Abstracts Demonstrate that ONTAK May Benefit Patients with Relapsed/Refractory T-Cell Non-Hodgkin's Lymphoma and B-Cell Chronic Lymphocytic Leukemia.

SAN DIEGO -- Ligand's (NASDAQ:LGND) ONTAK(R) (denileukin diftitox) may benefit patients with relapsed/refractory T-cell non-Hodgkin's lymphoma (NHL) according to an abstract of a poster presentation at the 46th annual meeting of the American Society of Hematology (ASH) on Sunday, Dec. 5, in San Diego.

Abstract 2641 covers an interim analysis of a Phase II study performed at the MD Anderson Cancer Center in Houston, TX, by Dr. Nam H. Dang and others. The study was designed to look at ONTAK's activity in relapsed/refractory T-cell NHL. In 17 evaluable patients, there was a 53% response rate with an additional 29% of patients with stable disease. Of the nine patients whose tumors positively expressed the p55 (CD25) component of the IL-2 receptor, 67 per cent showed a complete or positive response. ONTAK appeared to be well tolerated at the dosage tested.

"Based on this data, ONTAK has promising activity in relapsed/refractory T-NHL and is well tolerated at the dosing schedule tested," said lead author Nam H. Dang, M.D., Ph.D. and assistant professor of medicine at MD Anderson. "Additional patients are being studied to better define response rates and to evaluate the relationship between detectable CD25 expression and tumor response to ONTAK."

This data follows the results published on the B-cell arm of the study at ASH 2003 (abstract 4935) and in the Journal of Clinical Oncology (JCO), Oct. 15, 2004. The JCO study report on 45 evaluable relapsed or refractory B-cell NHL patients showed an overall response rate of 24.5% (6.7% complete response, 17.8% partial response) with a median time to treatment failure of seven months.

In a separate Phase II study of ONTAK reported in abstract 4824, there was a 40 per cent response rate among the 10 evaluable patients with fludarabine-refractory B-cell chronic lymphocytic leukemia. The investigators concluded that ONTAK "has activity in CLL with toxicities that can be managed with adequate premedication and close monitoring."

In all, there are five abstracts involving Ligand products -- three about ONTAK and two about Targretin(R) (bexarotene) -- scheduled for presentation or publication at the ASH conference. Full abstracts for the studies are available on the ASH internet site at www.hematology.org.

About ONTAK

In February 1999, the U.S. Food and Drug Administration granted Seragen, Inc., a wholly owned subsidiary of Ligand, marketing approval for ONTAK for the treatment of patients with persistent or recurrent cutaneous T-cell lymphoma, whose malignant cells express the p55 (CD25) component of the IL-2 receptor.

Full prescribing information for Ligand's products can be obtained in the United States from Ligand professional services by calling 800-964-5836, or on Ligand's Internet site at www.ligand.com.

About Ligand

Ligand discovers, develops and markets new drugs that address critical unmet medical needs of patients in the areas of cancer, pain, skin diseases, men's and women's hormone-related diseases, osteoporosis, metabolic disorders, and cardiovascular and inflammatory diseases. Ligand's proprietary drug discovery and development programs are based on its leadership position in gene transcription technology, primarily related to Intracellular Receptors (IRs) and Signal Transducers and Activators of Transcription (STATs). For more information, go to www.ligand.com.

Caution Regarding Forward-Looking Statements

This news release contains certain forward-looking statements that involve risks and uncertainties and reflect the company's judgment as of the date of this release. These statements include those related to the activity, effects, management and potential benefits of ONTAK and ongoing studies. There can be no assurance that results discussed here will be repeated, that these or other studies of ONTAK will be successful or that it will receive regulatory approvals for any additional indications. Additional information concerning these and other risk factors affecting Ligand's business can be found in prior press releases as well as in Ligand's public periodic filings with the Securities and Exchange Commission, available at www.ligand.com. Ligand disclaims any intent or obligation to update these forward-looking statements beyond the date of this release. This caution is made under the safe harbor provisions of the Private Securities Litigation Reform Act of 1995.