ZIOPHARM Announces Unanimous Recombinant DNA Advisory Committee (RAC) Approval for Phase 1 Study of Ad-RTS-IL-12 in Subjects

ZIOPHARM Announces Unanimous Recombinant DNA Advisory Committee (RAC) Approval
for Phase 1 Study of Ad-RTS-IL-12 in Subjects With Recurrent or Progressive

BOSTON, Dec. 6, 2013 (GLOBE NEWSWIRE) -- ZIOPHARM Oncology, Inc. (Nasdaq:ZIOP)
today announced the unanimous approval of the National Institutes of Health's
Recombinant DNA Advisory Committee (RAC) for the initiation of a Phase 1 study
of Ad-RTS-IL-12, an adenoviral vector engineered to express interleukin-12
under the control of veledimex, an oral activator, in subjects with recurrent
or progressive glioblastoma or grade III malignant glioma (brain cancer).
ZIOPHARM has announced plans to launch a Phase 1 study of Ad-RTS-IL-12 in
malignant glioma in the first half of 2014. The Company is currently studying
Ad-RTS-IL-12 in Phase 2 studies in melanoma and breast cancer.

"Malignant gliomas remain one of the deadliest forms of cancer. The
stimulation of an immune response is a novel and intriguing therapeutic
approach," said E. Antonio Chiocca, M.D., Ph.D., Chairman, Department of
Neurosurgery, and Co-Director of the Institute for the Neurosciences, Brigham
and Women's Hospital/ Dana Farber Cancer Institute, and Harvey Cushing
Professor of Neurosurgery, Harvard Medical School. "Important variables to
the efficacy and safety of such therapies include the immune-privileged status
of the central nervous system, the processes that contribute to the
suppression of immune responses and the ability to modulate a brain tumor
specific immune response. In animal tumor models, Ad-RTS-IL-12 and veledimex
demonstrate a significant ability to overcome these barriers by localizing and
tightly controlling expression of the potent immune cytokine interleukin-12.
I look forward to seeing this promising therapeutic approach move quickly into
clinical trials in patients with malignant brain tumors."

ZIOPHARM is developing Ad-RTS-IL-12 using Intrexon Corporation's (NYSE:XON)
RheoSwitch Therapeutic System® (RTS®) platform to control the expression of
interleukin-12 and enable its safe and effective delivery as an anti-tumor
agent.ZIOPHARM and Intrexon recently presented preclinical study results at
the 2013 AACR-NCI-EORTC International Conference on Molecular Targets and
Cancer Therapeutics, supporting the capability of Ad-RTS-IL-12 in the
treatment of glioma. These studies showed both the ability for veledimex to
penetrate the blood brain barrier and a dose-related increase in survival in a
mouse GL-261 glioma model. Animals treated with Ad-RTS-IL-12 survived
throughout the duration of the study (100% survival at 75 days) with no
significant adverse clinical signs observed. In contrast, the mean survival
in the control groups was 22 (±3) days. These findings support localized
regulated IL-12 production as an approach for the treatment of malignant

"The NIH Committee's decision is an important step forward in bringing
Ad-RTS-IL-12, a potentially transformative new DNA-based therapeutic, to the
treatment of gliomas," said Francois Lebel, M.D., Senior Vice President,
Clinical Development and Medical Operations at ZIOPHARM."In tumor models,
Ad-RTS-IL-12 and veledimex demonstrate a unique ability to overcome these
barriers by localizing and tightly controlling expression of the potent
cytokine interleukin-12.Our preclinical data to date demonstrate both a
precisely controlled biologic response using this gene expression system as
well as a remarkable effect on these tumors, suggesting further evaluation in
the clinic. We expect to initiate a multicenter Phase 1 study in the first
half of next year, and look forward to understanding the clinical potential of
this therapy in brain cancers."

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 platform 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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