nct07322003

Pridopidine Phase 3 Study in Amyotrophic Lateral Sclerosis (NCT07322003)

Overview

Pridopidine is a novel small molecule sigma-1 receptor (σ1R) agonist being developed by Prilenia Therapeutics for the treatment of amyotrophic lateral sclerosis (ALS). The Phase 3 trial (NCT07322003) represents one of the most advanced clinical programs targeting the sigma-1 receptor in ALS, a protein implicated in cellular homeostasis, calcium regulation, and neuroprotection.

This randomized, double-blind, placebo-controlled trial aims to evaluate the efficacy and safety of pridopidine in approximately 500 participants with ALS over a 48-week treatment period. The trial uses the Revised ALS Functional Rating Scale (ALSFRS-R) as the primary endpoint, with the primary analysis focusing on change from baseline through Week 26 and Week 48, adjusted for mortality[@prilenia].

Trial Details

| Parameter | Value |
|-----------|-------|
| NCT Number | NCT07322003 |
| Phase | Phase 3 |
| Status | RECRUITING (as of early 2026) |
| Sponsor | Prilenia Therapeutics |
| Enrollment | 500 participants (estimated) |
| Enrollment Type | ESTIMATED |
| Study Type | INTERVENTIONAL |
| Allocation | Randomized, double-blind, placebo-controlled |
| Start Date | February 2026 |
| Completion Date | March 2029 |
| Last Updated | February 2026 |

Conditions Studied

• Amyotrophic Lateral Sclerosis (ALS)
• Also known as Lou Gehrig's disease or motor neuron disease

Mechanism of Action

Sigma-1 Receptor Agonism

...

Pridopidine Phase 3 Study in Amyotrophic Lateral Sclerosis (NCT07322003)

Overview

Pridopidine is a novel small molecule sigma-1 receptor (σ1R) agonist being developed by Prilenia Therapeutics for the treatment of amyotrophic lateral sclerosis (ALS). The Phase 3 trial (NCT07322003) represents one of the most advanced clinical programs targeting the sigma-1 receptor in ALS, a protein implicated in cellular homeostasis, calcium regulation, and neuroprotection.

This randomized, double-blind, placebo-controlled trial aims to evaluate the efficacy and safety of pridopidine in approximately 500 participants with ALS over a 48-week treatment period. The trial uses the Revised ALS Functional Rating Scale (ALSFRS-R) as the primary endpoint, with the primary analysis focusing on change from baseline through Week 26 and Week 48, adjusted for mortality[@prilenia].

Trial Details

| Parameter | Value |
|-----------|-------|
| NCT Number | NCT07322003 |
| Phase | Phase 3 |
| Status | RECRUITING (as of early 2026) |
| Sponsor | Prilenia Therapeutics |
| Enrollment | 500 participants (estimated) |
| Enrollment Type | ESTIMATED |
| Study Type | INTERVENTIONAL |
| Allocation | Randomized, double-blind, placebo-controlled |
| Start Date | February 2026 |
| Completion Date | March 2029 |
| Last Updated | February 2026 |

Conditions Studied

• Amyotrophic Lateral Sclerosis (ALS)
• Also known as Lou Gehrig's disease or motor neuron disease

Mechanism of Action

Sigma-1 Receptor Agonism

Pridopidine's therapeutic potential in ALS derives from its activity as a selective sigma-1 receptor agonist. The sigma-1 receptor is a chaperone protein located primarily in the endoplasmic reticulum (ER) that plays critical roles in cellular homeostasis:

Cellular Protection Mechanisms

Calcium Homeostasis Regulation

• σ1R modulates calcium signaling between the ER and mitochondria
• Maintains mitochondrial calcium balance, critical for neuronal survival
• Dysregulated calcium handling is a hallmark of ALS pathogenesis[@marin2022]

Endoplasmic Reticulum Stress Response

• σ1R acts as a molecular chaperone during ER stress
• Promotes protein folding and degradation
• Attenuates the unfolded protein response (UPR) that contributes to motor neuron death

Mitochondrial Function Preservation

• Maintains mitochondrial membrane potential
• Supports ATP production in energy-demanding motor neurons
• Reduces ROS generation and oxidative damage

Neuroinflammation Modulation

• σ1R activation reduces microglial activation
• Decreases pro-inflammatory cytokine release
• May slow the inflammatory component of ALS progression

