NEW YORK, March 11, 2013 (GLOBE NEWSWIRE) -- ZIOPHARM Oncology, Inc. (Nasdaq:ZIOP), a biopharmaceutical company focused on the development and commercialization of new cancer therapies, today announced the initiation of a randomized, open label Phase 2 clinical study of Ad-RTS IL-12 in combination with palifosfamide to treat patients with non-resectable recurrent or metastatic breast cancer. The two-part, multi-center U.S. study will enroll up to 68 patients with non-resectable, recurrent or metastatic breast cancer who have visible lesions or lesions accessible by injection. The study is designed to assess the safety and efficacy of the drug combination of Ad-RTS IL-12 and palifosfamide. Ad-RTS IL-12 is a targeted and controlled DNA-based therapeutic designed to express interleukin-12 (IL-12), a protein important for an immune response to cancer. Palifosfamide is a potent bi-functional DNA alkylating agent. Part one of the two-part study will consist of a safety assessment for Ad-RTS IL-12 and palifosfamide, alone or in combination. Part two will consist of an efficacy evaluation of the Ad-RTS IL-12 only arm and the combination arm. The primary endpoint of the study is rate of progression-free survival at 16 weeks. Secondary endpoints include objective response rate, duration of response and evaluation of pharmacodynamic tumor markers. "Several recent breakthroughs in cancer treatment are based on the hypothesis that the immune system plays a central role in suppressing both cancer's growth and metastasis," said John Nemunaitis, M.D., lead investigator and Executive Medical Director, Mary Crowley Medical Research Center. "For breast cancer, the positive correlation of survival with immune response in the tumor elicited by non-immune treatments has only recently been elucidated, and this understanding hints at the potential for exciting new breakthroughs in this still underserved population. We look forward to participating in this study and to gaining further insight regarding the combined effect of Ad-RTS IL-12, a selectively controlled immunotherapy, and palifosfamide, a potent bi-functional DNA alkylating agent."