Currently, neurofilament light chain (NfL)3, 4 and phosphorylated neurofilament heavy chain (pNFH)5 are the most promising biomarkers for ALS and have been used as exploratory outcome measures in ALS clinical trials,6, 7 with treatment response reductions of NfL supportive for the recent FDA approval of QALSODY for ALS patients with SOD1 mutations.8 The gene discussed is NEFL; the disease is amyotrophic lateral sclerosis.