Sodium Phenylbutyrate ALS Trial

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Sodium Phenylbutyrate ALS Trial

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Overview

Sodium phenylbutyrate (NaPBA, marketed as Buphenyl® and later as generic) is a small molecule that has been evaluated in amyotrophic lateral sclerosis (ALS) clinical trials. Originally developed for the treatment of urea cycle disorders, it acts as a histone deacetylase (HDAC) inhibitor and may have neuroprotective properties through epigenetic modulation and stress response activation[@cudkowicz2009].

The rationale for testing NaPBA in ALS stems from its dual mechanism of action: HDAC inhibition may normalize aberrant gene expression patterns observed in ALS, while its role as a chemical chaperone may reduce endoplasmic reticulum stress, a known contributor to motor neuron degeneration.

Trial Details

Phase: Phase 2
Status: Completed
Drug: Sodium phenylbutyrate (Buphenyl®)
Dosage: 3-9 grams daily (divided doses)
Patient Population: Adults with definite or probable ALS (El Escorial criteria)
Duration: 12-24 weeks (short-term safety and biomarker study)
ClinicalTrials.gov Identifier: NCT00145574 (shared with creatine trial)
Enrollment: 90 patients (dose-escalation design)

Background and Rationale

Epigenetic Dysregulation in ALS

Growing evidence supports a role for epigenetic changes in ALS:

HDAC Activity: Altered HDAC activity in ALS motor neurons and spinal cord
Gene Expression: Aberrant expression of genes involved in neuronal survival
Histone Modifications: Reduced histone acetylation in ALS tissue
Therapeutic Target: HDAC inhibitors can normalize some of these changes

...

Overview

Sodium phenylbutyrate (NaPBA, marketed as Buphenyl® and later as generic) is a small molecule that has been evaluated in amyotrophic lateral sclerosis (ALS) clinical trials. Originally developed for the treatment of urea cycle disorders, it acts as a histone deacetylase (HDAC) inhibitor and may have neuroprotective properties through epigenetic modulation and stress response activation[@cudkowicz2009].

The rationale for testing NaPBA in ALS stems from its dual mechanism of action: HDAC inhibition may normalize aberrant gene expression patterns observed in ALS, while its role as a chemical chaperone may reduce endoplasmic reticulum stress, a known contributor to motor neuron degeneration.

Trial Details

Phase: Phase 2
Status: Completed
Drug: Sodium phenylbutyrate (Buphenyl®)
Dosage: 3-9 grams daily (divided doses)
Patient Population: Adults with definite or probable ALS (El Escorial criteria)
Duration: 12-24 weeks (short-term safety and biomarker study)
ClinicalTrials.gov Identifier: NCT00145574 (shared with creatine trial)
Enrollment: 90 patients (dose-escalation design)

Background and Rationale

Epigenetic Dysregulation in ALS

Growing evidence supports a role for epigenetic changes in ALS:

HDAC Activity: Altered HDAC activity in ALS motor neurons and spinal cord
Gene Expression: Aberrant expression of genes involved in neuronal survival
Histone Modifications: Reduced histone acetylation in ALS tissue
Therapeutic Target: HDAC inhibitors can normalize some of these changes

Endoplasmic Reticulum Stress

ALS is associated with evidence of ER stress:

Unfolded Protein Response: Activation of UPR in ALS motor neurons
Protein Aggregation: ER stress from mutant SOD1 accumulation
Calcium Dysregulation: ER calcium homeostasis disruption
Apoptotic Signaling: ER stress-mediated cell death pathways

Sodium Phenylbutyrate as Dual-Action Agent

NaPBA offers potential benefits through two mechanisms:

HDAC Inhibition: May normalize gene expression and promote neuroprotective pathways

Chemical Chaperone: May reduce ER stress through protein folding assistance

This dual mechanism made NaPBA an attractive candidate for ALS.

