A world where DNA can be rewritten to fix deadly diseases has moved a step closer after scientists said they had genetically edited the cells of a human for the first time.
A man in China was injected with immune cells modified to fight his lung cancer. Larger trials due next year in the United States and Beijing could open up a new era of genetic medicine, scientists say.
The technique used, Crispr, snips away genetic code and replaces it with instructions to build better cells.
Professor Andrew Sharrocks, of the University of Manchester, said the technique could help in treating cancer "but also potentially combating auto-immune type diseases including ... arthritis".
"I would expect similar types of approaches to be pioneered in the next few years as the potential for using this technology in the medical sphere is high and potentially transformative," he said.
In the case of the Chinese man, scientists led by Dr Lu You at Sichuan University in Chengdu focused on a gene which holds the instructions to build a protein called PD-1. The protein works like an antenna, looking out for healthy cells, so the immune system knows not to attack them.
However, cancer masquerades as a healthy cell, which is why it is often so deadly.
The scientists took immune cells from the man's blood and altered their DNA to remove the antennae, before increasing them in a lab and returning them to his bloodstream.
Experts say it is effectively like cutting the brakes on the immune system.
Doctors will monitor the man's progress over the next six months. They also plan to inject 10 more people with genetically edited immune cells in the coming months.
Dr Carl June, of the University of Pennsylvania, is planning a cancer trial in the US next year, while Peking University is planning Crispr trials for bladder, prostate and renal-cell in China next March.
Speaking to the journal Nature, he likened the US-China race to "Sputnik 2.0".