Tasuku Honjo, a distinguished professor at Kyoto University, has been named a co-winner of this year's Nobel Prize in Physiology or Medicine for his discovery of a protein that has been effective in the fight against cancer.

Honjo, 76, was named to share this year's prize by the Nobel Assembly at the Karolinska Institute in Stockholm with James Allison, 70, of the MD Anderson Cancer Center at the University of Texas.

The two scientists were cited for "their discovery of cancer therapy by inhibition of negative immune regulation."

Honjo discovered the protein known as PD-1, which serves as a switch for the immune system on the surface of immune cells that attack foreign matter in the body. The discovery was applied for the development of cancer drugs that inhibits the activity of the PD-1 so immune cells can continue to attack cancer cells.

The last Japanese to win the Nobel Prize in Physiology or Medicine was Yoshinori Ohsumi, an honorary professor at the Tokyo Institute of Technology, in 2016.

Honjo becomes the 26th Japanese to win a Nobel Prize and the fifth to win the prize in physiology or medicine, following Susumu Tonegawa, a professor at the Massachusetts Institute of Technology, who won in 1987; Shinya Yamanaka, a Kyoto University professor who won in 2012; Satoshi Omura, a distinguished professor emeritus at Kitasato University, who won in 2015; and Ohsumi.

The awards ceremony will be held in Stockholm on Dec. 10.