SAFETY OF INTRAVITREAL INJECTION OF BEVACIZUMAB IN RABBIT EYES LEONARD FEINER, MD, PHD,*† EMILY E. BARR, BS,* YING-BO SHUI, PHD,* NANCY M. HOLEKAMP, MD,*† MILAM A. BRANTLEY JR, MD, PHD*† Purpose: To evaluate the safety of intravitreal injection of bevacizumab in rabbits using electrophysiological testing and histopathologic analysis. Methods: New Zealand albino rabbits were injected in one eye with control antibody (n = 2), 0.05 mL of bevacizumab (n = 3), or 0.2 mL of bevacizumab (n = 3). Electroreti- nograms were obtained 1 week and 4 weeks after injection. Histologic analysis was performed after completion of the electroretinographic studies. Results: No statistical differences were seen in scotopic and photopic a- and b-wave amplitudes between untreated control and bevacizumab-injected eyes. No histopathologic differences were identified between untreated control and bevacizumab-injected eyes. Conclusion: Our study did not find evidence of retinal toxicity from a single intravitreal injection of bevacizumab in rabbits. RETINA 26:882– 888, 2006 I n 1989, two laboratories independently identified a protein that increased capillary permeability and functioned as an endothelial cell mitogen. 1,2 This pro- tein, vascular endothelial growth factor (VEGF), plays a critical role in both adult and developmental blood vessel growth. Because VEGF is such a crucial regu- lator of angiogenesis, it has become an attractive tar- get for pharmacologic manipulation to treat cancers and ophthalmic diseases. The role of VEGF in retinal vascular disease has been well established. In diabetic retinopathy and branch and central vein occlusions, elevations of vit- reous levels of VEGF correlate with the severity of proliferative retinopathy. 3,4 Anterior segment neovas- cularization has likewise been correlated with aqueous humor concentrations of VEGF. 5 VEGF inhibition has been shown to blunt or eliminate neovascularization in experimental models of proliferative retinopathy. 6 The role of VEGF in choroidal neovascularization is less clear. VEGF expression has been demonstrated in excised subfoveal choroidal neovascular mem- branes, but VEGF expression is diffuse and can be found in many control tissues. 7,8 Perhaps the best evidence that VEGF plays a critical role in choroidal neovascular membrane formation is that treatment of patients with medications that block VEGF signaling has been shown to improve the clinical course of exudative age-related macular degeneration (AMD). Intravitreally injected ranibizumab (Lucentis; Genen- tech, Inc.), an Fab fragment directed to VEGF, has been shown to prevent vision loss in a significant number of patients with exudative AMD in phase 3 clinical trials. 9 Bevacizumab (Avastin; Genentech, Inc.), a full- length humanized monoclonal IgG antibody that binds to VEGF, was approved by the US Federal Drug Administration in 2004 for the treatment of metastatic From the *Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri; and the †Barnes Retina Institute, St. Louis, Missouri. Supported by the Heed Foundation (L.F.), the Retina Research and Development Foundation, and Research to Prevent Blindness, Inc. (Washington University Ophthalmology and Visual Sciences). None of the authors has financial interest in this study. Reprint requests: Milam A. Brantley, Jr., Department of Oph- thalmology and Visual Sciences/Campus Box 8096, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110; e-mail: Brantley@vision.wustl.edu 882