The U.S. Food and Drug Administration (FDA) has approved Novartis’ Itvisma® (onasemnogene abeparvovec-brve) for children aged two years and older, as well as teens and adults, living with spinal muscular atrophy (SMA) caused by a confirmed mutation in the SMN1 gene. The decision marks a major milestone as Itvisma becomes the first and only gene replacement therapy authorized for such a broad SMA patient population in the United States.
SMA is a rare, progressive neuromuscular disorder triggered by the absence or mutation of the SMN1 gene, which produces a protein essential for muscle function, movement, swallowing, and breathing. Without adequate SMN protein, motor neurons deteriorate, leading to severe muscle weakness. While the SMN2 gene can partially compensate, it produces only a small fraction of the necessary protein, resulting in significant clinical limitations for most patients.
Itvisma is designed to address the genetic root cause of SMA through a one-time fixed-dose gene replacement approach. Notably, the therapy does not require dose adjustments based on a patient’s age or weight, potentially simplifying administration and broadening accessibility. By restoring a functional copy of the SMN1 gene, Itvisma aims to improve motor function and reduce reliance on chronic therapies that require ongoing dosing.
Experts in neuromuscular medicine are calling the FDA approval a transformative moment.
“The FDA’s approval of intrathecal onasemnogene abeparvovec is a game-changing advance, expanding the use of transformational gene replacement therapy for SMA across age groups,” said Dr. John W. Day, Professor of Neurology and Pediatrics at Stanford University School of Medicine. He noted that this milestone not only advances SMA care but also opens new possibilities for treating other neurological and genetic diseases.
The FDA’s decision is supported by robust data from the registrational Phase III STEER trial and the open-label Phase IIIb STRENGTH study. The therapy demonstrated statistically significant improvements in motor function and, critically, stabilization of abilities not typically maintained in the natural progression of SMA. These effects remained sustained over 52 weeks of follow-up. Safety findings were consistent across both clinical trials, with the most common adverse events including upper respiratory tract infections, fever, common colds, and vomiting.
Advocacy groups also welcomed the approval as an overdue advancement for older SMA patients, who have historically had fewer therapeutic options.
“This new route of administration for a single dose of gene replacement therapy can mean so much more than what is measured by numbers on a functional motor scale—it could mean greater independence and freedom in daily life,” said Kenneth Hobby, President of Cure SMA. He added that the SMA treatment landscape has evolved rapidly over the past six years, and Itvisma’s approval represents additional progress toward addressing unmet needs.
An estimated 9,000 people in the United States live with SMA, and while treatment options have expanded in recent years, significant gaps remain—especially for older children, adolescents, and adults seeking to preserve motor neurons and maintain physical strength. The approval of Itvisma offers renewed hope for this wider patient community and reinforces the growing role of gene therapy in the future of neurological care.