ABSTRACT
The conjugation of therapeutics to water-soluble biomedical polymers increases the aqueous solubility of hydrophobic drugs, prolongs in vivo drug retention time, reduces systemic toxicity, and enhances therapeutic efficacy. Polymer drug conjugates can preferentially accumulate in solid tumor tissues due to the hyperpermeability of tumor blood vessels or the so-called “enhanced permeability and retention effect.” Polymer drug conjugates can also down-regulate or overcome multiple drug resistance. Because of these unique properties, polymer drug conjugates exhibit higher therapeutic efficacy than the corresponding therapeutics alone. Several polymer drug conjugates are currently used in clinical cancer treatment, and more are in the pipeline of clinical development. Contrast-enhanced magnetic resonance imaging (MRI) is effective for noninvasive visualization of the real-time pharmacokinetics and biodistribution of paramagnetically labeled polymer drug conjugates after intravenous administration. MRI has a potential to provide accurate four-dimensional information of in vivo properties of the drug delivery systems.
