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Study Results Positive for New Cancer Drug Therapy for Prostate Patients

Posted on: Thursday, 17 February 2005, 09:00 CST

Feb. 17--Dendreon, a Seattle biotechnology company, has found in a small study that its experimental therapy can significantly extend lives of prostate-cancer patients who have failed on standard treatments.

It marks the first time in decades of research that a final-stage, placebo-controlled experiment has shown a cancer treatment can substantially prolong life by revving up the body's immune system.

Though the result appears promising, it comes with some caveats, outside experts said.

Dendreon found in a 127-patient study that after three years, 34 percent of patients were still alive after taking its Provenge treatment, compared with 11 percent on placebo. Half the Provenge patients were alive after 25.9 months, while half the patients on placebo survived 21.4 months or more.

The side effects with Provenge were mild by comparison to chemotherapy: fever and chills that generally lasted one or two days.

Prostate cancer is the fifth-leading cancer killer in the United States. It is expected to claim the lives of more than 30,000 men this year, according to the American Cancer Society.

"A therapy that prolongs life yet avoids the side effects of other therapeutic approaches is clearly attractive to patients and physicians," said Dr. Eric Small in a statement. Small, a urologist at the University of California, San Francisco, School of Medicine, will present the results Saturday at an American Society of Clinical Oncology symposium in Orlando, Fla.

As Wall Street anticipated the news yesterday, Dendreon's stock surged 15 percent on heavy volume.

The 127-patient study, of men who didn't respond to hormone therapy, found that Provenge's benefits extended to patients with aggressive disease as well as those with slower-growing tumors, Dendreon said yesterday.

Previously, analyzing the same patient group after a shorter period, Dendreon had said the benefit was found primarily in the group with less-aggressive tumors.

Another study has muddied the picture further. That 98-patient trial showed Provenge was unable to slow disease, regardless of tumor aggressiveness. Even so, for reasons that aren't fully understood, the company said last month that trial is confirming that Provenge offers a survival advantage after 30 months of follow-up.

The final three-year analysis of that trial will be completed later in the year. Dendreon Chief Executive Mitchell Gold said that if the second trial confirms the survival advantage of the first, Dendreon may combine them in an application for federal approval, instead of waiting months longer to see how another trial now under way turns out.

If it gets the Food and Drug Administration's green light, Dendreon could become the first company to deliver to the market a so-called cancer vaccine to stimulate the immune system, possibly in 2006.

"This is the strongest evidence yet that says Provenge is an effective drug," Gold said.

The treatment has numerous skeptics. Dr. Patrick Walsh, a Johns Hopkins University urologist and a well-known prostate-cancer surgeon, said the study was too small to draw definitive conclusions. He said it's unknown what other therapies patients may have had during the three-year follow-up period, which may have made a difference.

"The numbers here are just too small to make this a big deal," Walsh said.

Dr. Howard West, an oncologist at Swedish Medical Center, said it would be a stronger statement if the survival edge was seen across a larger number of patients. Still, he called the finding "extremely intriguing."

West has studied Provenge in another setting but was not involved in this trial.

"It's always appealing to have an option that's less toxic and can meet meaningful clinical [goals] like patient survival," West said.

If Provenge becomes a success, it could usher in a new style of cancer treatment beyond chemotherapy, radiation and surgery.

Here's how it works: A patient gives blood, and some of the most potent immune-system cells are fished out in a lab procedure. The cells are incubated with a genetically engineered protein, PAP, found on prostate-cancer cells.

During 36 hours, the cells are "taught" to recognize PAP as an invader, like a virus, that must be attacked by the body's immune defenses. They are then reinfused into the patient to charge up the immune system.

The technique has proved extraordinarily difficult to master, partly because cancer cells have many genetic similarities to normal cells, which the immune system does not attack.

If Dendreon reaches the market, it will have to compete with the largest of pharmaceutical companies. Study results for Taxotere, a common chemotherapy drug, showed last year it could produce a median survival advantage of 2.4 months in the same population of terminal prostate-cancer patients.

David Miller, president of Biotech Monthly, a Seattle-based industry newsletter, said Taxotere's results were well-received at last year's annual meeting of cancer doctors, and many oncologists remain skeptical about Provenge.

The trial results being presented this weekend will surely not be the final verdict on Provenge, said Miller, who owns shares in the company.

"If people judge it fairly, you have to keep an open mind that Dendreon's data could represent a significant advance in cancer treatment."

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DNDN,

Source: The Seattle Times

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