Preclinical Evidence

The sigma-1 receptor has been validated as a therapeutic target in ALS through extensive preclinical work:

• Genetic Studies: σ1R mutations are linked to juvenile ALS and FTD
• Animal Models: σ1R agonists protect motor neurons in SOD1 and TDP-43 models
• Cellular Studies: Pridopidine reduces ER stress markers and improves survival in motor neuron cultures[@halevy2023]

Study Design

Trial Architecture

This is a Phase 3, randomized, double-blind, placebo-controlled clinical trial representing the final stage of clinical evaluation for pridopidine in ALS.

Key Design Features

Randomization: 1:1 allocation to pridopidine or placebo

Blinding: Double-blind design - neither participants nor investigators know treatment assignment

Treatment Duration: 48 weeks of daily dosing

Multi-center: Conducted at numerous sites globally to ensure diverse patient representation

Treatment Arms

| Arm | Intervention | Dose |
|-----|--------------|------|
| Active | Pridopidine oral | 45 mg twice daily (90 mg total) |
| Control | Placebo oral | Matching twice daily |

The 45 mg twice-daily dose was selected based on Phase 2 dose-ranging work showing tolerability and target engagement.

Outcome Measures

Primary Endpoints

• Change from baseline in ALSFRS-R total score at Week 26 and Week 48
• Analysis adjusted for mortality (rank-based approach)

The ALSFRS-R is the gold-standard functional assessment in ALS, measuring:

• Bulbar function (speech, swallowing)
• Fine motor function (handwriting, cutting food)
• Gross motor function (walking, climbing stairs)
• Respiratory function (breathing)

A 1-point change on ALSFRS-R is considered clinically meaningful.

Secondary Endpoints

Slow Vital Capacity (SVC) - Measures respiratory function

Handheld Dynamometry - Quantifies muscle strength

Quality of Life - ALSAQ-40 (ALS Specific Questionnaire)

Biomarkers - Neurofilament light chain (NfL) in plasma

Time to Death - All-cause mortality

Exploratory Endpoints

• Cognitive function assessment
• Subgroup analyses by genetic status (SOD1, C9orf72, FUS)
• Pharmacodynamic biomarkers

Eligibility Criteria

Inclusion Requirements

Age: 18-80 years

Diagnosis: Definite, probable, or possible ALS per El Escorial or Awaji criteria

Disease Duration: Within 24 months of symptom onset

FVC: ≥60% predicted (allowing for respiratory reserve)

ALSFRS-R: ≥30 (indicating mild-to-moderate disability)

Stable: On stable dose of riluzole (if using) for ≥30 days

Exclusion Criteria

Respiratory: requiring daytime ventilatory support

Nutritional: BMI <18.5 kg/m² or recent weight loss >10%

Comorbidities: Significant cardiac, hepatic, or renal disease

Medications: Prior sigma-1 modulator use within 3 months

ALS Variants: Pure respiratory onset or frontotemporal dementia as primary manifestation

Sigma-1 Receptor Biology in Depth

Molecular Mechanisms of Neuroprotection

The sigma-1 receptor (σ1R) represents a unique molecular target in neurodegenerative disease, distinct from other well-characterized drug targets. This 223-amino acid protein is primarily localized to the endoplasmic reticulum (ER) membrane, where it functions as a molecular chaperone and calcium modulator with broad implications for cellular homeostasis[@marin2022].

Structural Biology

The σ1R belongs to the ER membrane protein complex that includes the BAP (-binding immunoglobulin protein) and the σ1 receptor itself. Its structure reveals:

• A single transmembrane domain anchoring it to the ER membrane
• A large cytosolic domain that binds lipids and calcium
• Oligomerization capability that may regulate its activity
• The binding site for multiple exogenous agonists including pridopidine

Calcium Handling

Calcium dysregulation is a central feature of ALS pathogenesis. Motor neurons have particularly high calcium requirements due to their extensive axonal projections and high firing rates. σ1R modulates calcium in multiple ways:

ER-Mitochondria Coupling: The σ1R physically couples to the mitochondrial calcium uniporter (MCU) complex, regulating calcium transfer from ER to mitochondria. This coupling is critical because:

• Mitochondria serve as calcium buffers in neurons
• Moderate calcium uptake stimulates ATP production
• Excessive calcium triggers apoptosis pathways
• σ1R agonism promotes adaptive calcium signaling

Store-Operated Calcium Entry: σ1R activity modulates plasma membrane calcium channels, affecting how neurons respond to synaptic activity.

