Semax: ACTH(4-10) Analog Nootropic Research Overview

Semax is a synthetic heptapeptide nootropic and neuroprotective agent developed in Russia. Its sequence, Met-Glu-His-Phe-Pro-Gly-Pro, is derived from the adrenocorticotropin hormone fragment ACTH(4-10) (Met-Glu-His-Phe-Arg-Trp-Gly), to which a Pro-Gly-Pro tripeptide was appended at the C-terminus for improved stability. The core ACTH(4-7) sequence (Met-Glu-His-Phe) is responsible for much of the behavioral and cognitive activity, while the C-terminal extension prolongs its activity in plasma. Semax was developed at the Institute of Molecular Genetics of the Russian Academy of Sciences, principally by Igor Ashmarin and collaborators including Natalia Levitskaya. Like Selank, the research literature is dominated by Russian-language publications. This guide presents findings from PubMed-indexed papers while being transparent about the limitations of that literature.

What Is Semax?

ACTH is a 39-amino-acid pituitary hormone with a well-characterized role in stimulating cortisol release from the adrenal cortex. Its 4–10 fragment, however, does not stimulate cortisol release and was instead found to have distinct behavioral effects in animal models — improving learning, memory, and attention in preclinical experiments conducted in the 1970s and 1980s. This observation became the basis for developing Semax, which was designed to capture those cognitive properties in a metabolically stable form.

Semax is registered as a pharmaceutical drug in Russia and Ukraine, available as a nasal spray at concentrations of 0.1% and 1%. It is approved in Russia for a range of neurological applications including acute ischemic stroke, cognitive impairment, and attention disorders. It is not approved by the FDA, EMA, MHRA, or TGA. Outside Russia and Ukraine, it is available as a research peptide only.

Mechanism of Action

Several complementary mechanisms have been identified in preclinical research:

BDNF and TrkB upregulation: A PubMed-indexed study (Dolotov et al., 2006) demonstrated that Semax, administered intranasally, significantly upregulated BDNF mRNA and protein expression in the rat hippocampus, as well as TrkB (the BDNF receptor) expression. BDNF is a critical modulator of synaptic plasticity, long-term potentiation, and neuronal survival. This mechanism is considered central to Semax's cognitive and neuroprotective effects. Monoaminergic effects: Levitskaya et al. (2006) showed that Semax activates dopaminergic and serotoninergic brain systems in rodents, enhancing dopamine release in the striatum and potentiating locomotor responses to D-amphetamine. These monoaminergic effects may contribute to the peptide's attention-enhancing properties. Basal forebrain BDNF binding: A separate PubMed-indexed study demonstrated that Semax binds specifically to a site in the rat basal forebrain and increases BDNF protein levels, suggesting direct interaction with BDNF-related signaling pathways (Dolotov et al., 2006).

Semax does not stimulate the hypothalamic-pituitary-adrenal (HPA) axis or cortisol release — a critical distinction from the parent ACTH molecule and its longer fragments.

What the Research Shows

Transparency note: As with Selank, the majority of Semax research originates from Russian research institutions and is published in Russian-language journals, including Zhurnal Vysshei Nervnoi Deyatelnosti, Eksperimental'naya i Klinicheskaya Farmakologiya, and Neuropeptides (Russian edition). PubMed-indexed publications in English are available but represent a fraction of the total literature, and they largely consist of translated abstracts. Independent replication by Western research groups is largely absent.

Cognitive and nootropic effects: Levitskaya et al. (1999) published an English-language PubMed-indexed paper reporting that repeated intranasal Semax administration improved learning in rats in a variety of behavioral paradigms. Manchenko et al. (subsequent work cited in reviews) extended these findings to attention and working memory models.

Neuroprotection: Semax has been studied in rodent models of dopaminergic neurotoxicity (MPTP model of Parkinson's disease). Kolomin et al. and Neuroprotective effects of Semax papers (Myasoedov et al. reviewed) documented reduced dopaminergic neuron loss in MPTP-treated animals. A 2021 PMC-indexed study (Semax attenuates MPTP-induced lesions) provided English-language evidence for neuroprotection in this model.

