SEATTLE ( TheStreet) -- Dendreon ( DNDN) has received full approval for its prostate cancer "vaccine" Provenge from the U.S. Food and Drug Administration, the agency said Thursday.

Dendreon shares closed Thursday up 26% to $50.18. The stock was halted for a time at $45.50 soon after the announcement hit the tape.

Provenge becomes the first cancer drug approved that works by activating a patient's own immune system to fight the disease. Under the FDA approval, Dendreon will market Provenge as a treatment for men with advanced prostate cancer that has grown resistant to standard hormone treatment.

"The FDA approval of Provenge is a testament to the courage of the patients and researchers who participated in our studies and is the culmination of nearly 15 years of research and development by our dedicated employees," said Dendreon CEO Mitch Gold, in a statement.

Provenge was approved based on a pivotal study in 512 men demonstrating that treatment with Provenge could extend survival by 4.1 months compared to patients not treated with Provenge.

"The availability of Provenge provides a new treatment option for men with advanced prostate cancer, who currently have limited effective therapies available,” said Dr. Karen Midthun, acting director of the FDA's Center for Biologics Evaluation and Research, in a statement.

Dendreon's struggles to bring Provenge to market have been long documented. An FDA advisory panel in 2007 recommended Provenge's approval but the FDA later decided to request more clinical data. Dendreon then ran another clinical trial that produced positive results in April 2009 and allowed the company to refile Provenge with FDA.

Dendreon is expected to treat its first prostate cancer patient with Provenge in the nect week. The company announced a Provenge treatment price of $93,000, well above Street estimates. Analysts have estimated the drug could generate $1 billion or more in U.S. sales, but that forecast may rise now given the higher Provenge sales price.

The commercial launch of Provenge will be closely watched because the drug is no ordinary off-the-shelf cancer drug. Instead, Provenge is personalized for each individual prostate cancer patient. This adds a logistical complexity to the manufacture and delivery of Provenge that could cause Dendreon some problems, or at least some sleepless nights, in the first days and weeks of the drug's launch. Wall Street will be watching the Provenge launch closely.

-- Reported by Adam Feuerstein in Boston.

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Adam Feuerstein writes regularly for TheStreet.com. In keeping with TSC's editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet.com. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.

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