Semax vs Selank: Same Laboratory, Same Pro-Gly-Pro Tail, and Neither Has a Placebo-Controlled Patient Trial

Two peptides, one laboratory, one stabilising tail. Neither has a placebo-controlled patient trial, so this page cannot rank them on efficacy. The trade-off it resolves instead is regulatory attention against verification difficulty, and on both they separate cleanly.

Both sit in the cognitive and neuroprotective peptides category, with individual records in Semax: FDA's own reviewers said no, and the advisory committee voted yes anyway and Selank: a registered anxiolytic that has never been compared to a placebo.

What is the actual difference between Semax and Selank?

Semax and Selank are two products of one design idea: take a short natural peptide and attach a Pro-Gly-Pro tail at the C-terminus to slow enzymatic degradation. The parents differ entirely. Semax is built from ACTH(4-7) and weighs 813.93 g/mol; Selank is built from tuftsin, an immunoglobulin G fragment, and weighs 751.9. Both are registered in Russia — Semax as a nootropic, Selank as an over-the-counter anxiolytic — and nowhere else.

The first four rows are the reason to run this comparison at all. Everything below them is a like-for-like property, and on most of those properties the two compounds are close to identical: same institute, same design principle, same registration holder, same country, same absence of human pharmacokinetics, same absence of a legal US compounding route.

Both came out of the Institute of Molecular Genetics of the Russian Academy of Sciences, Selank in cooperation with the Zakusov Scientific Research Institute of Pharmacology. Filatova and colleagues, writing in Frontiers in Pharmacology in 2017, state the origin plainly: Selank "is a synthetic analog of the natural immunopeptide taftsin... and was developed at the Institute of Molecular Genetics of the Russian Academy of Sciences, in cooperation with the Zakusov Scientific Research Institute of Pharmacology." FDA traces Semax's original synthesis to Ponomareva-Stepnaya et al., 1984.

One correction that applies to Semax and not to Selank. Semax is built from ACTH(4-7) — amino acids 4 through 7 of adrenocorticotropic hormone — but it is not an ACTH analogue in any functional sense: the fragment has no corticotropic activity and does not stimulate cortisol. Vendor copy describing it as a form of ACTH is wrong about mechanism before it is wrong about anything else. Selank's parent is an immunopeptide rather than a neuropeptide, which is why its early literature runs through cytokines rather than cognition.

Which has better evidence, and can either be ranked above the other?

Neither, and no. Semax has five human studies and Selank four, and zero randomised placebo-controlled trials in patients exist for either compound. Semax's foundational stroke work compared 30 patients against 80 conventional-therapy controls without randomisation or blinding and published no p-values; Selank's four anxiety trials all used a benzodiazepine comparator with no placebo arm and published no effect sizes. The two evidence bases fail in the same way, which is why this page does not rank them on efficacy.

This is cross-trial comparison and not head to head, with one partial exception. The Panikratova fMRI study is the only published work that put both compounds and a placebo in the same experiment, and it measured resting-state functional connectivity in healthy volunteers rather than symptoms in patients — a surrogate endpoint in people with nothing wrong with them. Everything else in that table compares different populations, different diseases, different endpoints and different journals. Every Selank trial appeared in Zhurnal Nevrologii i Psikhiatrii imeni S.S. Korsakova; every Semax patient trial was conducted in Russia and published in Russian.

Read Semax's 1997 study carefully, because it is the foundation of the entire stroke claim. Thirty patients received Semax and eighty received conventional therapy, patients were not randomised between those groups and nobody was blinded, and the reported outcome is a qualitative statement with no numbers and no p-values in the abstract. The 2007 motor neurone disease trial is the only Semax study carrying the randomised-controlled-trial tag, and its primary result is null. A null primary with a positive quality-of-life secondary is a hypothesis, not a finding.

Read Selank's 2008 Zozulya study the same way. The anxiolytic effects of Selank and medazepam were similar, with no placebo group, no stated non-inferiority margin and no power calculation in the abstract. In an anxiety trial, where placebo response rates routinely run 30–40%, "similar to an active drug" in 62 patients is not a demonstration of efficacy — it is a demonstration that two groups of about thirty people improved.

