Semax
ACTH(4-7)-Pro-Gly-Pro (Heptapeptide) · Met-Glu-His-Phe-Pro-Gly-Pro · ~813 Da
Executive Summary
Semax is a synthetic heptapeptide (Met-Glu-His-Phe-Pro-Gly-Pro) derived from an ACTH fragment, developed and used as a neuroactive intranasal drug in Russia. The strongest signal in peer-reviewed literature is not limitless nootropic enhancement, but context-dependent neurobiological modulation (neurotrophin expression, monoaminergic signalling, inflammatory gene programmes) most consistent in acute injury/stress paradigms and stroke models in animals. Human evidence exists but centres on small, older clinical studies (often Russian-language) with limited endpoints, plus a few neuroimaging experiments in healthy volunteers. This is far from the multi-centre, preregistered, blinded evidence base that social media implies. The U.S. FDA specifically identifies Semax as a Category 2 bulk substance with potential safety risks for compounding, citing immunogenicity, aggregation, peptide impurities, and limited safety information.
Semax is interesting and partially evidenced rather than proven and generalisable. The preclinical stroke/neuroprotection dossier is meaningful, but human-grade efficacy and safety certainty remain insufficient for broad claims. Regulatory signals materially raise the bar for how cautiously it should be discussed.
What Semax Is and What It Is Not
Semax is commonly described in the peer-reviewed literature as an ACTH-fragment analogue (ACTH(4-7)PGP / ACTH(4-10) analogue) with the sequence Met-Glu-His-Phe-Pro-Gly-Pro. The most prominent translational focus is neuroprotection and rehabilitation adjunct use in ischaemic stroke and other CNS conditions, with animal work spanning focal and transient MCA occlusion models, behavioural learning paradigms, and stress-related phenotypes.
- It is not an approved therapeutic drug by major Western regulators and should not be presented as a standard-of-care cognitive enhancer or stroke treatment.
- It is not supported by large, preregistered, blinded clinical trials for consumer-grade cognitive enhancement in healthy people.
- It does not 'rewire your genome' - the omics evidence is from injury-context-specific rat stroke models, not evidence of broad beneficial gene changes in healthy humans.
- It is not clearly safe - the FDA explicitly considers the available safety dossier inadequate for comfort in widespread compounded use.
Mechanism of Action
Neurotrophin modulation (BDNF/NGF)
Strongest mechanistic evidenceSemax has evidence for saturable, calcium-dependent binding sites in rat basal forebrain membranes (KD ~2.4 nM, BMAX ~33.5 fmol/mg protein). In vitro, Semax increased NGF and BDNF mRNA in glial cultures (~8-fold BDNF, ~5-fold NGF at ~30 minutes). In vivo, single intranasal dosing (50 ug/kg) produced rapid, region-specific changes: BDNF protein increased (~1.4x) with TrkB phosphorylation (~1.6x) in hippocampus, alongside improved conditioned avoidance responses.
BDNF changes in rats do not automatically equal cognitive enhancement in humans. The leap from rodent neurotrophin data to guaranteed nootropic effects is not established by clinical trials.
Monoaminergic modulation (dopamine/serotonin)
Plausible, animal-onlySemax potentiated extracellular dopamine release after D-amphetamine administration in rat striatum, and is described as activating dopaminergic and serotonergic brain systems. In neurotoxin models, daily intranasal Semax (0.2 mg/kg) reduced severity of MPTP-induced behavioural disturbances, attributed to dopaminergic modulation and neurotrophic action.
Monoamine-system modulation strengthens the case for caution with stimulant co-exposures rather than supporting risk-free focus boosts. This does not automatically imply a safe stimulant-like human effect profile.
Nitric oxide, mitochondrial protection, and cellular stress
Mechanistic anchor in injury modelsIn an incomplete global ischaemia model, Semax prevented enhanced nitric oxide generation in cerebral cortex and restored neurological function. At the cellular level, Semax (100 uM) delayed calcium dysregulation and mitochondrial membrane potential loss in cultured cerebellar granule cells under glutamate neurotoxicity and improved survival by ~30%.
