ZIOPHARM Reports Positive Interim Results in Patients With Advanced Melanoma From Ongoing Phase 1/2 Study of Ad-RTS-IL-12

ZIOPHARM Reports Positive Interim Results in Patients With Advanced Melanoma
From Ongoing Phase 1/2 Study of Ad-RTS-IL-12

   Potent biological activity observed in injected and non-injected lesions

            Findings presented at Melanoma Bridge 2013 Conference

       Conference Call Scheduled for 8:00 am EST on Monday, December 9

BOSTON, Dec. 7, 2013 (GLOBE NEWSWIRE) -- ZIOPHARM Oncology, Inc. (Nasdaq:ZIOP)
today announced positive interim results from its ongoing Phase 1/2 study of
Ad-RTS-IL-12, a novel DNA-based therapeutic candidate that is being evaluated
with the oral activator, veledimex, in patients with advanced melanoma. The
results from this multicenter study were presented at Melanoma Bridge 2013
Conference at the session "Best Abstracts on News in Immunotherapy", an
international conference co-sponsored by Istituto Nazionale Tumori Fondazione,
Sidra Medical and Research Center, and the Society for ImmunoTherapy of Cancer
that is being held in Naples, Italy.

In this study, 21 patients with unresectable, recurrent stage III/IV melanoma
have been treated with intratumoral injections of Ad-RTS-IL-12 and the oral
activator veledimex. The purpose of the study is to evaluate the safety and
tolerability of the Ad-RTS-IL-12 and veledimex therapy, determine tumor and
immune response, and select the optimal dose and schedule of veledimex for
future study. To date, expression of IL-12 mRNA in study subjects' tumors was
determined to be very high and tightly controlled by veledimex dose with
expression ranging from a median increase of approximately 1,000 times with an
oral dose of 100 mg to approximately 100,000 times with an oral dose of 160
mg. In addition, upon stopping veledimex dosing, expression of the IL-12 mRNA
returned to baseline levels, demonstrating the "on" and "off" control of
Intrexon Corporation's (NYSE:XON) RheoSwitch Therapeutic System® platform. In
this dose range, results to date demonstrate that Ad-RTS-IL-12 + veledimex has
potent biologic activity, as measured by on-mechanism and on-target toxicity
and response in injected and non-injected lesions. In addition, increased
tumor infiltrating lymphocytes were observed in the tumor microenvironment at
these doses, suggesting multiple favorable biologic effects of IL-12
expression. Following treatment, 11 of 16 evaluable patients have demonstrated
a response of stable disease or better on a per lesion basis.

The most common severe adverse events (SAEs) were pyrexia, hypotension, mental
status changes, and cytokine release syndrome. Four of seven patients with
SAEs had veledimex dosing stopped during cycle 1. Three had SAEs during
subsequent cycles, and stopped veledimex dosing at that time. Importantly, all
SAEs were reversed after veledimex dosing was stopped, demonstrating the "on"
and "off" control of veledimex on gene expression.

"Immunotherapy is a powerful and promising approach to the treatment of many
cancers, including advanced melanoma," saidDr. John Nemunaitis, MD, Executive
Medical Director,Mary Crowley Medical Research Center, and lead investigator
of the study."A major limitation to turning on the immune system in cancer is
the many checks and balances that mask the tumor from the immune
system.Delivery of interleukin-12 using the regulated gene expression system
Ad-RTS-IL-12 provides us with the ability to turn on the immune system and
finely control this potent anti-cancer immune response to derive clinical
effect and manage tolerability.To date, this study has demonstrated immune
response and encouraging activity, along with a tolerability profile that is
well controlled by dose of the activator ligand veledimex. This should combine
well with other emerging treatments to create a new treatment option for
advanced melanoma and other cancers."

"The ability to precisely modulate gene expression at the site of the cancer
represents a potential paradigm shift in cancer treatment," said Francois
Lebel, M.D., Senior Vice President, Clinical Development and Medical
Operations at ZIOPHARM."We believe the evidence of safety, efficacy and
control of gene expression in this study is encouraging and warrants the
completion of this trial and the pursuit of a larger Phase 2 clinical trial in
patients with advanced melanoma in 2014. We look forward to reporting the
full results of this study at a future medical meeting and to initiating
later-stage clinical testing in a larger patient population."

