April 14 (Bloomberg) -- Dendreon Corp.'s method for stimulating the immune system against prostate tumors may also help people fight certain types of breast, ovarian and colorectal cancers, researchers said.

The treatment, APC-8024, triggered an immune reaction against tumors, and two of 11 breast cancer patients had their disease stabilize for almost a year after other treatments failed, researchers said today at a medical meeting.

Dendreon, based in Seattle, lost almost $1 billion in market value in May, when the U.S. Food and Drug Administration delayed its application to market Provenge for prostate cancer patients. The company's second candidate mimics excess HER2 proteins, which affect growth of cancer cells, in the body, and is designed to teach the body's immune system to fight them like a virus. Dendreon has invested in Provenge, and hasn't advanced its other drug into late-stage testing.

``The data once again highlights the long-lasting effect of cancer immunotherapy in responding patients,'' said Michael King, an analyst with Rodman & Renshaw in New York, in a note to clients. ``Dendreon's platform technology has the potential to be applied broadly.''

The study confirmed the results from another trial of 18 patients that APC-8024, also known as Neuvenge, can stimulate the immune system after eight and 16 weeks, said Mark Frohlich, Dendreon's chief medical officer, in a telephone interview. The company plans to move the product forward in development after it receives what it expects will be positive data about Provenge in the second half of 2008, Frohlich said.

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Dendreon fell 1 cent to $5.27 at 4 p.m. New York time in Nasdaq Stock Market composite trading.

The findings were presented today at the American Association for Cancer Research in San Diego.

Researchers enrolled 18 patients with cancers that have amplified HER2 proteins, present in people with breast, ovarian and colorectal tumors. The patients had relapsed after standard chemotherapy, hormones or doses of Genentech Inc.'s Herceptin.

Patients took three infusions of APC-8024 in a month. The treatment is designed to work like Provenge, and unlike any marketed drug. Blood is drawn from a patient, and some white blood cells vital to the immune system are separated in a lab.

The white blood cells are shipped to the company and incubated with a genetically engineered protein found on cancer cells. The white blood cells are supposed to recognize the protein as an invader and attack the cells that contain it. The revved-up white blood cells are shipped back and re-infused into the patient.

Two of 11 patients with breast cancer, whose disease had spread, had their tumors stabilize on the Dendreon treatment, for 49 weeks and 72 weeks, respectively. Researchers at the University of California, San Francisco and Mayo Clinic in Rochester, Minnesota didn't see any cases of tumor shrinkage. Side effects, which included fatigue and chills, were generally mild, researchers said.

To contact the reporter on this story: Luke Timmerman in San Francisco at ltimmerman@bloomberg.net

Last Updated: April 14, 2008 16:02 EDT