Important mechanistic anchor, but at high in-vitro concentration and under excitotoxic insult conditions. Does not establish neuroprotection in healthy human brains.
Gene-expression modulation (omics evidence)
Context-dependent, misinterpreted in marketingIn permanent MCAO, a genome-wide microarray reported 96 genes altered at 3h and 68 at 24h, with immune-system genes representing >50% of modulated genes. In transient MCAO, RNA-Seq found 394 differentially expressed genes at 24h (FC>1.5, Padj<0.05). Protein-level follow-up showed reduced MMP-9, c-Fos, and JNK with increased CREB activation, consistent with reduced injury/inflammation signalling.
The omics literature supports Semax as a context-dependent modulator of post-ischaemic inflammatory and neurotransmission gene programmes, not as a general gene-therapy-like enhancer in healthy people.
Animal Evidence Map
The preclinical literature contains many positive findings, summarised below with stated limitations.
| Domain | Species | Dose | Outcome | Limitation |
|---|---|---|---|---|
| Neurotrophin binding and BDNF | Rat | Intranasal 50 & 250 ug/kg, single dose | Saturable binding (KD ~2.4 nM); BDNF increased in basal forebrain but not cerebellum | Rat tissue; binding site identity unclear; short timeframe (~3h assessment). |
| Hippocampal BDNF/TrkB and learning | Rat | Intranasal 50 ug/kg, single dose | BDNF protein ~1.4x increase, TrkB phosphorylation ~1.6x increase, improved conditioned avoidance | Acute effects only; animal learning task does not equal human cognition claims. |
| Neurotrophin gene expression | Rat | Intranasal 50 ug/kg, 1h exposure | Rapid, region-specific NGF/BDNF transcription changes in hippocampus and brainstem | Short duration; mRNA only; mixed directionality (NGF decreased in frontal cortex). |
| Focal cortical infarct and memory | Rat | Intranasal ~250 ug/kg/day, 6 days | Reduced cortical infarct volume and improved passive avoidance retention after photothrombotic injury | Limited abstract detail; translational gap to clinical stroke outcomes. |
| Ischaemia-reperfusion transcriptomics | Rat | IP 100 ug/kg post-occlusion + 1.5h + 5h after reperfusion | Reduced MMP-9, c-Fos, JNK; increased CREB at 24h post-tMCAO | Rodent model; targeted protein selection; clinical relevance uncertain. |
| Transcriptome modulation (pMCAO) | Rat | Not fully extractable (gene-expression focus) | 96 DEGs at 3h, 68 at 24h; immune/chemokine/immunoglobulin genes dominate (>50%) | Gene modulation is injury-context specific; not a general enhancement claim. |
| Transcriptome modulation (tMCAO) | Rat | Not fully extractable (gene-expression focus) | 394 DEGs at 24h (FC>1.5, Padj<0.05); suppressed inflammatory genes; activated neurotransmission genes | Small n typical for RNA-Seq (n=3/group); model-specific. |
| Dopaminergic injury (MPTP) | Rat | Intranasal 0.2 mg/kg daily | Reduced severity of MPTP-induced behavioural disturbances | Neurotoxin model does not equal human PD treatment; behavioural endpoints only. |
| Stress-gut axis and microbiota | Rat | IP 5-450 ug/kg, 12-15 min pre-stress | 50 & 150 ug/kg prevented stress-induced dysbiosis patterns during chronic restraint stress | Not a human gut-health claim; mechanistic attribution speculative. |
| Early-life stress and metabolic effects | Rat | Intranasal 50 ug/kg daily, postnatal day 15-28 | Reduced negative effects of neonatal isolation stress on weight/metabolic dysfunction; normalised corticosterone | Early-life rodent stress model; not weight-loss drug evidence. |
Human Evidence
Every published human study for Semax is reviewed below. None are randomised controlled trials.
