Semax vs Selank: Two Russian Nasal Peptides, and Only One Is Now Covered

Semax and Selank are short synthetic peptides developed in Russia, both usually taken through the nose and often sold together online as nootropics. Semax is built on a fragment of the pituitary hormone ACTH and has been studied mostly in stroke recovery and brain imaging.^[1] Selank is built on tuftsin, a small immune peptide, and has been studied mostly in anxiety.^[2] Neither is approved by FDA. The difference that matters most in the US arrived on October 28, 2026: Semax free base, for intranasal use only, is one of six peptides in an HHS enforcement-discretion policy for 503A compounding pharmacies, and Selank is not.^[3] A combined Semax and Selank spray falls outside that policy because it contains two active ingredients.

Semax vs Selank at a glance

What each peptide is

Semax is a chain of seven amino acids. The HHS policy identifies the covered form as semax free base, sequence Met-Glu-His-Phe-Pro-Gly-Pro, molecular formula C37H51N9O10S and molecular weight 813.9 g/mol.^[3] Russian researchers describe it as an analog of the ACTH(4-10) fragment with nootropic properties, and in rodents it activates dopamine and serotonin systems in the brain.^[1]

Selank is also seven amino acids long: Thr-Lys-Pro-Arg-Pro-Gly-Pro. Its first four are tuftsin (Thr-Lys-Pro-Arg), and Russian pharmacologists have compared the two directly in rats.^[2] Tuftsin itself is studied mainly as an immune modulator.^[4] Selank’s anxiety research points to a different target. In experiments on brain-cell membranes, its developers reported that it acts on GABA receptors as a positive allosteric modulator,^[8] the receptor family that benzodiazepines also work through.^[9]

The two molecules share an ending. Both sequences finish in Pro-Gly-Pro, which places them in the family Russian researchers call glyprolines.^[10] They also share a research group. Nikolai Myasoedov of the Russian Academy of Sciences is an author on the semax rodent study,^[1] on both semax imaging studies,^[11][12] and on all three selank anxiety trials discussed below.^[13][14][6] Much of what is known about either peptide comes from the people who developed them.

What the human evidence shows for each

Semax: one stroke study and imaging

The largest human semax study we found is a 2018 study of 110 people recovering from ischemic stroke, run at Pirogov University in Moscow by a team outside the developer group. Patients were grouped by when rehabilitation began (about 89 or about 214 days after the stroke) and then by whether they received semax. Those given semax had higher blood levels of BDNF, a protein that supports nerve cells, and the authors reported faster and better recovery on the Barthel index, a scale of everyday functioning.^[5] The abstract does not describe randomization or blinding, and the full paper is in Russian.

The rest of the human semax record is brain imaging in healthy volunteers. In one study, 14 people given 1% semax through the nose and 10 given placebo had resting-state fMRI scans, which showed a larger frontal part of the brain’s default mode network in the semax group.^[12] No test of memory or attention was part of the design. Our page on semax brain imaging without an outcome covers the larger imaging study and its limits.

Russian clinicians are measured about it too. In July 2026 an expert council of the National Association of Pediatric Neurologists rated add-on drugs used for ADHD in Russia. It put semax in its group with “a limited evidence base,” below the one product backed by a double-blind randomized trial that met its primary endpoint.^[15]

Selank: three anxiety trials from Russia

Selank’s human record is a short run of anxiety trials. In 2008, 62 patients with generalized anxiety disorder or neurasthenia were given selank or the benzodiazepine medazepam, and the anxiety-reducing effects were reported as similar.^[13] Our review of that trial covers what its abstract can and cannot show.

Two later trials used another benzodiazepine, phenazepam, as the comparator. In 2014, 60 patients with phobic-anxiety and somatoform disorders received selank or phenazepam, and the authors reported that selank’s anxiety-reducing effect lasted for a week after the last dose.^[14] In 2015, 70 patients received phenazepam alone (30) or phenazepam plus selank (40). With selank added, phenazepam’s benefit showed up sooner on the Hamilton rating scale (HDRS) the authors used, and its side effects, including sedation and problems with attention and memory, were less marked.^[6]

All three trials came from overlapping Russian author teams, and we found no independent replication published elsewhere. A 2021 review in the Journal of Clinical Pharmacology grouped selank with phenibut as “poorly studied Russian drugs with GABAergic mechanisms” that are sold to US consumers as dietary supplements.^[9]

The one study that gave both

Only one study we found gave semax and selank to comparable groups. Fifty-two healthy participants received semax, selank or placebo and had brain scans before and 5 and 20 minutes after. The authors reported effects on connectivity between the right amygdala and the right temporal cortex, some shared by the two peptides and some specific to each.^[11] It measured brain activity and did not test anxiety, memory or any task. No trial has compared semax and selank as treatments for anything.

Semax’s largest human study is in stroke recovery and Selank’s is in anxiety. No trial has compared the two as treatments.

