Coulter Pharmaceutical and SmithKline Beecham Announce Combined Results of Clinical Trials With Bexxar in Various Types of NHL.

SOUTH SAN FRANCISCO, Calif. and PHILADELPHIA--(BW HealthWire)--Dec. 6, 1999--

Data Show High Response Rates and Long Duration of Remissions

Coulter Pharmaceutical, Inc. (Nasdaq:CLTR) and SmithKline Beecham (NYSE:SBH) today announced promising combined data from multiple investigative trials of Bexxar(TM) (tositumomab, iodine I 131 tositumomab) for the treatment of various types of non-Hodgkin's lymphoma (NHL).

The data demonstrated high response rates and long durations of cancer remission with Bexxar when used for the treatment of low-grade or transformed low-grade NHL. Additionally, the companies announced combined data on Bexxar for the treatment of relapsed small lymphocytic lymphoma.

The results were reported in separate presentations at the American Society of Hematology Annual Meeting being held this week in New Orleans. Bexxar is not yet approved for any of these indications.

In a poster presentation, Julie Vose, M.D., vice chair and professor at the University of Nebraska Medical Center, reported combined data on 179 patients with low-grade NHL from five Phase I-III clinical trials. The data demonstrated that 145 patients (81 percent) responded to Bexxar, compared to 52 percent who

had responded to their last chemotherapy.

Additionally, 69 patients (39 percent) experienced a complete response of their disease following Bexxar, compared to 14 percent experiencing a complete response to their last chemotherapy. Importantly, long-term follow-up showed a median duration of complete remission of 57 months.

"Initial evidence that a therapy is working comes in the form of responses, particularly complete responses," said Dr. Vose. "Of greater importance in cancer treatment, however, is how long those responses are sustained.

"The response and duration data for Bexxar are compelling and continue to support the promise of this radioimmunotherapy for the treatment of low-grade and transformed low-grade NHL. Such long-lasting remissions are especially encouraging given the poor prognosis of many of these patients at the time they received Bexxar."

In a separate presentation, Andrew Zelenetz, M.D., Ph.D., chief of Lymphoma Service at the Memorial Sloan-Kettering Cancer Center, discussed a combined analysis of Bexxar(TM) for the treatment of transformed low-grade NHL, an especially difficult-to-treat form of NHL for which there is no approved therapy.

In the combined data from 58 transformed low-grade NHL patients evaluated in several Phase I-III trials, Bexxar elicited a response in 31 patients (53 percent) with 17 patients (29 percent) experiencing a complete remission. The median duration of complete response was 20 months.

Data also were presented by Mark Kaminski, M.D., director of the Leukemia/Lymphoma Program at the University of Michigan Comprehensive Cancer Center, on 14 small lymphocytic lymphoma (SLL) patients treated with Bexxar in four Phase I-III clinical trials. Advanced SLL is an indolent and incurable type of lymphoma which is similar to chronic lymphocytic leukemia.

Patients in this analysis had received a median of four prior chemotherapy regimens with 11 patients (79 percent) at baseline demonstrating lymphoma cells in their bone marrow. Following treatment with Bexxar, nine patients (64 percent) responded to the therapy with three patients (21 percent) experiencing a complete remission of their disease. The median duration of complete response has not been reached and is greater than 19 months.

Short-term side effects associated with Bexxar included a decrease in blood counts. The principal toxicity associated with Bexxar was hematologic. In this group of studies, three to seven percent of patients experienced a platelet count of less than 10,000 cells/mm3 and 14 to 19 percent experienced absolute neutrophil counts of less than 500 cells/mm3.

A minority of the patients required support by platelet or red-blood-cell transfusion or growth factors. Transient mild to moderate non-hematologic toxicity occurred with the most frequent events being fatigue, fever and nausea in approximately one-third of patients. Approximately 10 percent of previously treated patients developed human anti-mouse antibodies.

Bexxar is a radioimmunotherapy involving an antibody conjugated to iodine 131 that attaches to a protein found only on the surface of B-cells, including non-Hodgkin's lymphoma B-cells. Bexxar is believed to work through multiple mechanisms of action resulting in immune system activity of the monoclonal antibody and the therapeutic effects of the iodine (I-131) radioisotope.

Through the targeted approach of Bexxar, the tumor cells receive a greater concentration of the therapeutic radiation while minimizing the radiation to normal tissues.

Coulter Pharmaceutical, Inc. is engaged in the development of novel drugs and therapies for the treatment of cancer and autoimmune diseases. The company currently is developing a family of cancer therapeutics based upon two drug development programs: therapeutic antibodies and targeted oncologics.

The company's most advanced product candidate is Bexxar(TM), a monoclonal antibody conjugated to a radioisotope. Initial efforts in the targeted oncologics program are focused on the development of a tumor-activated peptide pro-drug version of doxorubicin to potentially treat certain solid tumor cancers.

The company's therapeutic antibody program includes an antibody-based approach to block the Type I interferon receptor for the treatment of autoimmune diseases and transplant rejection. For more company information, visit Coulter Pharmaceutical's web site at www.coulterpharm.com.

SmithKline Beecham -- one of the world's leading healthcare companies -- discovers, develops, manufactures and markets pharmaceuticals, vaccines, over-the-counter medicines and health-related consumer products. For company information, visit SmithKline Beecham on the World Wide Web at http://www.sb.com.

SmithKline Beecham Oncology is committed to the research, development, manufacturing and marketing of therapeutic and supportive care products in oncology. Currently, SB Oncology markets Hycamtin(R) (topotecan hydrochloride), Kytril(R) (granisetron hydrochloride) and Compazine(R) (prochlorperazine), and has novel agents in development.

Except for the historical information contained herein, the matters discussed in this news release are forward-looking statements for Coulter Pharmaceutical, Inc. that involve risks and uncertainties, including uncertainties related to product development, uncertainties related to the need for regulatory and other government approvals, dependence on proprietary technology, uncertainty of market acceptance of Bexxar(TM) or the company's other product candidates and other risks detailed from time to time in the company's filings with the Securities and Exchange Commission (SEC). In particular, see "Risk Factors" in the company's filed Form 10-K for the year ended December 31, 1998.

Under the safe harbor provisions of the U.S. Private Securities Litigation Reform Act of 1995, SmithKline Beecham cautions investors that any forward-looking statements or projections made by the company, including those made in this news release, are subject to risks and uncertainties that may cause actual results to differ materially from those projected. Factors that may affect the company's operations are discussed in Exhibit 99 to the company's Annual Report on Form 20-F for 1998, filed with the U.S. Securities and Exchange Commission.