Abstract
Recombinant human interleukin 2 purified from Escherichia coli has limited solubility at neutral pH and a short circulatory half-life. This recombinant interleukin 2 was chemically modified by an active ester of polyethylene glycol. The modified interleukin 2 was purified by hydrophobic interaction chromatography and characterized by sodium dodecyl sulfate/polyacrylamide gel electrophoresis and isoelectric focusing. This conjugate was compared to unmodified recombinant interleukin 2 in vitro and in vivo. Covalent attachment of the hydrophilic polymer polyethylene glycol enhanced the solubility of interleukin 2, decreased its plasma clearance, and increased its antitumor potency in the Meth A murine sarcoma model.