A DRUG that helps the immune system destroy cancer has been developed by US scientists.

It dramatically shrank deadly skin, brain and bowel tumours in mice and it is now hoped human trials will be just as successful.

The antibody is hailed as an exciting candidate for immunotherapy, a cancer treatment described as a “game changer”.

Scientists stumbled on the idea while studying multiple sclerosis, an autoimmune disease where the immune system mistakenly attacks the body’s own tissues. Cancer works in the opposite way.

Professor Howard Weiner, of Ann Romney Centre for Neurologic Diseases in Boston, said: “We could turn our investigations around and think how to restore the ability to stop cancer’s growth.”

Prof Weiner, co director the Ann Romney Center for Neurologic Diseases at Brigham and Women’s Hospital, Boston, has been studying T cells, which help the immune system tolerate our own bodies, for years.

It is a key survival mechanism that cancer takes advantage of, sending nefarious signals that cause the immune system cells to stand down, preventing them from detecting and attacking tumours.

Prof Weiner’s lab team found the antibody precisely targets T cells by locking onto chemicals on their surface .

They created anti-LAP initially to investigate the development of multiple sclerosis, but realised their work had implications for the study of cancer.

Its effectiveness centres on a protein called LAP (latency associated peptide) which has already been shown to increase in human cancer and predicts a poor prognosis.

Prof Weiner said this encourages him that targeting it will lead to similar results in patients.

He added: “Consistent with our findings, LAP expression in human cancer is associated with a poorer prognosis, providing an important translational link between our results and human disease and making anti-LAP an attractive candidate for cancer immunotherapy.”

Tests on cells in the lab and on mice showed anti-LAP acts on multiple populations of cells to boost the immune system’s ability to fight cancer.

This included increasing the activity of certain types of T cells and enhancing immune memory.

Lead author Dr Galina Gabriely said: “In addition to studying its therapeutic effect, we wanted to characterise the mechanism by which the anti-LAP antibody can activate the immune system, We found it affects multiple arms of the immune system.”

Clinical trials are now needed to see if it will benefit patients. US biotechnology company Tilos Therapeutics, which develops treatments for cancer, is modifying the antibody for use in humans. This is a process that usually takes several years.

Chief executive Dr Barbara Fox said: “I see this work as the perfect example of how research in all branches of immunology into the mechanistic underpinnings of disease can have a huge impact on other fields, such as oncology.”