Introgen presents preclinical data on INGN 251

Adenoviral-PTEN stimulates apoptosis while demonstrating anti-angiogenic properties in vitro

Seattle, WA, June 2, 2001 – Introgen Therapeutics, Inc. (Nasdaq: INGN) today reported promising preclinical results for INGN 251 (Adenoviral-PTEN) in two separate presentations at the Fourth Annual Meeting of the American Society of Gene Therapy (ASGT) in Seattle, Washington.

The PTEN tumor suppressor gene is frequently mutated or not present in multiple types of human cancers including melanoma. Using Introgen’s extensively tested adenovirus vector, combined with the PTEN gene, two scientific studies were conducted to assess the ability of PTEN to suppress tumor growth and angiogenesis, the process of new blood vessel formation that is essential for tumor growth.

In the first study, INGN 251 was delivered to human melanoma cancer cells. Upon analysis, apoptosis, or programmed cell death, was observed. This extends the anti-tumor observations that have already been made following PTEN gene transfer into models of brain, colorectal and endometrial cancer. The most significant finding of this study is the potent effects that INGN 251 had against tumor cells derived from highly metastatic melanoma even when their own PTEN genes had no mutations.

In the second study, two in vitro models using endothelial cells were constructed to test the effects of INGN 251 on angiogenesis. The first model showed a dramatic reduction in migration of human umbilical vein endothelial cells, and in the second model Ad-PTEN completely inhibited the formation of structures necessary for blood supply. These data indicate that Adenoviral-PTEN may not only prevent the growth of tumor cells, but may interfere with tumor blood supply.

“The results of these two preclinical studies are promising in that they indicate that INGN 251 may inhibit tumor cell growth with no adverse effects on normal cells, while also acting as an inhibitor of tumor blood supply,” said Lou Zumstein, Ph.D., director of research at Introgen Therapeutics. “Introgen will continue to evaluate INGN 251 as a promising candidate for gene therapy.”

Introgen is a leader in the development and production of gene-based drugs for the treatment of cancer and other diseases. Introgen’s product candidates engage precise molecular targets to produce a highly specific therapeutic effect. Introgen specializes in combining appropriate gene delivery systems and therapeutic genes to make its gene-based drugs. Introgen’s lead product candidate, INGN 201, is currently in Phase III clinical trials for the treatment of head and neck cancer. INGN 201 has been used in numerous clinical trials worldwide either alone or in combination with conventional treatments such as chemotherapy and radiotherapy. Introgen is also conducting a Phase II clinical trial for INGN 201 in lung cancer and Phase I trials for INGN 201 in additional cancer indications including prostate, ovarian, bladder, brain, and breast cancer. Earlier this year, Introgen announced the published results of preclinical studies which indicate a possible application of INGN 201 whereby the human immune system may be directed to attack tumor cells. Introgen’s second product candidate, INGN 241 (Adenoviral-mda7), for the treatment of solid tumors, is in Phase I clinical development. Introgen controls a broad intellectual property portfolio that includes more than 200 pending and issued patents for a variety of gene therapy technologies. Introgen owns a fully staffed and validated Good Manufacturing Practices (cGMP) production facility that is producing Phase III and commercial inventory of INGN 201. Introgen has received a U.S. Patent for the commercial scale production of adenovirus.

Certain statements in this press release that are not strictly historical may be “forward-looking” statements, which involve risks and uncertainties. Such forward-looking statements include, but are not limited to, those relating to safety and efficacy of drug product candidates, the efficacy of our drug product candidates in treating melanoma cancer or cancer through anti-angiogenic mechanisms, and Introgen’s ability to complete its clinical trials or successfully commercialize INGN 251 or any other product candidates. There can be no assurance that Introgen will be able to commercially develop gene-based drugs, that necessary regulatory approvals will be obtained or that any clinical trials or studies undertaken will be successful or that the proposed treatments will prove to be safe and/or effective. The actual results may differ from those described in this press release due to risks and uncertainties that exist in Introgen’s operations and business environment, including, but without limitation, Introgen’s stage of product development and the limited experience in the development of gene-based drugs in general, its dependence upon proprietary technology and current competition, history of operating losses and accumulated deficits, Introgen’s reliance on collaborative relationships, and uncertainties related to clinical trials, safety, efficacy, the ability to obtain the appropriate regulatory approvals, patent protection and market acceptance, as well as other risks detailed from time to time in Introgen’s filings with the Securities and Exchange Commission, including its prospectus dated October 12, 2000 and the 10-Q filed on May 14, 2001. Introgen undertakes no obligation to publicly release the results of any revisions to any forward-looking statements that reflect events or circumstances arising from the date hereof.

Editor's Note: For more information on Introgen Therapeutics, or for a menu of archived press releases, please visit the Company Website at: www.introgen.com, or call Introgen’s toll-free Investor Relations hotline at 1-877-776-GENE (4363).