Semax vs Selank
Reviewed by the BestHealingPeptides Editorial Team ·
Semax and Selank are the two prototype Russian-developed research peptides for cognitive and behavioural applications — both developed by the Russian Institute of Molecular Genetics, both intranasally delivered short heptapeptides with C-terminal Pro-Gly-Pro stabilisation, both registered as prescription medicines in Russia but unlicensed in the UK. The principal differentiation is mechanism and intended pharmacology: Semax is primarily nootropic (BDNF/NGF upregulation, learning and memory effects); Selank is primarily anxiolytic (enkephalinase modulation, non-sedating anxiety reduction). The two are pharmacologically complementary rather than substitutes, and the canonical research-chemical-community protocol pairs them in combined intranasal use.
Semax
A 7-amino-acid synthetic heptapeptide analogue of adrenocorticotropic hormone (ACTH) fragment 4-10, developed by the Russian Institute of Molecular Genetics (Moscow) in the 1980s for nootropic and neuroprotective applications. Lacks the corticotropic activity of native ACTH while retaining the neurotropic effects on hippocampal BDNF and NGF expression. Registered as a prescription medicine in Russia and several CIS countries; not licensed in the UK or other Western jurisdictions.
Selank
A 7-amino-acid synthetic heptapeptide analogue of the immunomodulatory tetrapeptide tuftsin (TKPR), developed alongside Semax by the Russian Institute of Molecular Genetics in the 1990s. Distinguished from Semax by its principally anxiolytic rather than nootropic profile, with mechanism involving GABAergic and serotonergic modulation alongside enkephalinase inhibition. Registered as a prescription anxiolytic in Russia; unlicensed in the UK.
| Aspect | Semax | Selank |
|---|---|---|
| Origin peptide | ACTH 4-10 (MEHFRWG) | Tuftsin (TKPR) |
| Synthetic sequence | MEHFPGP | TKPRPGP |
| Principal mechanism | BDNF/NGF upregulation, melanocortin signalling | Enkephalinase inhibition, GABA/serotonin modulation |
| Primary pharmacology | Nootropic (cognitive enhancement) | Anxiolytic (non-sedating) |
| Russian indication | Stroke, cognitive impairment, paediatric ADHD | Generalised anxiety disorder |
| Functional effect duration | ~4-8 hours per intranasal dose | ~4-12 hours per intranasal dose |
| Combined protocol | Pairs with Selank for combined nootropic-anxiolytic effect | Pairs with Semax for combined nootropic-anxiolytic effect |
| UK status | Unlicensed; research-chemical | Unlicensed; research-chemical |
Shared design heritage — Russian Institute of Molecular Genetics
Both peptides emerged from the same Russian Institute of Molecular Genetics (Moscow) research programme in the 1980s-1990s exploring stable analogues of endogenous bioactive peptides. The shared design heritage explains the structural similarity — both are 7-amino-acid heptapeptides with C-terminal Pro-Gly-Pro tripeptide extensions that confer proteolytic stability through the same medicinal-chemistry strategy. Both are predominantly delivered intranasally to exploit the olfactory and trigeminal pathways that bypass the blood-brain barrier limitation of peripheral peptide administration. Both are registered as prescription medicines in Russia (Semax for stroke, cognitive impairment, and paediatric conditions; Selank for generalised anxiety disorder) but neither has progressed to FDA, EMA, or MHRA marketing authorisation. The two compounds represent the most-developed examples of the broader 'Russian nootropic peptide' research tradition that has produced multiple bioactive heptapeptides over the past 40 years.
