Product Candidate: IDEC-151/CLENOLIXIMAB (anti-CD4)

IDEC-151 (Clenoliximab) is a PRIMATIZED® monoclonal antibody which targets the CD4 receptor that appears on helper T cells. These cells play a central role in both inducing and perpetuating response by directing the actions of other immune system cells. Once bound to CD4, IDEC-151 is thought to block that receptor’s function, and thus prevent the helper T cell from becoming activated, without seriously affecting other immune system functions. By regulating the activity of the cell that triggers harmful inflammation, anti-CD4 therapy may provide a longer acting and potentially less toxic alternative to current treatments for a variety of inflammatory diseases.

Clinical Trial Update
In August 2000 IDEC launched a Phase II clinical trial with IDEC-151 in combination with methotrexate in rheumatoid arthritis. Results are expected in the first half of 2002.

Marketing Rights Reacquired
In February 2000, IDEC amended and restated its agreement with GlaxoSmithKline which resulted in the return of all anti-CD4 program rights, including IDEC-151. The company will receive no further funding from GlaxoSmithKline under the restated agreement. As part of the restated agreement, GlaxoSmithKline has the option to negotiate commercialization and copromotion rights with IDEC for the first compound based on our PRIMATIZED anti-CD4 antibodies to complete a Phase II study. If IDEC does not elect to commercialize and copromote the compound with GlaxoSmithKline, it will pay GlaxoSmithKline royalties on sales by IDEC, its affiliates and licensees on any products emerging from the rights returned to IDEC under the restated agreement.

IDEC and its partner GlaxoSmithKline (GSK) clinically tested IDEC-151 in Phase I and Phase II studies in rheumatoid arthritis. In two Phase II studies the efficacy of IDEC-151 was demonstrated. However, in February 1999, GSK discontinued clinical development of IDEC-151 in rheumatoid arthritis.