Safety and Efficacy of Ranibizumab and Bevacizumab for the Treatment of Neovascular Age-related Macular Degeneration

Abstract

Ocular anti-vascular endothelial growth factor (VEGF) therapy represents a major breakthrough in the treatment of patients with neovascular age-related macular degeneration (nvAMD). The anti-VEGF agents, ranibizumab and bevacizumab, are both widely used in the treatment of nvAMD although bevacizumab has not yet received regulatory approval for intraocular use. Bevacizumab costs considerably less than ranibizumab when administered as an intraocular injection, which has led to widespread use and studies comparing the efficacy and safety of the two drugs. Bevacizumab shares identical pharmacology with ranibizumab although structural differences result in differences in receptor affinity and rates of drug clearance. While estimates of the vitreous half-life of ranibizumab vary, it is shorter than that of bevacizumab. Furthermore, the serum half-life of bevacizumab is about 20 days, more than twice that of ranibizumab and this has led to speculation that it may present a greater risk of systemic adverse effects. Considerable clinical trial evidence exists relating to the efficacy and safety of ranibizumab. The Comparison of age-related macular degeneration treatments trials (CATT) study of the two drugs found efficacy to be equivalent for the as needed versus as needed and monthly versus monthly comparisons. Ranibizumab as needed was equivalent to monthly ranibizumab, though the bevacizumab as needed was not equivalent to monthly bevacizumab. A greater number of serious adverse events (SAEs) occurred with bevacizumab. However, the study was insufficiently powered to identify differences in drug-related adverse events. Intravitreal injection of bevacizumab is associated with a low but significant risk of acute intraocular inflammation, shown to result in significant visual loss in some patients. Finally, there are issues related to fractionating of bevacizumab that has lead to sporadic cases of blindness worldwide. The increased risk for both systemic and ocular adverse events may influence the cost-effectiveness ratio of the two drugs based on health economic models. Further comparative studies and continuous monitoring of safety data are required to examine the incidence of adverse events.