Phase II Study Demonstrates that ONTAK(R) Benefits Patients with Relapsed/Refractory T-Cell Non-Hodgkin's Lymphoma.

SAN DIEGO -- Second Phase II Study Combines ONTAK with Rituximab for Relapsed/Refractory B-Cell Non-Hodgkin's Lymphoma 

Ligand Pharmaceuticals Incorporated (Pink Sheets:LGND) cancer drug ONTAK(R) (denileukin diftitox) benefits patients with relapsed/refractory T-cell and B-cell non-Hodgkin's lymphoma (NHL) according to Phase II study results presented at the 47th annual meeting of the American Society of Hematology (ASH) in Atlanta.

T-cell Study

A poster presentation at ASH reported on the final results of a Phase II study performed at the MD Anderson Cancer Center in Houston, TX, by Dr. Nam H. Dang and colleagues. The study was designed to look at ONTAK's activity in relapsed/refractory T-cell NHL. In 26 evaluable patients, there was an overall 50% response rate. Of the 13 patients whose tumors positively expressed the p55 (CD25) component of the IL-2 receptor, 61.5% showed a complete or positive response. ONTAK was well tolerated at the dosage tested (which is the approved dose for CTCL). Preliminary results of this study were the subject of an abstract presented at ASH in 2004.

"Based on this data, ONTAK appears to be effective 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 Chief, Department of Hematologic Malignancies, Nevada Cancer Institute. "Our data suggests that future studies are warranted to investigate ONTAK in newly diagnosed T-NHL as well as the use of ONTAK in combination with other drugs in the relapsed/refractory setting."

Andres Negro-Vilar, M.D. PhD, and Ligand's executive vice president of research and development and chief scientific officer, added, "In fact, the response rate observed in patients with relapsed disease is similar to the response rates observed with combination chemotherapy in patients with newly diagnosed T-cell NHL. In addition, the results compare well with data on other agents presented at ASH for relapsed/refractory T-cell lymphoma. Additional registration studies are being planned to better define the role of ONTAK in combination with chemotherapy in the treatment of newly diagnosed and relapsed T-cell NHL."

B-cell Study

Dr. Dang is also the lead author of a second poster presented at the conference reporting on an interim analysis of a Phase II study to evaluate the efficacy of the combination of ONTAK and rituximab for relapsed/refractory B-Cell NHL. Of the 39 patients enrolled, 36 are evaluable for response. The overall response rate was 33.3% and another 19% had stable disease. All of the responders but four had disease refractory to previous rituximab treatment. The objective response rate in the subset of patients with relapsed/refractory follicular lymphoma was 64%. The investigators concluded that the novel combination of denileukin diftitox and rituximab has significant clinical activity in this heavily pretreated population, with toxicities that can be managed with premedications and close monitoring.

"Based on these favorable results in relapsed/refractory follicular lymphoma Ligand plans to launch two new studies of ONTAK plus rituximab in this patient population," said Dr. Negro-Vilar.

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). For more information, go to www.ligand.com.

Caution Regarding Forward-Looking Statements

This news release contains forward-looking statements within the meaning of section 21E of the Securities Exchange Act of 1934, as amended, that involve risks and uncertainties and reflect Ligand's judgment as of the date of this release. These statements include those related to clinical trials of ONTAK, their results and future studies. Actual events or results may differ from our expectations. For example, there can be no assurance that further studies will be initiated or successfully concluded, that ONTAK will progress through further clinical development or receive required regulatory approvals for additional indications, that future clinical trials will confirm any results presented here, or that ONTAK will be beneficial or successfully marketed for new indications. Additional information concerning these and other risk factors affecting Ligand can be found in prior press releases as well as in public periodic filings with the Securities and Exchange Commission, available via 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.