Two immunologists, James Allison of the US and Tasuku Honjo of Japan, won the 2018 Nobel Medicine Prize for research into how the body's natural defences can fight cancer, the jury said on Monday.
Unlike more traditional forms of cancer treatment that directly target cancer cells, Allison and Honjo figured out how to help the patient's own immune system tackle cancer more quickly.
The award-winning discovery led to treatments targeting proteins made by some immune system cells that act as a "brake" on the body's natural defences killing cancer cells.
The Nobel Assembly said after announcing the prize in Stockholm that the therapy "has now revolutionised cancer treatment and has fundamentally changed the way we view how cancer can be managed."
In 1995, Allison was one of two scientists to identify the ligand CTLA-4 as an inhibitory receptor on T-cells.
T-cells are a type of white blood cell that play a central role in the body's natural immunity to disease.
Allison, 70, "realised the potential of releasing the brake and thereby unleashing our immune cells to attack tumours," the Nobel jury said during Monday's prize announcement in Stockholm.
Around the same time, Honjo discovered a protein on immune cells, the ligand PD-1, and eventually realised that it also worked a brake, but it acted differently.
Writing on his cancer centre's website, Allison said he was "honoured and humbled to receive this prestigious recognition".
Antibodies against PD-1 have been approved by the US Food and Drug Administration as an investigational new drug and developed for the treatment of cancer.
Research by Allison's team has meanwhile led to the development of a monoclonal antibody drug, which was approved by the US Food and Drug Administration (FDA) in 2011 for the treatment of melanoma.
"For more than 100 years, scientists attempted to engage the immune system in the fight against cancer. Until the seminal discoveries by the two laureates, progress into clinical development was modest," the Nobel jury said.
Allison, a professor at the University of Texas, and Honjo, a professor at Kyoto University, were in 2014 awarded the Tang Prize, touted as Asia's version of the Nobels, for their research.
- New therapies 'desperately needed' -
Other cancer treatments have previously been awarded Nobel prizes, including methods for hormone treatment for prostate cancer in 1966, chemotherapy in 1988 and bone marrow transplantation for leukaemia in 1990.
"However, advanced cancer remains immensely difficult to treat, and novel therapeutic strategies are desperately needed," the Nobel Assembly said.
The duo will share the Nobel prize sum of nine million Swedish kronor (about $1.01 million or 870,000 euros).
They will receive their prize from King Carl XVI Gustaf at a formal ceremony in Stockholm on December 10, the anniversary of the 1896 death of Alfred Nobel who created the prizes in his last will and testament.
Last year, US geneticists Jeffrey Hall, Michael Rosbash and Michael Young were awarded the medicine prize for their research on the role of genes in setting the "circadian clock" which regulates sleep and eating patterns, hormones and body temperature.
The winners of this year's physics prize will be announced on Tuesday, followed by the chemistry prize on Wednesday. The peace prize will be announced on Friday, and the economics prize will wrap up the Nobel season on Monday, October 8.
For the first time since 1949, the Swedish Academy has postponed the announcement of the 2018 Nobel Literature Prize until next year, amid a #MeToo scandal and bitter internal dispute that has prevented it from functioning properly.