Semax vs Selank

Two regulatory peptides from the same research programme, acting on different neurotransmitter systems. Why they are studied together and should not be conflated.

Same programme, different parents

Semax and Selank came out of the same Russian institute and are frequently mentioned in the same breath, which obscures that they derive from unrelated parent molecules and act on unrelated systems.

Semax is a heptapeptide built on the ACTH(4-10) fragment with a Pro-Gly-Pro tail added for stability. The corticotropic activity of the parent hormone is absent; what remains is studied for neurotrophic and noradrenergic effects.

Selank is a heptapeptide built on tuftsin, an immunomodulatory tetrapeptide derived from immunoglobulin G, with the same stabilising tail. Its research sits in GABAergic and anxiolytic signalling, and it retains a documented immunomodulatory strand that Semax does not have.

Where they differ

Parent molecule. ACTH(4-10) against tuftsin — a pituitary hormone fragment against an immunoglobulin fragment.
Primary system. Noradrenergic and dopaminergic modulation with BDNF expression for Semax; GABAergic and serotonergic modulation for Selank.
Research framing. Semax is studied for attention, memory consolidation and neuroprotection in ischaemia models. Selank is studied for anxiolytic endpoints without the sedation profile of classical GABAergic agents.
Immune activity. Present for Selank, following from tuftsin. Not a feature of the Semax literature.
BDNF. One of the most cited observations for Semax; not central to Selank.
Presentation. Both are supplied as vials and as metered intranasal bottles — Semax and Selank — because the intranasal route is how most of the primary work was conducted.

Which suits which question

Work on cognitive endpoints, neurotrophic signalling or ischaemic neuroprotection points to Semax. Work on anxiety-like behaviour, GABAergic tone or the immune-behavioural interface points to Selank.

They are often studied together because the systems are complementary rather than overlapping, and a design using both can separate an arousal or attention effect from an anxiolytic one. What does not work is treating them as variants of a single nootropic and expecting results from one to transfer.

Both should be read with the same caveat as the rest of the bioregulator literature: much of the primary work is in Russian-language journals, and methodological detail is not always recoverable from the translations in circulation. Published work is indexed on PubMed.

How both are supplied

Both are supplied lyophilised in sealed vials and as metered intranasal preparations. Each batch is specified at 99% purity or better by HPLC with identity confirmed by mass spectrometry and released against a batch-matched Certificate of Analysis, by the process on the lab testing page. Both sit in the cognitive and sleep group alongside DSIP and Dihexa.

Research use only

Both compounds are laboratory reference materials. Neither is a medicine, a supplement, or for human or veterinary use, and no dosing guidance or administration protocol is provided for either. The full terms are in the research use policy. Every guide is indexed in the research library.