Tofersen, the first approved genetically targeted therapy for amyotrophic lateral sclerosis (ALS), demonstrates significant lowering of plasma neurofilament in adults carrying mutations in the superoxide dismutase 1 (SOD1) gene; however, additional biomarkers of treatment response in ALS are lacking. Here, we analyze longitudinally collected cerebrospinal fluid (CSF) samples from the phase 3 VALOR clinical trial to identify candidate tofersen treatment-response biomarkers in SOD1-ALS via quantitative proteomics. We observe significant modulation from baseline abundance for 56 proteins in tofersen-treated participants relative to placebo, including CSF GPNMB, which is significantly and continuously elevated across all post-baseline timepoints. We orthogonally confirm this observation by GPNMB immunoassay in independent tofersen-treated cohorts. Taken together, these data identify pharmacodynamic-response biomarkers of tofersen treatment that can be measured as early as 4 weeks post-treatment in SOD1-ALS patients and demonstrate the utility of leveraging unbiased proteomic screening integrated with targeted validation methods to identify pharmacodynamic-response biomarkers in clinical trial patient samples.
Guise et al. (Sun,) studied this question.