First Drug in 20 Years Offers New Hope

FOR IMMEDIATE RELEASE CONTACT:
Julie Wood, Chiron Corporation, (510) 923-6686
Whitney Ertel, Ketchum Public Relations, (415) 984-2281

FIRST DRUG IN 20 YEARS OFFERS NEW HOPE FOR PATIENTS WITH DEADLY SKIN CANCER
Experts Urge Caution of Sun Exposure As Melanoma Cases Continue to Rise

EMERYVILLE, Calif., May 20, 1998 -- For the first time in more than 20 years, a new product is available to combat the deadliest form of skin cancer -- metastatic melanoma. Proleukin(r) (aldesleukin), a recombinant form of interleukin-2 approved this year by the U.S. Food and Drug Administration (FDA) for the treatment of patients with metastatic melanoma, is the only therapy proven to offer a reasonable chance of survival to those patients diagnosed with advanced-stage melanoma.

"Skin cancer -- not sun worship -- should be top of mind as Memorial Day and the summer season quickly approach," stresses Michael Atkins, MD, director of Melanoma and Biologic Therapy Programs at the Beth Israel Deaconess Medical Center in Boston and associate professor of medicine at Harvard Medical School. "New therapies such as interleukin-2 are producing significant results in some patients with advanced melanoma, but the keys to fighting skin cancer are still prevention and early detection."

Melanoma is one of only two cancers still increasing in incidence, as cited by the March report from the American Cancer Society, National Cancer Institute and Centers for Disease Control and Prevention. It is increasing faster than any other cancer today, according to the American Academy of Dermatology, and will affect more than 40,000 people this year, of whom 7,300 will develop metastatic disease and die. When looking at demographics, melanoma is the most prevalent cancer in women ages 25 to 29 and second only to breast cancer in ages 30 to 34.

Many people affected by melanoma are in the prime of their lives, with an average patient age of 46. If caught early, melanoma is highly treatable with surgery. However, once the melanoma spreads throughout the body (or metastasizes), it is usually fatal. The average survival at that point is just six to nine months.

One patient, Lanai Wallin, was only 27 years old when she was diagnosed with metastatic melanoma. "The melanoma started with a mole on my shoulder that began growing in size. Ultimately, the disease spread to my lungs and liver," said Lanai, who after five months of intense treatment with Proleukin, has been cancer free for nearly three years. "I never thought this deadly disease could happen to me, especially in my 20's. But as it turns out, I'm a prime candidate. I hope more people start to realize the dangers of sun exposure and really concentrate on prevention and screenings."

Proleukin is a recombinant, or laboratory-derived, version of interleukin-2 (IL-2), a naturally occurring protein produced by the human body. Like natural IL-2, Proleukin acts by stimulating the body's T-cells, considered the "quarterbacks" of the immune system, to recognize and attack cancer cells.

"The approval of Proleukin for metastatic melanoma is particularly important when you consider it is the only therapy proven to give patients with this disease an opportunity for complete and long-term results," said Magnus Lundberg, president of Chiron Therapeutics and Chiron Vaccines. "This disease calls for a powerful drug because once the diagnosis of metastatic melanoma has been made, the cancer typically has spread throughout the body and aggressive therapy is necessary."

At the recommended dose, Proleukin has been associated with capillary leak syndrome, which may cause severe hypotension and reduced organ perfusion. Most adverse events are self-limiting and usually, but not invariably, reversible within two or three days of discontinuation of therapy. Proleukin therapy should be restricted to patients with normal cardiac and pulmonary function and no active CNS disease.

Proleukin is administered in the hospital through an intravenous infusion, in two 5-day treatment cycles, separated by a 9-day rest period. Following the first course, patients are evaluated for response. If tumor shrinkage occurs, one or two additional courses can be administered.

"Side effects are significant but predictable, manageable and generally reversible," noted Dr. Atkins. "Treatment should be restricted to patients with excellent function and limited to centers experienced with managing the side effects. Although patients go through a lot, for those who achieve long-term benefit, it is clearly worth it."

Chiron Corporation was granted its license to market Proleukin for the treatment of metastatic melanoma in January 1998. Proleukin was tested in eight clinical trials in 270 patients at 22 institutions nationwide. Proleukin has been approved for the treatment of renal cell carcinoma (advanced kidney cancer) in the United States and Canada since 1992 and in Europe since 1989.

Chiron Corporation, headquartered in Emeryville, California, is a leading biotechnology company that participates in three global healthcare markets: diagnostics, therapeutics and vaccines. Chiron also conducts research and development in the fields of biological proteins, gene therapy and combinatorial chemistry.

# # #

NOTE: This document contains forward-looking statements that are subject to risk and uncertainties. There are a number of factors that could cause Chiron's actual performance to differ materially from expectations. These and other factors investors should consider are more thoroughly described in the company's Securities and Exchange Commission filings, including the Form 10-Q and Form 10-K.