Anti-VEGF antiserum neutralizes VEGF in vivo. The VEGF-neutralizing activity of antiserum was assessed in vivo using a modified version of a standard VEGF-induced angiogenesis assay. Briefly, CHO cells (1 × 10⁵ cells) expressing VEGF were injected into the ears of nude mice. The mice received control serum or anti-VEGF antiserum (0.8 ml) intraperitoneally daily starting at day –1. Marked angiogenesis was evident at days 2–4 in control serum–treated mice. Overall, using this in vivo assay, there was inhibition of ∼80% of VEGF-induced angiogenesis by the antiserum.