Polaris Group, of San Diego, said preclinical data for ADI-PEG-20, pegylated arginine deiminase, showed that it may effectively treat acute myeloid leukemia, glioblastoma multiforme and bladder cancer. In those cancers, hypermethylation of a promoter gene for arginosuccinate synthetase leads to a deficiency of the enzyme, which causes tumors to be reliant on externally supplied arginine. ADI-PEG-20 degrades arginine, depriving the tumor of that nutrient. Polaris is preparing to begin pivotal Phase III trials of the drug in hepatocellular carcinoma.