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-- Darinaparsin Demonstrates Potent Efficacy Effects in Various Solid Tumor Models --

NEW YORK--(BUSINESS WIRE)-- ZIOPHARM Oncology, Inc. (Nasdaq: ZIOP) announced today important new preclinical data on the efficacy of darinaparsin (Zinapar^TM, or ZIO-101) in various solid tumor models delivered at the EORTC-NCI-AACR International Symposium on Molecular Targets and Cancer Therapeutics being held in Berlin, Germany. Lead author, Susan Knox, M.D., Ph.D., Associate Professor, Department of Radiation Oncology and Member of BIO-X and Advising Dean at Stanford University School of Medicine, presented the abstract, "Darinaparsin (ZIO-101) is a novel cytotoxic and radiosensitizing anti-cancer agent".

The preclinical work was designed to study darinaparsin's cytotoxic and radiosensitizing effects against different solid tumor cell lines under both normoxic (NO) and hypoxic (HO) conditions. Hypoxia is an important condition in the microenvironment of solid tumor cells which creates resistance to cytotoxic drugs and radiation and causes cancer stem cells to re-grow the tumor. In these studies, hormone independent prostate cancer, pancreatic cancer, cervical cancer, and glioblastoma cell lines were treated with darinaparsin at concentrations ranging from 0.01 to 10 uM under either NO or HO conditions and irradiated with doses of 0 - 5 Gy. Results showed that darinaparsin is a potent cytotoxin under both NO and HO conditions and under HO when cells are resistant to radiation. Significant radiation enhancement was also observed in clonogenic assays under HO at clinically relevant doses, raising the potential for synergistic and dose-sparing radiation therapy. Darinaparsin's cytotoxic and radiation enhancing modes of action are distinct from other cytotoxic agents and were not dependent on generation of reactive oxygen species and DNA damage under HO.

"Darinaparsin's multiple mechanisms of action and potency provide for cytotoxicity and radiosensitization in a variety of tumor cell lines and environments," commented Dr. Knox. "This activity suggests a broad potential applicability for darinaparsin in the treatment of chemo- and radio-resistant solid tumors, with near term translational potential."

In September, ZIOPHARM announced that darinaparsin was granted Orphan Drug Designation by the U.S. Food and Drug Administration (FDA) for the treatment of peripheral T-cell Lymphoma (PTCL). Intravenous darinaparsin has demonstrated favorable results in a Phase II trial in lymphoma and particularly for PTCL. With a Phase I trial using the oral form ongoing in solid tumors and the results presented today, clinical development is expected to proceed in both PTCL and solid tumors.

About ZIOPHARM Oncology, Inc.:

ZIOPHARM Oncology is a biopharmaceutical company engaged in the development and commercialization of a diverse portfolio of cancer drugs. The Company is currently focused on three clinical programs.

Palifosfamide (Zymafos^TM or ZIO-201) is a novel DNA cross-linker in class with bendamustine, ifosfamide, and cyclophosphamide. ZIOPHARM is currently enrolling patients in a randomized, double-blinded, placebo-controlled Phase III trial with palifosfamide administered intravenously for the treatment of metastatic soft tissue sarcoma in the front-line setting. The Company expects to initiate additional studies in the near-term, including a Phase I intravenous study of palifosfamide in combination with standard of care addressing small cell lung cancer and a Phase I study of oral palifosfamide.

Darinaparsin (Zinapar^TM or ZIO-101) is a novel mitochondrial-targeted agent (organic arsenic) being developed intravenously for the treatment of peripheral T-cell lymphoma with a pivotal study expected to begin in late 2011. An oral form is in a Phase I trial in solid tumors.

Indibulin (Zybulin^TM or ZIO-301) is a novel, oral tubulin binding agent that is expected to have several potential benefits including oral dosing, application in multi-drug resistant tumors, no neuropathy and minimal overall toxicity. It is currently being studied in Phase I/II in metastatic breast cancer.

ZIOPHARM's operations are located in Boston, MA with an executive office in New York City. Further information about ZIOPHARM may be found at www.ziopharm.com.

ZIOP-G

Forward-Looking Safe Harbor Statement:

This press release contains forward-looking statements for ZIOPHARM Oncology, Inc. that involve risks and uncertainties that could cause the Company's actual results to differ materially from the anticipated results and expectations expressed in these forward-looking statements. These statements are based on current expectations, forecasts and assumptions that are subject to risks and uncertainties, which could cause actual outcomes and results to differ materially from these statements. Among other things, there can be no assurance that any of the Company's development efforts relating to its product candidates will be successful, or such product candidates will be successfully commercialized. Other risks that affect forward-looking information contained in this press release include the possibility of being unable to obtain regulatory approval of the Company's product candidates, the risk that the results of clinical trials may not support the Company's claims, the risk that pre-clinical or clinical trials will proceed on schedules that are consistent with the Company's current expectations or at all, risks related to the Company's ability to protect its intellectual property and its reliance on third parties to develop its product candidates, risks related to the sufficiency of existing capital reserves to fund continued operations for a particular amount of time and uncertainties regarding the Company's ability to obtain additional financing to support its operations thereafter, as well as other risks regarding the Company that are discussed under the heading "Risk Factors" in the Company's filings with the United States Securities and Exchange Commission. Forward-looking statements can be identified by the use of words such as "may," "will," "intend," " should," "could," "can," "would," "expect," "believe," "estimate," " predict," "potential," "plan," "is designed to," "target" and similar expressions. The Company assumes no obligation to update these forward-looking statements, except as required by law.

ZIOPHARM Oncology, Inc.
Tyler Cook, 617-259-1982
tcook@ziopharm.com
or
Media:
Argot Partners
David Pitts, 212-600-1902
david@argotpartners.com

Source: ZIOPHARM Oncology, Inc.

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