Introgen Therapeutics, Inc. (ticker: ingn, exchange: NASDAQ) News
Release - 5/17/04


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New Data Support Utility of Introgen's Oncolytic Viruses in the
Treatment of Cancer

AUSTIN, Texas, May 17 /PRNewswire-FirstCall/ -- Introgen
Therapeutics, Inc. (Nasdaq: INGN) today announced the publication of
preclinical data from studies of two oncolytic viruses that have
potential as novel cancer therapies. Introgen has licensed rights to
these oncolytic viruses and other related technologies from VirRx,
Inc. The studies were conducted in the laboratory of William S.M.
Wold, Ph.D., chairman of the Department of Microbiology and
Immunology at the Saint Louis University School of Medicine and
founder and chief executive officer of VirRx, and are published in
the current issue of Cancer Research.

INGN 007 (VRX-007) and VRX-009 are novel oncolytic adenoviruses that
have been engineered to kill cancer cells via viral replication.
These viruses can be engineered so that they are active in specific
types of cancer cells. The data published today indicate that INGN
007 and VRX-009 efficiently killed cancer cells in culture. VRX-009,
which has been designed to kill cells that carry a mutation common in
many colon cancers, efficiently killed cultured colon cancer cells,
but not lung cancer cells. INGN 007 effectively killed both types of
cancer cells. In an animal model of colon cancer, injection of either
INGN 007 or VRX-009 into tumors suppressed tumor growth more
efficiently than a negative control (five-fold and ten-fold
suppression, respectively). INGN 007 also completely suppressed tumor
growth in a lung cancer model of disease.

Louis Zumstein, Ph.D., director of research at Introgen, said "These
preclinical data are very promising, and support our belief that
oncolytic adenoviruses have enormous potential as a new class of
cancer therapies that may provide potent and selective killing of
cancer cells. These data also illustrate the flexibility of
engineered oncolytic adenoviruses to target selected tumor types with
great specificity. Our expertise in developing adenoviral-based
cancer therapies, including Advexin in Phase 3 trials and INGN 241 in
Phase 2 trials, positions us to be the leader in tumor-specific
oncolytic adenoviruses. We are conducting additional studies to
support the continued development of our oncolytic adenovirus
programs."

INGN 007 and VRX-009 are replicating adenovirus vectors that over-
express ADP, an adenoviral protein that plays a key role in the
release of viral particles from infected cells. This release kills
the cell, and also yields a pool of new viral particles capable of
infecting additional cells within the tumor. The ability to
overexpress the ADP gene sets this technology apart from other
existing oncolytic viruses and has been shown to provide a powerful
antitumor effect. Introgen holds an exclusive license to this
technology from VirRx.

"Oncolytic adenoviruses kill cancer cells through a mechanism that is
completely different from chemotherapy or radiation," said Dr.
Wold. "These viruses have the potential to treat many cancers that
are resistant to currently available therapeutics. Additionally, it
may be possible to use these viruses in combination with other
therapies to create novel treatment regimens."