Acute ischaemic stroke clinical study
Clinical study vs conventional therapy controlNot clearly randomised/blinded; control not placebo; older study; Russian-language; endpoints/analysis detail limited in abstract.
Suggestive signal, not definitive evidence.Post-stroke rehabilitation with BDNF monitoring
Clinical trial with subgroups by rehab timingNot a hard clinical endpoint trial (e.g., mortality/disability at 90 days); design details limited; Russian-language; causality confounding possible.
Largest study, but still not blinded RCT-level evidence.Optic nerve disease / partial atrophy
Comparative clinical groupsNon-English; unclear randomisation/blinding; sample size not in abstract; adjunctive therapy confounds.
Signal exists but study quality prevents conclusions.Healthy volunteer resting-state fMRI
Placebo-controlled imaging studyImaging surrogate only; very small sample; no behavioural or cognitive endpoints.
Neuroimaging curiosity, not clinical proof of cognitive enhancement.Hype vs Evidence
Common online claims compared against what the published evidence actually supports.
| Claim | Social Media Implies | Evidence Supports | Verdict |
|---|---|---|---|
| Massively boosts BDNF, making you smarter | Guaranteed cognitive enhancement via BDNF increase | Semax increases BDNF/NGF mRNA in glial cultures and changes neurotrophin gene expression in rat brain; BDNF protein and TrkB activation changes in rat hippocampus. Human cognitive enhancement in healthy people is not established by robust trials. |
Preclinical support; overgeneralised to humans
|
| Proven for stroke recovery | Established stroke treatment | Human studies exist but are small, often not placebo-controlled, largely Russian-language. Some report improved recovery dynamics and BDNF associations, but this is not equivalent to large, blinded, contemporary stroke RCT evidence. |
Suggestive but not definitive
|
| Rewires hundreds of genes in your brain | Gene-therapy-like enhancement for healthy people | In rat stroke models, 68-96 DEGs in pMCAO microarray and 394 DEGs in tMCAO RNA-Seq at 24h (FC>1.5 with Padj criteria). This is injury-context-specific transcriptomic modulation, not broad beneficial genome rewiring in healthy humans. |
Supported in injury models; misinterpreted
|
| Anti-inflammatory and neuroprotective in general | Universal brain protection | In tMCAO models, findings consistent with reduced inflammatory gene activation and markers (MMP-9/c-Fos/JNK) and increased CREB activation. Accurate to call this neuroprotective in specific rodent injury models, not universally neuroprotective. |
Preclinically supported; general claims overstated
|
| Risk-free / no side effects | Safe enough for unsupervised self-use | Safety reporting in accessible abstracts is limited. FDA explicitly highlights immunogenicity, impurity concerns, and limited safety information for compounding contexts. Lack of reported adverse events does not equal proof of safety. |
Misleading; safety is uncertain
|
| WADA-safe for athletes | Permitted in sport | WADA regulates peptide categories. This review could not confirm Semax's exact 2026 prohibited list status due to access limitations. Athletes should verify status via official lists and national anti-doping bodies. |
Not verifiable; assume prohibited
|
Evidence Strength Ratings
Each domain rated on a 0-5 scale based on quality and quantity of available evidence.
Safety, Side Effects & Regulatory Status
Human PK/ADME data were not identified in primary sources. Mechanistic metabolism work in rats shows Semax is degraded in blood/serum with prominent roles for bestatin-sensitive aminopeptidases (N-terminal cleavage) and a measurable contribution from ACE; Semax appears more stable than ACTH(4-10) against some enzymatic degradation pathways. A rat pharmacokinetics report describes tritium-labelled Semax penetrating brain and eyes after intranasal administration, but full quantitative PK parameters are not available. Marketing claims about rapid absorption and minute-range half-life exist on vendor sites but are not peer-reviewed primary PK evidence.
