Semax: Neuroprotective and Nootropic Peptide Research Guide — BDNF, Stroke Models, and Cognitive Research

Semax (Met-Glu-His-Phe-Pro-Gly-Pro) is a synthetic heptapeptide developed at the Institute of Molecular Genetics of the Russian Academy of Sciences (IMG RAS) in the 1980s. It is a structural analogue of ACTH(4-10) — the 7-amino acid fragment of adrenocorticotropic hormone at positions 4 through 10 of the 39-amino acid ACTH peptide.

Native ACTH(4-10) has known CNS-active properties but a plasma half-life of approximately 2–3 minutes. Semax incorporates a Pro-Gly-Pro stabiliser extension at the C-terminus to extend biological stability while maintaining and enhancing CNS-active properties.

Semax at a glanceSequence: Met-Glu-His-Phe-Pro-Gly-Pro (7 amino acids) · MW: ~888 Da · Parent: ACTH(4-10) · Developer: Institute of Molecular Genetics, Russian Academy of Sciences · Russian registration: ischaemic stroke, cognitive impairment · Key property: one of the strongest BDNF-upregulating peptides characterised in preclinical research

ACTH is a 39-amino acid peptide from the anterior pituitary whose primary endocrine function is stimulating cortisol production. Distinct ACTH fragments have independent CNS effects unrelated to adrenal stimulation.

The ACTH(4-10) fragment is the minimal active sequence responsible for ACTH's neurotrophic and pro-cognitive effects. Crucially, ACTH(4-10) does not stimulate cortisol production — the adrenal-stimulating activity resides in ACTH(1-24). This separation of cognitive/neurotrophic activity from hormonal activity made ACTH(4-10) analogues attractive research targets. Semax is the most extensively studied result.

Semax's most characterised mechanism is its potent upregulation of neurotrophic factors:

BDNF (Brain-Derived Neurotrophic Factor):

Semax is among the most potent upregulators of BDNF expression documented in peptide research — studies show 2–4× increases in hippocampal BDNF mRNA within hours of administration. BDNF is the primary driver of long-term potentiation (LTP, the cellular basis of memory), neuronal survival, synaptogenesis, and hippocampal neurogenesis. The magnitude of BDNF upregulation exceeds that documented for Selank and is comparable to exercise-induced BDNF increases in rodent models.

NGF (Nerve Growth Factor):

Semax also upregulates NGF expression in hippocampal and cortical tissue. NGF is required for the survival and maintenance of basal forebrain cholinergic neurons — the primary neurons responsible for acetylcholine-mediated memory processing and attention. NGF upregulation is particularly relevant to research on age-related cognitive decline.

VEGF (Vascular Endothelial Growth Factor):

In ischaemic stroke models, Semax promotes VEGF expression and angiogenesis at the ischaemic penumbra — the tissue surrounding the infarct core that is metabolically compromised but potentially salvageable. VEGF-driven angiogenesis restores perfusion to penumbral tissue, reducing secondary neuronal death.

Semax has the most extensive neuroprotection evidence base of the nootropic peptides, with a particularly strong signal in ischaemic brain injury models:

Ischaemic stroke (MCAO models):

• Significantly reduced infarct volumes vs controls, particularly when administered within the first few hours post-occlusion
• Improved neurological deficit scores (beam walk, rotarod, forelimb placing) at 24–72 hours post-MCAO
• Reduced neuronal apoptosis in the ischaemic penumbra (TUNEL staining, caspase-3 activity)
• Enhanced VEGF expression and microvessel density at the penumbra
• Reduced neuroinflammatory markers (IL-1β, TNF-α, activated microglia density) in peri-infarct tissue

Reperfusion injury:

Semax showed protective effects against reperfusion injury in both permanent and transient MCAO models, with reduced lipid peroxidation and oxidative stress markers — relevant because reperfusion paradoxically causes additional neuronal damage via ROS and inflammatory cascades.

Traumatic brain injury (TBI):

Controlled cortical impact models showed Semax reduces lesion volume, improves cognitive outcomes on Morris water maze at 2–4 weeks post-injury, and promotes axonal preservation in white matter tracts adjacent to the lesion.

