Thomas Perlmann, far right, Secretary-General of the Nobel Committee announces the 2019 Nobel laureates in Physiology or Medicine during a news conference today in Stockholm, Sweden. The prize has been awarded to scientists, from left on the screen, Gregg L. Semenza, Peter J. Ratcliffe and William G. Kaelin Jr. receiving the award jointly for their discoveries of "how cells sense and adapt to oxygen availability". (Pontus Lundahl/TT via AP)

STOCKHOLM (AP) — Two Americans and a British scientist won the 2019 Nobel Prize for Physiology or Medicine for discovering how the body’s cells sense and react to oxygen levels, work that has paved the way for new strategies to fight anemia, cancer and other diseases, the Nobel Committee said today.

Drs. William G. Kaelin Jr. of Harvard University, Gregg L. Semenza of Johns Hopkins University and Peter J. Ratcliffe at the Francis Crick Institute in Britain and Oxford University will share equally the 9 million kronor ($918,000) cash award, the Karolinska Institute said.

It is the 110th prize in the category that has been awarded since 1901.

Their work has “greatly expanded our knowledge of how physiological response makes life possible,” the committee said today, explaining that the scientists identified the biological machinery that regulates how genes respond to varying levels of oxygen.

That response is key to things like producing red blood cells, generating new blood vessels and fine-tuning the immune system.

The Nobel Committee said scientists are focused on developing drugs that can treat diseases by either activating or blocking the body’s oxygen-sensing machinery.

The oxygen response is hijacked by cancer cells, for example, which stimulate formation of blood vessels to help themselves grow. And people with kidney failure often get hormonal treatments for anemia, but the work of the new laureates points the way toward new treatments, Nils-Goran Larsson of the Nobel committee told The Associated Press.

Reached at his home, Kaelin said he was half-asleep this morning when the phone rang. It was Stockholm.

“I was aware as a scientist that if you get a phone call at 5 a.m. with too many digits, it’s sometimes very good news, and my heart started racing. It was all a bit surreal,” he said.

Kaelin said he isn’t sure yet how he’ll spend the prize money but “obviously I’ll try to put it to some good cause.”

Ratcliffe told Sweden’s news agency TT today that “when I started my research I also had no idea that it would result in this.”

He added the impact of oxygen on cells “has not always been a trendy area to research, and some people have doubted them during the journey.”

Last year, James Allison of the United States and Tasuku Honjo of Japan won the 2018 Nobel Prize for Medicine for their work in immunotherapy, activating the body’s natural defense system to fight tumors.

Today’s announcement kicked off this year’s Nobel Prizes. The Nobel Physics prize is handed out Tuesday, followed by the chemistry prize on Wednesday. This year’s double-header Literature Prizes — one each for 2018 and 2019 — will be awarded Thursday and the Peace Prize will be announced on Friday.

The economics prize will be awarded on Oct. 14.