A death that stayed hidden for a year: what the Mei case reveals about gene-therapy trials

In late July, Science magazine published an investigation with a stark finding: a six-year-old girl had died in an experimental gene-therapy trial in Shanghai in 2025, and her death had never been made public. The story has kept growing since. An official investigation was announced, the trial was halted, regulators were questioned, and this month an international industry body published its own independent inquiry. The case has become the clearest test yet of how gene therapy is being tried on patients outside the usual guardrails.

The girl, known publicly only as Mei, received the treatment in March 2025 at Xinhua Hospital, part of Shanghai Jiao Tong University School of Medicine. She had a rare neurodevelopmental disorder linked to the CHD3 gene. The experimental therapy delivered a base editor, a molecular tool for rewriting a single letter of DNA, into her cerebrospinal fluid inside viral vectors. Within days she developed a fever and kidney failure, and her blood platelets collapsed. About a week after the infusion she died. The hospital’s ethics board met in emergency session and concluded that the death was ‘definitely related’ to the treatment, according to its report. The immediate cause was thrombotic microangiopathy, a severe immune reaction to the viral delivery.

What happened next is the part that has drawn the sharpest criticism. The death was not disclosed to the public or to the research community at the time. The lead researcher, a Shanghai neuroscientist named Zilong Qiu, went on to publish related animal studies in Nature; the paper did not mention the girl’s death, nor that her parents said they had contributed financially to the therapy’s development. It was not until Science published its investigation on 23 July this year that the case became public, sixteen months after the girl died.

The official response followed quickly. The medical school issued a statement on 26 July saying it had set up a working group and would conduct a full investigation. On 30 July the trial’s entry on an international clinical-trial registry was changed to show that recruitment had stopped, with a serious adverse event assessed as related to the trial drug. The family have sought accountability and asked Nature to retract the paper. According to Science, the hospital later paid a modest fine to a local health authority, while the lead researcher was not publicly sanctioned. This month, the Oligonucleotide Therapeutics Society, the professional body for the field, published its own investigation under the title ‘Mei’s Story’, lending weight to the family’s account of what happened.

The regulatory questions are the most serious. The treatment appears to have proceeded under a provision that does not require approval from national regulators, a gap that ethicists and gene-therapy specialists have since identified as the reason a fatal outcome could pass so quietly. The case has also revived memories of earlier Chinese gene-editing controversies, and the international coverage has been unforgiving.

Experimental medicine depends on patients who are willing to take risks that no one else will take. That willingness rests on honesty: about what is known, what is not known, and what went wrong. When a death in a trial is hidden, the damage reaches far beyond one family. It erodes the ground on which such research is allowed to continue at all. The girl’s death was a tragedy. Hiding it was the deeper failure. Whether the school’s investigation answers for that, and in public, will say a good deal about whether the field has learned anything from this case.