Medicinal chemists try to find ways to get drugs to the target cell and organ,
and not to the rest of the body, and to activate the drug only at the target organ, to make
it effective. This can be done with liposomes, synthetic polymers, dendrimers and
nanotechnology. Liposomes prepared from polyethylene glycol (PEG) are used to
deliver the anticancer agent doxorubicin. Another way to deliver drugs to their specific
target is through antibody-drug conjugates and fusion proteins, in which one part (such
as the antibody) binds specifically to the target and the other part is released and has the
desired therapeutic effect. An example of this is the drug called trastuzumab emtansine,
also known as T-DM1. There are also recombinant immunotoxins, in which a fusion
protein is made that contains a bacterial toxin and a fragment which targets the specific
cancer cells being treated. An example is anti-Tac(Fv)-PE38 or LMB-2, which contains
a toxin fragment of Pseudomonas endotoxin and a monoclonal antibody against the cell
surface protein, CD25, in cancer cells. Another example that is in development is
targeted delivery of small inhibitory RNAs (siRNAs).
Keywords: Drug delivery, liposome, dendrimer, polyethylene glycol (PEG),
doxorubicin, trastuzumab emtansine, T-DM1, Bexxar, Zevalin.
