Semax
Synthetic ACTH(4-10) analog (heptapeptide)
A 7-amino-acid peptide studied in neuroprotection and cognitive research.
Overview
Semax was developed in Russia (Institute of Molecular Genetics, Russian Academy of Sciences) as a synthetic analog of a fragment of adrenocorticotropic hormone (ACTH 4-10) with an added Pro-Gly-Pro tail for stability. It is marketed in Russia and some neighboring countries.
At a glance
What Semax does
Semax is a synthetic heptapeptide based on the ACTH(4-10) fragment of adrenocorticotropic hormone, extended with a Pro-Gly-Pro tail that greatly increases its stability and, importantly, strips out the adrenal (cortisol-releasing) activity of the parent hormone. What it does in research is act as a neuroprotective and pro-cognitive agent: it preserves neurons under ischemic and oxidative stress and enhances attention, memory consolidation, and adaptation to stress.
At the mechanistic level, Semax engages melanocortin receptor pathways in the CNS and drives a broad neurotrophic response. In cerebral ischemia models it accelerates and amplifies expression of BDNF and its receptor TrkB, and prevents the ischemia-induced fall in NT-3, NGF, and related trophic factors. This melanocortin-linked, neurotrophin-mediated action antagonizes the excitotoxic, inflammatory, and apoptotic cascades that damage tissue after stroke, and also supports neurogenesis. Semax additionally modulates the brain-derived neurotrophic factor / dopaminergic and serotonergic systems and inhibits enkephalin-degrading enzymes, which contributes to its effects on attention and mood.
The evidence is stronger than for many research peptides in this class: Semax has been a registered pharmaceutical in Russia since the 1990s (nasal spray) for ischemic stroke recovery, cognitive impairment, optic nerve conditions, and attention deficits, and its strongest human data are in acute neurological injury and optic-nerve disease. Still, most rigorous mechanistic work is animal/in-vitro, and large independent Western clinical trials are lacking, so nootropic use in healthy people remains largely extrapolation.
Effects reported in research
- Neuroprotection in rat cerebral ischemia-reperfusion models, reducing infarct-related damage (animal).
- Earlier and stronger upregulation of BDNF and TrkB after ischemic injury (animal).
- Prevention of the ischemia-induced decline in NT-3, NGF, and TrkA/TrkC transcription (animal).
- Registered clinical use in Russia for ischemic stroke recovery and cognitive impairment (human).
- Reported benefit in optic nerve atrophy and other optic-nerve conditions (human, Russian clinical use).
- Enhanced attention and memory consolidation in cognitive-task studies (animal and human).
- Antagonism of excitotoxic, inflammatory, and apoptotic pathways in neurodegeneration models (preclinical).
- Inhibition of enkephalin-degrading enzymes, contributing to mood and stress-adaptation effects (preclinical).
Effects listed reflect findings reported in the research literature — many in animal or in-vitro models. Listing an effect is not a claim of efficacy or a therapeutic indication in humans.
Mechanism of action
Semax is an analog of the ACTH(4-10) melanocortin fragment but is described as being devoid of hormonal (corticotropic) activity. Research reports that it influences brain-derived neurotrophic factor (BDNF) and its receptor TrkB, modulates the expression of neurotrophin-related and immune genes, and may affect monoaminergic systems. It has been studied for neuroprotective and nootropic effects, potentially via effects on the melanocortin system.
Mechanistic description reflects published research-literature understanding. Much peptide research is preclinical (in-vitro or animal-model); mechanism in humans may differ and is not established for many compounds.
What it's studied for
Research contexts in which Semax appears in the literature. Listing a research area is not a claim of efficacy or a therapeutic indication.
