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| |  Aptamer Stops Angiogenesis, Tumor Growth BOULDER, Colo., Oct. 28, 1996 -- NeXstar Pharmaceuticals, Inc. (NASDAQ:NXTR) announced today that a Company scientist has presented data demonstrating that an aptamer antagonist of vascular endothelial growth factor (VEGF) can inhibit blood vessel growth, or angiogenesis, in vivo. The aptamer VEGF antagonist in a liposomal formulation also inhibited the growth of tumors in mice. This antagonist, created using the Company's proprietary SELEX combinatorial chemistry process, is in preclinical development as an anticancer agent. Speaking in Nice, France, at the 3rd International Symposium on the Impact of Cancer Biotechnology on Diagnostic and Prognostic Indicators in Predictive Oncology and Therapy, Nebojsa Janjic, Ph.D., director of cancer and cardiovascular research at the Company, discussed the development of a high affinity oligonucleotide that when embedded on the surface of a liposome binds to VEGF in vivo, inhibiting angiogenesis in a variety of model systems. In a healthy adult, angiogenesis occurs during the menstrual cycle and wound healing, but it is also a central feature of various disease states, including cancer and diabetic retinopathy. These studies were performed in collaboration with Parkash S. Gill, M.D., and his colleagues at the Norris Cancer Hospital, University of Southern California. In his presentation, Dr. Janjic showed data from in vitro experiments demonstrating that a liposomal formulation of the Company's VEGF aptamer bound with high affinity to VEGF and inhibited the growth of endothelial cells and cancer cells. In all experiments, the liposomal formulation substantially enhanced the inhibitory activity of the aptamer. In a second set of experiments, the anti-VEGF aptamer was injected into mice with growing tumors. In all mice treated with the aptamer, tumor growth was dramatically reduced. In addition, the aptamer blocked the VEGF-induced fluid leakage from blood vessels, a process that occurs near growing tumors and produces edema. In mice receiving placebo injections, tumors grew aggressively. "These are the first data showing that a systemically administered aptamer directed against an angiogenesis factor is capable of inhibiting angiogenesis in vivo, and that this will stop tumor growth," said Barry A. Polisky, Ph.D., NeXstar Pharmaceuticals' vice president for drug discovery. "This is encouraging both for this project and our entire oncology program. Furthermore, we are excited about the opportunity to combine our liposomal drug delivery efforts with our combinatorial chemistry drug discovery efforts." Larry Gold, Ph.D., NeXstar Pharmaceuticals' chief scientific officer, added, "We now have in vivo data for multiple aptamers developed using our SELEX combinatorial chemistry program. SELEX, by all appearances, works just as we always thought it would: it rapidly creates and identifies high-affinity, high-specificity aptamers that we can quickly turn into preclinical development candidates should the in vitro data justify that decision." NeXstar Pharmaceuticals, Inc. is an integrated pharmaceutical company engaged in the discovery, development, manufacturing and marketing of products to treat life-threatening diseases, including cancer and infectious diseases. The Company currently markets two drugs, AmBisome and DaunoXome. The Company has headquarters in Boulder, Colorado; research, development and manufacturing facilities in San Dimas, California; Antwerp, Belgium; Lakewood, Colorado, and Boulder; and marketing subsidiaries worldwide.
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