Introgen adenovirus demonstrates safety in hundreds of patients biosafety data presented in 190 patients at annual ASCO meeting

San Francisco, CA, May 14, 2001 – Introgen Therapeutics, Inc. (NASDAQ: INGN) today reported definitive biosafety information on INGN 201, its adenoviral-p53 gene therapy product candidate currently in Phase III clinical testing. These data were presented at the 37th Annual Meeting of the American Society of Clinical Oncology in San Francisco, CA.

The presentation described data from 190 patients treated intra-tumorally and demonstrated that there are no infectious risks associated with the adenoviral vector to the patients treated, or their families. The study further suggests that the adenovirus vector used in the treatment is genetically stable, meaning that there is no recombination or mutation after the administration of the treatment.

“Introgen has amassed the world’s largest safety database on adenoviruses with over 500 patients treated with INGN 201, currently in pivotal Phase III trials” said James A. Merritt, M.D., vice president of clinical affairs for Introgen. “No other gene vector system has been tested to the extent that Introgen’s adenovirus has in the clinic. Human safety has been evaluated following 8 routes of administration, including injections into various organs and tissues, as an instillation into the bronchial tree, mucosal infiltration into healthy surgical wound margins, and a repeated direct intravenous infusion. In each of these studies, the Introgen adenovirus demonstrates an impressive lack of toxicity, locally and systemically, at therapeutically active doses. By contrast, far less is known about the safety of other viral vectors such as the adeno-associated vectors, due to their less advanced development status. Although the Introgen adenoviral vector is replication-impaired, we believed it important to further demonstrate that the viral vector is not transmitted to members of a close household, under real world conditions. For other virus-based gene therapeutics, especially the replicating systems, this could still represent a concern.”

Earlier this year Introgen was awarded U.S. Patent No. 6,194,191 for the commercial scale production of adenovirus. This patent covers the commercial scale production of adenovirus regardless of whether the adenovirus is used as a delivery system for therapeutic genes such as p53, or used directly as a therapeutic agent. Over the past five years adenovirus has become by far the most commonly used vector for direct administration to patients. The gene therapy field has matured so that, in addition to INGN 201, there are a number of adenoviral products in Phase III, Phase I/II, or randomized Phase II clinical testing. Introgen has established itself as the de facto leader in the manufacture of adenoviral vectors for human trials, and has produced numerous lots of adenoviral product using its patented method.

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. In an announcement earlier this year, Introgen 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 has FDA inspected fully staffed validated Good Manufacturing Practices (cGMP) production facilities that are producing Phase III and commercial inventory of INGN 201.

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 and Introgen’s ability to complete its clinical trials or successfully commercialize INGN 201, INGN 241 or any other product candidates, using adenoviral delivery systems. 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 February 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).