BOSTON, June 1, 2013 (GLOBE NEWSWIRE) -- ZIOPHARM Oncology, Inc. (Nasdaq:ZIOP) today announced updated results from the Phase 1 study in advanced melanoma using Ad-RTS-IL-12, a novel DNA-based therapeutic candidate. Findings were presented in a poster presentation at the 2013 American Society for Clinical Oncology (ASCO) Annual Meeting being held May 31 – June 4, 2013 at McCormick Place in Chicago, IL. A presentation of the poster, titled "A phase I open-label study of Αd-RTS-hIL-12, an adenoviral vector engineered to express hIL-12 under the control of an oral activator ligand, in subjects with unresectable stage III/IV melanoma," was delivered by Gerald P. Linette, MD, PhD, Associate Professor, Medicine and Neurosurgery, Division of Oncology, at the Washington University School of Medicine. For the study, Ad-RTS-IL-12, an adenoviral vector engineered to express IL-12 utilizing the RheoSwitch Therapeutic System® (RTS®) technology, was injected intratumorally in patients with advanced melanoma (n=14). Expression of IL-12 was controlled through the administration of an oral activator ligand (INXN‑1001), which was administered in four ascending dose cohorts. The Company previously reported that compelling clinical activity was observed in five of seven (71 percent) patients dosed at the two highest dose levels (Nemunaitis et al. ASGCT 2013). The study further demonstrated that treatment with Ad-RTS-IL-12 + INXN-1001 was shown to increase intratumoral IL-12 mRNA transcription. The mRNA level was very tightly controlled (on and off) by the biologic switch and oral activator ligand. Consequent on the increase in IL-12 expression there was a major increase in tumor-infiltrating lymphocytes (CD8 +, CD45RO +) in the tumor microenvironment as measured in tumor biopsies. Subsequently clinical activity was observed in injected and non-injected lesions, primarily at the higher doses of INXN-1001 (100 and 160 mg), with inflammation, shrinkage, flattening, and depigmentation of lesions correlated with the highest serum levels of IFN-γ. ZIOPHARM is currently conducting a Phase 2 multi-center, single-arm, open-label expansion study in up to 15 patients with unresectable Stage III or IV melanoma. The Phase 2 study will focus on optimization of the dosing schedule, guided by pharmacokinetics and tolerability, using every other day dosing of the oral activator ligand.