Abstract
Epothilones are microtubule inhibitors that are promising alternatives to paclitaxel due to enhanced anticancer efficacy. While epothilones are slightly more water soluble than paclitaxel and more active against paclitaxel-resistant cells, they still require formulation with Cremophor EL and/or cosolvents and drug resistance still limits therapeutic efficacy. In this report, we showed that the combinational treatment of epothilone B (EpoB), 17-N-allylamino-17-demethoxygeldanamycin (17-AAG, Hsp90 inhibitor), and rapamycin (mTOR inhibitor) displays strong anticancer activity in vitro and in vivo. To address the poor water solubility of this 3 drug-combination, they were co-loaded into poly(ethylene glycol)-block-poly(d,l-lactic acid) (PEG-b-PLA) micelles, and the 3-in-1 loaded PEG-b-PLA micelle (m-EAR) was characterized in terms of drug loading efficiency, particle size, release kinetics. The m-EAR achieved high levels of all three drugs in water; formed micelles with hydrodynamic diameters at ca. 30nm and released the drugs in a sustained manner in vitro at rates slower than individually loaded PEG-b-PLA micelles. In A549-derived xenograft mice, m-EAR (2.0, 15.0, and 7.5mg/kg) caused tumor regression after four weekly injections, whereas EpoB alone (2.0mg/kg) was the same as control. No severe changes in body weight relative to PBS control were observed, attesting to the safety of m-EAR. Collectively, these results suggest that m-EAR provides a simple, but effective and safe EpoB-based combination nanomedicine for cancer therapy.