Gene-Editing Trial on Three Individuals for HIV Cure Yields Uncertain Result

The gene-editing technology CRISPR has been used to change the genes of human babies, to modify animals, and to treat people with sickle-cell disease. Now scientists are attempting a new trick: using CRISPR to permanently cure people of HIV. In a remarkable experiment, a biotechnology company called Excision BioTherapeutics says it added the gene-editing tool to the bodies of three people living with HIV and commanded it to cut, and destroy, the virus wherever it is hiding. The early-stage study is a probing step toward the company’s eventual goal of curing HIV infection with a single intravenous dose of a gene-editing drug. Excision, which is based in San Francisco, says the first patient received treatment about a year ago.

This week, doctors involved in the study reported at a meeting in Brussels that the treatment appeared safe and did not have major side-effects. However, they withheld early data about the treatment’s effects, leaving outside experts guessing whether it had worked. “This is an exceptionally ambitious and important trial,” says Fyodor Urnov, a genome-editing expert at the University of California, Berkeley, who believes it “would be good to know sooner than later” what the effect was — “including, potentially, no effect.”

A failure wouldn’t come as a surprise to anyone familiar with HIV. It has proved a devious adversary: there is still no vaccine, even 40 years after the virus was identified in 1983. Still, pharmaceutical companies did develop antiretroviral drugs, which stop the virus from copying itself. Taking these pills lets people with HIV live normal lives. But if they stop, the virus will quickly rebound and, if left unchecked, cause the fatal syndrome of infections and cancers known as AIDS. One reason the virus can’t be fully wiped out with drugs alone is that it inserts its genetic material into the DNA of our cells, leaving behind hidden copies that can restart the infection.