Demetrios Papahadjopoulos

Antibody-Targeted Liposomes: Development of a Cell-Specific Drug Delivery System

We have described the following important parameters for the development of antibody-directed liposomes in drug delivery. (i) Liposome-dependent cytotoxic agents: Drugs such as methotrexate-γ-aspartate which are unable to enter cells without a carrier are essential since their use eliminates the non-specific effects of drug which may leak from the liposomes. (ii) Multivalency of liposome interactions: Liposomes conjugated to antibody have a higher valency than the soluble antibody and can bind to cells with up to 1,000-fold higher affinity constant. (iii) Use of multiple ligands: Liposomes which interact with more than one ligand on the cell surface show marked resistance to inhibition of cell association by soluble ligands. (iv) Optimal liposome size for drug delivery: The optimal liposome size appears to vary from 0.05 to 0.1 µm depending on target cell type.