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Semax

Semax is a synthetic heptapeptide derived from the N-terminal fragment of adrenocorticotropic hormone (ACTH 4-10), specifically engineered for neuroprotective and cognitive enhancement applications. Developed through systematic peptide modification research in Russia, Semax (Met-Glu-His-Phe-Pro-Gly-Pro) represents a breakthrough in rational peptide design, optimized to enhance cognitive function while providing robust protection against neurological injury without the hormonal side effects of native ACTH.

This peptide has gained considerable attention in neurology and cognitive medicine due to its demonstrated multifaceted benefits in stroke recovery, traumatic brain injury rehabilitation, and cognitive performance optimization through comprehensive modulation of neurotransmitter systems, gene expression regulation, and neuroprotective pathways. Semax exhibits excellent CNS penetration via intranasal administration and maintains bioactivity across various physiological conditions, making it unique among neuroprotective peptides.

Molecular structure diagram of Semax, showing chemical bonds and atoms including nitrogen, oxygen, and carbon atoms.

Overview

Semax demonstrates superior stability compared to native ACTH fragments through strategic amino acid modifications that resist enzymatic degradation. The peptide exhibits excellent water solubility and high intranasal bioavailability with rapid CNS penetration. It is metabolized primarily through peptidase activity and eliminated via renal excretion, with detectability in plasma for several hours post-administration.

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Chemical structure & Properties

  • Molecular Formula: C37H51N9O10S
  • Molecular Weight: 813.93 Da
  • Sequence: Met-Glu-His-Phe-Pro-Gly-Pro (ACTH 4-10 analog)
  • Half-life: Approximately 1-2 hours (plasma elimination)
  • Stability: Enhanced resistance to peptidase degradation through structural modifications

Mechanism of Action

Semax exerts its therapeutic effects through multiple interconnected neurobiological pathways:

Neurotransmitter System Modulation

Semax influences key neurotransmitter systems through:

  • Enhanced dopaminergic signaling improving motivation, executive function, and reward processing
  • Serotonergic system modulation supporting mood regulation and stress resilience
  • Cholinergic system enhancement promoting memory formation, attention, and learning capacity
  • GABA system balance contributing to anxiety reduction and cognitive clarity

MELANOCORTIN SIGNALING

  • Semax is an ACTH(4–10) analogue whose proposed mechanisms include effects on melanocortin signaling in the brain.

Gene Expression Regulation and Transcriptional Control

The peptide demonstrates remarkable ability to modulate gene expression:

  • Upregulation of neuroprotective genes including brain-derived neurotrophic factor (BDNF)
  • Enhanced expression of genes involved in neuronal survival and synaptic repair
  • Modulation of inflammatory response genes reducing neuroinflammation and secondary injury
  • Activation of genes supporting neuroplasticity, neurogenesis, and synaptic strengthening

Cerebrovascular Protection and Enhancement

Semax provides comprehensive cerebrovascular benefits through:

  • Enhanced endothelial function and blood-brain barrier integrity
  • Improved cerebral blood flow and oxygen delivery to neural tissues
  • Protection against ischemia-reperfusion injury and oxidative damage
  • Promotion of angiogenesis and collateral circulation in damaged brain regions

Anti-inflammatory and Antioxidant Mechanisms

The peptide demonstrates potent protective properties through:

  • Reduction of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) and inflammatory mediators
  • Enhanced antioxidant enzyme activity and cellular protection systems
  • Mitochondrial protection and improved cellular energy metabolism
  • Reduction of oxidative stress markers and prevention of cellular damage

Areas Investigated in

the Research Literature

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Current Clinical Evidence

Safety Profile and Considerations

Preclinical and Clinical Safety Data

Studies across multiple species and limited human applications demonstrate:

  • Generally well tolerated in limited clinical use.
  • Large modern safety trials and long-term safety data are limited.
  • Tolerability reported in limited short-term use; large modern safety trials have not been conducted
  • Tolerance and dependence potential have not been systematically studied

Reported Side Effects

Mild and Transient Effects:

  • Rare mild headache during initial treatment period
  • Occasional nasal irritation with intranasal administration
  • Transient taste alterations (uncommon with intranasal route)
  • Minor injection site reactions with subcutaneous administration

Potential Concerns

Individual Sensitivity Variations:

  • Some patients may experience heightened cognitive stimulation requiring dose adjustment
  • Potential for overstimulation in sensitive individuals at higher doses
  • Individual variation in dosing and response patterns
  • Need for individualized treatment protocols based on patient response

Administration Route Considerations:

  • Intranasal administration may cause minor local irritation in some patients
  • Proper administration technique essential for optimal bioavailability
  • Quality and purity of preparations may vary between sources

Contraindications

Semax should be avoided in:

  • Active psychotic disorders or severe psychiatric instability (without medical supervision)
  • Pregnancy and breastfeeding (insufficient safety data in these populations)
  • Known hypersensitivity to peptides or components of the formulation
  • Severe cardiovascular instability requiring intensive monitoring

Regulatory Status and Legal Considerations

Regulatory information current as of 28 August 2026. This is a summary, not legal or medical advice, and status can change.