The most interesting Selank result is the one least often quoted, and it is not what the marketing says. The 2015 study is an add-on design: everyone received phenazepam, and the Selank group received Selank on top. The reported benefit is that the combination reduced the benzodiazepine's side effects, with less attention and memory impairment and less sedation. That is a plausible and useful result, and structurally it is a finding about phenazepam.

What is missing from both evidence bases?

The same four things are missing from both, and each is verifiable by absence. Neither compound has a placebo-controlled patient trial, neither has any human pharmacokinetic study, neither has a trial run outside Russia or by a non-Russian institution, and neither appears on any public trial registry. ClinicalTrials.gov returns zero Semax studies and no genuine Selank study, and the EU Clinical Trials Register returns zero for both.

The pharmacokinetic gap is the one that should change how vendor copy reads on both compounds. FDA states the Semax position without hedging: "We were not able to find pharmacokinetic studies in humans following exposure to semax (free base) or semax acetate via any route of administration." No human half-life, no human bioavailability, no human measurement of brain penetration by any route. For Selank the position is identical — a PubMed search for Selank pharmacokinetics returns five results, none of them human, so there is no published plasma half-life, no bioavailability figure and no measurement of how much of an intranasal dose reaches the brain.

Semax has one thing here Selank does not, and it is rodent data rather than human data. Shevchenko et al. 2006 gave tritium-labelled Semax intranasally to rats at 50 µg/kg and found "0.093% of the total introduced radioactivity per gram can be found in the rat brain 2 min after the administration, 80% of this radioactivity belonged to Semax." FDA's own summary puts rodent intranasal brain uptake at approximately 0.072% of the administered dose with a brain-to-blood ratio of 0.67, against 0.005% and a ratio of 0.24 for intravenous dosing — roughly a thirteen-fold advantage for the nasal route, which is the pharmacological reason the intranasal peptide guide exists for this pair. Both figures are still a fraction of one per cent, in a rodent, and the peptide degrades fast: the tripeptide proline-glycine-proline was the main metabolite identified in blood and brain.

Any percentage either compound's marketing quotes for blood-brain-barrier crossing in humans is extrapolated from rats or invented. That statement holds for both, and it is the single most commonly repeated false claim across the pair.

Which one has had regulatory attention, and what did it find?

Semax has had extensive FDA attention and Selank has had none. FDA's reviewers published a briefing document in May 2026 concluding there is "insufficient evidence of effectiveness" for Semax, and its Pharmacy Compounding Advisory Committee then voted 8–5, with one abstention, on 24 July 2026 to recommend listing it anyway. Selank has never been evaluated by that committee at all — it appears in FDA's Semax briefing material only to be excluded from scope as "a different peptide."

FDA's briefing document rested on four grounds, and only one of them was efficacy.

An advisory vote is not an agency action. As one legal analysis of the meeting put it, "an advisory committee vote is not an agency action, and FDA officials will have to make an ultimate decision on whether to accept or reject those recommendations." Semax today is exactly what it was before the meeting. FDA published no minutes or transcript for that meeting, so the 8–5 tally comes from published meeting coverage rather than an agency document — a hedge worth carrying, because the vote is the single most-cited fact about this compound.

The split matters for a reason beyond procedure. It maps precisely onto what the evidence base looks like when you open it: enough material for experienced people to form a favourable impression, and not enough for a regulator to write down a finding of effectiveness. Both readings are defensible from the same file, which is itself a statement about the file.

Selank's position is not better than Semax's — it is unexamined. Nobody has read Selank's dossier and reached either conclusion. A compound that has never been evaluated has no regulatory finding in its favour, and treating silence as endorsement is the error this row of the comparison exists to prevent. For context on how the same committee treats the wider group, Epithalon was reviewed at the same July 2026 meeting and recommended 7–5, and our bioregulators and the Khavinson peptides article covers that cluster.

What is each one registered to treat, and at what dose?

They are registered for different things, in different formats, under different ATC codes. Semax is a 0.1% and 1% nasal drop under ATC N06BX, on Russia's ЖНВЛП list of Vital and Essential Medicines, dosed at 2–3 drops per nostril two to four times daily for 7–30 days. Selank is a 0.15% nasal drop in a 3 mL bottle under ATC N05BX, "other anxiolytics," dispensed without prescription at two drops per nostril three times daily in 14-day courses.

