Gene Therapy Could Improve Survival for Spinal Muscular Atrophy

Two children with spinal muscular atrophy were able to walk without assistance after gene therapy.

An intravenous infusion of an investigational gene therapy was observed to extend the survival of patients with spinal muscular atrophy type 1 (SMA1), according to a study published in the New England Journal of Medicine.

The results of the phase 1 clinical trial may pave the way to a gene therapy for patients with the neuromuscular disorder.

“My team at Nationwide Children’s [Hospital] has worked with commitment and dedication to develop a therapy that may subsequently be shown through future clinical trials to potentially alter the course of this unforgiving condition and provide a therapeutic option for the families and infants with SMA1,” said principal investigator Jerry Mendell, MD.

SMA1 is a progressive pediatric disease that is caused by a single gene mutation. Patients typically die or require ventilation by age 2, according to the authors.

The authors noted that this is the first phase 1 clinical trial to test a gene therapy approach in patients with SMA1.

Included in the study were 15 patients with SMA1 who either received a high or low dose of modified adeno-associated virus serotype 9 (AAV9), which delivered the SMN gene. Of the 15 patients enrolled, 3 received a low dose, while 12 patients received a high dose of the gene therapy.

The authors discovered that patients treated with the high-dose gene therapy had improved motor function and had a reduced need for supportive care services compared with untreated patients, according to the study.

The gene therapy was found to have a favorable safety profile and was well-tolerated.

Approximately 92% of patients in the high-dose cohort achieved head control and 75% are now able to roll over. The authors also reported that 92% of patients are able to sit with assistance and 75% can sit for 30 seconds or longer, which was not possible before the treatment, according to the study.

Remarkably, 2 patients in the high-dose cohort have the ability to crawl, pull to stand, stand, and walk without assistance, according to the study.

Without intervention, patients typically require help breathing and eating by 1 year, and are not able to swallow or speak properly. The authors discovered that 11 patients are able to speak, 11 can eat, and 7 do not require help breathing, according to the study.

These findings suggest that the gene therapy may provide significant benefits to patients with SMA1.

“In this first phase of clinical trials, we have observed preliminary results that appear to be promising compared to the natural history of SMA Type 1,” Dr Mendell said.

In previous studies, the authors discovered that the AAV9 vector was able to cross the blood-brain barrier and could deliver the genes to motor neurons. When the therapy was administered to newborn SMA mice, the authors found that it prevented disease development.

The authors additionally found that the gene therapy was able to improve and stabilize the condition in large animal models of established SMA, according to the study.

“In neurological disease, it is rare to go from gene defect to therapy so directly, and the fact that this has happened here in one place is perhaps even rarer,” said John Kissel, MD, chair of Neurology at Ohio State and director of the SMA Clinic at Nationwide Children’s.