Critical ethical questions about the very first CRISPR clinical trial in the United States were being debated on the NIH campus the same week as my gene-editing course. During lunch and coffee breaks, I went to watch a committee of experts evaluate a proposal for a research project that aimed to cure cancer. Eleven distinguished scientists, doctors, and ethicists were seated around a large rectangular table as professional staffmembers in neckties and suits fiddled with AV equipment and took notes on laptops in the back of the room.

A handful of onlookers from biotech companies and government agencies sipped coffee from takeaway cups as Dr. Richard Whitley, the acting committee chairman, called the proceedings to order: “We have been at this now for forty years, and it is our responsibility to continually update the guidelines to make sure that they are contemporary with current procedures. Today is a landmark.” It was June 21, 2016, and the committee would decide if CRISPR should be ushered into the clinic.

Formed in 1975, the Recombinant DNA Advisory Committee (RAC, pronounced “rack”) had a venerable history. Early on, scientific experts addressed concerns about ecological, health, and safety issues related to all genetically engineered organisms. Over the years, the RAC's mission narrowed. Scrutiny of modified microbes, plants, and animals was no longer part of the committee's mandate. They began to focus on gene therapies in humans.

Gene therapy experiments began with live human patients in 1990, when a synthetic virus was designed to target a rare immunological disease. The therapy did not work, but the virus seemed safe enough. More than 4,000 people had their DNA modified in gene therapy experiments over the next decade. Viruses—derived from herpes, pox, and HIV—were used to infect patients’ cells with artificial genes designed by scientists. Some of the experiments went awry. Jesse Gelsinger, a relatively healthy eighteen-year-old with a rare genetic condition, died during a gene therapy experiment at the University of Pennsylvania in 1999. After this accident, the RAC applied the brakes. In recent years, a trickle of new experiments had started to make it through the pipeline. If this CRISPR experiment was approved, the trickle could turn into a flood.