ZIOPHARM Presents Positive Darinaparsin Clinical Data at ASCO`s Prestigious Clinical Science Symposium

Phase II Results Possible Basis for FDA DialogueRegarding Registration Trial
ORLANDO, Fla.--(Business Wire)--
ZIOPHARM Oncology, Inc. (Nasdaq: ZIOP) announced today that it presented
positive data from both Phase II intravenous (IV) and Phase I oral studies of
darinaparsin (ZinaparTM or ZIO-101), the novel organic arsenic molecule, as part
of the prestigious Clinical Cancer Symposia at the 45th Annual American Society
of Clinical Oncology (ASCO) meeting held in Orlando, FL, May 29th to June 2nd.

The study results were presented at the Clinical Science Symposium, New Agents
for Lymphoma, by Izidore S. Lossos, M.D, Chief of the Lymphoma Program, and
Professor of Medicine at the University of Miami Miller School Of Medicine.
Darinaparsin was one of three new drugs selected at this high profile ASCO
session.

"This drug is active in highly-refractory lymphoma patients and well tolerated,"
commented Dr. Lossos, lead investigator for the Phase II trial. "Interestingly a
lot of patients I and others have treated with this drug report feeling the best
they have felt since first getting lymphoma, having been on many different
treatments. The oral data are also promising and darinaparsin could well be
effective in treating other cancers as well."

The Phase II intravenous (IV) study is fully enrolled with 29 heavily pretreated
lymphoma patients. Of 19 evaluable patients, initial findings are 7 objective
responses, for an overall response rate of 37 percent, with 3 complete responses
(CRs) and 4 partial responses (PRs). Four additional patients had prolonged
stable disease (SD). There are 5 peripheral T-cell lymphoma (PTCL) patients
included in the 19 patients and in this group there were 3 objective responses,
for an overall response rate of 60 percent, of which there were 2 CRs and 1 PR.
Of the 4 patients with stable disease, 1 patient had PTCL. Darinaparsin was very
well tolerated with neutropenic fever as a severe adverse event in 1 patient.

On the advice of multiple experts, the Company intends, on complete review of
the final data, to open dialogue with the U.S. Food and Drug Administration with
a view of entering into a formal registration trial, likely for peripheral
T-cell lymphoma where, even with other agents under evaluation, there remains a
very high unmet medical need.

The two Phase I oral dose escalation studies included patients with all types of
cancers. Darinaparsin was dosed with various schedules. The study included 36
patients. The study has not yet reached MTD. Of 27 evaluable patients, 1 had a
partial response (head and neck cancer) and 15 had prolonged stable disease,
including head and neck, lymphoma, colon, and pancreatic cancers. Oral
darinaparsin was well tolerated with atrial fibrillation, congestive heart
failure and dyspnea as severe adverse events.

Treatment with darinaparsin has not evidenced any QT prolongation in either the
IV or oral studies. QT prolongation has been problematic with inorganic arsenic
and is a "black box" side effect warning in the labeling. The Company continues
dialogue regarding partnering and other initiatives regarding the further
clinical development of darinaparsin.

To view the presentation please visit:

http://www.ziopharm.com/docs/Darinaparsin_2009_ASCO_Symposium_Presentation.ppt

About ZIOPHARM Oncology, Inc.:

ZIOPHARM Oncologyis 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 (ZymafosTM or ZIO-201) references a novel composition (tris
formulation) that comprises the functional active metabolite of ifosfamide, a
standard of care for treating sarcoma, testicular and other cancers.
Palifosfamide delivers only the cancer fighting component of ifosfamide. It is
expected to overcome the resistance of ifosfamide and cyclophosphamide in
certain cancers. It does not have the toxic metabolites of ifosfamide that cause
the debilitating side effects of "fuzzy brain" (encephalopathy) and severe
bladder inflammation. Intravenous (IV) palifosfamide is currently in a Phase II
randomized trial to treat soft tissue sarcoma. An oral form of palifosfamide has
been developed preclinically.

Indibulin (ZybulinTM or ZIO-301)is a novel, oral tubulin binding agent that
targets both mitosis and cancer cell migration. Indibulin is expected to have
several potential benefits, including oral dosing, application in multi-drug
resistant tumors, no neuropathy and minimal overall toxicity. Indibulin has
shown early activity in Phase I study as a single agent in many types of solid
tumors. Indibulin is also completing Phase I trials in combination with Tarceva
and Xeloda. Oral indibulin preclinical "dose density" and "metronomic" dose
administration studies with our consultant Dr. Larry Norton have progressed to
the point of translation with the intention of further pursuit in clinical
study.

Darinaparsin (ZinaparTM or ZIO-101)is a novel organic arsenic being developed
for the treatment of various hematologic and solid cancers. Preclinical and
Phase I and II results to date demonstrate that darinaparsin is much less toxic
than other forms of arsenic. Intravenous darinaparsin continues to be studied in
a Phase II hematology trial with favorable treatment activity in certain
lymphomas and in Phase I study with oral administration. Darinaparsin has been
well tolerated in all trials to date.

ZIOPHARM`s operations are located in Boston, MA with an executive office in New
York. 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, 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. 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
International Investor Relations Inc.
Dennis Dobson, 203-258-0159
dsdobson@optonline.net

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