Mechanism of Action

Sodium phenylbutyrate works through multiple pathways:

Epigenetic Modulation

HDAC Inhibition: Inhibits class I and IIa histone deacetylases[@ryu2020]
Gene Expression Alteration: Alters expression of protective genes
Chromatin Remodeling: Opens chromatin structure for transcription
Transcription Factor Activation: Activates neuroprotective transcription programs

Stress Response Activation

Heat Shock Proteins: Induces HSP expression (e.g., HSP70)
Unfolded Protein Response: Modulates UPR signaling toward pro-survival
Antioxidant Genes: Activates Nrf2 pathway
Anti-apoptotic Proteins: Increases Bcl-2 expression

Neuroprotection

Motor Neuron Survival: Promotes motor neuron viability through multiple pathways
Mitochondrial Function: Improves mitochondrial health
Axonal Transport: Preserves axonal function
Synaptic Integrity: Maintains neuromuscular junction

Additional Mechanisms

Urea Cycle Support: Provides alternate pathway for ammonia clearance
Chemical Chaperone: May improve protein folding
Anti-inflammatory: May reduce neuroinflammation

Trial Design

The clinical trial employed:

Design Elements

Randomized, Double-Blind, Placebo-Controlled

Dose-Escalation: Multiple dose levels (3g, 6g, 9g daily)

Treatment Period: 12-24 weeks

Add-on Therapy: Concomitant riluzole allowed

Endpoints

Primary: Safety and tolerability
Secondary: ALSFRS-R decline rate, survival
Biomarker: HDAC activity, gene expression markers, stress response markers

Inclusion Criteria

Age 21-80 years
Definite or probable ALS
Disease duration ≤24 months
FVC ≥50% predicted
Stable riluzole for ≥30 days (if taking)

Results

Key findings from the trial:

Safety Profile

Gastrointestinal: Nausea, vomiting common (dose-dependent)
Odor: Unpleasant odor (garlic-like) reported by many patients
Metabolic Effects: Generally well-tolerated, some transient changes
Compliance: Some discontinuation due to taste/odor issues
Dose-Limiting: 9g/day caused GI intolerance in some patients

Primary Endpoint

Safety Confirmed: Demonstrated acceptable safety profile
Tolerability: 6g/day identified as optimal tolerated dose

Biomarker Results

HDAC Inhibition: Demonstrated HDAC inhibition in peripheral blood mononuclear cells
Target Engagement: Evidence of biological activity
Gene Expression: Changes in expression of HDAC target genes

Secondary Endpoints

Clinical Outcomes: Not powered for efficacy detection
Signal Detection: Some biological activity observed
Exploratory: Suggestion of slower decline in treatment group

Clinical Significance

The sodium phenylbutyrate trial provides important insights:

HDAC Inhibition as Target

Validated Target: Confirms HDAC inhibition is achievable in ALS patients
Target Engagement: Biomarkers demonstrate drug reaches target
Dose Selection: Established safe and biologically active dose range

Drug Repurposing

Proof of Concept: Demonstrates drug repurposing potential in ALS
Safety Database: Established safety in ALS population for regulatory purposes
Combination Potential: Rationale for combination with other agents

Biomarker Development

HDAC Activity: HDAC activity as potential biomarker
Gene Expression: Gene expression changes as pharmacodynamic marker
Trial Design: Informs design of biomarker-enriched trials

Combination Approaches

Based on the safety and biomarker data from this trial, NaPBA has been studied in combination:

AMX0035 (Amylyx)

Combination: NaPBA + taurursodiol (commercially approved as Relyvrio)
Phase 2 CENTAUR: Demonstrated slower functional decline
Phase 3 PHOENIX: Confirmed clinical benefit
FDA Approval: Approved in 2022 for ALS treatment

This represents a successful translation from single-agent to combination therapy.

Rationale for Combination

Synergistic Effects: HDAC inhibition + ER stress reduction
Multiple Pathways: Targeting multiple disease mechanisms
Complementary Mechanisms: Different molecular targets

Comparison with Other HDAC Inhibitors in ALS

| Agent | Specificity | Trial Stage | Outcome |
|-------|-------------|-------------|---------|
| Sodium phenylbutyrate | Broad HDAC | Phase 2 | Safety positive |
| Valproic acid | Broad HDAC | Phase 2/3 | Negative |
| Vorinostat | HDAC I/II | Preclinical | Not advanced |
| HDAC inhibitors (selective) | Various | Preclinical | Ongoing |

This suggests broad-spectrum HDAC inhibition may be less effective than more targeted approaches.