Peer-reviewed abstracts rarely report adverse events or discontinuation rates in sufficient detail to quantify risk. Preclinical work shows biological activity at a range of doses and routes (intranasal, intraperitoneal), but this is not equivalent to systematic toxicology, reproductive risk profiling, carcinogenicity assessment, or long-term neuropsychiatric safety surveillance. If a product is not sourced via a regulated pharmaceutical channel, identity, purity, and sterility cannot be assumed.
Explicitly cites potential significant safety risks for compounding: immunogenicity risk for certain routes, aggregation and peptide-related impurity complexity, and limited safety information for proposed routes. The agency considers the available safety dossier inadequate for widespread compounded use.
View Official Source →No EMA marketing authorisation evidence was identified. Any EU clinical use claims should be treated as non-authorised and non-standard.
View Official Source →WADA's Prohibited List regulates peptide hormones and growth factors. This review could not reliably verify whether Semax is named in the 2026 document. Athletes should consult the current WADA list directly via official channels and national anti-doping agencies.
View Official Source →What We Still Don't Know
- No large, preregistered, blinded human clinical trials for cognitive enhancement in healthy people.
- No robust human pharmacokinetics (PK/ADME) data in the public English-language literature; animal PK does not bridge this gap.
- No comprehensive adverse-event profile; systematic toxicology, reproductive risk, and long-term neuropsychiatric safety data are missing.
- Dose-exposure understanding is a major gap: animal studies span intranasal and intraperitoneal routes across wide ug/kg ranges, while human studies report mg-range daily totals without human PK bridging.
- Which transcriptomic signals predict functional outcomes vs epiphenomena is unresolved, and whether omics effects replicate across labs and species.
- AMPK and NRF2 pathway activation claims could not be confirmed from primary sources and should be treated as unsupported marketing add-ons.
References
All primary sources cited in this review. Links open in new tabs.
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Saturable binding sites in rat basal forebrain membranesTritiated Semax binding study demonstrating Ca2+-dependent, saturable binding with KD ~2.4 nM and BMAX ~33.5 fmol/mg protein
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Hippocampal BDNF/TrkB activation and conditioned avoidanceSingle intranasal dose (50 ug/kg) increased BDNF protein (~1.4x) and TrkB phosphorylation (~1.6x) in rat hippocampus with behavioural changes
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Region-specific NGF and BDNF gene expression changesRapid region-specific changes in neurotrophin mRNA after single intranasal Semax (50 ug/kg): increases in hippocampus, decreases in frontal cortex for NGF
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NGF/BDNF mRNA induction in basal forebrain gliaSemax increased BDNF mRNA ~8-fold and NGF mRNA ~5-fold at ~30 min peak in newborn rat basal forebrain glial cultures
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Dopaminergic and serotonergic brain system activationSemax potentiated extracellular dopamine release after D-amphetamine and activates dopaminergic and serotonergic brain systems in rats
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MPTP neurotoxin model: behavioural protectionDaily intranasal Semax (0.2 mg/kg) reduced severity of MPTP-induced behavioural disturbances attributed to dopaminergic modulation
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Nitric oxide prevention in global ischaemia modelSemax prevented enhanced NO generation in cerebral cortex and restored neurological function in incomplete global ischaemia
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Mitochondrial protection in glutamate neurotoxicitySemax (100 uM) delayed calcium dysregulation and mitochondrial membrane potential loss in cerebellar granule cells under glutamate neurotoxicity; ~30% improved survival
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Genome-wide microarray in permanent MCAOIllumina RatRef-12 microarray (22,226 genes); 96 DEGs at 3h and 68 at 24h; immune-system genes >50% of Semax-modulated genes
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RNA-Seq analysis in transient MCAO model394 differentially expressed genes at 24h after tMCAO (FC>1.5, Padj<0.05); suppressed inflammatory genes and activated neurotransmission genes
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Post-ischaemic protein changes (MMP-9, CREB, JNK)IP Semax 100 ug/kg post-occlusion: downregulated MMP-9, c-Fos, JNK; upregulated CREB in subcortical structures at 24h
