Patients with spinal muscular atrophy (SMA) treated with a one-time infusion of onasemnogene abeparvovec-xioi (Zolgensma®; AveXis) continue to show clinically meaningful benefits even 5 years after dosing, according to new data from the STR1VE-US, SPR1NT, and START trials.

Results from the pivotal open-label, single-arm, phase 3 STR1VE-US study evaluating onasemnogene showed that patients aged <2 years with SMA Type 1 experienced rapid, sustained and clinically meaningful improvements in motor function. Findings from the study demonstrated that 91% of patients (n=20/22) achieved event-free survival (co-primary end point) at 14 months, and 59% (n=13/22) achieved independent sitting for ≥30 seconds (co-primary end point) at 18 months. Moreover, 40.9% of patients (n=9/22) showed the “ability to thrive” (secondary end point) at 18 months, defined as not receiving nutrition through mechanical support or other non-oral method, having the ability to tolerate thin liquids, and being able to maintain weight.

Interim data from the ongoing open-label, single-arm, phase 3 SPR1NT study, which evaluated the efficacy and safety of onasemnogene in 29 pre-symptomatic infants aged <6 weeks with SMA and 2 or 3 copies of survival motor neuron 2 gene (SMN2), showed that among patients with 2 copies of SMN2, 7 out of 8 patients achieved the ability to sit independently (primary end point) within the World Health Organization (WHO) window of normal development. The 6 remaining patients in this cohort of 14 who have not yet passed are still within the developmental window. Most patients were within age-appropriate weight range and were fed orally; none of the patients required ventilatory support.

Lastly, new data from the long-term START study, which evaluated the efficacy and safety of onasemnogene in 12 SMA Type 1 patients with onset of clinical symptoms before 6 months of age, showed that all of the study participants were alive 5 years post-dose, free of permanent ventilation, and continued to maintain developmental milestones (2 patients achieved the new milestone of standing with assistance). 

“In complete contrast to the natural course of the disease, patients who received Zolgensma soon after birth before the onset of symptoms are achieving age-appropriate motor milestone development – an extraordinary outcome for SMA patients,” said Olga Santiago, MD, Chief Medical Officer, AveXis. “These SPR1NT data demonstrate the truly transformational impact a one-time dose of gene therapy can have, and further underscore the importance of newborn screening and early intervention to alter the course of the disease.”

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The STR1VE-US study findings were presented during a virtual Clinical Trial Session conducted by the Muscular Dystrophy Association (MDA) after the cancellation of the 2020 MDA Annual Conference due to COVID-19. Data from the SPR1NT and START studies will be published online by MDA in the coming weeks.

Zolgensma is currently approved for the treatment of pediatric patients <2yrs of age with SMA with bi-allelic mutations in the SMN1 gene.

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