Note the gap between Semax's label and Semax's literature. The 1997 stroke study used 12 mg/day in moderate stroke and 18 mg/day in severe; the 2018 study used 6000 µg/day. Those are hospital protocols, not the over-the-counter drop regimen, and the two are routinely conflated in dosing guidance written for the research market. Selank has no equivalent gap, because nothing in its published literature tests anything other than the registered course — and nothing tests what happens after a course ends, because every trial ran inside that window.

Peptogen was founded in 2005 with the participation of the Institute of Molecular Genetics, the institute that invented both molecules. We could not verify the original year of first registration for either compound. The state register carries only the current, re-issued certificates, and the years circulating online are not traceable to a primary source, so we are not printing one.

Converting between a percentage solution and a vial labelled in milligrams depends entirely on the volume you reconstitute into. The peptide dosing calculator and the reconstitution calculator will do that arithmetic; neither can supply the pharmacokinetics that would make the answer meaningful, because no human pharmacokinetic study exists for either compound. Reduce or stop a course if adverse effects appear, since no controlled safety study exists to tell you what is expected and what is not.

Which is harder to verify, and what does the platform data show?

Semax is harder to verify, and the reason is specific. Semax is sold alongside N-Acetyl Semax Amidate, a modified derivative with a different mass, and an HPLC purity figure cannot tell you which molecule is in the vial — a pure sample of the wrong compound produces a beautiful chromatogram. Selank's realistic failures are tuftsin at roughly 500 Da or a truncated synthesis, both of which mass spectrometry catches trivially at 751.9. Confusing the two with each other is not the realistic failure.

The Purity Index records Selank at 99.63% average HPLC purity across 285 independent lab tests from Vanguard, BTLabs, Horizon Analytical, Kovera, Ethos Analytics, ILS and MZ Biolabs, and Semax at 99.44% across 269 independent tests, each across 227 verified shops (verified August 2026). Both are strong purity results on large denominators. The weaker axis on both compounds is quantity.

Semax price data and Selank price data were both verified August 2026. Those figures exclude shipping, taxes and customs, coupon codes, bulk tiers, multi-vial kits and account-gated pricing. Both sit inside a platform total of 11,852 independent lab tests across 118 peptides and 530 shops, with 1,283 community reviews (verified August 2026), with community reviews and independently verified HPLC purity weighted equally at 50% each.

On price, the two compounds are close enough that cost is not a decision axis here. A $4.09 against $4.50 median, on compounds with identical evidence structures, is noise. Vial size drives most of the spread on both, so compare inside a band rather than across sizes. A 28.6% overage is not a bonus — it is direct evidence that fill accuracy is uncontrolled at that vendor, and the same process that overfills one vial underfills another, which is the mechanism explained in why 10 mg isn't 10 mg.

Three documentary traps sit around this pair and none of them is in the vial. PubChem's record title for CID 9811102 is not "Semax" — it reads "ACTH (4-7), Pro-Gly-Pro-", so anyone verifying a certificate against PubChem should expect that rather than treat it as a mismatch. ChemicalBook's Selank entry lists "PL14736" as a synonym, and PL14736 is BPC-157, an entirely different peptide, so that database cannot be used as a synonym source here. And Sigma-Aldrich supplies Semax research material as a TFA salt while quoting molecular weight on a free-base basis, which changes what your scale reads without changing the peptide (TFA versus acetate versus amidate salt forms).

One screening test applies to the surrounding content rather than the vial. Articles on both compounds routinely quote "Elena Yaroslavtseva" of the Institute of Molecular Genetics, and no such researcher exists — a PubMed author search under that surname returns five records covering an HIV cohort in St Petersburg, insect pathogenic fungi and 1976 bacteriophage genetics, none connected to peptides or this institute. The real programme is easy to trace: Nikolay F. Myasoedov and Lyudmila A. Andreeva, of the Department of Chemistry of Physiologically Active Compounds at the Institute of Molecular Genetics RAS, run through nearly every paper on both compounds, with Konstantin V. Shevchenko and Igor A. Grivennikov on the Semax pharmacokinetics, Evgeny I. Gusev and Veronika I. Skvortsova on the stroke studies, and Aleksandr A. Zozulya, G.G. Neznamov, Sergey B. Seredenin and Vladimir E. Medvedev on the Selank anxiety programme. Content that invents an expert is rarely accurate about anything else.

