Ligand's Ontak shows 50% response rate in lymphoma study

By Angela McDaniels

Seattle, Dec. 15 - Ligand Pharmaceuticals Inc. said its cancer drug Ontak (denileukin diftitox) benefited patients with relapsed/refractory T-cell and B-cell non-Hodgkin's lymphoma during phase 2 clinical studies.

The first phase 2 study, performed at the University of Texas M.D. Anderson Cancer Center in Houston, was designed to evaluate Ontak's activity in relapsed/refractory T-cell non-Hodgkin's lymphoma. Out of 26 evaluable patients, there was an overall 50% response rate, the company said.

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.

"Our data suggests that future studies are warranted to investigate Ontak in newly diagnosed T-cell non-Hodgkin's lymphoma as well as the use of Ontak in combination with other drugs in the relapsed/refractory setting," lead author Nam H. Dang of the Nevada Cancer Institute said in a company press release.

"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 non-Hodgkin's lymphoma," chief scientific officer Andres Negro-Vilar said in the release.

"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 non-Hodgkin's lymphoma."

Interim analysis of another phase 2 study showed a 33.3% response rate (13 out of 39) for relapsed/refractory B-Cell non-Hodgkin's lymphoma patients taking a combination of Ontak and rituximab.

Another 19% had stable disease. All but four responders had disease refractory to previous rituximab treatment, the company said.

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 ... Ligand plans to launch two new studies of Ontak plus rituximab in this patient population," Negro-Vilar said.

The study results were presented at the 47th annual meeting of the American Society of Hematology in Atlanta.

In 1999, the 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.

Ligand is based in San Diego and develops drugs to 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.

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