The enzyme superoxide dismutase (SOD) has been modified by the covalent attachment of monomethoxypolyethylene glycol (PEG) to form the conjugate PEG-SOD with greatly improved pharmacokinetics and clinically insignificant immunogenicity. Phase I trials have been completed in human volunteers with no adverse effects reported. PEG-SOD will be in evaluated in Phase II clinical trials for three indications: kidney transplants, burns, and multiple trauma. On completion of Phase II trials, we will move to Phase III trials for these indications.