Dendreon Prostate Vaccine Boosts Survival

Dendreon's controversial Provenge cancer vaccine may get another chance two years after the FDA rejected it. The drugmaker's stock soared on the news

Dendreon Corp. (DNDN) jolted the cancer community, and the stock market, on Apr. 14 with an announcement that a medical trial has shown that its experimental Provenge vaccine for prostate cancer can keep men alive longer than standard treatments. "The results were unambiguous," Dendreon CEO Mitchell Gold told BusinessWeek. The news raised the possibility that Provenge might become the first cancer vaccine approved for use in the U.S.

Dendreon's stock price soared, tripling at one point from the previous day's close of 7.30 to a high of 22.10 in morning trading. The stock closed at 16.99.

Provenge has divided cancer specialists and industry analysts ever since the Food & Drug Administration unexpectedly rejected the drug in May 2007, ignoring the recommendation of its own panel of outside experts. Although the panel said then that the drug was safe and potentially effective, based on the mixed results of a 127-patient trial, the FDA wanted more proof.

Larger Clinical Trial

That rejection set off a storm of demonstrations and lawsuits against the agency from cancer patients who wanted access to the drug, and from Dendreon investors angry about the nosedive in the company's stock.

But Seattle-based Dendreon was willing to try again and mounted a larger, more rigorous clinical trial in an effort to meet the agency's burden of proof—namely, that the drug could extend survival. Details of that later, 512-patient trial will not be released until a medical meeting on Apr. 28. But Gold said the trial met its goal, which was to reduce the risk of death in patients with advanced prostate cancer by at least 22%.

"They said some words that I really like: unambiguous, overall survival, and prespecified [end points], " said Mark Monane, analyst with Needham & Co. "I think this is very encouraging news for the drug."

Dendreon plans to refile for approval with the FDA toward the end of this year. If Provenge wins U.S. approval, it will be the first new drug for advanced prostate cancer since 2004, and only the second in more than a decade. There are only three drugs available for advanced prostate cancer, a disease that kills some 29,000 men a year in the U.S. The few treatments for prostate cancer are extremely toxic, and often leave patients incontinent and impotent.

"Results Are Quite Exciting"

If approved, analysts predict that Provenge could have initial annual sales of $200 million a year, and that sales could eventually exceed $1 billion. The drug, which is administered only once, is also likely to be costly, although the company has yet to release any pricing details.

Dendreon could also wind up being the first anticancer vaccine to win FDA approval. Provenge is one of a number of so-called immunotherapies in development that try to stimulate the body's immune system to attack cancer cells and prevent the disease from recurring. It is a controversial approach that scientists have been pursuing for decades, with little to show for their efforts. Only one such vaccine has won approval anywhere in the world, Antigenics' Oncophage, approved in Russia a year ago. Just a few months ago Cell Genesys shut down development of a prostate cancer vaccine, GVAX, which was once thought to be among the most promising of the group, after it failed to show a survival benefit.

This time, "the results are quite exciting," said Dr. William Oh, director or genital urinary oncology at Dana-Farber Cancer Institute in Boston, "I do think this may offer a new strategy." And the size should make the results reliable, he said.

The stocks of a number of other companies developing cancer vaccines shot up Apr. 14 as well, riding Dendreon's coattails. That included Antigenics (AGEN), whose Oncophage vaccine for kidney cancer is waiting a decision from the European Union following its approval in Russia. Antigenics CEO Garo Armen said the Dendreon data is "a small step in a giant wave of things to come" in the cancer-vaccine field. The Dendreon results "are a major milestone," he said.

Proving Survival

Provenge did show a survival benefit in the trial presented to the FDA two years ago, with 34% of the men who received the drug still alive after three years. That compared with 11% of those in the control arm. The drug also showed very few side effects, so an expert panel voted 13 to 4 that there was "substantial evidence" that Provenge worked. But because that trial enrolled only 127 patients and did not shrink the tumor, the end point of that trial, the FDA rejected the drug.

The new trial was only designed to prove survival, which is what the agency requested. It was not designed to show tumor shrinkage. Thus Dendreon CEO Gold said he believes the company will give the FDA what it wants.

"It meets the protocols set forth by the FDA," he said. As for the roller coaster he and his company have been on the last two years—the stock was down to 2.55 in March—Gold waxed philosophical: "I think innovative, meaningful science is often the most controversial."

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