Early ALS Patients Show Slowed Decline with Pridopidine Treatment

Amyotrophic lateral sclerosis (ALS) remains one of neurology's most challenging conditions, with limited disease-modifying options and relentless progression for most patients. That’s why identifying which patients might benefit from emerging therapies, and when to intervene, could make a meaningful difference in their functional trajectory.

Today, we’re taking a quick look at subgroup findings from the HEALEY ALS Platform Trial. They suggest that pridopidine, a selective sigma-1 receptor agonist, may slow functional decline in patients with early and definite disease.

Let’s dive in.

Targeting an Enriched Population

The HEALEY ALS Platform Trial evaluated pridopidine 45 mg twice daily versus placebo in a randomized, double-blind phase 2 design. Although the overall trial did not meet its primary endpoint, a predefined subgroup analysis focused on patients with definite or probable ALS by El Escorial criteria who were less than 18 months from symptom onset. This enriched population comprised 37 participants on pridopidine and 35 on placebo.

The analysis targeted individuals most likely to benefit—those with confirmed diagnosis and early disease, before irreversible motor neuron loss limits therapeutic potential. This approach reflects a broader trend in ALS trials: refining patient selection to identify subgroups where treatment effects may be more detectable.

Functional and Respiratory Signals

At 24 weeks, pridopidine slowed decline in the ALS Functional Rating Scale-Revised (ALSFRS-R) total score by 32% compared with placebo (change from baseline: placebo -9.0, pridopidine -6.10; Δ2.90, 95% CI 0.32-5.49, p = 0.03). While nominally significant, the finding warrants cautious interpretation given the post hoc nature of the analysis.

Respiratory function showed more pronounced effects:

• ALSFRS-R respiratory domain: 62% slowing of decline at 24 weeks (Δ1.20, 95% CI 0.12-2.29, p = 0.03)
• Dyspnea subscore: 88% reduction in decline (Δ0.85, 95% CI 0.27-1.43, p = 0.005)

These respiratory metrics suggest preservation of function in a domain often associated with survival and quality of life. Respiratory decline typically marks a critical transition in ALS disease course, making stabilization in this area clinically relevant.

Bulbar Function and Speech Preservation

Bulbar involvement in ALS affects communication and swallowing, domains that significantly impact daily function. Pridopidine demonstrated a 40% slowing of bulbar decline, though this did not reach statistical significance (p = 0.06). More compelling were objective speech measures: articulation rate decline was reduced by approximately 93% (Δ0.43, 95% CI 0.18-0.68, p = 0.0007), and speaking rate decline was slowed by 70% (Δ0.43, 95% CI 0.16-0.7, p = 0.002).

These speech findings suggest functional preservation beyond what conventional ALSFRS-R subscores capture. For patients and families, maintaining communication ability holds particular importance as disease progresses.

Safety Profile Remains Favorable

Pridopidine was generally well tolerated, with a safety profile comparable to placebo. Treatment-emergent adverse events, serious adverse events, and discontinuations showed no clinically significant differences between groups. This tolerability profile supports continued investigation in larger trials.

Interpreting Subgroup Findings

These results should be interpreted with appropriate caution. The analysis was conducted in a limited sample size, 72 participants total, and represents a subgroup of the original trial population. Post hoc analyses carry inherent risks of false-positive findings due to multiple comparisons and patient selection. The enrichment strategy, while scientifically justified, means findings may not generalize to broader ALS populations or those with more advanced disease.

Additionally, long-term survival data from a delayed-start analysis suggested a potential benefit for early treatment initiation, though the hazard ratio of 0.429 approached but did not reach statistical significance (p = 0.052). Longer follow-up in prospective trials will be necessary to assess durability of functional benefit and impact on survival.

Looking Ahead: Refining Patient Selection

For clinicians managing early ALS, these findings offer a compelling signal. The subgroup enrichment approach—focusing on patients with definite diagnosis and disease duration under 18 months—may inform future trial design and patient selection for sigma-1 receptor modulation. If confirmed in prospective studies, pridopidine could potentially fill a gap for patients seeking disease-modifying options in the critical early disease window, particularly those experiencing respiratory or bulbar decline.

Reference

Geva M, Goldberg YP, Leitner ML, et al. Pridopidine treatment in ALS: subgroup analyses from the HEALEY ALS Platform trial. Amyotroph Lateral Scler Frontotemporal Degener. Published online December 17, 2025. doi:10.1080/21678421.2025.2597935