Mechanism — distinct molecular pathways
Semax (ACTH 4-10 analogue, MEHFPGP) primarily upregulates hippocampal BDNF and NGF expression, with the molecular cascade involving melanocortin-receptor-mediated transcriptional effects (Semax retains MC4R activity but lacks the ACTH-receptor activation responsible for corticotropic effects), modulation of noradrenergic and dopaminergic systems, and downstream effects on hippocampal long-term potentiation. The pharmacological signature is principally nootropic — improvements in learning, memory, attention, and stress-resilience phenotypes. Selank (tuftsin analogue, TKPRPGP) primarily inhibits enkephalinase enzyme (neutral endopeptidase/neprilysin), raising central enkephalin tone with downstream µ-opioid system effects, plus modulation of GABA and serotonin systems and immunomodulatory effects reflecting the tuftsin ancestry. The pharmacological signature is principally anxiolytic — non-sedating anxiety reduction without the cognitive impairment or dependence of benzodiazepines. The two mechanisms are pharmacologically complementary and engage distinct molecular substrates.
Clinical and research evidence base
Semax has a broader Russian clinical-indication record: acute ischaemic stroke (foundational Gusev/Skvortsova clinical work), cognitive impairment in adults, and paediatric attention-deficit and learning-disability indications. The Russian clinical-use record spans 30+ years across multiple neurological and cognitive contexts. Selank has a focused Russian clinical-indication record centred on generalised anxiety disorder, with randomised controlled trials demonstrating non-inferiority versus benzodiazepine comparator medazepam and the favourable tolerability profile (no sedation, no cognitive impairment, no tolerance/dependence) that supports its registration as a non-benzodiazepine anxiolytic. Western pre-clinical research has produced supporting mechanism characterisation for both compounds but Western clinical-trial development has not been pursued for either.
Pharmacokinetics and dosing — both intranasal short-half-life
Both peptides share intranasal-delivery pharmacokinetics with short plasma half-lives (minutes) and longer functional effect duration through downstream pathway modulation. Semax intranasal dosing typically targets 50-450 µg/day divided 2-3 times daily (Russian-marketed 0.1% nasal drops product). Selank intranasal dosing typically targets 75-450 µg/day divided 2-3 times daily (Russian-marketed 0.15% nasal drops product). Functional effect duration is 4-8 hours for Semax and 4-12 hours for Selank — Selank's somewhat longer functional duration reflects the downstream enkephalin and monoamine system tone effects that persist beyond peptide presence. Both have established Russian clinical safety records supporting chronic dosing protocols.
Combined Semax + Selank protocol — the canonical pharmacological framework
The combined intranasal 'Semax + Selank' protocol has become the standard research-chemical-community framework for combined nootropic-anxiolytic pharmacology. The rationale is mechanistic complementarity: Semax addresses cognitive enhancement through BDNF/NGF upregulation; Selank addresses anxiety reduction through enkephalinase and GABA/serotonin modulation. The two mechanisms engage distinct molecular substrates with no documented adverse pharmacological interactions. Combined intranasal administration is straightforward — both peptides are typically reconstituted in compatible aqueous vehicles and can be co-administered in the same intranasal dosing schedule. The combined effect on subjective wellbeing, attention, and stress resilience is reported as superior to either monotherapy in research-community use, though formal Western RCT comparison of combined versus monotherapy has not been published. This combined-protocol framework parallels in spirit (though not in regulatory status) the canonical CJC-1295 + ipamorelin GH-axis protocol.
Verdict
Semax and Selank are mechanistically complementary Russian-developed heptapeptides with distinct primary pharmacology — Semax for nootropic cognitive enhancement, Selank for non-sedating anxiolysis. For research targeting the specific mechanism (BDNF/NGF for Semax, enkephalin/GABA for Selank), the choice is determined by the research question. For combined nootropic-anxiolytic research, the canonical Semax + Selank intranasal protocol exploits the mechanistic complementarity and is the dominant research-chemical-community framework. Neither is licensed in the UK; both are research-chemical-grade compounds in Western jurisdictions.
Where to source research peptides for laboratory research
The following UK-based suppliers stock research-grade, lyophilised peptides for in-vitro and pre-clinical work. Purity and provenance vary; always request a Certificate of Analysis (CoA) and confirm cold-chain storage on arrival. None of the products linked below are approved for human use.
- PeptideAuthority.co.uk
UK-based research peptide supplier with batch certificates of analysis and >99% purity testing.
- PeptideBarn.co.uk
Wide catalogue of research-grade lyophilised peptides shipped from the UK, including bulk vials.