Tofersen (Qalsody)
Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive degeneration of upper and lower motor neurons, leading to muscle weakness, paralysis, and death typically within 2–5 years of symptom onset. While most ALS cases are sporadic, approximately 5–10% are familial, and mutations in the SOD1 gene account for about 20% of familial cases (roughly 2% of all ALS).
The SOD1 gene encodes superoxide dismutase 1, an enzyme involved in neutralizing reactive oxygen species. In ALS, SOD1 mutations cause the protein to misfold and aggregate, exerting a toxic gain of function that kills motor neurons. The disease mechanism is not loss of SOD1 enzymatic activity but rather the toxicity of the misfolded mutant protein — making gene silencing a logical therapeutic strategy.
Tofersen (Qalsody), developed by Ionis Pharmaceuticals and Biogen, was approved by the FDA in April 2023 under accelerated approval for the treatment of ALS associated with SOD1 mutations. It is a 2′-O-methoxyethyl (2′-MOE) phosphorothioate gapmer ASO that binds SOD1 mRNA and recruits RNase H to degrade it, reducing SOD1 protein levels in the central nervous system. Tofersen is administered intrathecally (by lumbar puncture).
Clinical trials demonstrated that Tofersen reduces SOD1 protein levels in cerebrospinal fluid by approximately 35% and reduces neurofilament light chain (NfL), a biomarker of neuronal damage. While the Phase 3 VALOR trial did not meet its primary endpoint (change in ALSFRS-R score at 28 weeks), biomarker data and longer-term follow-up suggested clinical benefit, particularly in patients treated earlier in their disease course.
Tofersen is a milestone for the ASO field because it is the first approved ASO for a neurodegenerative disease of the central nervous system delivered intrathecally. It demonstrated that ASOs can reach and silence gene expression in motor neurons when injected into the spinal fluid — a delivery route also used by Spinraza for SMA.
Over 200 different SOD1 mutations have been identified in ALS patients, with varying clinical presentations and progression rates. The most common include A4V (aggressive, predominantly lower motor neuron), D90A (slow progression), and H46R. While Tofersen targets a region of SOD1 mRNA common to all mutations, personalized ASO design can optimize sequences for individual patients’ genetic context.
Pequliar designs gene-silencing ASO candidates for SOD1-ALS, scoring candidates on binding affinity, structural accessibility, and off-target safety. In blind validation, the platform recovers the Tofersen (Qalsody) target sequence, reproducing in minutes the design that took years to develop. For patients seeking to evaluate additional candidate sequences or for research into next-generation SOD1-targeting ASOs, Pequliar provides synthesis-ready designs with full chemistry assignment.
Describe your mutation and get ranked, synthesis-ready ASO candidates in minutes. $399 per design.
Start a designPequliar is a computational research tool for informational purposes only. All sequences are computationally predicted candidates that have not been experimentally validated. Pequliar does not prescribe, recommend, or administer any compound. Independent validation by qualified professionals is required.