Continuous release of interleukin-2 from liposomal IL-2 (mixture of interleukin-2 and liposomes) after subcutaneous administration to mice

Recombinant interleukin-2 (IL-2) was strongly and almost completely adsorbed onto small and hydrophobic liposomes by simple mixing under optimal conditions (liposome: DSPC-DSPG; molar ratio, 10:1; 30-50 nm in size, ratio of IL-2 to liposome: 4.0 JRU/nmol lipid). This liposomal IL-2 displayed better distribution after intravenous administration in mice and improved therapeutic effect against experimental M5076 metastases, as reported previously.[1] In this study, the elimination of IL-2 from the dosing area was investigated when the liposomal IL-2 was administered to mice subcutaneously. The results suggest that the release of IL-2 from this liposome was continuous and almost complete. The mean residence time (MRT) of IL-2 in the dosing area was 11.0 ± 1.65 hr. This resulted in the 8-fold times enhancement of MRT in the systemic circulation by the presence of liposomes, and IL-2 was detected in the serum for 2 days. Using this liposomal IL-2 is expected to have the potential to decrease the number of injections and enhance the efficacy of IL-2 in immunotherapies and therapies against tumor.