A cancer jab that can eliminate tumours, even when they have spread throughout the body, is about to start human trials.
Scientists at Stanford University in the US found that injecting tiny amounts of two drugs directly into a tumour not only killed the original cancer, but also triggered an "amazing bodywide" reaction, destroying distant cancer cells.
The drug combination works by switching on immune cells inside the tumours, which have been deactivated by the cancer, then boosting them, so they can go to work on killing the disease.
Once the immune cells have been reactivated, they recognise other cancer cells elsewhere in the body and set about clearing them out.
Scientists said the therapy worked "startlingly well" in mice. Nine out of 10 animals were cured of cancer after just one jab and the rest after a second injection.
"When we use these two agents together, we see the elimination of tumours all over the body," said Dr Ronald Levy, Professor of Oncology at Stanford University School of Medicine.
"Our approach uses a one-time application of very small amounts of two agents to stimulate the immune cells only within the tumour itself.
"In the mice, we saw amazing, bodywide effects, including the elimination of tumours all over the animal.
"I don't think there's a limit to the type of tumour we could potentially treat, as long as it has been infiltrated by the immune system."
Researchers are now recruiting patients to test the drug combination but believe it will be a cheap and effective way of fighting multiple types of cancer. The process is likely to take less time because one drug in the cocktail is already approved for use in humans, while the other is currently undergoing human trials.
And unlike other forms of immunotherapy, it is likely to have few side effects. Most similar drugs work by cutting the brakes on the immune system, but the downside to that is it also kills healthy cells.
However, the new treatment harnesses the immune system's own ability to recognise cancer cells and infiltrate tumours.
As a tumour grows, it often devises a way to suppress the activity of 'killer' immune cells, which get inside, but the new drug combination effectively reawakens those cells.
Those cancer-specific cells can then leave the original tumour site and travel through the body to fight other disease sites.
In mice studies, 87 out of 90 mice with breast, colon and melanoma tumours were cured of their cancer. Although tumours returned in three animals, a second jab was able to halt the disease.
The researchers said that in future doctors could inject a tumour before it was removed, so that the body could then get to work fighting unidentified cancer elsewhere in the body.
The research was published in the journal 'Science Translational Medicine'.