By Mary Welch

Idec Pharmaceuticals Inc. reported the results of a Phase I/II trial of IDEC-Y2B8, its radioimmunotherapy for relapsed or refractory B-cell non-Hodgkin's lymphoma, and started a Phase I trial of IDEC-114, its monoclonal antibody for psoriasis.

The San Diego-based company presented preliminary results from the Phase I/II trial on IDEC-Y2B8 at a December 1997 conference of the American Society of Hematology in San Diego, which prompted the company to start Phase III trials this past March. "Our current plan is to complete enrollment by the first quarter of next year," said Connie Matsui, vice president of planning and resource development

The final Phase I/II results, presented at the annual meeting of the American Society for Therapeutic Radiology and Oncology in Phoenix, showed that IDEC-Y2B8 was safe and reduced tumors when used in tandem with Rituxan therapy. Fifty-one patients with a variety of types of non-Hodgkin's lymphoma participated in the trial. Three dose levels were investigated, with the 0.4mCi per kilogram of patient body weight found to be particularly active. The 0.4mCi dose is being used in the 35-site Phase III study.

IDEC-Y2B8 is a murine monoclonal antibody tightly conjugated to the radioisotope yttrium-90 that targets the same CD20 antigen as does Rituxan, thus enabling the targeted delivery of radiation directly to B-cell tumors. Rituxan, approved by the FDA in November 1997 for non-Hodgkin's lymphoma, is an immunologically active, chimeric monoclonal antibody that targets the CD20 antigen on mature normal and malignant B cells. Rituxan is co-marketed by Idec and Genentech Inc., of South San Francisco.

On the first day of treatment, patients receive a single infusion of Rituxan (rituximab), followed by tumor imaging with IDEC-Y2B8. Seven days later, patients receive a second Rituxan infusion, followed by IDEC-Y2B8 therapy. Rituxan clears the blood of malignant and normal B cells, allowing IDEC-Y2B8 to penetrate the lymphatic system and direct the radiation to lymph tumors.

The study indicated that patients with low-grade or follicular NHL showed an overall response rate (complete and partial) of 82 percent across all dose groups. Twenty-seven percent of those patients had complete responses and 55 percent demonstrated partial responses.

Of those, 81 percent who received the 0.4mCi/kg dose showed complete or partial responses. Of the 28 low-grade or follicular responders, 14 are in ongoing remission and are being followed.

A complete response in lymphoma means there are no residual traces of the tumors that usually grow within the lymph nodes. A partial response means a reduction of the total tumor burden of at least 50 percent.

Adverse effects were generally transient and reversible hematologic ones, such as blood-cell count reductions.

Talks With Potential Marketing Partners Under Way

Idec plans to market IDEC-Y2B8 on its own in the U.S. and is in discussions with potential corporate partners for product commercialization elsewhere.

In addition, Idec started a 24-patient Phase I psoriasis trial of IDEC-114 to evaluate the safety, tolerability and pharmacokinetics of a single dose.

Biopsies from psoriasis lesions show that activated T cells in the dermal and epidermal layers express the B7-1 antigen. IDEC-114 binds to one of the two co-stimulating molecules on antigen-presenting cells. The antibody then blocks the binding of the B7-1 ligand on antigen-presenting cells to the CD28 receptor on T cells, thus interfering with T-cell activation

Idec is collaborating on IDEC-114 with Mitsubishi Chemical Corp., of Tokyo, which holds product commercialization rights in Asia. Idec retains exclusive rights elsewhere.

Idec's stock (NASDAQ:IDPH) closed Tuesday at $27.125, down $2.312. *