Semax

Overview

Semax is a synthetic heptapeptide developed at the Institute of Molecular Genetics of the Russian Academy of Sciences, primarily by Nikolai Myasoedov, Ashmarin, and colleagues — the same research group responsible for Selank. Semax is based on the fragment ACTH(4-7) — four amino acids from adrenocorticotropic hormone (ACTH) — extended with a C-terminal Pro-Gly-Pro sequence to enhance metabolic stability.

ACTH(4-10) and its subfragments were identified in the 1960s and 1970s as having neurotrophic and cognitive-enhancing effects independent of ACTH's adrenal-stimulating activity. The critical insight was that the cognitive effects of ACTH reside in the 4-10 amino acid segment and do not require the full 39-amino-acid hormone. Importantly, Semax does not stimulate adrenal cortisol production — the "steroidogenic" activity of ACTH is localized to a different region of the molecule.

In Russia, Semax has been approved as a prescription medication since 1994 and is available in two primary formulations:

• Semax 0.1% — prescribed for cognitive enhancement, memory disorders, and attention deficits
• Semax 1% — prescribed for acute stroke, transient ischemic attacks, and serious neurological conditions

Semax is one of the most extensively studied nootropic peptides, with a body of Russian-language literature spanning several decades. It is also available in modified forms — N-Acetyl Semax and N-Acetyl Semax Amidate (NASA) — that are reported to have enhanced stability and potency, though these modified versions have less published research.

Amino Acid Sequence

Semax is a heptapeptide with the following structure:

Met-Glu-His-Phe-Pro-Gly-Pro

• Molecular formula: C₃₇H₅₁N₉O₁₀S
• Molecular weight: 813.97 g/mol
• CAS Number: 80714-61-0

Structural features:

• Positions 1–4 (Met-Glu-His-Phe): Correspond to ACTH(4-7), the minimal fragment retaining neurotrophic activity
• Positions 5–7 (Pro-Gly-Pro): The stabilizing C-terminal extension (identical to the extension used in Selank)
• Methionine at position 1 is susceptible to oxidation, which has led to the development of modified forms:
  • N-Acetyl Semax — acetylation of the N-terminal methionine improves stability
  • N-Acetyl Semax Amidate (NASA) — both N-terminal acetylation and C-terminal amidation for maximum stability and reported enhanced potency

Mechanism of Action

BDNF and Neurotrophic Factor Modulation

Semax's most well-characterized mechanism is the upregulation of brain-derived neurotrophic factor (BDNF) and related neurotrophins:

• Increases BDNF mRNA and protein expression in the hippocampus, cortex, and basal forebrain
• Upregulates TrkB receptor expression (BDNF's primary receptor)
• Increases nerve growth factor (NGF) in some brain regions
• Modulates expression of neurotrophins NT-3 and NT-4/5

BDNF upregulation is considered central to Semax's effects on:

• Long-term potentiation (LTP) and memory formation
• Neuronal survival and resistance to excitotoxic damage
• Synaptic plasticity and dendritic branching
• Neurogenesis in the hippocampal dentate gyrus

Dopaminergic and Serotonergic Modulation

Semax influences monoamine neurotransmitter systems:

• Modulates dopamine turnover in the striatum and prefrontal cortex
• Influences serotonin metabolism in cortical and limbic regions
• Affects the balance of dopamine metabolites (DOPAC, HVA)
• These monoamine effects contribute to attention, motivation, and mood modulation

Neuroprotective Mechanisms

In stroke and ischemia research, Semax has demonstrated neuroprotection through:

• Reduction of oxidative stress markers in ischemic tissue
• Inhibition of NO synthase overactivation during ischemia-reperfusion
• Anti-inflammatory effects — downregulation of pro-inflammatory cytokines in the ischemic penumbra
• Modulation of apoptotic pathways (upregulation of Bcl-2, downregulation of caspase-3)
• Enhanced expression of genes involved in cell survival and immune defense

Gene Expression Effects

Transcriptomic studies have revealed broad gene expression effects of Semax in brain tissue:

• Upregulation of neurotrophic factor genes
• Modulation of immune/inflammatory gene clusters
• Effects on ion channel and neurotransmitter receptor gene expression
• Changes in vascular and angiogenic gene expression following ischemic stroke

Absence of Steroidogenic Activity

Despite being derived from ACTH, Semax does not stimulate adrenal cortisol production. The steroidogenic activity of ACTH requires the N-terminal sequence (amino acids 1-24), which is not present in Semax. This is a critical distinction that allows Semax to provide ACTH's neurotrophic benefits without HPA axis activation.

