Transitioning From Nusinersen to Risdiplam for Spinal Muscular Atrophy in Clinical Practice: A Single-Center Experience.

Background: Nusinersen and risdiplam are U.S. Food and Drug Administration (FDA)-approved treatments for spinal muscular atrophy (SMA). No head-to-head clinical trials to assess efficacy exist. Observational studies are needed to determine if transitioning to risdiplam is safe and efficacious.

Methods: This retrospective study at Nationwide Children's Hospital included individuals with SMA treated with nusinersen who switched to risdiplam. Motor, pulmonary and bulbar function were assessed before and 2 years after nusinersen and risdiplam initiation.

Results: Forty-four individuals were included: 11 with SMA type 1, 25 with SMA type 2 and 8 with SMA type 3. Motor function improved after initiation of nusinersen treatment with the most significant improvements seen in the first year. After transition to risdiplam, motor function remained largely stable. Need for noninvasive ventilation (NIV) overnight occurred in both groups. Cough peak flow significantly improved in the risdiplam group. Hospitalizations were the same in both groups. One individual in the nusinersen group gained the ability to take some food by mouth; two individuals in the risdiplam group achieved some oral feeding and two became exclusively orally fed.

Conclusions: As expected, motor function was most improved in treatment naïve individuals in the first year after nusinersen initiation. Over half of our study population had posterior spinal fusion surgery (57%) which significantly impacted motor and respiratory outcomes, though slightly less so in the risdiplam group. Overall, our data demonstrates that transitioning from nusinersen to risdiplam is associated with a favorable safety profile and stable motor outcomes.