Case Study Highlights Benefit of Nusinersen in Late-Onset SMA

A patient case study is adding to the available, yet limited, data on how well nusinersen works in patients with late-onset spinal muscular atrophy (SMA).

The case study, involving a boy aged 13 years, showed that in a little over 1 year, the treatment yielded significant clinical benefit. Findings appeared recently in Medicine.

“Nusinersen showed an improved motor function in phase 3 randomized controlled trials that led to the drug’s approval in early-onset SMA, but evidence of favorable outcomes of nusinersen in older patients are insufficient and there is a need to investigate [it’s] effectiveness on late-onset SMA as well,” commented the researchers of the case study. “In accordance with this issue, the importance of this case is that it provides clinical evidence in the effectiveness of nusinersen in late-onset SMA.”

The patient had received an SMA diagnosis at the age of 3 years after he displayed proximal limb weakness. Tests demonstrated that he had elevated creatine kinase levels.

At 14 months of Nusinersen treatment, the patient demonstrated improvements in both the Hammersmith Functional Motor Scale Expanded (HFMSE) and 6-minute walk test. Motor scale ratings increased from 29 to 32 points and the walk test increased by nearly 30%, rising from 87.5 to 113 meters.

“In this study, there was significant improvement of HFMSE but the degree of improvement in SMA type 3 was less than that of SMA type 2 (+1.8 points vs +10.8 points) showing a modest efficacy of nusinersen in SMA type 3,” explained the researchers. “This can be easily understood by the natural history data of growth in SMA where there is significant worsening of symptoms during adolescence, where children with SMA between 5 and 15 years were more likely to experience weight gain and increased contractures and scoliosis and showed the largest numerical change of deterioration.”

According to the researchers, the patient did not experience a severe adverse event but did report a mild headache, although only after the first injection. The headache resolved following symptomatic treatment, allowing the nusinersen treatment to continue. Headache is one of the adverse events associated with nusinersen, along with back pain, nausea, constipation, and dizziness.

“More studies on late-onset SMA are needed to accurately understand the efficacy of nusinersen,” the authors concluded, “and our case adds to the favorable outcome in the categories of late-onset SMA patients.”

Reference

Park J-M, Min Y-S, Park D, Park J-S. Effect of Nusinersen in a late onset spinal muscular atrophy patient for 14 months. Medicine. Published online January 8, 2021. doi:10.1097/MD.0000000000024236