By Mary Welch

Coulter Pharmaceutical Inc. and partner SmithKline Beecham submitted a biologics license application (BLA) for Bexxar, a treatment for relapsed or refractory, low-grade or transformed low-grade B-cell non-Hodgkin's lymphoma.

"We were really happy Coulter filed for the BLA - and in the second quarter, which is when they planned to," said Peter Ginsberg, senior research analyst with US Bancorp Piper Jaffray in Minneapolis.

Bexxar (tositumomab, iodine I 131 tositumomab) was given fast-track approval status by the FDA, and the companies are hoping it will be granted an expedited review.

"We'd like to be able to get final approval and get Bexxar available to doctors and patients by the end of the year," said Michael Bigham, president and chief executive officer of South San Francisco-based Coulter.

"We believe that Bexxar is on track for FDA approval in time for their year-end deadline," Ginsberg said.

Assuming the FDA accepts the application, which should take about a month, Coulter will receive a milestone payment from SmithKline Beecham (SKB) of "several million dollars," Bigham said.

Coulter and SKB entered into a $132 million deal to jointly commercialize Bexxar. London-based SKB paid $41.5 million up front and extended a $15 million line of credit to Coulter. The companies will equally share profits in the U.S., with Coulter receiving royalties from sales elsewhere. SKB has exclusive marketing and distribution rights throughout the world except the U.S. and Japan. (See BioWorld Today, Dec. 7, 1998, p. 1.)

Bigham declined to estimate how much Bexxar will capture in terms of market share or sales.

"There is a significant unmet medical need here," he said. "It is a sizeable market."

Ginsberg estimated Bexxar will be a "$400 million drug within the next three to five years. SmithKline thinks it'll be bigger. We continue to believe that Bexxar is one of the most promising cancer drugs in development today. SmithKline plans to make Bexxar its lead cancer drug."

Bexxar is a radioimmunotherapy involving an antibody specific to the CD20 antigen on B cells, which is conjugated to iodine 131 and attaches to a protein found only on the surface of B cells, including non-Hodgkin's lymphoma B cells.

In the intravenous antibody approach, a treatment to determine proper dosage is given, and about a week later a therapeutic dose is administered. Conventional chemotherapy treatments are given repeatedly over several months.

It is believed that Bexxar works through multiple mechanisms of action resulting in immune system activity of the monoclonal antibody and the therapeutic effects of the iodine radioisotope. With Bexxar's approach, the tumor cells receive a greater concentration of the therapeutic radiation relative to normal tissues.

If approved, Bexxar would be the first radioimmunotherapy approved in the U.S. for cancer, according to Coulter officials.

Non-Hodgkin's lymphoma is a form of cancer that affects the blood and lymphatic tissues. It is the sixth leading cause of death among cancers in the U.S. and has the second fastest growing mortality rate. About 300,000 people in the U.S. suffer from the disease and another 140,000 have low-grade or transformed low-grade disease.

The company will pursue other indications with Bexxar, including other B-cell based diseases, such as chronic lymphocytic leukemia and intermediate-grade non-Hodgkin's lymphoma.

Coulter's stock (NASDAQ:CLTR) closed Wednesday at $22.562, up 43.75 cents per share.

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