However the former is of the IgG1 type, the latter of the IgG2 type; consequences on antibody-dependent cellular cytotoxicity can be quite different.[28] Other monoclonals in clinical development are zalutumumab, nimotuzumab, and matuzumab. The monoclonal antibodies block the extracellular ligand binding domain. With the binding site blocked, signal molecules can no longer attach there and activate the tyrosine kinase.