Alzheimer's disease model: A 2024 PMC study examined the effects of Semax and its derivative on behavioral characteristics and amyloidosis in transgenic mice modeling Alzheimer's disease. Both Semax and a derivative improved cognitive functions and reduced certain amyloid markers in this model — a preclinical finding that does not constitute evidence of efficacy in humans.

Human clinical data: Semax has been used clinically in Russia for acute ischemic stroke (intranasal administration during the acute phase) and for attention-deficit presentations. Russian clinical trial data supporting pharmaceutical registration are not published in Western peer-reviewed journals. No Phase 2 or Phase 3 randomized controlled trial for Semax has been published in English to this reviewer's knowledge, and no regulatory submission to FDA or EMA has been made.

Pharmacokinetics

English-language peer-reviewed PK data for Semax are limited. Available characterization from Russian pharmaceutical data and preclinical work suggests: Molecular weight: approximately 887 Da. Half-life in plasma: very short (minutes) for the intact peptide due to rapid endopeptidase cleavage. The C-terminal Pro-Gly-Pro extension improves stability relative to ACTH(4-10) but the parent compound is still rapidly cleared. CNS penetration: intranasal administration is the preferred route for CNS delivery. Semax administered intranasally reaches the brain via olfactory and trigeminal neural pathways, bypassing the blood–brain barrier. Subcutaneous systemic bioavailability to CNS is lower. Metabolism: rapid proteolysis to short peptide fragments including Pro-Gly-Pro (a naturally occurring tripeptide with potential independent activity) and Met-Glu-His-Phe.

Common Research Dose Ranges

Not medical advice. These are ranges reported in research literature, not personalized recommendations. Consult your physician.

Animal studies have used intranasal doses of approximately 0.05–0.5 mg/kg per administration. The Russian pharmaceutical formulation is available as 0.1% (low-dose, daily use) and 1% (acute clinical dosing) nasal sprays; each spray delivers approximately 50–100 mcg. Research-community intranasal doses typically cited are 200–1,000 mcg per session. Subcutaneous doses reported in research contexts range from 250–500 mcg. None of these human-scale doses have been studied in published dose-finding or pharmacokinetic trials meeting Western regulatory standards.

Storage and Handling

Semax is sold in research markets as a lyophilized powder or as a pre-formulated intranasal solution (sourced from Russian pharmacies where it is registered). Lyophilized Semax: store at −20 °C, protected from moisture and light. Reconstituted or pre-formulated solution: store at 2–8 °C and use within 28 days of opening or reconstitution. As a short peptide with a methionine residue at the N-terminus, Semax is susceptible to oxidation of the methionine sulfur under aerobic conditions; limit exposure to air when preparing and storing reconstituted solutions.

What Semax Is NOT

Semax is not ACTH. Despite being derived from ACTH(4-10), Semax does not bind the MC2R (ACTH receptor) with meaningful affinity and does not stimulate cortisol release or activate the HPA axis. Semax is not a stimulant in the amphetamine or caffeine sense. Its effects on dopamine and serotonin are modulatory rather than direct-release or reuptake-inhibiting. Semax is not FDA/EMA/MHRA/TGA approved. It is approved only in Russia and Ukraine. In Western markets it has research-chemical status only. Semax has not been validated in independent randomized controlled trials outside Russia. The clinical claims that appear in some secondary sources are based on Russian registration data that have not been peer-reviewed by Western standards.

References

See citations below. Core English-language PubMed references include Dolotov et al. 2006 (BDNF/TrkB), Levitskaya et al. 2006 (monoaminergic effects), and Semax neuroprotection in MPTP model (2021). Foundational Russian-language work by Ashmarin's group is accessible via translated abstract in PubMed (PMID 9173745).