Comparison / Selank vs Semax
Selank vs Semax: Comparing the Research
Two Russian research peptides, often mentioned together and constantly confused. They are different molecules with different mechanisms — here's the honest comparison.
The short version
Here's Selank vs Semax in one breath: they're two different peptides, from the same Russian research tradition, that people lump together because they're often studied and sold side by side — but they are not the same thing and shouldn't be treated as interchangeable.
Selank is the calming one. It's built from tuftsin (an immune-and-calm peptide), works largely through the GABA and natural-opioid systems, and is studied as a non-sedating anxiolytic [1][2]. Its sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro.
Semax is the focus-and-resilience one. It's a different molecule entirely — derived from a fragment of the hormone ACTH — and is studied as a nootropic and neuroprotective peptide. Different parent, different sequence, different main mechanism. This page compares them honestly using what the Selank research actually establishes, and is careful not to put words in Semax's mouth.
What is the difference between Selank and Semax?
The cleanest way to separate them is origin and job. Selank is a synthetic analog of tuftsin, the endogenous immunomodulatory tetrapeptide (Thr-Lys-Pro-Arg) cleaved from the heavy chain of immunoglobulin G, extended with Pro-Gly-Pro for stability — so its full sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro (also called TP-7) [6]. Its studied role is anxiolytic and immunomodulatory.
Semax is a synthetic analog of a fragment of adrenocorticotropic hormone (ACTH) — a completely different parent molecule and sequence — studied primarily as a nootropic and neuroprotective agent. So while both are short Russian-developed peptides used intranasally, they start from different biology and are aimed at different effects. This site documents the Selank side in detail; it does not assert Semax findings it hasn't reviewed.
How Selank works (the side we can cite)
On the Selank side, the mechanism is well-characterized in the research summarized here. Selank acts as a positive allosteric modulator of GABA-receptor binding — making the brain's main calming receptor easier to activate, in a subtype-selective, dose-dependent way distinct from benzodiazepines [1]. It also inhibits enkephalin-degrading enzymes in human plasma (IC50 ~15 µM), protecting the body's own opioid-like calming signals [2], and raises BDNF in the rat hippocampus, linking it to neuroplasticity [3].
That profile is why Selank's reputation is "calm but clear": it supports the brain's own calm-and-adapt systems rather than sedating. Semax's nootropic reputation comes from a different mechanistic story rooted in its ACTH-fragment origin — which is outside the citable scope of this Selank-focused digest.
Should Semax and Selank be taken together in research?
In community practice people often pair them — Selank for calm, Semax for focus — but the peer-reviewed Selank corpus summarized here does not include a controlled Selank-plus-Semax combination study, so there is no citable efficacy or safety finding for that specific pairing in this digest. What the research does show is that Selank interacts with other GABAergic agents: combining Selank with diazepam produced the largest anxiety reduction in a rodent stress model [7].
That tells you Selank can have additive effects with things acting on overlapping systems — which is a reason for caution, not a protocol. This site gives no dosing and no recommendation to combine compounds; it reports that the specific Selank-plus-Semax combination is not established in the literature reviewed here.
What they share — and the shared caveat
Selank and Semax share a lineage and a limitation. Both came out of Russian research programs, both are typically used intranasally, and both have evidence bases concentrated in Russian-language literature with limited independent Western replication [6]. Neither is FDA-approved, and outside Russia both are sold as research chemicals.
So the honest comparison is symmetrical at the bottom: two distinct peptides with genuinely interesting but single-region, mostly-preclinical evidence. The difference is in what they target — Selank for non-sedating calm via GABA and enkephalinase pathways [1][2], Semax for cognition via a different route. For the full Selank picture, continue to Selank research, and for what people report, Selank effects.