New Data on OXiGENE's Lead Pre-clinical Compound, OXi4503, Confirms Potent Anti-tumor Activity in Cancer Models

OXiGENE, Inc. (NASDAQ: OXGN, XSSE: OXGN) announced today new data on the Company's lead pre-clinical compound, OXi4503, confirming its potent anti-tumor activity in pre-clinical models. OXiGENE believes that OXi4503 is the first in a new class of compounds being developed by the Company known as Ortho-Quinone Prodrugs, which display a novel cytotoxic effect in addition to vascular targeting capabilities. The OXi4503 data will be the subject of two presentations at the European Organization for the Research and Treatment of Cancer - National Cancer Institute - American Association of Cancer Research (EORTC-NCI-AACR) Symposium on Molecular Targets and Cancer Therapeutics taking place in Geneva, Switzerland September 28th through October 1st 2004.

Dr. Michael Horsman of the Aarhus University Hospital in Denmark will present a poster on anti-tumor activity of OXi4503 as a single-agent and in combination with radiation therapy. His study demonstrates substantial anti-tumor activity with OXi4503 in combination with radiation therapy, particularly compared to a more limited response to traditional therapies. Specifically, the radiation dose required to control or eradicate 50% of all tumors in these animals was reduced from 53 Gray to 34 Gray by administration of OXi4503. Additional data show that OXi4503 caused significant anti-tumor effects when administered as a single agent.

"Our use of OXi4503 in combination with radiation therapy shows greater efficacy than seen with any other clinically relevant treatment in this tumor model," said Dr. Horsman. "Although OXi4503 is similar in structure to OXiGENE's lead clinical compound CA4P, there is now evidence that OXi4503 has a secondary mechanism of action. In addition to the compound's ability to target aberrant blood vessels, OXi4503 appears to be metabolized in tumor tissue to an agent which may enhance tumor cell killing."

In the second presentation, Professor Dietmar Siemann from the Shands Cancer Center at the University of Florida will report on the activity of OXi4503 as a single agent and in combination with radiotherapy in a mouse sarcoma model. The data that will be reported shows that administration of OXi4503 to tumor bearing animals resulted in significant tumor growth inhibition. Moreover, when combined with radiation at 25mg/Kg dose of OXi4503, tumor cell death increased 20-50 fold over that seen with radiation alone.

"We are very excited about this new data on OXi4503 which demonstrates that the compound's increased anti-tumor efficacy can cause extensive cell death at both the central regions of the tumor as well as at the periphery," said Fred Driscoll, President and Chief Executive Officer of OXiGENE. "We expect this strong pre-clinical data with OXi4503 as both a single agent as well as in combination with radiation therapy to broaden our drug development opportunities. We anticipate advancing OXi4503 into clinical trials by year end."

Dr. Dai Chaplin, OXiGENE's Chief Scientific Officer followed by saying, "The data from these studies is both impressive and encouraging. It is consistent with recent data indicating that OXi4503 has an additional and distinct mechanism of action compared to our lead vascular disrupting agent CA4P. This data has provided evidence that once dephosphorylated, OXi4503 can be metabolized in tumor tissue creating a reactive metabolite thought to be an ortho-quinone. We believe OXi4503 represents a new class of therapeutic agents with potentially potent anti-tumor effects. Additional studies are now underway to further evaluate OXi4503 in vitro and in vivo."

About OXi4503

OXiGENE believes that OXi4503 is the first in a new class of compounds known as Ortho-Quinone Prodrugs, which display a novel cytotoxic effect in addition to their proven vascular targeting capabilities mediated by their action on the tubulin cytoskeleton. Unlike anti-angiogenesis agents that focus on preventing new tumor blood vessels from forming, agents similar to OXi4503, appear to attack existing blood vessel structures in solid tumors. OXi4503 exhibits some of the similar vascular shutdown properties of OXiGENE's CA4P but also has an additional cytotoxic mechanism of action that could enable destruction of the outside rim of cells residing next to and feeding off of normal tissue.

About OXiGENE, Inc.

OXiGENE is an emerging pharmaceutical company developing novel small-molecule therapeutics to treat cancer and eye diseases. The Company's major focus is the clinical advancement of drug candidates that selectively disrupt abnormal blood vessels associated with solid tumor progression and visual impairment. OXiGENE is dedicated to leveraging its intellectual property position and therapeutic development expertise to bring life saving and enhancing medicines to patients.

Safe Harbor Statement

Certain statements in this news release concerning OXiGENE's business are considered "forward-looking statements" within the meaning of the Private Securities Litigation Reform Act of 1995. These statements include, but are not limited to: the effect of OXi4503 on OXiGENE's drug development opportunities, the ability of OXi4503 to have potent anti-tumor effects and the advancement of OXi4503 into clinical trials by year end. Any or all of the forward-looking statements in this press release may turn out to be wrong. They can be affected by inaccurate assumptions OXiGENE might make or by known or unknown risks and uncertainties, including, but not limited to: the early stage of product development; the ability to secure necessary patents; uncertainties as to the future success of ongoing and planned clinical trials; and the unproven safety and efficacy of products under development. Consequently, no forward-looking statement can be guaranteed, and actual results may vary materially. None of OXiGENE's products under development have been approved for marketing by the FDA. Additional information concerning factors that could cause actual results to materially differ from those in the forward-looking statements are contained in OXiGENE's reports to the Securities and Exchange Commission, including OXiGENE's 10-Q, 8-K and 10-K reports. However, OXiGENE undertakes no obligation to publicly update forward-looking statements, whether because of new information, future events or otherwise.

Source: OXiGENE, Inc.