Zevalin Therapeutic Regimen Produces Durable, Complete Responses in Patients with Non-Hodgkin's Lymphoma; Zevalin Also Safe and Effective as Second- or Third-Line Therapy.

Business Editors/Health/Medical Writers

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CHICAGO--(BUSINESS WIRE)--June 1, 2003

IDEC Pharmaceuticals Corporation (Nasdaq: IDPH) today announced updated results of four studies of Zevalin(R) (ibritumomab tiuxetan), which were presented at the 39th Annual Meeting of the American Society of Clinical Oncology (ASCO). Approved by the U.S. Food and Drug Administration in February 2002, Zevalin is the only commercially available radioimmunotherapy for the treatment of B-cell non-Hodgkin's lymphoma (NHL). A total of six abstracts on Zevalin were presented at ASCO.

"The clinical results reported in these abstracts are indeed encouraging," said Christine A. White, M.D., IDEC's Vice President, Medical Affairs and a co-author of four of the six Zevalin presentations. "Not only do the data indicate that Zevalin produces complete and enduring responses in a subset of patients with low grade, follicular and transformed B-cell non-Hodgkin's lymphoma (NHL), but data also indicate that Zevalin is associated with higher response rates and longer durations of response (DRs) when used before multiple courses of chemotherapy."

Zevalin Induces Durable Complete Responses

Thomas E. Witzig, M.D., of the Mayo Clinic, Rochester, MN, delivered a poster presentation discussing updated duration of response (DR) data in 154 patients with relapsed or refractory B-cell NHL in three clinical trials: 1) a Phase I/II dose-finding trial in indolent and aggressive NHL, 2) a Phase II trial of reduced-dose Zevalin for patients with low grade, follicular or transformed NHL and baseline thrombocytopenia, and 3) a Phase III randomized trial comparing Zevalin with Rituxan(R) (rituximab).

The three trials involved more than 30 academic and community cancer centers and included the only randomized clinical trial to date comparing radioimmunotherapy to another standard therapy. These trials show that Zevalin produces high overall and complete response rates and enduring responses in patients with low grade, follicular and transformed B-cell NHL.

Dr. Witzig noted, "At latest follow-up, the median duration of response in patients achieving a complete response approaches two years, with some patients still in remission at greater than five years."

Zevalin Safe and Effective as Second- or Third-Line Therapy

Christos Emmanouilides, M.D., of the UCLA's Jonsson Cancer Center, co-authored a study examining the safety and efficacy of Zevalin when administered as second- and third-line therapy for relapsed low grade, follicular, and transformed B-cell NHL. Dr. Emmanouilides said, "The efficacy and safety results suggest that second-line or third-line treatment with Zevalin can produce higher response rates and longer durations of response, as well as decreased hematologic toxicity, especially when used before multiple courses of chemotherapy."

In assessing safety in 349 patients the study authors noted that 16 percent of patients with three or more chemotherapies experienced Grade 4 thrombocytopenia compared to 7 percent of patients with two or less prior chemotherapies (p = 0.02), but no differences were seen with respect to the incidence of Grade 3/4 neutropenia or thrombocytopenia. Patients treated with purine analog chemotherapy were more likely to develop Grade 3/4 neutropenia (p = 0.05), thrombocytopenia (p = .025), and anemia (p less than .001) and had a longer median duration of Grade 3/4 thrombocytopenia (p = 0.03).

In assessing efficacy in a subset of 211 patients the study authors noted that higher overall response rates and complete response rates of 86% and 49%, respectively, in patients with one prior therapy compared to 72% and 28%, respectively, in patients with two or more prior therapies. Both of these differences were statistically significant. Moreover, in complete responders, the median duration of response (DR) was 22.8 months in patients with one prior therapy compared to 14.6 months in patients with two or more prior therapies.

Durable Remissions with Zevalin

Leo Gordon, M.D., of Northwestern University, Chicago, IL delivered a poster presentation discussing updated clinical results of the Phase III randomized Zevalin trial. Overall these results confirm that in low grade, follicular and transformed NHL Zevalin produces high response rates and durable remissions.

In the pivotal randomized Phase III trial overall response rates (ORR) of relapsed or refractory, low grade, follicular and transformed NHL patients were 80 percent for Zevalin and 56 percent for Rituxan; complete responses (CR/CRu) of 34 percent for Zevalin and 20 percent for Rituxan. After 29 months of follow-up, a trend towards longer remissions was observed in the following subsets: 1) the median duration of response (DR) in all patients was 13.9 months for Zevalin and 11.8 months for Rituxan, and the median DR among patients with follicular NHL was 16.7 months for Zevalin and 11.2 months for Rituxan; and 2) the median time to next therapy (TTNT, or the period patients were "off therapy") in all patients was 17.6 months for Zevalin, and 12.4 months for Rituxan, and the TTNT among patients with follicular NHL was 21.5 months for Zevalin and 13.1 months for Rituxan.

