Gene therapy improved motor function in children with spinal muscle atrophy in the phase 3 STEER study of onasemnogene abeparvovec (OAV101 IT) in patients aged 2 to less than 18 years.

The trial enrolled more than 100 patients with type 2 SMA who had not received any prior treatment and could sit but not walk. 

"Maintaining motor function is a key goal for many older patients with SMA", as it allows them to perform daily activities as independently as possible, said Crystal Proud, MD, principal investigator at Children's Hospital of the King's Daughters.

In the 52-week study, patients who received the therapy showed improvement in measures such as sitting, rolling, crawling, and standing as measured on a commonly used scale, compared to those who received a sham procedure. Hammersmith Functional Motor Scale - Expanded (HFMSE) scores helped assess progress.

OAV101 IT showed a favorable safety profile with the most common side effects being upper respiratory tract infection, fever, and vomiting. Full data will be presented at a clinical meeting in 2025.

Other approved treatments include Biogen's spinal injection Spinraza, and Roche-PTC Therapeutics' oral drug Evrysdi.

SMA is the leading genetic cause of infant deaths and affects about 1 in 10,000 people, according to U.S. government data. The disorder is categorized into five types based on the onset of symptoms.