Within 13 days after the injection, 90 percent of the treated mice had the muscle coordination needed to right themselves as quickly as normal animals. By this time, untreated SMA mice already were suffering symptoms that left them unable to right themselves. The day-1 treated mice also were nearly identical to normal mice in their ability to run on a wheel.
In the case of restored nerve impulses, 90 days after the gene therapy, there was no difference in nerve pulses between the treated SMA mice and normal mice, which indicated that the nerves to muscle developed correctly.
The treated SMA mice also gained weight and lived substantially longer than untreated mice with the disease, and some mice were still alive when the paper was submitted 250 days after they received the treatment, Kaspar said.
Improvements this dramatic were seen only in the mice that received SMN on their first two days of life. Later delivery reduced the impact of correction.
"We don't yet know the exact window of when it is capable of getting into the right cells in a human. Is it a month after birth, or a week after birth? That's still a question," Kaspar said.
Complicating this issue is the fact that symptoms of spinal muscular atrophy aren't typically apparent in infants, and the only existing newborn screening technique has not been implemented because it is considered prohibitively expensive.
"So if you have a technique that needs to be delivered early, then you need a newborn screening," Burghes noted.
The researchers hope to progress to human clinical trials of this gene therapy technique as soon as the requisite toxicology experiments are in place and federal regulators will allow. This study should help move the process along because of its inclusion of a single viral vector treatment of a 1-day-old macaque with the green fluo
|Contact: Arthur Burghes|
Ohio State University