FDA Status

  • Classification: Research peptide/investigational compound in most jurisdictions. Semax (heptapeptide) was previously nominated to FDA Category 2; the nomination was withdrawn as of April 22, 2026. On July 24, 2026, the FDA Pharmacy Compounding Advisory Committee recommended Semax-related bulk drug substances for consideration on the 503A Bulks List. The recommendation is advisory and non-binding; final FDA action remains pending. Semax remains unapproved for therapeutic use in the United States.
  • Approval Status: Not approved for human therapeutic use in the United States or EU
  • Russian Federation: Approved for clinical use in specific neurological applications
  • Regulatory Position: Limited regulatory oversight outside of Russia

Legal Availability

  • Commercial Status: Available as research chemical through specialized suppliers
  • Market Presence: Sold for research purposes without therapeutic claims
  • Quality Control: Variable quality and purity standards across different suppliers
  • Clinical Use: Limited to research settings and specialized medical practices

Research Applications

  • Academic Research: Widely used in neuroscience research protocols
  • Clinical Investigation: Ongoing studies in various neurological applications
  • International Interest: Growing research interest in neuroprotective applications
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Conclusion

What the evidence supports

Semax is an ACTH-derived peptide studied for nootropic and neuroprotective effects, primarily in Russian clinical research and preclinical models. That work has not been replicated in independent controlled trials, and there is no standardized dosing or long-term safety data outside those settings. Semax is not FDA approved in the United States; a July 2026 Pharmacy Compounding Advisory Committee recommendation to consider related bulk substances for the 503A list is advisory, non-binding and pending. This page summarizes the published research and nothing further.

SEMAX SCIENTIFIC

DATA SUMMARY

MOLECULAR CHARACTERISTICS
RESEARCH APPLICATIONS SUMMARY
CLINICAL EVIDENCE SUMMARY
SAFETY PROFILE
REGULATORY STATUS
Parameter
Molecular Weight
Amino Acid Length
Half-Life
Bioavailability
Detection Window
Value
813.93 Da
7 residues
~1-2 hours (plasma)
High intranasal, excellent CNS penetration
Up to 6 hours (plasma)
Application
Stroke Recovery
Cognitive Enhancement
Neuroprotection
TBI Recovery
Reported outcome (model)
Preclinical evidence of potential neurological recovery effects and reduced infarct size
Improved memory, attention, learning capacity
Large-scale gene expression changes, improved survival in the model
Preclinical evidence of potential effects on recovery and cognitive deficits
Study Type
Genomic Analysis
Neurodevelopmental Study
Neuroprotection Research
Population
Stroke models
ADHD/Rett theoretical
Ischemia-reperfusion models
Results
Large-scale gene expression changes
Strong mechanistic rationale
Comprehensive transcriptomic changes
Limitations
Preclinical data, translation needed
Theoretical framework only
Animal studies, human data limited
Parameter
Acute Toxicity
Organ Toxicity
Adverse Events
Long-term Safety
Finding
Well tolerated short-term; long-term data limited
No organ toxicity reported in the limited data available
Minimal: mild headache, nasal irritation
Well-tolerated, no tolerance development
Authority
FDA
WADA Status
Russian Federation
Classification
Research Compound
Non-approved substance
Approved Medication
Status
Not approved for human therapeutic use
Not named on the Prohibited List, but S0 (Non-Approved Substances) applies — treat as prohibited and verify with your governing body
Clinical use in neurological applications

About this library

This library is published for education. It summarizes published research on compounds studied in this field. Many have no approved medical use, and several cannot lawfully be compounded in the United States. The presence of a page here does not mean Paragon offers that compound. Nothing on these pages is an offer to treat.

This page is general education about a compound studied in this field. Nothing here is medical advice, a recommendation, or an offer to prescribe or supply. A page appearing in this library does not mean Paragon Sports Medicine offers that compound.

Disclaimer: This information is provided for educational purposes only and does not constitute medical advice. Semax is not approved by the FDA for human therapeutic use. Patients should consult with qualified healthcare providers before considering any peptide therapy.

Statements on this page have not been evaluated by the FDA and are not intended to diagnose, treat, cure, or prevent any disease. Many peptides described here are not FDA approved for the uses discussed, and some cannot lawfully be compounded in the United States. Nothing on this page is medical advice or a recommendation for any individual. Whether any therapy is appropriate depends on your history, your laboratory results, and a clinical evaluation. Individual results vary. This page is published for education. Use of this site does not create a physician-patient relationship.

References

01
Functional Connectomic Approach to Studying Selank and Semax Effects. Dokl Biol Sci. 2020.
02
The Potential of the Peptide Drug Semax and Its Derivative for Correcting Pathological Impairments in the Animal Model of Alzheimer's Disease. Acta Naturae. 2025.
03
Semax peptide targets the mu opioid receptor gene Oprm1 to promote deubiquitination and functional recovery after spinal cord injury in female mice. Br J Pharmacol. 2025.
04
Semax, a Synthetic Regulatory Peptide, Affects Copper-Induced Abeta Aggregation and Amyloid Formation in Artificial Membrane Models. ACS Chem Neurosci. 2022.
05
Semax, a Copper Chelator Peptide, Decreases the Cu(II)-Catalyzed ROS Production and Cytotoxicity of Abeta by Metal Ion Stripping and Redox Silencing. Bioinorg Chem Appl. 2025.