The US difference since October 28, 2026

On October 28, 2026, HHS said it does not intend to take enforcement action against a state-licensed pharmacy, federal facility or licensed physician that compounds one of six listed peptides under section 503A, provided every condition in the policy is met. The policy is interim. It lasts until each peptide is “addressed in a final rule” deciding whether it goes on the 503A bulks list, and HHS may revisit it if a safety or quality problem appears. It is not an approval, and the document itself says compounded drugs are not FDA-approved.^[3] It covers 503A pharmacies only, not the larger 503B outsourcing facilities.^[16] Our explainer on the HHS peptide compounding policy walks through all six peptides and every condition.

Semax is in, as an intranasal free base

Semax had been in FDA’s Category 2 from September 29, 2023 until April 22, 2026. FDA’s drug center recommended against listing it, and the agency’s Pharmacy Compounding Advisory Committee voted in favor. In explaining its decision, HHS called the safety concerns raised by FDA reviewers “mechanistic rather than observed” and said the intranasal human record covers several hundred subjects with no reported adverse outcome. It then limited the cover to semax free base “for intranasal use.”^[3] An injectable semax, or a molecule that does not match the identity in Appendix B (sequence, formula and molecular weight), is outside the policy. For the July 2026 committee votes and how semax compares with the other listed peptides, see are peptides legal.

Selank is not covered

Selank is not in Appendix A, so the policy gives a pharmacy no cover to compound it.^[3] It was not among the seven peptides FDA’s advisory committee reviewed in July 2026. On FDA’s safety-risk page it appears as selank acetate in the table of substances withdrawn from Category 2, with FDA’s note that compounded selank may pose a risk of immune reactions for some routes and that the agency lacks important information about its safety in humans.^[7] Selank sold online is therefore sold outside the compounding system, as a research chemical or, as the 2021 review found, as a dietary supplement.^[9]

Semax + Selank sprays are blends

Condition 7 of the HHS policy says the compounded product “contains only a single Active Pharmaceutical Ingredient (API) listed in Appendix A.” HHS gives the reason: with one ingredient per product, adverse events and outcomes can be traced to a specific substance.^[3] A combined Semax and Selank spray fails that condition twice, because it has two ingredients and one of them is not on the list. A blend of semax with another listed peptide would fail it as well. Our page on peptide blends and stacks covers the single-ingredient rule across the market.

Semax nasal spray: an open question about the device

The policy limits semax to intranasal use. A separate condition says “the only drug delivery device co-packaged or containing the compounded drug is an FDA 510(k)-cleared syringe,” because more complex devices add risk.^[3] The text does not say how a nasal product fits that wording. Until HHS or FDA clarifies it, a patient offered compounded semax can fairly ask the pharmacy what the product comes in and how it meets that condition.

The other conditions apply to semax as to every listed peptide:

• A valid patient-specific prescription, so a clinician has to decide that it is appropriate for you.^[3]
• Bulk semax from an FDA-registered facility, with a certificate of analysis covering identity, purity, potency and contaminants such as endotoxins and heavy metals.^[3]
• A label stating “This is a compounded drug product. Not for resale.”^[3]
• Serious adverse events and quality problems reported by the compounder to FDA’s MedWatch program, with the reporting procedure on the patient labeling.^[3]

Supply may be thin at first. The president of a central Florida compounding company told NPR, “We won’t be able to meet demand.”^[16] Our semax provider page tracks compounding sellers as they appear, and the semax profile collects what sellers say about it.

What research-market sprays are

Before October 2026 neither peptide had a compounding route, so Semax and Selank sold online came from research-chemical and supplement sellers. The policy does nothing for those products. HHS said its aim was to discourage research-use-only peptides from foreign manufacturers that pose a safety risk to US patients.^[3] Belgium’s public health laboratory, Sciensano, analyzed two suspicious preparations seized in 2017 and 2018 that turned out to contain Selank and Semax. Its online search found these peptides sold as freeze-dried powder for injection and in nasal sprays.^[17] A research-use-only vial or spray has no certificate requirement, no prescriber and no adverse-event reporting behind it. The difference is set out in research-use-only vs compounded peptides.

In the Russian studies, semax was given as nasal drops, at 0.1% in a 2026 eye-surgery study^[18] and at 1% in the imaging study.^[12] Those are the strengths the studies used. No US dose of either peptide is approved, and under the HHS policy the strength of a compounded semax product is set by the prescriber for one patient.

Safety: what is known and what is not

• No large safety trials. Neither peptide has been through the kind of trials FDA reviews before approval. FDA’s notes on both list a possible risk of immune reactions from aggregation and impurities, and say the agency lacks the safety information it needs.^[7]
• Bleeding. HHS mentioned bleeding and abuse-potential signals for semax and said they have no clinical counterpart in the human record.^[3] In laboratory clotting tests, selank showed the strongest anticoagulant effect of three related glyproline peptides.^[10] Anyone on a blood thinner should raise either peptide with the prescriber first.
• Anxiety medicines. In membrane experiments, selank blocked the modulating effect of diazepam at the GABA receptor.^[8] Whether that matters in people is unknown, which is a reason to tell the prescriber of any benzodiazepine before trying selank.
• Unknown contents. A research-market product may not contain what its label says, a problem separate from whether the molecule works.^[17]

To check where any other peptide stands, use our peptide status checker.