Survival extended by Dendreon cancer vaccine

NEW YORK (Reuters) - An experimental cancer vaccine developed by Dendreon Corp improved three-year survival of patients with advanced prostate cancer by 38 percent compared with a placebo, according to data from a closely watched study unveiled on Tuesday.

Patients in the 512-subject study who received Dendreon's Provenge lived an average 4.1 months longer than those who received a placebo in the late-stage clinical trial, researchers said.

Patients lived 25.8 months after receiving the vaccine compared with 21.7 months for those taking placebos.

"This is a game changer in my business," said Dr. David Penson, associate professor of urology at the University of Southern California, who presented the data at the American Urological Association meeting in Chicago.

"I have no doubt that if this drug becomes commercially available in the United States, it will replace chemotherapy" in this patient population, Penson said in a telephone interview.

The results further raise the likelihood that Provenge will become the first approved therapeutic vaccine for any type of cancer. Dendreon plans to seek U.S. approval of Provenge, known chemically as sipuleucel-T, in the fourth quarter.

Penson called the data convincing and predicted that "it will reinvigorate cancer vaccine therapy," a field that had previously been littered with failures.

"The headline data looks solid. This meets the definition of unambiguous. It met the primary endpoint and the safety looks good," said Paul Latta, an analyst with McAdams Wright Ragen. "People ought to be pleased by this result."

Earlier this month Dendreon said Provenge achieved the main goal of this study, which was reducing the overall risk of death by at least 22 percent compared with a placebo. The announcement more than doubled the price of the company's heavily shorted shares.

Dendreon shares were halted after they plunged 45 percent to $11.81 on Nasdaq in the hour leading up to release of the study results. They were trading as low $2.55 in early March.

"I feel sorry for whoever sold it right before the news came out," Latta said. "The stock is likely to regain what it lost and then some."

Nasdaq said it was investigating "potentially erroneous" Dendreon transactions.

Details of the study, which showed the vaccine reduced risk of death by a statistically significant 22.5 percent, were not made public until the presentation at the urology meeting.

Prostate cancer is the most common cancer in American men aside from skin cancers, according to the American Cancer Society. About one in six men will be diagnosed with prostate cancer during his lifetime.

Unlike traditional vaccines that prevent disease, Provenge treats it by stimulating the body's own immune system to attack cancer cells. If approved Provenge, which is administered in three doses at two-week intervals, would be the first cancer immunotherapy on the market.

Adverse events seen in patients taking Provenge were chills, fever and headache that lasted one to two days following infusion, which is a huge advantage over the debilitating side effects typically seen with chemotherapy.

"This drug is the best tolerated (cancer) drug I've seen," Penson said. "These guys would get the drug on Thursday or Friday and be out playing golf on Saturday or Sunday."

The drug could have been available to patients with late-stage prostate cancer considerably sooner. But the Food and Drug Administration insisted that this study must first confirm earlier results as a condition of approval, despite a March 2007 recommendation from one of its own expert advisory panels that it be approved.

"Let's get it approved and get it out to help patients," Penson said.

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