Sequential Doses of Zevalin Appear Safe

Gregory A. Wiseman, M.D. of the Mayo Clinic, Rochester, MN, delivered a poster presentation reporting interim results of a Phase I trial that demonstrated the safety of two sequential doses of Zevalin, without the use of stem cell or prophylactic growth factors.

Zevalin

The FDA approved Zevalin, a new type of targeted cancer therapy called radioimmunotherapy, on February 19, 2002. It is a key component of a unique treatment regimen for patients with certain types of B cell NHL. Zevalin combines a monoclonal antibody with a radioisotope. The monoclonal antibody in Zevalin recognizes and attaches to a particular cell-surface part of a B cell, called the CD20 antigen. This allows Zevalin to specifically target B cells, destroying the malignant NHL B cells and also normal B cells. The generic name for Zevalin is ibritumomab tiuxetan. Today, Zevalin is being investigated in multiple clinical trials at major medical centers in the U.S. and in a variety of treatment strategies, including combinations with front-line and salvage chemotherapy regimens and as part of autologous and allogeneic stem cell transplantation. Schering AG, our corporate partner outside the US, is sponsoring additional studies to evaluate the efficacy and safety of Zevalin in relapsed diffused aggressive NHL and in an adjuvant setting to increase response duration after front-line chemotherapy in follicular NHL.

Safety

In safety data based upon 349 patients, the most serious adverse reactions of the Zevalin therapeutic regimen were primarily hematologic, with grade 4 neutropenia, thrombocytopenia, and anemia occurring in 30%, 10% and 3% of patients treated at the 0.4 mCi/kg dose, respectively. Infusion-related toxicities were typically grade 1 or 2 and were associated with pre-administration of Rituximab (Rituxan). The risk of hematologic toxicity correlated with the degree of bone marrow involvement prior to Zevalin therapy. Seven percent of patients were hospitalized with infection (3% of these had neutropenia) and fatal cerebral hemorrhage (less than 1%) has occurred in a minority of patients in clinical studies. Myelodysplasia or acute myelogenous leukemia was observed in 1% of patients (8 to 34 months after treatment).

Boxed Warning Summary: Zevalin should only be used by health care professionals qualified by training and experience in the safe use of radionuclides. Fatal Infusion Reactions: Rare deaths have occurred within 24 hours of Rituximab infusions. These fatalities were associated with an infusion reaction symptom complex that included hypoxia, pulmonary infiltrates, acute respiratory distress syndrome, myocardial infarction, ventricular fibrillation, or cardiogenic shock. Prolonged and Severe Cytopenias: Yttrium-90 Zevalin administration results in severe and prolonged cytopenias in most patients.

General Information

IDEC Pharmaceuticals Corporation is a leader in the discovery, development, and commercialization of targeted immunotherapies for the treatment of cancer and autoimmune diseases. IDEC discovered and developed the first commercially available radioimmunotherapy product (Zevalin) approved in the United States, which is used to treat certain non-Hodgkin's lymphomas. Schering AG (Germany) has exclusive marketing and distribution rights outside the U.S. IDEC also discovered and, with co-promotion partner Genentech, Inc., developed the first monoclonal antibody product (Rituxan) approved in the United States for the treatment of cancer. Rituxan is approved in over 70 countries worldwide and is also used to treat various types of non-Hodgkin's lymphomas. IDEC is a San Diego-based, integrated biopharmaceutical company with multiple products in clinical stage development and strategic alliances in a variety of research platforms.

For a menu of IDEC's current news releases and quarterly reports or to retrieve a specific release, call [phone].

The statements made in this press release contain certain forward-looking statements that involve a number of risks and uncertainties. Actual events or results may differ from IDEC's expectations. For example, the risk factors listed from time to time in IDEC's SEC filings including but not limited to its Annual Report on Form 10-K for the year ended December 31, 2002 and Form 10-Q for the quarter ended March 31, 2003, may affect the actual results achieved by IDEC. These forward-looking statements represent the company's judgment as of the date of this release. The company disclaims, however, any intent or obligation to update these forward-looking statements.

IDEC Pharmaceuticals, Rituxan and Zevalin are registered U.S. trademarks of the company. The company's headquarters is located at 3030 Callan Road, San Diego, CA 92121.