Waiting Game for Life-Extending Prostate Drug

Patients waited years for extra studies on unique cancer drug Provenge.

April 26, 2010, 6:28 PM

April 28, 2010— -- Men with severe prostate cancer were given a flicker of hope for a new treatment after the U.S. Food and Drug Administration voted unanimously that a vaccine therapy was safe, and voted 13-4 that substantial evidence exists suggesting that it is effective in treating prostate cancer.

That was three years ago.

But Instead of approving the drug, called Provenge, back in 2007, the FDA sent researchers back to do more studies.

But now, the long delayed vote to approve the drug for use could be days away.

Dr. David Penson, a researcher on the original Provenge studies, said the FDA questioned the curious results of the clinical trials of Provenge.

Provenge didn't perform well on the researchers' goal or "primary endpoint" to slow cancer's growth, Penson said, yet a subset of patients on the treatment lived several months longer than patients on placebo.

"A lot of patients were hopeful in 2007 that the FDA would say 'we don't usually take a secondary endpoint [living longer], but we will here,'" said Penson, professor of urologic surgery, at Vanderbilt University in Nashville, Tenn. "They [FDA] had their responsibility to the public and they were conservative... no use crying over spilled milk."

Penson said a larger study, of 500 men with metastasized, hormone-resistant prostate cancer confirmed the earlier finding that Provenge extends life by an average of four months. Men with that stage of prostate cancer usually have only one treatment option left -- a drug called Docetaxel, which has a "fair number" of side effects compared to Provenge.

Now the FDA is posed to make a final decision on whether Provenge is safe and effective enough for the U.S. market within a week. FDA spokeswoman Shelly Burgess said the FDA cannot comment on pending decisions and therefore could not comment for this article.

The drug is unusual not just for its ability to prolong life for some patients.

Provenge is also said to be the first prostate cancer therapy of its kind that works by overhauling and boosting the body's own immune system to fight cancer. Standard cancer treatments such as chemotherapy or radiation work by obliterating tissues -- mostly diseased but some healthy tissues as well.

Immune System May Be Trained to Fight Prostate Cancer

"It's not a miracle, but it's amazing that the immune system can still wake up even when a man has prostate cancer throughout his body," said Dr. Jonathan Simons, president and C.E.O. of the Prostate Cancer Foundation.

"In 1993 if you told someone that you could wake up the immune system to fight prostate cancer, they would have laughed you out of the room," said Simons.

About 18 years ago, Simons said scientists discovered that cells in our immune system called dendritic cells act as "detectives" that hunt down and identify potential invaders like cancer. The dendritic cells then "awake" or activate other cells in the immune system such at T-cells or B-cells to seek and destroy the cancer invaders.

Simons said it wasn't until 2000 that researchers believed the immune system of a person with severe prostate cancer could "wake up" and start to recognize the cancer as a disease.

As Penson explained, Provenge takes advantage of this new knowledge of the immune system to train a person's body to fight their cancer.

With Provenge a patient has blood drawn, and their white blood cells are separated from their red blood cells. The white blood cells are shipped to a specialized lab, and treated with antibodies that "train" the white blood cells to attack cancer.

"It has a survival benefit over placebo from 3-4 months," said Penson. "You know people look at me and say you know 3-4 months you're not curing anybody... but for someone who'd have 18 more months to live, you get 20 percent more life."

Several more months of life might is not a considered "home run," but the method of treatment and the small step in a new direction has prostate cancer advocates and other cancer researchers excited.

"All of us want to see home runs -- but the reality is we don't have something like that," said Dr. Nina Bhardwaj, director of the Tumor Vaccine Program at New York University Langone Medical Center in New York City. "Even in cancer when new chemo drugs are coming out if you can improve survival by 4-6 months, it's a big step."

New Drug Would Likely Be Expensive

Bhardwaj was not part of the research team behind Provenge.

"For the people who did survive those few months longer, it's obviously significant for them," said Bhardwaj. "It does provide tantalizing clues that cell based therapies can achieve that which, we would ordinarily see with drugs. And if these are patients who've had all the drugs and haven't responded, it is exciting."

However, as Bhardwaj predicted, this type of treatment will be expensive. Patients have to pay for the expensive process of extracting the blood, the processing of the blood and the transport of all the samples.

"Being individualized therapy like that makes it expensive -- just like the bone marrow transplant," said Bhardwaj.

A spokesman from Dendreon, the company that makes Provenge said the company "has not yet set the price, however we expect it will be similar to other novel biologics that prolong survival."

Other "novel biologics" run between $50,000-$100,000 for a course of treatment.

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