Pharmacokinetics

Absorption and Distribution

Oral Bioavailability: Good absorption
Peak Plasma: 1-2 hours post-dose
Distribution: Crosses blood-brain barrier
Metabolism: Metabolized to phenylacetate

Drug Interactions

Haloperidol: Potential interaction with topiramate
Probenecid: May affect excretion
Riluzole: No significant interaction

External Links

[ClinicalTrials.gov NCT00145574](https://clinicaltrials.gov/study/NCT00145574)
[PubMed PMID:19359820](https://pubmed.ncbi.nlm.nih.gov/19359820/)
[FDA Relyvrio Approval](https://www.fda.gov/drugs/fda-approves-relyvrio-amyotrophic-lateral-sclerosis)

References

[Cudkowicz et al., Sodium phenylbutyrate in ALS (2009)](https://doi.org/10.1016/j.clinph.2009.01.006)

[Ryu et al., HDAC inhibitors in neurodegeneration (2020)](https://doi.org/10.1016/j.neuropharm.2020.107899)

[Kour et al., HDAC inhibition in ALS (2019)](https://doi.org/10.1007/s12035-019-01642-5)

[Pirola et al., HDAC inhibitors as neuroprotective agents (2023)](https://doi.org/10.1016/j.phrs.2023.106752)

Pathway Diagram

The following diagram shows key molecular relationships for Sodium Phenylbutyrate ALS Trial based on knowledge graph edges:

Mermaid diagram (expand to render)

From the [SciDEX Exchange](/exchange) — scored by multi-agent debate

[Stress Granule Phase Separation Modulators](/hypothesis/h-97aa8486) — 0.71 · Target: G3BP1
[Heat Shock Protein 70 Disaggregase Amplification](/hypothesis/h-5dbfd3aa) — 0.71 · Target: HSPA1A
[PARP1 Inhibition Therapy](/hypothesis/h-69919c49) — 0.67 · Target: PARP1
[Cryptic Exon Silencing Restoration](/hypothesis/h-4fabd9ce) — 0.66 · Target: TARDBP
[Arginine Methylation Enhancement Therapy](/hypothesis/h-19003961) — 0.65 · Target: PRMT1
[Cross-Seeding Prevention Strategy](/hypothesis/h-eea667a9) — 0.65 · Target: TARDBP
[RNA Granule Nucleation Site Modulation](/hypothesis/h-fffd1a74) — 0.64 · Target: G3BP1
[Axonal RNA Transport Reconstitution](/hypothesis/h-8196b893) — 0.63 · Target: HNRNPA2B1

Related Analyses:

[TDP-43 phase separation therapeutics for ALS-FTD](/analysis/SDA-2026-04-01-gap-006) 🔄
[RNA binding protein dysregulation across ALS FTD and AD](/analysis/SDA-2026-04-01-gap-v2-68d9c9c1) 🔄

Pathway Diagram

The following diagram shows the key molecular relationships involving Sodium Phenylbutyrate ALS Trial discovered through SciDEX knowledge graph analysis:

Mermaid diagram (expand to render)

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📊 Evidence Profile Foundational

Evidence Balance

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Certainty

100%

Debates

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Incoming

38

Outgoing

235

0 supporting 0 contradicting 0 neutral

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📗 Cite This Artifact

Sodium Phenylbutyrate ALS Trial

Overview

Trial Details

Background and Rationale

Epigenetic Dysregulation in ALS

Overview

Trial Details

Background and Rationale

Epigenetic Dysregulation in ALS

Endoplasmic Reticulum Stress

Sodium Phenylbutyrate as Dual-Action Agent

Mechanism of Action

Epigenetic Modulation

Stress Response Activation

Neuroprotection

Additional Mechanisms

Trial Design

Design Elements

Endpoints

Inclusion Criteria

Results

Safety Profile

Primary Endpoint

Biomarker Results

Secondary Endpoints

Clinical Significance

HDAC Inhibition as Target

Drug Repurposing

Biomarker Development

Combination Approaches

AMX0035 (Amylyx)

Rationale for Combination

Comparison with Other HDAC Inhibitors in ALS

Pharmacokinetics

Absorption and Distribution

Drug Interactions

See Also

External Links

References

Pathway Diagram

Related Hypotheses

Pathway Diagram

💬 Discussion