After 15 years of research and a roller-coaster ride at the U.S. Food and Drug Administration (FDA) that went on for several years, sipuleucel-T (Provenge) recently became the first cancer vaccine ever approved by the FDA, ushering in a new era in the ongoing war on cancer.
Vaccines have long been the dream of cancer researchers for more than a century. Although sipuleucel-T is not
a cure for metastatic prostate cancer, it is the first therapeutic vaccine to win FDA approval, which is certainly
reason to cheer. Similar experimental therapeutic vaccines are currently in various testing phases for other cancers, including lymphoma, lung, and breast cancer.
Prostate cancer is now the second leading cause of cancer death in American men, behind only lung cancer.
Surgery and radiation therapy can cure prostate cancer, but once it spreads to the bones, the disease is often
incurable. In the United States, prostate cancer is expected to kill more than 32,000 men each year. Hormonal
therapy and chemotherapy are commonly used to slow metastatic growth of hormone-sensitive prostate cancer
tumor cells and this strategy generally controls the disease for variable time periods until the hormone-resistant cells proliferate and progress. Once the disease develops resistance to hormonal therapy and chemotherapy, historically there have been limited therapeutic options.
Now there is sipuleucel-T. Unlike a traditional preventive vaccine (such as a flu or measles vaccine) that revs up the immune system to help prevent infection, sipuleucel-T is a novel option, a therapeutic vaccine given to men with advanced prostate cancer to get their own immune systems to develop an immune response against the disease, leading to improvement in survival.
The new vaccine works differently from other prostate cancer drugs. Dendritic cells, a type of immune cell, are first removed from the patient and then exposed to prostate cancer cells in a laboratory. The goal is to have these specially treated cells seek and destroy the circulating tumor cells throughout the body when they are finally infused back into the patient several days later. The process is repeated two additional times to complete the entire treatment cycle.
Dendritic cells are the master controllers of immunity: They alert T-lymphocytes—a type of white blood cell—to the presence of foreign intruders within the body. These cells patrol the body, and when they encounter something that should not be there (such as cancer cells), they can process proteins from these invaders and present them to the T-cells. The T-cells in turn use these foreign proteins as a means of “recognizing” the foreigner and setting in motion the immune recognition and destruction of the invader.
With this new prostate cancer vaccine, doctors hope that the dendritic cells will trigger a cascade of events that leads to an immune response that eventually destroys all rogue prostate cancer cells. In a pivotal Phase III clinical trial reported in the New England Journal of Medicine, sipuleucel-T was found to extend the lives of patients with advanced, metastatic, androgen-independent prostate cancer by an average of four months when compared to patients given a placebo, reducing the risk of death by 24%. It’s now hoped that men will derive greater benefit when the drug is given earlier in the course of the disease, or when combined with other medications.
Sipuleucel-T is the first vaccine to demonstrate a survival benefit. This is certainly encouraging news, especially for avaccine whose only side effects are mild fever and body aches shortly after vaccination.
Where Are They Now
As of a 2016 update Sipuleucel- T is the only vaccine approved to treat cancer and is used specifically for prostate cancer that can no longer be treated by hormone therapy. The vaccine does not cure cancer but has been proven to extend patient lives by several months with the assistance of chemically exposed immune cells, called dendritic cells.