A six-year-old girl suffering from a rare genetic disease that caused intellectual disability and autism died after receiving experimental therapy for her condition in China. The girl’s death had not been disclosed by either the hospital where she was treated or the university that developed the therapy, according to an investigation by the news team of Science magazine and the Retraction Watch portal.
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The girl’s parents had raised over $800,000 to enable scientists and doctors to develop a specific gene therapy for their daughter. This was one of the (n=1) type trials, with a single patient and a treatment created specifically for them. In this case, it was a single mutation, a single chemical letter typo, an A instead of a G, in her genome composed of 3 billion chemical letters.
The death of this patient is a blow to the entire field of gene therapy, which is achieving historic results in the treatment of very serious genetic diseases. The case comes years after China was at the center of one of the biggest scandals in world science, when in 2018 scientist He Jiankui edited the genome of three babies without valid justification, creating the first human beings with modified genomes and putting them at risk of serious diseases caused by imperfect genomic editing techniques. Jiankui ended up in prison and China tightened controls for such human trials. To this day, the health status, whereabouts, or any other data of the three children born from these delusional experiments are some of China’s best-kept secrets.
That single typo in the CHD3 gene caused Snijders Blok-Campeau syndrome in the girl, a rare neurological and developmental disorder — only 237 cases are known worldwide — and non-degenerative, which affected her cognitive abilities. The girl received gene therapy in March 2025 at Xinhua Hospital in Shanghai through an injection into the cerebrospinal fluid surrounding the brain and spinal cord. The treatment contained deactivated viruses that were supposed to transport a base-editing therapy to the brain. This type of genetic editing is an evolution of the CRISPR system that is capable of selectively correcting single-letter typos in the genome. The girl suffered a severe immune reaction after receiving the treatment and died a few days later. An internal hospital investigation confirmed that the cause of her death was the injection of the therapy, according to the investigation published on Thursday.
In 2023, the girl’s parents, in search of a possible treatment, had found Zilong Qiu, a prestigious neuroscientist from Shanghai Jiao Tong University School of Medicine, on a WeChat messaging network forum, who offered to develop a therapy for the little girl. The researcher is a member of the Chinese National Academy of Sciences and has been trying for years to develop gene therapies against Rett syndrome, a rare disease that causes autism in young children. The parents themselves financed the previous research work to develop mice with their daughter’s mutation and conduct preclinical experiments, first in rodents, and then in monkeys.
With the apparently positive results of these experiments, Qiu’s team requested permission to administer the treatment as part of a single-patient clinical trial. The team resorted to a legal loophole in China that allows certain non-commercial, researcher-driven trials to not require permission from national authorities, who apply stricter criteria, but only from local ones.
The parents did not take action regarding their daughter’s death until they saw a study by Qiu’s team published in Nature that described the new gene therapy but did not mention that the mutation in question was their daughter’s, nor did it warn of the clinical trial or its fatal outcome. The parents had many of their conversations with Qiu recorded, which have now been analyzed by Science and Retraction Watch.
The investigation shows that research with mice and monkeys uncovered potential harms of the therapy that should have halted the project and led to more animal trials, according to several experts, including one of the reviewers of the study published in Nature. Despite this, Qiu’s team went ahead with the trial.
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The developed therapy consists of trillions of deactivated adeno-associated viruses that carry the base editor inside them. Given the size of the repairing genetic sequence, the team had to split it into two, and include one half in one part of the viruses and the other half in the other. Both variants had to reach the brain and penetrate the neurons and correct the typo in one of the two helices that make up the genome, precisely where the mutation is located. The natural DNA repair mechanisms would correct the second arm of the double helix, which in theory would cure the girl’s disease.
Shortly after receiving the injection, the patient had a fever. This was expected, but her immune reaction worsened to the point of paroxysm and ended her life. Although the hospital concluded that the death was due to an immune reaction caused by the treatment, the girl’s death was not disclosed. The responsible researchers, led by Qiu, were not sanctioned or removed from their positions. A few months later, regional authorities fined the hospital about $3,500. Neuroscientist Zilong Qiu was one of dozens of Chinese scientists who condemned He Jiankui’s absurd experiments.
The publication of the study in Nature prompted the girl’s parents to bring the case to light. Several experts question the validity of the work and call for its retraction from the journal.
This is one of the hardest blows for an emerging field. The case is reminiscent of the death of Jesse Gelsinger, an 18-year-old patient who died in 1999 during a pioneering gene therapy trial in the United States. The responsible university had to pay a fine of half a million dollars, and the principal investigator was disqualified for five years for not having clearly informed of the risks involved in the treatment. This death halted gene therapy research for years.
This approach has finally succeeded in recent years, thanks in part to new genetic editing technologies. For the first time, they have made it possible to cure incurable diseases once and for all in pioneering clinical trials. According to the investigation published this Thursday, it is possible that Qiu and the rest of the team did not clearly explain the risks of the therapy to the parents.
“This is a problem in China, where things like this have happened before and have happened again,” says Marcelo Bellusci, a pediatrician at Hospital 12 de Octubre who participates in several gene therapy trials for rare diseases. “In these types of trials, serious side effects are possible, but the family is always informed. This team has violated all current regulations,” he adds. The pediatrician believes that this tragedy “should not” affect the development of the field. Although it is still unclear, it seems that such an immune reaction was probably due to the associated adenoviruses rather than the gene therapy itself. And these types of vectors are widely used in therapies that have proven effective, including one already approved to treat spinal muscular atrophy,” he points out. “Gene therapy is in an early stage of development; it is essential that everything is done in an environment not biased by personal ambitions, with maximum guarantee for patients and by the scientific community itself. It is almost certain that this specific treatment in China was not ready to proceed to human trials,” he adds.