Semax
BDNF Upregulation & Neuroprotective Signaling
Semax — ACTH(4-7) Pro-Gly-Pro Analog Nootropic
Last reviewed: August 2026
Semax is a synthetic heptapeptide derived from a fragment of ACTH (adrenocorticotropic hormone) — a pituitary hormone — with modifications to remove its hormonal activity while preserving its neurological effects. Like Selank, it was developed in Russia and is approved there as a nootropic and neuroprotective drug. It's one of the most widely used cognitive peptides in the Russian medical system.
Semax's primary mechanism is the upregulation of BDNF (Brain-Derived Neurotrophic Factor) and NGF (Nerve Growth Factor) — proteins that promote the survival, growth, and maintenance of neurons. It also modulates dopaminergic and serotonergic neurotransmission, which may explain its reported effects on focus, memory, and mood. In Russian clinical use, it's been studied for stroke recovery, ADHD, optic nerve disease, and cognitive decline.
BDNF is one of the most important molecules in brain health — it's been called 'Miracle-Gro for the brain.' Low BDNF is associated with depression, cognitive decline, and neurodegenerative disease. A compound that reliably upregulates BDNF is of significant interest to neuroscience researchers. Semax's clinical use in Russia for stroke recovery provides a neuroprotection angle that's particularly compelling.
Semax is a well-characterized nootropic peptide with approved clinical status in Russia for neurological conditions. Its BDNF-upregulating mechanism is grounded in solid neuroscience. Like Selank, its evidence base is primarily in the Russian literature, though the underlying biology (BDNF, NGF) is extensively validated in Western research. Research-only compound outside Russia.
What is Semax?
Semax is a synthetic heptapeptide developed at the Institute of Molecular Genetics of the Russian Academy of Sciences, based on the ACTH(4-7) fragment (Met-Glu-His-Phe) with a C-terminal Pro-Gly-Pro extension for metabolic stability. It is approved in Russia and Ukraine as a nootropic and neuroprotective agent, with clinical applications in stroke rehabilitation, cognitive impairment, and attention deficit disorders.
Semax is distinguished from most nootropic compounds by its robust, well-characterized effect on brain-derived neurotrophic factor (BDNF) and its receptor TrkB — a neurotrophin signaling pathway that is central to synaptic plasticity, neurogenesis, and neuroprotection. Its mechanism is fundamentally different from stimulant-based cognitive enhancers, operating through neurotrophic rather than catecholaminergic pathways.
- Semax is a synthetic heptapeptide (Met-Glu-His-Phe-Pro-Gly-Pro) derived from the ACTH(4-10) fragment — the minimal sequence of adrenocorticotropic hormone required for cognitive effects, without the adrenal-stimulating activity of full ACTH.
- Primary mechanism: upregulation of BDNF (brain-derived neurotrophic factor) and NGF (nerve growth factor) expression in the hippocampus and frontal cortex, supporting neuroplasticity and neuroprotection.
- Registered as a pharmaceutical drug in Russia for ischemic stroke, TBI, and cognitive impairment; the Russian clinical dataset provides a meaningful safety and efficacy foundation for neuroprotective research.
- The Pro-Gly-Pro C-terminal extension (shared with Selank) increases resistance to enzymatic degradation by prolyl endopeptidase, extending CNS activity duration compared to the parent ACTH(4-10) fragment.
- Research applications include studying BDNF-mediated neuroplasticity, neuroprotection after ischemic injury, cognitive enhancement mechanisms, and the role of melanocortin peptides in CNS function.
Molecular Composition
Semax has the amino acid sequence Met-Glu-His-Phe-Pro-Gly-Pro, with a molecular weight of 813.94 Daltons. The core ACTH(4-7) sequence (Met-Glu-His-Phe) is the minimal fragment of adrenocorticotropic hormone that retains cognitive-enhancing activity without the adrenocortical stimulation of the full ACTH molecule. The Pro-Gly-Pro extension dramatically extends metabolic stability compared to the parent ACTH(4-7) tetrapeptide.
How Does It Work?
Semax enhances memory and cognitive function by upregulating BDNF and its receptor TrkB in the hippocampus, strengthening the synaptic connections underlying learning.
Semax's primary mechanism involves upregulation of BDNF and its high-affinity receptor TrkB in the hippocampus, frontal cortex, and basal forebrain. BDNF/TrkB signaling activates the PI3K/Akt and MAPK/ERK pathways, promoting neuronal survival, synaptic plasticity (LTP), and neurogenesis in the hippocampal dentate gyrus — the cellular substrates of learning and memory.
Semax also modulates the dopaminergic and serotonergic systems, increasing catecholamine turnover in the prefrontal cortex and limbic system. Additionally, it reduces neuroinflammation by suppressing NF-κB-mediated cytokine expression (IL-1β, TNF-α) in activated microglia, providing neuroprotective effects in ischemic and inflammatory models.
In rodent models of stroke, semax administration significantly reduces infarct volume and improves functional recovery, effects attributed to both its BDNF-mediated neuroprotection and its anti-inflammatory activity.