Research Summary

Area of Study	Key Finding	Notable Reference
BDNF upregulation	Increased BDNF mRNA and protein in hippocampus and cortex; enhanced TrkB signaling	Dolotov et al., Neuroscience Letters, 2006
Acute ischemic stroke	Improved neurological outcomes and reduced infarct volume in clinical trials; approved in Russia for stroke	Gusev et al., Zhurnal Nevrologii i Psikhiatrii, 2005
Cognitive enhancement	Improved attention, memory consolidation, and learning in both animal models and human subjects	Ashmarin et al., Neuroscience and Behavioral Physiology, 1997
Gene expression (stroke)	Modulated expression of 24 genes involved in immune response, vascular function, and cell survival in rat ischemic brain tissue	Medvedeva et al., BMC Genomics, 2014
Neuroprotection	Reduced oxidative stress markers and apoptotic cell death in ischemia models	Storozhevykh et al., Bulletin of Experimental Biology and Medicine, 2007
Optic nerve disease	Improved visual function parameters in patients with optic nerve pathology (clinical trial in Russia)	Polunin et al., Vestnik Oftalmologii, 2000
Attention deficit	Improved attention metrics in children with attention deficit conditions	Aseev et al., Zhurnal Nevrologii i Psikhiatrii, 2007
Neurotrophic factors	Upregulated NGF, BDNF, and TrkB in basal forebrain and hippocampus	Agapova et al., Doklady Biological Sciences, 2007
Comparative with Selank	Different neurotransmitter profiles: Semax more dopaminergic/stimulating; Selank more GABAergic/anxiolytic	Kozlovskaya et al., Bulletin of Experimental Biology and Medicine, 2003
N-Acetyl Semax	Enhanced stability and reported greater potency compared to standard Semax; less published data	Community reports; limited published PK data

Pharmacokinetics

• Half-life: Several minutes in plasma (short, typical of small peptides); Pro-Gly-Pro extension provides ~5x stability vs. ACTH(4-7)
• Route: Intranasal (primary; approved formulation in Russia); subcutaneous injection (research)
• Intranasal bioavailability: Direct nose-to-brain delivery via olfactory and trigeminal nerve pathways
• Onset of action: Cognitive effects reported within 30–60 minutes; neuroprotective effects in stroke protocols require continued administration
• CNS penetration: The intranasal route bypasses the blood-brain barrier; systemic administration would result in minimal CNS exposure
• Metabolism: Proteolytic degradation; N-acetyl and amidated forms resist degradation more effectively
• Dosing frequency: Typically 2–3 times daily in approved Russian protocols (0.1% solution, 2–3 drops per nostril)

Modified Forms

• N-Acetyl Semax: Acetylation of the N-terminal methionine prevents oxidation and aminopeptidase cleavage; reported to be more potent per unit dose
• N-Acetyl Semax Amidate (NASA): Both N-acetyl and C-terminal amide modifications; reported by the community as the most potent form, though published comparative data is limited

Dosing Protocols

The following dosing information is compiled from published research and community discussion for educational purposes only. No FDA-approved human dosing guidelines exist for most research peptides. Always consult a qualified healthcare professional.

Reconstitution

Parameter	Value
Vial size	5 mg
Bacteriostatic water	3.0 mL
Concentration	~1,667 mcg/mL
Storage (reconstituted)	2-8 °C, avoid freeze-thaw cycles
Storage (lyophilized)	-20 °C

Dosing Schedule

Phase	Dose	Frequency	Duration
Initial	200-300 mcg	Once daily	Weeks 1-4
Maintenance	400-500 mcg	Once daily	Weeks 5-12

Syringe Measurements (U-100 insulin syringe)

Dose	Units	Volume
200 mcg	12 units	0.12 mL
300 mcg	18 units	0.18 mL
400 mcg	24 units	0.24 mL
500 mcg	30 units	0.30 mL

Cycle Guidelines

• Cycle length: 8-12 weeks continuous; extended protocols use 6-8 weeks on / 2-4 weeks off up to 16 weeks
• Route: Subcutaneous injection
• Titration: Increase by ~100 mcg every 1-2 weeks
• Timing: Consistent daily timing recommended
• Injection sites: Rotate between abdomen, thighs, and upper arms

Common Discussion Topics

1. Semax vs. Selank — The two Russian neuropeptides are frequently compared. Semax is characterized as more stimulating and cognitive-enhancing (dopaminergic emphasis), while Selank is more anxiolytic and calming (GABAergic emphasis). Some protocols combine both.

2. Modified forms (N-Acetyl, NASA) — Community discussion around whether the modified forms offer meaningful improvements over standard Semax. N-Acetyl Semax Amidate is considered the most potent and stable variant.

3. Stroke and neuroprotection — Semax's approved use in Russia for acute stroke is a significant differentiator. The neuroprotective data in ischemic models is among the more compelling clinical evidence for any nootropic peptide.

4. Intranasal technique — Proper intranasal administration is critical for CNS delivery. Discussion covers spray vs. drops, head positioning, nasal congestion management, and formulation stability.

5. BDNF modulation — The BDNF upregulation mechanism connects Semax to broader neuroplasticity research and is of particular interest to the nootropic community.

6. Russian research validation — As with Selank, the concentration of published data in Russian literature and the limited number of international replication studies are discussed as limitations, though the body of evidence is substantial within its context.

Related Compounds

• Selank — a Russian-developed tuftsin analog with anxiolytic and immunomodulatory properties; commonly discussed alongside Semax
• ACTH(4-10) — the parent fragment from which Semax is derived; has neurotrophic activity but shorter half-life
• BPC-157 — unrelated structurally but shares broad neuroprotective and pleiotropic characteristics
• Dihexa — a small peptide (hexanedioic acid diamine) studied for cognitive enhancement through HGF/c-Met pathway; sometimes discussed in the same nootropic context
• Cerebrolysin — a mixture of neurotrophic peptides derived from porcine brain; prescribed for cognitive impairment and stroke in some countries; shares the neuroprotective peptide therapeutic category
• P21 (derived from Cerebrolysin) — a synthetic peptide fragment with BDNF-mimetic properties; similar mechanistic profile