New treatments have not only caused major shifts in practice patterns but have also presented feasible options for pathologies other than those for which they were initially developed.

At the 7th International AMD Congress, held during October 2007 in Marbella, Spain, Neil Bressler, MD discussed how the common features of retina pathologies might lead to treatments not only for neovascular age-related macular degeneration (AMD) today but also for macular oedema (ME) tomorrow.

The treatment of neovascular AMD has changed significantly over the last 25 years. From the original reports in the early 1980s, which showed that laser photocoagulation would work for very selected cases, through to the PDT era, which extended the number of treatable cases, yet still only enabled patients to increase their chance of avoiding vision loss rather than increasing their chance of gaining vision. Research then focused briefly on submacular surgery, but this was rejected after randomized clinical trials found it not to be beneficial. The direction then moved from halting progression of the condition to improving vision with anti-VEGF therapies, specifically ranibizumab, which was shown to improve people's vision about one-third of the time.

"The ANCHOR trial showed us that ranibizumab could not only avoid vision loss in someone with predominantly classic lesions, but there was some resolution of oedema presumably leading to improved retina function as reflected in substantial vision gain in 35-40% of patients. Similarly, the MARINA trial showed substantial vision improvement in a third of people with minimally classic or occult with no classic lesions and recent disease progression," said Dr Bressler. "When we think about the mechanisms by which anti-VEGF agents interfere with neovascularization or permeability to exert these beneficial effects, it makes you wonder whether anti-VEGF drugs have any value in developing a treatment for ME," he added.

Strength in numbers: the Diabetic Retinopathy Clinical Research Network

Dr Bressler explained the role of a US-based network in researching potential avenues of treatment in diabetic retinopathy (DR) and diabetic macular oedema (DME) by implementing multicentre clinical trials.

Initially funded by the National Eye Institute (NEI) in September 2002, the Diabetic Retinopathy Clinical Research Network currently involves over 100 sites, its objective being to develop a collaborative network of specialists that would rapidly facilitate multicentre clinical research. The two main priorities of the network were, firstly, to be broadly inclusive, both community-based practices that were dealing with retina and treated patients with diabetes, as well as university-based centres.

The second priority was to collaborate with industry to facilitate investigations and pursue opportunities with drugs that are available and warrant further investigation for efficacy in DR and DME. "The Network's collaborations with industry are consistent with its dedication to academic integrity; all protocols are transparent and freely available online, and the Network maintains control over scientific design, data, analysis, presentations, and publications.¹ To ensure optimal clinical trial performance, each decision is made based on the best scientific and clinical trial method. The Network has no role relating to the optimum ways of marketing the drug or study," assured Dr Bressler.

"In just a few years, the Network has 12 protocols ongoing, with over 2 100 subjects enrolled in various trials," he added.

He referred specifically to a pilot study, conducted by the Network, evaluating intravitreal bevacizumab for the treatment of DME.²

The bevacizumab test

The purpose of this study was to evaluate the efficacy of anti-VEGF therapy, using bevacizumab as the example, in treating ME compared with photocoagulation therapy.

There were five treatment groups: A) laser photocoagulation at baseline (n=19); B) 1.25 mg bevacizumab at baseline and at week six (n=22); C) 2.5 mg bevacizumab at baseline and at week six (n=24); D) bevacizumab just once, at baseline and a sham injection at week six (n=22); E) a combination of bevacizumab 1.25 mg at baseline and week six, and laser photocoagulation at week three (n=22).