Nusinersen treatment of spinal muscular atrophy - a systematic review

5q spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder caused by insufficient survival motor neuron protein. Untreated SMA involves death or permanent respiratory support (type 1), inability to walk (type 2) or ability to walk (type 3). The incidence of SMA is 1 in 7,500 live births, equivalant to eight children being born with SMA in Denmark annually.

We undertook a systematic review of the efficacy of nusinersen as SMA treatment. We included randomised controlled trials and cohort studies. Our primary endpoints were survival without permanent respiratory support and change in motor function.

We identified 658 articles and included 13 of these (two randomised controlled trials and 11 cohort studies). Nusinersen increased survival without permanent respiratory support in SMA type 1 and increased motor function development in types 1-3. Nusinersen treatment before symptom onset in children with presymptomatic SMA produced near-normal motor development. So far, nusinersen has only minor safety concerns mostly related to the lumbar puncture.

Nusinersen increased survival without permanent ventilatory support in children with SMA type 1. Improvements in SMA type 2 and 3 were less evident. Better outcomes were seen in young children with a short disease duration, particularly in children receiving nusinersen before symptom onset. Newborn SMA screening may facilitate presymptomatic treatment with splice modification (nusinersen, risdiplam) or gene implantation therapy (AVXS-101, zolgensma).