Vaccine Injection Targeted in Building a Better 'Bull's-Eye' to Fight Prostate Cancer

Looking to harness the body’s own immune system to target prostate cancer that has spread to the bones (metastatic) and is unresponsive to standard treatment, investigators at The Cancer Institute of New Jersey (CINJ) have just launched a clinical trial focusing on a combination of vaccine and radiation drug therapy. The goal is to see if disease progression will be further delayed by adding two different experimental injections to the standard treatment. CINJ is a Center of Excellence of UMDNJ-Robert Wood Johnson Medical School.

A standard treatment for prostate cancer that has spread to the bones is with a drug approved by the Food and Drug Administration known as samarium153. It contains material that gives off a tiny amount of energy (radiation) that damages cancer cells. And because radiation drugs such as samarium153 also can increase the immune system’s ability to find and kill cancer cells, CINJ researchers want to combine this treatment with a series of vaccination injections aimed at helping the body’s natural defenses work better.

At focus are two different experimental vaccines. PROSTVAC-V/TRICOM has a special virus added to it that produces a prostate specific antigen (PSA) protein which helps focus the body’s immune response to the PSA in the prostate tumor.

Other human genetic material added to this vaccine produces three other proteins that help increase an immune cell’s ability to destroy its target. The second vaccine, PROSTVAC-F, contains the same genetic material as PROSTAC-V, but will be given more frequently to boost the body’s immune system. Previous studies led by CINJ Director Robert S. DiPaola, MD, professor of medicine at UMDNJ-Robert Wood Johnson Medical School, have shown that giving the PROSTVAC-V vaccine followed a short time later by booster injections with PROSTVAC-F is more effective in increasing immune response than receiving one vaccine alone.

Mark Stein, MD, medical oncologist at CINJ and assistant professor of medicine at UMDNJ-Robert Wood Johnson Medical School, is the lead researcher on the new study. “Naturally, the body’s immune system is designed to fight off foreign material, but falls short when it comes to recognizing cancer cells. Through this combination of radiation therapy and vaccine injections, we’re trying to create a better ‘bull’s-eye’ for the body to target by utilizing more of the body’s own natural materials,” he said.

Adults with metastatic prostate cancer resulting in bone lesions that are not responding to standard treatment are eligible to take part in the trial, although other criteria must be met. Prior to being accepted into the study, participants would undergo a number of tests including blood work, a bone scan and a physical.

If accepted for participation in the trial, individuals will be divided at random into two groups for treatment. Those receiving samarium153 by itself will receive the drug by vein. Those selected for the combination therapy will receive samarium153 as well as one injection of PROSTAC-V/TRICOM in the thigh and then monthly injections of PROSTAC-F/TRICOM under the skin during the course of the study. After four months on study, participants will be evaluated for how the cancer is responding to treatment and continue to be treated with the assigned treatment regimen if the disease is responding favorably and they are not having severe side effects.