Targeting therapeutic molecules to sites of disease

Extract: The holy grail of drug development is to design a magic bullet that will deliver a therapeutic agent only to the site of disease with minimal side effects. This is of great importance in particular when it refers to biological agents such as cytokines that have pleiotropic actions in different tissues. Cytokines are local mediators of cell-to-cell communication. Their expression is transient and they have a short half-life. Therefore, to overcome the pharmacokinetic limitations of cytokines, they are given subcutaneously to reduce side effects. However, by this route they lose their potency. In order to use cytokines for therapeutic purposes they have to be administered frequently at high doses to achieve biologically active concentrations locally at the required sites of a disease.