Depot Characteristics and Biodistribution of Interleukin-2 Liposomes, Importance of Route of Administration

Peter M. Anderson, Emmanuel Katsanis, Susan F. Sencer, Diane Hasz, Augusto C. Ochoa, Bruce Bostrom

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62 Scopus citations


Due to rapid clearance of interleukin-2 (IL-2), it has had limited effective use as an in vivo immunostimulant. Current experimental and clinical protocols generally must utilize large doses, multiple injections, or continuous infusions of IL-2 in order to achieve significant immunostimulation, often at the expense of systemic toxicity. Therefore, the pharmacodynamics of IL-2 liposomes were investigated. IL-2 liposome incorporation efficiency was 80.4% (SD 5.5); vesicle diameter was 1.65 p.m (SD 0.09) as determined by fluorescence-activated cell sorting (FACS). Both formulation (free cytokine vs. IL-2 liposomes) and route of administration were important variables in determination of the biodistribution and pharmacokinetic characteristics of IL-2. When free [125I]IL-2 was given i.v. to mice, only 6.5% was in the blood and 3% in liver and spleen 2 h after injection; on the other hand, at 2 h > 70% of i.v. [125I]IL-2 liposomes were detected in the blood, liver, spleen, and lungs. Mean i.v. elimination t ½ from the blood of rats given 20 x 106U/kg free cytokine or IL-2 liposomes was 41 versus 102 min, respectively, as measured by bioassay and 59 and 119 min as measured by enzyme immunoassay (EIA). After i.v. administration, the estimated Vdof IL-2 liposomes was 13-fold smaller than free cytokine. Intrathoracic (i.tx.), i.p., and s.c. administration of [125I]IL-2 to mice also demonstrated significant depot effects when IL-2 was incorporated into liposomes. These data suggest IL-2 liposomes may provide in vivo immunostimulation superior to the free cytokine due to biodistribution and depot characteristics.

Original languageEnglish (US)
Pages (from-to)3-31
Number of pages29
JournalJournal of Immunotherapy
Issue number1
StatePublished - Jul 1992


  • Cytokine
  • Interleukin-2-Pharmacokinetics.
  • Liposomes

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology
  • Pharmacology
  • Cancer Research


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