The Food and Drug Administration (FDA) on Thursday approved Provenge, a new treatment for prostate cancer that was originally developed by Stanford researchers in the 1990s.

“This is extraordinarily important,” said Edgar Engleman, who first devised the immune cell therapy. “This is the first time that an immunotherapeutic approach has been [moved forward].” Engleman is a professor of pathology and medicine at the Stanford School of Medicine.

The FDA denied approval for the approach in 2007 and requested more data from Dendreon, the biotechnology company that produces Provenge. After a third clinical trial, the FDA finally gave Provenge the go-ahead.

“The firm then filed an amendment to its [application] to include the new data and the FDA has now completed review of that submission,” said the FDA’s Jill Burkoff, “and based on FDA’s review, we’ve determined that the product is safe and effective.” Burkoff is a consumer safety officer at the FDA’s Center for Biologics.

Provenge uses the body’s immune cells to recognize and fight cancer, which cells usually do not recognize as a foreign threat. The therapy is not preventative like traditional measles or tetanus vaccines; rather, it targets existing advanced-stage cancers.

The therapy involves isolating the dendritic cells, a type of immune cell, from each individual cancer patient and bringing them to a lab. In the lab, the cells are introduced to cancer components and manipulated to recognize them as non-self. When reintroduced to the patient, they then target and fight the cancer.

“In a sense we are kind of fooling the dendritic cells into thinking the cancer is foreign,” Engleman said.

Because the immune cell therapy is genetically the same as the patient’s own cells, they are nontoxic and have few side effects. Chemotherapy and other cancer treatments are extremely toxic and end up killing other cells in the patient, often causing debilitating side effects.

According to Engleman, “the dendritic cells” approach to cancer therapy is appealing because it “appears to be very, very safe.”

Now, after years of waiting, Dendreon is ready to turn the drug into a clinical reality.

“The approval of Provenge is a significant step towards realizing our mission of transforming the lives of patients with cancer, and it also marks Dendreon’s transformation into a commercial enterprise, ready to support the successful launch of the first personalized treatment for cancer,” said Mitchell H. Gold, the CEO of Dendreon, in a press release.

Engleman and his colleague Samuel Strober, professor of medicine, formed Dendreon in 1992 to bring their cell therapy through the clinical trials process and market it for therapeutic purposes. The firm began clinical trials in 1998.

When Dendreon applied to the FDA for approval in 2007, the expert advisory panel recommended that the FDA approve it. The FDA, however, wanted to pursue further research.

“The agency determined that there were deficiencies in the application that precluded approval,” Burkoff said.

Dendreon said it will offer 2,000 patients a supply of the therapy for 2010-2011. Provenge will be provided through 50 centers that originally participated in the clinical trials.

Dendreon is estimated to have spent approximately $1 billion developing the drug. The therapy will cost approximately $93,000.

“It is, by definition, a very expensive process,” Engleman said. “In this case, you basically have to manufacture your treatment for each patient every time. I think this will be a factor that limits accessibility.”

Dendreon and many other companies are currently employing the technique to treat other types of cancer.