Nusinersen Improves Motor Function, Survival in Infants With Spinal Muscular Atrophy

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Improving survival and reducing motor disability are key endpoints for nusinersen treatment for SMA.
Improving survival and reducing motor disability are key endpoints for nusinersen treatment for SMA.

Infants with spinal muscular atrophy who receive nusinersen experience greater survival and motor function improvement compared with controls, according to findings from a randomized, double-blind, phase 3 study published in the New England Journal of Medicine.

Investigators randomly assigned infants with spinal muscular atrophy to receive either nusinersen (n=80) or a sham treatment (n=41). The primary end point was comprised of event-free survival and motor-milestone response.

At the prespecified interim analysis, the researchers observed a significantly greater proportion of infants in the nusinersen group vs the control group who achieved a motor-milestone response (41% vs 0%; P <.001). The findings of this interim analysis resulted in early trial termination.

Results of the final analysis demonstrated superiority of nusinersen vs sham treatment for achieving motor-milestone response (51% vs 0%). Event-free survival was significantly higher among patients taking nusinersen compared with controls (hazard ratio for death or the use of permanent-assisted ventilation 0.53; P =.005).

Additionally, infants who received nusinersen experienced a greater likelihood for overall survival compared with controls (HR for death 0.37; P =.004). Infants with a disease duration ≤13.1 weeks were more likely to experience greater event-free survival and overall survival with nusinersen treatment than infants with longer disease durations.

Although these findings display the potential survival benefits of nusinersen over sham therapy for infants with spinal muscular atrophy, none of the infants in this study achieved normal motor development, and many died during the treatment period. Therefore, the investigators suggest nusinersen represents only a possible approach for this disease and not a cure for symptomatic patients.

Because roughly half of the infants who received nusinersen underwent permanent-assisted ventilation within a 13-week period following the first medication dose, the investigators suggest the study “indicates that a minimum treatment time is required to see the full benefits of nusinersen…[and] suggests that early initiation of treatment may maximize its efficacy.”

Reference

Finkel RS, Mercuri E, Darras BT, et al. Nusinersen versus sham control in infantile-onset spinal muscular atrophy. N Engl J Med. 2017;377(18):1723-1732.

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