IDEC Pharmaceuticals Submits Documentation and Analysis Regarding ZEVALIN Radioimmunotherapy Biologics License Application in Response to FDA’s May 2001 Complete Review Letter

(BW HealthWire) — IDEC Pharmaceuticals Corporation (Nasdaq: IDPH) today announced it has recently submitted documentation and analysis to the U.S. Food and Drug Administration’s Center for Biologics Evaluation and Research in response to the FDA’s May 2001 Complete Review Letter of the company’s Biologics License Application (BLA) for ZEVALIN(TM) (Ibritumomab Tiuxetan) radioimmunotherapy.

As previously noted, the FDA’s Complete Review Letter requested information and analysis in two areas: (i) clinical and (ii) chemistry, manufacturing and controls. The company will await the FDA’s review of the response and further guidance on the next steps in the regulatory review process.

“Our ongoing, positive dialogue with the FDA has permitted us to respond to all of their open questions in a thorough and timely manner,” said William H. Rastetter, Ph.D., chairman, chief executive officer and president of IDEC Pharmaceuticals. “We look forward to working with the agency over the coming months as we seek marketing approval of ZEVALIN.”

IDEC is seeking marketing approval of ZEVALIN for the treatment of low grade, follicular, CD20-positive transformed, relapsed or refractory, B-cell non-Hodgkin’s lymphoma (NHL) and Rituxan(R) (Rituximab) refractory follicular NHL, which are cancers of the lymphatic system. If approved, ZEVALIN would be the first or one of the first radioimmunotherapies available for commercial use in the United States.

The FDA accepted the ZEVALIN BLA for filing in December 2000, assigning it to a six-month priority review. Issuance of the Complete Review Letter in May satisfied the FDA’s performance goal for priority review under the Prescription Drug User Fee Act (PDUFA). IDEC’s partner, Schering A.G., which has marketing rights to ZEVALIN outside the United States, had its Marketing Authorization Application (MAA) for ZEVALIN accepted for review by the European Medicines Evaluation Agency (EMEA) in January 2001.

IDEC Pharmaceuticals focuses on the commercialization and development of targeted therapies for the treatment of cancer and autoimmune diseases. IDEC’s antibody products act chiefly through immune system mechanisms, exerting their effect by binding to specific, readily targeted immune cells in the patient’s blood or lymphatic system.

For a menu of IDEC’s current news releases and quarterly reports or to retrieve a specific release, call (888) 329-2309. On the Internet check the News Center at IDEC’s website: http://idecpharm.cdmail.biz. As previously announced, IDEC’s full financial results for the second quarter are expected to be released on July 19, 2001, after the close of market. Following the release, IDEC will conduct a live webcast of a discussion by IDEC management of the financial results between 1:30-2:30 p.m. Pacific Time. The webcast will be accessible through a link at IDEC’s web site at http://idecpharm.cdmail.biz and will be available for 48 hours.

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 timing, success and cost of preclinical research and clinical studies, the timing, acceptability and review periods for regulatory filings, the timing of and ability to obtain regulatory approval of products, the achievement of future product sales, the level of manufacturing performance and 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, 2000 and Form 10-Q for the quarter ended March 31, 2001, 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 and Rituxan are registered U.S. trademarks of the company and ZEVALIN is a trademark of the company. The company is located at 3030 Callan Road, San Diego, CA 92121.

CONTACT: IDEC Pharmaceuticals Corporation