A Chinese gene-editing experiment has lost touch with patients whose DNA was altered, alarming Western scientists who say subjects should be monitored for many years, The Wall Street Journal reports. The gene-editing tool known as Crispr-Cas9 allows scientists to edit the DNA of patients in hopes of eliminating harmful mutations, such as those that cause cancer. However, Chinese scientists have reportedly leapfrogged in experimenting with gene-editing on humans in the last few years. Beijing has no federal body that oversees gene-editing trials, meaning standards vary across experiments. The approach has been troubling to doctors and scientists in the U.S., who fear the promising science could be overshadowed by haphazard implementation. Last month, a Chinese scientist claimed he has created the world’s first gene-edited babies. Jennifer Doudna, a professor of chemistry and molecular & cell biology at the University of California Berkeley who is credited as a co-inventor of the Crispr technology, responded to the claim. “Because the data have not been peer-reviewed, the fidelity of the gene-editing process cannot be evaluated,” Doudna cautioned.