Key characteristics
- Derived from the ACTH(4-10) melanocortin fragment but reported to lack corticotropic hormonal activity
- Marketed in Russia, including for stroke and cognitive/attention indications
- Commonly administered intranasally in the Russian clinical setting
- Studied for effects on BDNF expression and neurotrophic signaling
- Not FDA- or EMA-approved; Western clinical trial evidence is limited
Reported research dosing reference only
Educational reference, not dosing guidance. The figures below summarize amounts reported in published research and research-community protocols, provided for educational and research context only. They are not medical advice, not a recommendation, and not instructions for human use. Semax is a research compound.
Cognitive research protocols commonly reference roughly 300-800 mcg/day intranasal, while Russian stroke studies used much higher milligram-per-day intranasal doses. These are reference figures for research context only, not human dosing guidance.
- Rodent cognition studies: ~50-500 mcg/kg (most in the 100-300 mcg/kg range)
- Healthy-adult research: single 600 mcg intranasal dose used in a controlled attention/working-memory study
- Cognition research-protocol reference: ~300-800 mcg/day intranasal or subcutaneous
- Acute ischemic stroke research: ~9-18 mg/day intranasal
Plasma half-life is only ~2-5 minutes; BDNF/NGF-driven effects are measured over hours
How it compares
Semax is a melanocortin (ACTH)-derived peptide oriented toward neuroprotection and cognition, whereas Selank derives from tuftsin and is oriented toward anxiolysis.
Commonly studied alongside
Compounds frequently researched together with Semax in the literature. Cross-referenced for research context — not a usage or combination recommendation.
Handling & Stability
Lyophilized peptides are stored cold, protected from light, and reconstituted only at the time of intended in-vitro work.
- Avoid repeated freeze-thaw cycles
- Verify supplier lot and Certificate of Analysis
- Follow institutional lab-safety protocols
Analytical & COA Concepts
Reputable research suppliers publish a third-party Certificate of Analysis per batch. Key analytical concepts referenced in COAs include:
Category Context
Semax sits in the Cognitive & Nootropic area of the PeptiDex library.
- Entry type: Research compound reference
- Browse the full library →
- Glossary of terms →
Where researchers source Semax
For researchers studying Semax, third-party suppliers such as Practically Natty Peptides offer research-grade material with third-party Certificates of Analysis and US-based shipping.
View research-supplier listing →
Outbound link to a third-party research supplier. Inclusion does not constitute endorsement; all editorial content is developed independently.
Frequently asked questions
What is Semax and what is it studied for?
Semax is a synthetic heptapeptide that adds a stabilizing Pro-Gly-Pro tail to the ACTH(4-7) fragment, developed at the Russian Academy of Sciences. It is studied in research models of cognition, attention, memory, and neuroprotection, where it is reported to upregulate BDNF and NGF messenger RNA in the hippocampus and cortex.
How does Semax achieve long effects despite a very short half-life?
The parent peptide has a plasma half-life of only about 2-5 minutes, yet its transcriptional effects on neurotrophic factors are measured over hours. The Pro-Gly-Pro tail slows peptidase cleavage relative to the native ACTH(4-7) fragment, allowing enough exposure to drive downstream BDNF/NGF signaling that outlasts the peptide itself.
Why is intranasal delivery emphasized in Semax research?
Intranasal administration provides direct nose-to-brain transport, achieving rapid CNS exposure without depending on blood-brain-barrier crossing from systemic circulation. Given the peptide's very short plasma half-life, this route is a common design choice in cognition and neuroprotection studies.
How does Semax differ from Selank?
Both are Russian heptapeptides with a Pro-Gly-Pro stabilizing tail, but Semax derives from ACTH(4-7) and is studied mainly for cognition, focus, and neuroprotection, whereas Selank derives from tuftsin and is studied primarily for anxiety and stress modulation.
Has Semax been studied in stroke research?
Yes. Semax has been evaluated in Russian clinical research in acute ischemic stroke at higher intranasal doses on the order of several milligrams per day, with reported endpoints around neurological recovery. It is not FDA- or EMA-approved and is sold in the US only for laboratory research.
Answers are educational summaries of research-literature context and do not constitute medical advice. See the Research Library, COA guide, and Storage & Handling guide for more.