ALS Treatment: Riluzole, Tofersen, and Realistic Expectations

The Clinical Problem in ALS Treatment

Amyotrophic lateral sclerosis (ALS) destroys the motor neurons that drive voluntary movement. Weakness spreads relentlessly until breathing fails. Across population registries, median survival is roughly two to three years from symptom onset, and respiratory failure causes most deaths.

This biology shapes what any ALS treatment can realistically achieve. No approved therapy stops or reverses the disease. The achievable goals are slowing functional decline, extending survival modestly, and protecting quality of life for as long as possible.

Two drugs frame current expectations: riluzole, approved three decades ago, and tofersen, the newest and first genetically targeted option. Their contrasting stories — alongside one cautionary withdrawal — show why careful expectation-setting is central to good ALS treatment.

Available ALS Treatment Approaches

Four disease-directed drugs have reached approval in ALS, alongside supportive interventions such as non-invasive ventilation. The table summarises the verified trial evidence for each, with confidence tiers marking where a figure is drawn from a primary source.

Riluzole — A Modest but Real Survival Benefit

Riluzole, a glutamate-signalling modulator approved in 1995, remains the most evidence-backed ALS treatment. Pooled across randomised trials, it reduces the risk of death and prolongs median survival by about two to three months — an estimated 9% increase in one-year survival.

When the more heterogeneous trial of older, more advanced patients is added to the pooled survival analysis, the effect is smaller but still significant (HR 0.84, 95% CI 0.698–0.997). Real-world cohort data suggest earlier initiation is associated with greater absolute survival gain, though the effect remains modest. Riluzole is well tolerated, and its benefit is small but consistently replicated.

Edaravone — Benefit in a Narrow Population

Edaravone, an antioxidant approved in 2017, slowed functional decline in the pivotal Study 19: an ALSFRS-R difference of 2.49 points over 24 weeks. That result, however, emerged only after enriching the trial for a narrow group — early disease, preserved vital capacity, and a defined rate of progression.

An earlier phase 3 study in a broader population had already failed. The trial authors were explicit that there is no evidence edaravone helps patients who fall outside these criteria. Its place in ALS treatment is therefore real but limited.

Tofersen — Targeting a Genetic Cause

About 2% of ALS is caused by mutations in the SOD1 gene, which produce a toxic protein. Tofersen is an antisense oligonucleotide that lowers SOD1 production. In the phase 3 VALOR trial, it did not meet its primary endpoint: the ALSFRS-R difference at 28 weeks was 1.2 points (95% CI −3.2 to 5.5).

Because that pre-specified test failed, all secondary clinical endpoints were treated as non-significant. Yet the drug’s effect on disease biomarkers was strong and consistent — a pattern that reshaped how it was evaluated.

A 12-month open-label analysis suggested that earlier tofersen slowed decline versus delayed start (ALSFRS-R difference 3.5 points, 95% CI 0.4–6.7). Those figures were exploratory and not adjusted for multiple comparisons. In April 2023 the FDA granted accelerated approval based on the neurofilament reduction — a surrogate marker — not on proven clinical benefit.

The confirmatory ATLAS trial, testing tofersen in people who carry an SOD1 mutation but are not yet symptomatic, is ongoing and expected to report around 2027. Serious neurologic events, including inflammation of the spinal cord, were reported in a minority of treated patients. Tofersen is best described as a scientific milestone whose clinical value is still being confirmed.

When Approval Outpaces Evidence — The AMX0035 Story

Sodium phenylbutyrate–taurursodiol (AMX0035, marketed as Relyvrio) offers the clearest recent lesson in expectation-setting. In the phase 2 CENTAUR trial, it slowed ALSFRS-R decline by 0.42 points per month (95% CI 0.03–0.81; P=0.03), and the drug was approved in 2022 after intense debate.

The confirmatory phase 3 PHOENIX trial, enrolling 664 patients, then failed to meet its primary and secondary endpoints (reported P=0.667 for the functional outcome). The manufacturer withdrew the drug from the market in 2024, offering continued supply free of charge to existing patients.

Comparative Analysis

Placed side by side, the disease-directed options fall into distinct tiers. Riluzole offers a small, replicated survival benefit. Edaravone slows function in a narrow group with no proven survival effect. Tofersen shows a strong biomarker effect but unproven clinical benefit. AMX0035 failed confirmation and is gone.

One comparison is striking. In the Bourke trial, non-invasive ventilation extended median survival by 205 days — roughly seven months — in patients without severe bulbar weakness. The authors noted this survival benefit is much greater than that from available neuroprotective drugs.

These trials are not head-to-head; populations, endpoints, and eras differ, so the numbers cannot be subtracted from one another. The consistent pattern, though, is instructive: modest drug effects, a meaningful respiratory-care effect, and one genetic therapy whose clinical worth remains under test.

Quality and Consistency of the Evidence

• Riluzole survival benefit — reasonably strong, consistent. Multiple randomised trials and a Cochrane meta-analysis agree on a small but real effect; heterogeneity appears mainly when advanced patients are included.
• Edaravone functional benefit — moderate but narrow. A single positive RCT in an enriched subgroup; an earlier broad-population trial was negative, and survival benefit is unproven.
• Tofersen biology — strong; tofersen clinical benefit — low certainty. The neurofilament and SOD1 effects are large and reproducible; the clinical primary endpoint was missed, and confirmation awaits ATLAS.
• AMX0035 — negative on confirmation. An initial phase 2 signal did not replicate in a larger phase 3 trial; the drug was withdrawn.
• Non-invasive ventilation — moderate-to-strong, consistent. Randomised and cohort data agree on survival and quality-of-life benefit in patients without severe bulbar impairment.

What the Evidence Does Not Show

Being specific about the gaps is as important as reporting the benefits, because it defines what patients can and cannot expect from ALS treatment.

• No approved therapy halts, reverses, or cures ALS; every proven effect is a matter of slowing, not stopping.
• Whether combining riluzole and edaravone adds benefit has not been settled by a robust randomised trial.
• Tofersen’s effect on survival and long-term function is unproven pending the ATLAS trial, and it has no established role outside SOD1-mutation ALS.
• Edaravone’s value outside the narrow Study 19 population is unproven, and long-term comparative survival data for its oral form are limited.
• There is no validated way to predict which individual patient will respond to a given drug.

Practical Implications

The evidence supports several practice considerations that keep expectations aligned with what ALS treatment can deliver.

• Offer riluzole early and frame it honestly. The benefit is measured in months, and starting sooner is associated with greater absolute survival gain.
• Test for SOD1. Genetic testing and counselling identify the ~2% of patients for whom tofersen is relevant; it has no role for others.
• Prioritise respiratory surveillance and timely non-invasive ventilation. The evidence points to this as one of the largest available levers on survival.
• Use multidisciplinary clinics. Coordinated care is associated with better survival than any single drug in isolation.
• Communicate transparently about biomarker-based approval and the AMX0035 lesson, and involve palliative care early rather than at the end.

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