Antitumor efficacy of dexamethasone-loaded core-crosslinked polymeric micelles.

In the current study, core-crosslinked polymeric micelles (DEX-PMs) loaded with three different DEX derivatives designed to display different drug release kinetics, were evaluated for cancer therapy and compared to another effective nanomedicine formulation (long-circulating liposomes encapsulating dexamethasone, LCL-DEX). Pharmacokinetic studies with both radiolabeled dexamethasone and polymer showed that these polymeric systems have long circulating half-lives and may accumulate at the tumor site to a higher extent than liposomes. The in vitro drug release profiles and circulating drug levels in the blood stream show that DEX-PMs with dexamethasone covalently entrapped via a sulfone ester-containing linker (DMSL2) have prolonged circulation time and intermediate drug release kinetics compared to the other polymeric DEX-releasing systems. Furthermore, as the free dexamethasone circulating levels were similar when administered as DMSL2-PM or LCL-DEX, these systems were evaluated simultaneously for antitumor efficacy in B16F10 melanoma bearing mice. The corticosteroid-targeted systems inhibited tumor growth to a similar extent and both increased survival compared to free drug. Recently antitumor efficacy of targeted formulations has been correlated with a systemic effect: a decrease of white blood cell count. In this study all three polymeric systems, liposomes as well as free drug had similar effects on the number of circulating white blood cells, although white blood cell counts recovered faster in the group receiving free drug. In conclusion, corticosteroid-targeting with a polymeric system or a liposomal system translates in similar therapeutic effects. The proven high versatility of the PM with possible optimization and adjustment of the drug release to that required by the therapeutic application, clearly demonstrates the potential of these systems for the treatment of chronic inflammatory diseases including cancer.