The standard polio virus uses a receptor molecule present on brain cells to "unlock" them. The virus then enters the cell and replicates until the cell dies. Gromeier's modified version of polio is spliced with a rhinovirus, which causes the common cold. This allows it to enter healthy brain cells using the same receptor molecule – which is also found in most cancers – but the virus is unable to replicate, so it can't hurt the cells.
However, because cancer cells have a different biochemical makeup than regular brain cells, the modified virus is able to enter them, replicate and kill them much like normal polio does. As such, the virus leaves healthy brain tissue unharmed, but it targets and destroys cancer.
Once Lipscomb and her mom were on board, doctors used a catheter to enter Lipscomb's brain and slowly inject the virus over six and a half hours.
It took several months for the virus to start killing Lipscomb's cancer cells, but on Monday, she learned that the tumor was only the size of a pea. Desjardins told her it could come back, but the tumor was still shrinking.
"It was probably one of the most exciting scans I have ever seen of my brain," Lipscomb said. "I don't think it's going to come back."
Of the eight patients treated with the modified polio virus, two have not responded well. Three patients have been improving over the last few months and it is too soon to tell how well three other patients will respond, Gromeier said. He does not know why the tumors didn't shrink in two of the patients.
Another clinical trial is in the works so Gromeier can continue his research.
Since even non-glioblastoma cancer cells have the receptor polio needs to unlock it, Gromeier has been able to shrink melanoma, prostate, colorectal and pancreas cancers in a lab. Still, he has yet to do trials on animals or humans.