A six-year-old girl with a rare genetic disorder died one week after receiving an experimental personalised gene-editing therapy in China. The previously undisclosed case has prompted an institutional investigation and renewed debate about patient safety, informed consent, research oversight, and transparency in first-in-human gene-editing studies.
A six-year-old girl with a rare neurodevelopmental disorder died seven days after receiving an experimental gene-editing therapy at Xinhua Hospital in Shanghai, according to a joint investigation by Science and Retraction Watch. The case, which remained undisclosed for more than a year, has drawn international attention after investigators reported that the child's death was not publicly disclosed and was not mentioned in a subsequent Nature paper describing the therapy's preclinical development.
Shanghai Jiao Tong University has since confirmed that it is investigating the circumstances surrounding the clinical trial. As of publication, no regulatory authority has publicly concluded that scientific misconduct occurred, and the university has not released the findings of its investigation.
Unlike earlier gene therapies that primarily add a functional copy of a gene, this experimental treatment attempted to correct a disease-causing DNA mutation directly inside the brain using base editing, an emerging form of CRISPR-derived genome editing. According to the Science investigation, researchers hoped the procedure would become the world's first personalised base-editing therapy directed at the central nervous system for a neurological genetic disorder.
The case has attracted global attention not only because of the child's death, but also because it has raised broader questions about how highly personalised gene-editing therapies should be evaluated before first-in-human use, how potential risks should be communicated to families, how serious adverse events should be reported, and how closely related preclinical research should be presented in the scientific literature.
The child, referred to by the pseudonym Mei to protect her identity, had Snijders Blok-Campeau syndrome, a rare neurodevelopmental disorder caused by a disease-causing variant in the CHD3 gene.
The condition has been reported in only a relatively small number of individuals worldwide. Children with the syndrome commonly experience developmental delay, speech and language impairment, low muscle tone, learning difficulties, and intellectual disability. Although the disorder can significantly affect daily functioning and quality of life, it is not generally considered a rapidly fatal condition. Current management focuses on supportive care, including speech therapy, occupational therapy, physiotherapy, and educational interventions, because no approved treatment can correct the underlying genetic mutation.
According to the joint investigation by Science and Retraction Watch, Mei's parents sought an experimental treatment after watching their daughter fall behind her classmates in kindergarten. She spoke in short sentences, required training chopsticks during meals, and struggled with developmental milestones expected for her age.
Genetic testing identified a single disease-causing mutation in the CHD3 gene. Investigators reported that one DNA base that should have been cytosine (C) had been replaced by thymine (T). Because the disorder resulted from a single-letter change in the genetic code, researchers believed it might be possible to correct that specific error rather than treat only the symptoms.
Unlike conventional medicines, which often manage the effects of a disease, gene-editing therapies aim to modify the underlying genetic sequence responsible for the condition. For families affected by ultra-rare disorders with no approved disease-modifying treatment, these experimental approaches may represent one of the few potential therapeutic options.
The treatment was developed by a research team led by Dr. Zilong Qiu, a neuroscientist at Shanghai Jiao Tong University's Songjiang Research Institute.
According to the Science investigation, the project proceeded under a Chinese regulatory pathway that allows certain investigator-initiated clinical research within hospitals without requiring approval from the country's national drug regulator. The pathway was designed to accelerate clinical innovation, but the events surrounding Mei's treatment have prompted renewed discussion about whether oversight mechanisms are sufficient for first-in-human gene-editing studies involving highly experimental personalised therapies.
The experimental treatment used in Mei's case was based on base editing, an emerging form of CRISPR-derived gene-editing technology designed to correct specific single-letter mutations in DNA.
To understand why researchers selected this approach, it is important to look at the type of mutation causing Mei's condition. According to the Science investigation, her CHD3 gene contained a single DNA base substitution, where thymine (T) had replaced cytosine (C). Because the disease resulted from a change in a single DNA "letter," researchers aimed to correct that specific error rather than replace the entire gene.