ZIOPHARM is developing Ad-RTS-IL-12 using Intrexon Corporation's RheoSwitch
Therapeutic System® platform to control the expression of interleukin-12 and
enable its safe and effective delivery as an anti-tumor agent.The company is
advancing the Ad-RTS-IL-12 platform in melanoma, breast cancer and

Conference Call Information:

ZIOPHARM management, joined by Larry Norton, M.D., Deputy Physician-in-Chief
for Breast Cancer Programs, Memorial Sloan-Kettering Cancer Center, Medical
Director, Breast Cancer Programs, will host a conference call and live audio
webcast on Monday, December 9, 2013, at 8:00 AM ET.The call can be accessed
by dialing (877) 402-8188 (U.S. and Canada) or (330) 871-4581
(international).The passcode for the conference call is 'ZIOPHARM.'To access
the live audio webcast, or the subsequent archived recording, visit the
"Investors - Events & Presentations" section of the ZIOPHARM website
atwww.ziopharm.com. The webcast will be recorded and available for replay on
the Company's website for two (2) weeks.

About ZIOPHARM Oncology, Inc.:

ZIOPHARM Oncology is a Boston, Massachusetts-based biotechnology company
employing novel gene expression and control technology to deliver DNA for the
treatment of cancer. ZIOPHARM's technology employs Intrexon Corporation's
RheoSwitch Therapeutic System® platform to turn on and off, and precisely
modulate, gene expression at the cancer site in order to improve the
therapeutic index. This technology is currently being evaluated in Phase 2
clinical studies of the immune system cytokine interleukin-12 for the
treatment of breast cancer and advanced melanoma. Multiple new Investigational
New Drug applications for new targets using synthetic biology technology with
monogenic and multigenic approaches are expected in 2014 and 2015. ZIOPHARM is
also developing novel small molecules as potential cancer therapeutics.

Forward-Looking Safe-Harbor Statement:

This press release contains certain forward-looking information about ZIOPHARM
Oncology, Inc. that is intended to be covered by the safe harbor for
"forward-looking statements" provided by the Private Securities Litigation
Reform Act of 1995, as amended. Forward-looking statements are statements that
are not historical facts. Words such as "expect(s)," "feel(s)," "believe(s),"
"will," "may," "anticipate(s)" and similar expressions are intended to
identify forward-looking statements. These statements include, but are not
limited to, statements regarding our ability to successfully develop and
commercialize our therapeutic products; our ability to expand our long-term
business opportunities; financial projections and estimates and their
underlying assumptions; and future performance. All of such statements are
subject to certain risks and uncertainties, many of which are difficult to
predict and generally beyond the control of the Company, that could cause
actual results to differ materially from those expressed in, or implied or
projected by, the forward-looking information and statements. These risks and
uncertainties include, but are not limited to: whether Ad-RTS-IL-12,
DC-RTS-IL-12, palifosfamide, darinaparsin, indibulin, or any of our other
therapeutic products will advance further in the clinical trials process and
whether and when, if at all, they will receive final approval from the U.S.
Food and Drug Administration or equivalent foreign regulatory agencies and for
which indications; whether Ad-RTS-IL-12, DC-RTS-IL-12, palifosfamide
darinaparsin, indibulin, and our other therapeutic products will be
successfully marketed if approved; whether any of our other therapeutic
product discovery and development efforts will be successful; our ability to
achieve the results contemplated by our collaboration agreements; the strength
and enforceability of our intellectual property rights; competition from other
pharmaceutical and biotechnology companies; the development of, and our
ability to take advantage of, the market for our therapeutic products; our
ability to raise additional capital to fund our operations on terms acceptable
to us; general economic conditions; and the other risk factors contained in
our periodic and interim SEC reports filed from time to time with the
Securities and Exchange Commission, including but not limited to, our Annual
Report on Form 10-K for the fiscal year ended December 31, 2012, and our
Quarterly Report on Form 10-Q for the quarter ended September 30, 2013.
Readers are cautioned not to place undue reliance on these forward-looking
statements that speak only as of the date hereof, and we do not undertake any
obligation to revise and disseminate forward-looking statements to reflect
events or circumstances after the date hereof, or to reflect the occurrence of
or non-occurrence of any events.

CONTACT: For ZIOPHARM Investor Relations:
         David Pitts
         Argot Partners
         Media Contacts:
         David Schull or Lena Evans
         Russo Partners, LLC

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