Anti-PlGF Inhibits Growth of VEGF(R)-Inhibitor-Resistant Tumors without Affecting Healthy Vessels

Novel antiangiogenic strategies with complementary mechanisms are needed to maximize efficacy and minimize resistance to current angiogenesis inhibitors. We explored the therapeutic potential and mechanisms of αPlGF, an antibody against placental growth factor (PlGF), a VEGF homolog, which regulates the angiogenic switch in disease, but not in health. αPlGF inhibited growth and metastasis of various tumors, including those resistant to VEGF(R) inhibitors (VEGFRIs), and enhanced the efficacy of chemotherapy and VEGFRIs. αPlGF inhibited angiogenesis, lymphangiogenesis, and tumor cell motility. Distinct from VEGFRIs, αPlGF prevented infiltration of angiogenic macrophages and severe tumor hypoxia, and thus, did not switch on the angiogenic rescue program responsible for resistance to VEGFRIs. Moreover, it did not cause or enhance VEGFRI-related side effects. The efficacy and safety of αPlGF, its pleiotropic and complementary mechanism to VEGFRIs, and the negligible induction of an angiogenic rescue program suggest that αPlGF may constitute a novel approach for cancer treatment. © 2007 Elsevier Inc. All rights reserved.