This is one of the situations in which base editing is considered particularly promising. Unlike some other gene-editing approaches that cut DNA before it is repaired, base editing chemically converts one DNA base into another without creating a double-stranded DNA break. Researchers hope this strategy may reduce certain risks associated with DNA cutting, although the technology remains under active investigation and its long-term safety continues to be evaluated.
Replacing the entire CHD3 gene would present additional scientific challenges because the gene is relatively large and tightly regulated within brain cells. Researchers have therefore explored whether correcting the specific disease-causing mutation could restore normal gene function while preserving the gene's natural regulation. This rationale has driven ongoing research into base editing for selected single-nucleotide disorders, although such therapies remain experimental.
Scientists had previously reported encouraging laboratory findings in mice and non-human primates before moving to human treatment. However, laboratory and animal studies cannot fully predict how an experimental therapy will behave in people. Every first-in-human study carries uncertainty, particularly when long-term human safety data are unavailable.
Several genome-editing technologies are currently being investigated for inherited diseases. Each has distinct strengths and limitations.
| Technology | How it works | Best suited for | Current clinical status |
|---|---|---|---|
| CRISPR-Cas9 | Cuts both strands of DNA before the cell repairs the break | Gene disruption, gene replacement, correction of some mutations | Used in multiple clinical trials. Some CRISPR-based therapies have received regulatory approval for selected diseases. |
| Base editing | Chemically converts one DNA base into another without creating a double-stranded DNA break | Single-letter DNA mutations | Early clinical development with limited human experience. |
| Prime editing | Uses a modified CRISPR system to rewrite short DNA sequences with greater flexibility | Broader range of small DNA changes | Primarily preclinical and early-stage research. |
Although these technologies differ in how they edit DNA, they all depend on delivering the editing machinery safely into the target cells. For neurological disorders, this remains one of the greatest scientific challenges.
According to the joint investigation by Science and Retraction Watch, researchers infused trillions of viral vectors carrying instructions for the customised base editor into Mei's cerebrospinal fluid. This route of administration, known as intrathecal delivery, was intended to allow the treatment to reach cells throughout the central nervous system.
The approach represented an important scientific milestone. If successful, it could have demonstrated that personalised base-editing therapies can directly target disease-causing mutations within the human brain.
Crossing the blood-brain barrier, a protective network of specialised cells that limits the entry of many medicines into the brain, remains one of the biggest obstacles in treating neurological disorders. Delivering therapies into the cerebrospinal fluid is one strategy researchers are investigating to improve access to the central nervous system.
However, introducing viral vectors into the body also presents safety challenges. Most current gene therapies use modified adeno-associated viruses (AAVs) because they efficiently deliver genetic material into cells. Although these viruses are engineered to be non-disease-causing, they can still trigger immune responses in some patients, particularly when large doses are required.
Researchers have previously reported immune-mediated complications following AAV-based gene therapy, including liver injury, thrombocytopenia, thrombotic microangiopathy, and multi-organ dysfunction. According to the hospital report reviewed by Science, Mei's death was most likely associated with a severe immune reaction to the viral vectors rather than the base-editing process itself. The complete clinical records have not been released publicly, and the institutional investigation remains ongoing.
Understanding the sequence of events helps place the investigation into context.
| Timeline | Reported event |
|---|---|
| Before March 2025 | Mei was diagnosed with Snijders Blok-Campeau syndrome caused by a CHD3 mutation. |
| Preclinical phase | Researchers developed a customised base editor and tested it in laboratory models, mice, and non-human primates before proposing human treatment. |
| 24 March 2025 | Mei received the personalised base-editing therapy at Xinhua Hospital in Shanghai through intrathecal administration. |
| Following treatment | Mei developed fever followed by signs of kidney injury, according to the Science investigation. |
| Seven days later | Mei died. A hospital report later concluded that the most likely cause was a severe immune reaction associated with the viral vectors. |
| Early 2026 | The research team published its preclinical findings in Nature. According to the Science investigation, the paper did not disclose Mei's death or the family's financial contribution. |
| July 2026 | Science and Retraction Watch published their joint investigation after reviewing documents and interviewing Mei's parents. |
| After publication | Shanghai Jiao Tong University confirmed that it had opened an investigation into the circumstances surrounding the clinical trial. |
The joint investigation by Science and Retraction Watch raised questions about how the potential benefits and risks of the experimental therapy were explained to Mei's family before treatment.