Key Research Pathways
BDNF / TrkB Signaling
Upregulates BDNF and TrkB in hippocampus and frontal cortex, activating PI3K/Akt and MAPK/ERK pathways for neuroplasticity and neuroprotection.
Synaptic Plasticity (LTP)
BDNF/TrkB-mediated enhancement of long-term potentiation in hippocampal circuits, the cellular basis of learning and memory consolidation.
NF-κB Neuroinflammation Suppression
Reduces microglial NF-κB activation and pro-inflammatory cytokine expression (IL-1β, TNF-α), providing neuroprotective effects.
Catecholamine Modulation
Modulates dopaminergic and serotonergic turnover in prefrontal cortex and limbic system, contributing to cognitive and mood effects.
Key Findings from the Literature
- Approved nootropic/neuroprotective agent in Russia and Ukraine for stroke and cognitive impairment
- Robust BDNF and TrkB upregulation in hippocampus and frontal cortex (Dolotov et al., 2006)
- Reduces cerebral infarct volume and improves functional recovery in stroke models
- Suppresses NF-κB-mediated neuroinflammation (IL-1β, TNF-α) in activated microglia
- Modulates dopaminergic and serotonergic systems in prefrontal cortex and limbic structures
- Enhances long-term potentiation (LTP) — the synaptic mechanism of memory consolidation
Evidence by Claimed Outcome
Each outcome rated by the highest level of evidence available. Tiers follow our 5-tier methodology.
Study counts reflect peer-reviewed publications in the evidence database below. "Theoretical" outcomes have mechanistic rationale only. Learn about our evidence tiers →
Structured Evidence Table
2 cited studies — model, sample size, outcome, and effect size from published literature.
| Study | Model | Sample | Outcome | Effect Size | Level |
|---|---|---|---|---|---|
Dolotov OV, et al. (2006) Semax, an analog of ACTH(4-10) with cognitive effects, regulates BDNF and trkB e… PubMed | Rodent (rat) — hippocampus | n=24 | Significant upregulation of BDNF and TrkB expression in hippocampus | BDNF mRNA: ~2× increase vs. control; TrkB: ~1.5× increase | Animal |
Gusev EI, et al. (1997) Effectiveness of Semax in acute period of hemispheric ischemic stroke (a clinica… PubMed | Human — clinical trial (ischemic stroke) | n=187 | Improved neurological outcomes and reduced disability in acute ischemic stroke | Significant improvement in neurological deficit scores vs. control (p<0.05) | Observational |
How Long It Lasts & How It Works in the Body
Semax — half-life, bioavailability, onset, and duration data
| Parameter | Value | Source |
|---|---|---|
| Half-Life (t½) | ~2–3 minutes (plasma) Extremely short; intranasal delivery bypasses systemic degradation | Preclinical Data |
| Time to Peak (Tmax) | ~5–10 minutes (intranasal) Rapid CNS delivery | Preclinical Data |
| Bioavailability (F) | Intranasal: ~50–70% (CNS delivery) Direct CNS delivery via nasal mucosa | Preclinical Data |
| Onset of Action | Minutes to hours Cognitive effects within hours; BDNF upregulation over days | — |
| Duration of Action | 4–8 hours Despite short plasma half-life | — |
ACTH(4-7) analog. Approved in Russia for cognitive enhancement and stroke recovery. BDNF upregulation is the primary mechanism for sustained cognitive effects.
References:
• Dolotov OV et al. J Neurochem 2006
• Manchenko DM et al. Peptides 2012
Important Research Context
Semax
Cognitive Research
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Technical Specifications
| Peptide Class | Synthetic heptapeptide (ACTH(4-7) analog) |
| Molecular Weight | 813.94 Da |
| Regulatory Status | Approved nootropic/neuroprotective in Russia and Ukraine |
| Parent Sequence | ACTH(4-7) + Pro-Gly-Pro stability extension |
| Available Sizes | 5mg vials |
| Form | Lyophilized powder |
| Purity | ≥99% (third-party tested) |
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Known Interactions
4 documented interactions for Semax
Selank (anxiolytic, GABA modulation) + Semax (BDNF upregulation, focus) — complementary neurological targets with no known negative interaction.
Interaction data is based on published research, known pharmacological mechanisms, and clinical practitioner experience. Evidence tiers: Clinical = human data; Emerging = preclinical/case reports; Theoretical = mechanism-based inference. Always consult a qualified healthcare provider before combining compounds.
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Supporting Research
Semax is approved in Russia for stroke rehabilitation and cognitive disorders, with real regulatory history. Supporting human trials are largely Russian-language, non-randomized, or non-placebo-controlled by Western standards. BDNF upregulation is the primary proposed mechanism, supported by animal and limited human data. No FDA or EMA approval; independent Western replication is limited.
References
- Gusev EI, et al.HUMAN — non-randomized, Russian-languageZhurnal Nevrologii i Psikhiatrii im. S.S. Korsakova. 1997. PubMedFunctional-scale improvement in stroke rehabilitation patients in uncontrolled clinical studies. Not independently replicated.
Research Databases
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