Nusinersen treatment significantly improves hand grip strength, hand motor function and MRC sum scores in adult patients with spinal muscular atrophy types 3 and 4.

Abstract

Nusinersen recently became available as the first treatment for Spinal Muscular Atrophy (SMA) and data on its effectiveness and safety in adult SMA patients are still scarce. We evaluated the effectiveness and safety of nusinersen treatment during 14months in 16 adult patients with SMA types 3 and 4 in a prospective study, and retrospectively detailed the natural history of 48 adult SMA patients types 2, 3 and 4. Hand grip strength (p = 0.03), hand motor function (p = 0.04) as assessed by a sub-score of the Revised Upper Limb Module (RULM) and the Medical Research Council (MRC) sum score (p = 0.04) improved significantly at month 14. Importantly, the MRC sum score had declined significantly (p < 0.01) prior to start of treatment in these patients. A minimal clinically important difference (MCID) in the Hammersmith Functional Motor Scale Expanded (HFMSE) and RULM scores was achieved in 31% and 50% of the patients, respectively, but the mean changes from baseline failed to reach significance. Forced Vital Capacity (FVC) transiently increased at month 6 (p = 0.01), whereas the Peak Expiratory Flow (PEF) did not. The Activity Limitations scale declined significantly prior to start of treatment (p < 0.01) and showed an improvement with nusinersen which was not significant. The safety evaluation did not reveal serious adverse events and no signs of nephrotoxicity or antisense oligonucleotide (ASO)-mediated inflammation. We conclude that hand grip strength and hand motor function, as well as MRC sum scores improved significantly in nusinersen-treated adult patients with SMA types 3 and 4.