Selank vs. Semax: Two Russian Neuropeptides in Research

Both are seven amino acids long, both end in the same three residues, and both came out of Russian labs. After that, they have little in common.

Selank and Semax get grouped together because they share a design trick. Each takes a short natural peptide and adds a Pro-Gly-Pro tail to slow its breakdown. Selank starts from tuftsin, a small immune-related peptide. Semax starts from a fragment of ACTH, the pituitary stress hormone, with the hormonal activity engineered out. Nearly all human research on both is small, open-label, and published in Russian, and neither is approved by the FDA. Here’s how they compare.

Table of Contents

• Selank and Semax at a Glance
• Selank: A Tuftsin Analogue
• Semax: An ACTH(4-10) Analogue
• How Strong Is the Evidence?
• US Regulatory Status
• FAQs About Selank and Semax

Selank and Semax at a Glance

Selank: A Tuftsin Analogue

Tuftsin is a naturally occurring four-amino-acid peptide (Thr-Lys-Pro-Arg) with immune-modulating activity. Selank keeps that sequence and adds Pro-Gly-Pro to the end, which makes it more resistant to the enzymes that would otherwise break it down quickly.

Published Selank research falls into a few groups.

The main human study compared Selank with a benzodiazepine in patients diagnosed with generalized anxiety disorder or neurasthenia (2008, Russian-language). Rodent work followed. A 2016 rat study looked at how Selank changed the expression of genes involved in GABA signaling in the frontal cortex (2016). Then a 2017 follow-up in cultured neuroblastoma cells found that Selank alone produced no direct change in that same gene set (2017).

That pair of results is a good example of how early this research is. A proposed mechanism showed up in one model and not in the next. A 2018 review lays out the leading hypotheses (2018), and most of them still rest on animal or cell data.

Semax: An ACTH(4-10) Analogue

ACTH is the pituitary hormone that signals the adrenal glands to release cortisol. Semax borrows a short stretch of it, positions 4 through 10, keeps the first four residues (Met-Glu-His-Phe), and replaces the rest with Pro-Gly-Pro. That swap removes the hormonal, cortisol-releasing activity and makes the peptide last longer.

Semax research leans on BDNF, short for brain-derived neurotrophic factor, a protein that supports the growth and survival of neurons. In rats, Semax raised BDNF levels and the activity of its receptor, TrkB, in the hippocampus (2003; 2006). Several gene-expression studies tracked how those changes unfolded over time (2007; 2008; 2010).

The human studies are clinical rather than mechanistic. They include open-label or non-randomized work in ischemic stroke (1997; 2018) and in optic nerve disease (2000).

How Strong Is the Evidence?

Not very, by the standards used for approved drugs.

The human studies for both peptides are small, ranging from a few dozen to around a hundred participants. Most are open-label or non-randomized, which means participants and researchers knew who received what. That design tends to inflate subjective outcomes like anxiety ratings. Nearly all were published in Russian-language journals, and we found no large, placebo-controlled randomized trial run in the US or Europe for either one.

The mechanism story has the same limits. Selank’s GABA link and Semax’s BDNF link come mostly from rodents and cultured cells. Human data on how much of either peptide reaches the brain are thin.

So a head-to-head question like “which one works better” has no answer in the literature. They were studied for different things, in different models, and never compared directly. Our overview of what peptide safety research shows covers why small open-label studies can’t settle safety questions either.

US Regulatory Status

Neither Selank nor Semax is an FDA-approved drug.

Both have appeared in FDA’s review of substances used in drug compounding, which is a separate process from approval. FDA’s page on bulk substances that may present significant safety risks lists Semax and Selank acetate among nominations that were withdrawn. A withdrawn nomination isn’t a safety clearance. Semax was also on the agenda for FDA’s July 2026 Pharmacy Compounding Advisory Committee meeting, so its status may change.

Research-grade Selank and Semax sit outside that process. They’re sold for laboratory work, where purity documentation carries the weight. Our guide to evaluating research peptide quality covers what a certificate of analysis should show.

FAQs About Selank and Semax

Are Selank and Semax the same thing?

No. They share a Pro-Gly-Pro tail and a Russian research history, but they come from different parent molecules. Selank is built on tuftsin, an immune-related peptide. Semax is built on a fragment of ACTH.

Why do both end in Pro-Gly-Pro?

The added tail makes each peptide more resistant to breakdown by enzymes. Semax’s version also replaces the part of the ACTH fragment responsible for hormonal activity.

Has either been tested in Western clinical trials?

We found no large, placebo-controlled randomized trial of either peptide conducted in the US or Europe. The published human studies are small and mostly Russian-language.

What is BDNF, and why does it come up with Semax?

BDNF is a protein that supports the growth and survival of neurons. Rat studies found Semax increased BDNF and the activity of its receptor in the hippocampus. That’s the basis for most discussion of Semax, and it hasn’t been confirmed in human studies.

How should Selank and Semax be stored?

Lyophilized powder keeps best cold and away from light. Check the product documentation and certificate of analysis for your specific vial. Our lab handling guide covers reconstitution and sterile technique.

All products are sold strictly for lawful laboratory research purposes only and are not for human or veterinary use or human consumption. This article summarizes published research for general information and is not a substitute for advice from your doctor. References: each study named above links to its record on PubMed, ClinicalTrials.gov, or FDA.gov.