Enzon Pharmaceuticals Inc., of Piscataway, N.J., presented Phase II data showing PEG-SN38 (EZN-2208) demonstrated activity in patients with previously treated metastatic breast cancer. Overall response was 21 percent in patients previously treated with anthracycline and taxane (AT) and 11 percent in patients previously treated with anthracycline, taxane and capecitabine (ATX).