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Focal cortical ischaemia: infarct volume and memoryIntranasal Semax (~250 ug/kg/day, 6 days) reduced cortical infarct volume and improved passive avoidance retention in photothrombotic model
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Enkephalin-degrading enzyme inhibitionSemax inhibited enkephalin-degrading enzymes in human serum (IC50 ~10 uM) more potently than some comparator inhibitors
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Amyloid-beta copper complex interactionSemax reduced amyloid-beta:Cu2+ complex formation and altered aggregation kinetics in artificial membrane models
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Semax enzymatic degradation in rat blood/serumN-terminal cleavage via aminopeptidases and ACE contribution; Semax more stable than ACTH(4-10) against some pathways
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Acute ischaemic stroke clinical study30 Semax vs 80 controls; doses 12 mg (moderate) and 18 mg (severe) daily for 5-10 days; faster regression of neurological deficits
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Post-stroke rehabilitation and BDNF monitoring110 patients; 6000 ug/day for 10 days (2 courses); plasma BDNF increased and associated with better Barthel index dynamics
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Optic nerve disease treatmentComparative clinical groups: intranasal drops vs endonasal electrophoresis vs control; improvements in visual acuity and electrophysiology
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Healthy volunteer resting-state fMRI study14 Semax vs 10 placebo; intranasal 1% Semax; greater DMN rostral subcomponent volume at 5/20 min post-administration
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Chronic restraint stress and colon microbiotaIP 50 & 150 ug/kg prevented stress-induced dysbiosis patterns in rats under chronic restraint stress
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Neonatal isolation stress and metabolic effectsIntranasal 50 ug/kg daily postnatal day 15-28; reduced negative effects of neonatal stress on weight and normalised corticosterone
View the compound profile for Semax including dosage forms, administration routes, and category information.
View Compound Profile →Frequently Asked Questions About Semax
Semax can increase BDNF and NGF mRNA in rat brain regions and glial cultures, and BDNF protein and TrkB activation have been measured in rat hippocampus. However, human cognitive enhancement in healthy people is not established by robust clinical trials. The leap from rodent neurotrophin changes to guaranteed human intelligence gains is not supported.
Human studies exist, including small clinical studies in acute ischaemic stroke and post-stroke rehabilitation showing improved neurological recovery dynamics and associations with increased plasma BDNF. However, these are small, often not clearly placebo-controlled, frequently Russian-language, and do not represent large, blinded, contemporary stroke RCT evidence.
Safety is uncertain. Peer-reviewed abstracts rarely report adverse events in sufficient detail. The U.S. FDA flags Semax as Category 2 with potential significant safety risks for compounding, citing immunogenicity risk, aggregation and peptide-related impurity complexity, and limited safety information for proposed routes.
A comprehensive side effect profile has not been established in English-language peer-reviewed literature. Preclinical work shows biological activity at various doses and routes, but systematic toxicology, reproductive risk profiling, and long-term neuropsychiatric safety surveillance data are not available in the public record.
In rat stroke models, Semax alters dozens to hundreds of differentially expressed genes (68-96 in permanent MCAO; 394 in transient MCAO at 24h). This is injury-context-specific transcriptomic modulation in rodents, not evidence of broad beneficial genome rewiring in healthy humans.
Semax is not authorised as a medicine by major Western regulators. The U.S. FDA classifies it as a Category 2 bulk drug substance with cited safety concerns for compounding. WADA regulates peptide categories. Athletes should verify status via official prohibited lists and national anti-doping bodies.
The clearest mechanistic evidence involves neurotrophin modulation (BDNF/NGF expression) via saturable binding sites in basal forebrain, monoaminergic system modulation (dopamine and serotonin), and anti-nitrosative/mitochondrial protection under injury conditions. Effects appear most consistent in acute injury/stress paradigms rather than baseline enhancement.
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Last reviewed: March 1, 2026