Compare vendors on the Semax compound page and the Selank compound page, see where to buy Selank and Semax for the seven checks specific to this pair, and read mass spectrometry for peptides and how to read peptide lab test results for what a certificate establishes line by line.

Are Semax and Selank legal, and are they banned in sport?

Both are registered medicines in Russia, both are unapproved new drugs in the United States, and neither has a legal US compounding route. Neither has a USP monograph and neither is a component of an FDA-approved drug, so neither satisfies any of the three statutory routes for a bulk substance in 503A compounding. Neither is named on the 2026 WADA Prohibited List, and whether the catch-all S0 clause reaches them is genuinely unresolved, because S0 turns on approval and both hold a Russian one.

On FDA's compounding page, current 22 April 2026, neither compound is among the fourteen substances in the active Category 2 group — cesium chloride, chloral hydrate, diethylstilbestrol, domperidone, edetate disodium, germanium sesquioxide, GHRP-2, GHRP-6, ibutamoren mesylate, ipamorelin acetate, kisspeptin-10, neomycin sulfate, quinacrine hydrochloride and tranilast. Both appear instead under "Bulk drug substances nominated but withdrawn." Semax's two nominations came from Wells Pharmacy Network and LDT Health Solutions, and FDA's note reads: "The nominations were withdrawn and FDA is evaluating the substances at its discretion."

Being off that list is a procedural fact about who withdrew what, not a safety clearance, and the claim that either compound is currently FDA-listed as a safety risk is outdated rather than true. See compounding pharmacy versus research peptide for what each supply route carries, and our FDA peptide regulation timeline for how these lists have moved.

On sport, do not overstate either compound. Neither "Semax" nor "Selank" nor "tuftsin" appears anywhere in the 2026 Prohibited List, effective 1 January 2026. Semax is not a corticotrophin — it has no corticotropic activity — so S2.2.2, which covers "corticotrophins and their releasing factors, e.g. corticorelin and tetracosactide," does not fit it. The catch-all S0 prohibits substances with "no current approval by any governmental regulatory health authority for human therapeutic use," and both hold exactly such an approval from Russia, which on the literal wording places them outside it. Whether an anti-doping tribunal would read it that way is a different question, and no published WADA, ITA or USADA determination exists either way. Seek a ruling before competing rather than assuming one. Anyone who tells you confidently that either is banned, or that either is cleared, is going beyond the documents.

So which should you choose?

Choose on what you can verify and what each is registered for, because efficacy will not separate them. Selank is registered as an over-the-counter anxiolytic and is the easier of the two to confirm in a vial. Semax is registered as a nootropic on Russia's Vital and Essential Medicines list, has the larger literature, and is the only one of the pair with a regulatory review — which concluded the evidence of effectiveness was insufficient before a committee recommended listing it 8–5 anyway.

The honest summary is that the choice is not between two efficacy profiles. It is between two registered indications, two verification problems and one regulatory file. If the reason for interest is anxiety, Selank is the one registered for it and the easier one to confirm. If the reason is cognitive or post-stroke, Semax is the one registered for it, and the price of that larger file is that a regulator has now read it and written down what it does not contain.

The trial that would settle this

The same trial would settle both compounds, and neither has any part of it. It needs a randomised, blinded placebo arm, a diagnosed patient population outside Russia, a pre-registered primary endpoint with an effect size and a confidence interval, a duration beyond a single registered course, and any human pharmacokinetic study at all. Zero Semax trials and zero Selank trials appear on any public registry, so even the registration element is unmet.

The last row is the one this page would most like to cite. The Panikratova study put Selank, Semax and placebo in one design and measured functional connectivity in people who were well. Running the same three-arm structure in patients, with a symptom endpoint, would answer the comparison in a single trial. Nobody has done it, and none of this is exotic — it is the standard package for a minor anxiolytic and a minor nootropic, and forty years after the molecules were made, nobody has run it for either.

