The U.S. Food and Drug Administration approved a new prostate cancer treatment Thursday. The treatment, which works by turning the body’s immune system against invading cancer cells, is called Provenge and is manufactured by Seattle biotech firm Dendreon. According to a story that ran on the front page of the Seattle Times this past Sunday, researchers at Dendreon have spent 18 years and nearly $750 million developing what they tout as another type of cancer “vaccine.”
FDA approval was based on a clinical trial of 500 men with advanced prostate cancer that had metastasized to other parts of the body. As Sandi Doughton writes for the Seattle Times, three years in, nearly one third of men who had been given Provenge were still alive, compared with fewer than 25% of those who took a placebo. Doughton explains: “The vaccine boosted median survival time by 4 months, from 22 months in the placebo group to 26 months in the Provenge group.”
So, how does this new “vaccine” work? Not like other vaccines—which work by prompting the immune system to create antibodies by either exposing it to damped down (attenuated) versions of a live microorganism, or dead microorganisms. To oversimplify quite a bit: with Provenge vaccination begins with a blood draw. Blood is then sent to the lab, where technicians extract immune cells known as antigen presenting cells (APCs) from the sample. From here, Dendreon combines the immune cells with proteins that are prevalent on the surface of prostate cancer cells. An immune boosting substance is also added into the mix. Exposure to the cancer proteins and immune booster spurs the APCs into action—and the prostate cancer proteins move to the surface of the “activated” cells. At this point, the activated APCs are pumped back into the patient’s blood stream.
Part of what makes cancer so difficult to treat is that the immune system doesn’t react to cancer cells as it does to other infections or viruses—as invaders that should be routed out. The goal of the Provenge treatment is to change that. Once the activated APCs are back in the patient’s blood stream, they come into contact with T-cells (the white blood cells that generally “seek and destroy” any unrecognized bugs). In turn, those T-cells become activated—they now recognize tumor cells as bad guys, and set out on the hunt, replicating more cancer-munching T-cells along the way.
Patients receive the treatment intravenously in a series of three doses spread out across several weeks. According to early estimates, because of its labor intensive, patient-specific nature, Provenge will likely cost between $50,000 to $75,000. (In anticipation of the FDA announcement, Dendreon shares jumped by 19%, the AP reports.)