Fighting Cancer with Polio

A promising new treatment that uses the polio virus to attack a virulent brain cancer called glioblastoma was recently granted breakthrough therapy designation by the FDA.

To receive this designation, early clinical evidence must suggest a significant improvement over therapies currently available to treat a serious or life-threatening disease or condition. The designation was granted to the recombinant oncolytic polio virus PVS-RIPO after data showed that patients who had been living an average of 10 months were living an average of 15 months after treatment. Additionally, 3 patients showed no sign of cancer at all after 3 years.

The polio virus was chosen by Duke Medicine researchers because it seeks out and attaches to a receptor that’s found on the surface of the cells on nearly every kind of solid tumor. For the study, the polio virus was re-engineered, which involved removing a key genetic sequence and replacing it with a harmless portion of a cold virus.

PVS-RIPO can’t cause paralysis or death because it can’t reproduce in normal cells. However, it can reproduce in cancer cells, where it releases toxins that poison them. By infecting the tumor, the protective measures that normally surround tumors and shields them from the immune system is removed. With this shield out of the way, the immune system can attack and kill the tumor cells.

Essentially, the immune system recognizes tumor cells as polio infection and sets off alarms to attack those cells. The modified polio virus starts the killing the cells, and the immune system mounts an additional attack.

Interestingly, the polio virus treatment also appears to set up the tumor to be more responsive to chemotherapy in patients who previously haven’t seen positive results with chemotherapy.

With breakthrough therapy designation, the second phase of the trial will be expanded to about 40 centers, where hundreds of patients may participate. If all goes well, Duke will be allowed to skip the third phase of the trial and make polio therapy for glioblastoma available to all.

Scientists say they’re looking to see if the polio virus can attack other forms of cancer, including breast, colon, pancreatic, prostate, lung, skin and stomach cancers.