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Angiogenesis inhibition therapy for AMD still under discussion in Asia
The swift and widespread uptake of anti-VEGF therapy for age-related macular degeneration in clinical practice has broad implications, many of which are highlighted in the cover story in this issue.
Despite its efficacy, which is now generally considered indisputable, safety, cost and optimal dosing schedule of anti-VEGF therapy have all been widely debated. Our major concern, however, is the accessibility of this sight-saving treatment in Asia. Even in developed countries, there are signs that the health care systems are struggling to keep up with the demand.
With unceasing population growth and aging demographics in developing countries such as China and India, it is difficult to imagine how the health care systems in these countries can face further headwinds. An estimated 1.68 million patients have neovascular AMD in China. At present, only photodynamic therapy with verteporfin is approved as a treatment for neovascular AMD there. This is possibly related to the substantial cost of providing anti-VEGF therapy for all these patients, which will likely add unsustainable stress to the finite resources of the current health care system. Ultimately, patients may suffer and be deprived of the benefits of this new treatment unless new public health initiatives are put in place promptly in these countries.
Studies
Another obvious, but often neglected, issue for the use of ocular anti-VEGF therapy in Asia is that most landmark randomized controlled trials of ocular anti-VEGF therapy for neovascular AMD were conducted in Caucasian populations. It is widely used in Asians based on the assumption that we can expect similar therapeutic effects. Nevertheless, Asian patients are more likely to develop polypoidal choroidal vasculopathy, a variant of neovascular AMD, and hence, they often respond poorly to anti-VEGF therapy alone and require other treatments such as photodynamic therapy. With close to 1 million patients in China with polypoidal choroidal vasculopathy, management of these patients has to rely on data mostly from uncontrolled studies.
This situation underlines the need for future trials of anti-VEGF therapy to include Asian populations. It is encouraging to see that the VIEW trials for VEGF Trap-Eye (aflibercept, Regeneron/Bayer HealthCare), also known as Eylea, have already recognized such a need and enrolled a subset (10%) of Asian patients in their trials. While the trials showed that VEGF Trap-Eye and ranibizumab injections might have equivalent efficacy, it remains unclear whether bevacizumab injections, used almost exclusively in some Asian countries, are comparable to these treatments in Asians.
Challenges
Undoubtedly, angiogenesis inhibition therapy for AMD has saved sight for millions worldwide. There is now evidence suggesting that the declining trends of blindness witnessed in developed countries in recent years could be attributed to this new therapy.
Nevertheless, it remains to be determined whether such public health success can be expected in Asia. The dynamic landscape of the constantly evolving medical and socioeconomic issues suggests that there could be significant challenges ahead. Although none of these challenges are insurmountable, expectations must be realistic. It will take more time before we can see the positive impact of anti-VEGF therapy at full stretch in Asia.
References:
Cheung N, Wong TY. Changing trends of blindness: the initial harvest from translational public health and clinical research in ophthalmology. Am J Ophthalmol. 2012;153:193-195.
Harvey KJ, Day RO, Campbell WG, Lipworth W. Saving money on the PBS: ranibizumab or bevacizumab for neovascular macular degeneration? Med J Aust. 2011;194:567-568.
Kawasaki R, Yasuda M, Song SJ, et al. The prevalence of age-related macular degeneration in Asians: a systematic review and meta-analysis. Ophthalmology. 2010;117:921-927.
For more information:
Dennis S.C. Lam, MD, FRCOphth, can be reached at the Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, 3/F, Hong Kong Eye Hospital, 147K Argyle Street, Kowloon, Hong Kong; email: dennislam_pub@cuhk.edu.hk.
Disclosures: Prof. Lam, Dr. Cheung and Dr. Liu have no relevant financial disclosures.