The tools of biotechnology can be used to engineer molecules that incorporate genes or portions of genes for two proteins. The resulting fusion protein can offer a combination of attributes that enhance its ability to treat disease.
For example, several fusion proteins have been constructed by combining the binding domain of a cell surface receptor with the tail (Fc) portion of an antibody. The receptor portion functions as a decoy binding site to attract and capture molecules that would otherwise contribute to disease. The antibody portion enables the fusion protein to remain in the body much longer than a circulating receptor would last on its own.