Development of an interleukin-2 slow delivery system.

The authors developed a slow delivery system for interleukin-2 (IL-2) using highly purified bovine collagen to overcome the rapid clearance and side effects of IL-2; 1 X 10(6) microns of recombinant human IL-2 was successfully infused into needle-shaped "IL-2 mini-pellets". Pharmacokinetic study in C57BL/6 mice revealed that a single subcutaneous injection of an IL-2 mini-pellet could prolong IL-2 retention and decrease maximal concentration in the serum. Elimination half-life was 360 min for subcutaneously injected IL-2 mini-pellets, while it was 8 and 15 min, respectively, for intravenous and subcutaneous injections of aqueous IL-2. No side effects were observed throughout the experiment. This slow delivery system using collagen as a carrier proved to be effective and may be applicable to other kinds of drugs.