Clinical trial to test prostate cancer vaccine

Needle with medication prepared for injection

If successful, a developmental prostate cancer vaccine may potentially trigger the body’s own immune system to kill deadly cancer cells. The treatment, called ProstAtak, is designed for newly diagnosed, localized prostate cancer.

“The problem with cancer is that it if you trace back its lineage, at one point it was a normal cell that went awry, and as it multiplies, it does so under the radar of the immune system so our body doesn’t create an immunity against it,” said Dr. Shawn H. Zimberg, medical director of radiation oncology for Advanced Radiation Centers (ARC) of New York.

“So these cancers grow without the immune system waking up and doing anything about them, which is unfortunate because we’ve got this amazing army in our immune system that doesn’t even really know the cancer is there,” he added.

ProstAtak works through a series of three injections of a viral vector that goes directly into the prostate using gene transfer technology. Each injection is accompanied by a round of antiviral pills. The combination seems to prime the cells for a more robust cell death during standard radiation therapy. According to Zimberg, this is what awakens the immune system.

“With the immune system jump-started, the patient potentially has now developed a life-long immunity specifically to their own cancer,” he said. “This circulating immunity may be enough to mop up any leftover cancer cells either in the prostate region or even for metastatic disease.”

In a previous study, the treatment was associated with a significant decrease in expected tumor recurrence.

Unlike Provenge, a popular immune therapy currently on the market for patients with metastatic prostate cancer who are no longer responding to therapy, ProstAtak is designed for localized, newly diagnosed disease. Another key difference between the two therapies is the fundamental way in which they work. With Provenge, white blood cells are removed from the body and then exposed to generic prostate cancer antigens. Then they’re put back into the body, which creates an immunity to a generic prostate cancer. According to Zimberg, this approach typically gives the patient a three to four month survival benefit over men who don’t undergo the treatment.

ProsAtak is different in that it triggers the body to create an immunity to its own specific cancer – not a generic.

“It’s actually a very exciting and novel method where we are literally trying to use the body’s own immunity,” said Zimberg, who compared the immune system to a potent army unlike any other.

A national clinical trial is currently enrolling patients at a variety of sites throughout the country.

By Marianne Hayes

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