Abstract: Lyophilized temsirolimus-loaded liposomes were prepared; the formulations were optimized; and the pharmacokinetics in rats was investigated. The lyophilized temsirolimus-loaded liposomes were prepared by film dispersion, followed by freeze drying. Formulations were optimized by single-factor design. The optimized formulation contained 24 mg/mL phosphatidyl choline(PC), a weight ratio of 1 ∶40 between drug loading and PC, and a weight ratio of 10 ∶1 between PC and cholersterol. Sucrose was determined as an optimal lyoprotectant, and the weight ratio between sucrose and PC was 2 ∶1. The optimized liposomes had a particle size of(100. 8±6. 74)nm and an entrapment efficiency of(95. 24±3. 58)%. Dialytic method was used to investigate the drug release profile. Less than 30% of entrapped drug was released after 24 h at pH 7. 4 under 37 °C. In addition, pharmacokinetics of temsirolimus in rats receiving commercial product Torisel^® and temsirolimus-loaded liposomes was evaluated after HPLC determination of temsirolimus in rat plasma. c_max and AUC of the liposomes were 2. 06- and 1. 49-fold improved relative to that of Torisel^® , respectively. In conclusion, the optimized lyophilized temsirolimus-loaded liposomes with high entrapment efficiency achieved sustained release and significantly increased bioavailability of temsirolimus in rats.