ZIOPHARM Presents Preclinical Data Supporting DNA-Based IL-12 Therapy for Breast Cancer

ZIOPHARM Presents Preclinical Data Supporting DNA-Based IL-12 Therapy for
Breast Cancer

Immunotherapeutic Strategy Results Presented at AACR 2013 Annual Meeting

NEW YORK, April 9, 2013 (GLOBE NEWSWIRE) -- ZIOPHARM Oncology, Inc.
(Nasdaq:ZIOP), a biopharmaceutical company focused on the development and
commercialization of new cancer therapies, announced today the presentation of
results from a study in a breast cancer murine model demonstrating the
anti-tumor effects and tolerability of Ad-RTS-mIL-12, a viral vector DNA-based
therapeutic for the controlled, local expression of IL-12, an important
protein for enhancing antitumor immunity. The data were presented at the
American Association for Cancer Research 2013 Annual Meeting (AACR 2013)
taking place April 6-10, 2013 in Washington, D.C. The study was conducted
jointly by ZIOPHARM and Intrexon Corporation, a synthetic biology company that
utilizes its proprietary technologies to provide control over cellular
function. ZIOPHARM is Intrexon's exclusive channel partner for the development
of in vivo therapeutics in oncology.

For the study, intratumoral administration of Ad-RTS-mIL-12 (Ad) was examined
in a 4T1 BALB/c mouse breast carcinoma model. Production of murine IL-12 was
controlled using Intrexon's RheoSwitch Therapeutic System^® (RTS^®) platform
and oral administration of the activator ligand INXN-1001 (AL). Oral
administration of AL was found to elicit a dose-related increase in plasma AL
levels, which correlated with increasing tumor levels of AL. The increase in
tumor AL levels in combination with Ad in turn resulted in a dose-related
increase in expression of mIL-12 in the tumor, with minimal increase in serum
mIL-12. This increase in AL-regulated tumor IL-12 levels correlated with an
increase in tumor-infiltrating CD4^+ and CD8^+ T cells in and adjacent to the
tumor, concomitant with a decrease in tumor regulatory T cells.This resulted
in a dose-related decrease in tumor growth rate.Moreover, the therapeutic
strategy appears to be well tolerated, as no change in clinical signs or body
weight was observed in the treated animals when compared with vehicle alone.

Samuel Broder, M.D., Chairman of Intrexon's Therapeutic Opportunities
Committee and former Director of the NCI (National Cancer Institute), stated,
"Two major obstacles for the development of immunotherapeutics in the
treatment of cancer are the ability of tumors to evade the anti-cancer
capabilities of the immune system and the toxicity often associated with the
systemic administration of immunomodulating agents.To overcome these
challenges, we have developed Ad-RTS-IL-12, a DNA-based system for the
regulated expression of IL-12, that allows for localized, controlled
expression of immunomodulating cytokines and activation of their corresponding
anti-tumor effects.This strategy is now being tested in the clinic, with the
recent launch of a Phase 2 Study of Ad-RTS-IL-12 combined with palifosfamide
in the treatment of advanced breast cancer."

Jonathan Lewis, M.D., Ph.D., Chief Executive Officer of ZIOPHARM, commented,
"These results support the hypothesis that localized delivery of IL-12 results
in an increase in tumor infiltrating lymphocytes concomitant with a reduction
in tumor growth.These findings suggest the applicability of this strategy in
the treatment of breast cancer, especially in the context of recent literature
addressing the positive correlation of survival with immune response measured
in breast cancer tumors treated with non-immune therapies.This novel
synthetic biology approach, which is being explored in several ongoing
clinical studies, holds transformative potential for the treatment of cancer."

About ZIOPHARM Oncology, Inc.:

ZIOPHARM Oncology is a biopharmaceutical company focused on the development
and commercialization of new cancer therapies. The Company's clinical programs
include:

Ad-RTS-IL-12 is currently being tested in two Phase 2 studies, the first for
the treatment of advanced melanoma, and the second in combination with
palifosfamide for the treatment of non-resectable recurrent or metastatic
breast cancer.Ad-RTS-IL-12 uses synthetic biology to enable controlled
delivery of therapeutic interleukin-12 (IL-12), a protein important for
enhancing the development of an immune response to cancer. Being developed in
partnership with Intrexon Corporation, ZIOPHARM's DNA synthetic biology
platform employs an inducible gene-delivery system that enables controlled
delivery of genes that produce therapeutic proteins to treat cancer. This is
achieved by placing IL-12 under the control of Intrexon's proprietary
biological "switch" (the RheoSwitch Therapeutic System^® or RTS^® platform) to
turn on/off the therapeutic protein expression at the tumor site.

Palifosfamide (ZIO-201) is a potent, bi-functional DNA alkylating agent that
has activity in multiple tumors by evading typical resistance
pathways.Palifosfamide is in the same class as bendamustine,
cyclophosphamide, and ifosfamide.

Indibulin (ZIO-301) is a novel, tubulin binding agent that is expected to have
several potential benefits, including oral dosing, application in multi-drug
resistant tumors, no neuropathy and a tolerable toxicity profile.It is
currently being studied in a Phase 1/2 trial in metastatic breast cancer.

Darinaparsin (ZIO-101) is a novel mitochondrial-and hedgehog-targeted agent
(organic arsenic) currently in ongoing studies with Solasia Pharma K.K.

ZIOPHARM's operations are located in Boston, MA, and New York City.Further
information about ZIOPHARM may be found at www.ziopharm.com.

Forward-Looking Safe Harbor Statement:

This press release contains certain forward-looking information about ZIOPHARM
Oncology 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 Palifosfamide, Ad-RTS
IL-12, 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 Palifosfamide, Ad-RTS IL-12, 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 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.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
         David Pitts or Lourdes Catala
         Argot Partners
         212-600-1902
         ziopharm@argotpartners.com
        
         Media Contacts:
         David Schull or Lena Evans
         Russo Partners, LLC
         858-717-2310
         212-845-4262
         david.schull@russopartnersllc.com
         lena.evans@russopartnersllc.com

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