Polaris Group, of San Diego, said the first patient has been dosed in its phase I trial of ADI-PEG 20 in combination with sorafenib, a current first line therapy, for the treatment of advanced hepatocellular carcinoma (HCC). ADI-PEG 20 is designed to deplete the external supply of arginine, which causes arginine-dependent cancer cells to die while leaving the patient’s normal cells unharmed.