Beyond neuroprotection, Semax has an established nootropic profile:

• Spatial learning (Morris water maze) — faster acquisition of hidden platform location and superior probe trial performance, most pronounced in animals with age-related or stress-induced cognitive impairment where baseline BDNF is suppressed
• Passive avoidance — improved memory consolidation consistent with BDNF/NGF-mediated hippocampal and cholinergic enhancement
• Attention — NGF upregulation supports basal forebrain cholinergic neurons, underlying improved attention in cholinergic dysfunction models relevant to Alzheimer's research
• Human data — limited Russian clinical research reported improvements in attention span and processing speed in subjects with mild cognitive impairment receiving nasal Semax; not replicated in independent Western RCTs as of 2026

Semax's registered delivery route is intranasal — exploiting anatomical pathways for CNS access:

• Olfactory pathway — olfactory neurons project axons directly through the cribriform plate to the olfactory bulb, connecting to limbic and prefrontal structures. Peptides absorbed by nasal mucosa can access these projections without crossing the BBB by conventional circulatory route.
• Trigeminal nerve pathway — trigeminal nerve innervates nasal mucosa and projects to the brainstem, providing posterior CNS access
• Systemic component — a portion enters systemic circulation via nasal blood vessels and reaches the brain via the BBB

Intranasal Semax produces detectable CNS effects with rapid onset (typically 5–15 minutes), consistent with olfactory pathway providing rapid access to limbic and prefrontal structures.

Semax holds pharmaceutical registration in Russia and Ukraine for:

• Ischaemic stroke — acute-phase treatment and recovery support
• Cognitive impairment — particularly in patients with cerebrovascular disease and age-related cognitive decline

The registered preparation is a 1% intranasal solution (approximately 200–1000 µg per dose). In 2001, Semax received approval by the Russian Ministry of Health as a nootropic agent for cognitive enhancement in healthy subjects as well as clinical populations — one of the few peptides with this regulatory status. Clinical evidence comprises Russian-language trials not replicated in large Western RCTs.

RetaLABS Semax is supplied as lyophilised powder.

• Add bacteriostatic water slowly along the vial wall; gently swirl until dissolved — do not shake or vortex
• Typical concentrations: 0.5–2mg/mL depending on protocol; for intranasal research: 1mg/mL in sterile isotonic saline
• Store lyophilised at −20°C, protected from light and moisture
• Reconstituted: 2–8°C, use within 4 weeks. Aliquot for single-use volumes if extended storage required.

See the Peptide Reconstitution & Storage Guide for general protocol notes.

What makes Semax particularly valuable for neuroprotection research?

Semax's BDNF upregulation magnitude — among the strongest documented for any peptide intervention — is the primary driver of neuroprotection research interest. In stroke models, the combination of BDNF-mediated neuroprotection plus VEGF-driven angiogenesis at the ischaemic penumbra addresses neuronal survival and perfusion restoration simultaneously.

Does Semax affect cortisol levels?

No. The cortisol-stimulating activity of ACTH resides in the ACTH(1-24) sequence. Semax is based on ACTH(4-10) — a fragment that lacks adrenal stimulating activity. Multiple studies confirm Semax administration does not significantly alter cortisol or adrenal hormone levels.

What is the difference between Semax and Selank?

Semax (ACTH analogue) is primarily neuroprotective and cognitively enhancing, with strong BDNF and NGF upregulation and mild stimulant-like properties. Selank (tuftsin analogue) is primarily anxiolytic, with moderate BDNF effects and immunomodulatory properties. The two are complementary.

Is Semax available in Australia?

Research-grade Semax is available in Australia for laboratory research purposes. It is not TGA-registered as a therapeutic product. All RetaLABS products are for laboratory research use only.

RetaLABS Semax is sourced from manufacturers providing a Certificate of Analysis (COA) with each batch. All products are for laboratory research use only.

For the complementary anxiolytic profile, see the Selank Research Guide. For the broader nootropic landscape, see the Nootropic Peptides Guide. For the Australian regulatory framework, see the Research Peptides Legal Guide.