In general, the gene therapy cut the children's brain levels of NAA (the chemical that goes out of control in Canavan), and slowed down their brain tissue degeneration. It also boosted their quality of life, Leone and her colleagues report in the Dec. 19 issue of the journal Science Translational Medicine.
That included small improvements in the children's muscle rigidity, sleep quality, ability to move and attentiveness. Some children started having fewer seizures.
Not all of the kids benefited equally, though, and age at treatment seems to be key.
Because no one knew how the gene therapy would work, the first several children who received it were older -- about 5 years old, on average -- and in a further state of brain degeneration. They showed the least improvement.
But as the trial continued, regulators let Leone's team treat younger children; the last few were 16 months old, on average, and included a 3-month-old. It was those younger children who showed the most benefit in terms of symptoms.
"The therapy should start as early in life as possible," Leone said.
Gene therapy, for any condition, is still experimental; no form of it is approved for use in the United States. The whole field suffered a huge setback in 1999, when a teenager participating in a clinical trial of gene therapy died from a severe immune system reaction to the cold virus used to deliver the gene.
The virus used in the current study was of a different type, considered unlikely to trigger an immune system response. None of the children had a serious immune reaction to the therapy -- though one child developed a fever and another a brain abscess after the initial surgery to infuse the gene.
"The safety findings, to me, are the most important part," said Dr. Maria Escolar, director of the program for the study of neurodevelopment in rare disorders at Children's Hospital of Pittsb
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