Tofersen Treatment in SOD1-ALS: Real-World Evidence from a Retrospective Multicenter Study in France (FORSLA Study)

To evaluate the effectiveness of Tofersen in patients with superoxide dismutase 1 gene (SOD1-ALS) patients in France in a real-world setting, using disease progression within patient comparisons and with a historical cohort.

Patients with SOD1-ALS were included from across 19 French FILSLAN network centers. Baseline was defined as the treatment initiation date. Main endpoints were the ALSFRS-R progression rate and plasmatic neurofilament light chain (NfL) levels at baseline and 12 months after baseline.

In the Tofersen Cohort (N=46), within-group comparisons showed that the mean ALS functional rating scale revised (ALSFRS-R) progression rate slowed from 0.53 ± 0.5 at baseline to 0.22 ± 0.3 point/month at 12 months (P=.006). NfL levels significantly decreased from 89.0 ± 9.0 pg/ml at baseline to 29.2 ± 19.5.5 at 12 months (P=.004). Exploratory comparisons with a propensity score (PS) matched historical cohort (39 matched pairs) using a mixed-effects model, ALSFRS-R progression rate at baseline, 6 months, and 12 months after baseline, showed no statistically significant differences between groups P=.30, whereas longitudinal ALSFRS-R scores differed significantly between groups (time-treatment interaction P=.006). The mean survival of the PS matched population was longer in the Tofersen Cohort (42.6 months) than the Historical Cohort (31.8 months) P=.004. Time-dependent adjusted cox analysis showed that Tofersen was associated with a reduction in mortality risk (adjusted HR=0.34; 95% CI, 0.12-0.91; P=.03).

Tofersen seems to be associated with slower functional decline and reduced NfL levels. While limitations of retrospective design and ALSFRS-R sensitivity must be acknowledged, these findings provide real-world evidence suggesting a clinical benefit of Tofersen.