NFL is a marker of treatment response in children with SMA treated with nusinersen

Background Recently, the anti-sense oligonucleotide drug nusinersen was approved for spinal muscular atrophy (SMA) and our aim was to find a response marker for this treatment. Methods Twelve children with SMA type 1 and two copies of the SMN2 gene were included in a consecutive single-center study. The children were sampled for CSF at baseline and every time nusinersen was given intrathecally. The neuronal biomarkers NFL and tau and the glial biomarker GFAP were measured. Motor function was assessed using CHOP INTEND. Eleven similarly aged children, who were investigated to rule out neurological or infectious disease, were used as controls. Results Baseline levels of NFL (4598 ± 981 vs 148 ± 39, P = 0.001), tau (939 ± 159 vs 404 ± 86, P = 0.02), and GFAP (236 ± 44 vs 108 ± 26, P = 0.02) were significantly higher in SMA children than controls. Motor function improved by nusinersen treatment in median 13 points corresponding to 5.4 points per month of treatment ( P = 0.001). NFL levels typically normalized ( < 380 pg/ml) between the fourth and fifth doses [− 879.5 pg/mL/dose, 95% CI (− 1243.4, − 415.6), P = 0.0001], tau levels decreased [− 112.6 pg/mL/dose, 95% CI (− 206–7, − 18.6), P = 0.01], and minor decreases in GFAP were observed [− 16.9 pg/mL/dose, 95% CI (− 22.8, − 11.2), P = 0.02] by nusinersen treatment. Improvement in motor function correlated with reduced concentrations of NFL (rho = − 0.64, P = 0.03) and tau (rho = − 0.85, P = 0.0008) but not GFAP. Conclusions Nusinersen normalized the axonal damage marker NFL and correlated with motor improvement in children with SMA. NFL may, therefore, be a novel biomarker to monitor treatment response early in the disease course.