17-Allyamino-17-demethoxygeldanamycin (17-AAG) is a potent anticancer agent currently undergoing phases I and II clinical trials. However, the clinical development of 17-AAG has been hindered by its poor aqueous solubility and hepatotoxicity. This study aimed to devise novel micellar nanocarriers for 17-AAG that improve its solubility and retain the incorporated drug for a prolonged period of time. We have found that 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000]/D-alpha-tocopheryl polyethylene glycol 1000 (PEG-DSPE/TPGS) mixed micelles (at a 1:2 molar ratio) can deliver 17-AAG at clinically relevant doses. By modulating the concentrations of micelle-forming copolymers, the burst release of 17-AAG from PEG-DSPE/TPGS mixed micelles was substantially reduced with a release half-life up to about 8h. Our (1)H NMR spectroscopy results revealed that the incorporation of TPGS into PEG-DSPE micelles restricted internal molecular motions of copolymers in both the corona and core regions of the micelles, leading to the delayed drug release. Cytotoxicity of 17-AAG formulated in PEG-DSPE/TPGS mixed micelles against human ovarian cancer SKOV-3 cells was comparable to that of free 17-AAG. 17-AAG-loaded PEG-DSPE/TPGS mixed micelles may offer a promising alternative to the current 17-AAG formulations for the treatment of solid tumors.
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