This is an anti-DLL4/VEGF bispecific antibody designed to inhibit both Delta-like ligand 4 (DLL4) in the Notch cancer stem cell pathway as well as vascular endothelial growth factor (VEGF) and thereby induce potent anti-tumor responses while mitigating certain angiogenic-related toxicities. Since DLL4 is cell-bound, the agent can localize to the tumor microenvironment to block DLL4 and sequester VEGF that is locally secreted. The anti-DLL4 moiety of navicixizumab specifically binds to DLL4, prevents its interaction with Notch receptors, and inhibits Notch-mediated signaling and gene transcription, which may both block tumor angiogenesis and inhibit tumor cell growth. The anti-VEGF moiety binds to VEGF and prevents the binding of VEGF to its receptor, which blocks VEGF-mediated signaling and further inhibits the growth and maintenance of tumor blood vessels.