According to documents reviewed by Science, the child-friendly informed consent form described the treatment as an attempt to correct a small "mistake" in the child's genetic "book" before it became more serious. The form was designed to help families understand the scientific concept behind the therapy in simple language.
However, several independent experts interviewed by Science, including specialists in genetics, virology, gene therapy, and bioethics, questioned whether the available preclinical evidence was sufficient to justify proceeding with a first-in-human clinical intervention for a condition that is generally not considered immediately life-threatening.
Some experts also expressed concern that safety signals observed during preclinical animal studies may not have been fully reflected in discussions with the family before treatment. These observations represent expert opinions reported by Science and should not be interpreted as findings of scientific misconduct or conclusions of the ongoing institutional investigation.
Neither Dr. Zilong Qiu, Shanghai Jiao Tong University, nor Xinhua Hospital responded to multiple requests for comment from Science and Retraction Watch before publication of the investigation.
Mei's treatment represents an example of what researchers call a personalised or "n-of-1" gene therapy, meaning the therapy was designed specifically for a single patient rather than a larger group of individuals.
Advances in genome sequencing have made it possible to identify the exact genetic mutation responsible for many rare inherited disorders. In some cases, researchers can design a customised therapeutic approach that targets that specific mutation.
This strategy has attracted increasing interest because thousands of rare genetic diseases affect only a handful of patients worldwide. Developing a conventional medicine for each condition is often not commercially feasible, prompting researchers to explore personalised treatment approaches.
Earlier in 2025, researchers at the Children's Hospital of Philadelphia reported the successful use of a personalised base-editing therapy for an infant with carbamoyl phosphate synthetase 1 (CPS1) deficiency, a life-threatening metabolic disorder. That case demonstrated the potential of rapidly developing customised therapies for patients with ultra-rare diseases.
At the same time, personalised therapies introduce important scientific, ethical, and regulatory challenges. Because each treatment may be administered to only one patient, researchers often have limited human safety data before treatment begins. As a result, careful preclinical testing, independent ethical review, transparent informed consent, and close safety monitoring become particularly important.
The concerns raised following Mei's death extend beyond the outcome itself and focus on broader questions about how first-in-human personalised therapies should be evaluated.
According to the Science and Retraction Watch investigation, seven independent experts in genetics, virology, bioethics, and gene therapy reviewed documents related to the case.
Several questioned whether the available laboratory and animal data provided sufficient evidence to justify a first-in-human clinical trial. Others expressed concern about reported safety findings in non-human primate studies and whether those observations were adequately communicated to the family before treatment.
Some experts also questioned whether a highly experimental personalised gene-editing therapy should have been offered for a disorder that, although associated with lifelong disability, is generally not considered rapidly fatal.
The experts interviewed by Science emphasised that these concerns relate to the specific circumstances of this trial rather than to the field of gene editing as a whole.
Their comments should not be interpreted as evidence of scientific misconduct or as conclusions of the ongoing investigation by Shanghai Jiao Tong University.
Experimental therapies typically undergo several stages of scientific and ethical review before they are tested in people.
Researchers first conduct laboratory studies to determine whether a treatment works at the cellular level. Promising therapies then move to animal studies to evaluate effectiveness, determine appropriate dosing, and identify potential safety concerns.
Before a first-in-human clinical study begins, investigators generally prepare a detailed research protocol describing the treatment, participant eligibility, monitoring procedures, and plans for managing adverse events. Independent ethics committees or institutional review boards evaluate these protocols to determine whether the anticipated benefits justify the potential risks.
Participants, or in the case of children their legal guardians, are asked to provide informed consent after receiving information about the experimental nature of the therapy, potential benefits, known and unknown risks, available alternatives, and their right to withdraw from the study.
