Comparison of bevacizumab, ranibizumab, and pegaptanib in vitro: efficiency and possible additional pathways.

PURPOSE Vascular endothelial growth factor (VEGF) antagonists are the therapy of choice for age-related macular degeneration. Ranibizumab and pegaptanib have been approved by the United States Food and Drug Administration, whereas bevacizumab is used off label. In this study, the authors compare these VEGF inhibitors directly regarding their efficiency to neutralize VEGF in a quantifiable in vitro system. METHODS Porcine retina-retinal pigment epithelium-choroid organ culture and RPE cell culture were prepared from fresh eyes, cultivated in a perfusion chamber, and treated with clinically relevant concentrations of bevacizumab, ranibizumab and pegaptanib. VEGF content of the supernatant was analyzed with ELISA. Additionally, the influence of bevacizumab and ranibizumab on intracellular VEGF was analyzed with Western blot. RESULTS At clinically significant doses, bevacizumab (0.25 mg/mL) and ranibizumab (0.125 mg/mL) neutralized VEGF completely for 6 hours, whereas pegaptanib (0.08 mg/mL) showed no effect. Bevacizumab and ranibizumab neutralized VEGF significantly up to 16 hours. When diluted, bevacizumab lost its inhibiting properties at a concentration of 975 ng/mL, and ranibizumab neutralized VEGF up to a concentration of 120 ng/mL. Both substances significantly diminished VEGF expression in Western blot. CONCLUSIONS At clinical doses, bevacizumab and ranibizumab are equally potent in neutralizing VEGF. To neutralize VEGF completely in this system, a fraction of the clinical dose is needed. Ranibizumab is more efficient at neutralizing VEGF when diluted. Pegaptanib showed no effect in this system, which might help explain the clinical experience regarding this drug. A direct effect of ranibizumab and bevacizumab on VEGF protein expression indicates additional pathways of VEGF inhibitors.