Two Americans and a Briton won the 2019 Nobel Medicine Prize on Monday for discovering a molecular switch that regulates how cells adapt to fluctuating oxygen levels, opening up new approaches to treating heart failure, anaemia and cancer.

William Kaelin at the US Dana-Farber Cancer Institute and Harvard Medical School was “almost speechless” when told that he and two other doctors, Gregg Semenza of Johns Hopkins University and Briton Peter Ratcliffe of Oxford University, would share the 9-million Swedish-crown ($913,000) prize, the Nobel award-giving body said.

“They were extremely happy, and happy to share the prize with each other,” Thomas Perlmann, a member of the Nobel Assembly, told reporters as the prize was announced.

The scientists’ work established the basis for understanding of how oxygen levels are sensed by cells — a discovery that is being explored by medical researchers seeking to develop treatments for various diseases that work by either activating or blocking the body’s oxygen-sensing machinery.

Their work centres on the hypoxic response — the way the body reacts to oxygen flux — and “revealed the elegant mechanisms by which our cells sense oxygen levels and respond” said Andrew Murray, an expert at Britain’s University of Cambridge who congratulated the three.

Randall Johnson, a professor at the Karolinska Institute where the prize is awarded, noted that since “oxygen is essential for life and is used by virtually all animal cells,” the work is central to how the body functions.