Parents want accountability after a cutting-edge gene-editing trial in China went disastrously wrong, according to an exclusive investigation from Science and Retraction Watch. Meagan Cantwell, a video producer at Science, explains. #ScienceTok #STEMTok #NewsFromScience CREDITS: (IMAGES) LI YIBO/XINHUA/ALAMY; WANG GANG/COSTFOTO/BARCROFT MEDIA VIA GETTY IMAGES; (ILLUSTRATION) A. MASTIN/SCIENCE; (VIDEO PRODUCTION) M. CANTWELL/SCIENCE

A six-year-old girl in China died after receiving an experimental gene therapy, and her family once accountability now. For privacy, her parents have asked to call their daughter Mei. When Mei was four, her teachers noticed she was falling behind her peers in class. The root cause came down to a single mutated DNA base, a T that should have been a C in a gene that influences brain development. While seeking advice and treatment options, Mei's parents contacted a prominent neurodevelopmental expert, named Zilong Chu. He offered to develop a treatment that would fix the mutated gene in Mei's neurons, using a base editor, a more precise version of the gene editor, CRISPR. Mei's parents paid $860,000 to fund his team's studies for the potential therapeutic. In mice, researchers were able to repair the genes using a virus to deliver the base editor. The researchers then showed that a different virus, tailored to human cells, could reach and edit the brain cells of monkeys, another primate. In January of 2025, the hospital's ethics panel approved a moving forward with the trial, based on data that showed that the base editor worked in mice and primates. But a second primate study looking at safety wasn't reviewed by the panel in time. That study showed that of the four monkeys that had received the therapy all developed varying degrees of liver damage and one had kidney damage. The likely cause was a serious immune reaction to the virus that triggered a cascade of microscopic blood clots. The informed consent document Mei's physicians gave her parents mentioned that this could be a possible outcome, but they say that the risks of the trial were downplayed to them. In March of 2025, Mei received an infusion containing trillions of viruses with the gene editing instructions. Seven days later, she died from the same kind of organ injuries that the consent forms had warned about. Later that year, the hospital was fined $3,600 for not receiving proper approvals for the clinical trial, as well as a handful of other violations. The lead researcher who didn't reply to requests for comment wasn't punished. This year, he and his colleagues published a paper in Nature on some of the preclinical research showing that the gene editing treatment worked in mice and primates. Nowhere in it did it mention the concerning primate safety data or Mei's death. While the first person who died from a gene therapy trial decades earlier, Jesse Gelsinger, prompted a major self-examination within the field, Mei's death has gone undisclosed until now.