Semax is a synthetic heptapeptide analog of the ACTH(4-10) fragment (sequence MEHFPGP), stabilized with a C-terminal Pro-Gly-Pro extension and lacking the parent's hormonal activity. Research studies it as a neurotrophic and neuroprotective agent. It is a laboratory research compound and is not for human use.

What is the reported mechanism of Semax?

The most-cited mechanism in the literature is upregulation of brain-derived neurotrophic factor (BDNF) expression, alongside related neurotrophic signaling. Because it lacks ACTH's hormonal activity, the research focus is on CNS-signaling pathways. The work is preclinical and does not demonstrate outcomes in people.

How is Semax different from Selank?

Both are Pro-Gly-Pro-stabilized heptapeptide analogs, but Semax (from an ACTH fragment) is studied for neurotrophic/BDNF activity, while Selank (from tuftsin) is studied for GABAergic signaling. They act on different pathways and are studied as complementary research tools.

Compound Profile3 min readUpdated May 27, 2026

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What is Semax?
What does the research literature study?
How it relates to Selank
Handling and storage
Sources and further reading

Semax: Compound Profile

Semax is the neurotrophic member of the nootropic-neuropeptide class, the counterpart to the regulatory-leaning Selank. This profile covers its identity, the mechanism the literature attributes to it, and how it relates to Selank. For the class, see the neuropeptides overview.

What is Semax?#

Semax is a synthetic peptide modeled on the 4-10 fragment of adrenocorticotropic hormone (ACTH), with a Pro-Gly-Pro tripeptide added at the C-terminus. That extension increases stability and the analog lacks the corticotropic (hormonal) activity of the parent, so it acts purely as a neuropeptide. It was developed in Russia and is studied as a neuroprotective and neurotrophic agent.

Attribute	Value
Common name	Semax
Class	Synthetic ACTH(4-10) analog; heptapeptide
Sequence	Met-Glu-His-Phe-Pro-Gly-Pro (MEHFPGP)
CAS number	80714-61-0
Stabilizing feature	C-terminal Pro-Gly-Pro extension
Primary study area	Neurotrophic and neuroprotective research (BDNF pathway)

Semax molecular identity, as commonly reported in the literature and chemical databases.

Two-dimensional structure of Semax, a ACTH(4-10) heptapeptide with a Pro-Gly-Pro extension. Surgical-green heteroatoms (N, O) over a white skeleton on a dark background. — Semax · ACTH(4-10) heptapeptide with a Pro-Gly-Pro extension · structure rendered from PubChem CID 9811102 via RDKit.

What does the research literature study?#

Semax is studied as a neurotrophic and neuroprotective agent. The most frequently cited reported mechanism is upregulation of brain-derived neurotrophic factor (BDNF) expression, alongside related neurotrophic signaling. Because it lacks the hormonal activity of its ACTH parent, the research focus is on these CNS-signaling pathways rather than endocrine effects. This is preclinical and pharmacology research; it does not establish cognitive or other outcomes in people.

How it relates to Selank#

Semax leans neurotrophic; Selank leans regulatory (GABAergic signaling). The two share a Pro-Gly-Pro-stabilized design but act on different pathways, which is why the literature studies them as a complementary pair. The full breakdown is in Semax vs Selank.

Handling and storage#

Semax ships lyophilized and is dissolved prior to use. As a short stabilized peptide it is reasonably robust, but storage is standard across the catalog: the reconstitution primer covers solvent choice, and the cold-chain article covers stability once reconstituted.

Nexara catalogs Semax (10mg) at ≥99% purity for laboratory research. Independent third-party COA delivery is paused during the transition to a new testing laboratory; see research compliance.

Frequently asked

What is Semax?: Semax is a synthetic heptapeptide analog of the ACTH(4-10) fragment (sequence MEHFPGP), stabilized with a C-terminal Pro-Gly-Pro extension and lacking the parent's hormonal activity. Research studies it as a neurotrophic and neuroprotective agent. It is a laboratory research compound and is not for human use.
What is the reported mechanism of Semax?: The most-cited mechanism in the literature is upregulation of brain-derived neurotrophic factor (BDNF) expression, alongside related neurotrophic signaling. Because it lacks ACTH's hormonal activity, the research focus is on CNS-signaling pathways. The work is preclinical and does not demonstrate outcomes in people.
How is Semax different from Selank?: Both are Pro-Gly-Pro-stabilized heptapeptide analogs, but Semax (from an ACTH fragment) is studied for neurotrophic/BDNF activity, while Selank (from tuftsin) is studied for GABAergic signaling. They act on different pathways and are studied as complementary research tools.

Sources and further reading#

Semax (ACTH 4-10 analog) increases BDNF protein in rat basal forebrain (PMID 16635254): primary study of the Semax–BDNF mechanism.
Neurotrophin gene expression in rat brain under Semax (PMID 17353092): Semax effects on BDNF and trkB expression.

For research use only. Not for human consumption, diagnosis, treatment, or prevention of any disease. All products are intended solely for laboratory research purposes.

Last updated: 2026-05-27