Public Release: 

Targeted Genetics presents advances in systemic gene delivery technology

Noonan/Russo Communications

--Intravenous gene delivery demonstrates efficacy in pre-clinical studies of breast cancer and head and neck cancer--

San Francisco, CA -- April 3, 2000 -- Targeted Genetics Corporation (Nasdaq: TGEN) today presented data on the company's synthetic gene delivery platform at the American Association of Cancer Research 91st Annual Meeting being held in San Francisco. Dr. Pervin Anklesaria, Senior Director of Research at Targeted Genetics, presented data indicating that the company's LPD (Lipid Polycation DNA) gene delivery system is capable of delivering genes systemically when delivered intravenously. Intravenous delivery of tgLPD-E1A, the company's second-generation cancer therapeutic, inhibited tumor growth in animal models of two different human tumors. The data were presented in an abstract titled "Systemic and Local Delivery of E1A-Cationic Lipid Complex Chemosensitizes Breast and Ovarian Cancer Cells In Vivo."

Advances in Systemic Gene Delivery Technology
In a study presented today, the LPD delivery system was used to deliver E1A, a proprietary tumor inhibitor gene, systemically to mice transplanted with human head and neck tumors. tgLPD-E1A was administered weekly beginning six days after tumor cells were transplanted into the animals. These cells express basal levels of HER-2/neu. At 13 weeks, 70 percent of the animals treated with tgLPD-E1A were tumor free, compared to only 10 percent of animals receiving either lipid alone or 5FU, and only 50 percent of animals receiving a lipoplex-E1A control.

"We have now demonstrated that intravenous delivery of tgLPD-E1A is able to inhibit tumor growth in animal models of breast and head and neck cancers," said Dr. Anklesaria. "These data show that the LPD gene delivery system may enable the systemic delivery of therapeutic genes, an important step in the evolution of gene delivery technologies. Significantly, tgLPD-E1A was seven-fold more effective at inhibiting tumor growth than was 5FU, a chemotherapy agent frequently used to treat head and neck tumors in humans. We are very encouraged by these results and are moving forward aggressively in the development of the LPD delivery system. Systemic delivery of E1A may provide a new gene therapy approach to treating patients with metastatic disease or other cancers that are not amenable to treatment by direct injection."

Previous studies have shown that tgLPD-E1A also inhibits tumor growth in a mouse xenograft model of breast cancer tumors. Significantly, the combination of tgLPD-E1A and paclitaxel inhibited tumor growth three-fold more efficiently than did paclitaxel alone. These data and studies evaluating tgDCC-E1A in combination with chemotherapy indicate that E1A sensitizes tumor cells to chemotherapeutic agents . Targeted Genetics is evaluating tgDCC-E1A (the company's local gene delivery formulation) in Phase II trials for head and neck cancer and in Phase I trials in combination with chemotherapy for ovarian cancer. Data from the Phase II trial are to be presented at the 36th American Society of Clinical Oncology Annual Meeting in May of this year. Patient enrollment in the Phase I trial is expected to be completed by the end of the year. The Company intends to begin human clinical trials of tgLPD-E1A in 2001.

"These data suggest that we are moving closer to attaining the holy grail of gene therapy - a systemic delivery system," said Dr. Barrie J. Carter, Executive Vice President and Director of Research and Development at Targeted Genetics. "Our ability to deliver genes systemically will expand the number of diseases that may be treatable with gene therapy approaches. We are very excited about the progress we are making in developing a variety of synthetic gene delivery systems, including formulations for systemic and local delivery."

Targeted Genetics is developing a variety of synthetic gene delivery systems, both on its own and in collaboration with Elan Corporation plc (NYSE: ELN). In July 1999, Targeted Genetics and Elan established a joint venture, Emerald Gene Systems, to develop advanced gene delivery technologies. The joint venture combines the company's expertise in vector development and manufacturing with Elan's leadership in novel drug delivery technologies. The addition of Elan's targeting technologies to delivery vehicles such as LPD may provide targeted, systemic approaches for the delivery of therapeutic genes.

"The promising clinical and pre-clinical data that we are generating in studies of both our DCC and LPD delivery platforms validate our plan to develop multiple gene delivery strategies," said H. Stewart Parker, President and Chief Executive Officer of Targeted Genetics. "We were the first company to bring adeno-associated virus (AAV) vectors into the clinic and we are leading the charge to develop a synthetic systemic gene delivery system. Our excellence in the development of both viral and synthetic gene delivery technologies reflects our robust capabilities in identifying and developing promising approaches for clinical and commercial applications. Our multiple gene delivery technologies will enable us to capitalize on the growing number of genes identified through genomic discovery efforts and to deliver the right gene to the right patient using the right vector."

Background on LPD
Targeted Genetics, in collaboration with Dr. Leaf Huang, Ph.D., Joseph Koslow Professor of Pharmaceutical Sciences at the University of Pittsburgh's School of Pharmacy, is developing a series of improved synthetic delivery systems based on various formulations of cationic lipids. In one of these systems, designated "LPD" for lipid-polycation-DNA, the DNA is condensed through the addition of a polycation to form small, degradation resistant cores encapsulated in a lipid shell. The resulting LPD formulation contains particles of defined size, which have enhanced stability and gene transfer efficiency. Pre-clinical experiments in non-tumor bearing mice have shown that the LPD system is able to deliver genes systemically through intravenous administration.

Background on E1A
E1A is a tumor inhibitor gene. Previous laboratory and animal studies have demonstrated E1A's ability to suppress metastases, induce apoptosis (programmed cell death) and reverse the over-expression of HER-2/neu, a cancer-causing gene. In patients with cancer, over-expression of the HER-2/neu oncogene is correlated with poor prognoses, increased tumor formation and metastasis and resistance to chemotherapeutic agents. Targeted Genetics is currently testing E1A in Phase II trials in patients with head and neck cancers and Phase I trials in patients with ovarian cancer.

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Targeted Genetics Corporation develops gene therapy products for the treatment of acquired and inherited diseases. The company has lead clinical product development programs targeting cystic fibrosis and cancer, and a promising pre-clinical pipeline of product candidates focused on hemophilia A, cardiovascular disease, cancer and AIDS prophylaxis. The company has a broad platform of gene delivery technologies, as well as a promising body of technology for cellular therapy. For more information about Targeted Genetics Corporation please visit the Company's web site at http://www.targetedgenetics.com.

NOTE: This release contains forward-looking statements relating to the Company's products under development, technologies and future operating results that are subject to certain risks and uncertainties that could cause actual results to differ materially from those projected. The words "believes", "expects", "intends", "anticipates", variations of such words, and similar expressions identify forward-looking statements, but their absence does not mean that the statement is not forward-looking. These statements are not guarantees of future performance and are subject to certain risks, uncertainties and assumptions that are difficult to predict. Factors that could affect the Company's actual results include the need for additional capital, the early stage of product development, uncertainties related to clinical trials, and uncertainties related to patent position. Reference is made to the Company's latest Annual Report on Form 10-K filed with the SEC for a more detailed description of such factors. Readers are cautioned not to place an undue reliance on these forward-looking statements, which speak only as of the date of this release. The Company undertakes no obligation to update publicly any forward-looking statements to reflect new information, events or circumstances after the date of this release or to reflect the occurrence of unanticipated events.

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