Abstract 2155: Achieving complete response to locoregional disease without toxicity using temperature-sensitive liposomes and ultrasound-mediated hyperthermia.

Abstract

Abstract By stabilizing doxorubicin within temperature-sensitive liposomes and repeating delivery twice per week for four weeks, extended survival and complete response were obtained in syngeneic murine breast tumors. Further, with the stabilized formulation, cardiac toxicity and leukopenia were not detected. Liposomes composed of DPPC:MPPC:DSPE-PEG2k, 86:10:4 were prepared in the presence of copper(II) gluconate and triethanolamine and extruded with 100 nm membrane filters. Cu-liposomes were loaded with Dox at 0.2 mg-drug/mg-lipid with 100% loading. We studied the efficacy of CuDox liposomes (CuDox-LTSLs) using the highly invasive neu deletion (NDL) tumor. Treatment began when the tumor diameter reached 4 mm. The fluorescence of circulating doxorubicin in blood was quenched after the digestion of liposomes with Triton X-100, indicating that the circulating drug remained associated with copper. Dox fluorescence was restored upon reducing the pH using a citrate-saline buffer. Over the 28 days of the study, CuDox-LTSLs were administrated intravenously two times per week at a therapeutic level of 6 mg-drug/kg-body weight. The entire tumor was insonified with a peak ultrasound pressure of 1.1 MPa at a frequency of 1.5 MHz at 42°C for 5 min prior to and 20 min post drug injection. A total of 30 mice were studied, including groups spanning drug treatment with ultrasound, ultrasound, drug treatment and no treatment. Although a single dose administration of CuDox-LTSLs combined with insonation of the entire tumor suppressed the tumor growth, complete response was achieved only upon repeated treatment over a period of 28 days. At 30 days after the last administered dose, none of the mice from the other groups survive; however, 100% of mice treated with ultrasound combined with CuDox-LTSLs survive and the remaining tumor is undetectable. In conclusion, repeated treatment of stabilized temperature sensitive doxorubicin liposomes is highly effective in the treatment of aggressive murine tumors. Acknowledgement: NIHR01CA134659 and NIHR01CA103828 Citation Format: Azadeh Kheirolomoom, Chun-Yen Lai, Sarah M. TAM, Lisa M. Even, Elizabeth S. Ingham, Brett Z. Fite, Katherine D. Watson, Katherine W. Ferrara. Achieving complete response to locoregional disease without toxicity using temperature-sensitive liposomes and ultrasound-mediated hyperthermia. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2155. doi:10.1158/1538-7445.AM2013-2155