Cancer Research Lab

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 immune response to cancer. It targets the prostate cancer antigen, prostatic acid phosphatase (PAP), which is found in approximately 95% of prostate cancers.

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.

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.