What is 'checkpoint therapy' and why did it win the medicine Nobel prize?

James Allison and Tasuku Honjo jointly take this year’s 2018 Nobel prize in physiology or medicine for ‘their discovery of cancer therapy by inhibition of negative immune regulation’. But what does this actually mean, how does it work and what makes it a cut above the rest? We explain why checkpoint therapy is the most exciting thing to happen in decades when it comes to treating cancer.