FDA advisers back Dendreon's prostate-cancer drug

Dendreon's prostate-cancer drug won the recommendation of a U.S. Food and Drug Administration advisory panel Thursday, an outcome that should help the Seattle biotech company in its bid to win approval of the drug.

But a last-minute change in the wording of the panel's endorsement suggests to at least one analyst that the potential blockbuster drug, Provenge, still faces uncertainty when the FDA makes its ultimate decision by May 15.

The agency typically follows the guidance of its outside group of advisers, though it's not required to do so.

The committee, made up of experts in cell and gene therapy, agreed unanimously that Provenge was safe. In a 13-4 vote it concluded the drug was "substantially effective."

Provenge is intended as the first treatment of its kind to stimulate a patient's own immune system against prostate cancer. If it's approved, Dendreon will become the only Seattle-based biotech company with a marketable drug that analysts predict could generate up to $1 billion in annual sales.

"It was all across the board a really great day for cancer patients, a great day for the field of immunology and a great day for Seattle," said Dr. Mitchell Gold, president and CEO of Dendreon in an interview after the panel vote.

Trading of Dendreon was halted Thursday because of the meeting. Shares of the company climbed 13 percent to close at $5.22 Wednesday in anticipation of the meeting in Gaithersburg, Md.

Over the last five trading days, the company's shares gained 41 percent.

Jonathan Aschoff, senior biotechnology analyst with Brean Murray Carret, in New York, said he doesn't think the panel members would have approved Provenge for effectiveness if not for a "substantial" rewording of the question on which they voted. Aschoff does not own shares of Dendreon.

The original question posed to the panel was, "Does the submitted data establish the efficacy" of Provenge? But during the voting, several members said they were having trouble with the meaning of "establish." That may have been a reflection of the mixed results Provenge showed in clinical trials.

So the question was changed to ask whether the data showed the drug was "substantially effective." That weaker formulation won a strong majority.

In two studies, the company failed to demonstrate the drug could slow the progression of prostate cancer, the No. 2 killer of men in the United States. However, in a three-year analysis of 127 men with late-stage cancer, the median survival time for patients receiving Provenge was 4.5 months longer than patients taking a placebo.

After three years, 34 percent of the men taking Provenge were still alive, compared with 11 percent on the placebo.

Aschoff doesn't think the FDA will ultimately approve Provenge and has been advocating a "sell" since 2004.

"I haven't spoken to a single institutional investor that said they were going to buy this stock [Friday]," said Aschoff.

David Miller, president of Seattle-based Biotech Stock Research, said the panel went as he expected. He's optimistic Provenge will be approved.

Public testimony by cancer patients was a pivotal point in Thursday's daylong meeting and helped the panel better understand the unmet need for therapy for late-stage prostate cancer, said Dr. Celestia Higano, associate professor of medicine and urology at the University of Washington and the Fred Hutchinson Cancer Research Center in Seattle.

Higano was the local investigator on one Provenge trial and was at the panel meeting.

Prostate-cancer advocates, patients and their families gave emotional testimony on their struggles with the disease, which kills about 27,000 men a year in the United States, according to the American Cancer Society.

Provenge would be the first so-called immunotherapy to treat cancer.

Scientists take a patient's own white blood cells, mix them with a genetically engineered protein and reintroduce them into the patient.

Currently, advanced-stage patients often feel forced into chemotherapy and its side effects because there are no other treatment options that affect survival, said Higano. Side effects of Provenge have generally been fever and chills, although it's been shown to have a risk of stroke.

"This opens up a new option that shows some survival benefit," Higano said.

Steve Fleischmann, a Seattle prostate-cancer patient and advocate, spoke at the hearing at Dendreon's invitation.

Fleishmann, 51, recently learned his cancer had returned after being in remission for 3-½ years. He will soon start radiation treatments.

"If this drug doesn't get approved, then what? What do I face?" said Fleishmann, who has not participated in any of the clinical trials.

Even though it has the recommendation of the panel, Dendreon could still have trouble winning FDA approval.

It's possible the FDA would grant the company an "approvable" status and require it to finish a third, ongoing clinical study. That study is enrolling 500 patients and won't produce results until 2010.

Kirsten Orsini-Meinhard: 206-464-2391 or kmeinhard@seattletimes.com