Semax vs Selank: what is the difference?

Semax and Selank are often mentioned in the same breath. Both are synthetic heptapeptides, both were developed at the same Russian institute and both end in the same three amino acids. Yet they are derived from completely different parent peptides and are studied in different research models. This page explains the difference between Semax and Selank, what they have in common and how to handle them in the lab.

What is Semax?

The Semax peptide is a synthetic heptapeptide with the sequence Met-Glu-His-Phe-Pro-Gly-Pro. It is an analogue of the ACTH(4-10) fragment: the ACTH(4-7) sequence Met-Glu-His-Phe, extended at the C-terminus with Pro-Gly-Pro. Unlike the parent hormone ACTH, Semax has no hormonal (corticotropic) activity.

Semax was developed at the Institute of Molecular Genetics of the Russian Academy of Sciences. In preclinical research it has been studied mainly in neuroprotection models and in models of BDNF (brain-derived neurotrophic factor) expression. It is registered as a medicine in Russia but is not authorised in the EU.

• Sequence: Met-Glu-His-Phe-Pro-Gly-Pro
• Parent peptide: ACTH(4-10) fragment (ACTH 4-7 + Pro-Gly-Pro)
• Hormonal (corticotropic) activity: none
• Research focus: neuroprotection and BDNF-expression models

What is Selank?

The Selank peptide is also a synthetic heptapeptide, with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. It is an analogue of tuftsin, an immunomodulatory tetrapeptide (Thr-Lys-Pro-Arg), extended with the same Pro-Gly-Pro tail.

Selank was developed at the same institute as Semax. It has been studied in anxiety and stress models and in models of immunomodulation. Like Semax, it is registered in Russia but not authorised in the EU.

• Sequence: Thr-Lys-Pro-Arg-Pro-Gly-Pro
• Parent peptide: tuftsin (Thr-Lys-Pro-Arg) + Pro-Gly-Pro
• Research focus: anxiety/stress and immunomodulation models

Key differences between Semax and Selank

The most important difference between Semax and Selank is their origin. Semax builds on a fragment of a hormone (ACTH); Selank builds on an immunomodulatory peptide (tuftsin). As a result, the first four amino acids are completely different, and the two peptides are studied in different research models.

• Parent peptide – Semax: ACTH(4-10) fragment; Selank: tuftsin
• Sequence – Semax: Met-Glu-His-Phe-Pro-Gly-Pro; Selank: Thr-Lys-Pro-Arg-Pro-Gly-Pro
• Research focus – Semax: neuroprotection and BDNF expression; Selank: anxiety/stress and immunomodulation

What Semax and Selank have in common

Both are heptapeptides of seven amino acids, and both come from the Institute of Molecular Genetics of the Russian Academy of Sciences. Their most striking shared feature is the C-terminal Pro-Gly-Pro extension: it improves resistance to enzymatic breakdown and so makes the peptides more stable than their parent sequences.

That shared design is one reason the two often appear together in nootropic peptides research. Both are research compounds that are not authorised in the EU; the Semax and Selank supplied by Virexa Labs are intended exclusively for laboratory research – not for human or veterinary use.

• Both heptapeptides (7 amino acids)
• Same C-terminal Pro-Gly-Pro extension for stability
• Developed at the same institute
• Registered in Russia, not authorised in the EU

Storage and reconstitution

Store lyophilised vials of Semax and Selank at −20 °C, dry and protected from light; 2–8 °C is fine for short periods. Reconstitute with bacteriostatic water: add it slowly along the wall of the vial and swirl gently – don't shake. Keep the solution at 2–8 °C, use it within about four weeks and avoid repeated freezing and thawing.

Our storage guide describes the full procedure step by step.

Quality at Virexa Labs

Looking to buy Semax and Selank for research? At Virexa Labs, every batch is tested by HPLC for ≥99% purity and by mass spectrometry for identity. The Certificate of Analysis (COA) is available on the product page.

Delivery takes 1–2 working days to Belgium, the Netherlands and Germany, and 2–5 working days to Italy and Türkiye.

Related research peptides

• Semax
• Selank
• VIP
• Bacteriostatic Water 10mL

Frequently asked questions

What is the difference between Semax and Selank?

Semax is an analogue of the ACTH(4-10) fragment (Met-Glu-His-Phe-Pro-Gly-Pro), studied in neuroprotection and BDNF-expression models. Selank is an analogue of tuftsin (Thr-Lys-Pro-Arg-Pro-Gly-Pro), studied in anxiety/stress and immunomodulation models.

Does Semax have hormonal activity?

No. Although Semax is derived from a fragment of ACTH, it has no hormonal (corticotropic) activity.

Why do both peptides end in Pro-Gly-Pro?

The Pro-Gly-Pro extension improves resistance to enzymatic breakdown, making these short peptides more stable than their parent sequences.

Are Semax and Selank approved medicines in the EU?

No. Both are registered as medicines in Russia but are not authorised in the EU. Virexa Labs sells them strictly for laboratory research; they are not intended for human or veterinary use.

How fast is delivery?

1–2 working days in Belgium, the Netherlands and Germany; 2–5 working days to Italy and Türkiye.