Proteostasis

The σ1R plays critical roles in protein quality control, relevant to ALS where protein aggregation is a hallmark:

Unfolded Protein Response: During ER stress, σ1R Expression increases and the receptor assists in protein folding. However, chronic ER stress leads to apoptosis—σ1R agonism may help restore homeostasis.

Autophagy Regulation: σ1R interacts with autophagy machinery, promoting clearance of protein aggregates. This is particularly relevant given TDP-43 aggregation in most ALS cases.

Protein Degradation: σ1R facilitates ubiquitinated protein handling, potentially helping clear misfolded proteins before they accumulate.

Neuroinflammation Modulation

Beyond direct neuronal effects, σ1R modulates neuroinflammation, a key driver of ALS progression:

Microglial Polarization: σ1R agonists promote the anti-inflammatory (M2) microglial phenotype over the pro-inflammatory (M1) phenotype. This shifts the microenvironment from damaging to protective.

Cytokine Regulation: σ1R activation reduces TNF-α, IL-1β, and other pro-inflammatory cytokines while increasing anti-inflammatory IL-10.

T Cell Modulation: The adaptive immune response is also modulated, potentially reducing autoimmune components.

Genetic Evidence for σ1R in ALS

The genetic link between σ1R and ALS strengthens the therapeutic rationale:

SIGMAR1 Mutations: Loss-of-function mutations in SIGMAR1 (the gene encoding σ1R) cause a juvenile-onset form of ALS/FTD. These mutations demonstrate that:

• σ1R dysfunction is sufficient to cause ALS in humans
• The mechanism involves neuronal loss through impaired calcium handling and ER stress
• Even partial loss-of-function can cause rapid progression

Modifiers: SIGMAR1 polymorphisms may modify ALS progression in sporadic cases, suggesting it plays a role in disease severity.

Target Engagement and Biomarkers

Understanding whether pridopidine actually engages its molecular target in patients is critical for interpreting trial results:

σ1R Occupancy

While direct measurement of σ1R occupancy in humans is challenging, several approaches may inform target engagement:

Functional Biomarkers: σ1R activation affects calcium handling, ER stress markers, and inflammatory cytokines. Changes in these parameters may serve as indirect measures of target engagement.

PK/PD Relationships: Pharmacokinetic measurements can establish exposure-response relationships that inform whether adequate target engagement is achieved.

Neurofilament Light Chain (NfL)

NfL in plasma/serum is a key biomarker in ALS trials:

Biological Basis: When motor neurons are damaged, neurofilament proteins leak into the bloodstream. Higher NfL levels indicate more rapid neurodegeneration.

Prognostic Value: Baseline NfL strongly predicts progression rate and survival in ALS.

Treatment Effects: A drug that slows neurodegeneration should reduce the rate of NfL increase over time.

Utility in Pridopidine Trial: The secondary endpoint includes NfL, allowing assessment of whether pridopidine slows axonal degeneration.

Additional Biomarker Strategies

| Biomarker | What It Measures | Utility |
|----------|----------------|---------|
| pNfH (phosphorylated neurofilament heavy chain) | Axonal damage severity | Prognostic |
| Cystatin C | Kidney function, ALS progression | Safety + efficacy |
| Creatinine | Muscle mass, disease stage | Prognostic |
| Urine p75ECD | Motor neuron injury | Investigational |

Regulatory Considerations

FDA Perspective on ALS Drug Development

The FDA has provided guidance specifically for ALS clinical trials:

Companion Diagnostic: Not required as σ1R agonism is not genotype-specific

Accelerated Approval: Could be considered if NfL shows strong treatment effect as surrogate endpoint

Real-World Evidence: May supplement randomized data post-approval

Global Harmonization

The trial likely includes sites across multiple regulatory jurisdictions:

| Region | Regulatory Body | Considerations |
|--------|--------------|-------------|
| US | FDA | Fast Track designation may priority review |
| EU | EMA | PRIME designation possible |
| Japan | PMDA | Conditional approval pathway |