During the trial, researchers are expected to monitor participants closely for adverse events. Serious adverse events are generally reported to ethics committees, study sponsors, and regulatory authorities in accordance with national regulations and internationally recognised Good Clinical Practice guidelines.
Although regulatory systems differ across countries, these principles are widely regarded as fundamental safeguards for protecting participants enrolled in clinical research.
The investigation has also prompted discussion about publication ethics and scientific transparency.
According to Science and Retraction Watch, the research team published a paper in Nature in early 2026 describing preclinical studies of the customised base-editing strategy in mice and non-human primates. The published paper did not mention that a child had already received the therapy or that the patient had died following treatment.
The investigation further reported that earlier manuscript drafts referred to the family's financial contribution and the clinical translation of the research, but these references were removed before publication.
Following publication, Mei's parents reportedly asked the authors to withdraw the paper and later contacted Nature, arguing that the article did not fully reflect the circumstances surrounding the clinical programme.
In response to questions from Science, Nature stated that it had not been informed of Mei's death or the related ethical concerns during peer review. The journal indicated that questions regarding research oversight should be addressed through the relevant institution's investigation.
The case has led some researchers to question whether journals should be notified when serious adverse events occur in closely related clinical studies before or during publication of associated preclinical research. Others have emphasised that institutional investigations should establish the facts before editorial decisions are considered.
Although Mei's death has raised important questions about clinical research oversight, experts caution against drawing broad conclusions about gene editing as a therapeutic technology from a single experimental case.
Gene editing encompasses several different technologies, diseases, delivery methods, and clinical settings. Multiple approved gene therapies and emerging genome-editing treatments have demonstrated meaningful clinical benefits for selected inherited disorders after undergoing years of laboratory research, clinical trials, and regulatory review.
The treatment administered to Mei was a highly personalised, first-in-human experimental therapy designed for a single patient with an ultra-rare genetic disorder. As with many early-stage experimental interventions, important uncertainties remained regarding safety, dosing, and long-term outcomes.
Researchers continue to view gene editing as a promising area of medicine, but they also emphasise that each new therapy must undergo rigorous scientific evaluation, transparent reporting, and independent ethical oversight before it can become part of routine clinical care.
Beyond the clinical outcome, Mei's case has drawn attention to how serious adverse events are reported in biomedical research and how scientific journals, research institutions, and investigators communicate unexpected outcomes.
According to the joint investigation by Science and Retraction Watch, the research team published a paper in Nature in early 2026 describing preclinical studies of the customised base-editing strategy in mice and non-human primates. The published paper demonstrated proof of concept for the technology but did not disclose that a child had already received the therapy or that the patient had died following treatment.
The investigation further reported that earlier manuscript drafts referred to the family's financial contribution and the planned clinical translation of the research. Those references were removed before publication.
After the paper appeared in Nature, Mei's parents reportedly requested that the authors withdraw the publication and later contacted the journal, arguing that the article did not fully reflect the circumstances surrounding the clinical programme.
In response to questions from Science, Nature stated that it had not been informed of Mei's death or the related ethical concerns during peer review. The journal further stated that questions regarding research oversight should be addressed through the relevant institutional investigation.
The case has prompted discussion within the scientific community about whether journals should be informed when serious adverse events occur in closely related clinical studies before or during publication of associated preclinical research. At the same time, experts have noted that editorial decisions should be guided by verified findings from institutional investigations.
Transparency is widely recognised as a cornerstone of ethical clinical research.
Reporting serious adverse events allows clinicians, researchers, ethics committees, regulators, and future participants to better understand the safety profile of experimental therapies. It also enables other investigators to improve study design, refine patient selection, and strengthen safety monitoring in future research.
International standards, including the International Council for Harmonisation (ICH) Good Clinical Practice guideline and the Declaration of Helsinki, emphasise that investigators should appropriately document and report serious adverse events in accordance with applicable regulations and study protocols. Clinical trial registries also play an important role by making information about ongoing and completed studies publicly available.
Reporting requirements, however, vary depending on the regulatory framework under which a study is conducted. The ongoing investigation may clarify how these requirements applied in Mei's case.
