The generality of this approach to antibody–protein conjugation was assessed by generating similar fusions with a human antibody against the HER2/neu receptor, a common breast and ovarian cancer marker and target of the clinically approved antibody drug Herceptin.44 The anti-HER2/neu antibody was tagged with the aldehyde tag at the C terminus then conjugated to hGH and MBP by using the same protocol described for hIgG. Here, ERBB2 is linked to ovarian carcinoma.