Selank and Semax are synthetic neuropeptides developed at the Institute of Molecular Genetics of the Russian Academy of Sciences. Both have received regulatory approval in Russia for clinical indications including anxiety disorders (Selank) and cognitive impairment following ischaemic stroke (Semax). Outside Russia, they remain research compounds.
Selank
Selank is a heptapeptide analogue of tuftsin (Thr-Lys-Pro-Arg-Pro-Gly-Pro), with modifications conferring metabolic stability. Tuftsin itself modulates immune function and exhibits anxiolytic properties. Selank retains the anxiolytic profile while being resistant to rapid enzymatic degradation.
Preclinical studies have demonstrated Selank's ability to modulate GABA-A receptor activity and influence brain-derived neurotrophic factor (BDNF) expression. Unlike benzodiazepines, Selank does not appear to produce sedation, tolerance, or withdrawal in rodent models — a profile that has attracted interest for its potential as a non-sedating anxiolytic scaffold.
Human trials conducted in Russia showed reductions in anxiety scores (Hamilton Anxiety Scale) comparable to standard anxiolytic medications, with improved tolerability. The peptide is typically administered intranasally in clinical studies, with nasal absorption providing direct access to the olfactory-CNS pathway.
Semax
Semax is a synthetic analogue of ACTH(4-7) — a fragment of adrenocorticotropic hormone — with the sequence Met-Glu-His-Phe-Pro-Gly-Pro. It was developed specifically for neuroprotective and nootropic applications.
Research has focused on Semax's ability to upregulate BDNF, nerve growth factor (NGF), and other neurotrophins. In stroke models, early administration of Semax reduced infarct volume and improved behavioural recovery. The compound also modulates the dopamine system and has demonstrated pro-cognitive effects in rodent learning paradigms (Morris water maze, novel object recognition).
In a 2011 Russian clinical study of patients recovering from ischaemic stroke, Semax administration over 10 days was associated with improved neurological deficit scores and faster rehabilitation milestones compared to standard care.
Differences and Complementary Profiles
Selank's primary profile is anxiolytic and immune-modulatory. Semax's primary profile is nootropic and neuroprotective. They act on overlapping but distinct pathways — researchers sometimes describe Selank as reducing cognitive noise (anxiety, stress response) while Semax enhances signal (learning, neurotrophin expression). Both require intranasal or injectable administration; oral bioavailability is negligible due to peptide degradation in the GI tract.
Limitations of Available Data
Most human data comes from Russian-language publications with relatively small sample sizes and limited blinding rigour by Western standards. Larger, independently replicated trials are lacking. Mechanism work is largely rodent-based. Both peptides are well-tolerated in available studies, but long-term safety data in humans is limited.
- Selank: GABA-A modulation, BDNF upregulation, anxiolytic without sedation
- Semax: ACTH(4-7) analogue, neurotrophin expression, neuroprotection in stroke models
- Both approved in Russia; research compounds elsewhere
- Intranasal administration preferred for CNS delivery
For research purposes only. Not approved for human use outside the Russian Federation. Consult medical literature and qualified professionals.