NEFL and amyotrophic lateral sclerosis: In clinical studies (NCT02623699, NCT03070119) designed to evaluate tofersen in symptomatic patients with SOD1-ALS, intrathecal administration of tofersen 100 mg led to robust reductions in total cerebrospinal fluid (CSF) SOD1 protein, a marker of target engagement, and plasma NfL, a marker of neuronal degeneration [22, 23].