A humanized recombinant monoclonal antibody directed against the extracellular dimerization domain of the HER-2 tyrosine kinase receptor. Binding of the antibody to the dimerization domain of the HER-2 tyrosine kinase receptor protein directly inhibits the ability of the HER-2 tyrosine kinase receptor protein (the most common pairing partner) to dimerize with other HER tyrosine kinase receptor proteins; inhibiting receptor protein dimerization prevents the activation of HER signaling pathways, resulting in tumor cell apoptosis. (NCI04)