Tofersen Shows Long-Term Efficacy in Rare Genetic ALS, Stabilizing Disease and Improving Function in Quarter of Patients
核心洞察
Long-term data from a phase 3 trial shows tofersen, an FDA-approved drug for SOD1-ALS (搜索), delays symptom progression and death over 3-5 years of treatment.
Approximately 25% of patients experienced stabilization or improvement in strength and respiratory function, unprecedented outcomes in this devastating neurological disease.
The antisense oligonucleotide drug targets the SOD1 (搜索) gene mutation affecting only 2% of ALS (搜索) cases but provides proof-of-concept for treating other ALS forms.
Long-term follow-up data from a pivotal phase 3 trial of tofersen demonstrates that the FDA-approved drug can stabilize disease progression and even improve function in patients with SOD1 (搜索)-related amyotrophic lateral sclerosis (搜索) (ALS (搜索)), offering unprecedented hope for a condition historically characterized by relentless neurological decline.
The study, published December 22 in JAMA Neurology and led by researchers at Washington University School of Medicine in St. Louis, followed 46 of the original 108 trial participants for 3.5 to 5.5 years. Results showed that approximately one-quarter of participants in the early-start group experienced stabilization of symptoms and functional improvement in grip strength and respiratory function.
"Stopping disease progression and making improvements over three to five years is unheard of in this type of ALS (搜索)," said first author Timothy M. Miller, MD, PhD, the David Clayson Professor of Neurology at WashU Medicine (搜索) and co-director of the WashU Medicine ALS Center. "Tofersen shows benefits compared with what we expect to see for these participants, with about 25% of participants experiencing improvement."
Targeting a Rare but Devastating Form of ALS
Tofersen is designed specifically for ALS (搜索) caused by variants in the SOD1 (搜索) gene, which accounts for approximately 2% of all ALS cases. The antisense oligonucleotide drug works by blocking production of the mutated SOD1 protein (搜索), interfering with the genetic material that tells the body how to make these harmful proteins.
About 20,000 people in the United States are living with ALS (搜索), also known as Lou Gehrig's disease (搜索). The average life expectancy for patients with SOD1-ALS (搜索) is typically two to three years from symptom onset. However, the new data suggests tofersen can significantly extend survival, with at least half of trial participants alive nearly five years from the study's start.
The drug received FDA approval in 2023 under an accelerated approval pathway based on earlier results showing reduced neurodegeneration. Tofersen is administered monthly via injection directly into the cerebrospinal fluid surrounding the spinal cord.
Real-World Impact on Patient Lives
The clinical benefits translate into meaningful improvements in patients' daily lives. Rickey Malloy, a 41-year-old plumber diagnosed with SOD1-ALS (搜索) in 2023, has been receiving tofersen for two years and reports significant improvements.
"I have far less muscle spasming and cramping in my legs — it's helped tremendously," Malloy said. "My physical therapy team has added more exercises and walking, and even stairs are getting easier. My goal is to be able to stand on my tiptoes again. I'm now building strength rather than just maintaining it."
Malloy's improvement has been so substantial that he recently underwent total knee replacement surgery that he had previously been told he didn't qualify for due to the severity of his ALS (搜索).
Similarly, Jessica Morris, a 37-year-old social worker and mother of three, experienced dramatic improvements after starting tofersen through FDA's expanded access pathway. Morris, who had deteriorated to the point of needing to crawl upstairs and requiring a wheelchair for daily activities, regained the ability to walk with just a cane.
"One night in March, I went to walk up my stairs, and my body just naturally took the step," Morris recalled. "It's like winning the lottery to have ALS (搜索) and to have this opportunity, to actually have a medication that not only is supposed to slow the progression but, [for] me, got me out of a wheelchair."
Study Design and Statistical Outcomes
The phase 3 trial initially lasted six months, comparing participants receiving tofersen with those receiving placebo. All participants were then offered tofersen in an open-label extension. While numerical trends favored those who started the drug earlier, differences between early-start and late-start groups did not reach statistical significance at three years.
Patients who received tofersen early showed a 48% reduction in risk of death within six months compared to patients who received placebo initially. The lack of statistical significance between groups is likely attributed to the study design, which allowed placebo participants to switch to tofersen after just six months, making it difficult to detect differences over several years of follow-up.
"The fact that participants in both groups are doing better than expected compared with knowledge of the typical natural course of the disease is further evidence of tofersen's efficacy," the researchers noted.
Safety Profile and Side Effects
The most common side effects included headache, procedural pain, falls, back pain, and extremity pain. Nine participants (9%) experienced more serious neurological side effects, primarily inflammatory in nature, which were successfully treated with additional therapies.
Broader Implications for ALS Treatment
The success of tofersen provides proof-of-concept that targeting underlying genetic causes can meaningfully alter ALS (搜索) progression. Miller and colleagues, including collaborators at UC San Diego and Ionis Pharmaceuticals (搜索), pioneered the antisense oligonucleotide approach, which is now being applied to other damaging proteins in different forms of ALS and neurodegenerative diseases.
"I think we know from this study that [some forms of] ALS (搜索) [are] treatable," Miller told ABC News. "I am very hopeful for a cure for ALS. And I think that we're going to find drugs that substantially slow down ALS, make it a livable disease that will be ongoing treatment."
A new multisite clinical trial is currently underway to evaluate whether tofersen can prevent or delay SOD1-ALS (搜索) in people who carry SOD1 (搜索) gene variants but are not yet showing symptoms. The trial is being led by Robert Bucelli, MD, PhD, at the WashU Medicine (搜索) site.
The Centers for Disease Control and Prevention estimates approximately 34,000 people in the U.S. currently live with ALS (搜索), with projections showing cases could rise to more than 36,000 by 2030, representing a 10% increase.