Tofersen: A Novel Option for the Treatment of Amyotrophic Lateral Sclerosis

Objective: This review summarizes current evidence on the efficacy and safety of tofersen (Qalsody) in treating amyotrophic lateral sclerosis (ALS). Data Sources: PubMed, MEDLINE, Google Scholar, and ClinicalTrials.gov were searched using the keywords: Qalsody , BIIB067 , antisense oligonucleotides , SOD1 , and amyotrophic lateral sclerosis . Articles published from inception to November 2025 were included. Study Selection and Data Extraction: English-language studies assessing the pharmacokinetics, pharmacology, efficacy, and safety of tofersen were included. Prescribing information and real-world evidence were also reviewed. Data Synthesis: Tofersen is an intrathecally administered antisense oligonucleotide targeting superoxide dismutase 1 (SOD1) mRNA. Early trials demonstrate dose-dependent reductions in cerebrospinal fluid (CSF) SOD1 protein levels of −33% and slower ALS Functional Rating Scale (ALSFRS-R) decline compared to placebo (−1.19 vs −5.63 points). In Phase 3 trials, tofersen reduced CSF SOD1 by 29% and plasma neurofilament light chain (NfL) by 60%, while biomarkers increased in the placebo group. There was no significant difference in ALSFRS-R decline between tofersen and placebo (−6.98 vs −8.14; P = 0.97). Real-world data show favorable patient-related outcomes and improvement in ALSFRS-R. Adverse effects are primarily lumbar puncture related with serious neurologic events documented in 7% of tofersen recipients. Relevance to Patient Care and Clinical Practice in Comparison to Existing Drugs: As the first Food and Drug Administration (FDA)-approved gene-directed therapy for SOD1 ALS, tofersen directly targets the underlying genetic cause. Barriers include the need for genetic confirmation and intrathecal administration. Conclusion: Tofersen provides a promising targeted treatment option for pathogenic SOD1 ALS. Ongoing studies will clarify its long-term clinical impact.