Honjo, professor at Kyoto University since 1984, separately discovered a second protein called PD-1 and found that it too acted as an immune system brake, but with a different mechanism.
"Immunotherapy is now possibly the most important recent discovery for cancer therapy in general, as an alternative to chemo", he said. Allison then developed a "checkpoint inhibitor", or a drug that releases that brake, and enables the patient's immune system to identify and confront tumors. His research has also helped former President Jimmy Carter, who was diagnosed in 2015 with skin cancer which had spread to his brain.
"By stimulating the inherent ability of our immune system to attack tumor cells this year's Nobel Laureates have established an entirely new principle for cancer therapy", the Nobel Prize Foundation said in a statement.
The treatments, often referred to as "immune checkpoint therapy", have "fundamentally changed the outcome for certain groups of patients with advanced cancer", it added.
The American Cancer Society's chief medical officer says he and colleagues gave a celebratory toast to Allison at a party on Friday - days before the announcement of the Nobel Prize in Medicine - because they agreed this could be his year.
"Science advances on the efforts of many", Allison said.
Half of the 9-million-kronor ($1.01 million) prize goes to Frances Arnold of the California Institute of Technology. "Brakes" on the surface of T cells essentially halt activation of the immune response when it's not needed.
Wireless Emergency Alert System Test happening Wednesday
The agency is required by law to conduct a nationwide test of its public alert systems no less than once every three years. A similar but slightly longer test message will be sent over television and radio stations two minutes later.
The already much-heralded University of Texas MD Anderson Cancer Center in Houston has just scored global bragging rights.
What makes cancer so hard to target and treat is its ability to outsmart the immune system in different ways. In the USA, some have reportedly asked their doctors to immediately use immunotherapy instead of traditional treatments like chemotherapy, even when they are more effective. Their work has been crucial to developing new and extremely effective treatments.
The method researched by the scientists have found out ways to remove the brakes on cells that fight attackers.
The pioneering work of Allison and Honjo led to the development of several drugs, including ipilimumab (Yervoy), the first immunotherapy drug, and the PD-1 inhibitors nivolumab (Opdivo) and pembrolizumab (Keytruda). The Nobel Memorial Prize for Economic Sciences will be announced on Monday, October 8.
"It has been so fulfilling that I wish I could live this life all over again", he said, while thanking his family for allowing him to focus on his research.
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.
Pharmaceuticals for rheumatoid arthritis, psoriasis and inflammatory bowel diseases have resulted from their research, as well as anti-bodies that can neutralise toxins, counteract autoimmune diseases and cure metastatic cancer.
"At that time, I never thought it would lead to a drug to treat cancer", Honjo said. No literature prize is being given this year.