FZD5 and neoplasm: Vantictumab (OMP-18R5) is a mAb that blocks the Fz receptors (such as Fz1, Fz2, Fz5, Fz7, and Fz8) [57] and reduces proliferation of tumor cell and tumor-initiating cell number in tumors of the lung, breast, colon, and pancreas.