Semax is an ACTH(4-7) analogue that upregulates BDNF and activates TRKB signalling, driving neuroprotective and cognitive effects; Selank is a synthetic tuftsin analogue with anxiolytic and immune-modulatory activity, also studied for cognitive effects through serotonin and dopamine system modulation.
Research reference only — all information on this page summarises peer-reviewed scientific literature and does not constitute medical advice. View full compound profiles: Semax · Selank
Mechanism Comparison
Semax (Met-Glu-His-Phe-Pro-Gly-Pro) is a heptapeptide analogue of ACTH(4-7) with added Pro-Gly-Pro stabilisation. It does not act at melanocortin receptors at standard research doses but instead stimulates BDNF and NGF expression in hippocampal and frontal cortex neurons, activating TRKB and TRKC signalling. Selank (Thr-Lys-Pro-Arg-Pro-Gly-Pro) is a synthetic analogue of the immunopeptide tuftsin, extended with Pro-Gly-Pro for stability. It modulates GABAergic tone (anxiolytic effect), upregulates serotonin metabolism, and has immune-modulatory activity through tuftsin receptor engagement.
Side-by-Side Attributes
| Attribute | Semax | Selank |
|---|---|---|
| Peptide origin | ACTH(4-7) analogue + Pro-Gly-Pro extension | Tuftsin (IgG fragment) analogue + Pro-Gly-Pro extension |
| Primary mechanism | BDNF/NGF upregulation; TRKB activation | GABAergic modulation; serotonin metabolism; tuftsin receptor |
| Primary research profile | Cognitive enhancement, neuroprotection, BDNF-mediated effects | Anxiolytic, stress-reduction, immune modulation |
| BDNF effect in research | Significant upregulation (key finding) | Modest; indirect |
| Anxiolytic effect | Present but secondary | Primary reported effect |
| Immune modulation | Indirect (via NGF/BDNF) | Direct (tuftsin receptor; NK cell activation) |
| Administration route in research | Intranasal; SC injection | Intranasal; SC injection |
| Half-life (approx.) | ~Several minutes (active metabolites longer-lived) | ~Several minutes (active metabolites longer-lived) |
| Regulatory status (Russia) | Approved as cognitive/cerebrovascular agent | Approved as anxiolytic agent |
Key Research Points
- 1Semax is the stronger candidate for BDNF-focused neuroprotection research: published data show significant BDNF and NGF upregulation in hippocampal and cortical tissue after intranasal administration in rodent models.
- 2Selank is the preferred tool for anxiolytic mechanism research: its GABAergic activity and serotonin metabolism modulation have been characterised in published anxiolytic dose-response studies, with a published clinical comparison to standard anxiolytics in Russian clinical research.
- 3Both peptides contain the Pro-Gly-Pro C-terminal extension that confers protease stability, extending effective CNS activity beyond what their short plasma half-lives would suggest.
- 4Both are approved pharmaceutical agents in Russia (Semax as a cerebrovascular/cognitive drug, Selank as an anxiolytic) — the Russian clinical literature provides clinical-context data not available for most other research peptides.
- 5Neither compound has completed Phase 3 trials under Western regulatory frameworks (FDA/EMA); their use in research outside Russia is investigational.
Frequently Asked Questions
What is the main difference between Semax and Selank?
Semax is an ACTH(4-7) analogue primarily studied for cognitive and neuroprotective effects via BDNF and NGF upregulation; it activates TRKB signalling and is used in research on neuroplasticity, stroke recovery, and cognitive impairment models. Selank is a tuftsin analogue primarily studied for anxiolytic effects via GABAergic and serotonergic modulation, with secondary immune-modulatory activity through tuftsin receptor engagement. In summary: Semax is more cognitive/neuroprotective; Selank is more anxiolytic/immunomodulatory.
Do Semax and Selank both increase BDNF?
Semax shows robust BDNF and NGF upregulation in published rodent research — this is considered its primary mechanistic output. Selank shows more modest and indirect BDNF effects; its primary mechanism is GABAergic and serotonergic modulation. Published studies comparing the two have found Semax to be the more potent BDNF stimulator, while Selank's neuroactive profile is better characterised through anxiolytic and immune-outcome measures.
Are Semax and Selank FDA-approved?
Neither Semax nor Selank is FDA-approved. Both are approved pharmaceutical agents in Russia (Semax as a cerebrovascular and cognitive agent; Selank as an anxiolytic), where their clinical use has generated a body of clinical research data. Outside Russia, both are classified as investigational peptides. Both are subject to 503A compounding restrictions in the United States as of mid-2026.
Deep Dive
For extended mechanism analysis, trial data, and regulatory context, see the full research article:
Semax vs Selank: Neuropeptide Research Comparison →Full compound profile
Semax
Full compound profile
Selank