ABSTRACT
In the development of novel anticancer drugs including molecular targeting and antibody drugs, unexpected withdraw has been often encountered during phase trials (Kerbel and Folkman 2002). Although these drugs signicantly suppressed tumor growth in certain preclinical models, most of them failed to produce signicant therapeutic results or demonstrated serious side effects in the human subjects tested. These failed drugs frequently showed fast clearance in the blood or irreversible damage to organs by single or repeated injection. Considering these failures, it is desirable to stringently control the process at the action site for maximizing the positive effects and reducing the side effects of the drugs. However, the control of absorption, distribution, metabolism, and excretion (ADME) of a drug is not so easy depending on its own molecular properties. To overcome these problems, nanocarriers such as liposomes, polymeric micelles, and lipid microspheres have been used as systems for controlling drug delivery. The advantages of using nanocarriers for the desired therapeutics are the following: (1) reduction in nonspecic or undesirable biodistribution of a drug, (2) protection from undesirable metabolism and degradation, (3) enhancement of bioavailability by controlled release, (4) selective delivery to the target tissues, etc. It can be considered that therapeutic effect owing to these advantages is signicant.
