PEG-Farnesyl Thiosalicylic Acid Telodendrimer Micelles as an Improved Formulation for Targeted Delivery of Paclitaxel

We have recently designed and developed a dual-functional drug carrier that is based on poly(ethylene glycol) (PEG)-derivatized farnesylthiosalicylate (FTS, a nontoxic Ras antagonist). PEG(5K)-FTS2 readily form micelles (20-30 nm) and hydrophobic drugs such as paclitaxel (PTX) could be effectively loaded into these micelles. PTX formulated in PEG(5K)-FTS2 micelles showed an antitumor activity that was more efficacious than Taxol in a syngeneic mouse model of breast cancer (4T1.2). In order to further improve our PEG-FTS micellar system, four PEG-FTS conjugates were developed that vary in the molecular weight of PEG (PEG(2K) vs PEG(5K)) and the molar ratio of PEG/FTS (1/2 vs 1/4) in the conjugates. These conjugates were characterized including CMC, drug loading capacity, stability, and their efficacy in delivery of anticancer drug PTX to tumor cells in vitro and in vivo. Our data showed that the conjugates with four FTS molecules were more effective than the conjugates with two molecules of FTS and that FTS conjugates with PEG(5K) were more effective than the counterparts with PEG(2K) in forming stable mixed micelles. PTX formulated in PEG(5K)-FTS4 micelles was the most effective formulation in inhibiting the tumor growth in vivo.