Dendreon's Cancer Drug Backed by Advisers to U.S. FDA (Update2)
By Luke Timmerman
March 29 (Bloomberg) -- Dendreon Corp.'s prostate cancer drug Provenge was recommended for U.S. approval as the first treatment to stimulate the body's immune system against tumor cells.
Advisers to the U.S. Food and Drug Administration voted 17-0 today that the medicine is safe and 13-4 that it's ``substantially effective'' based on clinical trials so far.
Provenge would be Dendreon's first approved product and could generate as much as $1 billion a year in U.S. sales, analysts say. The drug, designed to train the body's immune system to fight prostate cancer as if it were a virus, would provide a new treatment for a disease that kills 27,000 men a year in the U.S.
``This is the first demonstration that a vaccine approach can prolong survival,'' said Philip Kantoff, an oncologist at Dana Farber Cancer Institute in Boston, in a telephone interview March 26. ``It will fuel an incredible amount of enthusiasm for investigation of this approach in prostate cancer and other tumors.''
The FDA generally follows the recommendations of its advisory panels, although it isn't required to do so. The agency has set a May 15 deadline to act on the Provenge application, according to Dendreon.
Trading in shares of Seattle-based Dendreon was halted today because of the FDA meeting. The shares gained 41 percent in the five days leading up to today's vote, on volume more than five times the three-month average.
Investors also have been betting that Provenge would fail. About 26 million shares were held in a short position in March, more than twice the number in December, according to data compiled by Bloomberg. People who sell short try to profit by borrowing stock and repurchasing the securities later at a lower price to return to the holder.
Patient Advocates
``What this says to the FDA is that the drug has value to patients,'' said Mitchell Gold, Dendreon's chief executive officer, in an interview after the advisory panel's vote.
Provenge can provide hope for those whose advanced cancer can't be helped by other treatments, representatives of patient advocacy groups told the panel.
``Men are begging for anything else that can save their life, and their quality of life,'' said Jim Kiefert, a 17-year prostate cancer survivor from Olympia, Washington, and chairman an organization called Us Too.
`Doubts Remain'
The FDA's staff said in a report March 27 that ``doubts remain'' about the drug's effectiveness, and much of the panel's discussion today turned on that question.
One of the FDA advisers, Howard Scher of Memorial Sloan Kettering Cancer Center in New York, asked how Dendreon could be confident Provenge would prolong the lives of the 55,000 men with advanced prostate cancer, based on small studies of 225 men.
``If one or two patients shift, suddenly you can lose significance,'' Scher said.
The panel must make its decision on ``less than perfect data,'' said Brent Blumenstein, Dendreon's statistical consultant. Dendreon's trials were statistically sound, and showed benefits for all groups of patients, unlike many cancer drugs, he said.
Trial Results
The first trial submitted by Dendreon of 127 men showed that patients on Provenge lived a median 25.9 months, compared with 21.4 months for those on a placebo. The second trial, of 98 men, was designed to be identical, the company said. It showed a median survival of 19 months for Provenge patients.
The difference ``might be attributable to chance,'' the FDA staff said in its analysis. ``Doubts remain about the persuasiveness of the efficacy data.''
Provenge appeared to be ``generally well-tolerated'' for prostate cancer patients, the FDA staff said. Of the 147 patients on the drug in two pivotal trials, eight had strokes, which is a ``potential safety concern'' the staff said. The most common side effects were fever and chills that lasted one to two days, according to the company.
How it Works
The drug, called an immunotherapy, doesn't work like a traditional cancer treatment. Blood is drawn from a patient, and some white blood cells vital to the immune system are separated in a lab.
The white blood cells are shipped to the company and incubated with a genetically engineered protein found on prostate cancer cells. The white blood cells are supposed to recognize the protein as an invader and attack the cells that contain it. The revved-up white blood cells are then shipped back and re-infused into the patient.
Dendreon failed to demonstrate in trials that Provenge could slow the cancer's progression, the primary statistical goal of the studies. The company has said that may be because it can take weeks for Provenge to charge up the immune system.
Doctors see a promising combination in Provenge's survival edge and its mild side effects, said Neal Shore, a prostate cancer specialist with Carolina Urologic Research Center in Myrtle Beach, South Carolina.
Another Treatment
The other treatment recently approved for prostate cancer, Taxotere, a chemotherapy drug, improved median survival by 2.4 months, with more harsh side effects than Provenge, Shore said.
``Nothing out there compares to Provenge,'' he said in a telephone interview March 21. Shore is an investigator on a continuing Dendreon-sponsored study.
Provenge could have U.S. sales of more than $1 billion a year if it's approved by the FDA, said David Miller, president of Biotech Stock Research, an independent equity research firm in Seattle. Miller owns shares.
To contact the reporter on this story: Luke Timmerman in San Francisco ltimmerman@bloomberg.net .
Last Updated: March 29, 2007 17:22 EDT |
