The US Food and Drug Administration (FDA) on Thursday approved a new therapy for certain men with advanced prostate cancer that uses their own immune system to fight the disease; although described as a “vaccine” the new therapy, called Provenge, treats rather than prevents prostate cancer.

In a statement the manufacturer, Seattle-based Dendreon Corp, described Provenge (sipuleucel-T) as the first therapy in a class known as “autologous cellular immunotherapies”, marking a significant step in personalized treatment for cancer.

According to Dendreon, Provenge is designed to treat:

“… asymptomatic or minimally symptomatic metastatic, castrate-resistant (hormone-refractory) prostate cancer (CRPC).”

Dr Karen Midthun, acting director of the federal agency’s Center for Biologics Evaluation and Research, explained that Provenge offered:

“A new treatment option for men with advanced prostate cancer, who currently have limited effective therapies available.”

In the US, prostate cancer is the second most common cancer in men, after skin cancer, and mostly affects older men.

According to figures from the National Cancer Institute, last year in the US there were some 192,000 new cases of prostate cancer and 27,000 deaths to the disease.

Provenge stimulates the patient’s own immune system to fight the disease by inducing an immune response against prostatic acid phosphatase (PAP), an antigen expressed in 95 per cent of all prostate cancers.

Each patient receives his own tailored version of the “vaccine”, made using immune cells extracted from his own blood that are then exposed to the cancer protein and bound with an immune system stimulant. The treated cells are then returned to the patient in a three-dose schedule given intravenously at about two-week intervals.

Provenge was tested in a randomized, double-blind, placebo-controlled, multicenter trial involving 512 CRPC patients. Patients receiving the new treatment showed an increase in overall survival of 4.1 months, with a median survival of 25.8 months compared to 21.7 for the group not receiving it.

Nearly all participants had an adverse reaction of some kind, most of which were mild or moderate and included chills, fatigue, fever, back pain, headache, joint ache, and nausea.

However, about 1 in 4 patients had a serious adverse reaction to Provenge, including acute infusion reactions and stroke.

Dr Mitchell H Gold, president and chief executive officer of Dendreon, praised the patients, researchers and employees who have made it possible for Provenge to win FDA approval:

“The FDA approval of PROVENGE is a testament to the courage of the patients and researchers who participated in our studies and is the culmination of nearly 15 years of research and development by our dedicated employees,” said Gold.

The FDA approval of Provenge may well spur more “vaccine” treatments for cancer.

Reuters reported yesterday that other manufacturers are also looking at or developing similar treatments: GlaxoSmithKline is said to be studying one for lung cancer, Bristol-Myers Squibb is developing one for melanoma, and the Danish biotech company Bavarian Nordic is said to be in the final stages of testing a rival to Provenge called Prostvac.

Dr Len Lichtenfeld, deputy chief medical officer at the American Cancer Society, told the news agency that the FDA approval of Provenge is “exciting because it does represent a proof of concept”.

Sources: FDA, Dendreon, Reuters.

Written by: Catharine Paddock, PhD