Pediatric and adult spinal muscular atrophy (SMA) type 3 patients showed improved Hammersmith Functional Motor Scale Expanded (HFMSE) and Revised Upper Limb Module (RULM) scores after 12 months of treatment with nusinersen (Spinraza®). The “findings expand the available data on the effect of nusinersen on type 3 patients, so far mostly limited to adult patients,” the authors stated.
Out of the 144 patients that constituted the original cohort, 12-month analyses were performed in 104 (72.22%) for the HFMSE and 100 (69.44%) for the RULM. Both scores significantly increased from baseline to 12 months, with a mean difference of 1.18 (95% CI, 0.37‑1.99, P =.004) for the HFMSE score and 0.58 (95% CI, 0.12‑1.04, P =.014) for the RULM score.
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The improvement in the HFMSE score was significant in the pediatric group (mean difference = 1.53, 95% CI, 0.34‑2.72, P =.0123), ambulant (mean difference = 1.06, 95% CI, 0.08‑2.04, P =.034), nonambulant (mean difference = 1.48, 95% CI, 0.09‑2.88, P =.038), and type 3b patients (mean difference = 1.33, 95% CI, 0.53‑2.12, P =.001), but not in adult and type 3a patients. According to the longitudinal multivariable data analysis, age, SMA functional status, HFMSE at baseline, and SMA 3 subtype were contributing factors to the changes.
The mean HFMSE 12-month changes were mostly positive in treated patients aged more than 7 years, with only a few individuals presenting negative changes, in contrast to age-matched untreated patients who showed no improvement in a 12-month HFMSE longitudinal investigation published in Annals of Neurology.
Pediatric (mean difference = 1.26, 95% CI, 0.55‑1.97, P =.0007), nonambulant (mean difference = 0.95, 95% CI, 0.24‑1.66, P =.0009), and type 3a (mean difference = 1.25, 95% CI, 0.54‑1.96, P =.001) patients also showed a significant 12-month RULM increase. Age and RULM at baseline were found as contributing factors to the changes in the longitudinal multivariable data analysis.
No significant improvement was found in the 6-Minute Walk Test (6MWT) mean score (mean difference = 6.65, 95% CI, ‑7.08‑20.37, P =.339) between the 2 assessments, despite the increasing trend in both type 3a and 3b patients. According to the longitudinal multivariable data analysis, age and 6MWT at baseline were contributing factors to the changes.
The results of this study corroborated previous findings in adults and supported the existence of a 12-month nusinersen treatment effect on at least 1 functional measure of SMA type 3 patients.
Pera MC, Coratti G, Bovis F, et al. Nusinersen in pediatric and adult patients with type III spinal muscular atrophy. Ann Clin Transl Neurol. Published online June 24, 2021. doi:10.1002/acn3.51411
Coratti G, Messina S, Lucibello S, et al. Clinical variability in spinal muscular atrophy type III. Ann Neurol. 2020;88(6):1109-1117. doi:10.1002/ana.25900