The powerful gene-editing CRISPR-Cas9 technique is a promising tool in the fight against conditions like retinal degradation, muscular dystrophy and HIV, but so far trials have been restricted to cultured cells and laboratory mice. Now the tool is being used in human trials for the first time, with a team of Chinese scientists injecting CRISPR-edited cells into a patient suffering from lung cancer.

CRISPR works like a pair of genetic scissors, allowing scientists to cut very specific sections of DNA out of an organism, such as inherited genes that may lead to disease, and replace them with something more beneficial. Along with its potential to fight cancer and other illnesses in humans, the technique can be used in other living organisms for a variety of purposes, like pest control or improving the yield, hardiness and nutritional value of crops.

The current study, led by oncologist Lu You at Sichuan University, is using the technique to modify immune cells of patients with metastatic non-small-cell lung cancer, in the hope that it might boost the body's defenses. In basic terms, the immune system uses a type of white blood cell called a T cell to detect and kill abnormal cells that may turn cancerous. T cells have a built-in mechanism called Programmed cell death protein 1 (PD-1) that shuts them down when they're done, and one of cancer's crafty little tricks is to trigger that process early, weakening the body's immune response and allowing the tumor to grow.

To combat this, the Sichuan study is collecting samples of a patient's immune cells and using CRISPR-Cas9 to remove the gene in which PD-1 is encoded. These engineered PD-1 Knockout T cells, as the team calls them, are then cultured in the lab to grow their numbers before being injected back into the patients. Without the PD-1 protein for the cancer to turn against the immune system, the team hopes that the engineered T cells will be able to keep up the fight and kill the tumor.

The trial was greenlit in July after receiving ethical approval from a hospital review board, and after collecting and cultivating the T cells, the first patient was injected with edited cells on October 28. While the researchers haven't given details regarding the patient's progress, the treatment apparently went well, and a second injection is planned. The aim of the trial is mostly to determine the safety of the procedure, and to that end, 10 patients will be treated with either two, three or four injections.

The study is expected to conclude in April 2018. Several other human trials using CRISPR-Cas9 are currently in the pipeline, including a University of Pennsylvania study expected to start early next year, and a series of others at Peking University in Beijing.