Three Peptides, Side by Side

The short version

This page lines up Semax, Selank and DSIP on the dimensions that matter when reading research peptides: what kind of molecule each one is, where it has been studied most, how strong the evidence is, how it was given in studies, its regulatory status, and its single biggest caution. The headline is blunt. All three are studied in the brain-chemistry space, but they are at very different stages and working on different problems. Selank has the most human data — a small Russian clinical RCT in generalized anxiety disorder. Semax has the most rodent mechanistic data, a real prescription drug registration in Russia, and no Western RCT. DSIP has been studied longest, still has no identified receptor or gene, and a large share of users report no effect. None is an approved medicine in the United States or European Union, and none is presented here with a human dose.

The comparison matrix

Peptide class

Semax and Selank are both synthetic heptapeptides built by modifying endogenous molecules and adding a Pro-Gly-Pro enzymatic-stability tail — a structural family resemblance that explains why they share some mechanisms (both inhibit enkephalin-degrading enzymes) despite having different primary targets. DSIP is a naturally occurring nonapeptide, nine amino acids rather than seven, endogenously produced and found in cerebrospinal fluid and plasma — yet paradoxically the least mechanistically understood of the three.

Most-studied in

The three occupy different cognitive territories. Semax's home ground is neuroprotection and neurotrophin signaling — BDNF, NGF, and the immunomodulatory cascade in ischemia models — with cognition as a downstream target ^[3][4][2]. Selank's home ground is anxiety and GABAergic modulation, studied as a non-sedating alternative to benzodiazepines ^[6][11]. DSIP was named for and has been most studied in the context of sleep and delta-wave EEG activity, with secondary work in stress-hormone modulation and longevity ^[14][16].

Evidence base (model)

This is where the three genuinely separate. Selank has the most direct human clinical evidence: a Russian clinical study in GAD patients with an active comparator and a real anxiolytic result ^[11]. Semax has the deepest rodent record and is registered as a prescription drug in Russia — but no Western RCT exists ^[3][4]. DSIP has the longest research history (since 1977) and the weakest evidentiary outcome: its sleep effects are described by a mainstream peer-reviewed review as extremely poorly documented, no receptor has been found, and the human trials are small and old ^[14][17]. The human ACTH-modulation finding was not reliably replicated ^[16].

Administration studied

Intranasal delivery is the primary studied and community-used route for both Semax and Selank, which is how they are supplied in Russian formulations and how they are used in the nootropic community. Intravenous delivery was used in the human DSIP sleep and ACTH studies ^[16][17], and animal studies use IP or ICV routes across all three compounds. Oral bioavailability is not established for any of them; peptides are generally degraded in the gut before reaching the bloodstream.

Regulatory / WADA status

None of the three is approved for human use by the FDA or EMA. Semax and Selank are registered prescription drugs in Russia only; outside Russia they are sold strictly as research chemicals. DSIP has no approved drug status anywhere — its INN Emideltide exists in the registry but no Emideltide product has ever been approved or marketed. Semax does not appear by name on the WADA Prohibited List but may fall under the catch-all S0 non-approved substances category. Selank and DSIP are not specifically named on the WADA list, but athletes under anti-doping rules should treat any non-approved substance with appropriate caution.

Key caution

Each peptide carries a defining issue that this desk will not minimize. For Semax it is that the evidence base is geographically concentrated in a small set of Russian institutions with no Western replication, and that its neurotrophin and immune gene-expression effects — while genuine — are large-scale biological interventions whose long-term consequences in healthy humans are unstudied ^[2][3]. For Selank it is the interaction unknowns: it touches GABAergic, opioid, monoaminergic, and immune signaling, and combining it with medications acting on those systems has essentially not been studied in Western populations ^[6][10][12]. For DSIP it is the fundamental mechanistic uncertainty — no receptor, no gene, a 2006 authoritative review calling its sleep evidence extremely poorly documented, and a large share of users who report nothing ^[14]. Reading the three together, the lesson is the same as it tends to be in this field: interesting biology, narrow and geographically concentrated evidence, and a gap between community enthusiasm and clinical proof.