Four U.S. CRISPR Trials Editing Human DNA to Research New Treatments

Last fall, the birth of genetically edited twin girls in China—the world’s first “designer babies”—prompted an immediate outcry in the medical science community. The change to the twins’ genomes, performed using the gene editing technology CRISPR, was intended to make the girls more resistant to H.I.V. But the edited genes may result in adverse side effects, and the International Commission on the Clinical Use of Human Germline Genome Editing is currently working on stricter and less ambiguous guidelines for editing the DNA of human embryos as a response to the rogue experiment.

Human genetic engineering has also witnessed more regulated advances. In the past 12 months, four clinical trials launched in the United States to use CRISPR to treat and potentially cure patients of serious medical conditions.

CRISPR-Cas9 is a technology derived from single-celled prokaryotic microorganisms and is composed of guide strands of RNA as well as the Cas9 enzyme, which does the “cutting.” It allows scientists to make changes at highly specific locations in a cell’s genetic code by removing or replacing parts of the genome. Even tiny changes to individual genes can fundamentally alter the function of a cell. CRISPR has been used to edit all types of organisms, from humans to corn, but clinical trials represent a stride toward turning the technology into a drug or medical treatment.

The clinical trials in the U.S. are Phase 1 and 2 trials, small studies designed to demonstrate the safety and efficacy of a potential treatment. Essentially, these make-or-break trials take a drug from the laboratory to test on real patients. They’re “the first requirement for a product to end up on the market,” says Saar Gill, an assistant professor at the University of Pennsylvania’s medical school who works on genetically-edited immune cells.