The invention provides active agents, such as paclitaxel, rapamycin, or 17-AAG, encapsulated by safe poly(ethylene glycol)-block-poly(lactic acid) (“PEG-b-PLA”) micelles. The compositions provide effective solubilization of drug combinations, such as paclitaxel, rapamycin, and 17-AAG, as well as others described herein. A significant advantage of PEG-b-PLA as a carrier is that it is less toxic than Cremophor® EL or DMSO, which are used in currently known compositions. Additionally, PEG-b-PLA micelles are easier to handle than DMSO and they do not possess a foul odor, which is a problem with formulations currently in clinical trials. Accordingly, the invention provides stable and biocompatible drug formulations that improve bioavailabilty without causing toxicity. It was also found that larger doses of individual drugs in micelle formulations can be administered compared to non-micelle formulations.