Xcyte Therapies pulled the plug yesterday on plans to take its immune system-stimulator against cancer to the final stage of clinical trials...

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Xcyte Therapies pulled the plug yesterday on plans to take its immune system-stimulator against cancer to the final stage of clinical trials, instead shifting its focus to HIV.

The Seattle biotech company’s stock plummeted 17.6 percent, or 15 cents, to close at 70 cents a share yesterday after the news.

Bob Kirkman, Xcyte’s chief business officer, said the company dropped its study of the so-called “cancer vaccine” in patients with chronic lymphocytic leukemia because it reached a stalemate with the Food and Drug Administration over the scope and design of a clinical trial needed to gain approval.

The FDA insisted the company run a randomized trial in several hundred patients, with a goal of showing better survival than existing therapies, Kirkman said.

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Xcyte’s counterproposal was far different. It wanted to conduct the trial in fewer than 100 patients, aiming to clear the lower hurdle of showing improved tumor response rates. Because patients tend to live at least four to five years with the disease, the FDA’s proposed approach would have taken even longer to tell if the drug improved survival. Kirkman said such a trial would have taken too long for Xcyte, because of its limited cash resources.

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Carolyn Ramsden, a technician at Xcyte Therapies, counts blood cells received from a donor earlier this year.

“We ran into a roadblock with the FDA,” Kirkman said. “The only trial they were going to accept was one we couldn’t afford to do.”

Less than a year ago, Xcyte thought it was well on its way to a clinical trial. In September, company officials met with the FDA, and Xcyte said it thought they reached an understanding that its trial design was acceptable. But the FDA’s position changed when a personnel shift brought in a new reviewer with a different philosophy, Kirkman said.

Xcyte’s technique had shown promise in cancer, and Kirkman said some academic researchers will continue to study its technique through government-sponsored clinical trials. They were intrigued by results that showed 11 of 13 leukemia patients had significant shrinkage of their cancerous spleens, and that 12 had shrinkage of cancer in their lymph nodes.

Xcyte has struggled as a public company. It went public at $8 a year ago and has been in a constant slide. It had $39.5 million in cash and investments at the end of March, and had a net loss of $7.2 million in the first three months of 2005.

At yesterday’s closing price, the company’s market capitalization was $13.8 million — approximately one-third of its March 31 cash and investments.

Kirkman would not comment on whether Xcyte plans additional moves to conserve cash. In March, the company laid off 26 workers and dropped two other cancer-treatment programs.

Kirkman said the company hopes to start by year’s end an early-stage clinical trial of its HIV treatment, which it can do with its existing resources.

He said the company believes that boosting a patient’s infection-fighting T cells, an effect that has been seen in more than 100 cancer patients, could be useful in helping people with HIV.

A study also found that HIV-infected monkeys taking the company’s Xcellerated T cells and antiretroviral therapy were able to remain disease free, even for a year after the therapy ended.

David Miller, president of Biotech Monthly, a Seattle-based newsletter, said HIV would be difficult to pursue. Xcyte’s technique, an intricate process of stimulating a person’s own T cells, costs more than $4,000 per patient in raw materials, making it too expensive for the developing world.

The potential market is still large in the U.S. and Western Europe, but many funding agencies, like the Bill & Melinda Gates Foundation, are more interested in developing treatments for the developing world, where HIV is more widespread.

Luke Timmerman: 206-515-5644 or ltimmerman@seattletimes.com