Dear Editor,

We read the article 'Bevacizumab and ranibizumab tachyphylaxis in the treatment of choroidal neovascularisation' with interest. We congratulate the authors for trying to establish the efficacy of a promising treatment strategy for Tachyphylaxis to Anti-VEGF drugs in Exudative AMD. We agree with the authors that this could be a useful option in patients who develop tachyphylaxis. However, there are some unanswered questions .

Firstly,the total number of Exudative ARMD patients treated with Lucentis or Avastin in the study period was not provided in the article. This would be useful for calculating the incidence of tachyphylaxis, thus providing information on the magnitude of the problem.

Secondly,although 80-81% subjects responded to switching to the alternate Anti-VEGF group, most of these required multiple injections post intervention. Also, at the end of the study period 11 of the 26 treated eyes had persistent exudation and continued to need therapy. Could this be attributed to tachyphylaxis to the second drug after switching? This may be due to either these subjects being predisposed to developing tachyphylaxis or ill sustained effect of the second anti VEGF drug as a response to chronic blockade of signaling mediated by VEGF. All these issues lead us to question the efficiency and feasibility of switching a patient from one anti-VEGF to another.

We also noted a difference in the response to the two anti-VEGFs. The group switched from bevacizumab to ranibizumab therapy subsequently required a higher number of ranibizumab injections with a mean of 7(1-16) versus 2.75 (1-6) bevacizumab injections in the other group. Though this difference may not be significant due to the relatively small size in each group, it is contrary to expectations since ranibizumab has a much higher binding efficacy to VEGF?.

The long term sustenance of positive effect of switching needs to be studied prospectively before recommending it.

References

1.Gasperini JL, Fawzi AA, Khondkaryan A, Lam L, Chong LP, Eliott D, Walsh AC, Hwang J, Sadda SR. Bevacizumab and ranibizumab tachyphylaxis in the treatment of choroidal neovascularisation. Br J Ophthalmol. 2012 Jan:96(1):14-20.

2.Ferrara N, Damico L, Shams N, Lowman H, Kim R. Development of Ranibizumab, An Anti-vascular endothelial growth actor antigen binding fragment, as therapy for neovascular age-related macular degeneration. Retina2006;26 (8):859-870

Conflict of Interest:

None declared