The controversial gene-editing tool CRISPR may soon be used to create custom blood cells that hunt cancer — its first use to treat humans. A study at the University of Pennsylvania received an initial approval from the ethical gatekeepers at the National Institutes of Health this week, the government body's Recombinant DNA Advisory Committee (RAC) signing off on its potential use in a human trial.

Immune cells will be edited and then inserted back into cancer patients

The designer immune cell technique has previously been tested in cancer patients. For it, doctors take a sample of patients' blood and spin out white blood cells called T cells. Previous trials have used a virus to insert a section of DNA that searches for cancerous mutations, before infusing the lab-made blood cells back into patients. The scientists involved say using CRISPR may make the treatment more effective, letting them target cancers more precisely, as well as bolster the T cells' capabilities and reproduction rate.

"It's an important new approach," RAC clinical oncologist Michael Atkins said of the trial. "We're going to learn a lot from this, and hopefully it will form the basis of new types of therapy." In addition to excitement from the scientific community, CRISPR has also generated interest in tech circles after successfully helping to produce small pigs and excessively buff dogs, with Napster founder Sean Parker using his Parker Institute for Cancer Immunotherapy to fund the planned cancer trial.

The trial still needs to pass through other ethics boards

But scientists have also warned against reckless use of CRISPR to alter human genes. The technology could be used to build designer babies, for example, an ethical gray area. It's also such a new area of research that it may have unforeseen health consequences down the line, factors that informed John Holdren from the White House Office of Science when he said last year that "altering the human germline for clinical purposes was a line that should not be crossed at this time." Altering the T-cells doesn't count as a germline alteration, since the lab-designed blood cells won't be passed along to offspring.

RAC approval in this case is a big step for the human applications of CRISPR, but the researchers still have a way to go before the trial can begin, the doctors involved needing similar responses from in-house ethics boards and the US Food and Drug Administration. But even if it doesn't go ahead, it seems to be a matter of when, not if CRISPR will be used in humans as other studies — including one by Editas Medicine aiming to use the technology to treat eye disease — are also in the works.