WASHINGTON, United States (AFP) — A six-year-old Chinese girl died last year after receiving an experimental gene-therapy to correct a non-life-threatening condition, according to an investigation by Science and Retraction Watch.

The girl, given the pseudonym “Mei,” died a week after receiving a spinal infusion of trillions of viruses last March designed to penetrate the brain and fix a rare genetic condition that caused her mild cognitive impairment, the report said Thursday.

But her parents, who paid more than $800,000 to fund the experiment, were not adequately informed about the risks, the report said.

The lead researcher went on to publish a paper on related animal studies in the prestigious journal Nature that made no mention of Mei, who had a rare genetic condition called Snijders Blok-Campeau syndrome, known to affect just 237 people worldwide.

Most affected individuals have larger-than-normal heads and intellectual deficits.

, though the extent varies widely.

For Mei, this meant still speaking in simple sentences at age six and eating with training chopsticks, though speech and occupational therapy was helping.

The trial was led by neuroscientist Zilong Qiu, one of several researchers globally racing to turn base editors -- a more precise form of the CRISPR gene editor -- into custom treatments for children with rare genetic conditions.

Just a month earlier, an infant with a life-threatening metabolic disorder successfully received such a treatment at the Children’s Hospital of Philadelphia.

With Mei’s treatment, Qiu was aiming for the world’s first ever gene-editing therapy directed at the brain, rewriting the mutated gene in her neurons so she could make a vital protein.

Instead she died a week later from a severe immune reaction.

Seven experts who reviewed the details for Science and Retraction Watch said Qiu and his team downplayed the trial’s risks and went ahead despite low odds of success.

They also called for a full review of the data submitted for the Nature paper, saying some findings could warrant a retraction.

The case also raises questions about whether such risky treatments should be initially tested on patients with nonfatal conditions.

In 1999, the death of 18-year-old Jesse Gelsinger, who received gene therapy for a genetic disease of the liver despite having a milder form, chilled research in the field for the next decade.