Interleukin-2 lipid microspheres. II.In vitroandin Vivoassessment of a colloidal drug carrier containing interleukin-2

Abstract

AbstractModifying the tissue distribution and disposition of intravenously administered interleukin-2 (IL2) is desirable for the reduction of its clinical toxicity. In this report, the feasibility of employing lipid microspheres (LMS) was studied for the delivery of IL2. The physical stability of IL2 LMS was monitored after initial preparation and on a monthly basis during storage at 4°C. Appearances and mean particle diameters of IL2 LMS preparations were independent of the type of copolymer surfactant used for emulsification and remained so during refrigerated storage. Retention of IL2 biologic activity after preparation as LMS was assessed in an IL2-dependent cellular bioassay and it was revealed that, in comparison to free IL2, LMS preparations displayed approximately fourfold lower bioactivities. From in vivo tissue distribution studies, total radioactivity recovery following administration of an 125I-IL2 solution was 31% compared to 50–84% for block copolymer stabilized 125I-IL2 LMS (P < 0.001), sug...