Chiron's Proleukin Granted a Marketing License in Canada for Second Indication, Metastatic Melanoma.

EMERYVILLE, Calif.--(BW HealthWire)--Jan. 8, 1999--Chiron Corp. (Nasdaq:CHIR) announced today that the Canadian Health Protection Branch has issued a Notice of Compliance to Proleukin(R) (aldesleukin) for metastatic melanoma.

Proleukin is currently approved in the United States, Canada and Europe for the treatment of patients with metastatic renal cell carcinoma. It is approved also in the United States for malignant metastatic melanoma. Proleukin is currently available to patients in 47 countries worldwide.

"Last year Proleukin became the only therapy in 20 years to be approved in the U.S. for the treatment of metastatic melanoma," commented Magnus Lundberg, president of Chiron Therapeutics and Chiron Vaccines. "Proleukin continues to produce significant results in patients with advanced skin cancer and we are excited that it has been approved in Canada for this indication."

In clinical trials of Proleukin, 16% (43/270) of patients responded to the drug and approximately half of these patients (22/43) remain alive over four years after treatment. In an analysis of the data, Proleukin produced a complete response in 6% (17/270) of patients. A complete response was defined as the total disappearance of tumors for two consecutive observations at least 28 days apart.

Approximately 60% of the 17 patients who achieved a complete response have remained in remission for greater than five years without further treatment. The median duration of complete response has not yet been observed, but is at least 40 months. By comparison, the median duration of partial response was 5.9 months. These data indicate that durable responses can be achieved in some metastatic melanoma patients treated with Proleukin.

Proleukin can result in a number of adverse events including capillary leak syndrome (CLS) and flu-like symptoms. Nearly all patients experienced serious toxicities; these included low blood pressure, decreased kidney and lung function, respiratory distress, cardiac abnormalities, changes in mental status and edema (fluid retention). In a majority of cases these adverse events were fully reversible after cessation of therapy.

Melanoma Background

Melanoma, a type of skin cancer whose overall incidence is increasing faster than that of any other cancer, occurs when certain skin cells called melanocytes (pigment-producing cells located in the top layer of the skin) become malignant, or cancerous. Melanoma is the most frequent cancer occurring in women between the ages of 25 and 29 years and, after breast cancer, is the second most frequent cancer in women 30 to 34 years of age.

Metastatic melanoma is the most advanced form of the disease and occurs as a result of the cancer spreading rapidly from the initial site to more distant parts of the body where it continues to grow and destroy tissue.

Proleukin: Enhancing the Body's Immune Defenses

Chiron introduced Proleukin(R) (aldesleukin) in the U.S. as the first approved treatment for metastatic renal cell carcinoma. Unlike traditional cancer therapies, Proleukin does not attack cancer cells themselves. Instead, it enhances the body's immune defenses by mimicking the way natural IL-2 activates the immune system and stimulates the growth and activity of cancer-killing cells.

Although Proleukin's exact mechanism of action is unknown, it is believed to help the body recognize cancer cells as foreign, thus boosting the body's immune response to them.

Chiron Corp., headquartered in Emeryville, is a leading biotechnology company that participates in three global healthcare markets: therapeutics, blood testing and vaccines. Chiron also conducts research and development in the fields of recombinant technology, vaccines, gene therapy, small molecule discovery and genomics. For more information, visit the company's Web site at www.chiron.com.

For more information about Proleukin for metastatic melanoma or renal cell carcinoma, please call Chiron's Professional Services group at 800/CHIRON-8 (800/244-7668), selection No. 2.

This news release may contain forward-looking statements regarding Proleukin. Actual results could differ materially from those described in this news release as a result of a number of factors, including, but not limited to the following: There can be no assurance that any product in the Chiron product pipeline will be successfully developed or manufactured, or that final results of human clinical trials will be supportive of regulatory approvals required to market products, or that final regulatory approval will be received in a timely manner, if at all, or that patient and physician acceptance of these products will be achieved. Chiron does not undertake any obligation to revise or update the statements in this press release to reflect events or circumstances after the date of this release.