukocytes adhered to the vasculature through CD18 and remodeled it through Fas ligand (FasL)-mediated endothelial cell apoptosis. In a model of oxygen-induced ischemic retinopathy, this process was exaggerated. Leukocytes used CD18 and FasL to obliterate the retinal vasculature, leaving behind large areas of ischemic retina. In vitro, T lymphocytes isolated from oxygen-exposed neonates induced a FasL-mediated apoptosis of hyperoxygenated endothelial cells. Targeting these pathways may prove useful in the treatment of retinal ischemia, a leading cause of vision loss and blindness.