Chiron Grants Nonexclusive HCV License to Roche.

EMERYVILLE, Calif. -- Chiron Corporation (Nasdaq:CHIR) today announced that it has granted to F. Hoffmann-La Roche (Roche) a nonexclusive license for the research, development and commercialization of small molecule therapeutics against hepatitis C virus (HCV) drug targets. Under the terms of the agreement, Roche would pay Chiron up-front license fees, milestone payments and royalties on products. The specific financial terms and other details of the license were not disclosed.

"This agreement is a further example of Chiron's strong commitment to making its technology widely available to companies working to find therapies for hepatitis C," said Ursula Bartels, Esq., Chiron's general counsel. "We continue to strategically leverage our HCV intellectual property and actively license this technology to other companies, while we pursue our own research into therapeutic agents for hepatitis C."

About Hepatitis C

In 1987, Chiron scientists Michael Houghton, Ph.D.; Qui-Lim Choo, Ph.D.; and George Kuo, Ph.D., cloned and first identified HCV as the cause of transfusion-related non-A, non-B hepatitis. This breakthrough marked the first time a virus was cloned before it had been grown in tissue culture or otherwise isolated. The Chiron scientists received the prestigious Lasker Award in recognition of this discovery. Since the initial work, Chiron has been granted more than 100 HCV-related patents in over 20 countries, including patents directed to hepatitis C polypeptides encoded throughout the genomes of HCV. Such polypeptides can be used in a variety of medical applications, including blood screening, clinical diagnosis, vaccines and as therapeutic targets for drug screening. A number of therapeutic companies have been granted nonexclusive licenses to Chiron's HCV technology for drug screening purposes, including Bristol-Myers Squibb, GlaxoSmithKline, Japan Tobacco Inc., Gilead, Pfizer, Boehringer-Ingelheim, and InterMune.

About Chiron

Through its global Blood Testing, Vaccines and BioPharmaceuticals businesses, Chiron Corporation addresses human suffering with more than 50 diverse products to detect, prevent and treat disease worldwide. The company's success has come from its pioneering science, skill in delivering innovations in biotechnology and disciplined business approach. Chiron believes that science has the power to improve people's lives and harnesses that power to transform human health. For more information about Chiron, please visit www.chiron.com.

This news release contains forward-looking statements, including statements regarding licensing revenues and strategies relating to licensing activities that involve risks and uncertainties and are subject to change. A full discussion of the company's operations and financial condition, including factors that may affect its business and future prospects, is contained in documents the company has filed with the SEC, including the form 10-Q for the quarter ended June 30, 2004, and the form 10-K for the year ended December 31, 2003, and will be contained in all subsequent periodic filings made with the SEC. These documents identify important factors that could cause the company's actual performance to differ from current expectations, including the outcome of clinical trials, regulatory review and approvals, manufacturing capabilities, intellectual property protections and defenses, stock-price and interest-rate volatility, and marketing effectiveness. In particular, there can be no assurance that Chiron will increase sales of existing products, successfully develop and receive approval to market new products, or achieve market acceptance for such new products. There can be no assurance that Chiron's out-licensing activities will generate significant revenue, nor that its in-licensing activities will fully protect it from claims of infringement by third parties.

We do not undertake an obligation to update the forward-looking information we are giving today.