Innovative treatments for exudative age-related macular degeneration

Antiangiogenic therapy with anti-vascular endothelial growth factor modalities for neovascular age-related macular degeneration

BACKGROUND

Age-related macular degeneration (AMD) is a common cause of severe vision loss in people 55 years and older.

OBJECTIVES

The objective of this review was to investigate the effects of anti-VEGF (vascular endothelial growth factor) modalities for treating neovascular AMD.

SEARCH STRATEGY

We searched CENTRAL, MEDLINE, EMBASE and LILACS. We handsearched ARVO abstracts for 2006, 2007 for ongoing trials.

SELECTION CRITERIA

We included randomized controlled trials (RCTs).

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data. We contacted trial authors for additional data. We summarized outcomes as relative risks (RR), number needed to treat (NNT) and weighted mean differences.

MAIN RESULTS

We included five RCTs of good methodological quality. All five trials were conducted by pharmaceutical companies. An intention-to-treat analysis using the last observation carried forward method was done in most trials. Two trials compared pegaptanib versus sham. One trial compared ranibizumab versus sham, another compared ranibizumab/sham verteporfin PDT versus verteporfin PDT/sham ranibizumab, and the final trial compared ranibizumab plus verteporfin PDT versus verteporfin PDT alone. Fewer patients treated with pegaptanib lost 15 or more letters of visual acuity at one year follow-up compared to sham (pooled relative risk (RR) 0.71; 95% confidence interval (CI) 0.61 to 0.84). The NNT was 6.67 (95% CI 4.35 to 14.28) for 0.3 mg pegaptanib, 6.25 (95% CI 4.17 to 12.5) for 1 mg pegaptanib and 14.28 (95% CI 6.67 to 100) for 3 mg pegaptanib. In a trial of ranibizumab versus sham, RR for loss of 15 or more letters visual acuity at one year was 0.14 (95% CI 0.1 to 0.22) in favour of ranibizumab. The NNT was 3.13 (95% CI 2.56 to 3.84) for 0.3 mg ranibizumab and 3.13 (95% CI 2.56 to 3.84) for 0.5 mg ranibizumab. In a trial of ranibizumab versus verteporfin PDT, RR for loss of 15 or more letters at one year was 0.13 (95% CI 0.07 to 0.23) favouring ranibizumab. The NNT was 3.33 (95% CI 2.56 to 4.76) for 0.3 mg ranibizumab and 3.12 (95% CI 2.43 to 4.17) for 0.5 mg ranibizumab. In another trial of combined ranibizumab plus verteporfin PDT versus verteporfin PDT, RR for loss of 15 or more letters at one year favoured combined therapy (RR 0.3 (95% CI 0.15 to 0.60). The NNT was 4.35 (95% CI 2.78 to 11.11). Pooled RR for gain of 15 or more letters visual acuity at one year was 5.81 (95% CI 3.29 to 10.26) for ranibizumab versus sham, 6.79 (95% CI 3.41 to 13.54) for ranibizumab/sham verteporfin PDT versus verteporfin PDT/sham ranibizumab, and 4.44 (95% CI 1.40 to 14.08) for ranibizumab plus verteporfin PDT versus verteporfin PDT. Frequency of endophthalmitis in included studies was between 0.7% to 4.7% with ranibizumab and 1.3% with pegaptanib. Improvement in vision-specific quality of life was reported for both treatments.

AUTHORS' CONCLUSIONS

Pegaptanib and ranibizumab reduce the risk of visual acuity loss in patients with neovascular AMD. Ranibizumab causes gains in visual acuity in many eyes. Quality of life and cost will be important for treatment decisions. Other agents blocking VEGF are being tested in ongoing trials.

Is significant relevant? Validity and patient benefit of randomized controlled clinical trials on age-related macular degeneration

A large variety of new treatment options for different forms of age-related macular degeneration (ARMD) are becoming available. Not all new therapies may meet the expectations of patients and ophthalmologists. Despite the given statistical significant priority of treatment investigations, the endpoints may not be relevant to the patient's requirements. Therefore, questions inevitably arise regarding patient's benefit and the validity of the randomized controlled trials. The randomized controlled trial is regarded as the "gold standard" in terms of evaluating the effectiveness of interventions. The external validity of randomized controlled trials may be compromised, if, for example, patients assigned to the study group are unrepresentative of the reference population. This review aims to analyze problems with external validity in the randomized controlled trials on ARMD and surveys the endpoints of clinical studies with respect to the patient benefit.

Pegaptanib: in exudative age-related macular degeneration

Pegaptanib, an aptamer, is an antagonist of vascular endothelial growth factor that has shown efficacy in the treatment of patients with exudative age-related macular degeneration (AMD). In two randomised, double-masked trials in patients with exudative AMD (n=1208), the proportion of responders (those losing <15 letters of visual acuity) at 54 weeks was significantly higher in intravitreous pegaptanib 0.3 mg recipients than in those receiving sham injections (70% vs 55%; p<0.001). These trials were conducted concurrently and analysed as a single study; the treatments were given every 6 weeks for 48 weeks. The improvement in visual acuity with pegaptanib was maintained in a 1-year extension of these trials. Similar favourable results with pegaptanib 0.3 mg were seen in terms of the secondary efficacy endpoints (e.g. proportion of patients experiencing severe loss of visual acuity or legal blindness in the study eye). These vision-improving effects of pegaptanib were associated with beneficial angiographic effects. Intravitreous pegaptanib 0.3-3 mg was well tolerated with most ocular adverse events being mild-to-moderate and transient. Serious injection-related adverse events occurred in <or=1.3% of patients treated with pegaptanib. There were no systemic adverse events that could be definitely attributed to pegaptanib.

Photoreceptor cells from mouse ES cells by co-culture with chick embryonic retina

Degeneration of photoreceptors is a consistent and common endpoint in retinal diseases. Herein, we report the efficient induction of photoreceptor-like cells from mouse embryonic stem (ES) cells using chick embryonic retina tissue. Undifferentiated mouse ES cells were initially cultured in a preferential condition into a neural lineage, and ES cells were then co-cultured with chick embryonic day 6 (E6) retina tissues. After a 10-day co-culture, approximately 20% of the mouse ES derivatives became immuno-positive for rhodopsin. RT-PCR analysis demonstrated expression of the transcription factor crx and a distinct increase of rod photoreceptor-specific markers, IRBP and recoverin, after the start of the co-culture. These results indicate that co-culture of ES cells with chick embryonic retina tissue is a useful and efficient method for the induction of photoreceptor-like cells.