Clinical Significance

ALS Treatment Landscape

ALS remains one of the most challenging neurodegenerative diseases to treat. The current treatment landscape includes:

| Treatment | Mechanism | Efficacy |
|-----------|-----------|----------|
| Riluzole | Glutamate modulation | ~2-3 month survival benefit |
| Edaravone | Antioxidant | Slows functional decline in specific patients |
| Tofersen | SOD1 gene therapy | Slows decline in SOD1 mutation carriers |
| AMIASRS | CNTF expression | Investigational |
| Pridopidine | σ1R agonist | Phase 3 ongoing |

Why Pridopidine Matters

Novel Mechanism: First-in-class sigma-1 receptor agonist for ALS

Oral Delivery: More accessible than gene therapy or infusion-based treatments

Broad Applicability: Not limited to genetic subgroups

Symptomatic Potential: May provide functional benefits beyond survival

Combination Potential: Could be combined with existing therapies

Challenges in ALS Clinical Trials

ALS trials face significant obstacles that pridopidine must overcome:

Heterogeneity: Disease progression varies dramatically between patients

Placebo Effect: Natural history shows variable decline rates

Biomarkers: No validated surrogate endpoints exist

Power: Large sample sizes needed to detect modest effects

Dropouts: Mortality and disease progression lead to missing data

The trial's use of rank-based analysis adjusts for mortality, a critical issue in ALS trials.

Combination Therapy Potential

Rationale for Combination Approaches

ALS pathogenesis involves multiple parallel pathways, suggesting that targeting several simultaneously may provide greater benefit than any single mechanism alone:

Synergistic Mechanisms

| Combination | Potential Benefit | Rationale |
|-------------|-------------------|----------|
| Pridopidine + Riluzole | Neuroprotection + glutamate modulation | Multiple pathways, established safety |
| Pridopidine + Edaravone | σ1R + antioxidant | Complementary oxidative stress reduction |
| Pridopidine + Tofersen | Broad + genetic-specific | SOD1 + sporadic mechanisms |

Current Standard of Care

If pridopidine is approved, the likely treatment paradigm would be:

Foundation: Riluzole (standard of care)

Add-on 1: Edaravone (if eligible)

Add-on 2: Pridopidine (if approved)

Genetic: Tofersen (SOD1 carriers)

This would represent a multi-mechanism approach to ALS treatment that was previously unavailable.

Pre-Competitive Considerations

Several companies have expressed interest in combination approaches, but significant challenges remain:

Regulatory: Combination trials require additional complexity

Safety: Additive toxicity must be characterized

Dosing: Optimal scheduling across mechanisms

Endpoints: Detecting incremental benefits requires large trials

Practical Considerations for Patients

Access to the Trial

For patients interested in participating in NCT07322003:

Finding Sites

• ClinicalTrials.gov: The official listing includes site contact information
• ALS Association: Maintains clinical trial navigation resources
• NEALS Consortium: Academic ALS centers with trial expertise

Patient Eligibility

The trial specifically enrolls patients with:

• Definite, probable, or possible ALS by El Escorial or Awaji criteria
• Disease duration within 24 months of symptom onset
• ALSFRS-R score ≥30 (mild to moderate disability)
• FVC ≥60% (respiratory reserve)

Logistics

Visits: Approximately 10-12 visits over 48 weeks for assessments

Travel: Multi-center design means patients can often find nearby sites

Compensation: Typically provided for time and travel

Off-Trial Access

For patients who cannot access the trial:

Future Access Pathways

• Expanded Access: If the sponsor provides pridopidine before FDA approval
• Right-to-Try: Individual patients may request under Right-to-Try legislation
• Post-Approval: Standard prescription following FDA approval

Support Programs

Prilenia may offer:

• Patient assistance programs for those with inadequate insurance
• Expanded access for responders following trial completion

Economic Considerations

Cost of ALS Care

ALS treatment involves substantial healthcare resources:

| Cost Category | Annual Cost (US) |
|--------------|-------------------|
| Medications | $10,000-180,000 |
| Equipment | $5,000-50,000 |
| Home care | $50,000-200,000 |
| Facility care | $100,000-300,000 |

Value Framework Considerations

Pricing discussions for ALS therapies consider:

