Enhanced antitumor activity of different double arms polyethyleneglycol-modified liposomal doxorubicin.

The effect of polyethyleneglycol (PEG)-modified liposome as a drug carrier has been demonstrated clinically. We designed and synthesized a novel PEG-lipid, 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-PEG (different double arms PEG, DDA-PEG) which had two PEG chains of 500 and 2000 in one molecule to develop more useful PEG-modified liposome. DDA-PEG-modified liposomal doxorubicin (DDA-LDOX(7.5)) had the biggest fixed aqueous layer thickness (FALT) compared with other PEG-lipid-modified liposomes even if the added amount was a few. It was thought that FALT was the indication of blood circulation time. In DOX uptake in tumor cells, DDA-LDOX(7.5) group increased the DOX concentration in tumor cells because it had contact ability with tumor cells. Hence, DDA-LDOX(7.5) which has long circulation time in the bloodstream and contact ability with tumor cells, also had a strong antitumor effect on mice bearing M5076 ovarian sarcoma cells which were DOX low sensitive cells according to the expression of multidrug resistance protein. Furthermore, this liposome maintained a high DOX concentration in a tumor for a long time. These results indicated that the useful antitumor effect of DDA-LDOX(7.5) against M5076 ovarian sarcoma cells is a promising DDS carrier for therapies against drug resistant tumors.