Abstract: The present invention is directed to uricase modified with polyethylene glycol and to methods of treating different illnesses characterized by increased circulating uric acid levels, including but not limited to, hyperuricemia and tumor lysis syndrome.

Abstract: The present invention provides methods for determining which cancer patients are susceptible to arginine depletion therapy and methods for treating cancer. The present invention also provides methods for predicting the appropriateness of arginine deprivation therapy for a cancer patient. The methods generally comprise obtaining a tumor sample from the cancer patient and detecting the presence or absence of evidence of urea cycle enzyme expression in the tumor sample. The absence of evidence of urea cycle enzyme expression in the tumor sample is indicative of a cancer patient who is a candidate for arginine deprivation therapy, and the presence of evidence of urea cycle enzyme expression in said tumor sample is indicative of a cancer patient who is not a candidate for arginine deprivation therapy.