Frequently Asked Questions

Is Semax better than Selank?

Neither can be ranked above the other on efficacy, because neither has a placebo-controlled trial in patients. Semax has five human studies and Selank four, and every Selank trial used a benzodiazepine comparator while every Semax patient trial was unblinded or null on its primary endpoint. They differ on what they are registered to treat, on how hard they are to verify, and on whether a regulator has read the file.

What is the difference between Semax and Selank chemically?

Both are heptapeptides built by attaching a Pro-Gly-Pro tail to a different parent. Semax is Met-Glu-His-Phe-Pro-Gly-Pro at 813.93 g/mol, built from ACTH(4-7). Selank is Thr-Lys-Pro-Arg-Pro-Gly-Pro at 751.9 g/mol, built from tuftsin, a natural immunopeptide from the heavy chain of human immunoglobulin G. That 62-dalton gap is easy for any mass spectrometer to resolve.

Did FDA approve Semax?

No. FDA's own reviewers concluded in a May 2026 briefing document that there is "insufficient evidence of effectiveness" and that the evaluation criteria weigh against listing it. The Pharmacy Compounding Advisory Committee then voted 8–5, with one abstention, on 24 July 2026 to recommend adding it, which is a non-binding recommendation from an outside committee. FDA has not issued a decision, and Semax remains an unapproved new drug.

Why has Selank never been evaluated by FDA?

Its nomination for the compounding list was withdrawn by the nominator before evaluation, so it sits in FDA's "nominated but withdrawn" table rather than the active Category 2 group. It appears in FDA's Semax briefing material only to be excluded from scope as "a different peptide." An absence of evaluation is not a clearance and should not be read as one.

Which one is harder to fake or substitute?

Semax. It is sold alongside N-Acetyl Semax Amidate, a modified derivative with a different mass that an HPLC purity figure cannot distinguish from it, so a batch-matched mass spectrometry result against 813.93 Da is the only check that settles identity. Selank's realistic substitutions are tuftsin at roughly 500 Da or a truncated synthesis, both of which are trivially visible at 751.9 Da.

Can I take Semax and Selank together?

No published trial has tested the combination in patients. The only study that put both compounds in one experiment was a 52-person resting-state fMRI study in healthy volunteers, which measured brain connectivity rather than symptoms and stated neither randomisation nor blinding. There is no human pharmacokinetic data for either compound alone, let alone together.

Where this leaves the pair

Semax and Selank are the same idea executed twice, and the comparison ends in an unusual place: the evidence cannot separate them, so everything else has to. One institute attached one stabilising tail to two different parent peptides, registered both in one country, and produced two files with identical shapes — real provenance, real registrations, small trials with the wrong control group, and no human pharmacokinetics.

What does separate them is not pharmacology. Semax is registered for cognitive and post-stroke indications and sits on Russia's Vital and Essential Medicines list; Selank is registered as an over-the-counter anxiolytic. Semax is the harder of the two to confirm in a vial, because its derivative is sold beside it and purity testing is blind to the difference. And Semax is the only one of the pair whose file a regulator has actually opened.

That last difference is the one most likely to be read backwards. An 8–5 advisory recommendation is not an approval, was made against the written assessment of FDA's own reviewers, and comes to us through published meeting coverage rather than an agency transcript. Nothing about Semax's effectiveness changed in July 2026 — only the opinion of thirteen people about what to do while the evidence is missing. And nothing about Selank's effectiveness has been assessed at all.

Browse the cognitive and neuroprotective peptides category, or our complete peptide guide with 118 compounds (verified August 2026). For per-dose volume when reconstituting a vial, use the peptide dosing calculator alongside the reconstitution calculator. Compare shops through independent lab tests and community-verified shop reviews.

This article is for educational and informational purposes only and does not constitute medical advice. Peptides discussed may be investigational compounds not approved by the FDA (or equivalent regulators in your jurisdiction) for human use. Always consult a qualified healthcare provider before using any peptide or research compound. Peptigrity is an independent review platform and does not sell, endorse, or recommend specific products or vendors.