A fully human IgG1 monoclonal antibody directed against human vascular endothelial growth factor receptor 1 (VEGFR-1/FLT-1) with potential antiangiogenesis and antineoplastic activities. Icrucumab specifically binds to and inhibits the activity of VEGFR-1, which may prevent the activation of downstream signaling pathways and so inhibit tumor angiogenesis; the subsequent reduction in tumor nutrient supply may inhibit tumor cell proliferation. Tumor cell overexpression of VEGFR-1 may be associated with tumor angiogenesis and tumor cell proliferation and invasion; VEGFR-1 may modulate VEGFR-2 signaling.