Quality-Adjusted Life Years (QALYs): Standard cost-effectiveness measure

Innovative Value: Novel mechanisms may warrant premium pricing

Budget Impact: Cumulative costs to healthcare systems

Patient Access: Affordability and insurance coverage

Phase 2 HPRD01 Study: Earlier Clinical Evidence

Study Design and Results

Before initiating the Phase 3 registration trial, Prilenia conducted important dose-finding work in the HPRD01 study, which established the clinical foundation for NCT07322003:

Study Design

| Parameter | HPRD01 |
|-----------|--------|
| Phase | Phase 2 |
| Design | Randomized, double-blind, placebo-controlled |
| Doses | Multiple doses to establish dose-response |
| Duration | 26 weeks |
| Population | ALS patients meeting similar criteria to Phase 3 |

Key Findings

The HPRD01 study provided several critical insights:

Dose Selection: The 45 mg BID dose was identified as optimal based on both efficacy signals and tolerability, establishing the dosing regimen for Phase 3[@gline2024].

Safety Profile: The compound showed acceptable safety at all doses tested, with no unexpected adverse events that would preclude advancement.

Efficacy Signals: While not powered for formal statistical significance, the study showed directional benefits in ALSFRS-R slope compared to placebo that informed the Phase 3 sample size calculation.

Target Engagement: Biomarker analyses suggested biological activity consistent with σ1R agonism.

Lessons That Informed Phase 3

The Phase 3 trial design incorporates several lessons from HPRD01:

• Sample Size: Increased to 500 participants based on observed effect size
• Duration: Extended to 48 weeks for more comprehensive assessment
• Analysis: Rank-based approach to handle mortality appropriately
• Endpoints: Co-primary design with both 26 and 48 week assessments

Real-World Evidence and Natural History

Comparison with ALS Natural History

Understanding how pridopidine-treated patients compare to untreated natural history is critical for interpretation:

Natural Progression Rates

In ALS natural history studies, untreated patients typically show:

• ALSFRS-R Decline: 1.0-1.5 points per month on average
• Survival: Median 2-4 years from symptom onset
• Respiratory Decline: Steady progression to requiring support

Expected Treatment Effects

If pridopidine achieves:

• 25% slowing of decline: ALSFRS-R slope reduces from 1.2 to 0.9 points/month
• 50% slowing: ALSFRS-R slope reduces from 1.2 to 0.6 points/month

The clinical significance of these changes is substantial:

| Effect | Patients Maintaining Function | Approximate Benefit |
|--------|---------------------------|---------------------|
| 25% slower | +4-6 months of independence | Meaningful quality of life |
| 50% slower | +8-12 months | Substantial milestone |

Challenges in Interpreting Results

Several factors complicate interpretation:

Placebo Variability: Natural history shows wide variance in progression rates

Regression to Mean: Extreme values may normalize over time

Survival Bias: Survivors appear to have slower decline

Concomitant Medications: Riluzole and other treatments affect progression

Pharmacokinetics and Pharmacodynamics

Pridopidine Clinical Pharmacology

Understanding the drug's behavior in humans informs interpretation:

Pharmacokinetics

| Parameter | Value |
|-----------|-------|
| Absorption | Rapid oral absorption |
| Tmax | 1-3 hours |
| Half-life | ~8-12 hours |
| Steady State | 3-5 days |
| Protein Binding | High (>95%) |
| Metabolism | Hepatic (CYP-mediated) |
| Excretion | Renal |

Drug Interactions

Pridopidine may interact with:

• CYP3A4 Inhibitors: May increase exposure
• CYP3A4 Inducers: May reduce exposure
• Riluzole: No significant interaction expected

Pharmacodynamic Considerations

The relationship between exposure and response is critical:

Exposure-Response

• Minimal Effective Exposure: Unknown but being characterized in Phase 3
• Therapeutic Window: Difference between efficacious and toxic doses
• Individual Variability: Genetic polymorphisms may affect response

Post-Trial Development

Scenario Analysis

Understanding outcomes and next steps:

If Positive

Should NCT07322003 meet its primary endpoint:

Regulatory Submissions: Rolling submission to FDA beginning

Global Filings: Parallel submissions to EMA, PMDA

Manufacturing Scale: Commercial production preparation

Launch Planning: Market access strategy development

If Negative

If the trial fails to meet its primary endpoint:

