Selecting disease-modifying medications in 5q spinal muscular atrophy

Spinal muscular atrophy (SMA) is an inherited lower motor neuron disease. SMA occurs secondary to alterations in the survival motor neuron 1 gene (SMN1), which is the main driver of SMN protein production. The severity of the disease is determined by the number of copies of the SMN2 gene, which is a homolog to SMN1 but not as efficient in protein production. Three medications have recently been approved for the treatment of SMA. Nusinersen is an intrathecal antisense oligonucleotide that alters SMN2 pre-mRNA, onasemnogene abeparvovec-xioi is an intravenous SMN1 gene replacement therapy, and risdiplam is an oral small molecule splicing modifier of SMN2. No head-to-head studies have been conducted comparing these medications, so selection of one of these medications for an individual with SMA can be challenging. In this article we outline the efficacy, safety, and other pertinent factors to consider when selecting a therapy for an individual with SMA. The age of the individual and comorbidities, such as liver or kidney disease, help guide treatment choices. All three of these medications are efficacious, and early initiation is critical for obtaining the best outcomes.