Abstract
Pluronic (Poloxomer) micelles can solubilize cabazitaxel (CTX), a second-generation taxane, and then be subjected to low-temperature "surfactant-stripping" to selectively remove loose and free surfactant, thereby increasing the drug-to-surfactant ratio. We previously found that the addition of certain other co-loaded hydrophobic cargo to the micelles can result in stabilized, surfactant-stripped cabazitaxel (sss-CTX) micelles, which resist drug aggregation in aqueous storage, a common challenge for taxanes. Here, we show that elevated temperatures can accelerate the aggregation of sss-CTX micelles, thereby enabling rapid optimization of formulations with respect to the type and ratio of co-loader used for stabilization. A sss-CTX micelle formulation was developed using mifepristone as the co-loader, at a 60% mass ratio to the CTX. Drug release, hemolysis and complement activation were investigated in vitro. Microtubule stabilization and in vitro cytotoxicity were similar for sss-CTX and a conventional Tween-80 micelle formulation. In vivo pharmacokinetics also revealed similar blood circulation of the two formulations. In subcutaneous Lewis lung carcinoma tumors, as well as in an aggressive mouse model of malignant pleural effusion, sss-CTX showed a similar therapeutic effect as the Tween-80 based formulation. Altogether, these data show that sss-CTX can achieve similar efficacy as conventional Tween-80 formulations, albeit with substantially higher drug-to-surfactant ratio and with capability of extended aqueous storage.