Another aspect of the investigation that has attracted attention is the reported financial contribution made by Mei's family.
According to Science and Retraction Watch, the family contributed approximately US$860,000 toward developing the personalised treatment after using personal savings and financial support from relatives.
Developing a personalised gene-editing therapy is considerably more expensive than producing conventional medicines because each treatment requires customised laboratory development, manufacturing, quality testing, regulatory review, and clinical monitoring for an individual patient.
Many rare genetic disorders affect only a small number of people worldwide, making traditional commercial drug development difficult. Researchers, academic institutions, biotechnology companies, charitable organisations, and patient advocacy groups are therefore exploring alternative models to support the development of therapies for ultra-rare diseases while maintaining appropriate scientific and ethical standards.
According to the Science investigation, one member of the research team later returned more than US$100,000 to the family following Mei's death.
Gene therapy has advanced substantially over the past three decades, but the field has also experienced important setbacks that have shaped modern clinical research.
One of the best-known cases involved Jesse Gelsinger, an 18-year-old participant in a gene therapy study in the United States who died in 1999 after developing a severe immune response to an adenoviral vector. His death prompted widespread changes in clinical trial oversight, adverse event reporting, informed consent, and regulatory review.
Since then, improvements in vector engineering, manufacturing, patient selection, and clinical monitoring have contributed to the approval of several gene therapies for inherited retinal diseases, spinal muscular atrophy, haemophilia, sickle cell disease, beta thalassaemia, and other genetic disorders.
Genome editing has also entered clinical medicine. In recent years, regulatory authorities in several countries have approved the first CRISPR-based therapy for selected patients with sickle cell disease and transfusion-dependent beta thalassaemia following extensive clinical evaluation.
These advances demonstrate that gene-editing technologies can provide meaningful clinical benefit when supported by robust laboratory research, carefully designed clinical trials, and regulatory oversight.
As investigations continue, it is important to distinguish verified information from questions that remain unresolved.
Mei, a six-year-old girl with Snijders Blok-Campeau syndrome caused by a CHD3 mutation, received a personalised experimental base-editing therapy at Xinhua Hospital on 24 March 2025.
According to Science, the therapy was designed to correct a single disease-causing DNA mutation by delivering a customised base editor into the central nervous system.
Mei died seven days after treatment.
A hospital report reviewed by Science concluded that the most likely cause of death was a severe immune reaction associated with the viral vectors used to deliver the treatment.
Shanghai Jiao Tong University has confirmed that it is investigating the circumstances surrounding the clinical trial.
The published Nature paper describing the related preclinical work did not disclose the child's death or the family's financial contribution.
Nature told Science that it had not been informed about Mei's death during peer review.
The complete clinical records describing Mei's medical course after treatment have not been released publicly.
No peer-reviewed clinical case report describing the fatal event has been published.
The university investigation has not released its final findings.
No regulatory authority has publicly concluded that scientific misconduct occurred.
It remains unknown whether the related Nature paper will be corrected, updated, or retracted.
The precise biological mechanisms underlying the reported immune reaction have not been fully described publicly.
Mei's case illustrates both the promise and the challenges of precision genomic medicine.
Advances in genome sequencing, molecular biology, and gene editing have created opportunities to develop highly personalised therapies for diseases that previously had no disease-modifying treatment. For many families living with rare inherited disorders, these advances offer hope that was not possible only a decade ago.
At the same time, first-in-human therapies involve uncertainties that cannot be eliminated entirely through laboratory or animal studies. Every unexpected adverse event contributes to scientific understanding only when it is carefully investigated, transparently reported, and independently reviewed.
The ongoing investigation is therefore significant not only because it concerns one experimental treatment, but also because it may influence future discussions about oversight, informed consent, adverse event reporting, publication practices, and the responsible clinical translation of emerging gene-editing technologies.
As personalised gene-editing therapies continue to evolve, balancing scientific innovation with patient safety will remain a central challenge for researchers, clinicians, regulators, scientific journals, and families seeking new treatment options.
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