Wet AMD Recurrence Rate in Patients Stable on Three Month Ranibizumab Dosing

In North America, AMD is the leading cause of irreversible vision loss in those over 65 years of age.1 Vascular endothelial growth factor A (VEGF-A) is a potent promoter of angiogenesis and vascular permeability and its role in the pathogenesis of neovascular AMD is well recognized.2,3 The advent of VEGF inhibitors such Ranibizumab (Lucentis; Genentech Inc.) has revolutionized the management of neovascular AMD. Ranibizumab is an intravitreally administered recombinant, humanized, monoclonal antibody antigen-binding fragment (Fab) that neutralizes all known active forms of VEGF-A. In the landmark phase III clinical studies MARINA, and ANCHOR, Ranibizumab injections were administered monthly over the course of 2 years to eyes with subfoveal CNVMs secondary to AMD. Ranibizumab was shown to not only prevent loss of visual acuity (VA) but also improve VA on average in these patients. 4-6

Despite the tremendous benefit of this treatment, the prospect of indefinitely adhering to the monthly treatment schedules of MARINA and ANCHOR has raised ocular and systemic safety concerns as well as convenience and cost issues for patient and physician alike. The identification of alternative dosing strategies capable of reducing the number of required anti-VEGF injections while still achieving favourable visual acuity outcomes has since been a subject of great interest. The current norm in clinical practice with Ranibizumab is to implement an 'initiation phase' followed by an individualized 'maintenance phase' that is modeled after one of two basic approaches: 'treat-and-observe' or 'treat-and-extend'. Both regimens are currently considered within the standard of clinical practice. 'Treat -and-observe' entails treatment and follow-up until the macula is free of exudation, with treatment thereafter only in the presence of recurrent exudation.7 Alternatively, in a treat-and-extend dosing strategy, intervals between treatments are extended as long as the macula remains dry.8 In the 2009 ASRS survey, 56% of physicians reported employing treat-and-observe and 44% reported employing treat-and-extend for their patients with neovascular AMD.9 In a study by Oubraham et al10 it was found that a treat-and-extend dosing regimen may yield greater gains in vision than treat-and-observe, albeit with a greater number of required injections.

In a treat-and-extend dosing strategy, some patients may require frequent monthly injections to stabilize their disease, while others may demonstrate a more stable condition requiring infrequent treatments. Many clinicians who employ a treat-and-extend dosing regimen, do not extend their treatment intervals beyond 3 months. However, it is possible that the subgroup of patients on every three months 'treat-and-extend' dosing may represent a unique, stable population that would perform particularly well on a 'treat-and-observe' regimen.