Semax vs Selank: Evidence, Differences and Which One the HHS Policy Covers

Semax and selank are both seven-amino-acid peptides from the same Russian research network, both sold online as nasal sprays, and often sold together. They are not interchangeable. Semax is an analog of a fragment of the hormone ACTH and is studied mainly for stroke and other brain injury^[2][9]. Selank is an analog of tuftsin, a naturally occurring peptide, and is studied mainly as an anti-anxiety drug^[4][5][7]. The evidence for both is small and mostly Russian. As of October 28, 2026 they also differ in US status. Under a draft HHS enforcement policy announced that day, HHS says it does not intend to take action against 503A pharmacies that compound six peptides under ten conditions: semax is one of the six, for intranasal use only; selank is not on the list^[1]. The policy is not final and is not binding on HHS or the public, and comments are open until November 13, 2026^[14]. Neither is FDA-approved. This article compares what each is, what the human studies show, and what the policy means for buyers.

Semax vs selank at a glance

Where they come from

Both come from the same Moscow research network: N.F. Myasoedov of the Institute of Molecular Genetics, Russian Academy of Sciences, is an author on core papers for each^[2][4][6]. Both share the same design idea: a short active peptide with a Pro-Gly-Pro tail at the end. Semax starts from Met-Glu-His-Phe, a fragment of ACTH, the pituitary hormone that drives cortisol release; its developers describe it as an ACTH(4-10) analog^[2]. Selank starts from Thr-Lys-Pro-Arg, the sequence of tuftsin, an endogenous peptide^[4][5].

What the evidence says about each

Semax: brain injury studies

In rats, a single dose of semax raised BDNF (brain-derived neurotrophic factor) and its receptor trkB in the hippocampus^[3]. In people, the studies are in patients with brain or nerve disease. A Russian study of 110 patients after ischemic stroke found semax raised plasma BDNF and was linked to faster, better recovery on the Barthel daily-function index; the abstract does not describe randomization or blinding^[9]. An open-label study of 27 patients with motor neuron disease found intranasal semax did not change nerve damage or clinical scores but improved quality of life through mood and motivation^[10]. None of these tested semax as a focus or memory aid in healthy people.

Selank: anxiety studies

In rat brain membranes, selank acted as a positive allosteric modulator of GABA binding, the same receptor system benzodiazepines act on, though its binding site appears different^[4]. A rat study found selank and GABA changed the expression of many of the same neurotransmission genes^[6]. In people, a Russian study of 60 patients with anxiety, phobic and somatoform disorders compared selank with phenazepam (a benzodiazepine used in Russia) and reported “pronounced anxiolytic and mild nootropic effects” of selank, with the effect lasting a week after the last dose^[7]. A second study gave 30 patients phenazepam alone and 40 patients phenazepam plus selank; the combination reached its effect sooner on the rating scale and had fewer phenazepam side effects such as memory problems and sedation^[8]. The abstracts do not report placebo groups.

The one study that tested both

The only head-to-head we found is a brain-imaging study, not a clinical trial. Russian researchers gave 52 healthy participants semax, selank or placebo and ran resting-state fMRI before and 5 and 20 minutes after. They reported general and specific effects of each peptide on connectivity between the right amygdala, a region tied to anxiety, and the right temporal cortex^[11]. That shows both peptides change brain activity on a scan within minutes. It does not show which one helps anxiety, focus or memory more, because those outcomes were not measured.

Which one the draft HHS policy covers, and why it matters

The draft HHS policy announced October 28, 2026 lists six peptides in Appendix A: BPC-157, epitalon, KPV, MOTS-c, semax and TB-500^[1]. Selank is not one of them. In practice that means:

• Semax can be compounded by a State-licensed 503A pharmacy, a Federal facility or a licensed physician without HHS enforcement action, as semax free base for intranasal use, under ten conditions including a patient-specific prescription, a tested bulk source and FDA MedWatch reporting^[1]. Injectable semax is not covered. Condition 9 names a 510(k)-cleared syringe as the only device that may come with the product and does not mention nasal spray pumps, so ask the pharmacy how its spray fits that condition. Details are in our semax nasal spray article.
• Selank gets none of that. The policy does not address it, so a pharmacy compounding selank has no enforcement-discretion cover from this policy.
• Semax and selank combination sprays are excluded twice over: condition 7 allows only a single active ingredient listed in Appendix A, and selank is not listed^[1].

The policy is a draft, and it is not approval. It states that compounded drugs are not FDA-approved and that FDA does not review their safety, effectiveness or quality before marketing^[1]. The full list of conditions and the other five peptides are in the HHS 503A peptide policy explained, with the announcement covered in our news report.

Safety: what is known for each

For semax, HHS says the intranasal human record compiled by CDER covers several hundred subjects with no reported adverse outcome^[1]. For selank, the anxiety studies reported it was tolerated and reduced phenazepam's side effects when added to it^[8]. In both cases the record is short courses in small Russian patient groups, which is not enough to rule out uncommon or long-term effects.

Product quality is a shared and better-documented risk. Belgian regulators analyzed two unknown preparations seized in 2017 and 2018 and found semax and selank, and noted that these nootropic research peptides were sold freely online as injectable powders and nasal sprays^[12]. A research-use-only bottle has no prescription, no required testing and no adverse-event reporting behind it. See our guide on whether peptides are legal for what “research use only” means.

Is there a semax and selank dosage chart?

No validated one. Charts that circulate online are not drawn from trials in healthy people. The Russian semax studies used set courses in sick patients, for example 12 mg a day of a 1% intranasal solution in two 10-day courses for motor neuron disease^[10]. For selank, the human abstracts we reviewed do not report doses, and the animal work compared routes in mice rather than setting a human dose^[13]. None of that converts into a dose for a healthy adult, and combining the two has not been studied. Under the HHS policy, the strength and schedule of a compounded semax spray are set by the prescriber; selank has no compounded route under the policy. Our semax dosage page covers this in more detail.

Bottom line

Semax and selank are related Russian heptapeptides with different starting points: semax from ACTH, studied in brain injury; selank from tuftsin, studied in anxiety. Each has a small, mostly Russian human literature and no large placebo-controlled trial elsewhere, and the only direct comparison measured brain scans rather than symptoms^[11]. The practical difference in the US is now regulatory: semax can be compounded as a single-ingredient nasal product under the HHS conditions, and selank cannot^[1]. Our semax provider page lists every seller we confirmed sells semax as a single-ingredient product, shows the form each one sells, and labels injectable semax as a form the policy does not cover; semax-selank blends are left off. A listing does not confirm that the pharmacy meets the policy's other conditions, so check them yourself with the checklist in our semax nasal spray article: a certificate of analysis, a single active ingredient, the label line, the intranasal route, the device, and a State-licensed 503A pharmacy. For the other peptides on the HHS list, see the peptide guides, including KPV and TB-500.