By Mary Welch

Coulter Pharmaceutical Inc. reported positive interim data from a Phase III trial of Bexxar, a treatment for non-Hodgkin's lymphoma expected to be the subject of a biologics license application filing later this year.

In order for the primary endpoint to be achieved, the length of time a patient's tumor needed to respond to the treatment had to be at least one month longer than the response time in prior chemotherapy in a significant number of patients.

"There were no surprises, and we are very encouraged by the percentage of patients that reached our endpoint," said Sylvia Wheeler, director of investor relations for Palo Alto, Calif.-based Coulter. "A success would have been 51 percent and we're seeing success rates of 77 percent."

Bexxar is an antibody conjugated to iodine 131. It attaches to a protein found only on the surface of B cells, including non-Hodgkin's B cells and some normal B cells, in order to provide a greater concentration of therapeutic radiation to tumor cells.

The intravenous antibody treatment is a two-pronged approach. First, a dose customized to the patient is given. Then, about a week later, a therapeutic dose is administered. Coulter believes Bexxar is the first instance of using a monoclonal antibody as stand-alone therapy. If approved, it would be the first radioiummontherapy approved in the U.S. for the disease.

Interim Phase III results compared 30 patients' duration of response to Bexxar to the duration of response shown in their prior chemotherapy. Those participating in the trials were in advanced stages of the disease and had relapsed within six months after completion of their last chemotherapy regimen.

Of the 30 tested, 22 had adequate follow-up data to judge against the primary endpoint. Of the 22, nine cases showed equal results. Of the remaining 13, 10 showed a longer duration of response compared to three who responded better to chemotherapy.

"So, really, the 77 percent represents 10 people who had a longer duration of response, and [there were] nine who had an equal response," Wheeler said. "That's 19 out of 22 who responded better or the same to Bexxar than to chemotherapy."

Side effects included a decrease in blood counts, a reversible condition that is generally self-limiting, the company noted. A minority of heavily pre-treated patients may require support by blood transfusion or growth factor.

Also, researchers found a mild to moderate flu-like syndrome.

"These side effects seem to be much less severe than those associated with chemotherapy," Wheeler said.

The trial enrolled 60 patients, all refractory to chemotherapy, having either no response to prior chemotherapy or disease progression within six months of their last chemotherapy treatment.

Last fall, Coulter raised $42 million in a public offering to support development of Bexxar.

Non-Hodgkin's lymphoma, the sixth leading cause of death among cancer patients in the U.S., affects the blood and lymph tissues.

Coulter's stock (NASDAQ:CLTR) closed Tuesday at $34.125, up $2.75. *

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