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ZIOPHARM Presents Preliminary ZIO-201 Clinical Results at ASCO

ATLANTA--(BUSINESS WIRE)--Jun 5, 2006 - ZIOPHARM Oncology, Inc. (OTC BB: ZIOP) announced today preliminary data from a phase I study of ZIO-201 (isophosphoramide mustard-lysine) were presented at the 2006 American Society of Clinical Oncology Annual Meeting. These data support the Company's premise that certain adverse events associated with ifosfamide, an approved cancer drug extensively used in the United States and Europe, can be avoided with ZIO-201, the active metabolite of ifosfamide. ZIO-201 can be given at much higher doses than ifosfamide and without extensive intravenous hydration or co-administration of the drug mesna, protective measures required with ifosfamide use.

In this phase I study involving outpatients with progressive cancers following extensive therapy with other drugs, the maximum tolerated dose (MTD) of ZIO-201 is about 1.5 g/me2/cycle, a dose the Company estimates to be equivalent to 15-30 g/me2/cycle of ifosfamide. Ifosfamide doses at this level are rarely given because of substantial bladder and central nervous system (CNS) toxicity, which were not evident in this trial with ZIO-201. One patient with mesothelioma receiving ZIO-201 had stable disease for more than one year. Confirmation of the MTD and exploration of alternative dosing schedules is ongoing.

ZIO-201, the Company's proprietary alkylating drug, is the active metabolite of ifosfamide and, unlike ifosfamide, does not produce the other metabolites causing substantial toxicities. Data in human cancer cell lines, human-mouse xenografts and cancers resistant to cyclophosphamide and ifosfamide indicated ZIO-201 was active at doses similar to those achieved in the phase I trial. The Company recently initiated a phase I/II trial of ZIO-201 in advanced sarcoma. Trials in lymphoma and children's cancers are in late-stage planning, and an oral formulation is being explored.

"ZIOPHARM is pleased to see anti-cancer activity without several of the severe adverse effects associated with ifosfamide," said lead author and Senior Vice President of Research, Robert Peter Gale, M.D., Ph.D. "The possibility of achieving comparable or greater efficacy with less toxicity is an exciting opportunity."

About ZIOPHARM Oncology, Inc.

ZIOPHARM Oncology, Inc. is a biopharmaceutical company engaged in the development and commercialization of a diverse, risk-sensitive portfolio of in-licensed cancer drugs to address unmet medical needs. The Company applies new insights from molecular and cancer biology to understand the efficacy and safety limitations of approved and developmental cancer therapies and identifies proprietary and related molecules for better patient treatment. For more information, visit

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, and risks related to the Company's ability to protect its intellectual property and its reliance on third parties to develop its product candidates. The Company assumes no obligation to update these forward-looking statements, except as required by law.

Contact Investors ZIOPHARM Oncology, Inc. Kelly Luethje, 617-259-1975 or Media Kathryn Morris, 845-635-9828