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Nov 21, 2005

ZIOPHARM Oncology Announces ZIO-101 Data Published in Blood

ZIOPHARM Oncology Announces ZIO-101 Data Published in Blood

NEW YORK, NY - November 21, 2005 - ZIOPHARM Oncology, Inc. (OTC BB: ZIOP) announced today the publication of abstracts on its lead product candidate, ZIO-101. The preclinical abstracts are published and available online in Blood, the official journal of the American Society of Hematology. The abstracts include:

  • Abstract 5163: "In vitro activity of a novel organic arsenical (S-dimethylarsino-glutathione, ZIO-101) against multiple myeloma," by Lawrence Boise, Ph.D. and coworkers, University of Miami. In this study, the cytotoxic properties and mechanism of action of ZIO-101 were compared to arsenic trioxide (ATO) in four multiple myeloma cell lines. Data suggest that both ZIO-101 and ATO kill myeloma cells but that different modes of action may be involved. Cancer cells resistant to ATO may respond to ZIO-101.
  • Abstract 4446: "Comparison of uptake and intracellular induced structural changes of arsenic trioxide, an inorganic compound, and organic arsenic derivative S-dimethylarsino-glutathione (SGLU; ZIO-101) in NB4 acute promyelocytic leukemia (APL) cells," by Taghi Manshouri of University of Texas M.D. Anderson Cancer Center and coworkers. This study showed intracellular accumulation of atomic arsenic is about eight-fold higher for ZIO-101 than for arsenic trioxide (ATO) at comparable extracellular arsenic concentrations. The compounds also appear to have different modes of action for inducing programmed cell death: ZIO-101 is more toxic to mitochondria than ATO. The researchers conclude based on these data that the activity of ZIO-101 against cancers might be different than ATO.
  • Abstract 4445: "Mechanisms of increased reactive oxygen species (ROS) generation induced by organic arsenic derivative S-dimethylarsino-glutathione (SGLU; ZIO-101)," by Xiaodong Cheng of the University of Texas M.D. Anderson Cancer Center and coworkers. The anti-leukemia activity of ZIO-101 correlates with induction of intracellular ROS. This study revealed that low doses of ZIO-101 increased ROS via changes in NADPH whereas high-doses increase ROS by disrupting electron transport in mitochondria. These data suggest ZIO-101 may be operationally-specific for cancer cells which have major defects in mitochondrial energy reserves.

About ZIO-101

ZIO-101 is a novel organic arsenic product candidate currently in Phase I clinical trials. It is the lead product candidate from a "family" of novel organic arsenic compounds licensed to ZIOPHARM Oncology, Inc. from the University of Texas M. D. Anderson Cancer Center and Texas A&M University. A Phase I/II trial and a Phase II trial for ZIO-101 in advanced myeloma are in the advanced planning stage and will likely be followed with exploratory Phase II trials in other cancers. The Company expects a pivotal registration trial to initiate the first half of 2007. A second organic arsenic from the same licensing arrangement, ZIO-102, is the subject of further preclinical studies.

About ZIOPHARM Oncology, Inc.

ZIOPHARM Oncology, Inc. is a biopharmaceutical company seeking to acquire, develop and commercialize a diverse, risk-sensitive portfolio of in-licensed cancer drugs that address unmet medical needs. Currently, the Company is in U.S. Phase I studies for its two product candidates, ZIO-101 and ZIO-201. For more information, visit www.ziopharm.com.

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 the Company's 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:

Kelly Luethje
Manager, Investor Relations/Communication
617-259-1975