Dendreon Corp. showed that its novel cancer therapy Provenge is reasonably safe and provided "substantial evidence" it benefits men with advanced prostate cancer, U.S. advisers ruled on Thursday.
Provenge is a therapeutic cancer vaccine designed to stimulate the body's immune system to fight a diagnosed cancer. It differs from traditional vaccines that prevent infections in people not yet sick.
Two Dendreon studies failed to meet their main goal of slowing the progress of advanced prostate cancer, but one analysis found patients treated with the product lived about 4.5 months longer.
A U.S. Food and Drug Administration advisory panel debated whether the findings were convincing. Some said they felt uncomfortable answering the agency's initial question of whether Dendreon had "established" efficacy.
Members ultimately reworded the query and voted 13-4 that Dendreon had provided "substantial evidence" Provenge worked.
"I think new fields ... are hard to foray into if we wait until everything's perfect," said Sharon Terry, the panel's consumer representative and chief executive of the Genetic Alliance Organization.
Others said it was too early to conclude Provenge was effective and urged the company to complete a new, 500-patient study. Survival results from that trial are due in 2010, the company said.
Dendreon Chief Executive Mitchell Gold said the company has planned an interim look at that trial, which has so far enrolled 400 patients, and will be working with the FDA over the coming weeks.
"Does this drug prolong life? I just don't know at this point in time," said Dr. Howard Scher, a panel member and specialist in genitourinary cancers at Memorial Sloan-Kettering Cancer Center in New York.
'REASONABLY SAFE'
The panel unanimously said Provenge was "reasonably safe." Many panelists urged Dendreon to closely watch if strokes seen in some patients may have been linked to the therapy.
Prostate cancer will be diagnosed in 218,000 U.S. men in 2007 and kill 27,000, according to American Cancer Society estimates.
Dendreon studied men with advanced prostate cancer that had stopped responding to hormone therapy but was not causing pain. Life expectancy at that stage usually ranges from 14 months to 22 months, the company said.
One analysis of 127 men showed patients infused with Provenge lived about 4.5 months longer than others given a placebo, Dendreon said.
The company said Provenge, known generically as sipuleucel-T, was less toxic than chemotherapy for advanced prostate cancer. The most common side effects included mild to moderate chills, fever and headaches within a day or two of infusion.
The FDA is scheduled to decide by May 15 whether to approve Provenge for sale. The agency usually clears products that win positive recommendations from advisory panels.
CEO Gold said the company was "very pleased the committee recognized the value of Provenge to prostate cancer patients."
Wall Street analysts had largely expected a negative outcome from the panel review, with final approval hinging on the 2010 completion of the ongoing survival trial.
Paul Latta, an analyst at McAdams, Wright, Ragen, said the chance that the FDA will grant full approval to Provenge in May has now risen to between 50 percent and 60 percent, from a previous likelihood of 30 percent.
He estimated that sales of Provenge could reach $500 million a year if the vaccine is eventually cleared as a treatment for earlier-stage prostate cancer.
If Provenge wins FDA approval, it could give a boost to the emerging field of therapeutic cancer vaccines. Several companies including GlaxoSmithKline Plc are working on similar products.
Provenge is tailored for each person. White blood cells are filtered from a patient's own blood, mixed with a protein and infused back into the patient two days later. The mixture is designed to recognize tumors as foreign invaders and attack.
Gold said about 50,000 U.S. prostate cancer patients would be candidates for Provenge.
Trading in shares of Seattle-based biotechnology company was halted on Nasdaq while the panel met.
