News Release

Ribozyme Pharmaceuticals Enters VEGF Receptor Ribozyme Into Product Development

Peer-Reviewed Publication

Noonan/Russo Communications

New York, New York, November 12, 1997 - At a technology briefing held in New York today, Ribozyme Pharmaceuticals, Inc. (RPI) (Nasdaq:RZYM) announced commencement of product development activities for a ribozyme based therapeutic directed at the Vascular Endothelial Growth Factor (VEGF) receptor, with an expectation of submitting an IND by the end of 1998.

VEGF is secreted by numerous human tumors including cancers of the lung, breast, and colon. The chemically synthesized anti-VEGF receptor ribozyme (RPI.4610) has shown activity in multiple animal models of angiogenesis in both the eye and in cancers. For example, in mice bearing Lewis Lung Carcinomas, RPI.4610 inhibited development of tumor blood vessels resulting in significant inhibition of both tumor growth and metastasis. As a result, product development activities on RPI.4610 have begun, and an Investigational New Drug (IND) Application to initiate clinical trials in cancer is planned for submission prior to the end of 1998.

"Our preclinical animal efficacy experiments in both ocular and tumor models have conclusively shown efficacy of our ribozyme as an anti-angiogenic agent. The resulting therapeutic potential encompasses all of the major types of cancer and the two leading causes of blindness in the industrialized world, i.e., Age-Related Macular Degeneration and Diabetic Retinopathy," said Thomas H. Rossing, MD, Vice President of Product Development at RPI. In addition, Nassim Usman, Ph.D., Vice President of Research at RPI, noted, "These experiments also illustrate the potential of ribozymes in the Target Validation or Functional Genomics field. For example, there are currently at least 20 known molecular targets involved in angiogenesis, and the question of greatest importance has been to determine which one is important in disease" We have now validated the VEGF receptor as a key target in pathological angiogenesis, using two independent animal models."

The development of RPI.4610 is the result of a collaboration between RPI and Chiron Corporation (Nasdaq: CHIR) to use ribozymes for the treatment and/or diagnosis of diseases associated with five human therapeutic targets. Under terms of the agreement, RPI and Chiron expect to conduct product development jointly, sharing the potential profit and risk for products. RPI holds certain manufacturing rights for ribozymes and is currently manufacturing RPI.4610 to permit initiation of toxicology testing in 1Q98, while further internal review of development plans will take place within Chiron.

RPI and Chiron Corporation are also currently collaborating with City of Hope National Medical Center and Children's Hospital, Los Angeles to develop a gene therapy approach using ribozymes against HIV. The initial Phase I/IIa trial in HIV infected volunteers is nearing completion, with results expected to be released in early 1998.

"We are very pleased that our partnership with Chiron has been so productive," said Dr. Ralph Christoffersen, CEO and President of RPI. "The initial results in the Phase I - IIa HIV trial at City of Hope, together with our pharmacology results with VEGF receptor ribozymes, demonstrate the broad therapeutic potential of ribozymes - either chemically synthesized or produced by vectors. We look forward to continued successful collaboration with Chiron."

RPI is a public company that was founded to capitalize on the broad potential of ribozymes for use as human therapeutics and in other areas, including the identification of gene function and therapeutic target validation. Ribozymes are a form of RNA that have the ability to selectively inhibit protein production. RPI has also entered into collaborations with Schering AG plus a second collaboration with Chiron in the target validation and discovery area; with DowElanco for commercialization of certain ribozyme-based agricultural products; with Pharmacia Biotech AB on the production-scale synthesis of RNA and chimeric oligonucleotides; with Alza on ribozyme delivery; with Protogene Laboratories to develop automated machines for production of large numbers of ribozymes; and with IntelliGene Corporation for development of ribozyme-based diagnostics.

Chiron Corporation is a science-driven healthcare company that combines diagnostic, vaccine, and therapeutic strategies for controlling disease. Headquartered in Emeryville, California, near San Francisco, and with operations on four continents, Chiron had revenues in 1996 of more than $1 billion. Chiron participates in four global healthcare markets: diagnostics, including immunodiagnotics, critical care diagnostics and new quantitative probe tests; therapeutics, with an emphasis on oncology and infectious disease; and pediatric and adult vaccines. Chiron also has research programs in gene therapy, combinatorial chemistry, cancer, infectious and cardiovascular disease and critical care through its Chiron Technologies business unit.

This press release contains forward-looking statements that involve risks and uncertainties, and actual events or results may differ materially. These risk factors include actions by the U.S. Food and Drug Administration, technological advances, ability to commercialize and manufacture products and general economic conditions. These and additional risk factors are identified in our annual report to the Securities and Exchange Commission filed on forms 10-KSB and in other SEC filings.

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