It's hard to know how much of the symptom improvement, and overall survival, was due to the gene therapy itself, Escolar said. Advances in how doctors care for kids' complications, such as pneumonia, might have affected survival rates.
Still, Escolar said, "the safety findings, alone, are a huge step forward."
Since this trial began, scientists have also made advances in the viral vectors that could be used for gene therapy. Better ones, that may not need to be directly infused into the brain, are under study in animals -- and close to being studied in humans, Escolar noted.
"Now this study needs to be repeated using better vectors, along with better natural history data," Escolar said.
Gene therapy is not the only approach to Canavan under study, said Morris Baslow, a scientist at the Nathan S. Kline Institute for Psychiatric Research in Orangeburg, N.Y.
Other research groups, he said, are trying to better understand how the chemical NAA works in the brain, and hopefully come up with other approaches to treat Canavan disease, including medications.
When it comes to gene therapy, Baslow agreed that it should start very early, soon after birth. He also said the "ideal" method would be to use a viral vector that specifically targets brain cells called oligodendrocytes -- which are responsible for making the protective sheaths around nerves.
Leone agreed that that type of vector would be better. But it doesn't exist yet.
Ultimately, a combination of therapies may be needed to best treat, or even cure, Canavan disease. "Our feeling is, in the future, gene therapy in association with medication that targets the metabolism of [brain] cells will be the cure," Leone said.
Learn more about Canavan disease from the Canavan Research Foundation.
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