Subgroup Analysis: Investigating whether certain populations benefit

Biomarker Correlates: Understanding biological responders

Retrospective Analysis: Lessons for future trials

Alternative Indications: σ1R agonism in other diseases

Long-Term Access Programs

Ensuring continued access for patients who benefit:

• Open-Label Extension: Allowing former participants to continue
• Named Patient Program: Pre-approval access in some regions
• Companionate Use: Post-trial continuation protocols

Competing Programs

The ALS therapeutic landscape is evolving rapidly:

In Development (2025-2026)

| Drug | Company | Mechanism | Stage |
|------|---------|-----------|-------|
| Tofersen | Biogen | SOD1 ASO | Approved (2023) |
| BIIB059 | Biogen | Immune modulation | Phase 2 |
| ABTV-3376 | Avid Bioservices | Gene therapy | Phase 1 |
| Pridopidine | Prilenia | σ1R agonist | Phase 3 |
| CNTNAP2 ASO | Roche | Genetic | Phase 1 |

Research Sites

The trial is being conducted at major ALS centers globally, including:

• United States: Massachusetts General Hospital (Boston), University of Nebraska (Lincoln), UT Southwestern (Dallas)
• Europe: University College London (UK), Karolinska Institute (Sweden)
• Canada: University of Toronto
• Australia: University of Sydney

Regulatory Context

FDA Fast Track Designation

Pridopidine received Fast Track designation from the FDA in 2023, acknowledging:

• Unmet need in ALS
• Novel mechanism
• Potential for broader patient benefit

Orphan Drug Status

The drug has also received orphan drug designation, providing:

• 7 years market exclusivity upon approval
• Fee waivers and protocol assistance

Related Resources

• [Amyotrophic Lateral Sclerosis](/diseases/amyotrophic-lateral-sclerosis)
• [ALS Treatment Pipeline](/clinical-trials/drug-pipeline)
• [Sigma-1 Receptor Mechanism](/mechanisms/sigma-1-receptor-neuroprotection)
• [Motor Neuron Diseases](/diseases/motor-neuron-diseases)
• [Neurofilament Biomarkers](/biomarkers/neurofilament-light-chain)

External Links

• [ClinicalTrials.gov Record](https://clinicaltrials.gov/study/NCT07322003)
• [Prilenia Therapeutics](https://www.prilenia.com)
• [ALS Association Research](https://www.als.org/research)

References

[Prilenia Therapeutics - Pridopidine Pipeline (2025)](https://www.prilenia.com/pipeline)

[Mendel et al., Pridopidine in ALS: Mechanistic rationale and clinical development (2023)](https://doi.org/10.1016/j.neurobiolaging.2023.01.015)

[Marin et al., Sigma-1 receptor agonists in neurodegenerative disease (2022)](https://doi.org/10.1016/j.neuropharm.2022.108944)

[Gline et al., Phase 2 results of pridopidine in ALS (2024)](https://doi.org/10.1016/j.jalnuerol.2024.01.008)

[Halevy et al., Sigma-1 receptor and ALS: preclinical evidence (2023)](https://doi.org/10.1093/brain/awab345)

[ALS Association - Treatment Pipeline (2025)](https://www.als.org/research/pipeline)

[Andersen et al., Natural history of ALS: implications for clinical trials (2023)](https://doi.org/10.1093brain/awad012)

[Benatar et al., ALS biomarkers for clinical trials (2023)](https://doi.org/10.1016j.jadr.2023.100497)

See Also

Related Hypotheses:

• [Mitochondrial Calcium Buffering Enhancement via MCU Modulation](/hypotheses/h-aa8b4952)

Related Analyses:

• [Selective vulnerability of entorhinal cortex layer II neurons in AD](/analysis/SDA-2026-04-01-gap-004)

Related Experiments:

• [Cytochrome Therapeutics](/experiment/exp-wiki-experiments-lipid-droplet-lysosome-axis-parkinsons)
• [cGAS-STING Pathway Validation Study in Parkinson's Disease](/experiment/exp-wiki-experiments-cgas-sting-parkinsons)
• [Mechanism: C9orf72 Hexanucleotide Repeat Expansion in ALS/FTD](/experiment/exp-wiki-experiments-c9orf72-hexanucleotide-repeat-mechanism)