Background: Andrographolide (ADG) isolated from Andrographis paniculata exhibits anti-inflammatory and anticancer activities, but high hydrophobicity and poor bioavailability greatly restricts its clinical application.Objectives: In this study, ADG was encapsulated in a micelle formulation based on poly (D,L-lactide-co-glycolide)-b-poly (ethylene glycol)-b-poly (D,L-lactide-co- glycolide) (PLGA-PEG-PLGA) amphiphilic triblock copolymers, in order to enhance the anticancer efficacy and bioavailability in vivo.Methods: The physicochemical properties of the ADG-loaded PLGA-PEG-PLGA micelles were investigated for encapsulation efficiency, particle size, zeta potential and critical micelle concentration. These micelles were further evaluated for in vitro cytotoxicity, including proliferation inhibition, cell cycle arrest and pro-apoptosis effects against human breast cancer MAD-MB-231 cells, cellular uptake and pharmacokinetics study in rat.Results: ADG-loaded PLGA-PEG-PLGA micelles had a high encapsulation and loading efficiency of about 92 and 8.4% (w/w), respectively, and a stable particle size of 124.3 ± 6.4 nm. In vitro cytotoxicity testing demonstrated that ADG-loaded PLGA-PEG-PLGA micelles exhibited higher proliferation inhibition, cell cycle arrest at the G2/M phase and pro-apoptosis effects in MAD-MB-231 cells, which would be contributed to higher efficiency of cellular uptake and intracellular transport. Further, the plasma AUC(0-∞) and mean resident time of ADG-loaded PLGA-PEG-PLGA micelles were increased by 2.7- and 2.5-fold, respectively, when compared to the raw suspension.Conclusion: All of these investigations suggest that PLGA-PEG-PLGA micelles may be a potential drug delivery strategy for improving ADG bioavailability and efficacy in cancer therapy. © 2014 Informa UK, Ltd.