Abstract: The invention relates to engineered antibodies which specifically bind to integrin receptors, especially the alpha V integrin receptor subunit. The antibodies comprise the antigen binding sites (CDRs) of a known mouse anti-integrin antibody, as well as hybrid light chain variable sequences, mutated heavy chain variable sequences (Frs) and modified heavy chain constant sequences. The novel antibodies have improved immunogenic and expression properties and elicit excellent anti-angiogenic as well as anti-tumor activities in humans in monotherapy but also and above all in combination with other angiogenesis and tumor inhibiting agents.